U-boat Archive - Type VII C Manual

U-Boat Type VIIC	U-boat Information	Page III

	Amendments

Note the section, page and paragraph No., to which changes or additions are registered:			Certified to be Correct

Page	Contents	Paragraph No.		Place	Date	Signed

Page IV	U-boat Information	U-Boat Type VIIC

	Amendments

Note the section, page and paragraph No., to which changes or additions are registered:			Certified to be Correct

Page	Contents	Paragraph No.		Place	Date	Signed

U-Boat Type VIIC	U-boat Information	Page V

	Table of Contents

Contents of U-boat Information

=====================

			Page
Title Page			I
Excerpt from the regulations for the establishment, examination and conduct of General Navy Regulations and Damage Control Procedures			II
Amendments to U-boat Information			III
Table of Contents Ship Information			V
Table of Contents Machinery Installations			X
Introduction: Development of the Type VII C U-boat			XIII
A. Ship Information
I. General.
1.	Shipyard information		1
2.	Overview of ship construction		2
	a)	Dimensions	2
	b)	Measured displacement	3
	c)	Volume and distance from center of mass	3
	d)	Test and operating pressures	7
	e)	Materials	8
	f)	Weights	9
	g)	Stability	9
3.	Weapons overview		11
	a)	Torpedoes and mines	11
	b)	Artillery	12
	c)	Small arms	12
4.	Safety and rescue equipment overview		12
	a)	Structural safety installations	12
	b)	Safety equipment	13
	c)	Rescue equipment	13
5.	Test data		14
	a)	Speed [surfaced] and [submerged]	14
	b)	Diving time	14
	c)	Diving depth	14
	d)	Depth differences for bow and stern	15

Page VI	U-boat Information	U-Boat Type VIIC

	Table of Contents

			Page
6.	Practical values		15
	a)	Speeds for various operating conditions	15
	b)	Behavior of the boat under different rudder angle and wind conditions	17
	c)	Turning radius	17
	d)	Behavior in a seaway	20
	e)	Diving characteristics	20
	f)	Depth control	21
	g)	Vibrations	23
	h)	Sound levels	24
II. Boat and Pressure Hull - including openings.
1.	General construction of the boat		26
2.	Construction of the pressure hull		26
3.	Partitioning of the pressure hull		27
4.	Conning tower structure		28
5.	Openings in the pressure hull		29
6.	Construction of the outer shell		34
7.	Partitioning of the outer shell		36
III. Diving Installations.
1.	Tanks and fuel oil tanks		37
	a)	Main ballast tanks	37
	b)	Main ballast and reserve fuel oil tanks	37
	c)	Bow and stern buoyancy tanks	38
	d)	Regulating tanks	38
	e)	Regulating and reserve fuel oil tanks	39
	f)	Trim tanks	39
	g)	Negative buoyancy tanks	39
	h)	Torpedo compensating tanks	40
2.	Blowing and exhaust gas blowing installation		40
	a)	Compressed air blowing	40
	b)	Exhaust gas blowing	40
3.	Venting and vent valves		40
4.	Compressed air systems		41
	a)	Electric air compressor	41
	b)	Diesel air compressor	42
	c)	High pressure compressed air flasks	43
	d)	Compressed air equipment	43
5.	Pumps		46
6.	Dive planes		47

U-Boat Type VIIC	U-boat Information	Page VII

	Table of Contents

			Page
IV. Armament.
1.	Torpedoes and mines		48
	a)	Torpedo tubes	48
	b)	Installation for mine ejection	49
	c)	Stowage	49
	d)	Torpedo loading equipment	51
	e)	Torpedo fire control system	51
	f)	Weight compensation during torpedo firing and mine ejecting	53
2.	Gunnery		56
	a)	Weapons	56
	b)	Ammunition	56
3.	Mine and demolition equipment		56
4.	Small arms		57
V. Communications
1.	Visual and acoustic equipment		58
	a)	Visual equipment	58
	b)	Acoustic equipment	58
2.	Electronic communication equipment		59
	a)	Radio installation	59
	b)	Broadcast and announcement system	61
	c)	Ultra short wave portable transmitter and receiver	61
	d)	Aerial installations	62
	e)	Radio converter installation	63
	f)	UT Installation (sound)	63
	g)	G.H.G. installation	63
	h)	K.D.B. equipment	64
3.	Power supply for electronic communications equipment		64
4.	Aerials		66
VI. Steering System and Anchor Installation.
1.	Steering system		67
	a)	General	67
	b)	Main rudder installation	68
	c)	Dive planes installation	69
2.	Anchor installation		69
VII. Equipment and Installations for Ship Control.
1.	Ship Control		71
2.	Periscopes		71

Page VIII	U-boat Information	U-Boat Type VIIC

	Table of Contents

			Page
	a)	Attack periscope	71
	b)	Air search periscope	72
	c)	Periscope drive	72
3.	Compass installation		73
	a)	Gyro compass installation	73
	b)	Projector compass installation	74
4.	Signal equipment		74
5.	Depth sounding equipment		75
	a)	Echolot	75
	b)	Elektrolot	76
	c)	Hand lead	76
6.	Log installation		76
7.	Alarm installation		77
8.	Ordering and reporting installations		78
VIII. Safety and Rescue Installations.
1.	Installations for submerged and surfaced boat		79
	a)	Emergency lighting	79
	b)	Hand lamps	80
	c)	Fire extinguishers	80
	d)	Flooding installation	80
	e)	Drainage installation	80
	f)	UT and G.H.G. installation	80
	g)	Emergency steering gear	81
	h)	Diving suit	81
	i)	Emergency escape gear	81
	k)	Life rafts	81
	l)	Damage control materials	81
2.	Installations for surfaced boat		81
	a)	Battery ventilation	81
	b)	Emergency vent valves	81
	c)	Coaming	82
	d)	Life buoy, night signal buoy and dinghy	83
	e)	Life jackets	83
	f)	Railing and tethers	83
	g)	Recognition marks for aircraft	84
3.	Installations for submerged boat		84
	a)	Compartmentation	84
	b)	Air purification system	84

U-Boat Type VIIC	U-boat Information	Page IX

	Table of Contents

			Page
	c)	Compressed air and emergency blowing manifold	86
	d)	Emergency air supply system	86
	e)	Life rafts	87
	f)	Air trap	87
	g)	Emergency escape gear	87
	h)	Net deflector	88
	i)	Net cutter	88
	k)	Compartment ready indicating system	88
	l)	Hull closure indicating system	88
	m)	Vent valve indicating system	88
IX. Damage Control.
1.	General		89
	a)	Damage control parties	89
	b)	Balancing the boat	90
	c)	Reserve buoyancy	91
2.	Weights and trim adjustment with water flooding		91
	a)	Leakage into external tanks with the boat surfaced	92
	b)	Leakage into pressure hull with the boat surfaced	93
	c)	Leakage into external tanks and into pressure hull with the boat surfaced	97
	d)	Leakage with the boat submerged and with the boat lying on the bottom	102
3.	Leakage counter measures		103
	a)	Blowing	103
	b)	Sealing the compartments	104
	c)	Sealing leaks	104
	d)	Pumping	105
	e)	Weight relief	106
4.	Escape from a sunken boat		106
	a)	Escape procedures	106
	b)	Influence of chlorine gas, nitrogen and oxygen	107
	c)	The practical use of the emergency escape gear	111
	d)	Flooding options and flooding time	112
5.	Gas hazard		117
6.	Fire hazard		117
7.	Fire extinguishing equipment and flooding installation		117
8.	Drainage and compressed air systems		117

Page X	U-boat Information	U-Boat Type VIIC

	Table of Contents

			Page
B. Machinery Installation.
I. Propulsion Plant			118
1.	M.A.N. diesel engine installation		118
	a)	M.A.N. general and performance figures	118
	b)	Construction of the M.A.N. propulsion plant	119
	c)	Auxiliary machinery associated with M.A.N. engines	120
1.	G.W. diesel engine installation		123
	a)	G.W. general and performance figures	124
	b)	Construction of the G.W. propulsion plant	124
	c)	Auxiliary machinery associated with G.W. engines	125
1-1	Comparison between M.A.N. - G.W. engines		129
2.	Batteries		131
	a)	Technical and performance data	131
	b)	Construction and maintenance	131
	c)	Capacity, discharging, final voltage	133
	d)	Charging	133
3.	The main switchboards and battery connections		134
4.	E motor installation		134
	a)	Design and performance data	134
	b)	Motor construction and connections	135
5.	Shaft lines		136
	a)	Propellers	136
	b)	Drive shafts, bearings and shaft brakes	136
	c)	Main thrust bearing	137
	d)	Clutches	138
6.	Interaction of the engines and motors		140
	a)	General	140
	b)	Diesel engine only drive	140
	c)	E motors only	140
	d)	Support and buffer mode	140
	e)	Diesel-electric drive	141
	f)	Charging operation	141
II. Auxiliary Machinery for Propulsion.			142
1.	Ship's auxiliary machinery		142
	a)	Main rudder and dive planes	142
	b)	Anchor and warping capstan installation	143
	c)	Air compressor	144

U-Boat Type VIIC	U-boat Information	Page XI

	Table of Contents

			Page
	d)	Auxiliary drain and trim pump	145
	e)	Main drain pump	145
	f)	Intake and exhaust air fan	145
	g)	Periscope drive	146
	h)	Refrigeration plant	148
	i)	Distilling unit	149
	k)	Hand pumps etc	150
	l)	W.C. installation	151
	m)	Gyro compass installation	151
2.	Auxiliary machinery for the diesel engine installation		151
	a)	Auxiliary lubricating oil pump	151
	b)	Auxiliary cooling water pump	152
3.	Auxiliary machinery for the E installation		153
	a)	E motor fan blower	153
	b)	Cooling pump	153
III. Draining and Flooding.
1.	Main drainage installation		155
2.	Auxiliary drainage installation		155
3.	Hand drainage installation		156
4.	Artificial flooding installation		156
5.	Natural flooding installation		156
IV. Sea, Wash, and Fresh Water Installations.
1.	Sea water installation		158
2.	Wash water installation		158
3.	Fresh water installation		158
V. Ventilating Systems.			160
VI. Heating Installations.			161
VII. Lubricating Oil Installations.			163
VIII. Fuel oil Installations.			165
IX. E Installations.
1.	E motors		167
2.	Batteries		167
3.	Main switchboards		168
	a)	Main switchboards with lever switches	168
	b)	Main switchboards with rotary switches	170

Page XII	U-boat Information	U-Boat Type VIIC

	Table of Contents

			Page
4.	Auxiliary switchboards and power distribution		173
5.	Electric equipment		174
	a)	E drive motors and their current draw	174
	b)	Rotary converters and associated equipment	175
	c)	Ordering and reporting installations	179
		General information and power supply	179
		Engine order telegraph system	180
		Shaft revolution indicator system	180
		Rudder order telegraph and rudder angle indicator system	181
		Dive planes angle indicator system	182
		Alarm bell and flashing light system	182
		Compartment ready indicating system	183
		Hull closure indicating system	183
		Vent valve indicating system	183
		Torpedo orders indicator system	184
	d)	Signal equipment	184
		General information and power supply	184
		Running lights	185
		Searchlight equipment	185
	e)	Power load for ships purposes	185
		Boat lighting	185
		Hot plates	186
		Boats heating	186
C. Annex: Drawings

- . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . - . -

U-Boat Type VIIC	U-boat Information	Page XIII

	Introduction

Development of the Type VII C U-boat

===========================

The first medium size U-boats of the German Navy were the Type VII U-boats (displacement 500 tons) of U-Flotilla "Saltzwedel" (1936). Their main distinguishing characteristic was the aft torpedo tube on the upper deck.

This boat was developed into the Type VII B (displacement 517 tons). These boats which together formed U-Flotilla "Wegener" (1938) had the aft torpedo tube inside the pressure hull and also some diving and operational improvements and greater propulsion plant performance as a result of installed superchargers.

The Type VII B U-boats came into service during peace time, but after war broke-out in 1939, they proved their outstanding utility as a prefect front-line submarine. They fulfilled all requirements completely.

Nevertheless, even before war time there were attempts to make some other improvements, which eventually led to the Type VII C U-boat:

1. New electronic and communication equipment required more space to install. This space was obtained by lengthening the control room by the distance of one half frame forward of, and one half frame aft of the search periscope. The type VII C boat was lengthened by one frame.

2. Related to above changes, the quite constricted type VII B conning tower dimensions were increased in width by 60 mm and length by 300 mm.

3. Diving characteristics, especially in heavy seas, were improved by adding pressure-proof negative tanks forward of the port and starboard regulating tanks.

4. Surface range was improved by increasing the fuel oil capacity of fuel oil tank 1 (internal). This was achieved by moving the aft bulkhead of main ballast tank 3 one frame forward. The volume of fuel oil tank 1(internal) was increased from 32.5 m³ in the type VII B to 37.9 m³ in the type VII C.

Page XIV	U-boat Information	U-Boat Type VIIC

	Introduction

5. One of the two electrically driven compressors (Krupp design) was replaced by a diesel engine driven compressor (Junkers design) in order to reduce electric power consumption.

6. To achieve required reliability the lubricating oil purifying installation was provided.

U-Boat Type VIIC	A. Ship Information	Page 1

U-boat Information	I. General	1

A. Ship Information.

I. General.

1. Shipyard information.

Shipyards.

Primary Yard:

Friedrich Krupp Germaniawerft A.-G., Kiel-Gaarden

North Sea Area

Follow-on Yards:

Nordseewerke Emden

Kriegsmarinewerft Wilhelmshaven

Vegesacker Werft

Blohm and Voß Hamburg

Howaldtwerke Hamburg

H.C. Stülken Hamburg

Baltic Area

Flensburger Shipbuilding Company

Deutsche Werke Kiel

Lübecker Flenderwerke

Danzinger Werft

Schichauwerft Danzig

Construction data for U-____


Construction yard	Keel laying	Launching	1. Commissioning	Decommissioning	2. Commissioning

U-boat Commands must enter valid data on page 1 under "Construction data for U-____" and on page 3 under "Measured displacement" for their boats in their U-boat Manuals. [Pasted note]

Page 2	A. Ship Information	U-Boat Type VIIC

2	I. General	U-boat Information

2. Overview (ship construction).
	a)	Dimensions.
		Length:
		Length over all		m
		Length at the waterline		m
		Length of the pressure hull with end caps		m
		Length of pressure hull without end caps		m

		Width:
		Maximum width		mm
		Maximum width at the waterline		mm
		Maximum width of the pressure hull		mm
		Diameter of the forward end of the pressure hull		mm
		Diameter of the aft end of the pressure hull		mm

		Draft:
		Draft aft		m
		Draft amidships		m
		Draft forward		m
		Note: Length, width, and draft are classified.

		Height:
		Upper deck above keel	6000	mm
		Top of conning tower above keel	9397	mm
		Top of attack periscope above conning tower fairing	5266	mm
		Top of search periscope above conning tower fairing	2602	mm
		Extended attack periscope above keel	14663	mm
		Extended air search periscope above keel	11999	mm

		Conning tower and keel:
		Height of conning tower above pressure hull	2630	mm
		Length of the conning tower	2950	mm
		Width of the conning tower	1760	mm
		Height of the keel	550	mm
		Width of the keel	1100	mm
		Length of straight keel	32355	mm

U-Boat Type VIIC	A. Ship Information	Page 3

U-boat Information	I. General	3

b) Measured displacement.

U-boat Commands must enter valid data on page 1 under "Construction data for U-____" and on page 3 under "Measured displacement" for their boats in their U-boat Manuals. [Pasted note]

Surfaced displacement

m³

Submerged displacement

m³

Official displacement

m³

c) Volume and distance from center of mass.

Interior Rooms:


Room	Volume m³	Distance meters

Aft torpedo room and E motor room	62	-18.75
Diesel engine room	88	-10.95
Petty officer quarters without/with battery compartment 1	33/47	-4.55
Control room	45	+2.3
Officers, chief petty officers, radio, listening, switch rooms without/with battery compartment 2	63/77	+9.65
Forward torpedo room	72	+18.85
Conning tower without/with periscope shaft	10/14	+2.3
Total volume:	405

Exterior Spaces:


Room	Volume m³	Distance meters

Stern buoyancy tank	4.28	-31.15
Bow buoyancy tank	8.0	+29.05

Ballast tanks, Fuel oil tanks, Tanks and Reservoirs:

Measured volume (liters)


Boat	Regulating tanks		Trim tanks		Regulating and reserve fuel oil tanks		Torpedo compensating tanks
No.	Stb.	Port	Aft	Forward	Stb.	Port	1	2	3

U 93	(7850)	(7850)	(3550)	(3600)	(4700)	(4700)	(2350)	(5750)	(5750)
(Type - boat)
	7800	7660	3640	3680	4640	4580	2450	5680	5790
U . . .
	Figures in parentheses are calculated

Page 4	A. Ship Information	U-Boat Type VIIC

4	I. General	U-boat Information

Tanks: (Calculated values)


Tank	Capacity m³ working volume	Test Pressure meters H₂O	Distance meters

Main ballast tank 1	30.700	6	-26.00
Main ballast tank 3 (with vent duct 1 m³)	47.750	30	+2.10
Main ballast tank 5	25.150	6	+26.47
Regulating tank 2 stb. (total 7.850 m³)	7.600	140	-0.10
Regulating tank 2 port (total 7.850 m³)	7.600	140	-0.10
Aft trim tank	3.550	30	-23.05
Forward trim tank	3.600	30	+18.55
Torpedo compensating tank 1	2.350	30	-21.15
Torpedo compensating tank 2	5.750	30	+15.25
Torpedo compensating tank 3	5.750	30	+15.25
Fresh water tank 1 (Galley)	2.625	3	-7.05
Fresh water tank 2 (Control room)	0.465	3	+1.25
Fresh water tank 3 (Officers room)	0.785	3	+9.90
Wash water tank (Listening room)	0.485	3	+7.75
Waste water tank 1	0.760	1	-6.05
Waste water tank 2	0.485	1	+7.75
Negative buoyancy tank stb. (total 2.15 m³)	2.070	30	+2.45
Negative buoyancy tank port (total 2.15 m³)	2.070	30	+2.45

Fuel Oil Tanks: (Calculated values)


Bunker	Volume m³	Test Pressure meters H₂O	Distance meters

Main ballast and reserve fuel oil tank 2 starboard	11.300	6	-7.95
Main ballast and reserve fuel oil tank 2 port	11.300	6	-7.95
Main ballast and reserve fuel oil tank 4 starboard.	13.300	6	+7.05
Main ballast and reserve fuel oil tank 4 port	13.300	6	+7.05
Regulating and reserve fuel oil tank 1 starboard	4.700	140	-3.25
Regulating and reserve fuel oil tank port	4.700	140	-3.25
Fuel oil tank 1 (internal)	37.900	8	-3.25
Fuel oil tank 2 (internal)	32.800	8	+8.30
Fuel oil collecting tank	0.425	6	-9.55

U-Boat Type VIIC	A. Ship Information	Page 5

U-boat Information	I. General	5

Tanks:


Tank	Capacity m³ working volume	Test Pressure meters H₂O	Distance meters

Lubricating oil supply tank 1	3.270	6	-11.45
Lubricating oil supply tank 2	3.230	6	-11.45
Lubricating oil collecting tank starboard	0.800	6	-11.65
Lubricating oil collecting tank port	0.800	6	-10.45
Dirty lubricating oil tank	0.790	6	-12.85

Storage and Weight:


Storage	Capacity m³ working volume	Test Pressure meters H₂O	Distance meters

Fuel oil gravity feed tank	0.730		-11.50
Lubrication oil daily service tank	0.026		-7.55
Water distillate tanks 1-3			-18.50
149 liters + 199 liters + 153 liters	0.501		-16.70
			-16.25
Storage for flare shells	0.033		+5.45
Storage for demolition charges	0.500		+9.90
Ammunition magazine	7.350		+6.85
Provisions storage aft	2.000		-6.65
Provisions storage forward	1.600		+13.15
Wash water daily supply tank	0.030		-5.90
Brine tank	0.030		+3.05

Torpedo stowage:


Tubes	Volume liters	Remarks	Distance meters

Torpedo tubes I - V		Piston 70 kg	fwd: +25.25
with piston inserted	1680		aft: -26,15
without piston	1740		fwd: +25.10
			aft: -26.00
Upper deck container forward, aft	2500		fwd: +19.18
with/without G 7 A		0.5 at	aft: -20.23
		test pressure	fwd: +18.75
			aft: -19.80

Page 6	A. Ship Information	U-Boat Type VIIC

6	I. General	U-boat Information

Torpedo stowage:


Tubes	Volume liters	Remarks	Distance meters

Torpedo in the tube	-	G 7 E =	fwd: +25.63
G 7 E / G 7 A		G 7 E =	aft: -26.53
		G 7 A =	fwd: +25.56
		G 7 A =	aft: -26.46

Reserve stowage forward, aft	-	G 7 E =	fwd: +17.75
		G 7 A =	fwd: +17.66
		G 7 A =	aft: -18.30

Residual Water in tanks and bunkers:


Designation	Volume m³	Remarks

Main ballast tank 1	2.550 )
Main ballast tank 3	0.800 )	100 mm above
Main ballast tank 5	1.980 )	upper edge
Main ballast and reserve fuel oil tank 2 port/stb.	0.950 )	of flood opening
Main ballast and reserve fuel oil tank 4 port/stb.	1.050 )
Regulating and reserve fuel oil tank 1 port/stb.	~ 0
Regulating tank 2 port/stb.	0.500	Not pumpable
Negative buoyancy tank port/stb.	0.160	Not blowable

Total capacity:

Ballast tanks	103.600 m³
Ballast tanks and ballast and reserve fuel oil tanks	152.800 m³
Fuel oil tank 1 and 2 (internal)	70.700 m³
Fuel oil tanks (internal), main ballast and reserve fuel oil tanks, and regulating and reserve fuel oil tanks	129.700 m³
Lubricating oil supply tanks 1 and 2	6.500 m³
Lubricating oil collecting tanks port and stb.	1.600 m³
Fresh water tanks	3.875 m³
High pressure air flasks at 205 kg/cm²	3900 liters
Oxygen flasks at 150 kg/cm²	500 liters

U-Boat Type VIIC	A. Ship Information	Page 7

U-boat Information	I. General	7

d)	Test and operating pressures.
	Spaces, vents/valves.
	Pressure test in pressure dock under external pressure	10.5 at
	Watertight bow and watertight stern under air pressure	0.02 at
	Pressure hull and conning tower including periscope shafts with internal pressure equivalent to water pressure at the bottom of the pressure hull	30 meters Pressure head
	Pressure-proof curved watertight bulkheads from the cupped side with internal pressure equivalent to water pressure at the top of the pressure hull	30 meters Pressure head
	Watertight bulkheads with internal pressure equivalent to water pressure at the top of the pressure hull	1 meter Pressure head
	Testing the bulkhead tightness of the ammunition magazine for gas tightness	1 meter Pressure head
	Hull plating tested to	15 at
	Flood valves of main ballast and reserve fuel oil tanks and main ballast tank 3 at the valve	1 meter Pressure head
	Vent valves with pressure equivalent to water pressure at the top of main ballast tanks or main ballast and reserve fuel oil tanks to	6 meters Pressure head
	Emergency vent valves for main ballast tank 3	1 meter Pressure head
	Emergency vent valves for main ballast and reserve fuel oil tanks 2 and 4 port and stb.	6 meters Pressure head
	Deck of the battery compartment by filling the battery compartment with air under pressure	100 mm Pressure head

Tanks, Fuel Oil Tanks, Bunkers, Gravity Tanks see paragraph I 2 c

High pressure air, oxygen and pressure oil flasks.
	High pressure air flasks:	Operating pressure	205 kg/cm²
		Test pressure	280 kg/cm²
	Starting air flasks MAN:	Operating pressure	75 kg/cm²
		Test pressure	120kg/cm²
	Starting air flasks GW:	Operating pressure	30 kg/cm²
		Test pressure	50 kg/cm²
	Oxygen flasks:	Operating pressure	150 kg/cm²
		Test pressure	225 kg/cm²
	Hydraulic oil flasks	Operating pressure	70 kg/cm²
		Test pressure	120 kg/cm²

Page 8	A. Ship Information	U-Boat Type VIIC

8	I. General	U-boat Information

Auxiliary Machinery.
Air compressor:	Operating pressure	LP stage	1.2-1.4 kg/cm²
		MP stage 1	7-9 kg/cm²
		MP stage 2	19.5 - 45 kg/cm²
		HP stage	205 kg/cm²
	Test pressure = 1.5 x operating pressure
	Test pressure radiator casing 15 kg/cm²
Capstan motor:	Operating pressure		3.5 kg/cm²
Hydraulic oil pump for periscope drive: Operating pressure			70 kg/cm²
Compartment ventilating fan:	Operating pressure	424 mm H₂O
	Test pressure of fan enclosure		0.25 kg/cm²

Safety valves:
	HP air manifold		220 kg/cm²
	Ballast tank blowing manifold		30 kg/cm²
	Low pressure air manifold		18 kg/cm²
	Trim air pressure distributor		2.5 kg/cm²
	Regulating tank pressure discharge distributor		12 kg/cm²
	Anchor capstan		6 kg/cm²

e)	Materials.
	Pressure hull	St 52 K M
	Conning tower casing	Wh - n/A Special type
	Conning tower deck	Chromium Nickel-Molybdenum-Steel
	Upper deck canisters for torpedoes	Aluminum
	Casting	Hy 51
	Sheet	Hy 5 W
	Flood valves	Steel casting
	Flood valve frames	Steel casting
	Vent valves, casing	Steel casting
	Vent valves, seat	Steel casting with bronze
	Emergency vent valves	Steel casting

U-Boat Type VIIC	A. Ship Information	Page 9

U-boat Information	I. General	9

	HP air flasks	Chromium Nickel-Molybdenum steel

	Armatures	Steel casing with bronze
	Piping	Mild steel inside and galvanized outside
	Piping in fuel oil bunkers, battery room and fresh water tanks	Galvanized mild steel
All gear rods and linkages with their bearings installed outside the pressure hull are galvanized or made from sea water-proof material.

f)	Weights.
	I.	Ship's hull including ballast	= %
	II.	Auxiliary machinery for propulsion	= %
	III.	Armour	= %
	IV.	Propulsion plant including associated auxiliary machinery	= %
	V.	Gunnery	= %
	VI.	Torpedo weaponry	= %
	VII.	Equipment	= %
	VIII.	Fuel and lubricating oil	= %
	IX.	Weight reserve	= %
	Sum of I – IX = Construction displacement = 100%
	Note: Above data is not filled because it is secret.

g)	Stability.
	General.
	The stability of the boat can be expressed as the lever arm MG (so called "meta centric height"), i.e. the distance between the center of gravity G and transverse meta center M (intersection of the upward force of buoyancy and ship vertical center-line).
	The heeling of the boat by the force P by angle φ creates the righting arm (stabilizing arm):

	The position of the M over the buoyancy center F during -cruise depends on the position of the floating line (transverse water line gives the height of the M).

Page 10	A. Ship Information	U-Boat Type VIIC

10	I. General	U-boat Information

	When heeling angles are small (0-2°) the position of M can be considered as constant, so stabilizing arm * sin φ is also constant (starting stability).
	At large heeling angles the position of M is changing. In U-boats, however, the stability at large declinations is not calculated - as you know, U-boats with sufficient starting stability are stable at large heeling angles. The "starting stability" will be called "stability".
	During -cruise M overlaps with buoyancy center F:

	The stabilizing arm * sin φ is equal for longitudinal and lateral declinations. Longitudinal stability during -cruise is also as large as transverse stability, whereof it reacts to trim changes.
	During -cruise the longitudinal stability is very large (MG approximately = ship length).

Note: Free surfaces are not accounted for in stability considerations.

U-Boat Type VIIC	A. Ship Information	Page 11

U-boat Information	I. General	11

	Inclining test.
	The inclining test verifies previously calculated ship stability and is carried out by applying a well known heeling moment , which is equal to the righting moment .
	The deflection from the plumb-line gives the heel angle and then from

	the righting arm can be calculated.

	Stability Values for Type VII C U-boats
	For the following trim conditions the corresponding approximate stability values ratio apply:
	a:b:c:d: = 5:4:3:2

	a)	-cruise, trim condition A
	b)	-cruise, trim condition B
	c)	-cruise
	d)	The least stability is during diving, when the upper edge of the main ballast reserve fuel oil tanks comes under the surface.
	The stability of boats with G.W. engines is about 30 mm lower than in boats with M.A.N. engines.
	Note: For the absolute values of the meta centric height of the boats with M.A.N. and G.W. engines see secret documents.

3)	Weapons overview.
	a) Torpedo and mine armament.
	14 53-cm torpedoes may be carried
	4 in the bow torpedo tubes
	1 in the stern torpedo tube
	9 in reserve storage

Page 12	A. Ship Information	U-Boat Type VIIC

12	I. General	U-boat Information

In some torpedo stowage 2 TMA or 3 TMB mines can be stored in place of torpedoes.

The following examples of maximum load are provided:


	G 7a	G 7e	TMA	TMB

1	5	9	-	-
2	3	2	-	21
3	3	2	14	-
4	3	1	-	21
5	3	1	16	-

For storage see paragraph IV 1 c.

Artillery

1 cannon SK C/35, caliber 8.8 cm

1 machine gun C/30, caliber 2 cm

For munitions see paragraph IV 2 b.

Small arms

1 LMG C/34

2 Machine guns

3 Mauser pistols, caliber 7.65 cm

3 bayonets

2 signal pistols

For munitions see paragraph IV 4.

Safety and rescue equipment overview.

Structural safety installations.

Spherical bulkheads for pressure-tight partition	2
Watertight bulkheads	3
Hatch with retractable latches	1
Net cutter	2
Net deflector	3
Recognition marks for aircraft	1

U-Boat Type VIIC	A. Ship Information	Page 13

U-boat Information	I. General	13

Safety equipment.

High pressure air system, air volume at 205 at: 3900 liters

Oxygen renewal system, oxygen volume at 1 at: 75000 liters

Air purification system, sodium hydrate cartridges: 212 units

Emergency vent valves for the main ballast tank 3 and main ballast and reserve fuel oil tanks 2 and 4

Emergency blowing manifold (1) for all main ballast and main ballast and reserve fuel oil tanks

Emergency air supply connection (3 x 2) in each pressure-tight compartment

Automatically switched on emergency lamps: 8

Battery ventilation

Compartment ready indicating system

Hull closure indicating system

GHG installation

KDB installation

UT installation

Dry fire extinguisher 3

Foam fire extinguisher 1

Flooding installation

Drainage installation

Damage control materials

Rescue equipment.

Rescue buoys with night signal light	2
Battery powered hand lamps	8
Life buoys	3
Emergency escape gear	55
Life jackets	40
Diving suit	1
Diving suit without weighting systems	1
Watertight suit for the emergency escape set	1
Raft with buoy	2
Dinghy	1

For further information about safety and rescue equipment see section VIII.

Page 14	A. Ship Information	U-Boat Type VIIC

14	I. General	U-boat Information

Test data.

Speed

and


	Diesel engines			E motors

	Turns	Speed		Turns	Speed
		Condition A	Condition B
	R.P.M.	knots	knots	R.P.M.	knots	knots

	Ahead

2 x KF
KF	180	7.2	7.0	55	2.3	1.5
LF	275	10.2	10.0	110	4.5	3
HF	340	12.4	12.0	160	6.3	4.5
2 x HF	396	14.6	14.0	215	8.2	6
GF	435	16.3	16.0	250	9.3	7
AK	471	17.7	17.5	285	10.5	8
3 x AK	480	18.1	17.9	300	11

	Astern

KFz	180			55
LFz	210			110
HFz	250			160
2 x HFz	310			215
AKz	400			250

Diving time.

While staying still	seconds
At HF forward	seconds
Fast diving	seconds

Diving depth.

Construction depth	100 meters
Tested in pressure dock	105 meters
Deepest allowable depth

U-Boat Type VIIC	A. Ship Information	Page 15

U-boat Information	I. General	15

	d)	Depth differences for bow and stern.
		As per the chart on page 16.

6)	Practical values.
	a)	Speeds for various operating conditions.

Page 16	A. Ship Information	U-Boat Type VIIC

16	I. General	U-boat Information

Tauchungeunterschiede von Bug und Heck gegenüber der Druckmessertiefe

Diving differences for bow and stern opposed to the depth gage

Achterlastig Down by the stern

Bock für Netzabweiser Support for net deflector

Bug Bow

Bug (untere) Netzsäge Bow (bottom of) Net saw/cutter

Bug höher Bow higher

Bug tiefer Bow deeper

Grad Degrees

Heck Stern

Höhertauchung Shallower immersion

Kiel Keel

Netzsäge (oben) Net saw/cutter (top of)

Rudderhacke Rudder heel (bottom of the rudder)

Tiefertauchung Deeper immersion

Turm Conning tower

Vorlastig Down by the bow

U-Boat Type VIIC
A. Ship Information
Page 17

U-boat Information
I. General
17

b) Behavior of the boat under different rudder angle and wind conditions.

c) Turning circles.

Turning circle diameter

Depending on main rudder angle and speed.

Surfaced:

Trim Condition

Rudder angle

Turning circle diameter in meters

AK RPM=471

GF RPM=435

HF RPM=340

LF RPM=275

KF RPM=180

32°

270

265

253

245

230

30°

295

260

250

A

25°

350

310

290

20°

418

370

345

15°

530

475

440

32°

286

280

270

265

253

30°

B

25°

20°

15°

Page 18	A. Ship Information	U-Boat Type VIIC

18	I. General	U-boat Information

Submerged:


Circle to:	Rudder angle	Turning circle diameter in meters
Circle to:	Rudder angle	AK RPM=285	GF RPM=215	HF RPM=160	LF RPM=110	KF RPM=55

	32°	280	260	225	205	180
	30°		270
Port	25°		315
	20°		370
	15°		440
	10°		525

	32°		250
	30°		260
Starboard	25°		305
	20°		350
	15°		405
	10°		480

Note: RPM are valid at the moment of running into the turning circle and during the steady turning condition of the boat are accordingly lower.

