CONFIDENTIAL REPORT 2G-21
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FORMER GERMAN SUBMARINE TYPE XXI
 
 
 
 
DESIGN, MODELS AND PLANS
 
 
 
 
SUMMARY
 
     
          This type of vessel is a radical departure in hull form and in certain mechanical and electrical respects from earlier types of German submarines, for the purpose of increasing submerged speed, and permissible submergence depth.  
          The changes have been made at the expense of surface speed and other surface characteristics.  Further, the design was not completely thought out before the beginning of construction, and has a number of shortcomings as a result, as described in the pertinent sections of this report.  
          Nevertheless, the results obtained indicate the need to exploit the possibilities of the type to the maximum.  
     
     
     
     
     
 
July, 1946
 
 
 
 
PORTSMOUTH NAVAL SHIPYARD, PORTSMOUTH, N. H.
 
     
     
     
 
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  DESIGN, MODELS AND PLANS
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          The principal characteristics of the type 21 submarines as given in NavTechMisEu Report 312-45, are summarized herein.  The vessels depart in certain respects from the data given, and where they do, reference has been made to the fact in the proper report section.  The designed characteristics, which were not met in all respects, as as follows:  
     
 
  L.O.A.
251'-10"
  Max. beam
21'-8"
  Draft - surface
20'-4"
  Max. Diam. of Pressure Hull
17'-6"
  Displacement - surface
1621 cu. meters
                          submerged
1819 cu. meters
  Designer's depth
135 meters
  Complement - total
57
  Fuel capacity
228 metric tons
                           including regelbunker
250 metric tons
  Cruising range - normal
15500 mi. @ 10 kn.  2 engines
                           max. speed
11150 mi. @ 12 kn.  2 engines
                           submerged
365 mi. @ 5 kn.  2 engines
   
285 mi. @ 5 kn.
   
170 mi. @ 8 kn.
   
110 mi. @ 10 kn.
  Surface speed - max.
15.6 kn.
  Submerged speed - 1 hr. rate
17-18 kn.
  Torpedo tubes
6 bow
  Torpedoes
20
  Guns & ammunition
two 30 mm. in 2 turrets
   
3800 rounds
  Main propulsion Machinery
(two 1970 H.P. MAN 6 cyl.
                          main engines
(4 cycle, M6V40/46 with
   
(supercharger, at 520 RPM Max.
                          main motors
Two 2070 H.P.  2GU 365/30
   
double motors at 1675 R.P.M.
                          creeping motors
(Two 113 H.P. GV323/28 single
   
(motors at 350 R.P.M.
                          batteries
Six battery divisions, each
   
with 62 cells and 1300 A.Hr.
   
Cell type 44 MAL 740E
 
          On vessels observed, the stabilizer fins did not extend beyond the full beam of the vessel, although as designed, the stabilizers were to have been 26'-3" wide.  
     
 
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          Displacement on both vessels was found to be about 40 tons greater than the design figure above.  
          The cruising radius and the speeds on main engines were modified, in the vessels observed, by the removal of the superchargers, which reduced the engine horsepower and efficiency.  
          Submerged speeds did not, so far as can be determined, reach 18 knots on actual vessels.  
          Torpedo stowage, including the tubes, for 23 torpedoes exists, but it is necessary to retain three idle positions to permit withdrawal of torpedoes from tubes for servicing.  The actual total torpedoes carried is, therefore, 20.  
          Additional details will be found in the appropriate sections.  
          Wind tunnel tests on the hull of this type of vessel are described in NavTechMisEu Report 188-45.  
          Plotted wave formation at three speeds is included among the information in the Tests for Type XXI Submarines.  
          Discussion of the specifications will be found in the S1-7 section of the report.  
          There were many changes from design during the course of constructing these vessels.  They include, in addition to the removal of the superchargers and reduction in stabilizer area aforementioned, the following:  
          a)  Simplification of hydraulic controls  
          b)  Modification of muzzle door operating gear  
          c)  Alteration of battery ventilation  
          d)  Many minor but cumulative alterations to the outer shell and fairwater to reduce drag caused by excessive size of flooding and venting openings, and to arrive at a satisfactory compromise bridge structure  
          e)  Elimination of the negative tank  
          f)  Installation of 9 meter instead of 7.5 meter high-angle periscopes  
          g)  Provision of a forward-aft antenna with one end supported on a faired stanchion aft on the superstructure  
          h)  Installation of piping for automatic depth control and hovering gear.  
     
 
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