Time to reciprocal heading

Rudder Hard Over

and


Speed setting	Time to Reciprocal heading
Speed setting	Trim Condition A	Trim Condition B	Submerged

AK	1 min 10 sec	1 min 13 sec	min sec
GF	1 min 11 sec	1 min 15 sec	min sec
HF	1 min 17 sec	1 min 23 sec	min sec
LF	1 min 33 sec	1 min 36 sec	min sec
KF	2 min 23 sec	2 min 35 sec	min sec

U-Boat Type VIIC	A. Ship Information	Page 19

U-boat Information	I. General	19

Time to put in and to take effect

with main rudders in astern cruise


Rudder angle	Time to put in		Time to result
Rudder angle	RPM=100	RPM=360	RPM=100	RPM=360

32°	7.3 sec	sec	8.8 sec	sec
30°	6.8 sec	sec	8.2 sec	sec
25°	5.8 sec	sec	7.0 sec	sec
20°	4.8 sec	sec	5.6 sec	sec
15°	3.8 sec	sec	4.3 sec	sec
10°	2.8 sec	3 sec	3.0 sec	3.5 sec

Main Rudder Limits

astern cruise


AK	GF	HF	LF	KF

10°	15°	32°	32°	32°

Page 20	A. Ship Information	U-Boat Type VIIC

20	I. General	U-boat Information

	d)	Behavior in a seaway.










	e)	Diving characteristics, crash dives.

U-Boat Type VIIC	A. Ship Information	Page 21

U-boat Information	I. General	21

	f)	Depth control characteristics.
		Normal









		In a seaway

Page 22	A. Ship Information	U-Boat Type VIIC

22	I. General	U-boat Information


		During torpedo firing









		During mine firing

U-Boat Type VIIC	A. Ship Information	Page 23

U-boat Information	I. General	23

	g)	Vibration:
		By engines at different RPM






		by torpedo firing




		by periscope with drag at speed
		Attack periscope (aft periscope):






		Air search periscope (forward periscope):

Page 24	A. Ship Information	U-Boat Type VIIC

24	I. General	U-boat Information

	h)	Sound levels (from testing with "U-45 and "U-51")
		(updated for VII C boats after testing)

		Boat lying on the bottom
		Sound from auxiliary machinery at 250 meters distance
		Operating: Underwater Telegraphy converter and gyro compass


Not heard	Quiet	Moderately loud	Loud	Very loud

Gyro compass-circulation pump	Radio converter	UT converter	Main drain pump	Auxiliary drain and trim pump
Gyro compass- converter	Hydraulic oil pump	Auxiliary LO pump		Air compressor
Extending attack periscope	W.C. pump	Retracting attack periscope		Drive motor for turning attack periscope
Extending air search periscope	Echolot (shallow depth device)	Retracting air search periscope
Tracking motor in torpedo data computer	Control valves for the periscope drive	Compartment ventilation fan	Walking in the boat	Speaking in the boat
Dive planes electric drive	Engine order telegraph without buzzer	Engine order telegraph with buzzer
Dive planes (hand drive)				Working in the boat
Main rudder electric drive	Main rudder (hand drive)			Echolot (deep depth device)

Boat hanging on the periscope

Sound from auxiliary machinery at 250 meters distance. Motors stopped. No auxiliary machinery

except for Underwater Telegraphy converter and gyro compass.


Not heard	Quiet	Moderately loud	Loud	Very loud

Extending air search periscope		Retracting air search periscope
Extending attack periscope		Retracting attack periscope

U-Boat Type VIIC	A. Ship Information	Page 25

U-boat Information	I. General	25

Boat at attack depth

Boat driven

at attack depth in a circle of 500 meters radius


Not heard	Quiet	Moderately loud	Loud	Very loud

One motor KF = 50 RPM
Attack periscope	Draining and trimming with air		Draining and trimming with auxiliary drain and trim pump
Dive plane driving motor	Operating both dive planes by hand

Both motors KF = 50 RPM	Compartment ventilating fan

Compartment ventilating fan				Both motors LF 100 RPM

Both dive plane driving motors		Both motors 80 RPM	Both motors 140 RPM	Both motors 250 RPM
Attack periscope		Both motors 50 RPM	Both motors 120 RPM	Both motors 200 RPM
Compartment ventilating fan			Both motors LF 100 RPM	Both motors 180 RPM
				Both motors 160 RPM

At starboard 110 and port 90 RPM the noise is weaker than with both motors at 100 RPM

Draining and trimming by means of air at 80 RPM or less: slight noise is audible.

Detection range with different RPM rates


At	80 RPM:	4500 meters	(Detection range particularly large because of howling sound)
At	160 RPM:	5000 meters	(Detection range lowered.)

Page 26	A. Ship Information	U-Boat Type VIIC

1	II. Boat and Pressure Hull	U-boat Information

II. Boat and Pressure Hull including thru-hull openings.

1.	General construction of U-boats.
	Type VIIC U-boats are medium sized mixed construction boats.
	The boat is built from following parts:
	pressure hull with conning tower
	outer shell
	upper deck and bridge deck.
	The conning tower, which is located above the control room at half of the pressure hull length is connected to it by means of the control room hatch.
	The outer shell encloses the stern, both sides and the bow of the pressure hull. The substructure of the upper deck extends over the full length of the boat and is welded to the pressure hull by means of knee-plates. To reduce the drag while submerged, the conning tower is enclosed by the conning tower casing.
	In the bottom of the pressure hull there is a 0.5 meter high and 1.1 meter wide keel box.

2)	Construction of the pressure hull.
	The pressure hull has a circular cross-section over its full length. The hull consists of one cylindrical and seven cone-shaped parts. These parts are joined together by arc welding, and strengthened from inside by 82 frames - which are made from bulb tee girders – and pressure-proof and watertight bulkheads. The quality of the arc welds are tested by the shipyard with radiographics. At first 25% of all welded joints on type VII boats were faulty, due to strict testing this number reached 15%. This ensures greater resistance to water pressure at deep depths. The thickness of the pressure hull plates decreases towards the ends.

U-Boat Type VIIC	A. Ship Information	Page 27

U-boat Information	II. Boat and Pressure Hull	2

	Especially stressed areas (i.e. under the conning tower and around the aft torpedo hatch, exhaust valves and diesel engine room patch) are further strengthened with thicker plates. Both ends of the pressure hull are enclosed by two outside cambered dished plates. The forward end of the pressure hull is adequately strengthened to account for the weakening due to the openings for the four torpedo tubes. The thickness of plating in the cylindrical part of the hull is 18.5 mm and decreases towards the forward and aft ends and in conical parts is 16 mm. The thickness of plating at both hull endings is 35 mm.

3)	Partitioning of the pressure hull.
	The pressure hull is divided into three compartments by two pressure-proof bulkheads and subdivided into six rooms by the following watertight bulkheads, which from aft are as follows: (see Chapter C: Tanks and installations plan)
	Compartment I (Frame 0-39).
	Room 1: Aft torpedo- and E motor room Frame 0 - 16-1/2
	1 stern torpedo tube, E motors, converters, switchboards, air compressors, driving motors for main rudders and after dive planes, torpedo compensating tank and after trim tank, 1 oxygen flask, 1 emergency fresh water tank.
	Under floor: stowage for 1 reserve torpedo, stowage for 3 distilled water containers.
	Room 2: Diesel engine room Frame 16-1/2 - 29
	Diesel engines and auxiliary machinery, 2 starting air flasks, 2 oxygen flasks.
	Under floor: lubricating oil supply tanks, lubricating oil collecting tanks, dirty oil tank, fuel oil collecting tanks.
	Room 3: Petty officers room Frame 29 - 39
	W.C., galley, stowage for provisions, automatic battery switch 1, refrigeration plant, HP air bank 3.
	Under floor: fresh water tank 1, waste water tank 1, fuel oil tank 1, battery room 1.

Page 28	A. Ship Information	U-Boat Type VIIC

3	II. Boat and Pressure Hull	U-boat Information

	Compartment II (Frame 39 - 50-1/2).
	Room 4: Control room.
	Main drain pump, auxiliary drain and trim pump, drive for aft (attack) periscope, control station for main rudder and dive planes, gyro compass, refrigeration plant, distilling unit, trimming station, fresh water tank 2, 4 oxygen flasks.
	Under floor: main ballast tank 3 (Frame 41 - 48).

	Compartment III (Frame 50-1/2 - 80).
	Room 5: Officers- and chief petty officers quarters Frame 50-1/2 - 60, radio- and underwater telegraphy room, listening room, automatic battery switch 2, stowage for provisions, W.C., fresh water tank 3.
	Under floor: fuel oil tank 2 (Frame 48 – 63), storage for explosive charges, munitions magazine, active sonar room, wash water tank, waste water tank 2, battery room 2.
	Room 6: Forward torpedo room Frame 63 - 80.
	4 bow torpedo tubes, auxiliary stowage for 2 reserve torpedoes, HP air pressure bank 4 and 5, 3 oxygen flasks.
	Under floor: stowage for 4 reserve torpedoes or mines, torpedo compensation tanks 2 and 3, forward trim tank.

4)	Conning tower structure.
	The shape of the conning tower in horizontal cross-section is an ellipse in the aft section and the arc of a circle in the lateral and forward sections. These parts are joined together without flat spots. The radius of the forward arc is 575 mm, and that of the side arcs 2260 mm. To decrease the drag of the conning tower during submerged cruise, the tower is enclosed with a casing.
	The conning tower is enclosed at the top by the bridge deck fabricated from 30 mm thick steel plate, which is welded to the conning tower walls. The thickness of the conning tower wall plates is 32 mm.

U-Boat Type VIIC	A. Ship Information	Page 29

U-boat Information	II. Boat and Pressure Hull	4

In conning tower are installed: aft (attack) periscope with hydraulic driving motor, main rudder steering station, torpedo fire control installation.

Openings in the pressure hull.

The opening in the pressure hull are necessary for:

Linkage and shafts

Lines

Hull fittings

Communication equipment

Measuring equipment.

All installations passing through the hull are tested at 15 at.

In each room there are the following openings:

Aft torpedo and E motor room.

Openings for linkage and/or shafts:
	For	Vent valve for main ballast tank 1	1
	"	Main rudder drive	1
	"	Aft dive planes	1
	"	Propeller shafts	2
	"	Outer torpedo tube door opening	1
	"	Vent valve for the stern buoyancy tank	1
	"	Torpedo loading hatch (clearance 660 mm)	1
Openings for lines:
	For	Emergency air supply and exhaust	2
	"	Mine ejection	2
	"	Blowing line for main ballast tank 1	1
	"	Lubrication for main ballast tank 1	1
	"	Hull valve in blowing line for stern buoyancy tank	1
	"	Flooding line for torpedo tube	1
	"	Vent line for torpedo tube	1
	"	Hull valve for HP air bank 1	1

Page 30	A. Ship Information	U-Boat Type VIIC

5	II. Boat and Pressure Hull	U-boat Information

Openings for hull fittings:
	For	Hull valve for cooling water discharge	1
	"	Hull valve for cooling water pump intake and flooding torpedo compensating tank	1

Diesel engine room.

Openings for linkage and/or shafts:
	For	Vent valve for main ballast and reserve fuel oil tank 2 stb. and port	1
	"	Main blowing valve for main ballast and reserve fuel oil tank 2 stb. and port	2
	"	Grinding mechanism for the exhaust gas valves stb. and port	4
	"	Ventilation exhaust foot valve	1
	"	Ventilation supply foot valve	1
	"	Diesel engine air induction trunk foot valve	1
	"	Selector valve for lubricating points	2
Openings for lines:
	For	Hull valve in fuel oil delivery line from main ballast and reserve fuel oil tank 2 stb. and port	2
	"	Hull valve for air evacuation for main ballast and reserve fuel oil tank 2 stb. and port	2
	"	Hull valve for fuel oil intake	1
	"	Hull valve for lubricating oil intake	1
	"	Hull valve for the compensating water line	1
	"	Ships steam heating connection	2
	"	Hull valve for HP air bank 2	1
Openings for hull fittings:
	For	Hull valve for cooling water pump stb. and port	2
	"	Assembly patch 4940 x 1890 mm and in this an assembly hatch 860 x 1890 mm	1

Petty officer room (with Galley).

Openings for linkage and/or shafts:
	For	Flood valves for main ballast and reserve fuel oil tank 2 stb. and port	4
	"	Emergency vent valves for main ballast and reserve fuel oil tank 2 stb. and port	2
	"	Marker buoy flooding and drainage operation shafting	2
Openings for lines:
	For	Blowing lines for main ballast and reserve fuel oil tank 2 stb. and port	2
	"	Hull valve for fuel delivery line from main ballast and reserve fuel oil tank 2 stb. and port	2

U-Boat Type VIIC	A. Ship Information	Page 31

U-boat Information	II. Boat and Pressure Hull	6

	For	Cooling water gravity tank (warm sea water)	1
	"	Hull valve for filling fresh water and wash water tanks	1
	"	Lubricating, flood valves main ballast and reserve fuel oil tank 2 stb. and port	4
Openings for hull fittings:
		Assembly patch (battery hatch) 550 x 420 mm	1
		Aft W.C.	2
		Galley hatch (600 mm diameter)	1

Control room.

Openings for linkage and/or shafts:
	For	Flood valves for main ballast and reserve fuel oil tank 4 stb. and port	4
	"	Emergency vent valves main ballast and reserve fuel oil tank 4 stb. and port	2
	"	Vent valve for main ballast and reserve fuel oil tank 2 and 4 stb. and port	2
	"	Vent valve for main ballast tank 3	2
	"	Flood valve for main ballast tank 3	4
	"	Diesel engine air induction trunk head valve	1
	"	Ventilation supply and exhaust head valve	2
	"	Emergency vent valves for main ballast tank 3	2
	"	Exhaust gas blowing valves	8
	"	Aft (air search) periscope (through the deck, main ballast tank 3, pressure hull and conning tower)	3
	"	DF antenna	1
Openings for lines:
	For	Lubrication of flood valves main ballast tank 3	8
	"	Lubrication of emergency vent valves main ballast tank 3	2
	"	Port and stb. blowing lines for main ballast tank 3	2
	"	Blowing lines for main ballast and reserve fuel oil tank 4 stb. and port	2
		Hull valve for emergency air supply and exhaust	2
		Hull valve for emergency blowing of main ballast tanks 1 and 5	2
		Compressed air measuring lines	8
		Hull valve for compressed air filling intake	1
		Tyfon air whistle	3

Page 32	A. Ship Information	U-Boat Type VIIC

7	II. Boat and Pressure Hull	U-boat Information

	For	Regulating tanks water level indicators	4
	"	Depth gages	4
	"	Log installation	2
	"	Vent line for regulating tank 2 port and stb.	2
	"	Vent line for regulating reserve fuel oil tank 1 port and stb.	2
	"	Viewing port for magnetic compass	1
	"	Vent gate valve for main ballast and reserve fuel oil tank 4 stb. and port	2
	"	Hull valve for oxygen intake	1
	"	Cooling water for gyro compass intake and discharge	2
	"	Drainage for compartment ventilation supply and exhaust and diesel engine air induction trunk head valves	3
	"	Hull valve deck washing water	1
	"	Hull valve in fuel oil delivery line from main ballast and reserve fuel oil tank 4 stb. and port	2
	"	Echo depth sounder (deep depth device)	3
	"	Intake for fine control of flooding regulating tanks and/or regulating reserve fuel oil tanks	1
	"	Telephone connection for pressure dock	1
	"	Lubrication for flood valves of main ballast and reserve fuel oil tank 4 stb. and port	4
Openings for hull fittings:
	For	Flood valves of main ballast tank 3	6
	"	Intake hull valve for fine flooding of regulating tanks	1
	"	Hull valve for flooding munitions magazine	1
	"	Hull valve from sea	1
	"	Hull valve discharge drain pump	1

Officers and Chief Petty Officer's Room.

Openings for linkage and/or shafts:
	For	Antenna trunk	1
	"	Active sonar	1
	"	Echo depth sounder (shallow depth device)	2
	"	Echo depth sounder (deep depth device)	3
	"	Underwater telegraphy	2
	"	Active sonar transducer/projector	2
	"	Marker buoy flooding drainage and operation shafting	3
	"	Cooling water gravity tank	1

U-Boat Type VIIC	A. Ship Information	Page 33

U-boat Information	II. Boat and Pressure Hull	8

Openings for hull fittings:
	"	Forward W.C.	2
	"	Assembly patch (battery hatch) 700 x 445 mm	1

Forward torpedo room.

Openings for linkage and/or shafts:
	For	Control valve for anchor capstan	1
	"	Clutch and brake for anchor capstan	1
	"	Anchor release mechanism	1
	"	Chain stopper	1
	"	Shifter for raising and lowering anchor	1
	"	Forward dive planes	1
	"	Annunciator mechanism for length of extended chain	1
	"	Vent valve for main ballast tank 5	1
	"	Vent valve for bow buoyancy tank	1
	"	Outer torpedo tube door opening	4
Openings for lines:
	For	Passive sonar array	4
	"	Transmitter for underwater telegraphy	4
	"	Rotating passive hydrophone	1
	"	Hull valve for emergency air supply	1
	"	Hull valve for emergency air exhaust	1
	"	Hull valve for HP air bank 6	1
	"	Mine ejection	4
	"	Blowing line for main ballast tank 5	1
	"	Blowing line for bow buoyancy tank	1
	"	Flooding line for torpedo tubes	4
	"	Vent line for torpedo tubes	4
	"	Lubrication for vent valve for main ballast tank 5	1
Openings for hull fittings:
	For	Forward torpedo loading hatch (clearance 660 mm)	1
	"	Hull valve from sea for flooding torpedo compensating tanks 2 and 3	1
	"	Forward torpedo tubes	4

Page 34	A. Ship Information	U-Boat Type VIIC

9	II. Boat and Pressure Hull	U-boat Information

Conning tower.

Openings for linkage and/or shafts:
	For	Forward (attack) periscope	1
Openings for lines:
	For	Targeting and gyro compass repeater	2
	"	Torpedo fire control installation	2
	"	Bridge main rudder angle indicator	1
	"	Air whistle	3
	"	Voice tube	1
	"	Emergency air supply	1
Openings for hull fittings:
	For	Air connection to the bridge	1
	"	Conning tower hatch	1
Openings for lines in floor of conning tower:
	For	Emergency air supply	1
	"	Emergency air exhaust	1
	"	Voice tube	2
	"	Hydraulic oil for periscope (pressure and return)	2
	"	Dive planes angle indicator	1
	"	Drainage	2
	"	Air supply to conning tower	1
	"	Air exhaust from conning tower	1

Construction of the outer shell.

Aftership.

In the stern part of the outer shell are located main ballast tank 1 and the stern buoyancy tank, both with flood openings. The main top beams are: 1 longitudinal main girder in the middle and 2 shorter, lateral girders, all welded to the aft top part of pressure hull.

The main bottom beams: 2 heavy stringers.

The stringers with transversal frames and top middle girder are assembled into a truss. The truss is strengthened in the transverse direction by means of the torpedo tube bulkhead.

U-Boat Type VIIC	A. Ship Information	Page 35

U-boat Information	II. Boat and Pressure Hull	10

	The aft torpedo tube is used as horizontal bracing for the stern buoyancy tank.
	In the bow part of outer shell is located the main ballast tank 5 and the bow buoyancy tank, both with flood openings.
	The main top beams: 2 I-girders reaching the forward torpedo tubes bulkhead and one main girder in the middle reaching the bow.
	The main bottom beams: 1 heavy I-girder.
	The bow part of outer shell in the area of the torpedo tubes shutters is not braced by girders. An additional middle girder is located above the bow buoyancy tank at the deck.
	All girders and decks are joined by transversal frames, supporting and uniting the torpedo tube bulkhead and the buoyancy tank bulkhead into one strong structure.

	Saddle tanks.
	The main ballast and reserve fuel oil tanks, regulating and reserve fuel oil tanks, regulating tanks and negative buoyancy tanks are built as lateral saddle tanks, with frames welded to the pressure hull by means of knee-plates. The regulating and reserve fuel oil tanks, regulating tanks, and negative buoyancy tanks are made pressure-proof.

	Upper deck.
	The upper deck spreads over the full length of the boat. The frames of the upper deck are connected with pressure hull by means of knee and support plates. Two support girders made from Z-shaped iron brace the upper deck. The wooden deck, side plates and all free-flooding spaces have flooding holes to prevent the formation of air pockets when diving.

	Conning tower.
	The conning tower casing is made from light plates.
	This casing encloses:
	Air trunks, aerials trunks, DF antenna, rod antenna, forward (air search) periscope, pressure-proof container for MG C/30 gun barrels, cooling water gravity tank. The top part of the conning tower casing is a bridge, used as command station when surfaced and as a platform for the MG C/30 gun.

Page 36	A. Ship Information	U-Boat Type VIIC

11	II. Boat and Pressure Hull	U-boat Information

Special stiffeners.

The parts of the torpedo tubes extending beyond the pressure hull are supported by torpedo tube bulkheads located in stern and bow parts of the outer shell. Places especially exposed to loads (area of dive planes, torpedo guiding plates, the widest part of the hull, shaft support, anchor capstan etc.) are braced with stringers, girders and beams.

Partitioning of the outer shell.

After end: from aft to Frame 12.
	Stern buoyancy tank	Stern post		to		Fr. 10
	Flooded space		Fr. -10	to		Fr -9
	Main ballast tank 1		Fr. -9	to		Fr. +4/6
	Free flooded space		Fr. +4/6	to		Fr. +12
Amidships: from Frame 19 to Frame 79.
	Free flooded space		Fr. +19	to		Fr. +24
	Main ballast and reserve fuel oil tank 2 stb.		Fr. +24	to	PH.	Fr. +34
	Main ballast and reserve fuel oil tank 2 port		Fr. +24	to	PH.	Fr. +34
	Regulating and reserve fuel oil tank 1 stb.	PH.	Fr. +34	to	PH.	Fr. +38
	Regulating and reserve fuel oil tank 1 port	PH.	Fr. +34	to	PH.	Fr. +38
	Regulating tank 2 stb.	PH.	Fr. +38	to	PH.	Fr. +44
	Regulating tank 2 port	PH.	Fr. +38	to	PH.	Fr. +44
	Negative buoyancy tank stb.	PH.	Fr. +44	to	PH.	Fr. +46
	Negative buoyancy tank port	PH.	Fr. +44	to	PH.	Fr. +46
	Main ballast and reserve fuel oil tank 4 stb.	PH.	Fr. +46	to		Fr. +75
	Main ballast and reserve fuel oil tank 4 port	PH.	Fr. +46	to		Fr. +75
	Free flooded space		Fr. +75	to		Fr. +79
Fore ship: from Frame 92 to bow
	Main ballast tank 5		Fr. +92	to		Fr. +106
	Free flooded space		Fr. +106	to		Bow
	Bow buoyancy tank		Fr. +102	to		Fr. +113
The chain locker is located in main ballast tank 5			Fr. +101	to		Fr. +103

U-Boat Type VIIC	A. Ship Information	Page 37

U-boat Information	III. Diving Installations	1

III. Diving Installations.

1)	Tanks and fuel oil tanks.
	a)	Main ballast tanks.
		Three main ballast tanks are provided, which give the boat the buoyancy necessary for surfaced cruise: main ballast tanks 1 and 5 are located respectively at the aft and forward end of the outer shell, main ballast tank 3 is located inside the pressure hull under the floor of control room. Main ballast tanks 1 and 5 have flooding slits and one vent valve each. The vent valve of main ballast tank 5 opens to the outside - in the opposite direction from all the other vent valves. Main ballast tank 3 is sickle shaped, and is strengthened with perforated bulkheads. On the port and stb. sides there are three rectangular, outward opening, flood valves, which are operated by means of four linkage rods from the control room. Venting of main ballast tank 3 takes place through two separate port and stb. pressure-proof trunks near the aft part of control room, which are then led through the port and stb. regulating fuel oil tanks respectively. These trunks are provided with vent valves, which are independently operated. In the area of passing through the pressure hull, the vent trunks are provided with two emergency vent valves, which are operated manually from the control room. The emergency vent valves are opened in normal conditions and are shut only in case of damage to the vent trunks.

	b)	Main ballast and reserve fuel oil tanks.
		Main ballast and reserve fuel oil tanks 2 and 4 port and stb. are located in the outer shell. The flood valves of these tanks are operated from inside the boat and open inwards. Venting of tanks takes place through venting trunks. Trunks from stb. tank 2 and stb. tank 4 are led to a common vent valve at the stb. side. The same arrangement is made for the port tanks.

Page 38	A. Ship Information	U-boat Type VIIC

2	III. Diving Installations	U-boat Information

		Vent valves are operated from the control room. Each vent trunk also has an emergency vent valve installed directly at the joint with the tank operated from inside. The emergency vent valves are closed in case of damage to the vent trunks. After each emergency vent valve a gate valve installed, which should be closed, when the tanks are filled with fuel oil.
		Main ballast and reserve fuel oil tanks 2 port and stb. are also fitted at their after ends with a residual air vent installation. There are two cut-off valves installed at the joints with the tanks and two vent valves port and stb. Both vent valves are operated manually from control room by means of linkage rods.

	c)	Stern and bow buoyancy tanks.
		The aft and forward parts of outer shell are constructed as stern and bow buoyancy tanks and are used to dampen longitudinal pitching of the boat. Both tanks have flood slits and one vent valve each.

	d)	Regulating tanks.
		To compensate for changes of weight caused by consumption of provisions, fuel oil, munitions, different number of crew and buoyancy changes due to leakage, regulating tanks 2 port and stb. are provided. They are located on both sides of pressure hull near the control room and are pressure-tight. The amount of water inside the tanks is readable by means of water level indicators or measurable by means of an air pressure gauge. The regulating tanks are connected to the drainage installation in control room and can be drained by main drain pump, auxiliary drain and trim pump as well as by means of compressed air.

U-boat Type VIIC	A. Ship Information	Page 39

U-boat Information	III. Diving Installations	3

	e)	Regulating reserve fuel oil tanks.
		The regulating reserve fuel oil tanks 1 port and stb. are also located outside the pressure hull between main ballast and reserve fuel oil tanks 2 and the regulating tanks. They are pressure-tight and have the same flood and drain ability as regulating tanks except for blowing with compressed air. The amount of the water inside the tanks is measured by means of air pressure gauge. The tanks can be used either as regulating tanks or fuel oil tanks. When used as fuel oil tanks, they are connected with low pressure air installation (through pressure reducing valve to 0.5 at) and with fuel oil delivery lines. The tanks are also fitted with their own venting and sounding lines.

	f)	Trim tanks.
		The previous consideration of submerged stability (the longitudinal stability during -cruise is as great as transverse stability) that said, even relatively small changes in weight displacement in the longitudinal axis cause trim changes. To compensate for changes of trim during torpedo and mine launching, provision consumption and so on, the trimming installation is provided. In the forward and aft torpedo rooms there are two trim tanks, located 41.6 meters apart. They are connected by a pipeline with a water meter, trim line valve and trim controller. Trimming takes place by means of compressed air or the auxiliary drain and trim pump.

	g)	Negative buoyancy tanks.
		The negative tanks stb. and port are located outside the pressure hull, forward of the regulating tanks. They are provided to reduce diving time. The tanks are constructed as pressure-proof. Each tank is flooded by a flood valve operated from control room. Tanks are vented inside the boat and blown by means of compressed air.

Page 40	A. Ship Information	U-boat Type VIIC

4	III. Diving Installations	U-boat Information

	h)	Torpedo compensating tanks.
		The torpedo compensating tanks accept water for compensating the weight of a torpedo or mine as well as the surrounding water. Two tanks are located in forward torpedo room and one tank is located in E motor room.
		Each torpedo compensating tank has its own sounding pipe, can be flooded with sea water through a water meter and is connected to the drainage installation. Torpedo compensating tank 2 in the forward torpedo room is also connected with hand wash water pump in the forward W.C.

2) Blowing installation.
	a)	Compressed air blowing.
		The main ballast tanks are blown with compressed air controlled from the blowing distributor, which is located on the stb. side of the control room. Blowing takes place until the boat has sufficient buoyancy to safely open the conning tower hatch.
		All blowing lines are led inside the pressure hull and at places where they pass through hull to tanks they are fitted with cut-off valves. The highest pressure in the installation is 25 at.

	b)	Exhaust gas blowing.
		Exhaust gas from the diesel engines is used to blow residual water from the ballast tanks. The exhaust gases are fed through the main blowing valves port and stb. to the exhaust gas blowing manifold. The manifold is located outside the pressure hull, over the control room, on the stb. side. Linkage rods pass through the hull to control room.
		The exhaust gas pressure measured in control room should be 0.5 at.

3) Venting and vent valves.
		All ballast tanks and reserve fuel oil ballast tanks as well as stern and bow buoyancy tanks are fitted with vents that are operated from inside the hull by means of linkage.

U-Boat Type VIIC	A. Ship Information	Page 41

U-boat Information	III. Diving Installations	5

		For protection against foreign bodies the tank vents are cased with steel plates and wired mesh. The vent valves of bow and stern buoyancy tanks are operated from the forward and aft torpedo room respectively. The vents of main ballast tanks and reserve fuel oil ballast tanks are operated from control room. Main ballast tank 1 has a vent valve which is operated by means of a linkage rod and hand wheel located at the aft bulkhead of the control room. Main ballast tank 3 is vented through pressured trunks port and stb., which pass through regulating tank 2 port and stb. and lead to vent valve chambers located above pressure hull. The valves are operated from control room by means of hand levers.
		Main ballast and reserve fuel oil tanks 2 and 4 port as well as main ballast and reserve fuel oil tanks 2 and 4 stb. have on both sides vent ducts installed outside the pressure hull, which lead to common vent valve chambers port and stb. respectively. The common vent valves port and stb. are operated from the control room by means of hand levers.
		Main ballast and reserve fuel oil tanks 2 port and stb. are also provided with a residual air vent installation. Both residual air vent valves are operated by one common hand wheel.
		Main ballast tank 3, main ballast and reserve fuel oil tanks 2 port and stb. and main ballast and reserve fuel oil tanks 4 port and stb. also have emergency vent valves installed, operated from control room and petty officers room respectively.
		After filling the reserve fuel oil ballast tanks with fuel oil, the vents can be secured by closing the gate valves installed in the vent and residual air vent trunks.
		Main ballast tank 5 has a vent valve, which is operated by means of a linkage rod and hand wheel located at the forward bulkhead of the control room.

4) Compressed air systems.
	a)	Electric air compressor.
		The compressed air required for blowing ballast tanks, starting diesel engines, for torpedo launching installation, anchor installation and so on, is produced by two electric, 4-stage air compressors, located in the aft torpedo room.

Page 42	A. Ship Information	U-Boat Type VIIC

6	III. Diving Installations	U-boat Information

		Their performance is 6.1 liters/minute at 205 kg/cm².
		Compressed air from each stage is cooled down in a cooler. The air cooler and lubricating oil cooler are located in one case outside the compressor. The compressor is cooled by sea water. The two-stage cooling water pump is located on the coupling side of compressor and is driven by means of helical gears from the crankshaft. The gear type lubricating oil pump is located on the front side of compressor at its base plate and is driven from the crankshaft by means of gear wheels.
		The compressor is driven by a direct current, shunt electric motor, with starting compound winding on commutating poles. The motor is splash-proof and self-cooled with air.

	b)	Diesel air compressor.
		Type VIIC U-boats since Boat No. ____ are provided with one electric air compressor and one diesel air compressor.
		The diesel air compressor is a horizontal, double piston, two-stroke diesel engine with free pistons which are directly coupled with a four-stage compressor. Its performance is 8.5 liters/minute at 205 kg/cm².
		After compression the air from each stage passes through a condenser for cooling. The cooler for all four stages is located beneath the compressor in individual cases. The air is cooled by means of sea water. The cooling water pump, rotary vane type, driven by a gear shaft, forces the water in the following order: cooler IV, combustion chamber cooling jacket, compressor stage I, compressor stage IV, cooler III, compressor stage III, compressor stage II, cooler I, cooler II.
		The lubricating oil pump, driven by means of an eccentric from the gear shaft, lubricates all sliding parts.
		The compressor is driven by two-stroke diesel engine made by Junkers, with two opposed pistons,

U-Boat Type VIIC	A. Ship Information	Page 43

U-boat Information	III. Diving Installations	7

which are coupled together by means of two sets of traverses, two gear racks with a geared wheel located between them. Engine pistons control intake of air, which is compressed and exhausted. The stage I compressor piston is connected with left engine piston, the stage II compressor piston is connected with right engine piston. The stage IV compressor piston is coupled with the left piston rack and the stage III compressor piston is coupled with the right piston rack. The compressor is started by means of compressed air admitted to particular compressor stage chambers.

The compressor casing is splash-proof.

High pressure compressed air flasks.

Compressed air is stored in 12 high pressure air flasks with total capacity of 3.900 m³. Each flask has capacity of 325 liters and is tested at pressure of 280 at. The flasks are grouped in 6 banks (2 flasks each), which are located as follows.

Bank 1	Upper deck aft, on both sides of the aft external torpedo container
Bank 2	Upper deck, above the diesel engine assembly patch
Bank 3	Petty officer's room port and stb.
Bank 4	Forward torpedo room to port
Bank 5	Forward torpedo room to stb.
Bank 6	One flask in the bow buoyancy tank, one flask on the stb. side forward of the external torpedo container.

The flasks are smooth shaped and are lined with lead. On both ends they narrow into the neck, capped by means of flange and cover. To drain the flask a drainage pipe is provided in the deepest point of flask. Furthermore, the flasks are inclined 4 degrees from the horizontal.

Compressed air equipment.

The following compressed air equipment is installed:

1. High pressure equipment

Page 44	A. Ship Information	U-Boat Type VIIC

8	III. Diving Installations	U-boat Information

		2. Medium pressure equipment
		3. Low pressure equipment
		Particular devices are supplied with pressure air from high air pressure distributor, low air pressure distributor and blowing distributor. For blowing regulating tanks, regulating reserve fuel oil tanks and negative tanks one or more manifolds are provided in the control room.

High Pressure Air Distributor.

		1.		To blowing distributor
		2.		From HP air bank 2
		3.		" " " 6
		4.		" " " 1
		5.		" " " 5
		6.		" " " 3
		7.		" " " 4
		8.		From HP air filling connection on upper deck
		9.		To Blowing manifold for regulating tanks and negative tanks
		10.		To torpedo HP air manifold aft
		11.		To torpedo HP air manifold fwd.
		12.		From HP air compressors
		13.		To pressure reducing valve LP air manifold
		14.		To LP air manifold
		15.		Drain valve
		Valves 2-7 are provided as adjustable cone stop-check valves with pressure gages.

U-Boat Type VIIC	A. Ship Information	Page 45

U-boat Information	III. Diving Installations	9

Blowing Distributor for Ballast Tanks

		1.		Master blowing valve for ballast tanks
		2.		Individual blow valve for MBT 1
		3.		" " " " MBT 5
		4.		" " " " MBT 3 stb.
		5.		" " " " MBT 3 port
		6.		" " " " MB/RFOT 2 stb.
		7.		" " " " MB/RFOT 2 port
		8.		" " " " MB/RFOT 4 stb.
		9.		" " " " MB/RFOT 4 port
		10.		Drain valve
		11.		To blowing distributor for regulating tanks, regulating and reserve fuel oil tanks, and negative tanks
		The master blowing valve and the valves for main ballast tanks 1 and 5 are provided with sharply tapered seats for fine control.

Low Pressure Air Distributor

		1.		Regulating valve LP air distributor
		2.		To pressure reducing valve
		3.		To Tyfon air whistles
		4.		To torpedo LP air manifold aft
		5.		To torpedo LP air manifold forward
		6.		To pneumatic tool connection
		7.		To compressed air clutch for forward and aft dive planes
		8.		To blow trim tanks
		9.		To compressed air gauge
		10.		To blow sea connection for flooding regulating tanks and distilling unit intakes
		11.		Regulating valve for raising direction finding antenna
		12.		Drain valve

Page 46	A. Ship Information	U-Boat Type VIIC

10	III. Diving Installations	U-boat Information

Blowing distributors for regulating tanks, regulating and reserve fuel oil tanks and negative tanks

For blowing regulating tanks, regulating and reserve fuel oil tanks, and negative tanks a blowing manifold is provided in the control room. The safety valves for regulating tanks and regulating and reserve fuel oil tanks are set at 13 at and for negative tanks at 10 at. Each regulating tank has a pressure differential gauge installed.

(Regulating/RFO tanks) (Regulating tanks) (Negative buoyancy tanks)

1.	Regulating valve - regulating tanks, regulating and reserve fuel oil tanks, and negative tanks
2.	Blow valves for regulating tanks, regulating and reserve fuel oil tanks, stb. and port
3.	Hull valve negative tanks stb. and port (stop check valve)
4.	Drain valve
5.	To blowing distributor for main ballast tanks

5) Pumps.
		The following pumps are part of the diving installation:
		a) main drain pump
		b) auxiliary drain and trim pump.
		The main drain pump is a self-priming, switchable, two stage, centrifugal type. It is built from two impellers, which can be connected either in serial (high pressure - low performance) or parallel (low pressure - high performance).
		Its performance at pressure head of 15 meters H₂O in parallel mode is 1300 liters/minute and at pressure head of 105 meters H₂O in serial mode is 500 liters/minute at RPM = 2600.

U-Boat Type VIIC	A. Ship Information	Page 47

U-boat Information	III. Diving Installations	11

		The pump is driven by an electric motor and is used to drain large quantities of water from regulating tanks, regulating and reserve fuel oil tanks, torpedo compensating tanks and from rooms during flooding. When draining from the forward and aft parts of the boat, pump performance is reduced due to flow resistance in pipelines (see paragraph IX 3 d).
		The auxiliary drain and trim pump is a double-acting, two cylinder, piston type. The pump is driven by an electric motor built above by means of worm gear with a vertical worm shaft.
		Its performance is 358 liters/minute at RPM = 115. The maximum operating pressure is 10 at. The pump is used to drain small quantities of water from regulating tanks, regulating reserve fuel oil tanks, torpedo compensating tanks, bilges and for trimming. Both the main drain pump and the auxiliary drain pump have the capability of pumping water out to main ballast tank 3.

6) Dive planes.
		For controlling depth there are two sets of dive planes, aft located directly after the propellers and forward located laterally below the torpedo tubes. Both set of dive planes are protected with frames, the aft edge of the forward planes also with guy wires. Dive planes are driven either electrically or manually. The dive planes station for electric and manual control as well as for operating the compressed air pistons of the dive plane clutches are located in the control room.

Page 48	A. Ship Information	U-Boat Type VIIC

1	IV. Armament	U-boat Information

IV. Armament.

1) Torpedoes and mines.
	a)	Torpedo tubes.
		The boat is equipped with 4 forward and one after torpedo tubes, whose diameter is 553.6 mm and whose length is 7552 mm. 2/3 of the length of these 5 tubes is located outside the pressure hull and they are supported by the ends of pressure hull and by torpedo tube bulkheads in the bow and aft parts of outer shell. Torpedo launch takes place by means of compressed air.
		The tubes consist of forward, middle and aft sections, joined together by means of flanges and bolts. The forward part is closed with an outer door, which opens on a vertical axis towards amidships. The breech door located at the inner end of tube is closed and secured by means of a locking ring. The interlock mechanism between the breech and outer door operating gears prevents simultaneous opening.
		The following installations pass through the pressure hull:
		Outer door operating shafts,
		Flood and drainage installations,
		Venting installation for the forward parts of tubes,
		Compressed air installation for the mine stop bolt actuator.
		The tubes are provided with gears for setting the desired depth, speed and gyro angle of a loaded torpedo during attack approach. The air impulse tank capacity is 220 liters and is used to provide compressed air for torpedo launch. During torpedo launch, the firing rod gear retracts the torpedo stop bolt and admits air into the tube.
		To avoid the appearance of air bubbles, which could betray the boats position, a suppressor is provided.

U-Boat Type VIIC	A. Ship Information	Page 49

U-boat Information	IV. Armament	2

Distances between tube axes.

Forward torpedo tubes Aft torpedo tube

	b)	Installation for mine ejection.
		All 5 tubes are adapted for mine ejection in addition to torpedo launching.

	c)	Stowage.
		The largest payload of torpedoes and mines can be arranged as follows:

Page 50	A. Ship Information	U-Boat Type VIIC

3	IV. Armament	U-boat Information


Payload	In torpedo tubes		In reserve stowage		In deck containers		In auxiliary stowage
Payload	fwd.	aft	fwd.	aft	fwd.	aft	fwd.

Case 1
5 G 7 a			2	1	1	1
9 G 7 e	4	1	2				2

Case 2
3 G 7 a				1	1	1	-
2 G 7 e	2						-
21 TMB	6	3	12				-

Case 3
3 G 7 a				1	1	1	-
2 G 7 e	2						-
14 TMA	4	2	8				-

Case 4
2 G 7 a				1	-	1	-
1 G 7 e	1				-		-
24 TMB	9	3	12		-		-

Case 5
3 G 7 a				1	1	1	-
1 G 7 e	1						-
16 TMA	6	2	8				-

Cases 1-5 are feasible down to sea water density (1.003) without additional changes in trim and weight of the boat.

		G7a can be stored in all places except auxiliary stowage, because there the engine chamber would be positioned at the support point.
		G7e can not be stored in both deck containers and in aft reserve stowage because access for maintenance is insufficient.
		TMA and TMB can not be stored in: both deck containers, auxiliary stowage under forward torpedo room floor and in aft reserve stowage. These locations are intended only for torpedoes, and set the minimal number of torpedoes that could be carried in the forward torpedo room. Mines cannot be stored in the aft torpedo room because of danger from electric fields, therefore TMA and TMB mines should be loaded into the aft torpedo tube only when the electric motors are disengaged. Case 3 with 14 TMA corresponds to case 2 with 21 TMB. Case 5, with 16 TMA, allows one more torpedo to be carried than case 4 with 24 TMB.

U-Boat Type VIIC	A. Ship Information	Page 51

U-boat Information	IV. Armament	4

Secured storage for torpedo munitions (9 contact pistols and 10 torpedo fuses) is provided in the forward torpedo room.

Torpedo loading equipment.

Torpedoes can be loaded from land or from ships by means of a port or ship crane, or from the water by means of a portable crane. This crane can be mounted on the forward upper deck on port side, or, on the after deck on either the port or starboard side of galley hatch.

To transport torpedoes into the boat, a chute is installed; supporting beams are used to assure proper motion of the torpedo despite rolling of the boat. Torpedoes are pulled down by means of windlasses, which are installed either on the conning tower or near the galley hatch.

Transport splints with gear racks are installed in the boat. Each splint is hung by means of two hoists and three holding lugs. The splint is equipped with two trolleys. The torpedo is attached to these trolleys by means of steel bands. The torpedo is moved longitudinally by means of the aft trolley, which is equipped with gear rack and crank arm. Two transverse splints are provided for lateral movements.

Mines are loaded using the same equipment.

Torpedo fire control system.

Torpedo Direction Computing installation

The torpedo direction computing installation is intended to calculate the gyro angle based on estimated and measured values and to transmit it to torpedo tube electrically (single or salvo shot without turning the boat).

Consists of the following parts:
On the bridge:	1	Surface sight with target bearing transmitter and pedestal

Page 52	A. Ship Information	U-boat Type VIIC

5	IV. Armament	U-boat Information

In the conning tower	1	Torpedo data computer
	1	Target bearing transmitter 1 (for attack periscope)
	1	Terminal box (for surface sight)
	1	Fuse box
In control room	U-boat coupling and transmitting equipment
	1	Target bearing transmitter 2 (for air search periscope)
	1	Switch box
	1	Blue switch
	2	Fuse box
	1	Main switch box (with starter and regulator for rotary converter and torpedo gyro setting gears and fuses for torpedo fire control system)
In forward torpedo room	1	Torpedo gyro angle receiver
In aft torpedo room	55 V AC rotary amplifier for the gyro angle setting gear

Firing data from the conning tower and control room are transmitted electrically to torpedo gyro angle receivers. In the forward and aft torpedo rooms the gyro angle of the torpedo can be set electrically or manually by means of gyro setting gears.

This installation is powered with AC voltage from auxiliary switchboard 1 through rotary converter located in aft torpedo room (the servo motors are powered from auxiliary switchboard 2).

The transmitter of the torpedo order indicator system located in the conning tower provides transference of orders (“flood torpedo tubes”, “open outer doors”, “get tubes ready” and so on) from the conning tower to order receivers in the forward and aft torpedo rooms.

Torpedo firing installation.

The firing installation provides electrical firing from the bridge and from the conning tower in addition to mechanical launching at the tube.

U-Boat Type VIIC	A. Ship Information	Page 53

U-boat Information	IV. Armament	6

Consists of following parts:

On the bridge:	Pressure resistant firing switch
In the conning tower:	1	Firing switch
	1	Lamp board for the five tubes
	1	Terminal box (for firing switches)
In the control room:	Switch box with
	Selector switch for bridge or conning tower
	Selector for single shot
	Selector for salvo shot
	Salvo interval timer
	Fuse box
In the forward torpedo room:	1	Tube distributor box
	1	Ready lamp box
	4	Firing electromagnets with automatic cut-off switches
In the aft torpedo room:	2	Torpedo-charging units

The salvo interval timer launches the torpedoes when salvo is selected at predefined time intervals. In the case of failure of the electrical firing system, the flashing of corresponding lamps indicates the time delay for mechanical launch.

The firing installation is powered with 110 DC voltage from auxiliary switchboard 2.

Torpedo Order Indicating System.

In the conning tower:	Optical and acoustic order transmitter
In the control room:	Acoustic order transmitter
In the forward torpedo room:	Optical and acoustic order receiver
In the aft torpedo room:	Optical and acoustic order receiver

Weight compensation during torpedo firing and mine ejecting.

To drain water from tubes and to compensate for the weight of launched torpedoes two torpedo compensating tanks are provided in the forward torpedo room and one torpedo compensating tank in the aft torpedo room. Tanks are connected to the drain installation and are equipped with venting and sounding pipes. The forward tanks are flooded through a hull valve on the port side of hull.

Page 54	A. Ship Information	U-Boat Type VIIC

7	IV. Armament	U-boat Information

		The tank in aft torpedo room is flooded from the intake for the cooling water pump. For capacities of torpedo compensating tanks see paragraph A I 2 d.

U-Boat Type VIIC	A. Ship Information	Page 55

U-boat Information	IV. Armament	8

Weight and Balance for torpedoes


Torpedo Types		G. 7a Model	G. 7a Model Combat	G. 7a Drill 60 at	G. 7a Drill 100 at	G. 7a Drill 130 at	G. 7a Drill 200 at	G. 7a Combat 200 at	G. 7e Model Combat	G. 7e Drill	G. 7e Combat


Torpedo weight	kg	1245.5	1540.5	1406	1438	1462	1518	1528	1573.5	1279	1606
Torpedo displacement	liters	1310.5	1310.5	1254	1254	1254	1254	1254	1310.5	1306	1306
Volume to flood tube	liters	370	370	426	426	426	426	426	370	374	374
Positive and buoyancy	kg	65	230	152	184	208	264	274	263	27	300
Trim moment - forward shot	mkg	+1661	-5879	-3885	-4703	-5316	-6748	-7003	-5741	+692	-7689
Trim moment - aft shot	mkg	-1720	+6086	+4022	+4869	+5504	+6985	+7250	+5977	-716	+7959

To calculate trim moment the distance between boat and torpedo G7 a or G7 e gravity center is taken as moment arm.

Weight and Balance for mines


Mine types		T.M.A.	T.M.B.	T.M.B.Ex.

Total weight (Case and Anchor)	kg	806	742	740
Mine displacement	liters	585	470	459
Surrounding water 1 mine	liters	1095	1210	1221
Surrounding water 2 mines	liters	510	740	762
Surrounding water 3 mines	liters		270	303
Buoyancy	kg	221	272	281
Trim moment - forward eject	mkg	-5547	-6827	-7053
Trim moment - aft eject	mkg	+5746	+7072	+7306

Page 56	A. Ship Information	U-Boat Type VIIC

9	IV. Armament	U-boat Information

2) Gunnery.
	a)	Weapons.
		8.8 cm Gun (S.K. C/35).
		The gun is installed on deck forward of the conning tower near hull frame 54. The gun mounting is pyramid shaped and is strengthened by longitudinal and transverse supporting beams.
		The upper deck is widened to about 3800 mm in the area of gun mounting.

		M.G. C 30.
		The M.G. C 30 gun is installed on the aft part of conning tower casing. The base is formed as a cylindrical column attached to pressure hull, strengthened with 4 knee sheets.

	b)	Ammunition.
		Total amount of ammunition that can be carried:
		8.8 cm munitions: 205 rounds HE shell C/35
		MG C/30 munitions: 1500 rounds
		Of these in munitions magazine in officers room between Frames 50 ½ – 53:
		177 rounds 8,8 cm HE shell C/35
		1200 rounds MG C/30
		Ready-use ammunition for the S.K. C/35 is stored in pressure-proof canisters [one shell to a canister placed in a rack] in the upper deck just aft of and outside the operating circle to both sides of the conning tower:
		28 rounds 8.8 cm HE shell C/35
		3 ammo clips with 20 rounds each are stored in the conning tower.
		The munitions magazine in officers room is connected to the flooding and drainage installation.

3) Mine and demolition equipment.
		For TMA and TMB mines stowage see paragraph IV 1 c.
		Additional demolition equipment includes:
		2 boxes with 4 demolition charges each [for self destruction]

U-Boat Type VIIC	A. Ship Information	Page 57

U-boat Information	IV. Armament	10

		2 boxes with 12 demolition slabs each [general purpose explosives in a rectangular metal case with openings to insert the slow match fuse with detonator]
		2 boxes with 12 time fuses each
		Fuse (slow match) with manual ignition and detonator.
		Explosives are stored in a floodable magazine in the control room.

4) Small arms.
		In the boat are stored:
		1 MG 34 machine gun
		2 submachine guns
		6 Mauser pistols 7.65 mm
		3 bayonets 84/98 with body belts and 2 ammunition pouches
		1 flare gun (single barreled)
		1 flare gun (double barreled)
		The ammunition allocation is as follows:
		3000 rounds for submachine guns
		860 rounds for pistols
		180 rounds for flare guns (star signals)
		200 rounds for flare guns (recognition signals)
		Ammunition for small arms is stored in a munitions magazine in the officers room.

Page 58	A. Ship Information	U-Boat Type VIIC

1	V. Communications	U-boat Information

V. Communications.

1) Visual and acoustic equipment.
	a)	Visual equipment:
		Large searchlight and small signal searchlight
		Aldis lamp
		Running lights
		Signal and semaphore flags
		Star signal pistol
		Flares.

		The 24 V searchlight is powered from the transformer located in control room from the TDC converter installed in aft torpedo room.
		Watertight switches and outlets are installed in the conning tower.
		The 24 V signal search light is powered in the same way. The watertight and pressure-resistant outlet is installed on the bridge, one more watertight outlet is installed in the conning tower. Switches for both outlets are located in the conning tower.
		The following running lights are installed: steaming, side and stern lights. These lights are controlled by means of switch located in conning tower. Both stern lights are provided with a dimming-resistor in conning tower with a control switch and indicator lamp.
		To power the steaming light a watertight and pressure-resistant outlet on the bridge and a watertight outlet in the conning tower are provided.
		The flares and flare lighter are stored in a can in the control room.

	b)	Acoustic equipment:
		Tyfone air whistle
		Ship's bell.
		The tyfone air whistle can be operated from conning tower and from the bridge.
		The ship's bell can be mounted on the bridge railing, when diving it was stored inside the boat.

U-Boat Type VIIC	A. Ship Information	Page 59

U-boat Information	V. Communications	2

2) Electronic communications equipment.
	a)	Radio installation.
		The radio installation consists of short and long wave equipment and an auxiliary direction finding receiver.
		The short wave equipment consists of a transmitter (output power 200 W, frequency range 3750-15000 kHz and wavelength 80-20 meters) and a 6-stage receiver (1500-25000 kHz, wavelength 200-12 meters).
		The transmitter consists of three-stages, with continuously variable frequency. The control stage is divided into 10 separate ranges, which are overlapping. The transmitter can be switched into toneless or sounding telegraphy mode.
		The following voltages are needed for operation:
		1500 V DC for powering vacuum tube anodes in the output stage
		400 V DC for powering vacuum tube anodes in the buffer stage and through a voltage divider:
		a) screen grids of vacuum tubes in the buffer stage and,
		b) screen grids of vacuum tubes in the output stage, by which output power control is possible in the range of 2-200 W.
		280 V 100 Hz AC
		a) after previous required transformation for heating the cathodes of tubes in all stages and,
		b) after previous rectification as a cut-off and biasing voltage in the control and output stages (from -110 to 300 V),
		c) for powering the key relay (24 V).
		The receiver is a five-tube, six-stage large ship receiver. The frequency range is divided into 8 separate ranges, which are overlapping. The receiver requires following power supplies:
		a) 200 V DC for powering vacuum tube anodes,
		b) 4 V DC for heating the cathodes of vacuum tubes and,
		c) -1.5 V DC for cut-off voltage for all tubes.
		The long wave equipment consists of a transmitter (output power 150 W, frequency range 300-600 kHz, wavelength 1000-500 meters) and a direction finding receiver used as long wave receiver.

Page 60	A. Ship Information	U-Boat Type VIIC

3	V. Communications	U-boat Information

		(for details see direction finding installation).
		The transmitter consists of two-stages, with continuously variable frequency. Unlike the short wave transmitter, the output stage with antenna circuit is separated in its own case from the main transmitter casing.
		The following voltages are needed for operation:
		1500 V DC for powering vacuum tube anodes in output stage
		400 V DC for powering vacuum tube anodes in control stage and through voltage divider screen grids of vacuum tubes in output stage, by which output power control is possible.
		280 V AC after previous required transformation for heating the cathodes of tubes in all stages and after previous transformation and rectification as a cut-off and biasing voltage in control and output stages.
		Both transmitters can be connected with common control unit by means of a selector switch on the transmitter switchboard. This unit provides a telegraph key, output power control, volume control and operation mode (toneless, sounding telegraphy) selection.

		The direction finding installation is used to obtain relative bearings form radio beacons and in this way to get own location. It consists of a direction finding receiver and pressure-resistant and watertight loop antenna.
		The direction finding receiver has two operational ranges: frequency: 1000-75 kHz, wavelength: 300-4000 meters and frequency: 25-15 kHz, wavelength: 12000-20000 meters. These are divided into 7 separate sub-ranges. Due to their good direction and receiving properties the longest waves (12000-20000 meters) are especially suitable for receiving while submerged.
		The dedicated power supplier supplies following voltages needed for the receiver:
		a) 4 V DC for heating the cathodes of vacuum tubes
		b) 60 V DC for powering the vacuum tube anodes.
		The loop antenna installation consists of the directional loop, rotating shaft, clutch casing, manual drive for rotating the shaft and installation for rising and lowering the antenna. Raising and lowering takes place by means of compressed air, controlled by three-way cock. Rotation of the directional loop is done with a directional wheel in the radio room.

U-Boat Type VIIC	A. Ship Information	Page 61

U-boat Information	V. Communications	4

Broadcast and announcement system:

The system consists of: 1 broadcast radio receiver, 1 record player with amplifier, 10 fixed mounted speakers and 6 microphones.

The broadcast selection switch enables connecting either the radio receiver or the record player to the broadcast system amplifier.

The arrangement of speakers and microphones is as follows:

Aft torpedo room:	Speaker	Microphone
E motor room:	"	"
Diesel engine room:	"
Petty officers room:	"
Control room:	"	"
Conning tower:	"	2 "
Officers room:	"	"
Chief petty officers room:	"
Forward torpedo room:	"	"
Radio room:	Control speaker

The speakers combined with microphones are used for passing orders.

Broadcast radio receiver, record player and amplifier are powered by 220 V AC.

Ultra short wave portable transmitter and receiver:

The device is a portable transmitter and receiver with following operating modes: toneless and sounding telegraphy, telephony and broadcast receiving. It is used for passing orders and communication within visual range.

Transmitter, receiver, accumulator, dry batteries, headphones, telegraph key and telescoping antenna are hosted in an armored wooden case.

The device output power is 0.6 W, frequency range 41.67-45.15 MHz, wavelength 7.2-6.5 meters. This range is divided on the transmitter and receiver scale into 10 channels (9-18).

The accumulator delivers 2 V power for heating the cathodes of transmitter and receiver vacuum tubes, while the dry batteries

Page 62	A. Ship Information	U-Boat Type VIIC

5	V. Communications	U-boat Information

		connected in series deliver 120 V voltage for powering the vacuum tube anodes and about 3 V power for cut-off voltage.
		When operating on the boat, the rod aerial installed on the pennant masthead is used. When operating on land, a telescoping antenna attached to armored wooden case is used.

		Back-up radio equipment.
		In case of damage to the short wave equipment the auxiliary radio in the listening room is provided. It consists of a transmitter (output power 40 W, frequency range 3000-16670 kHz, wavelength 100-18 meters) and an all wave receiver (15-20000 kHz, wavelength 20000-15 meters). The transmitter and receiver are connected to a common control panel.
		The transmitter is designed as two stage, long-range device. The frequency range is divided into three separate sub-ranges. It provides only toneless telegraphy operating mode.
		The dedicated power supply, powered by 220 V AC, supplies following voltages needed by the transmitter:
		390 V DC for powering the anodes of vacuum tubes in the control stage
		600 V '' '' '' '' output stage
		12.6 V AC for heating the cathodes of all vacuum tubes
		110 V and 195 V DC for powering the screen grids of vacuum tubes
		-210 V and 190 V DC as cut-off voltage
		The all wave receiver is a two stage, four vacuum tube device and is dedicated to receiving all types of modulation. The frequency range is divided into 10 sub-ranges.
		The dedicated power supplier supplies following voltages needed by receiver:
		100 V DC for powering the anodes of vacuum tubes
		4 V for heating the cathodes of all vacuum tubes
		-3 and -1.5 V as a cut-off voltage.

	d)	Aerial installation:
		The jumping wires [net deflectors] are used as transmit and receiving aerials. The wires are separated from hull by means of coconut insulators. Two aerial selector panels in the radio room allow plugging in the transmitter or receiver to the forward or aft jumping wires. The aerial feed lines are led in pressure proof and water resistant shafts.

U-Boat Type VIIC	A. Ship Information	Page 63

U-boat Information	V. Communications	6

	e)	Radio - converter installation:
		The installation consists of 1 transmitter converter and 3 receiver converters.
		The transmitter converter provides following voltages:
		1500 V DC 0.3 A, 400 V DC 0.3 A, 280 V AC 1 A.
		The following receiver converters can be used:
		1 6 kVA – converter for powering all receivers, active sonar, passive sonar or
		1 1.5 kVA – converter for powering receiver and passive sonar or
		1 0.3 kVA – converter for powering only two receivers.

	f)	UT [Underwater Telegraphy] installation (sound).
		The UT installation is used to communicate during submerged and surfaced cruise.
		The installation consists of 2 x 2 sound transmitters and 2 x 2 sound receivers, which are located on the port and stb. side, near main ballast tank 5 under the waterline, the UT converter with automatic and manual starter, the switchboard, the amplifier, headphones, and telegraphy key.
		The transmitters and receivers on each side are installed in a pressure-resistant cable box. From there, through pressure-resistant cable trunks, the connecting cables lead into the boat.
		The DC-AC, sound frequency, single phase converter supplies 120 V AC controlled by the telegraphy key, through the switchboard to power the transmitters. Incoming sound waves are passed from the receivers through the amplifier to the headphones.

	g)	G.H.G. [Grupenhorchgerät = Group Listening Apparatus - passive sonar] installation.
		The G.H.G. installation is used to obtain the bearing of surface or submerged vessels.
		The installation consists of 24 sound receivers each on the stb. and port sides, located below the waterline, near main ballast tank 5, each with a pre-amplifier, the power supply, the compensator and

Page 64	A. Ship Information	U-Boat Type VIIC

7	V. Communications	U-boat Information

		the bearing unit with bearing scale. Each set of 8 receivers is connected through pressure-resistant trunks with connection boxes, so that, 6 pressure hull pass-throughs are needed for all 48 receivers. The connecting boxes are located near the hull pass-throughs, directly under the upper deck forward torpedo container. The installation is powered by 220 V AC from the radio receiver converter.

	h)	K.D.B. [Kristalbasisgerät = Crystal Rotating Base Apparatus - passive sonar] equipment.
		The installation has the same function as the G.H.G. It consists of crystal receivers on a rotatable mount, the shaft, the amplifier and bearing scale. The installation is located between the forward torpedo tubes. The shaft passes through the pressure hull forward of the anchor capstan. The rotatable mount rises 40 cm above the upper deck. The installation is powered in the same way as the G.H.G.

3) Power supply for electronic communications equipment.
		The power supply line for the electronic equipment branches from auxiliary switchboard 1 in the E motor room and leads to auxiliary switchboard 1A (radio regulating switchboard) in the E motor room and to the radio switchboard in the radio and the listening rooms.
		From auxiliary switchboard 1 (regulated part) main bus (110 V) a line goes to the radio switchboard 110 V bus. The following installations and equipment are powered from this bus:
		Transmitter switchboard,
		Underwater telegraphy installation,
		Echo depth sounder,
		Auxiliary transmitter and receiver control panel.
		From auxiliary switchboard 1 (unregulated part) main bus a line goes through the auxiliary switchboard 1A to the top bus (110 V) of the radio switchboard. The following devices are connected to this bus:
		6 kVA rotary converter
		1.5 kVA '' ''
		0.3 kVA '' ''
		These 3 converters power the 220 V AC radio switchboard.

U-Boat Type VIIC	A. Ship Information	Page 65

U-boat Information	V. Communications	8

		Bus I, which can be powered only by the 6 kVA converter, branches to the following installations:
		Active sonar
		Auxiliary transmitter
		Underwater telegraphy installation
		All wave receiver
		Preheating of the transmitter switchboard
		Bus II, which can be powered by all three converters, branches to:
		Group Listening Apparatus (G.H.G.)
		Rotating Hydrophone Apparatus (K.D.B.)
		Depth sounder
		Short wave receiver
		Direction finder receiver
		Broadcast receiver with record player
		Sound amplifier
		Coding machine (through transformer 220/4 AC)
		Electrical outlets
		The transmitter switchboard is powered (110 V DC and 220 V AC) from the radio switchboard (see above). By means of the transmitter rotary converter (1.2 kW) the 110 V DC current is converted into 1500 V and 400 V DC and 280 V AC (double armature converter with collector rings). The following devices are powered from the transmitter switchboard:
		Short wave transmitter
		1500 V DC
		400 V DC
		280 V AC
		Long wave transmitter
		1500 V DC
		400 V DC
		280 V AC
		Control unit for short and long wave transmitters
		Output stage for long wave transmitter
		Ultra short wave portable transmitter and receiver are powered by:

Page 66	A. Ship Information	U-Boat Type VIIC

9	V. Communications	U-boat Information

		A 2 V battery is used to heating the cathodes of vacuum tubes, for powering the microphone and for temperature compensation of capacitors. Two 90 V batteries power the tubes, screen grids and for cut-off voltage.

4) Antennas.
		The ship is equipped with following aerial systems:
		Forward jumping wire [net deflector]
		Aft jumping wires.
		All three jumping wires can be used as transmitter and receiver aerials for short and long wave and broadcast radio equipment.
		Rod aerial.
		The rod aerial is used as transmitter aerial for short and long wave equipment when submerged (at periscope depth).
		Loop aerial.
		The loop aerial is used as a receiver aerial for direction finder receiver. (to obtain position of own boats other ships and aircraft)

U-Boat Type VIIC	A. Ship Information	Page 67

U-boat Information	VI. Steering Gear System and Anchor Installation	1

VI. Steering Gear System and Anchor Installation.

1) Steering System.
	a)	General.
		The rudder installation includes the following:
		Two identical main rudder planes parallel to each other,
		Forward dive planes,
		After dive planes,
		Plane drive,
		Steering stations,
		Steering lines.

		Steering plane construction:
		To keep the driving force low, all steering planes are built as displacement, balanced rudders. They are made from watertight plating on both sides, with stiffeners provided between the plates. The spaces between plates are filled with tarred wood.

		Steering plane protection:
		A skeg is provided to protect the main rudder, especially from hitting the bottom, from which two arms lead to both rudders and are attached to the rudder pins. To prevent entanglement with naval mine wires and antisubmarine nets all linkages are made smooth and all faces are rounded.
		The outer edges of dive planes are protected against naval mine wires.
		To avoid corrosion (galvanic current between bronze and steel in sea water) all steering planes are provided with zinc protection plates.

Page 68	A. Ship Information	U-Boat Type VIIC

2	VI. Steering Gear System and Anchor Installation	U-boat Information

	b)	Main rudder installation.
		The main rudder is twin type and can be either electrically or manually driven.

		The main rudder is driven by means of vertical intermediate shaft, which passes through the pressure hull between frames 1 and 2 and which is driven by worm gear. The shaft bearing is installed at the pressure hull and is retightened from inside by a stuffing box.
		To top of the intermediate shaft (in the upper deck) is attached to a double arm, which is connected by means of two long connecting rods with two, center-facing, main rudder arms. Each main rudder has an area of 2.75 m². The rudder maximum deflection is 33° when electrically driven and 35° when manually driven.

Ruderblätter Rudder planes

Fester winkel Fixed angle

Drehpunkt des Ruderblattes Pivot point of rudder planes

Hauptruderhebel Main rudder arm

Schubstange Connecting rod

Senkrechte Zwischenwelle Vertical intermediate shaft

Doppelhebel Double arm

U-Boat Type VIIC
A. Ship Information
Page 69

U-boat Information
VI. Steering Gear System and Anchor Installation
           3

The maximum deflection of the main rudder and forward and aft dive planes is limited electrically by means of a limit switch and mechanically by means of mechanical limit stop.

c) Dive planes installation.

The forward and aft dive planes are mounted on common shafts. The maximum deflection of the forward planes is 30° up and 30° down, for the aft planes 25° up and 35° down. The spindle driven by an electric motor moves the pushing rod either in or out and through the connection with the rudder shaft lever deflects the dive planes. The aft dive planes each have an area of 2.25 m², each of the the forward dive planes area is 2.40 m².

2) Anchor installation.

The anchor installation consists of:

        Anchor, anchor chain,

        Chain stopper, chain tripping device,

        Anchor windlass and capstan.

The boat is fitted with Hall stockless type anchor and chain of length 150 meters. The anchor weight is 400 kg and chain weight is 1676 kg. The chain consists of 6 parts each 25 meters long connected by means of shackles.

Motor mit Getriebe Electric motor with gear box

Drucklager Thrust bearing

Kupplung Clutch

Führungsstange mit Gewinde Threaded guide rod

Stopfbuchsen Stuffing boxes

Kreuzkopf Limit slider

Druckkorper Pressure hull

Lenkstange Pushing rod

Ruderwelle mit Hebel Rudder shaft with lever

Page 70
A. Ship Information
U-Boat Type VIIC

4
VI. Steering Gear System and Anchor Installation
U-boat Information

To keep the anchor chain still when anchor windlass is not driven, a chain stopper is installed at the upper deck, which is operated from inside the boat by means of linkage and a handle.

The anchor chain locker is located within main ballast tank 5.

The capstan raises the lowered anchor at a speed of 10 meters/minute and heaves the chain at a speed of 20 meters/minute. The output power of the compressed-air motor is 19 Hp at 740 RPM and 3.5 at. The motor can be operated and reversed from the forecastle and from inside the boat. The capstan is driven by a compressed-air motor through double-cone worm gear. After double-cone worm gear and horizontal intermediate shaft the drive branches to the anchor windlass. Moreover, manual drive is possible by means of a removable capstan head.

The length of expended anchor chain is observed by means of an indicating device from inside the boat as well as from the upper deck.

U-Boat Type VIIC	A. Ship Information	Page 71

U-boat Information	VII. Equipment and Installations for Navigation	1

VII. Equipment and Installations for Navigation.

1) Ship control.
	As the ship control station are used:
		The bridge
		Conning tower
		Control room
		The following installations are available:
		Main rudder control station on the bridge, in the conning tower and in the control room,
		Dive planes control station in the control room,
		Engine order telegraph in the conning tower and in the control room,
		Gyro-compass repeater on the bridge (pressure-proof), in the conning tower and in the control room,
		Main rudder angle indicator on the bridge (pressure-proof), in the conning tower and in the control room,
		Alarm bell activating switches in the conning tower and control room,
		Periscopes in the conning tower and in the control room,
		Auxiliary main rudder control station in the E motor room (manual drive) with mechanical main rudder angle indicator.

2) Periscopes.
	The boat is equipped with two periscopes.
	a)	Attack periscope (PH. Frame 44).
		The aft periscope has its upper part tapered as much as possible (has low light transmission) and is used mainly during day attack.
		It is constructed as a fixed-eye-level periscope and so offers the advantage of fixed height of viewing during lowering and rising of the scope. The scope is operated in the conning tower. The periscope is lead out through the deck covering the conning tower by means of a guide bushing and to avoid vibrations it is supported by the periscope stand on the bridge.
		The periscope well extends from the lower part of the pressure hull to the level above the conning tower deck. Inside main ballast tank 3 the well is pressure-proof and

Page 72	A. Ship Information	U-Boat Type VIIC

2	VII. Equipment and Installations for Navigation	U-boat Information

		can be accessed for inspection purposes (removing the prism box) from the control room through the pressure-proof man hole in the control room deck.

	b)	Air search periscope (PH. Frame 47-1/2).
		The forward periscope has greater light transmission (thicker tube) and is mainly used during night attacks.
		It is operated from the control room and is lead out in front of the conning tower. The scope is guided in a bushing and at the level of conning tower covering plate by a support stand to avoid vibration. On the bridge the scope is surrounded by a light protective cover which is bolted to the conning tower casing and provided with flooding holes.
		The well of the forward periscope extends from a level 500 mm above the lower part of pressure hull in main ballast tank 3 to a level 600 mm above control room deck. The well is constructed as pressure-proof.
		For scopes details see classified periscope manuals.

	c)	Periscope drive.
		Both periscopes are driven hydraulically. Hydraulic oil is used as a pressurized hydraulic fluid. The electrically driven screw pump (main or auxiliary) pressurizes oil from the collecting tank into three steel flasks of capacity 125 liters each. A connection from high pressure air installation to each flask is used to create the required pressure and air cushion. From the flasks the oil under a working pressure of 80-45 kg/cm² is supplied to the screw motors, where the energy of pressured oil is transformed into movement. Each periscope has its own screw motor used for raising and lowering. Moreover, the attack periscope is provided with one additional motor (with smaller output power) for rotating the scope.
		The oil pumps are automatically turned on and off when the marginal pressure is reached (45 and 80 kg/cm²) by means of pressure control switches.
		The hydraulic motors are turned on and off and reversed by means of control valves.

U-Boat Type VIIC	A. Ship Information	Page 73

U-boat Information	VII. Equipment and Installations for Navigation	3

		Each periscope is provided with an automatic limit switch, which turns off the motor at the end positions.

3) Compass installation.
		The compass installation consists of:
		a) Gyro compass (Anschutz type)
		b) Projector compass (Askania type)
		In case of damage to the gyro compass the projector compass is used for navigation.

	a)	Gyro compass installation.
		The gyro compass installation consists of the gyro compass (in the control room) and seven gyro repeaters.
		The repeaters are located as follows:
		1 in the control room,
		1 in the conning tower,
		2 on the bridge (one with bearing telescope),
		1 in the radio room,
		1 wall repeater in the control room near the active sonar equipment,
		1 in the listening room.
		Both repeaters on the bridge are pressure-proof. The repeater in the control room can be moved to the auxiliary main rudder control station in the aft torpedo room.
		The currents and voltages required for driving the gyro compass are supplied by the gyro compass rotary converter (Anschütz type) located in the E motor room. This converter can be powered through the selector switch by the port or starboard auxiliary switchboard.
		Operating principle of gyro compass:
		When the ship changes its course, the outer - follow-up - sphere in its floating mounting rotates the same angle. Due to gyroscopic effect (gyro keeps always its main axis parallel to the meridian plane) the inner - gyro - sphere is always set to the north-south line.

Page 74	A. Ship Information	U-Boat Type VIIC

4	VII. Equipment and Installations for Navigation	U-boat Information

		Thus there occurs a difference in the liquid path resistance, which affects the current, which - amplified - powers the follow-up motor. This motor is coupled by means of gear drive with servo transmitter, which transmits the movement to the servo receivers (azimuth motor and repeaters) with 1/16 deg accuracy.
		The azimuth motor of the gyro compass rotates the follow-up sphere by means of a gear drive as long as the servo transmitter is rotated by follow-up motor. When the follow-up sphere is rotated to a position, in which the liquid path resistance is equal - that is at the same angle as the course change - the follow-up motor stops. The motors of the repeaters behave exactly as the azimuth motor and turn their compass roses at the same angle as the azimuth motor turns the follow-up sphere.

	b)	Projector compass installation.
		The projector compass is installed forward of the conning tower in a pressure-proof casing together with the compass rose illumination and optics system which projects the view of the rose to the control room. To eliminate the influence of electric currents to the magnetic compass, non-magnetic materials are used within a radius of 900 mm from the compass center.
		The desiccator of the periscopes can be used to dry out the optical projection system or the compass casing.

4) Signal equipment.
	Signal equipment consists of the following:
	a)	Running lights.
		Stern light (stern)
		Stern light (conning tower)
		Sidelights (port and stb.)
		Steaming light
		All around light

U-Boat Type VIIC	A. Ship Information	Page 75

U-boat Information	VII. Equipment and Installations for Navigation	5

Searchlight equipment.

24 Volt signal search light

24 Volt searchlight

For details see section V.1.

5) Depth sounding equipment.

The boat is equipped with the following depth sounding equipment.

1. Echolot [echo sounder]

2. Elektrolot [explosive echo sounder]

3. Hand lead

The Echolot device can be used also during submerged cruise.

Echolot.

The Echolot consists of a shallow and a deep depth device. Measurement of water depth performed by both devices is based on determination of the elapsed time of the sound from the ship to sea bottom and back. The product of the elapsed time and sound velocity in sea water gives the length of the sound path. Half of this length is the water depth.

The sounding device has three measurement ranges:

1. 0-125 meters	shallow/supersonic sounding device
2. 0-1000 meters	shallow/supersonic sounding device
3. 150-3000 meters	deep/sonic sounding device

The shallow and deep depth devices work totally independently, though measured depth is displayed on the same common depth indicator located in control room. By means of an arm switch the depth indicator can be connected either with the shallow or deep depth sounding device. By means of the scale switch the shallow and deep depth devices can be connected simultaneously.

Each device consists of: transmitter, receiver and amplifier. The shallow depth sounding device works noiselessly, while the deep depth device sends sound impulses which are audible. Both devices are powered by the AC shallow and deep depth echo sounding converter located in the E-motor room.

Page 76	A. Ship Information	U-Boat Type VIIC

6	VII. Equipment and Installations for Navigation	U-boat Information

		The deep depth sounding device has three transmitters and three receivers which are mounted in the keel. The shallow depth sounding device has one transmitter and one receiver. Both are mounted on bottom of the hull, on the port side, near the munitions magazine.

	b)	Elektrolot.
		In this method, an explosive charge is thrown into the sea and when it breaks the water surface, a stopwatch is started. When the device reaches the sea bottom (the sound of explosion returns) – the timer is stopped (rate of sinking is 2 meters/second).

	c)	Hand lead.
		The hand lead consists of sounding line and plummet. The line is 50 meters long and is provided with marks spaced at 2 meters for reading the depth.

6) Log installation.
		The speed is obtained by measuring the pressure difference between static and dynamic pressure. The dynamic pressure is obtained from nozzles located on the port and starboard sides of the bow.
		The static pressure is obtained from nozzles located on port and stb. side of main ballast tank 3. Each nozzle is connected by means of pipes with the master unit installed in the control room. The speed can be read on master unit in the control room or on a repeater in the conning tower, to which the speed is electrically transmitted. In the conning tower a distance counter is also provided.
		The installation consists of:
		piping with control manifold
		master unit (transmitter)
		repeater (receiver)
		distance counter
		The control manifold and master unit are installed in the control room. Transmitting the height of the quicksilver column takes place by means of a magnetic clutch. The indicator axis is coupled by variable resistance to transmit the indicator position to the log repeater and to the integrator of the distance counter.

U-Boat Type VIIC	A. Ship Information	Page 77

U-boat Information	VII. Equipment and Installations for Navigation	7

		The repeater is installed in conning tower. The coil of the indicator is powered by 24 V current, taken from the light circuit through the voltage divider. The speed is shown by means of rotating indicator on a linear 270° arc scale.
		The distance counter is installed in the conning tower. The device has two mechanical counters, on which the upper one shows the traveled distance. The counter is resettable. The second counter can be set to a desired distance. The optical indicator signals when that distance is traveled. The distance counter is powered by 110 V current.

7) Alarm installation.
		The alarm installation is used to tell the crew to take their diving stations as quickly as possible.
		The installation is powered by 110 V DC from either starboard or port light group. The power line branches from auxiliary switchboard in the E motor room and in the control room and through fuse boxes leads to the control panel in the control room, and to alarm bells and both flashing circuits in the diesel engine room. The flashing circuits are connected with the port and starboard lights circuits of the diesel engine room and control 5 lamps in the starboard and 7 lamps in the port circuit respectively.
		Alarm bells are located as follows:
		1. in the E motor room,
		2. in the petty officers room,
		3. in the diesel engine room,
		4. in the control room,
		5. in the chief petty officers room,
		6. in the forward torpedo room.
		The alarm can be activated from the control room or from the conning tower by means of a two-pole switch. When the switch is on, the alarm circuit is energized. Alarm bells start to ring and flashing circuits switch the lamps in the diesel engine room on and off at short intervals.

Page 78	A. Ship Information	U-Boat Type VIIC

8	VII. Equipment and Installations for Navigation	U-boat Information

8) Ordering and reporting installations.
		The electric ordering and reporting installation and indicating installation consists of:
		1. Engine order telegraph system,
		2. Rudder order telegraph and rudder angle indicator system,
		3. Alarm installation,
		4. Compartment ready indicating system,
		5. Hull closure indicating system,
		6. Broadcast and announcement system (see paragraph V b).
		For details of electric ordering and reporting installation see paragraph B IX 5c.

		Voice tubes are installed for passing verbal orders between rooms.
		Connecting bridge and conning tower with:
		E motor room,
		Control room (branches to diving officer station and to main rudder control station),
		Radio and listening rooms,
		Commanding Officer's room.
		Also connecting conning tower with:
		Aft torpedo room,
		Forward torpedo room.
		By means of a bi-directional whistle system the control room and conning tower can be called from the aft and forward torpedo rooms.
		Each voice tube has several bulkhead valves installed, which enable isolating pressure-proof compartments from each other in case of water intake.

U-Boat Type VIIC	A. Ship Information	Page 79

U-boat Information	VIII. Safety and Rescue Installation	1

VIII. Safety and Rescue Installations.

1) Installations for submerged and surfaced boat.

Emergency lighting.

The emergency lighting should, in case of damage to the main lighting, point the way to emergency exits and illuminate the rooms.

For that reason there are 8 automatically switched on battery powered emergency lamps, 9 mountings for battery powered hand lamps and 8 battery powered hand lamps located as follows:


Room Plan	Battery Powered Emergency Lamp		Room Plan	Battery Powered Hand Lamp - Mounting
	No.	PH. Frame		No.	PH. Frame

E motor room	1	16-1/2	Aft torpedo room	1	At the torpedo tube
		(Bulkhead)
Diesel engine room	1	29	E motor room	1	16-1/2
		(Bulkhead)			(Bulkhead stb.)
Galley	1	29	Diesel engine room	1	29
		(Bulkhead)			(Bulkhead)
Petty officers room	1	39	Galley	1	29
		(Bulkhead)			(Bulkhead)
Control room	1	Periscope shaft port	Control room	1	Periscope shaft aft
Conning tower	1	Air shaft port	Control room	1	48
					Illumination of the depth meter
Officer and chief petty officers' room	1	50-1/2	Conning tower	1	To starboard
		(Spherical bulkhead)
Forward torpedo room	1	63	Officer and chief petty officers' room	1	50-1/2
		(Bulkhead)			(Spherical bulkhead)
			Forward torpedo room	1	69-70 port

Both types of lamps have as a power source battery type M 4/1 with output voltage of 4 V, capacity of 10.5 Ah at 0.75 A current load. The switching circuit of the battery powered emergency lamps

Page 80	A. Ship Information	U-Boat Type VIIC

2	VIII. Safety and Rescue Installations	U-boat Information

		consists of 2 relays, one connected to the starboard, the other connected to the port light circuit, so that in case of damage to both light circuits, the lamps will be automatically switched on.

	b)	Hand lamps.
		Each boat is equipped with 8 battery powered hand lamps, whose location is shown in the preceding table. To help with location, the power switch of each lamp is surrounded by a ring covered with luminous paint.
		Also, each crew member has a pocket lamp.

	c)	Fire extinguishers.
		There are 4 fire extinguishers provided as follows:
		In the E motor room 1 dry extinguisher
		In the diesel engine room 1 foam extinguisher
		In the control room (near the auxiliary switchboard) 1 dry extinguisher
		In the officers room (near radio and listening room) 1 dry extinguisher.
		The fire extinguishing installation is connected to the auxiliary drain and trim pump manifold and consists of a flexible hose connection and stop valve. There is a branch leading through a hull valve to the upper deck. At the upper deck, the piping is led in the upper deck casing parallel to the pressure hull. There are three connections for hoses with stop valves – in the aft part of the upper deck, in the middle (conning tower casing) and the forward part.

	d)	Flooding installation. See section B III.

	e)	Drainage installation. See section B III.

	f)	UT and G.H.G. installation.
		The UT installation is used for communication during submerged cruise between two boats or between the boat and a surface vessel. The transmitters and receivers are installed on the bow part of hull. The UT rotary converter and UT control unit are located in active sonar room, the G.H.G. rotary converter is located in E motor room.

U-Boat Type VIIC	A. Ship Information	Page 81

U-boat Information	VIII. Safety and Rescue Installations	3

		The G.H.G. installation is used to listen to propeller noises, torpedoes etc. during submerged and surfaced cruise. 6 sound receivers are located on each side of bow. [Note: the number 6 is apparently an error - there were actually 24 receivers on each side of the bow for the G.H.G.]

	g)	Emergency steering gear.
		Manual emergency steering gear is provided for the main rudder located in the aft torpedo room. This steering station is equipped with mechanical main rudder angle indicator, 1 rudder order telegraph receiver with ordered angle indicator and 1 call bell.

	h)	Diving suit.
		2 full diving suits, 1 simple diving suit with oxygen flask, without helmet, 1 set of weight chains, 1 pair of weighted shoes are provided.

	i)	Emergency escape gear.
		See paragraph A VIII 3 h.

	k)	Life rafts.
		2 Life rafts with buoys.
		To store the life rafts with buoys, 2 pressure-proof containers are provided on the upper deck, together with installation for flooding, venting and opening, which is operated from inside the boat.

	l)	Damage control materials.
		See paragraph A IX 3 c.

2) Installations for surfaced boat.
	a)	Battery ventilation.
		The ventilation installation of the battery rooms should prevent accumulation of explosive gases, which are formed when the batteries are charged. In all parts of the battery ventilation system there should be a rarefaction of the gases by fresh air at least 20 times by the end stage of charging with 415 A current.

Page 82	A. Ship Information	U-Boat Type VIIC

4	VIII. Safety and Rescue Installations	U-boat Information

		The extractor pipe under battery room deck is connected with main exhaust trunk by means of an extractor duct. A stop valve is installed in the extractor duct at the point of passage through the battery room deck and is bent upward just before connection with main exhaust trunk.
		Over the battery a grid of suction pipes is installed, which is connected to each battery cell by means of glass bend and rubber pipe. The single suction pipes are fastened to cell poles by means of insulated brackets and are connected to the extractor pipe, which in turn is connected with main exhaust trunk.
		At the joint with extractor pipe each suction pipe has an adjustable, ebonite orifice plate installed, which enables a balanced flow rate to be maintained.
		To check the amount of suction, pressure indicating devices connected at the blank end of each extractor pipe, which are installed over the battery room deck. They show the pressure difference between the suction pipes and battery room. Also, at the end of each extractor pipe, at the lowest point, a tank is installed, which is dedicated for acid carried away by the air flow.

	b)	Emergency vent valves.
		The following main ballast tanks and main ballast and reserve fuel oil tanks are equipped with emergency vent valves:
		Main ballast tank 3 port and stb.,
		Main ballast and reserve fuel oil tank 2 port and stb.,
		Main ballast and reserve fuel oil tank 4 port and stb.
		The emergency vent valves for main ballast tank 3 port and starboard are located at the point where the vent trunks pass through the pressure hull. The vents for main ballast and reserve fuel oil tank 2 and 4 port and starboard are located where the vent trunks pass through the outer hull plating.

U-Boat Type VIIC	A. Ship Information	Page 83

U-boat Information	VIII. Safety and Rescue Installations	5

		The emergency vent valves are operated manually from inside the pressure hull. The operating handles are sealed in the open position and are closed in case of damage to the vent trunks or vent valves or after filling main ballast and reserve fuel oil tank 2 and 4 with fuel oil.

	c)	Coaming.
		In case of flooding the boat, to keep enough air space, coamings extending downward from the hatches are provided with additional extensible downward plates. These movable extensions are pushed up during surface cruise and secured in that position. During submerged cruise, the plates are lowered.
		For the same purpose, the lower conning tower hatch coaming is extended downward to the level about 1650 mm above control room deck by means of a 3 mm thick skirt.

	d)	Life buoy, night signal buoy and dinghy.
		There are three horseshoe-shaped life buoys, two of them are kept handy during surfaced cruise on the sides of the conning tower casing. During submerged cruise they are stored together with two night signal buoys. The dinghy is stored at the forward part of upper deck, on port side, near the torpedo container and is attached by means of lashings.

	e)	Life jackets.
		There are 40 life jackets on board. They are stored in each crew accommodation room near the escape hatches.

	f)	Railing and tethers.
		The railing is installed on the upper deck on both sides and leads from the bow to the stern. The railing pennants are mounted in railing supports by means of clamping bolts. Demounted railing can be stowed in the upper deck casing.

Page 84	A. Ship Information	U-Boat Type VIIC

6	VIII. Safety and Rescue Installations	U-boat Information

		There are 10 tethers and safety belts provided for use by the crew operating the deck gun and the bridge watch while cruising in stormy seas.

	g)	Recognition marks for aircraft.
		Each boat is equipped with recognition marks for aircraft, which are unfolded on the upper deck, forward of the deck gun.

3) Installations for submerged boat.
	a)	Compartmentation.
		The pressure hull is divided by means of two spherical bulkheads into three pressure-proof compartments and by means of another three watertight bulkheads into 6 rooms.
		See paragraph A II 3.

	b)	Air purification system.
		The air purification system consists of:
		Purification system: removing CO₂ by means of sodium hydroxide cartridges
		Renewal system: bleeding O₂ from oxygen flasks.
		A man when breathing, creates 30 liters/hour of CO₂ and needs the same amount of O₂. The air purification system maintains the CO₂ content at 1.5% level and O₂ content at 17.5%.
		CO₂ content above 2% is injurious.
		The estimation of time, when 1.5% CO₂ content in 400 m³ of air in the boat will be reached:
		37 men creates per hour: 37 x 30 x 100/400000 = 0.28% CO₂ / hour
		So 1.5% CO₂ content will be reached after 5 hours 20 minutes.
		The measurement of CO₂ and O₂ concentration is made by means of Orsat devices, first time after 4 hours of submerged cruise. Moreover there are CO₂ sampling tubes to detect carbon dioxide content above 1.5%.

		Air purification
		3 air purifiers are used for air purification connected to exhaust air duct, located as follows:
		In the aft torpedo and E motor room
		In the control room
		In the forward torpedo room
		Each air purifier consists of 4 sodium hydroxide cartridges.

U-Boat Type VIIC	A. Ship Information	Page 85

U-boat Information	VIII. Safety and Rescue Installations	7

The air from the compartment is withdrawn through an air exhaust duct through the air purifier and purified air is returned by an air intake duct. The regulating valve allows adjustment of the amount of air passing through the purifier. When adjusting, the amount of passing air should be kept as low as possible to avoid warming the cartridges, because in this case, the cartridges don't reach their full efficiency. Ventilation capacity is:

In the 1st hour – 350 liters/hour

In the 2nd hour – 400 liters/hour

In the 3rd hour – 450 liters/hour

Air renewal

Air renewal takes place, when the oxygen content drops below 17.5%. 10 oxygen flasks are provided, with capacity 50 liters each at a pressure of 150 at. These flasks are located as follows:

E motor room	1 flask
Diesel engine room	2 flasks
Control room	4 flasks
Forward torpedo room	3 flasks

The main manifold, to which all flasks are connected, has a branch from the control room to the upper deck, which is used for filling the flasks with oxygen. Oxygen can be supplied through connecting pipes to the air exhaust duct and added to circulating air or bled directly into the compartments of the boat.

Regulating valves installed in the connecting ducts and in the end of branch leading to the conning tower, which allow adjusting the oxygen feed rate depending on crew numbers.

The stored oxygen and sodium hydroxide cartridges enable the crew of 37 men, to remain continuously submerged for 72 hours.

Page 86	A. Ship Information	U-Boat Type VIIC

8	VIII. Safety and Rescue Installations	U-boat Information

	c)	Compressed air and emergency blowing manifold.
		The compressed air reserve is 3900 liters at 205 at. For details see paragraph A III 4.
		To blow the main ballast tanks and the main ballast and reserve fuel oil tanks from a rescue vessel, there are branches from both emergency air supply lines, between the screw joint and straight-way valve, which each lead through the straight-way valve to the common line and then to the emergency blowing manifold located in the conning tower casing. Its location is marked with a red mark.


		Just before the connection with the manifold, a check-valve is installed. By means of 8 straight-way manifold valves all main ballast tanks and main ballast and reserve fuel oil tanks can be blown. From two emergency manifold valves the lines lead through the hull valves to main ballast tank 1 and main ballast tank 5 blowing lines. These hull valves can be operated from the inside the boat as well as from the upper deck. The valves are normally sealed.
		The emergency blowing lines of the other tanks lead from the emergency blowing manifold through the straight-way valves to the respective exhaust gases blowing lines.
		The emergency blowing manifold valves in the conning tower casing are located according to order of the the ballast tanks and have enlarged handles for ease of operation by divers.

	d)	Emergency air supply system.
		To ventilate the sunken boat from a rescue vessel by means of pressure-proof, armored hose, the following emergency air supply and emergency air exhaust connections are provided:
		In the aft torpedo room over the air compressor
		In the control room on the port, foreside of the periscope well
		In the forward torpedo room near rear part of torpedo tubes
		In the conning tower (air supply only) at the conning tower deck
		The emergency air supply system in the aft and forward torpedo rooms consists of screw joints and hull valves operated from inside the boat.

U-Boat Type VIIC	A. Ship Information	Page 87

U-boat Information	VIII. Safety and Rescue Installations	9

		The emergency air supply system in control room consists of screw joints and valves, which are operated from the upper deck. Inside the boat in the air supply and exhaust lines hull and three-way valves installed. By means of a three-way valve either the control room or the conning tower can be ventilated.
		The emergency air supply to the conning tower consists of external screw joint and internal valve, which is operated from inside the boat. The location of all connections at the upper deck is marked with a circle sign:


	e)	Rafts.
		See paragraph A VIII 1 k.

	f)	Air trap.
		For the watertight bulkheads between:
		E motor room and Diesel engine room,
		Diesel engine room and petty officers room,
		Officers and chief petty officers room and forward torpedo room.
		The area above the upper edge of bulkhead doors serves as an air trap. Other air traps are made by the coamings of the galley hatch, control room hatch and conning tower hatch.

	g)	Emergency escape gear.
		39 sets of emergency escape gear are provided for the crew on board, and another 20 sets as reserve - total number: 59 sets. The escape gear is so located, that during submerged cruise, in case of emergency, there is a sufficient number of sets in each compartment for each crew member at their diving stations.
		Also, two full diving suits (one with and one without weights) and 40 life jackets are provided on board.

Page 88	A. Ship Information	U-Boat Type VIIC

10	VIII. Safety and Rescue Installations	U-boat Information

	h)	Net deflector.
		Over the entire length of the boat, from bow to the stern, a jumping wire is stretched and attached to the bridge bulwark in such way, that underwater nets are moved over the wire and do not catch on the bridge bulwark. From the conning tower to the bow there is a single wire, from stern to the conning tower a double jumping wire is installed. During torpedo loading the jumping wire can be demounted by means of tensioning screws. Because the jumping wire is used as an aerial, it is isolated from the boat hull by means of a chain of three coconut porcelain insulators fitted at each end.

	i)	Net cutter.
		At the stem, under the standard waterline there is a fixed, while at stern a detachable net cutter is installed. The net cutter at stem is protected by a cover made of 4 mm thick plate. The cover at its lower part is formed in tongue shape, which slides in the pocket in the stem, while at upper part it is mounted to the stem by means of bolts. Thus the cover can be removed without placing the boat in the dry dock.

	k)	Compartment ready indicating system.
		See paragraph B IX 5 c(7).

	l)	Hull closure indicating system.
		See paragraph B IX 5 c(8).

	m)	Vent valve indicating system.
		Not installed.

U-Boat Type VIIC	A. Ship Information	Page 89

U-boat Information	IX. Damage Control	1

IX. Damage Control.

1) General.
	a)	Damage control parties.
		To increase the safety of the boat, hull, electrical and machinery parties are formed. These parties have following tasks:
		Removing leaks due to enemy action
		Removing damage to machinery and electrical installations due to enemy action
		Passing orders through the boat
		Reducing noise during approach and evasion and thereby improving depth keeping, which is especially demanding in the presence of the enemy.

		Damage control parties are formed from off duty crew members and are divided as follows:


Party	Post	Petty Officers	Ratings

Hull Party I	E motor room	1 career track II	1 career track VII T
			1 career track II

Hull Party II	Petty officers room	1 career track I	1 career track III

Hull Party III	Forward torpedo room	1 career track VII T	1 career track VII T
			1 career track II
			1 career track I

Machinery-Party	Diesel engine room		2 career track II

Electrical-Party I	Petty officers room		1 career track II

Electrical-Party II	Officers room	1 career track II	1 career track II

Career track (Laufbahn)

Specialty

Career track

Specialty

I
Seaman
VIII
Unused

II
Machinist (Engine room personnel)
IX
Administrative

III
Helmsman/Navigation
X
Clerical

IV
Radio operator
XI
Medical

V
Carpenter
XIII
Musician

VI
Ordnance
XIV
Coastal Artillery

VII
Mechanic (Artificers/Torpedomen)
XV
Motor Transport

Page 90
A. Ship Information
U-Boat Type VIIC

             2

IX. Damage Control

U-boat Information

The party leader is always the most senior ranking crew member in the party.

The hull, mechanical and electrical parties have to take action immediately after damage occurs. If necessary, the member of parties located near the damage must assist as far as possible. The damage control equipment and tools for the mechanical and electrical parties are kept at hand for immediate use.

b) Boat's compensation.

The boat is so designed, that when with standard load (main ballast and reserve fuel oil tanks filled with water) and empty regulating and reserve fuel oil tanks, regulating tanks and negative tanks, at sea water of density = 1.003 it has 0 tons of buoyancy. [see note below]

The excess buoyancy which - when with main ballast and reserve fuel oil tanks 2 and 4 (49.6 m³ of oil + 0.223 m³ of air in pressure proof parts of vent pipes) filled with fuel oil of density = 0.87- is 6.28 tons, is compensated by loading on board additional supplies:

        2.11 tons of lubricating oil

        1.61 tons of provisions

        1.77 tons of fresh water

        1.33 tons of water in regulating tanks (or additional wash water in torpedo compensating tanks 1 and 2).

For both trim conditions the following loads are provided:

Supply

Trim Condition A

Trim Condition B

Remarks

Normal load capacity

Maximum load capacity

35 Days

56 Days

Fuel Oil (density = 0.87)

(including fuel oil gravity tank)
m³

tons

m³

tons

a) regulating/RFO tanks empty (Baltic)
71.43

62.14

121.03

105.30

at sea water density < 1.014

b) regulating/RFO tanks full (North Sea)
80.83

70.32

130.43

113.47

at sea water density > 1.014

Lubricating oil

5.00

7.11

Provisions

2.68

4.29

Fresh and wash water

2.72

4.50

     In wartime conditions maximum load capacity is always taken.

Note: The average density of seawater at the ocean surface is 1.025 grams/ml. Seawater is denser than both fresh water and pure water (density 1.0 grams/ml at 4 °C (39 °F)) because dissolved salts add mass without contributing significantly to volume. Sea water density varies with salinity and temperature from about 1.020 - 1.030 grams/ml.

The water density 1.003 cited above (at which the boat would have 0 buoyancy) is very low and would never be encountered by the boat while it was operating in sea water.

The density of sea water in the Baltic is significantly lower (as low as 1.005 at salinity 7.5%) due to fresh water from rivers than in the North sea (1.025 at salinity 35%).

U-boat Type VIIC
A. Ship Information
Page 91

U-boat Information
IX. Damage Control
            3

c) Reserve buoyancy.

As is written above, when surfaced , at sea water density = 1.003, with empty regulating tanks and regulating and reserve fuel oil tanks, buoyancy is created by air contained in main ballast tanks and main ballast and reserve fuel oil tanks. When sea water density is greater, it is necessary to fill regulating tanks accordingly.

The reserve buoyancy in:

Trim Condition A (main ballast tanks and main ballast and reserve fuel oil tanks empty, standard load)

Va = 154.95          ≈ 155 m³

Trim Condition B (main ballast tanks and main ballast and reserve fuel oil tanks filled with fuel oil, increased load)

Vb = 154.95 – 49.6             ≈ 105 m³

Reserve buoyancy with increased load is also maintained when the largest room, the Diesel engine room (volume 88 m³), is flooded by water. Moreover, the watertight bulkheads allow for isolation and localization of the leakage (at pressure up to 1 meter over upper edge of pressure hull) in the affected room. However the trim change when end rooms are fully flooded is so large, that if any counter ballasting action is taken, the boat slants forward or aft respectively, and total loss of the boat occurs.

For details see the next section.

Remarks: It should be noted, that when pressure inside the boat increases, the depth gauge not longer shows the real depth, but a lesser value, relative to the pressure difference between water pressure and air pressure inside the boat. That's why the depth should be also controlled by means of the Papenberg column, periscope or conning tower flood valve.

2) Weights and trim adjustment with water flooding.

Possible causes: influence of enemy weapon, ramming, explosions and spontaneous combustion on board, material defects and operating errors.

Page 92	A. Ship Information	U-Boat Type VIIC

4	IX. Damage Control	U-boat Information

	a)	Leakage into external tanks with the boat surfaced (Table 1).
		Leaks into external tanks are not dangerous for the boat. The reserve buoyancy in each case gives enough displacement, which also is not affected by trim change. In the case of flooding all external main ballast tanks, and main ballast and reserve fuel oil tanks, including regulating tanks, regulating and reserve fuel oil tanks, and negative buoyancy tanks, the pressure-proof main ballast tank 3 gives enough displacement of 47.00 m³ with level immersion.
		The buoyancy when external tanks are flooded is (values are rounded, regulating tanks, regulating and reserve fuel oil tanks, and negative tanks are half full):


Leak	Capacity	Remaining buoyancy in m³
	m³	Trim Condition A	Trim Condition B

Main ballast tank 1	32	123	73
Main ballast tank 5	25	130	80
Main ballast/RFO tank 2 port and stb.	11	144	105++
Main ballast/RFO tank 4 port and stb.	13	142	105++
Regulating tank 2 port and stb.	4	151+	101+
Regulating/RFO tank 1 port and stb.	3	152+	105+
Negative buoyancy tank port and stb.	1	154+	104+

+) Calculated half full of water
++) Calculated full of fuel oil

		Limitations to diving characteristics can generally be avoided because of the spatial arrangement of venting and flooding installations. However seaworthiness, in certain circumstances, can be strongly affected by heeling and trim changes (i.e. the flooding of main ballast tank 5 lowers the bow of the boat up to 61 cm). These changes can be fixed by counter ballasting.

U-Boat Type VIIC	A. Ship Information	Page 93

U-boat Information	IX. Damage Control	5

Table 1:

Counter ballasting for leaks in external tanks.


Leak				Measure		Final State

Tank	Capacity	Trim or heel		Counter ballasting	Intake	Remaining buoyancy tons	Trim Status
	m³	Trim or heel		Counter ballasting	m³	Remaining buoyancy tons	Trim Status

MBT 5	25	Trim condition A	aft: -37 cm	MBT 1	32	97	Bow moves
			mid: +12 cm				40 cm higher
			fwd: +61 cm				21 cm//deeper

		B	aft: -56 cm	MBT 1	32	48	Bow moves
			mid: +14 cm				45 cm higher
			fwd: +84 cm				39 cm //deeper

MB/RFOT 2 stb.	11	Trim condition A	2.7° stb.	MB/RFOT 4 port	13	130	0° Boat leveled, slightly deeper

MB/RFOT 4 stb.	13	A	3° stb.	MB/RFOT 2 port	11	130	0° Boat leveled, slightly deeper

MBT/RFOT 2 and 4, R 1, R/RFOT 2 stb.	31	A	9° stb.	MB/RFOT 2 and 4 port	24	99	~ 0°
							20 cm //deeper

With a leak in MBT 1 port tanks, the measurements are analogous.

= Flood

	b)	Leakage into pressure hull with the boat surfaced (Table 2).
		Small leaks (see paragraph 3 d) can be removed by means of the main drain pump. However larger leaks in the end rooms lead, when any counter ballasting is taken, to a trim moment, which despite sufficient buoyancy, tilt the boat forward or aft. The free water surface effect also increases this danger. Without counter ballasting or draining, the boat is floatable only when:
		In trim condition A the following rooms are fully flooded:
		petty officers room,
		or the control room,
		or the officer and chief petty officers room,
		or main ballast tank 3.
		In trim condition B the following rooms are fully flooded:
		control room,
		or main ballast tank 3,
		possibly the petty officers room.

Page 94	A. Ship Information	U-Boat Type VIIC

6	IX. Damage Control	U-boat Information

		With 40 tons or less buoyancy, the boat is still floatable only when there is no load.
		The dangerous trim moment caused by flooding end rooms can be compensated by simultaneous counter ballasting or blowing and draining. Next, weight reduction by localization of the leakages and immediate applying the steps from paragraph 3 e should be accomplished. Thus, any leakage in one room at trim condition A and B can be compensated by counter ballasting or draining. In each case the following measures are to taken to maintain sufficient buoyancy (gathered in Table 2):

		= Flood; = Blow; = Drain;
		Drain the fuel oil to the main ballast and reserve fuel oil tanks by means of auxiliary lubricating oil pump through the flexible hose and fuel oil compensating lines, the remaining overboard.

U-Boat Type VIIC	A. Ship Information	Page 95

U-boat Information	IX. Damage Control	7


Leak			Measure				Final State

Room	Capacity	Arm	Measure for		Intake	Arm	Remaining buoyancy	Total moment	Trim
	m³	+/- m	Trim condition A and B		m³	+/-	tons	+/- m tons	Status

E motor room	62	-18.75	A	MBT 5	25.3	+25.8
				MB/RFOT 4 stb./port	26.8	+6.95	79	-200.3	floatable
				Fuel oil tank 1(I)	37.9	-3.25

			B	MBT 5	25.3	+25.8
				MB/RFOT 2 stb./port	22.8	-7.95	78	-207.6	As per A
				Fuel oil tank 1(I)	37.9	-3.25

Diesel engine room	88	-10.95	A	MBT 5	25.3	+25.8	25
Diesel engine room				Forward torpedo room only partly	16.5	+18.85		0	floatable

			B	MB/RFOT 2 stb./port	22.8	-7.85
				MB/RFOT 4 stb./port	26.8	+6.95	25		As per A
				MBT 5	25.3	+25.8		0
				Forward torpedo room only partly	16.8	+18.85

Petty officers Room	47	-4.55	A	MBT 5 only partly	8.3	+25.8	100	0	floatable

			B	MB/RFOT 2 stb./port	22.8	-7.85	80		As per A
				MBT 5 only partly	1.35	+25.8		0

Control room	45	+2.30	A	Not required			110	+103.5	floatable

			B	Not required			60	+103.5	As per A

Officer and chief petty officers room	77	+9.65	A	Fuel oil tank 2(I)	32.8	+8.30
Officer and chief petty officers room				MB/RFOT 2 stb./port	22.8	-7.85	77
				MBT 1 only partly	11.2	-26.0		0	floatable

			B	Fuel Oil Tank 2	32.8	+8.30
				MB/RFOT 4 stb./port	26.8	+6.95	77
				MBT 1 only partly	11.0	-26.0		0	floatable

Forward torpedo room	72	+18.85	A	Fuel oil tank 2(I)	32.8	+8.30
Forward torpedo room				MB/RFOT 2 stb./port	22.8	-7.85	61	+66
				MBT 1	32.3	-26.0			floatable

			B	Fuel oil tank 2(I)	32.8	+8.30
				MB/RFOT 4 stb./port	26.8	+6.95	60	+59	As per A
				MBT 1	32.3	-26.0

Page 96	A. Ship Information	U-Boat Type VIIC

8	IX. Damage Control	U-boat Information

Table 2: Measures

for leaks in internal rooms.


		Trim	MBT		MB/RFOT		Fuel oil tanks (internal)			Remaining buoyancy	Total moment
Leak	m³	Cond.	1	5	2	4	1	2	Bow torpedo room	tons	meters tons

E motor room	62	A								79	-200.3

		B								78	-207.6

Diesel engine room	88	A							only partly 16.5	25	0

		B							only partly 16.8	25	0

Petty officers room	47	A		only partly 8.3						100	0

		B		only partly 1.35						80	0

Control room	45	A								110	0

		B								60	0

Officers and chief petty officers room	77	A	only partly 11.2							77	0

		B	only partly 11.0							77	0

Forward torpedo room	72	A								61	+66

		B								60	+59

		= Blow
		= Drain
		= Flood
		= Drain to MB/RFOT 4 and MB/RFOT 2, remaining overboard

		MB/RFOT 2 and 4 = on both sides (port and stb.)
		After taking these measures, the boat is in each case floatable. Further, heavy list can be compensated by applying steps from Table 4.

U-Boat Type VIIC	A. Ship Information	Page 97

U-boat Information	IX. Damage Control	9

	c)	Leakage into external tanks and into the pressure hull with the boat surfaced. (Tables 3 and 4)
		Stability calculations show that flooding an internal room and adjacent external tank at trim condition A and B can be compensated for by counter ballasting and draining.
		It is assumed that saddle tanks are full on both sides (because of flooding or counter ballasting to remove the list).


Leak			Measure				Final State

Room/Tank	Capacity	Arm	Measure with		Intake	Arm	Remaining buoyancy	Total moment	Trim
	m³	+/- m	Trim condition A or B		m³	+/- m	tons	+/- m t	status

E motor room	62	-18.75	A	MBT 5	25.3	+25.8
Main ballast tank 1	32.3	-26.00		FOT 1(I)	37.9	-3.25	34	-141	not
				FOT 2(I)	32.8	+8.30			floatable
				Forward torpedo room	72	-18.85

			B	MB/RFOT 2 stb./Port	22.8	-7.85	34	-148	As for A
				MB/RFOT 4 stb./port	26.8	+6.95
				Additional measures as for Trim A

Diesel engine room	88	-10.95	A	FOT 1(I)	37.9	-3.25
MB/RFOT 2 stb./port	22.8	-7.85		FOT 2(I)	32.8	+8.30	56	0
				MBT 5	25.3	+25.8			floatable
				Forward torpedo room only partly	33.9	+18.85

			B	MB/RFOT 4 stb./port	26.8	+6.95	56	0	As for A
				Additional measures as for Trim A

Petty officers room	47	-4.55	A	MBT 5 only partly	15.2	+25.8	70	0	floatable

MB/RFOT 2 stb./port	22.8	-7.85	B	MB/RFOT 4 stb./port	26.8	+6.95	70	0	As for A
				Additional measures as for Trim A

Page 98	A. Ship Information	U-Boat Type VIIC

10	IX. Damage Control	U-boat Information


Leak			Measure				Final State

Room/Tank	Capacity	Arm	Measure with		Intake	Arm	Residual	Remaining buoyancy	Trim
	m³	+/- m	Trim condition A or B		m³	+/- m	A t	+/- m t	status

Petty officers room	47	-4.55	A	MBT 5 only partly	9.5	-25.8	89	0
R/RFOT 1 stb./port	9.4	-3.25							floatable

			B	MB/RFOT 2 stb./port	22.8	-7.85	89	0	As for A
				MB/RFOT 4 stb./port	26.8	+6.95
				Additional measures as for Trim A

Petty officers room	47	-4.55	A	MBT 5 only partly	8.35	+25.8	84	0
RT 2 stb./port	15.2	-0.1							floatable

			B	MB/RFOT 2 Stb./Port	22.8	-7.85	84	0	As for A
				MB/RFOT 2 stb./port	26.8	+6.95
				Additional measures as for Trim A

Control Room	45	+2.30	A	MBT 1 only partly	3.92	-26.0	91	0
RT 2 stb./port	15.2	-0.1							floatable

			B	MBT 1 only partly	3.92	-26.0	41	0	As for A

Control room	45	+2.30	A	MBT 1 only partly	11.1	-26.0	72	0
MB/RFOT 4 stb./port	26.8	+6.95							floatable

			B	MBT 1 only partly	18.0	-26.0	65	0	As for A
				MB/FOT 2 Stb./Port	22.8	-7.85

Officer and chief petty officers room	77	-9.65	A	FOT 2(I)	32.8	+8.30	59	0
MB/RFOT 4 stb./port	26.8	+6.95		MBT 1 only partly	25.2	-26.0			floatable

			B	MB/RFOT 2 stb./port	22.8	-7.85	59	0	As for A
				Additional measures as for Trim A

Forward torpedo room	72	+18.85	A	FOT 2(I)	32.8	+8.30
MBT 5	25.3	+25.8		FOT 1(I)	37.9	-3.25	41	0
				MBT 1	32.3	-26.0			floatable
				E motor room only partly	54.6	-18.75

			B	MB/RFOT 2 stb./port	22.8	-7.85	41	0	As for A
				MB/RFOT 4 stb./port	26.8	+6.95

U-Boat Type VIIC	A. Ship Information	Page 99

U-boat Information	IX. Damage Control	11

Table 3 Measures

for leaks in internal rooms with adjacent external tanks


			MBT	MBT	MB/RFOT	MB/RFOT	FOT	FOT	Forward torpedo room	Remaining buoyancy tons	Total moment m t
Leak	m³	Trim	1	5	2	4	1(I)	2(I)	Forward torpedo room	Remaining buoyancy tons	Total moment m t


E motor room	94	A								34	-141

MBT 1		B								34	-148

Diesel engine room	111	A							only partly 33.9	35	0

MB/RFOT 2 stb./port		B							only partly 33.9	56	0

Petty officers room	70	A		only partly 15.24						70	0

MB/RFOT 2 stb./port		B		only partly 15.24						70	0

Petty officers room	56	A		only partly 9.5						89	0

R/RFOT 1 stb./port		B		only partly 9.5						89	0

Petty officers room	62	A		only partly 8.35						84	0

RT 2 stb./port		B		only partly 8.35						84	0

Control room	60	A	only partly 3.92							91	0

RT 2 stb./port		B	only partly 3.92							41	0

Control room	72	A	only partly 11.1							72	0

MB/RFOT 4 stb./port		B	only partly 18.0							65	0

Officers and chief petty officers room	104	A	only partly 25.2							59	0

MB/RFOT 4 stb./port		B	only partly 25.2						E motor room	59	0

Page 100	A. Ship Information	U-Boat Type VIIC

12	IX. Damage Control	U-boat Information


			MBT	MBT	MB/RFOT	MB/RFOT	FOT	FOT	Forward torpedo room	Remaining buoyancy	Total moment
Leak	m³	Trim	1	5	2	4	1(I)	2(I)	Forward torpedo room	tons	m t


Forward torpedo room	97	A							only partly 54.6	41	0

MBT 5		B							only partly 54.6	41	0

		= Blow
		= Drain
		= Flood
		Except in case 1, the boat is still floatable after taking these measures. When the E motor room and main ballast tank 1 are flooded, immediate measures leading to weight reduction and trim adjustment (table 4) are to taken.

Table 4: Additional measures

for weight reduction and trim adjustment


	Drain	Capacity	Arm	Moment
No.		tons	meters	m t

	By the bow :
1	1 Aft torpedo launched, tube drained, torpedo compensating tank 1 drained	-1.600	-26.46	+42.34
2	Aft deck torpedo container emptied (1 torpedo)	-1.500	-20.23	+30.35
3	1 reserve torpedo (E motor room) loaded and launched torpedo compensating tank 1 drained	-1.500	-18.61	+27.92
4	Torpedo compensating tank 1	Empty	-21.15	0
5	Trim weights aft	-0.375	-19.75	+7.40
6	Trim tank aft	Empty	-23.05	0
7	Dirty lubricating oil tank	-0.790	-12.85	+10.15
8	Lubrication oil supply tank stb.	-3.270	-11.45	+37.44
9	Lubrication oil supply tank port	-3.230	-11.45	+36.98
10	Lubrication oil collecting tank port	-0.800	-11.65	+9.32
11	Lubrication oil collecting tank stb.	-0.800	-10.65	+8.36

U-Boat Type VIIC	A. Ship Information	Page 101

U-boat Information	IX. Damage Control	13


Serial	Pump	Capacity	Arm	Moment
No.		tons	meters	m t


12	Fuel oil gravity tank	-0.730	-11.50	+8.39
13	Fuel oil collecting tank	-0.425	-9.55	+4.06
14	Fresh water tank 1 (galley)	-2.625	-7.05	+18.50
15	Waste water tank 1	-0.760	-6.05	+4.60
16	Fuel oil tank 1(I)	-37.900	-3.25	+123.17
17	Regulating and reserve fuel oil tank 1 port and stb.	-9.400	-3.25	+30.55
18	Regulating tank 2 port and stb.	Empty	-0.1	0

	By the stern:
1	Fresh water tank 2 (control room)	-0.465	+1.25	-0.58
2	Waste water tank 2	-0.485	+7.75	-3.76
3	Wash water tank (forward torpedo room)	-0.485	+7.75	-3.76
4	Fuel oil tank 2(I)	-32.800	+8.30	-272.24
5	Fresh water tank 3 (officer room)	-0.785	+9.90	-7.77
6	Torpedo compensating tanks 2 and 3	Empty	+15.25	0
7	Trim tank forward	Empty	+18.55	0
8	Forward deck torpedo container	-1.500	+19.18	-28.77
9	Trim weight forward	-0.375	+21.05	-7.89
10	4 bow torpedoes (forward torpedo room) loaded, launched, tubes drained, torpedo compensating tanks 2 and 3 drained	-6.400	+25.56	-163.58
11	6 reserve torpedoes (forward torpedo room) loaded, launched, torpedo compensating tanks 2 and 3 drained	-9.000	+17.68	-159.12
12	Loose the anchor	-0.400	+26.45	-10.60
	and chain	-1.676	+28.20	-47.20

All capacities of trim, regulating and torpedo compensating tanks are calculated as completely filled.

Page 102	A. Ship Information	U-Boat Type VIIC

14	IX. Damage Control	U-boat Information

	d)	Leakage with the boat submerged and with the boat lying on the bottom.
		Before blowing all main ballast tanks, and main ballast and reserve fuel oil tanks, to avoid wasting the compressed air, in case of a small leakage, according to the Diving Operations Manual, the following should be considered:
		1. How much water poured into the boat?
		2. Which main ballast tanks are probably damaged and can not be blown?
		3. If all undamaged main ballast tanks, and main ballast and reserve fuel oil tanks are blown, will the boat will have sufficient buoyancy to float?

		The reserve of compressed air on type VIIC U-boat:
		3.900 m³ under the pressure ~ 200 at
		is sufficient for a one-time full blow of:
		all main ballast tanks and main ballast and reserve fuel oil tanks (155 m³) at a depth of 40 meters.
		Main ballast tanks only (105 m³) at a depth of 65 meters.
		At depth 100 meters only 71 m³ can be blown.

		With sudden water flooding, according to the Diving Operations Manual, without any waste of time and without regarding for compressed air reserve, the main ballast tanks and main ballast and reserve fuel oil tanks should be blown immediately to the performance limit of the compressed air. However, the ballast tanks located opposite to the leakage (main ballast tank 1 or 5) should be blown cautiously or not at all in order to keep an even keel. The avoidance of dangerous trim angles, which despite of available buoyancy set the boat inclined to the bow or stern, is a crucial matter in a submerged boat.
		If blowing is successful, and the boat gets to the surface, and when only the one room (not compartment) with adjacent external tanks is fully flooded, by immediate counter ballasting and draining according to Tables 2, 3 and 4, the boat can be kept floatable.
		If there is not sufficient buoyancy to get the boat to the surface, the leakage always leads to the full flooding of the whole compartment up to the

U-Boat Type VIIC	A. Ship Information	Page 103

U-boat Information	IX. Damage Control	15

control room bulkhead. Exception: heavy leakage, which floods the compartment until pressure equalization.

The amount of water with fully flooded:

Compartment I	(After rooms)	197 m³
Compartment II	(Control room)	45 m³
Compartment III	(Forward rooms)	149 m³
Conning Tower		10 m³

The ability to surface in these cases exists only when the control room (as long as operation by the crew is possible), the conning tower or both are fully flooded. The possible weight reduction when the aft or forward compartment are fully flooded is not sufficient to create enough buoyancy.

When the control room , stability decreases by 1/6, when the conning tower is fully flooded – also by 1/6.

For boat lying on the bottom, in case of leakage, apply the rules written above. Take the boat to the surface slowly on an even keel by blowing, which is:

in the case of flooded control room, conning tower or both – possible (as long as operation by the crew is possible). The stability is sufficient. When compartment I or compartment III is flooded, surfacing is no longer possible.

When the boat is totally filled with water, there is no stability. The boat is stable only because it is lying on the bottom.

3) Leakage countermeasures.

Blowing.

The inflow rate formula

Q =

* F *

shows that, for example, at the depth h = 50 meters, the amount of water flooding into the boat through the same hole is 7 times greater than at depth 1 meter. Blowing the main ballast tanks and main ballast and reserve fuel oil tanks is therefore the first counter measure to decrease the flooding and being on the surface gives the possibility of limiting leakage into the room surfacing on an even keel so that no dangerous

Page 104	A. Ship Information	U-Boat Type VIIC

16	IX. Damage Control	U-boat Information

trim moments are caused by the free water surfaces.

In addition to the main ballast tanks and main ballast and reserve fuel oil tanks, the regulating tanks port and stb. can be also be blown.

Sealing the compartments.

All pressure and watertight bulkheads are to be shut.

Shut isolating valves on voice tube connections:

In E motor room:	Stern torpedo tube - conning tower and control room
	E motor room - diving officer station and conning tower
In control room:	Diving officer station - E motor room and conning tower, bridge
	Diving officer station - and helmsman - conning tower, bridge
	Control room and conning tower (both with whistle blowing lines) - E motor room
	Control room and conning tower (both with whistle blowing lines) - forward torpedo tubes
In officers room:	Radio and listening room - conning tower
In forward torpedo room:	Forward torpedo room - conning tower and control room
In conning tower:	Conning tower - Commanding Officer's room
	Conning tower - radio room
	Conning tower - diving officer station and E motor room

The bulkhead stop valves in ventilation intake and exhaust lines are to be shut and checked for tightness. Check the tightness of the connections of the drain lines leading to the aft and fore ship from the main draining manifold.

Sealing leaks.

To support bulkheads and seal leakages, the following materials are provided on the boat:

Leak shoring material.

4	Leak shoring timber	350 x 10 x 10 cm	in diesel engine room
4	"	200 x 10 x 10 cm	in forward torpedo room
2	"	200 x 10 x 10 cm	in aft torpedo room
4	Boards	75 x 30 x 4 cm	in diesel engine room
4	"	75 x 30 x 4 cm	in forward torpedo room

Sealing of the watertight bulkheads is possible only when the leaks occur while surfaced.

U-Boat Type VIIC	A. Ship Information	Page 105

U-boat Information	IX. Damage Control	17

Damage Control Kits.

1 each in
	Forward torpedo room
	Control room
	Aft torpedo room and E motor room
Contents of damage control kits:
1	Pincher pliers
1	Hammer
1	Screw driver (adjustable)
1	Pry bar
1	Chisel
1	Hatchet
2	Cross-cut chisel
1	Flat chisel
1	Hand saw
2	Drift pins/punches
30	Nails (3" to 5")
20	Wedges (various sizes)
20	Leak plugs (various sizes)
2	Clamps, oakum.

Leak canvas.

Only on support ship.

Pumping.

The performance of main drain pump which is

1300 liters/minute in parallel mode at a pressure head of 15 meters H₂O

is achievable only when draining from the control room. Due to flow resistance in pipelines the highest performance for the after ship is: 700 liters/minute in parallel mode at a pressure head of 15 meters H₂O.

For the fore ship it is: 550 liters/minute in parallel mode at a pressure head of 15 meters H₂O.

With this performance, leakage through holes of the following cross sections at different depths can be pumped out.

Page 106	A. Ship Information	U-Boat Type VIIC

18	IX. Damage Control	U-boat Information


		Leak cross section in cm²

Water-depth in meters	Main drain pump operating mode	After ship	Control Room	Fore ship
		700 liters/minute//	1300 liters/minute/	550 liters/minute//
		500 " - -	500 " - -	500 " - -

1	/ /	31	57	24
2	/ /	22	41	17
3	/ /	18	33	14
4	/ /	15	29	12
10	/ /	10	18	8
20	/ /	7	13	5
50	/ /	4	8	3
100	- -	2	2	2

// = parallel mode - - = series mode

		The values are calculated from Q = * F * with = 0.85
		(sharp-edged hole). The drain performance by // and -- mode are similar up to depth of 57 meters. At greater depth the performance by // mode decreases strongly. In practice you should switch to the -- mode at a depth of 50 meters. By the hook-up of the auxiliary trim and drain pump (358 liters/minute) in serial to the suction and pressure lines of the main drain pump, the drain performance at depths greater than 50 meters was increased during trials by 40%.

	e)	Weight relief.
		See Table 4 in paragraph 2 c.

4) Escape from a sunken boat.
	a)	Escape procedures.
		As soon as it becomes clear, that the boat is not able to surface, immediately, without waiting for any help, the crew prepares for escape. Pressure equalization takes place by intentional flooding of the pressurized compartment or the entire boat. For the closures which should be opened see paragraph 4 d.

U-Boat Type VIIC	A. Ship Study	Page 107

U Boat Study	IX. Damage Control	19

		Escape from the control room takes place via the conning tower, from the after ship through the galley hatch, and from the fore ship (if control room is not accessible) through the torpedo hatch. In the last case, there is no air trap provided but a small amount of air remains between the frames, in the upper part of the pressure hull.

		Immediately after beginning flooding, the cover of the escape hatch is unscrewed, so that when the pressure is equalized, the cover can be raised and flooding process will be accelerated. In the forward torpedo room the crew is to gather near the torpedo hatch (to keep in contact with each other), because after flooding orientation becomes difficult. To keep secure from water inrush, the crew should stay high, with legs supported by opened locker doors or upper bunks.

	b)	Influence of chlorine gas, nitrogen and oxygen.
		All available means must be used to flood the boat as quickly as possible because staying in a flooded boat at sea pressure is limited by:
		Influence of chlorine gas
		Influence of nitrogen (the bends, decompression sickness)
		Influence of oxygen (oxygen toxicity).

		Influence of Chlorine Gas
		The chlorine gas is created when the batteries are flooded with sea water. It can be recognized by the stinging, strong smell and forces the use of the escape gear.

		Influence of Nitrogen
		The breathing bag filling state varies between two boundary cases: an oxygen-rich and oxygen-poor mixture. The former limits the maximum staying time under

Page 108	A. Ship Study	U-Boat Type VIIC

20	IX. Damage Control	U Boat Study

pressure due to nitrogen effects, while the latter is limited by the damage caused by oxygen.

For filling the breathing bag with an oxygen-poor mixture, air with the following atmospheric proportion is used: ~80% N₂ and ~20% O₂, without adding oxygen from the oxygen flask. The maximum length of staying without symptoms of the bends is shown in Table 1.

For filling the breathing bag with an oxygen-rich mixture, the following proportion is used: ~20% N₂ and ~80% O₂. The maximum length of staying without symptoms of oxygen toxicity is shown in Table 2.

At depth below 20 meters with the breathing bag there must always be a sufficient amount of N₂ as a diluting agent for the oxygen, because the latter is harmful at an over-pressure of 2 at. The nitrogen also gives the sensation, that there is breathing air available – it remains in the same quantity, as no usage takes place. When the oxygen content drops below 10%, the mixture is no longer capable of being breathed.

The influence of nitrogen is not predictable. It is not always harmful, while the symptoms of oxygen toxicity always appear after a certain time. There have been cases of escaping from a depth of 40 meters, after remaining one hour under pressure, without any after-effects.

In the first boundary case, the oxygen-poor air mixture (~80% N₂ and ~20% O₂,) is not likely to cause symptoms of the bends after continuous surfacing, when the following times are not exceeded:

Table 1: Oxygen-poor Gas-air Mixture


Diving Depth	Staying Time

20 meters	30-60 minutes
30 meters	20-25 "
40 meters	15 "
50 meters	12 "
60 meters	8 "
70 meters	4 "
80 meters	3 "

U-Boat Type VIIC	A. Ship Study	Page 109

U Boat Study	IX. Damage Control	21

		There is a favorable effect, that the highest pressure is experienced only for the shortest time – it must be withstood at the pressure equalization time. While surfacing, the pressure is decreasing. The breathing bag in normal cases is filled with the oxygen-poor air mixture. The short flooding time at depth down to 50 meters is achieved with the medium cross-section holes. At deeper depths, after beginning flooding, as soon as the water counter-pressure allows, the larger shutters (torpedo tubes) are to be opened.
		Surfacing with decompression stops after staying longer under the pressure is in general not performed due to the ½ hour usage limit of the breathing bag, cold water, lack of time and existence of only one lead rope. Generally, the surface should be reached as fast as possible.

		After-treatment for rapidly decompressed crews is always required. They must stay in the pressurized chamber or U-boat rooms at 0.9-0.3 at over-pressure. When the pressurized chamber is not available, with the assistance of auxiliary ships, after a short rest (1 minute) at the surface, they should dive back to a depth of 3-5 meters, until the breathing bag's CO₂ absorbent cartridges are exhausted.

		Influence of Oxygen.
		The influence of oxygen under high pressure is noticeable after a certain time in every case. It is caused by unbound oxygen in the blood and leads to the trembling of the limbs, body spasms and finally to loss of consciousness. Movement and body effort speed up the appearance of oxygen toxicity symptoms. While surfacing, this chemically unbound O₂ is almost as harmful as nitrogen. Compared with N₂, the advantage is, that growing bubbles are gradually chemically bound. While the bends symptoms do not always appear, pressurized oxygen is always toxic after certain time. Trials with 100% O₂ proved, that the oxygen toxicity symptoms appear after following times:

Page 110	A. Ship Study	U-Boat Type VIIC

22	IX. Damage Control	U Boat Study

under 3 at over-pressure	in 35 minutes
" 4 "	" 15 "
" 5 "	" 10 "
" 6 "	" 5 "

In the second boundary case, which can occur while surfacing with the breathing bag, occurs when an oxygen-rich, 80% O₂ and 20% N₂ mixture used. Trials have proved that these proportions cause oxygen toxicity symptoms after time as shown in table 2. The experimental value (developed by Dräger) for the maximum staying time at a determined depth is derived from the formula - O₂ partial pressure respective to depth and possible staying time resulting in constant product equal to

50 at * minutes.

The O₂ partial pressure is i.e. at 80% oxygen content at depth 0 meters equal to 0.8 at, at depth 10 meters equal to 1.6 at and so on.

Table 2: Oxygen-rich Mixture


Diving depth	O₂ Partial-pressure	Staying Time
meters	at	=50:O₂-at

0	0.8	62 min
10	1.6	31 "
20	2.4	21 "
30	3.2	16 "
40	4.0	13 "
50	4.8	10 "
60	5.6	9 "
70	6.4	8 "
80	7.2	7 "
90	8.0	6 "
100	8.8	5.7 "

Staying time at shallow depths can be even longer. At depth 70-100 meters (trials not performed) it is safer to keep the time shorter. These times were designated with respect to oxygen toxicity symptoms and can be safely closed up. The influence of N₂ at 80% O₂ filling is irrelevant.

The high-grade oxygen mixture at greater depths is always harmful when specified times are exceeded, while the bends - if an oxygen-poor mixture is used

U-Boat Type VIIC	A. Ship Study	Page 111

U Boat Study	IX. Damage Control	23

		do not always appear, so close attention should be paid when filling with oxygen.
		Considering all influences, the breathing bag is filled as follows for escaping.
		Air with atmospheric proportion from boat's inside is used as an agent for diluting the oxygen. The breathing bag is filled by breathing out air, up to the half of the volume. Then, a small amount of oxygen is added, till the breathing bag is filled up to ¾ of the volume. Thus there is almost 50% content of oxygen. The breathing bag is ready for use. While the flooding goes on, the air inside the boat is still breathable, although because of increasing pressure the lungs containing a larger amount of air. When the stinging smell is noticeable (chlorine gas), the breathing bag should be used immediately.
		When the breathing mixture specified above is used, there are sufficient safety margins that no symptoms of the bends or oxygen toxicity are to be expected, if staying times from table 1 are not exceeded.

	c)	The practical use of the emergency escape gear.
		When using the breathing bag, the fundamental issue to determine is if there will be diving from the surface down to depth, or surfacing from depth up to the surface.
		When diving from the surface into the depth the breathing bag should be emptied and then filled with oxygen. In this case, the oxygen is not harmful, when a depth of 20 meters will not be exceeded.
		When escaping from a sunken boat from a depth of greater than 20 meters, the oxygen can be used only when diluted with air. The following rules apply:
		A. Before flooding:
		Put on the escape gear when ordered.
		Breath out the boat's air into the breathing bag, till the bag is half full.
		Close the mouthpiece.
		Add the oxygen, until the bag is three-quarters full.
		(pure oxygen without air only at depths down to 20 meters)

Page 112	A. Ship Study	U-Boat Type VIIC

24	IX. Damage Control	U Boat Study

B. Before escaping and when chlorine gas present:

Put the mouthpiece into the mouth.

Put on the nose-clamp.

(the over-pressure valve must be loosened)

C. While escaping:

Breathe out the air through the corner of the mouth.

D. After surfacing:

Secure the over-pressure valve.

Flooding options and flooding time.

Considering previously discussed influences of pressurized nitrogen and oxygen, on type VIIC U-boats the following openings for fast flooding can be used:

Flooding aftership to the control room bulkhead:

		Narrowest Flood Opening
		mm ø	cm²
1.1.)	At seawater filter aft torpedo and E motor room
	"Sea water intake for cooling pump and flooding torpedo compensation tank"	50	19.6
	"Hull valve for sea water intake for cooling pump and flooding torpedo compensation tank"
2.2.)	Casing "Cooling water discharge"
	"Hull valve for cooling water discharge"	50	19.6
3.3.)	From manhole torpedo compensating tank 1 (batter in) bow cap torpedo tube 5 outer door
	"Torpedo tube 5 flooding and drain lines" in passageway	72	40.8
4.4.)	At stb. cooling waterline filter in the diesel engine room:
	"Water intake for cooling pump stb."	110	95.0
	"Hull valve for sea water intake for cooling pump stb."
5.5.)	At port cooling water line filter in the diesel engine room:
	"Sea water intake for cooling pump port"	110	95.0
	"Hull valve for sea water intake for cooling pump port"
6.6.)	From cooling water gravity tank: remove cocks in fuel oil compensating water line in diesel engine room
	"Fuel oil compensating water line hull valve"	70	38.5
7.7.)	Remove check valve in W.C. petty officer room
	"Outer cock group on"	65	33.3
	"Inner cock group on"
	Total flooding cross section cm²:		341.8

U-Boat Type VIIC	A. Ship Study	Page 113

U Boat Study	IX. Damage Control	25


Water depth in meters	10	20	30	40	50	60	70	80	90	100

Flooding time in minutes	18.5	15.7	13.8	12.2	10.9	9.9	9.3	8.3	8.0	7.7

Below a depth of 50 meters, flooding time through above mentioned openings is greater than required for avoiding the bends. Additionally, the last escaping crew member in each case is exposed longer to the high pressure. To shorten this time, after flooding begins, as soon as decreasing pressure difference allows, the torpedo tube is to be opened (flooding the aftership through the aft torpedo tube only at depth 50 meters lasts 53 second, the flooding rate is 30 meters/second). To flood additionally through the aft torpedo tube:

Remove interlocks,

Open the breech door,

Open the outer door.

Flooding control room and conning tower:

		Narrowest Flood Opening
		mm ø	cm²
1.1.)	Via the bilge filter and hose connection (suction line)
	"Suction connection of the main drain pump"	100	78.5
	"Connection to the flooding and drainage manifold"
	"Sea water intake for flooding regulating tank"
	"Control room bottom valve"
2.2.)	"Hull valve for sea water intake for fine flooding of the regulating tanks"
	"Connection for flooding regulating tanks, regulating and reserve fuel oil tanks stb. and port"
	"Regulating and regulating and reserve fuel oil tanks stb. and port vent lines.	4 x 35	38.5
3.3.)	"Negative buoyancy tanks stb. and port vent lines"	2 x 55	47.6
4.4.)	Over the locker for star signal cartridges
	"Hull valve for flooding munitions magazine"
	"Connection for flooding star signal cartridges"	35	9.6
5.5.)	At the regulating discharge valve for the main drain pump
	"Main drain pump discharge"
	"Hull valve for main drain pump discharge"	90	63.6
6.6.)	Conning tower air outboard valve	40	12.6
			250.6

Page 114	A. Ship Study	U-Boat Type VIIC

26	IX. Damage Control	U Boat Study


Water depth in meters	10	20	30	40	50	60	70	80	90	100

Flooding time in minutes	6.9	5.8	5.1	4.5	4.1	3.7	3.4	3.1	2.9	2.8

Further flooding options through main ballast tank 3:

"Close the flood valves".

Release pressure through the "auxiliary trim and drain pump discharge".

Remove man hole cover main ballast tank 3.

Open the main ballast tank 3 vents (2 x 400 mm ø = 2 x 1256 cm²).

Flooding foreship from control room bulkhead:

		Narrowest Flood Opening
		mm ø	cm²
1.1.)	Manhole torpedo compensating tanks 2 and 3 (batter in)
	"Hull valve sea water intake for flooding torpedo compensation tanks 2 and 3"	70	38.5
	"Flooding torpedo compensating tank 2"
	"Flooding torpedo compensation tank 3"
2.2.)	Torpedo tubes 2 and 4 outer doors
	"Torpedo tubes 2 and 4 flooding and drain valves" in passageway
	"Torpedo tube 2 draining connection"	72	40.8
3.3.)	Torpedo tubes 1 and 3 outer doors
	"Torpedo tubes 1 and 3" flooding and drain valves" in passageway
	"Torpedo tube 3 draining connection"	72	40.8
4.4.)	Check valve WC petty officers room
	"Outer cocks group"
	"Inner cocks group"		33.3
5.5.)	Torpedo low pressure air control
	"2 cocks at each tube"	8 x 15	14.5
	Total flooding cross section cm² =		167.9
====================================


Water depth in meters	10	20	30	40	50	60	70	80	90	100

Flooding time in minutes	28.6	24.2	21.2	18.7	16.8	15.2	14.1	12.6	12.4	12

U-Boat Type VIIC	A. Ship Study	Page 115

U Boat Study	IX. Damage Control	27

The foreship flooding time is the longest. At depths below the 30 meters it is greater, than required for avoiding the bends. As soon as decreasing pressure difference allows, the compartment is additionally flooded through the forward torpedo tube (the crew have to take places in upper parts of compartment).

To flood additionally through one forward torpedo tube (flooding the foreship through only one forward torpedo tube at depth 50 meters lasts 40 seconds, the flooding rate is 30 meters/second):

Remove interlocks

Open the breech door

Open the outer door

When the control room is accessible:

"Hull valve for flooding the munitions magazine (65 mm ø)"

"Munitions magazine flood valve"

"Demolition charges storage flood valve"

Flooding the conning tower

	Narrowest Flood Opening
	mm ø	cm²
Conning tower air outboard valve	40	12.55


Water depth in meters	10	20	30	40	50	60	70	80	90	100

Flooding time in minutes	15.4	13.0	11.4	10.1	9.0	8.2	7.6	7.0	6.7	6.4

Flooding the entire boat

Flooding the entire boat takes place with the same openings as for flooding the single compartments.

Page 116	A. Ship Study	U-Boat Type VIIC

28	IX. Damage Control	U Boat Study

		Computation of flooding time
		The time needed for flooding the pressurized compartment till the pressure equalization at escaping hatch, is calculated from the following formula:

		L = air volume in the compartment about to flood..................m 3
		F = cross-section of the flood opening...................................cm 2
		= valve flow coefficient depending on the line type
		At depths below 4 meters it is equal to:
		for lines without valves ≈ 0.6
		for lines with one valve only ≈ 0.5
		for 2 lines connected by valves ≈ 0.3
		= coefficient depending on the water pressure according to the diagram:

		It should be noted that at shallow depths, the pressure is equalized before the water level reaches the lower edge of the air trap coaming. From that moment, special attention should be paid until the excess air leaks through the hatch and the water level rises up to the air trap coaming. The additional flooding time (after opening the hatch cover) is not included in the calculation. When the additional openings are opened (torpedo tubes, manholes, main ballast tank 3), the boat can be abandoned in 1 minute or less.

U-Boat Type VIIC	A. Ship Study	Page 117

U Boat Study	IX. Damage Control	29

5) Gas hazard.
		In the war zone the appearance of offensive warfare, explosive, combustion gases as well as smoke screens is to be expected. When gases enter the boat, the escape gear is to be used and the vessel is to be quickly rigged for dive except that the diesel engine air induction trunk is to be opened.
		After passing through the danger zone, all compartments are to be ventilated with the air blowers and all corners and pockets are to be blown out with compressed air.

6) Fire hazard.
		The fire sources inside the boat can be fought with portable fire extinguishers, at the upper deck additionally with the fire hose and nozzle from the deck wash line.
		The oxygen flasks, diesel engine starting air flasks and high pressure air banks are in certain circumstances in case of large fires to be emptied: oxygen flasks through the intake lines outboard, starting flasks through the diesel Engines, high pressure air banks into the ballast tanks. To fight fires in the electric installation, the dry fire extinguishers are used. Endangered main and auxiliary switchboards are shut down (disconnected by means of automatic battery circuit breakers). Endangered munitions magazines are to be flooded immediately.
		When the fire cannot be fought with available extinguishing equipment, the endangered compartment is to be abandoned and segregated (escape gear is to be taken).

7) Fire extinguishing equipment and flooding installation.
	For fire extinguishing equipment see paragraph VIII 1 c
	Flooding installation see paragraph VIII 1 d

8) Drainage and compressed air systems.
	Drainage installation see paragraph VIII 1 e
	Compressed air system see paragraph III 4

Page 118	B. Machinery	U-Boat Type VIIC

1	I. Propulsion Plant	U-boat Information

Chapter B. Machinery.

I. Propulsion plant.

1) M.A.N. diesel engine installation.

The diesel engine installation for some Type VII C boats consists of 2 M.A.N. engines with associated auxiliary machinery. The engines are single-acting four-cycle with fuel spray injection and supercharging. Both engines are reversible.

M.A.N. general and performance figures.

Type	M.A.N. - Marine diesel engine, Type M 6 V40/46 with forced induction by Buchi supercharger
Rated Power	Full load 1400 SHP
	Overload 1500 SHP
	Maximum load 1600 SHP
Rotational Speed	470/480/490 RPM
Fuel oil consumption	231 kg/hour (full load)
Cylinders	6
Supercharger Speed	9400 - 10900 RPM
Cylinder diameter	400 mm
Piston Stroke	460 mm
Piston Displacement	6 x 57.8 liters
Overall length	5630 mm
Overall height	2810 mm
Overall width	1400 mm

U-boat Type VIIC	B. Machinery	Page 119

U-boat Information	I. Propulsion Plant	2

	b)	Construction of the M.A.N. propulsion plant.
		The lower support for the engine block and the crankshaft bearings is the bed plate. It is built from three lying, open frames, which are held by fitting bolts. The bottom part of the frames form the oil pan.
		(See drawing page 130)
		The engine block consists of a lower part, upper part, and the top flange plate. The lower part is welded together from several parts. The upper part of the engine block consists of freestanding, separate cylinder barrels and admission of the reversing gear. These are separately bolted onto the lower part. On the upper part the continuous top flange plate as a main girder is fastened to the cylinder barrels by bolts and shear pins. The engine block is connected with the bed plate by fitting bolts. The cylinder covers are pressed to the block by studs and thus form the upper counter bearing for the cylinder cans.
		The tie rods extend from the bed plate to the top flange plate. They relieve the engine block of the combustion forces and transfer these directly to the support bearings in the bed plate.
		The cam shaft is situated at mid height in the engine, from which the push rods engage the intake and exhaust valves in the cylinder head. The fuel pumps are likewise propelled by cams on the camshaft.
		The engine is reversed by means of compressed air. The reversal is done by raising the rolls for push rods of the valve rocker arms and oil pumps and then shifting the camshafts.
		The fuel is injected into the combustion chamber of each cylinder by fuel oil injection pumps through type M.A.N. injection nozzles. Oil from the feed pump (geared type) is supplied to the individual fuel oil injection pumps. Fuel oil regulation is done via an safety automatic controller (centrifugal governor), which responds when the maximum permissible engine speed is exceeded. (overflow valve).

Page 120	B. Machinery	U-Boat Type VIIC

3	I. Propulsion Plant	U-boat Information

		Charging (increase in the amount of air to burn) takes place via a Büchi type supercharger. The turbine is driven by the exhaust gases. The engine develops improved performance with constant charging.

	c)	Auxiliary machinery associated with M.A.N. engines.

	1.	Superchargers.
		The supercharger is a Büchi type charger from B.B.C. Mannheim. The blower increases scavenging of the combustion chamber after the power stroke, cooling the piston surface, cylinder heads and exhaust valves, as well as filling the cylinders with a greater volume of air for the power cycle.
		Intake air is supplied by turbo-blower, whose drive takes place via a turbine propelled by the exhaust gases of the engine.
		Exhaust-gas turbine and intake blowers are assembled to a mounting set on the clutch side of the engine.

	2.	Pumps.
		Cooling water pump.
		The cooling water for cooling the engine lubricating oil cooler, the cylinder barrels, cylinder heads, exhaust valves and exhaust manifolds is fed by a double-piston pump. The drive of the pump takes place via the crank, which is propelled by gear wheel transmission from the crankshaft (Ratio 2:1).

		Lubricating oil pump.
		The entire engine as well as all important contact surfaces are lubricated by pressurized oil. Lubricating oil is distributed by a gear pump, which is located over the cooling water pump. The oil pump is driven by the gear wheel from the cooling water pump drive. The pressure of the lubricating oil is controlled by means of pressure control valve at the operating station.

U-Boat Type VIIC	B. Machinery	Page 121

U-boat Information	I. Propulsion Plant	4

		Fuel oil feed pump.
		The fuel oil feed pump is a gear pump and is located on the clutch side of the engine. It is driven from the camshaft. The pump feeds the fuel oil into the individual fuel oil injection pumps associated with each cylinder.

		Fuel oil injection pump.
		Each cylinder has its own associated fuel oil injection pump. The pump plunger is propelled by cams on the camshaft. The regulation of the amount of fuel oil depending on load occurs through a spill off valve which allows part of the pressurized fuel oil to back-flow to the suction manifold.

		The hydraulic governor oil pump.
		The oil needed for automatic adjusting of the fuel oil injection pumps is taken from the lubricating oil line and is supplied to the hydraulic governor by a special small gear pump. This pump is attached directly to the hydraulic governor and is driven by this governor.

		Supercharger oil pump.
		The pump is responsible for lubricating the bearings of the supercharger. It is a gear driven pump and is flange mounted to the inlet of the charger turbine. The drive shaft is coupled with the turbine shaft and drives the pump gears through a worm gear. The turbine oil pump draws the oil from its own tank and forces it by the hollow-bored worm shaft to the bearings of the turbine shaft. The oil running from the bearings flows back into the tank.

		Auxiliary cooling water pump.
		In case of a failure of the cooling pumps attached to the engines, an electrically driven centrifugal pump serving as auxiliary cooling water pump is provided in the diesel engine room. Pump performance is 48 m³/hour at a discharge head of 30 meters. The pump casing is directly connected with its driving motor.

Page 122	B. Machinery	U-Boat Type VIIC

5	I. Propulsion Plant	U-boat Information

		Hand cooling water pump.
		The hand operated water pump is designed as a double-acting piston pump. It draws sea water and discharges it to the cooling water control manifold.

		Auxiliary lubricating oil pump.
		The auxiliary lubricating oil pump serves for the lubricating of the engines before start-up, and backs-up the attached engine oil pumps in case of failure. The pump is an electrically driven vertically arranged screw pump and supplies 38 m³/hour of oil at a discharge head 50 of meters H₂O with at least 5 meters suction inlet head. The auxiliary lubricating oil pump can be used by change-over for the distribution of fuel oil.

		Hand lubricating oil pump.
		The hand lubricating oil pump is used to refill the lubricating oil collecting tanks, for the lubrication of the engines before the start-up, and in case of failure as an auxiliary lubricating oil pump. It is built as a double-acting piston pump. Its performance is 4.3 m³/hour.
		See paragraph B II. 2.

3) Governors, filters, lubricating oil cooler, starting air tanks (M.A.N.).

		Over speed governor.
		In order to prevent engine over-speed because of a sudden reduction of load, an automatic governor is provided, which decreases fuel delivery to prevent exceeding the maximum permissible engine speed. The governor does not actuate directly on the adjusting shaft, but actuates the pilot valve of the hydraulic governor.

		Hydraulic governor.
		The hydraulic governor amplifies and transfers output of the centrifugal governor to the control linkage of the fuel oil pumps. The transfer and amplification is done by means of lubricating oil which is supplied to the governor under a pressure of 6-8 kg/cm² by a small coupled gear pump. The centrifugal governor actuates the pilot valve, which allows the flow of the oil.

U-Boat Type VIIC	B. Machinery	Page 123

U-boat Information	I. Propulsion Plant	6

		The control linkage of the fuel oil injection pumps is thereby moved by a piston shifted by the pressurized oil. The engine receives more or respectively less fuel oil. Moving back the pilot valve interrupts the path of the oil and the speed regulating process is completed.

		Filter.
		The purifying of the fuel oil is done by means of EC-edge disk filters and for purifying lubricating oil an EC – 2-stage edge disk filter is used. Fuel oil and lubricating oil filters can be cleaned while in service by turning the handle.

		Lubricating oil cooler.
		The warm oil heated by friction surfaces is cooled in lubricating oil coolers. The coolers are built as tube coolers. Sea water flows through the tubes combined into a bundle, while the oil flows around the radiator. The cooling installation is designed so that the coolers can be bypassed.

		Starting air tanks.
		Engines are started by air under a pressure of 30 at. The reversing gear is also operated by the same compressed air. Each engine has an associated 125 liter air tank. The air tank operational pressure is 75 at. It is equipped with a relief valve, stop valve, a drain valve and a pressure gauge valve.

1) G.W. diesel engine installation.
		Diesel engine installation of some Type VII C boats consists of 2 G.W.-engines with associated auxiliary machinery. The engines are single-acting four-cycle with fuel spray injection and supercharging. Both engines are reversible.

Page 124	B. Machinery	U-Boat Type VIIC

7	I. Propulsion Plant	U-boat Information

G.W. general and performance figures.

Type	Germaniawerft Marine diesel engine, Model e.v. 40/46 with forced induction by Roots type blower
Power	Full load 1400 SHP
	Overload 1500 SHP
	Maximum load 1600 SHP
Speed	470/480/490 RPM
Fuel oil consumption	254 kg/hour (full load)
Cylinders	6
Cylinder diameter	400 mm
Stroke	460 mm
Displacement	6 x 57.8 liters
Overall length	5600 mm
Overall height	2895 mm
Overall width	1525 mm

Construction of the GW propulsion plant.

Bed plate and engine block (lower part) are constructed as one welded block, which consists of single, vertically standing cast steel frames, which are held down by welded steel plate. The two cylinder blocks (three cylinders each) are connected with this bed plate by means of tie rods passing through flanges on the lower edge of the cylinders. These tie rods relieve the working cylinders of the combustion gas forces and transfer them to the upper part of the raised bed plate. The cylinder heads are pressed by studs on the working cylinders and thus form the upper abutment for the cylinder cans. The fuel oil is injected into each cylinder by a fuel oil injection pump (Bosch design) and a fuel oil injector (type G.W.) into the combustion chamber. Oil from a fuel oil feed pump (gear pump) is transmitted to the individual fuel oil injection pumps. The delivery rate of the fuel oil pumps is controlled by shifting the regulator linkage (changing volume by means of beveled edge). The control regulator linkage can be moved by governor as well as by fuel oil control lever at the operating station. The governor is

U-Boat Type VIIC	B. Machinery	Page 125

U-boat Information	I. Propulsion Plant	8

		built as a centrifugal governor and is driven by an idler gear from the camshaft drive. Charging (increase in the amount of air to burn) takes place via a Roots type supercharger (G.W. type). The charger is arranged on the clutch side of the engine and is driven from the crankshaft by means of gear wheels through a hydraulic clutch. This hydraulic clutch and interlocking mechanism allows the charger to be used only while driving forward and engaging and disengaging it only when the engine is running. Cylinder barrels, cylinder heads, exhaust valves and exhaust manifolds are cooled by sea water, which is fed by a coupled cooling water pump (piston pump).
		The coupled lubricating oil pumps (gear pump) feed lubricating oil that is used to operate the hydraulic governor as well as for lubrication of the crankshaft bearings, cylinder barrels, camshaft bearings, the fuel oil pump control linkage and drive as well as for supercharger blowers. The engine can be reversed either by means of compressed air or by means of a special hand oil pump. Altering the direction is controlled by shifting the cam shaft in the longitudinal direction, so that the cams for the opposite direction of rotation engage push-rod rolls.

	c)	Auxiliary machinery associated with G.W. engines.
	1.	Superchargers.
		In order to have a greater air supply available, a Roots type blower is mounted on the clutch side of the engine. The blower is powered from the crankshaft of the engine by means of gear wheels. The blower is driven by means of a wrap-spring coupling, which prevents torsion vibrations and which takes up the distortion of the rotating motion. The supercharger clutch is a double cone type which can be engaged and disengaged from the operation station only while in "Ahead" drive, and only when the engine is running at full operational speed. In order to preserve the friction lining, the operating speed is to be lowered if possible when engaging to on.

Page 126	B. Machinery	U-Boat Type VIIC

9	I. Propulsion Plant	U-boat Information

	2.	Pumps.

		Cooling water pump.
		The cooling water for cooling the engine oil cooler, cylinder barrels, cylinder heads and the exhaust is fed by a double piston pump, which is at the front of the engine. The drive takes place via a crank, which is driven by gear wheel transmission from the crankshaft of the engine. A safety valve on the discharge side of the pump should respond when outlet valves are closed.

		Lubricating oil pump.
		The entire engine as well as all important contact surfaces are lubricated by oil fed from lubricating oil pressure line under appropriate, reduced pressure. The lubricating oil pump is driven by the gear wheel of the cooling water pump drive. It is a gear pump and operates in both directions of rotation. The adjustment of oil pressure takes place via a pressure control valve from the operating station.

		Fuel oil feed pump.
		The fuel oil is supplied by a special feed pump from the gravity fuel oil tank to the fuel oil injection pumps. It is a gear pump and is suitable for both directions of rotation. It is arranged over the camshaft.

		Auxiliary cooling water pump.
		For the cooling of the engines in case of failure the coupled cooling water pump an electrically driven centrifugal pump is provided in the diesel engine room as an auxiliary cooling water pump. The pump performance is 48 m³/hour of water against 30 meters H₂O. The pump housing is directly connected with the associated driving motor.

		Hand cooling water pump.
		The hand operated water pump is designed as a double-acting piston pump. It draws

U-Boat Type VIIC	B. Machinery	Page 127

U-boat Information	I. Propulsion Plant	10

		sea water and discharges it to the cooling water control manifold.

		Auxiliary lubricating oil pump.
		The auxiliary lubricating oil pump serves for the lubricating of the engines in case of failure of the coupled lubricating oil pumps and before start-up. The pump is an electrically driven vertically arranged screw pump and supplies 38 m³/hour of oil with discharge head of 50 meters H₂O and suction head of 5 meters H₂O. The auxiliary lubricating oil pump can be also be used for the distribution of fuel oil.

		Hand lubricating oil pump.
		The hand lubricating oil pump is used to transfer lubricating oil from supply tanks to the collective tanks, and in case of failure of the auxiliary lubricating oil pump to pump oil before the start-up of the engines. It is designed as double acting piston pump and its performance is 4.2 m³/hour.

	3)	Governor, filter, lubricating oil cooler, starting air tanks, lubricating oil purifying system.

		Governor.
		A centrifugal regulator is used as a governor which is mounted on the clutch side of the engine and is driven by an idler gear from the cam shaft drive. The governor prevents exceeding the maximum permissible engine speed by more than 10 percent. If the maximum permissible engine speed is exceed, the governor pushes control linkage towards the zero position.
		As soon as the number of revolutions decreases, the governor returns to its previous position and the control linkage brings the fuel oil lever back to the operational position by means of a spring.

		Fuel oil and lubricating oil filter.
		The purifying of the fuel oil is done by means of a system of EC-edge disk filters. To protect these filters against coarse impurities in the fuel oil

Page 128	B. Machinery	U-Boat Type VIIC

11	I. Propulsion Plant	U-boat Information

		a coarse sieve is inserted in the line before the fuel oil gravity tank.
		For purifying lubricating oil an EC-edge disk filter is used for each engine. The bearing lubricating oil as well as oil for the clutches and the hydraulic governor is filtered by these filters after branching from the oil cooler.

		Lubricating oil cooler.
		The entire lubricating oil cycling installation is cooled by a lubricating oil cooler attached to each engine. The cooling effect is achieved by forcing oil through coils, around which sea water flows. The cooling water installation is so designed that oil cooler can be bypassed as a whole or partially.

		Starting air tanks.
		Starting and reversing the engines is done by means of compressed air at 30 at. The compressed air is stored in dedicated tanks of capacity 200 liters each, connected together to the high pressure distributor (high pressure air bank 1 – high pressure manifold) through the reduction valve. The pressure reducing valve works automatically and holds the pressure in the starting air cylinders at 30 at. The tanks have safety valves set at 30 atmospheres at as well as necessary connecting valves, drain valves and control valve with pressure gauge.

		Lubricating oil purifying system.
		An electrically driven purifier with a capacity of 250 liters/hour is provided in the diesel engine room for purifying dirty lubricating oil. The purifier is equipped with an electrical oil pre-heater and a hot water pre-heater. Directly coupled with the drive shaft are the pure oil and dirty oil feed pumps. These two geared pumps arranged one after the other. The attached dirty oil pump sucks the contaminated oil from the lubricating oil collecting tanks and passes it over the oil pre-heater into the lubricating oil purifier. The cleaned oil is then pumped by the pure oil pump.

U-Boat Type VIIC	B. Machinery	Page 129

U-boat Information	I. Propulsion Plant	12

		The waste water from the oil purifying process drains into the bilge. A hot water pre-heater is provided for better cleaning of engine lubricating oil.

		1-1 Comparison between engines M.A.N. - G.W.


	M.A.N.	Krupp (G.W.)

Number of cylinders	6	6
Piston displacement	57.8. liters	57.8 liters
Piston speed	7.2 meters/second	7.2 meters/second
Efficiency	82.5	81.0
Speed	470 RPM	470 RPM
Supercharger speed	10,900 RPM	10,900 RPM
Performance	1400 SHP	1400 SHP
Stroke	460 mm	460 mm
Cylinder diameter	400 mm	400 mm
Length (whole engine)	5630 mm	5600 mm
Width (whole engine)	1400 mm	1400 mm
Height	2810 mm	2895 mm
Engine weight	38.476 tons	43.440 tons
Weight to power ratio	13.75 kg/SHP	15.5 kg/SHP
Fuel oil consumption (+)	0.165 kg/SHP	0.182 kg/SHP

Supercharger	Buchi Exhaust gas turbine B.B.C.	Roots type charger G.W.
Fuel oil regulation	Over flow adjustment	Chamber volume by means of beveled edge adjustment

(+) Full load.

[Note: engine weight above woud seem to be the total weight of the engine installation (2 engines)]

Page 130	B. Machinery	U-Boat Type VIIC

13	I. Propulsion Plant	U-boat Information

Assembly by tie rods (M.A.N. and G.W.)

Zylinderdeckel Cylinder head

Gurtplatte Top flange plate

Zurganker Tie Rod

Arbeitszylinder Work cylinder

Gestelloberterteil Engine block (upper part)

Gestellunterteil Engine block (lower part)

Triebwerksgehäuse und Grundplatte Crank case and bed plate

Grundplatte Bed plate

Ölwanne Oil pan

U-Boat Type VIIC
B. Machinery
Page 131

U-boat Information
I. Propulsion Plant
14

2) Battery.

The auxiliary and main power supply of the boat consists of two separately arranged storage batteries. Battery 1 is located under the petty officers room and battery 2 is under the officers room.

a) Technical and performance data.

Type: 33 MAL 800 W

Cells: 2 x 62

Number of negative plates: 34

Number of positive plates: 33

Cell weight: 493 kg +/- 2%

Total weight of batteries: 61132 kg +/- 2%

Capacity at 20 hour rate 9160 Amp hours

b) Construction and maintenance.

The cells of every battery are set up in 6 rows on step-shaped iron stands. Over the cells, there is an extractor duct that moves gases into the main exhaust trunk. Each cell is connected to the duct by a rubber tube. The U-tube manometer located outside of the battery room indicates the amount of suction in the extractor duct.

Between the single plates of each cell are insulators. The negative plates are equipped with hard rubber feet and stand on the box bottom, while the positive plates hang in the box itself. Plates of the same polarity are grouped together, both groups form a package. This is covered with a glass plate for protection against foreign objects. The plates of each group are connected by terminal strips.

Each strip has 5 terminals, which are passed through the box cover. Cell connectors (leaded copper rails) are screwed onto the terminals; the lid of the cells is double-walled and has 3 openings:

Extraction opening

Air entrance opening

Operation opening

Page 132	B. Machinery	U-Boat Type VIIC

15	I. Propulsion Plant	U-boat Information

		The air entrance opening is designed in such a way that during a boat’s inclination up to 35° in any direction no acid is spilled from the cell. The cell case is made of hard rubber and so strongly constructed that the ready-for-operation cell is easily transported using eyelets. The joint between the box and the lid is filled with a sealing compound. The sealing compound can be melted by means of a wire inserted into the groove of the joint by connecting the wire ends to the terminals of the cell.
		Each cell has a rating plate with data regarding type, manufacturer's number, manufacture date of the positive and negative plates and details regarding repairs and maintenance of the battery. Operating life of the battery depends on careful maintenance.
		Maintenance includes cleaning of the upper surface of the cells. Foreign bodies or contamination should not drop into the cells through the operation openings. Particularly dangerous is sea water containing chlorine, which destroys the positive plates. An external inspection of the battery must be carried out frequently. All suction pipes are to be regularly inspected to ensure they are working properly. A defective ventilation system may cause a battery explosion.
		An examination of all cells must be performed every 4 weeks in conjunction with recharging. This includes compensation of acid levels by adding distilled water, the measurement of the acid density, temperature and the voltage of the individual cells.
		So that stands, and the pressure hull are not corroded by acid which spills into the battery rooms, the bilge water is to be examined frequently. Both battery rooms can be rinsed with slaked lime and are connected to the draining system.

U-Boat Type VIIC	B. Machinery	Page 133

U-boat Information	I. Propulsion Plant	16

Capacity, discharging, final voltage.

The capacity of a battery is mainly dependent on the discharging current and the cell temperature. The following capacity values are at a reference temperature of 30° C.

Type 33 MAL 800 W


Discharge current	Duration	Amp Hours	Final Voltage in V
Amps	Hours	Ah	Cell	1/2 Battery

3630	1-1/2	5450	1.63	101.06

2960	2	5920	1.67	103.50

2200	3	6600	1.71	106.02

1480	5	7400	1.75	108.50

838	10	8380	1.78	110.36

458	20	9160	1.80	111.60

196	50	9800	1.80	111.60

The information listed in the preceding table about the capacity refers to discharging with a certain current, without interruption up to the final voltage. However, if discharge is stopped before battery exhaustion and is continued again later, the total capacity is greater. The battery has the ability to recover in the rest state.

Charging.

The Type 33 MAL 800 W charge begins with 1650 A (1st, charging phase) which is reduced gradually to 415 A (3rd, charging phase). Charging with low current is allowed. Cell temperature should not exceed 45° C.

Page 134	B. Machinery	U-Boat Type VIIC

17	I. Propulsion Plant	U-boat Information

In special cases "fast charging” is done by doubling the 1st, charging phase, the charging time is shortened by about 1/3.

3) The main switchboards and battery connections.

The main switchboards from the starboard and port sides are each connected via the automatic battery switch to a battery. Both main switchboards are contained in a rack and are identical. The switchboards contain the switches, regulators, relays, and measuring instruments for both drive and recharge mode. By the "battery – in parallel – or series – switch" both batteries can be switched to either in parallel or series, while the “E motor – in parallel – or series – switch” switches the armatures of E motors on each side of the boat either in parallel or serial.

Battery connection for ahead and astern:


Drive settings	Connection of the battery	Voltage

Dead slow	parallel	110/170 V
Slow	parallel	110/170 V
half speed	parallel	110/170 V
2 x half speed	serial	220/340 V
3/4 speed	serial	220/340 V
2 x 3/4 speed	serial	220/340 V
Emergency speed	serial	220/340 V

4) E motor installation.

Design and performance data.

Manufacturer	B.B.C. Mannheim
	A.E.G. Berlin
Weight of a machine with fan blower	B.B.C. 8100 kg.
	A.E.G. 8170 kg.

U-Boat Type VIIC	B. Machinery	Page 135

U-boat Information	I. Propulsion Plant	18

Motor rated power:		276/238 kW (60 min/continuous)
	Rated current:	1470/1240 A (60 min/continuous)
	Voltage:	210 V
	Number of revolutions:	295/280 RPM (60 min/continuous)
	Excitation voltage and current:	110 V 28 A
Generator rated power:		465kW(continuous)
	Rated current:	1550 A
	Voltage:	300 V
	Number of revolutions:	450 RPM
	Excitation voltage and current:	110 V 28 A

Machine construction and connections.

The E motors serve as motors to drive the propellers and as generators to charge the batteries. Each E motor is built as a fan cooled, totally enclosed, direct current, double-armature, with compound winding and commutating poles, has 2 x 8 main poles and just as many commutating poles. The motors are designed for forward and backward drive. Both armatures of the E motor can be connected in series or in parallel for drive. If one armature is damaged, the motor can still be driven in parallel connection.

Cooling is provided by a blower directly attached to each motor. It draws fresh air from E motor room and blows it into the center of the E motor. The exhausted air is cooled in 2 water-cooled air coolers lying between the E motors.

E motor armature connections:


Drive setting	Setting of the armature

Dead slow	serial
Slow	parallel
half speed	parallel
2 x half speed	parallel

Page 136	B. Machinery	U-Boat Type VIIC

19	I. Propulsion Plant	U-boat Information


Drive setting	Setting of the armature

3/4 speed	parallel
2 x 3/4 speed	parallel
Emergency speed	parallel

5) Shaft lines.

Propellers.

The three-bladed propellers are made from a single piece, and mounted on the shaft's cone with a key and nut. For better water flow and to protect the propeller mounting, the aft end of the screw hub is secured by a cowling cover, which also secures the attaching nut. The area between the shaft's support and the propeller hub is covered by metal sheet to protect against penetration by foreign objects.

The propellers can be removed using a jacking fixture.

In forward drive, the propellers turn top to outboard.

The propellers have the following dimensions:

Diameter	1620 mm
Pitch	1540 mm
Total area	0.93 m²
Projected area	0.81 m²
Material	Special casting brass grade B

Drive shafts, bearings and shaft brakes. (See drawing)

Each of the two drive shafts consists of

Propeller shaft

Thrust shaft

To these shafts are coupled the electric motor shaft and diesel engine shaft.

Shafts are made from Siemens Martin-Stahl (special type of steel) and are hollow, with conical ends.

U-Boat Type VIIC	B. Machinery	Page 137

U-boat Information	I. Propulsion Plant	20

		Propeller shafts can be removed from behind, for that reason they have a removable coupling flange on the front end. The thrust shafts have a forged flange on both ends. The torque measuring device indicator gauge is fastened at the rear coupling flange. The front flange is connected to the main clutch. The drive for the revolution counter is connected in the rear part of the main thrust bearing housing. The bearings are made of bronze, all parts of the shaft exposed to sea water are coated with rubber. A wire rope taping between aft stern tube bearing and the strut bearing serves as protection against damage. The propeller shaft's strut bearing is made as a two-part bronze bushing with lined inner surface fitted with lignum vitae wood strips which can be removed from forward and which is secured from rotation. The stern tubes are made from Siemens-Martin ingot steel and the bearings are made of bronze. One zinc protection ring per tube is inserted in forward and aft bearings. For lubricating and cooling purposes stern tube bearings are connected to the Diesel engine cooling water line.
		The shaft brake is a differential band brake which is driven by a lead bolt and affects on a shaft drum behind the flange coupling. It is so designed that the propeller shaft is held safely when main clutch is disengaged and the other propeller shaft is running at full speed.

	c)	Main thrust bearing.
		To carry the axial thrust of the propeller there is a one disk thrust bearing for each shaft, which can transfer up to 10,000 kg of thrust.
		The thrust is transferred to the front or rear sliding pad of the thrust bearing by a thrust collar on the intermediate shaft and via the bearing housing to the boat. The thrust bearings have auto-lubrication and a connection for closed-circuit cooling of the lubricating oil.

Page 138	B. Machinery	U-Boat Type VIIC

21	I. Propulsion Plant	U-boat Information

		The bearing housings are made of cast steel and sliding pads are made of Siemens-Martin steel. The bearing holders and sliding pads are filled with white metal. The thrust bearings are connected to the foundation by bolts and removable wedges.
		The thrust bearings are constructed in such a way that a guide ring with a pressure gauge can be inserted to measure the propeller thrust. The thrust bearings are designed for forward and reverse drive.

	d)	Clutches.
		Main clutches.
		The thrust shaft and the electric motor shaft are connected by the main clutch, which is constructed as a disengageable double cone friction clutch. It permits small axial shifts of the shafts. The main clutch is manually operated for engaging and disengaging the propeller shaft by shifting each of two friction cones on a two-part sleeve.
		The nominal torque which can be transferred is about 2150 mkg [15,050 ft/lbs], the maximum operating torque is 4400 mkg [30,800 ft/lbs].

		Diesel engine clutch.
		It is constructed in the same way as the main clutch and serves for disengaging the diesel engine. The engaging and disengaging are done via a piston ram operated with compressed air and oil. In case of failure of the piston or compressed air, the clutch can be operated by hand. The maximum torque is 8800 mkg [61,600 ft/lbs].

U-Boat Type VIIC	B. Machinery	Page 139

U-boat Information	I. Propulsion Plant	22




	Motorwelle	Engine shaft
	Schwingungsdämpfer	Flywheel
	Dieselmotor	Diesel engine


	Dieselmotorkupplung	Diesel engine clutch
	E-Machine welle	E Motor shaft
	Schott 16-1/2	Bulkhead (frame 16-1/2)
	Maschine 2	Motor 2
	E Maschine	E motor
	Maschine 1	Motor 1

	Hauptkupplung	Main clutch
	Druckwelle	Thrust shaft
	Hauptdrucklager	Main thrust bearing

	Flanschenkupplung	Flange coupling
	Schraubenwelle	Propeller shaft
	Wellenbremse	Shaft brake
	Stopfbuchse	Stuffing box
	Druckörper	Pressure hull
	Vorderes Stevenrohrlager	Forward - Stern tube bearing
	Hinteres Stevenrohrlager	Aft - Stern tube bearing


	Wellenbocklager	Shaft strut bearing
	Schraube	Propeller

Page 140	B. Machinery	U-Boat Type VIIC

23	I. Propulsion Plant	U-boat Information

6) Inter-operation of the engines and motors.
	a)	General.
		The diesel engines provide a maximum surface speed of about 18 knots and both E-motors provide a submerged speed of 8 knots. The different working modes are listed below:
		Diesel engine only drive,
		E motors only drive,
		Support and buffer mode,
		Diesel-electric drive,
		Charging mode.
		Exhaust gas from both diesel engines can be diverted and used for blowing out the main ballast tanks and main ballast and reserve fuel oil tanks.

	b)	Diesel engine only drive.
		In diesel engine only drive; both diesel engines drive the propellers via the diesel engine couplings, E motors, main couplings, thrust shafts and the propeller shafts.
		In this arrangement the E motors are just a part of the drive train and the armatures are unpowered. The fan blowers of the E motors rotate slowly powered by voltage generated due to the remanent magnetism of the unpowered rotating armature.

	c)	E motors only.
		With E motor drive only, the diesel engine coupling is un-clutched. The E motors are powered by the battery and work as motors driving the propellers via the main couplings, thrust shafts and the propeller shafts.

	d)	Support and buffer mode.
		In support mode, the output power of the diesel engines is increased by switching on the E motors additionally. Each diesel engine via the diesel engine coupling and in addition each E motor acting as a motor drives the propeller. The buffer mode is used in rough seas. The diesel engines drive the ship's propellers as in "Diesel engine only drive". The E motor voltage is adjusted such that with normal conditions the loading and discharge current

U-Boat Type VIIC	B. Machinery	Page 141

U-boat Information	I. Propulsion Plant	24

		are equal to zero. If the screw runs above the surface, thus causing unintentional reduction of load on the diesel engine, the E motor works as a generator preventing an inadmissible increase in diesel RPM.

	e)	Diesel-electric drive.
		Diesel-electric drive allows driving both propellers even if one diesel engine has failed. The operational diesel engine works directly driving the propeller on its side. The E motor whose armature would normally run idle, works as a generator delivering power to the other ship side. The E motor on the other side drives the propeller; the diesel engine clutch is disengaged. The current from the primary E motor can either be switched in such a way that it only drives the secondary E motor or an additional light charge of the batteries takes place.

	f)	Charging operation.
		Charging operations can be differentiated as follows:
		Charging with a disengaged propeller shaft,
		Charging while running on the surface with diesel engines.
		When charging with a disengaged propeller shaft, the diesel engine drives the E motor via the diesel engine clutch. The E motor runs as a generator and charges the storage batteries.
		When charging while on the surface with the diesel engines; the diesel engine power drives the propeller. At a constant number of revolutions from the diesel engine, the E motor charges the batteries. In this case, the diesel engine must provide power for the propeller and for charging.

Page 142	B. Machinery	U-Boat Type VIIC

1	II. Auxiliary Machinery for Propulsion	U-boat Information

II. Auxiliary Machinery for Propulsion.

1) Ship's auxiliary machinery.
	a)	Main rudder and dive planes.
		The operating installations of main rudder and dive planes are similar in their fundamental construction of driving motors and steering servos. Each steering installation (main rudder, aft dive planes, forward dive planes) consists of following parts:
		Driving motor with gearbox,
		Steering switch,
		Selection switch,
		Remote starter,
		Limit switch,
		Starting, breaking and shunt field resistor,
		Cut off switch.
		The driving motor for the main rudder and dive plane installation is manufactured by B.B.C., and is a direct current, 4-pole, compound winding electric motor with a coupled gearbox manufactured by Köllmann.
		The steering switch is used to turn on and toggle the electromagnetically operated remote starter, i.e. to remotely control - through the remote starter - the driving motor.
		The selection switch enables driving the main rudder from several different steering switches.
		The remote starter is used to directly switch the driving motor to run in one or the other direction and to connect the breaking resistor.
		Limit switch assures that driving motor and coupled gearbox will stop when it reaches the ending position.
		Immediately after switching off the driving motor, the armature winding is short-circuited with the breaking resistor in order to stop the motor. Starting, breaking and shunt field resistors are used to start the motor, to stop the motor by short-circuit armature winding and to protect the shut field winding from high self-inductance while turning off respectively.
		The coupled gearbox converts high speed revolutions of the driving motor to low speed revolutions.

U-Boat Type VIIC	B. Machinery	Page 143

U-boat Information	II. Auxiliary Machinery for Propulsion	2

Main Rudder installation:

	Direct Current Motor	Gearing Mechanism
Manufacturer	B.B.C. Sarrbrücken	Köllmann A.G. Lepzig
Model	GS 10 b	G 2766
Weight	198 kg	137 kg
Rated power	3.54/4.86 kW 60 min	4.8/6.6 Hp 60 min
	5/7.72 kW 1 min	6.8/10.5 Hp 1 min
Number of RPM	650/880 60 min	650/880 60 min
	495/790 1 min	495/790 1 min
Current	42.4/34.3 A 60 min
	67/57 A 1 min
Voltage	110/170 V

Forward Dive Plane installation:

	Direct Current Motor	Gearing Mechanism
Manufacturer	B.B.C. Sarrbrücken	Köllmann A.G. Lepzig
Model	GS 9 b	G 2717
Weight	140 kg	137 kg
Rated power	2.58/3.75 kW 60 min	3.5/5.1 Hp 60 min
	5/5.74 kW 1 min	5.00/7.8 Hp 1 min
Number of RPM	900/1170 60 min	900/1170 60 min
	715/1085 1 min	715/1085 1 min
Current	29.7/27 A 60 min
	59.8/41.6 A 1 min
Voltage	110/170 V

Aft Dive Plane installation:

	Direct Current Motor	Gearing Mechanism
Manufacturer	B.B.C. Sarrbrücken	Köllmann A.G. Lepzig
Model	Gs 9 b	G 2698
Weight	140 kg	137 kg
Rated power	Same as above	Same as above
Number of RPM	Same as above	Same as above
Current	Same as above
Voltage	Same as above

Anchor and warping capstan installation.

Compressed-air engine is built as a bi-directional gear pump. According to

Page 144	B. Machinery	U-Boat Type VIIC

3	II. Auxiliary Machinery for Propulsion	U-boat Information

required rotation direction, compressed air is admitted from one or the other side of two slant-tooth gear rotors.

Manufacturer	Demag, Duisburg
Model	Z S U 20
Power	19 Hp
Weight	330 kg
Number of RPM	740
Consumption	48.6 m3/HP h?

Air compressor.

I. E-Air Compressor

Two 4-stage air-compressors of the same design.

	Direct Current Motor	Air Compressor
Manufacturer	Garbe & Lahmeyer	Krupp GW, Kiel
Model	RP 81 a	HK 1/1
Rated Power	23.5/28 kW (total input)	6.1/6.6 1/min
Weight	1030 kg	636 kg
Number of RPM	550/650	Same as motor
Current demand	256/190 A
Voltage	110/170 V
Operating pressure		205 kg/cm²

II. Diesel Air Compressor

Manufacturer	Junkers Motorenbau G.m.b.H.
Model	4 FK 115
Performance	8.5 liters/minute at 205 kg/cm²
Weight
Total machine with exhaust system: approximately 560 kg
Cycles when working against no load	810 at 150 kg/cm² back-pressure
Cycles when working against full load	860 at 205 kg/cm² back pressure
Operating pressure	205 kg/cm²
Minimum allowable back pressure (Stage IV)	150 kg/cm²
Maximum allowable back pressure	215 kg/cm²
(Lifted safety valve)

U-Boat Type VIIC	B. Machinery	Page 145

U-boat Information	II. Auxiliary Machinery for Propulsion	4

Auxiliary drain and trim pump.

	Direct Current Motor	Pump
Manufacturer	A.E.G.	Klein, Schanzlin & Becker
Model	A W 76	MKS 6
Rated Power	13.2/15.5 kW (total input)	300-360 1iters/minute
Weight	365 kg	330 kg
Number of RPM	1600/1920 RPM
Current	144/110 A
Voltage	110/170 V
Discharge head		100 meters

Main drain pump.

	Direct Current Motor	Pump
Manufacturer	B.B.C., Manheim	Amag Hilpert, Pegnitzhütts
Model	GS 11 B	Fh I/4
Rated Power	20.6/30 kW (total input)	1300/1465 liters/minute
		against 15 meters
		500/900 liters/minute
		against 105 meters
Number of RPM	2600/3050 RPM	2600/3050 RPM
Weight	300 kg	250 kg
Current	213/198 A
Voltage	110/170 V
Discharge head		140 meters

Intake and exhaust air fan.

Two air fans are mounted in the diesel engine room, an exhaust air fan on the port side and an intake air fan on the starboard side.

The air fan casing is made in such a way, that it is gas-proof under the pressure of 2.5 meters H₂O. Casing and fan wheels are primed and surfaced with acid-proof coating. The fan's shaft is sealed so that water and battery gases cannot penetrate to the driving motor.

Above each air fan is attached S-shaped drain pipe, connected without any valve to the air trunk.

Page 146	B. Machinery	U-Boat Type VIIC

5	II. Auxiliary Machinery for Propulsion	U-boat Information

The air fans are driven by direct current, compound-winding motors with starting windings. After starting the motor, the series winding is short-circuited. Motors have water splash and water flush-proof casings.

Both motors are provided with a group switch for setting required operation mode and a starting switch. Using the group switch the following operation modes can be set:

Position I	Two motors in series (half voltage)
Position II	Two motors in parallel (full voltage)
Position III	Port motor only
Position IV	Stb. motor only.

	Direct Current Motor	Fan
Manufacturer	A.E.G.	Turbon, Berlin
Model	AWV 54	H 102/38
Weight	110 kg	45 kg
Current	52/46.5 A
Rated Power	4.8/6.6 kW (total input)	2600/2700 m³/hour
Number of RPM	3000/3450 RPM	3000/3450 RPM
Voltage	110/170 V
Pressure head		22/24 mm H₂O

Periscope drive.

Periscope drive is implemented as a hydraulic power system. The hydraulic pressure is created by the main pressure oil pump and/or the auxiliary pressure oil pump, both with the same fan blower. Two hydraulic motors are provided for lifting and lowering the periscopes one in the conning tower and one in the control room; a third hydraulic motor is located in the conning tower for turning the attack periscope.

Pressure pumps and hydraulic motors are screw type and are the same in their construction. They are different only in their operating modes. They are built from one central power rotor and two outer idler rotors. All three screw rotors are double-start threaded, engaged with each other in such a way that they are sealed against them as well as against the closing cover

U-Boat Type VIIC	B. Machinery	Page 147

U-boat Information	II. Auxiliary Machinery for Propulsion	6

The oil working chamber, where the pressure pump compresses oil and where the hydraulic motor converts pressure to the rotation of the power rotor, is bounded by the edges of the threads of the screw rotors and the sealed pump/motor casing.

Pressure oil pumps can turn in only one direction, hydraulic motors can rotate in both directions.

Each pressure oil pump is driven by a direct current motor. The motor is started automatically by contact sensor, but can be also started manually.

Pressure Oil Pump

	Direct Current Motor	Pump
Manufacturer	Siemens, Schuckert	(Main and Auxiliary hydraulic pumps) Krupp G.W., Kiel
Model	HG 147/17 m V1	V 45/6
Weight		75 kg
Rated Power	9.6/19 kW	on average 106 1iters/minute
	14.8/29.5 kW
Number of RPM	1600/1470 RPM	Same as driving motor
	1920/1820 RPM
Current	106/210 A
Voltage	110/170 V
Propulsion performance		12.5/24.5 HP
Maximum pressure		90 kg/cm²

Hydraulic Motor (Attack and Control R periscopes)

Manufacturer	Krupp GW, Kiel
Model	38 - 6
Performance	115 1iters/minute
Weight	63 kg
Number of RPM	1500 RPM
Maximum pressure	70 kg/cm²

Page 148	B. Machinery	U-Boat Type VIIC

7	II. Auxiliary Machinery for Propulsion	U-boat Information

Rotary Motor (Attack Periscope)

Manufacturer	Krupp GW, Kiel
Model	25-6
Performance	32 1iters/minute
Weight	22 kg
Number of RPM	1500 RPM
Maximum pressure	70 kg/cm²

Refrigeration plant.

A refrigeration plant is installed on the boat for the preservation of food and production of ice. It consists of a refrigeration unit in the control room and a refrigeration chamber in the petty officers room. The refrigeration unit consists of a compressor with its driving motor and condenser. The refrigeration chamber houses the evaporator. Refrigeration is achieved by picking up external heat by a liquid refrigerant (Freon), which in so doing is vaporized. The process is sustained, when the Freon vapor is drawn, pressurized by the compressor and condensed to a liquid.

The evaporator side of the compressor provides the low pressure required to evaporate the refrigerant while the condenser side provides the high pressure needed for condensing the vapor.

The liquid refrigerant moves from condenser to evaporator through a regulating valve. The valve maintains the steady flow of refrigerant and despite its double state changes doesn't allow it to run out in any part of the refrigeration circuit.

The compressor is an air-cooled, 1-stage, 2-cylinder, piston type of vertical design. Both cylinders and cylinders head are cast as one block, which is bolted to the crankcase. The compressor is driven by a direct current shunt motor with auxiliary series winding. The motor casing is water splash resistant and damp-proof at inclination of the boat up to 30° and temperatures up to 45° C.

U-Boat Type VIIC	B. Machinery	Page 149

U-boat Information	II. Auxiliary Machinery for Propulsion	8

The refrigeration plant is automatically controlled – required temperature is achieved by turning on and off the compressor, there is also a pressure switch which turns off the compressor if liquefaction pressure is too high.

Refrigerator

	Direct Current Motor	Cooling Compressor
Manufacturer	B.B.C., Mannheim	B.B.C. Mannheim
Model	GS 5 a
Power	0.5/0.65 kW (total input)	250 changes/hour
		-15° Vaporizer Temperature
		+30° Cooling Temperature
Number of RPM	1300/1600 RPM	345 RPM
Voltage	110/170 V
Ice production		6 kg/day

Distilling unit.

For production of the fresh water an electric distilling unit is installed in on the port side of the control room. Distillate created by evaporation of sea water can be used as drinking water or to fill up the electrolyte in batteries.

Evaporation takes place in a vacuum of 1.6 – 2 meters H₂O. The vapor is drawn from evaporation chamber and forced into the condenser by the compressor. In the condenser the heat of the condensing vapor is taken up by cold sea water bathing the condenser and in this way is used again in the evaporation process. The heat of fresh water leaving the condenser and of the concentrated brine is withdrawn in refrigeration coils and used to preheat feed sea water.

The distilling unit consists of a cast-metal case, in which is installed the condenser, heating resistances and cooling chamber. The cast body is covered by a copper cap, which creates an evaporation chamber. A safety valve is installed in the cap and thermal insulation of the driving motor and case.

Page 150	B. Machinery	U-Boat Type VIIC

9	II. Auxiliary Machinery for Propulsion	U-boat Information

The driving motor drives the compressor via a vee belt, through first gear stage the brine pump and through second gear stage the scrubbers which keep the condenser coils clear of scale. The driving motor is a direct current motor with compound winding. It incorporates a self cooling fan and a water splash-resistant casing.

Manufacturer	Siemans G.m.b.H.
Rated Power	8/10 liters/hour
Power (total input)	1.6 kW
Number of RPM	2800/3600 RPM
Weight	325 kg
Voltage	110/170 V
Current	18 A

Hand pumps etc.

Hand Lubricating Oil Pump:

Manufacturer	Klein, Schanzlin & Becker
Type	Double acting piston pump
Weight	19.0 kg
Model	Franconia Gr. 3

Hand Cooling Water Pump:

Manufacturer	Klein, Schanzlin & Becker
Type	Double acting piston pump
Weight	19.0 kg
Model	Franconia Gr. 3

Hand Dirty Oil Pump:

Manufacturer	Klein, Schanzlin & Becker
Type	Double acting piston pump
Weight	12 kg
Model	KSB Gr. 3

Hand Fresh Water Pump:

Manufacturer	Klein, Schanzlin & Becker
Type	Double acting impeller pump
Weight	6.6 kg
Model	KSB Gr. 3

U-boat Type VIIC	B. Machinery	Page 151

U-boat Information	II. Auxiliary Machinery for Propulsion	10

Hand Wash Water Pump:

Manufacturer	Klein, Schanzlin & Becker
Type	Double acting impeller pump
Weight	4.8 kg
Model	KSB Gr. 3

W.C. installation.

A W.C. pump is installed at aft part of petty officers room and at the forward part of officers and chief petty officers room. The pump's piston is driven reciprocally by means of compressed air. The control of air flow is done manually by changeover cock, which must be set in the middle position "pumping by hand", when the pump is operated manually.

	Pump Toilet
Manufacturer	Triton, Belco Hamburg
Weight	86.5 kg

Gyro compass installation.

See paragraph A VIII 3 a.

2) Auxiliary machinery of the diesel engine installation.

Auxiliary lubricating oil pump.

The auxiliary lubricating oil pump is a reserve pump used in case of damage to the coupled lubricating oil pump to lubricate and cool the engines. It can also be used for the loading or transfer of lubricating oil.

The pump is a screw type, of vertical construction driven directly by a direct current (shunt) motor coupled with elastic bolt-leather coupling. Pump and motor are placed on a common mounting.

The auxiliary lubricating pump can take suction from the following locations:

From upper deck

From lubricating oil collecting tank

From lubricating oil supply tanks

Page 152	B. Machinery	U-boat Type VIIC

11	II. Auxiliary Machinery for Propulsion	U-boat Information

Pressurized oil can be moved:

To the upper deck

To the diesel engines port and stb.

To the reserve lubricating oil tanks

To the lubricating oil collecting tanks

	Direct Current Motor	Pump
Manufacturer	B.B.C., Mannheim	Leistritz, Nürnberg
Model	G S-10 a	72 N
Rated Power	9.1/10.3 kW (total input)	252/638 1iters/minute
Weight	174 kg	100 kg
Number of RPM	2000/2400 RPM	200/2400 RPM
Current	87/70 A
Voltage	110/170 V
Operating pressure		5 kg/cm²

Auxiliary cooling water pump.

The auxiliary cooling water pump is built as a one-stage, non-self-priming, vertical, spiral-casing, centrifugal pump, and is directly flange-mounted with its driving motor (direct current, shunt). The pump does not have its own propelling shaft. The shaft of the driving motor is lengthened and is coupled with a slot on the pump rotor and secured with a protective sleeve.

The auxiliary cooling water pump takes suction from port or stb. cooling water injection pipe system and pressurizes the cooling water distributor.

	Direct Current Motor	Pump
Manufacturer	A.E.G., Bremen	Odesse, Oschersleben
Model	AWV 65	G 80/180
Rated Power	8.8/11 kW (total input)	800 liters/minute
Weight	179 kg	28 kg
Current	96/78 A
Number of RPM	2900/3300 RPM	2900/3300 RPM
Voltage	110/170 V
Operating pressure		3 kg/cm²

U-Boat Type VIIC	B. Machinery	Page 153

U-boat Information	II. Auxiliary Machinery for Propulsion	12

3) Auxiliary machinery for the E installation.

E motor fan blower .

The motor windings of each E motor are cooled by a fan blower attached to the casing. The blower draws fresh air from E motor room and blows it into the center of the E motor. The warm air leaves the motor case through lateral openings in the upper parts of the bearing shields and then to a pair of coolers cooled by sea water.

The blower is consists of a galvanized iron cast casing and the fan wheel which is attached to the shaft of the driving motor.

The driving motor is series type, without starting resistance, and is always connected by a switch with one of two armatures, so that when the E motor is powered, the blower runs in relation to the rotation speed (air flow rate corresponds with the drive level). When the E motor is unpowered, the fan blower rotates slowly powered by voltage generated due to the remanent magnetism of the unpowered rotating armature.

	Direct Current Motor	Fan blower
Manufacturer	Siemens-Halske	Siemens-Halske
Model	GS 10 a	T v 4
Rated Power	3.2/6.8 kW	550/8250 m³/hour
Number of RPM	1400/1800 RPM	1400/1800 RPM
Weight	180 kg	50 kg
Current	18/24 A
Voltage	220/340 V

Cooling pump.

When diesel engines are turned off (submerged drive), the cooling pump takes over the functions of the port and/or stb. cooling water pumps driven by the diesel engines to provide cooling for following installations in the aft torpedo room and E motor room:

Propeller shaft stuffing boxes port and stb.

Main thrust bearing port and stb.

Each of 2 E motor air coolers port and stb.

E motor bearing port and stb.

Page 154	B. Machinery	U-Boat Type VIIC

13	II. Auxiliary Machinery for Propulsion	U-boat Information

The cooling pump is tested under a pressure of 12 at and along with connected installations can function at construction diving depth.

	Direct Current Motor	Pump
Manufacturer	A.E.G.	Klein, Schanzlin & Becker
Model	A W V 57
Weight	86 kg	42 kg
Current	49/47 A
Number of RPM	2000/2400 RPM	2000/2400 RPM
Rated Power	4.4/6.6 kW (total input)	250/384 liters/minute
Voltage	110/170 V
Test pressure		12 kg/cm²

U-Boat Type VIIC	B. Machinery	Page 155

U-boat Information	III. Draining and Flooding	1

III. Draining and Flooding.

1) Main drainage installation.

The main drainage installation consists of a main drain line with suction piping and the main drain pump. The main drain line leads from the E motor room to the forward torpedo room.

The main drain pump is a self-priming, reversible, 2-stage, centrifugal pump, vertical design with driving motor positioned above. A vacuum pump is positioned below the rotor, which can remove air from the suction piping.

The drain line can be flooded by means of the open-check-close valve in the "forward and/or aft" drain connection. Vent valves are installed in the drain line forward in the control room and in aft torpedo room.

The main drain pump delivers capacity of ~1300 liters/minute against heads up to 15 meters and ~500 liters/minute against heads up to 100 meters.

The main drain pump should be used to drain large quantities of water. It can drain from:

All to and from sea

Regulating tanks and regulating and reserve fuel oil tanks

Trim tanks

Torpedo compensating tanks

Waste water tanks

Periscope shafts

Munitions magazine

Store room

2) Auxiliary drainage installation.

The auxiliary drain and trim pump in control room is provided for draining small quantities of water and for trimming operations. It is an electric driven, double-piston pump with capacity ~360 liters/minute. Its draining options are the same as for the main drain pump. The stb. and port regulating tanks can be emptied by means of the main drain pump, auxiliary drain and trim pump or even compressed air.

Page 156	B. Machinery	U-Boat Type VIIC

2	III. Draining and Flooding	U-boat Information

		For draining the bilges at greater depth there is a check valve of open-check-close type on the discharge line of the main drain pump provided (in the pressurized valves casing of the main drain pump). Hence when the open-check-close valve is in the open position, bilges can be drained using the auxiliary drain pump through the flooding and drainage manifold to the regulating tanks and/or the regulating and reserve fuel oil tanks.
		The auxiliary drain and trim pump can discharge to the sea, upper deck wash line, main ballast tank 3, trim tanks, regulating tanks and the regulating and reserve fuel oil tanks.

3) Hand drainage installation.
		A portable hand drain pump is provided on board as a hand drainage installation, which can be used to drain resting water from bilges, bunkers and tanks.

4) Artificial flooding installation.
		The auxiliary drain pump can be used for artificial flooding. A fire extinguishing connection is provided in the deck wash line leading to the upper deck. The munitions magazine and container can be flooded by means of the hose connected there. Regulating tanks and regulating and reserve fuel oil tanks can be flooded by means of the main and auxiliary drain pumps.

5) Natural flooding installation.
		Natural flooding refers to flooding the rooms through hull valves without using the pumps.
		Natural flooding installations are provided for:
		a) Regulating tanks and regulating and reserve fuel oil tanks
		b) Torpedo compensating tanks
		c) Munitions magazine and munitions container
		Regulating tanks and regulating and reserve fuel oil tank flooding takes place by means of the flooding and drainage manifold either through the hull valve from sea or for accurate flooding through the hull valve with water meter.

U-Boat Type VIIC	B. Machinery	Page 157

U-boat Information	III. Draining and Flooding	3

		Torpedo compensating tanks 1, 2, and 3 are flooded from sea through the hull valves with water meter in the aft torpedo room or the forward torpedo room respectively.
		Flooding the munitions magazine and container for explosive charges in the officers and chief petty officers room as well as the container for flare charges takes place through a hose connection from the hull valve in the control room.
		For flooding options and flooding times for a sunken boat see section A IX.

Page 158	B. Machinery	U-Boat Type VIIC

1	IV. Sea, Wash, and Fresh Water Installations	U-boat Information

IV. Sea, Wash, and Fresh Water Installations.

1) Sea water installation.
		To provide sea water collection in the galley, there is a branch off the cooling water manifold in the diesel engine room, which leads to the valve and a tap in the wash sink.
		The warm sea water installation branches off from cooling water head tank in the conning tower casing and leads to the washbasins in both W.C.s and to the wash sink in the galley.
		The discharge line of the auxiliary drain and trim pump branches off to the deck wash line. A shower head can be connected to this line, attached to the net protector, and stowed again after usage.

2) Wash water installation.
		Wash water is stored in the following tanks:
		1 wash water tank (listening room)
		1 wash water daily supply tank (aft W.C.)
		As reserve tanks there are:
		Torpedo compensating tank 1
		Torpedo compensating tank 2
		Wash water tank and wash water daily supply tank are connected to the fresh water filling and extracting line. Tanks are filled through the intake at the upper deck.
		The hand fresh water pump is used for filling the wash water daily supply tank from the wash water tank. A hand wash water pump provided in the forward W.C., to which a suction line can be switched by the selector cock to the wash water tank or to torpedo compensating tank 2. Extracting the wash water from torpedo compensating tank 1 takes place by means of compressed air.

3) Fresh water installation.
		Fresh water is stored in 3 tanks (3.870 m³) situated in:
		Fresh water tank 1: Galley, port, under the floor
		Fresh water tank 2: Control room, port
		Fresh water tank 3: Officers room, stb.

U-Boat Type VIIC	B. Machinery	Page 159

U-boat Information	IV. Sea, Wash, and Fresh Water Installations	2

		The fresh water tanks are connected to the filling and extracting line through the fresh water selector cock. The line leads through the hull valve at the upper deck and inside the hull branches off to the emergency drain connection. The hand fresh water pump in the galley takes suction from selected tank and discharges through the control valve either directly to the tap in wash sink or through the filter.
		The water supplied by the distilling unit in the control room is collected in the distillate tank and is moved through the control valve either directly or through the filter to fresh water tank 1 in the galley.
		All fresh and wash water tanks have sounding pipes and dip sticks.

Page 160	B. Machinery	U-Boat Type VIIC

1	V. Ventilating Systems	U-boat Information

V. Ventilating Systems.

		The ventilating system is used to exchange the air inside the boat and to extract gases generated while charging the batteries. The intake and exhaust air fans in the diesel engine room, which can run in parallel or separately, are used to ventilate through the intake and exhaust ducts. Each fan's performance is 2600 – 2700 m³/hour with pressure head at 22 – 24 mm H₂O.
		The intake duct on the stb. side and exhaust duct on port side run throughout the boat from the aft torpedo room to the forward torpedo room.
		Intake and exhaust air ducts are connected by air trunks which lead to the aft part of the conning tower casing through the foot valve in the diesel engine room and the head valve which can be closed from the control room.
		In the diesel engine room the intake and exhaust ducts are interconnected through the compartment air exhaust selector and the compartment air intake selector to enable running one or both fans in several configurations (see Machinery Sketchbook).
		In each compartment there are branches from the intake air duct ending in a ventilation grille. One branched duct leads to the conning tower. There is also a duct leading through the radiator to the attack periscope well. The ducts leading from the exhaust duct are led to the lowest place in the compartment (CO₂ is heavier than air) and are provided with gate valves. Carbon dioxide absorbents are connected in the E motor room, control room and in forward torpedo room. Emergency oxygen feed ducts are also connected to the exhaust air duct in the diesel engine room, control room and in forward torpedo room.
		The ventilation of battery cells takes place through ducts leading to the exhaust duct, which are also provided with grilles for natural ventilation. Shafts with grilles leading from the compartment to the battery cells serve as air intakes.
		In aft torpedo room as well as in forward torpedo room there are flexible connections to the Eto charging units.
		The intake and exhaust air ducts when passing through bulkheads, are equipped with watertight and/or pressure resistant gate valves, which can be operated from both sides of the bulkhead.

U-Boat Type VIIC	B. Machinery	Page 161

U-boat Information	VI. Heating Installations	1

VI. Heating Installations.

There are two separate heating installations provided:

a) steam heating system

b) electrical heating

The steam heating system consists of steam intake and exhaust installations. In harbor the steam is taken from the depot ship through a flexible pipe. In the boat, next to the steam hull valve, a steam heat reducing valve with pressure meter and safety valve are installed. The operational pressure is 3 at. There are 21 radiators of different sizes installed. Each radiator has an inlet and outlet valve.

To drain the water in the steam exhaust pipe, draining water separators are installed in the diesel engine room and in the forward torpedo room. The condensed steam is exhausted through the hull valve and flexible pipe to the depot ship or land connection.

The arrangement of radiators is as follows:

E motor room	4	Heads	Heating Surface	2	Heads	0.615 m²
			"	2	"	0.812 m²
Diesel engine room	4	"	"	4	"	1.608 m²
Petty officers room	1	"	"	1	"	0.745 m²
Control room	3	"	"	1	"	0.412 m²
			"	1	"	0.250 m²
			"	1	"	0.745 m²
Radio room	1	"	"	1	"	0.260 m²
Listening room	1	"	"	1	"	0.260 m²
Officer and chief petty officers room	3	"	"	1	"	0.278 m²
			"	1	"	0.250 m²
			"	1	"	0.745 m²
Forward torpedo room	4	"	"	4	"	0.804 m²

The electric heating installation consists of 9 portable electric resistance heaters. Each heater is provided with a cable and plug and can be connected to the electric power installation in each room. The heater can run at one of 3 levels.

Page 162	B. Machinery	U-Boat Type VIIC

2	VI. Heating Installations	U-boat Information

The heater's performance is 1.5 – 3.5 kW at 13.6 – 20.6 A current.

The following rooms have outlets for heaters:

E motor room	2	Outlets
Diesel engine room	2	"
Petty officer room	2	"
Control room	1	"
Conning tower	1	"
Radio room	1	"
Listening room	1	"
Officer and chief petty officers room	3	"
Forward torpedo room	3	"

U-Boat Type VIIC	B. Machinery	Page 163

U-boat Information	VII. Lubricating Oil Installations	1

VII. Lubricating Oil Installations.

The lubricating oil installation consists of:

Reserve lubricating oil tanks 1 and 2

Lubricating oil collecting tanks port and stb.

The lubricating oil pumps of the Diesel engines

The auxiliary lubricating oil pump

The hand lubricating oil pump

The hand dirty lubricating oil pump

The dirty lubricating oil tank

The lubricating oil consumption tank

The filling and transfer lines

The purification system.

Reserve lubricating oil tanks are located below the diesel engines and have a total capacity of 6.59 m³. Both tanks have sounding pipes and pipe for filling and draining purposes.

The lubricating oil collecting tanks are located one after another between the diesel engines. Each tank (0.8 m³) is connected with the suction pipe of the associated lubricating oil pump. Both tanks have connections to the suction pipe of the auxiliary lubricating oil pump and hand lubricating oil pump. The suction pipe of the auxiliary lubricating oil pump can be used as a filling line. Each collecting tank is connected to the lubrication oil return line of each diesel engine and to the selector cock of the suction pipe of the hand dirty lubricating oil pump. Sounding pipes provided for sounding the tanks.

The dirty lubricating oil tank is located aft of both collecting tanks. Its capacity is 0.4 m³ and is connected through the selector cock to the hand dirty lubricating oil pump.

Loading of lubricating oil takes place through the hull valve at the upper deck either gravitationally to the reserve and collecting lubricating oil tanks or by means of auxiliary or hand lubricating oil pump through the appropriately switched valves and cocks. The reserve and collecting lubricating oil tanks can be also pumped out to the upper deck using both these pumps.

Page 164	B. Machinery	U-Boat Type VIIC

2	VII. Lubricating Oil Installations	U-boat Information

		The lubricating oil consumption tank can be filled with the hand pump. Its capacity is 26 liters.
		The purification system is connected through 2 dirty and clean oil manifolds with the collecting and dirty lubricating oil tanks.

U-Boat Type VIIC	B. Machinery	Page 165

U-boat Information	VIII. Fuel Oil Installations	1

VIII. Fuel Oil Installations.

		The fuel oil installation consists of:
		Inside pressure hull:
		Fuel oil tank 1 (inboard) (petty officers room)
		Fuel oil tank 2 (inboard) officers and chief petty officers room)
		Fuel oil collecting tank (Diesel engine room)
		Fuel oil gravity tank (Diesel engine room).

		Outside pressure hull:
		Main ballast and reserve fuel oil tank 2 port and stb.
		Main ballast and reserve fuel oil tank 4 port and stb.
		Regulating and reserve fuel oil tank 1 port and stb.

		The fuel oil in all tanks – with the exception of regulating and reserve fuel oil tank 1 port and stb. - is transferred by means of sea water.
		The inboard tanks have capacity of 70.70 m³, the outboard tanks have a capacity of 59.00 m³. Total capacity is 129.70 m³. All tanks have manholes and have – except for regulating and reserve fuel oil tank 1 port and stb – the following connections:
		1 connection for filling and delivery line
		1 connection for compensating water line
		1 connection for test line
		1 connection for vent line
		The fuel oil in regulating and reserve fuel oil tank 1 port and stb. is transferred only by means of low pressure air at 0.5 at. The tanks have following connections:
		1 connection for filling and delivery line
		1 connection for low pressured air through the reduction valve from 13 at to 0.5 at.
		The inboard fuel oil tanks 1 and 2 have also connections for sounding pipes and the connections between compensating water line and valve box with excess and negative pressure relief valves.
		The fuel oil collecting tank is used to collect leaked-off oil.
		Draining can be done by means of hand cooling water pump or by the hose connection and hand draining pump.

Page 166	B. Machinery	U-Boat Type VIIC

2	VIII. Fuel Oil Installations	U-boat Information

		A four way valve is provided for filling and extracting fuel oil from the gravity tank located in the upper part of diesel engine room. The venting and drain pipes lead through the funnel to the collecting tank. The gravity tank has a capacity of 0.73 m³ and has a sight glass on its front side. The fuel oil line leads from the gravity tank through the fuel oil meter and control cock and then branches to fuel oil feed pumps attached to each diesel engine.
		The filling and delivery line leads from the screw joint connection on the upper deck, through the hull valve and strainer to the main distributing manifold. This manifold is connected through the fuel oil control cock 1, fuel oil meter, strainer and fuel oil control cock 2 with the tank manifold. From this manifold the line branches and through the valves leads to the top of the inboard and outboard fuel oil tanks.
		The fuel oil is delivered by means of pressurized water passing down from the cooling water head tank on the upper deck to the bottom of each fuel oil tank. The compensating water line branches to the inboard tanks through the cut-off valves and to the outboard tanks through the selector valve. In the diesel engine room the compensating water line is connected with hand cooling water pump.
		The tanks are filled by gravity or by means of a pump on land. In exceptional cases the auxiliary lubricating oil pump can be used for filling the tanks (pumping fuel oil from another boat to the boat at sea).

U-Boat Type VIIC	B. Machinery	Page 167

U-boat Information	IX. E Installations	1

IX. E Installations.

1) E motors.
		The E motors working as electric motors drive the propellers and working as a generators charge the batteries. They are fan cooled, encapsulated, direct current, double armature, with compound windings and commutating poles. The motor is built from two parts, casing with installed windings, which are bolted together. There are also two armatures installed on the same shaft inside. In the upper parts of casings are cold air inlets and warm air outlets. Bottom parts up to the bottom edge of the shaft are water resistant and at the lowest points draining cocks are provided.
		Each double armature motor has 2 x 8 main poles and the same amount of commutating poles. All poles are bolted to the inner side of the rotating yoke. The shaft has installed two armatures and runs in two slide oil ring lubricated bearings. The bearing on the diesel engine side is built as a thrust bearing for absorption undesirable thrust.
		The bearings of the E motors are cooled by sea water. During surfaced drive the cooling system is fed by the diesel engine cooling pump and while submerged, by the cooling pump.
		A fan blower is attached to the casing. It draws fresh air from the E motor room and blows from above into the both parts of the motor.
		The warm air escapes through outlets in the upper parts of bearing casings and is directed to air coolers, which are installed between the E motors.

2) Batteries.
	On board are:
	Battery 1 and 2
	8 batteries powering emergency lights
	8 batteries powering hand lanterns

Page 168	B. Machinery	U-Boat Type VIIC

2	IX. E Installations	U-boat Information

For the specifications of battery 1 and 2 see paragraph B.I.2.

The emergency lights and portable lamp batteries can be charged at the charging console in the E motor room from the lighting network. Each battery consists of 2 cells. Battery voltage is 4 V, capacity on the discharging current of 0.75 A is 10.5 Ah.

3) Main switchboards.

Main switchboards with lever switches.

The stb. main switchboard is connected through the aft battery automatic circuit breaker to the aft battery, the port main battery switchboard is connected through the forward battery automatic circuit breaker to the forward battery. Each battery automatic circuit breaker has following settings:

overload current of 5000 A in 6 seconds

short circuit current of 13000 A.

The main switchboards are built from an iron framework, which supports switches, control and measurement equipment necessary for driving and charging. The order of the switches on each switchboard from left to right for both E motors is as follows:

1	Starting relay
2	Motor automatic circuit breaker
1	Main battery switch with charging connection
1	Drive direction switch - two part
1	Motor - series-parallel - switch
1	Battery - parallel-serial - switch

Above the switches are installed measurement devices and the switch for the fan blower motor. A double motor field rheostat is installed on the right side of each switchboard.

Main battery switch is two-pole. When switched on, the battery automatic circuit breaker is connected with main switchboard. The switch is operated by an isolated handle, which is mounted on two arms. In online state, the handle is in the upper position, when off – handle rests in the horizontal position on the rubber holders.

Above are charging terminals, accessible through a flap on the casing.

U-Boat Type VIIC	B. Machinery	Page 169

U-boat Information	IX. E Installations	3

		Drive direction switch is also two-pole and is used to toggle current direction in the armatures to change the motors direction of rotation. The switch is built from two parts. Both parts are operated together. By severance of the connection muff, each part of switch can be operated separately. For forward drive, the switch is in the upper position, for reverse drive, in the bottom position. When off, the switch is in the middle position.

		Motor - series-parallel - switch is three-pole. The middle pole is used to make equalizer connection between armatures and series winding when armatures are connected in parallel. In the upper position the armatures of the motor are connected in parallel. In the bottom position the armatures are connected in series.
		In the second case, the arm of the switch handle, by closing auxiliary contacts bridges the relay contacts and prevents activation of the starting relay, when the battery - parallel-serial - switch is in the parallel position.

		Battery - parallel-serial - switch is a three-pole, toggle switch constructed for 1500 A of continuous current. In the upper position the batteries are in series, in the bottom position they are connected in parallel.

		Motor automatic circuit breaker is a one-pole contactor connected with the armature windings. The automatic circuit breaker can be turned on and off manually. For automatic triggering two separate magnetic contactors and two trigger levels are provided for short circuit and overload current.
		First is set at 3000 A of short circuit current
		Second at 1100 A overload current in 4 seconds.

		Starting relay normally works fully automatic, but in case of damage, it also can be manually operated. This contactor limits too high starting current. Immediately after turning on the drive direction switch the contactor opens and in its off-state connects the starting resistor into the E motor armature circuit. The contactor operation

Page 170	B. Machinery	U-Boat Type VIIC

4	IX. E Installations	U-boat Information

latency is adjustable. When the contactor contacts close (the current has gone down, the voltage is low), the starting resistor is short-circuited. The auxiliary contacts are simultaneously closed and the indicator lamp lights.

All maneuver switches are connected in the starting relay control circuit so that when the motor main circuit opens, i.e. by turning off any maneuver switch, the staring relay will open. Any modification of the main motor circuit results in connecting the starting resistor.

Using the motor - series-parallel - switch and battery - parallel-serial - switch three drive speed ranges corresponding three voltage ranges can be set (see E Sketchbook)

1.	Batteries in parallel, armatures in series
2.	Batteries in parallel, armatures in parallel
3.	Batteries in series, armatures in parallel

Within these three ranges, further adjustments can be done by changing the current in shunt windings using the double motor field rheostat.

Main switchboards with rotary switches.

Type VIIC U-boats are equipped with main switchboards with rotary switches provided by A.E.G. Company, Berlin.

overload current of 6000 A in 10 seconds

short circuit current of 12000 A

The main switchboards are built from iron framework, which supports switches, control and measurement equipment necessary for driving and charging. The order of the switches on each switchboard from left to right for both E motors is as follows:

U-Boat Type VIIC	B. Machinery	Page 171

U-boat Information	IX. E Installations	5

1	Main battery switch with charging connection below
1	Starting relay with with indicator lamp
1	Field switch 2
1	Drive direction switch
1	Field switch 1 with indicator lamp
1	Motor - series-parallel - switch
1	Battery - parallel-serial - switch

Above the switches are installed the fan blower motor switch, board illumination switch, silent running drive switch, and measurement devices.

The speed controller is installed on the right side of each switchboard. Timed relay and auxiliary relay are installed below the measurement devices and above the drive direction switch.

Main battery switch is two-pole. When switched on, the battery automatic circuit breaker is connected with main switchboard. The switch is operated by an isolated hand wheel. By rotating the hand wheel to the right, the switch turns on, rotating to the left turns the switch off. In the bottom part are charging terminals, accessible through flap on the casing.

Drive direction switch is five-pole and is used to toggle the current direction in the armatures to change motors direction of rotation. By turning the hand wheel to the right, the motor runs forward, by turning to the left, the motor runs backward. The switch is turned off when the hand wheel is the middle position. The drive direction switch is interlocked with the motor field switch so that the E motor cannot be turned on, when the field switch is turned off.

Motor - series-parallel - switch is a four-pole toggle switch. Turning the hand wheel to the right, causes the armatures to be connected in series and the equalizer line is disconnected. When the hand wheel is turned to the left, the armatures are connected in parallel and the equalizer line is connected. By means of auxiliary contacts the circuits of the timed relay and silent running drive switch are closed.

Page 172	B. Machinery	U-Boat Type VIIC

6	IX. E Installations	U-boat Information

Battery - parallel-serial - switch is a double three-pole toggle switch. Turning the hand wheel to the right, causes parallel connection of the batteries. When the hand wheel is turned to the left, the batteries are connected in series. By means of auxiliary contacts the circuits of the timed relay and silent running drive switch are closed.

Starting relay is a two-pole circuit breaker. It normally works fully automatically, but in case of damage, it also can be manually operated. This contactor limits too high starting current. Immediately after turning on all switches or after expiration of the adjustable (to 1 second) timeout the contactor opens and in its off-state connects the starting resistor into the E motor armatures circuit. When the contactor contacts close (the current has gone down, the voltage is low), the starting resistor is short-circuited. When the main current circuit opens, i.e. by turning off any of maneuver switches, the starting relay is opened and the starting resistor is connected.

When the relay is damaged, the starting resistor can be short-circuited manually. In that case before setting the maneuver switches, the starting relay must be turned off. When starting relay is activated, the indicator lamp lights up.

Using the motor - series-parallel - switch and battery - parallel-serial - switch three drive speed ranges corresponding three voltage ranges can be set (see E-Sketchbook).

1.	Batteries in parallel, armatures in series
2.	Batteries in parallel, armatures in parallel
3.	Batteries in series, armatures in parallel

Within these three ranges, further adjustments can be done by changing the current in shunt windings using the double motor field rheostat – the speed controller. It also can be used to control the output voltage of the E motor while charging the battery. Each single rheostat is connected in series with single shunt winding of the double-armature machine, then they are connected in parallel with each other.

U-Boat Type VIIC	B. Machinery	Page 173

U-boat Information	IX. E Installations	7

4) Auxiliary switchboards and power distribution.
		The power distribution and the lighting distribution is done by means of the auxiliary switchboards. Auxiliary switchboard 1 is installed on port side of the E motor room, auxiliary switchboard 2 is installed on the stb. side of control room.
		By means transfer switches the auxiliary switchboards can be connected either to the battery automatic circuit breaker or the corresponding main switchboard. The connections with main battery bus and with the main switchboard auxiliary bus are fused with 430 A cartridge fuses. Each switchboard is divided into the main power section and regulated voltage section. The main power section powers the equipment, which can work with variable voltage within range 110-170 V. The regulated voltage section powers equipment which works at a fixed voltage of 110 V. All circuits are fused with cartridge fuses.
		The fixed voltage in the regulated voltage section is maintained by an automatic voltage regulator. In case of damage, the voltage regulator can be hand operated.

	Auxiliary switchboard 1 feeds the following circuits:
	Regulated section
		Radio and UT switchboard
		Gyro compass and TDC converter
		Port light group 2
	Unregulated section
		Auxiliary switchboard 1a
		Aft room (power port) group 2
		Power port (forward) group 4
		Air compressor 1
		Air compressor 2
		Diesel engine room (power port) group 3

	Auxiliary switchboard 2 feeds the following circuits:
	Regulated section
		Lights stb. (aft) group 1
		Ordering and reporting installations

Page 174	B. Machinery	U-Boat Type VIIC

8	IX. E Installations	U-boat Information

		Lights (stb.) forward group 3
	Unregulated section
		Power stb. (aft) group 1
		Auxiliary drain and trim pump
		Power stb. (forward) group 5
		Main drain pump
		Diesel engine room (power port) group 3

5) Electric equipment.
	a)	E drive motors and their current feed (power supply).
		1. Pumping

Driving motor	Detailed Description	Circuit	Power Supply
Main drain pump	B.II 1 e	Compound with Series starting winding	Aux. switchboard 2 (power)
Aux. drain and trim pump	B.II 1 d	Compound	Aux. switchboard. 2 (power) power port (forward) group 4
Air compressor 1 and 2	B.II 1 e	Compound with Series starting winding	Aux. switchboard. 1 (power)
Auxiliary lubricating oil pump	B.II 2 a	Compound with Series starting winding	Diesel engine room (power port) group 3
Auxiliary cooling water pump	B.II 2 b	Compound with Series starting winding	Diesel engine room (power port) group 3

Cooling pump	B.II 3 b	Compound with Series starting winding	Power stb. (aft) group 1
Lubricating oil pump	B.II 1 g	Compound with Series starting winding	Power port (forward) group 4 power stb. (forward) group 5
Drive for distilling unit	B.II 1 j	Shunt	Power port (forward) group 4 or Ordering and reporting installations
Drive for Refrigeration plant	B.II 1 n	Compound	Power stb. (forward) group 5
Drive for lubricating oil purification system	B.II	Compound	Diesel engine room (power port) group 3
2. Diving Planes and Main Rudder Driving Motors.
Aft dive plane driving motor	B.II 1 a	Compound	Power stb. (aft) 1 or aft room (power port 2)

U-Boat Type VIIC	B. Machinery	Page 175

U-boat Information	IX. E Installations	9

Driving motor	Detailed Description	Circuit	Power Supply
Forward dive plane driving motor	B.II 1 a	Compound	Power port (forward) 4a or power stb. (forward) 5a
Main rudder driving motor	B.II 1 a	Compound	Power stb. (aft) or aft room (power port 2)
3. Air fans.
Intake and exhaust air fan	B.II 1 f	Compound	Diesel engine room power port 3


	b)	Rotary converters and associated equipment.

Gyro Compass Converter
Manufacturer:	Anschütz & Co., Kiel
Construction:	Multiple-armature converter
Power supply:	Auxiliary switchboard 1 and 2
Model:	A 220 T

Driving motor:	Generator:
	Single-phase Gen.	Medium-freq. Gen.	Direct current Gen.
Voltage: 110 V	50 V	112 V	220 V
Rated current: 19 A	17.2 A	2.4 A	1.4 A
RPM: 3330	3330	3330	3330
Frequency:	55.5 cycles/second	0.7 cycles/second
Power factor:	0.5	0.7
Rated power:	0.86 kVA	0.5 kVA	0.3 kVA

Transmitter Converter
Manufacturer:	Telefunken
Construction:	Multiple-armature converter
Power supply:	Radio switchboard
Model:	TFG 110/3

Driving motor:	Generator: (Model TFG 412/7)
Voltage: 110 V	400/1500 V DC 280 AC
Rated current: 13 A	0.3 A 0.3 A 1 A
RPM 3000	3000
Frequency:	100 cycles/second
Power factor:	0.8

Page 176	B. Machinery	U-Boat Type VIIC

10	IX. E Installations	U-boat Information

Rated Power: 1.1 kVA

0.12/0.45 kVA

Radio Converter 1
Manufacturer:	Conz, Altona
Construction:	Two-armature converter
Power supply:	Radio switchboard
Model:	ENG 54/4 T

Driving motor:	Generator:
Voltage: 110 V	225 V
Rated current: 65 A	27 A
RPM 1500	1500
Power factor:	0.8
Frequency:	50 cycles/second
Rated power:	6 kVA

Radio Converter 2
Manufacturer:	Conz, Altona
Construction:	Two-armature converter
Model:	ENG 34/4 T
Power supply:	Radio switchboard

Driving motor:	Generator:
Voltage: 110 V	225 V
Rated current: 21 A	6.7 A
RPM 1500	1500
Power factor:	0.8
Frequency:	50 cycles/second
Rated Power:	1.5 kVA

Radio Converter 3
Manufacturer:	Hansa, Altona
Construction:	One-armature converter
Model:	GW 7/125 Sp
Power supply:	Radio switchboard

U-Boat Type VIIC	B. Machinery	Page 177

U-boat Information	IX. E Installations	11

Driving motor:	Generator:
Voltage: 110 V	220 V
Rated Current: 5 A	1.36 A
RPM 1000	1000
Power factor:	0.8
Frequency:	50 cycles/sec
Rated Power: 0.35 kW	0.3 kVA

UT Converter
Manufacturer:	Conz, Altona
Construction:	Two-armature converter
Model:	EHG 03 BT
Power supply:	Radio switchboard

Driving motor:	Generator:
Voltage: 110 V	120 V
Rated Current: 9 A	4.2 A
RPM 5150	5150
Power factor:	0.9
Frequency:	2060 cycles/second
Rated Power:	0.5 kVA

Shallow and Deep Echo Sounding Converter
Manufacturer:	Conz, Altona
Construction:	One-armature converter
Model:	EHG 25 T
Power supply:	Radio switchboard

Driving motor:	Generator:
Voltage: 110 V	100 V
Rated Current: 1.1 A	7 A
RPM 2500	2500
Power factor:	0.9
Frequency:	1500 cycles/second
Rated Power:	0.7 kVA

Page 178	B. Machinery	U-Boat Type VIIC

12	IX. E Installations	U-boat Information

TDC Converter
Manufacturer:	S.S.W., Berlin
Construction:	Two-armature converter
Model:	VG 86 A 6/VFEA 66 b
Power supply:	Auxiliary switchboard 1

Driving motor:	Generator:
Voltage: 110 V	55 V
Rated Current: 17 A	45.5 A
RPM 1500	1500
Power factor:	0.35
Frequency:	50 cycles/second
Rated Power:	0.25 kVA

2 Eto-Charging Units
Manufacturer:	S.S.W., Berlin
Construction:	Two-armature converter
Model:	VG 46 A 8 - 4
Power supply:	Auxiliary switchboard 1

Driving motor:	Generator:
Voltage: +30 - 40 - 10 V KBDB	110/150 DB 170 KB
Rated Current: 35/20 A	5 A
RPM 1500/2600	1500/2600

Rotary amplifier (for the gyro angle setting gear)
Manufacturer:	S.S.W., Berlin
Construction:	Three-armature converter
Model:	VG 46 A 8 - 4
Power supply:	Auxiliary switchboard 1

Driving motor:	Generator:
	Coarse setting gear Generator	Fine setting gear Generator
Voltage: 110 V	130 V	35 V
Rated Current: 6.44 A	3 A	3 A
Rated Power: 0.5 kW	0.39 kW	0.105 kW
RPM: 2000	2000	2000
Excitation Voltage: 110 V	110 V	110 V

U-Boat Type VIIC	B. Machinery	Page 179

U-boat Information	IX. E Installations	13

Ordering and reporting installations.

General information and power supply.

The ordering and reporting system is composed of the following distinct installations:

1.	Engine order telegraph system
2.	Shaft revolution indicator system
3.	Rudder order telegraph and rudder angle indicator system for main rudder
4.	Dive planes angle indicator systems
5.	Alarm bell and flashing light system
6.	Compartment ready indicating system (for each room)
7.	Hull closure indicating system
8.	Torpedo orders indicator system
9.	Radio broadcast and announcement system (see paragraph V b)

The following systems are powered through ordering and reporting systems fuse box in control room (110 V, direct current):

1.	Rudder order telegraph system
2.	Rudder angle indicator system
3.	Engine telegraph system
4.	Alarm bell and flashing light system
5.	Hull closure indicating system
6.	Speed log system

The fuse box is connected through the selector switch (ordering and reporting system feed switch) either to auxiliary switchboard 2 ordering and reporting power line branch or to the port light circuit.

The hull closure indicating system is powered through a feed switch (not switchable) from ordering and reporting power line branch (auxiliary switchboard 2)

Shaft revolution indicator system is powered by transmitters coupled to the shaft lines, acting as direct current generators.

Torpedo orders indicator system is powered by (55 V alternating current) TDC converter located in the E motor room, which is powered from auxiliary switchboard 1.

Page 180	B. Machinery	U-Boat Type VIIC

14	IX. E Installations	U-boat Information

Engine order telegraph system.

The engine order telegraph is used to pass the drive level orders for the diesel engines and E motors. The common feed circuit (third junction in the ordering and reporting systems fuse box) is further separated into two parallel connected port and stb. installations. Each installation consists of a transmitter, receiver with indicator unit and receiver selector switch in the conning tower and in the control room and one receiver indicator with answering transmitter in the diesel engine room and one in the E motor room. In the control room are also two transmitter selector switches - one for each installation. The receiver selector switch connects the associated transmitter with:

Position 1:	Receiver in the diesel engine room
Position 2:	Receiver in the diesel engine room and E motor room
Position 3:	Receiver in the E motor room

The transmitter selector switch enables the following connections:

Position 1:	Control room unit activates conning tower unit reads along
Position 2:	Conning tower unit activates, control room unit reads along
Position 3:	Control room unit activates, conning tower unit is disconnected.

A two-pole rotary cut off switch is provided in the selector switch casing. The switch is used to enable noiseless operating mode, when the buzzers in conning tower and control room, bells in diesel engine room and horns in E motor room are disabled. Only signal lamps are connected with receivers. There is a flashing circuit provided for each installation.

Shaft revolution indicator system.

The shaft revolution indicator system is used to show present, average revolution speed (revolutions per minute) and the revolution direction of the propeller shafts. It has two separate port and stb. installations. A transmitter is provided in the aft torpedo room and E motor room for each of the two shafts. The transmitter is coupled with the electric motor shaft by a chain and sprocket. Each transmitter is connected with receivers in the following rooms:

U-Boat Type VIIC	B. Machinery	Page 181

U-boat Information	IX. E Installations	15

E motor room

Diesel engine room

Control room

Conning tower

Listening room

A control box is provided in the control room for port and stb. installation, by which every single receiver can be cut off.

Both receivers for port and stb. sides in conning tower are provided with self-illumination, which is powered from the port light group.

Rudder order telegraph and rudder angle indicator system.

The main rudder installation consists of the rudder order telegraph and rudder angle indicator systems.

The rudder order telegraph is used to pass steering commands from the control room to the manual steering station in the aft torpedo room.

The rudder angle indicator system is used to pass main rudder current position to the receivers located in control room, aft torpedo room, bridge, conning tower, diesel engine room and E motor room.

The installation consists of the following parts:

Aft torpedo room:	1	Rudder telegraph receiver with built-in rudder angle indicator
	1	Call bell for the rudder telegraph receiver
E motor room:	1	Rudder angle receiver
Diesel engine room:	1	Rudder angle receiver
Control room:	1	Rudder telegraph transmitter with built-in rudder angle indicator with turnable buzzer
	1	Fuse and terminal box
Conning tower:	1	Rudder angle receiver with adjustable illumination.
	1	Control box with 3 switches
Bridge:	1	Rudder angle receiver with adjustable illumination and heating (water/pressure-resistant)
Listening room	1	Rudder angle receiver

Three switches of the control box in conning tower are used to cut the bridge receiver out of the system, and to turn on and off the heating and to regulate its

Page 182	B. Machinery	U-boat Type VIIC

16	IX. E Installations	U-boat Information

and self-illumination (tube lamp).

The position of the main rudder is transmitted electrically using the voltage divider principle.

Dive plane angle indicator system.

The plane angle indicator system is used to pass the current angle of the forward and aft dive planes to receivers located in the control room and the conning tower.

The installation consists of the following parts:

1	Rudder plane angle transmitter sender for aft dive planes
1	Rudder plane angle transmitter for forward dive planes

Control room:

1	Rudder angle receiver for forward dive planes
1	Rudder angle receiver for aft dive planes
1	Terminal and fuse box

Conning tower:

1	Double receiver for forward and aft dive planes

Alarm bell and flashing light system.

The purpose of the installation is to inform the crew, that they must assume diving stations as fast as possible. There are alarm bells and flashing lamps in following rooms.

Alarm bell - one per room:

E motor room

Diesel engine room

Petty officers room

Control room

Officer and chief petty officers room

Forward torpedo room

Because of loud noise in diesel engine room there are also 7 lamps in port and 5 lamps in stb. lights group controlled by flashing circuit powered by port and stb. aft lights group.

The system is operated by alarm activation switches located in conning tower and control room. These switches are made as transfer switches, so that the alarm can be turned on or off by one of these, and also turned off or on by the other.

U-Boat Type VIIC	B. Machinery	Page 183

U-boat Information	IX. E Installations	17

The alarm is initiated by operating one of these switches.

Compartment ready indicating system.

The system is used to report compartment readiness for diving through indicating lamps. An indicating lamp box with 5 lamps is installed in the control room on the forward stb side of the periscope well. When the compartment reports readiness for diving, the switch located in that room closes the circuit and the related indicating lamp highlights the word “Ready” on the indicating lamp box.

The switches for each room are located as follow:

E motor room	At the switchboard
Diesel engine room	On the forward bulkhead
Petty officers room	In the galley on the forward bulkhead
Officers and chief petty officers room	On the bulkhead of the provisions locker
Forward torpedo room	Over the tubes near the frame

Hull closure indicating system.

The hull closure indicating system is used to report state of the hull valves on the indicating lamp box. The box is installed on the forward stb. side of periscope well, under the compartment ready indicating lamp box. There are 5 indicating lamps, which are controlled by contact switches provided for the following valves:

For the outer exhaust gas valve port and starboard

" Diesel engine air intake upper valve

" intake air upper valve

" exhaust air upper valve

Vent valve indicating system.

Not installed

Page 184	B. Machinery	U-Boat Type VIIC

18	IX. E Installations	U-boat Information

10.

Torpedo orders indicator system.

The system is used to pass orders from the conning tower to the forward and aft torpedo rooms. The transmitter with answer receiver is installed in the conning tower, in the forward and aft torpedo rooms receivers with answer transmitters are provided. By means of the control box in control room, the conning tower can be connected with forward or with aft torpedo rooms.

Signal equipment.

General information and power supply.

The ordering and reporting power line (auxiliary switchboard 2) branches in the first fuse box into the running lights power line.

This line has the following terminals:

Steaming light with indicator lamp )
Side light stb. with indicator lamp )
Side light port with indicator lamp )	Each has a switch at the fuse box
Stern light on stem )
Stern light on conning tower )
All-round light )

These lights can be turned off and turned on by water-resistant switches (signal lamps switches) provided in conning tower. In the circuits of the side and steaming lights indicator lamps are connected in series after the switches in the fuse box. For settings "Bright", "Dim" and for turning off the stern lights, there is a dimming-resistor with indicator lamp and switch provided in conning tower. The stern light and indicator lamp is connected in series. By means of selector switch the stern light on stern or the stern light on conning tower can be connected with dimming-resistor.

For powering the steaming light and 24 V signal searchlight the following outlets are provided: water and pressure-resistant outlet on the bridge (with associated water-resistant switch located in conning tower) and water-resistant outlet with switch in the conning tower. The 24 V signal searchlight is connected through fuse box and transformer and powered from the

U-Boat Type VIIC	B. Machinery	Page 185

U-boat Information	IX. E Installations	19

TRU-switchboard located control room.

The power for the large 24 V searchlight is provided the same as for signal searchlight. In the conning tower there is a water-resistant outlet with switch installed.

Running lights.

The side lights are built into the bridge bulwark.

The steaming light is attached to the forward periscope by means of several brackets.

The hand-lamp used as an all-round light, which is attached to the top of forward periscope by means of several brackets, so it can be visible from all directions.

Between the switch and outlet of the all-round light is a mobile cable with key-switch, by which the light can by used for Morse signaling.

Searchlight equipment.

The 24 Volt signal searchlight is held by 2 handles and is controlled by means of a key. The dimming shutter consists of a moving tube, which covers up the light bulb. The outlets are installed in conning tower and on the bridge. Both associated switches are located in conning tower.

The 24 Volt searchlight can be set up on the port or stb. side of the bridge, in two mounting supports provided there.

Its dimming device consists of several slats, operated by hand lever. The water-resistant outlet is installed in conning tower.

Power load for boat purposes.

Boat lighting.

The boat lighting system is divided into three groups:

Light Group 1:	Light stb. aft, Power supply auxiliary switchboard 2
Light Group 2:	Light port " " " " 1
Light Group 3	Light stb. forward, " " " " 2

Page 186	B. Machinery	U-Boat Type VIIC

20	IX. E Installations	U-boat Information

Half of the lights of each room are always powered from different light group, so the failure of one light group or auxiliary switchboard doesn't lead to complete room light failure.

The night lighting is powered from light groups and in the following rooms consists of:

Petty officers room	2 items
Officers and chief petty officers room	2 "
Forward torpedo room	1 "

Hot plates.

The stove is powered by voltage 110/170 V, the total weight is 325 kg. It has:

2 Hotplates	each 3 kW	Current consumption	each 23 A
1 "	" 1.1 kW	"	" 8.5 A
1 Oven	" 4 kW	"	" 31 A
1 10 liter boiler	" 1.2 kW	"	" 9.2 A

In place of the oven, a 40 liter, 8.5 kW, 65.5 A boiler can be connected.

Boat's heating.

For electric heating equipment see section B VI.

U-Boat Type VIIC	C. Annex	Page 187

U-boat Information	Drawings 1 to 5	1

C. Annex.

1.	Boat silhouette	Drawing	1
2.	Interior plan: Horizontal cross section	"	2
3.	Interior plan: Vertical cross section	"	3
4.	Tank plan and trim table	"	4
5.	Blowing piping, emergency blowing and room ventilation ducting	"	5

Page		U-Boat Type VIIC

	Drawing
	1	Boat silhouette
	2	Interior plan: Horizontal cross section
	3	Interior plan: Vertical cross section
	4	Tank plan and trim table
		The original drawing of blowing piping, emergency blowing and room ventilation ducting is missing. The drawings below are substituted
	5A	Ballast tank flooding and blowing system, exhaust gas and emergency blowing mechanism
	5B	Blowing and emergency blowing mechanism, expressing regulating and negative tanks

	5C	Here is the original drawing from the manual for the type VIIB U-boat as implemented in U-73-76, U-83-87, U-99-102

Tauchungeunterschiede von Bug und Heck gegenüber der Druckmessertiefe
Diving differences for bow and stern opposed to the depth gage

Achterlastig	Down by the stern
Bock für Netzabweiser	Support for net deflector
Bug	Bow
Bug (untere) Netzsäge	Bow (bottom of) Net saw/cutter
Bug höher	Bow higher
Bug tiefer	Bow deeper
Grad	Degrees
Heck	Stern
Höhertauchung	Shallower immersion
Kiel	Keel
Netzsäge (oben)	Net saw/cutter (top of)
Rudderhacke	Rudder heel (bottom of the rudder)
Tiefertauchung	Deeper immersion
Turm	Conning tower
Vorlastig	Down by the bow

Ruderblätter	Rudder planes
Fester winkel	Fixed angle
Drehpunkt des Ruderblattes	Pivot point of rudder planes
Hauptruderhebel	Main rudder arm
Schubstange	Connecting rod
Senkrechte Zwischenwelle	Vertical intermediate shaft
Doppelhebel	Double arm

Motor mit Getriebe	Electric motor with gear box
Drucklager	Thrust bearing
Kupplung	Clutch
Führungsstange mit Gewinde	Threaded guide rod
Stopfbuchsen	Stuffing boxes
Kreuzkopf	Limit slider
Druckkorper	Pressure hull
Lenkstange	Pushing rod
Ruderwelle mit Hebel	Rudder shaft with lever

Career track (Laufbahn)	Specialty	Career track	Specialty
I	Seaman	VIII	Unused
II	Machinist (Engine room personnel)	IX	Administrative
III	Helmsman/Navigation	X	Clerical
IV	Radio operator	XI	Medical
V	Carpenter	XIII	Musician
VI	Ordnance	XIV	Coastal Artillery
VII	Mechanic (Artificers/Torpedomen)	XV	Motor Transport

Zylinderdeckel	Cylinder head
Gurtplatte	Top flange plate
Zurganker	Tie Rod
Arbeitszylinder	Work cylinder
Gestelloberterteil	Engine block (upper part)
Gestellunterteil	Engine block (lower part)
Triebwerksgehäuse und Grundplatte	Crank case and bed plate
Grundplatte	Bed plate
Ölwanne	Oil pan