CONFIDENTIAL REPORT 2G-21
S44
     
 
FORMER GERMAN SUBMARINE TYPE XXI
 
 
 
 
PROPELLERS
 
     
 
SUMMARY
 
     
          Twin, 3-bladed, cast steel propellers are installed on the type XXI submarines.  They are of standard design and are installed in the normal manner.  
     
     
     
     
     
     
     
     
     
 
May, 1946
 
 
 
 
PORTSMOUTH NAVAL SHIPYARD, PORTSMOUTH, N. H.
 
     
     
     
 
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  REPORT 2G-21
S44
     
 
PROPELLERS
 
     
  1.  INTRODUCTION  
          A detail plan of the propeller used on the XXI submarine has been received from Germany and is in the custody of the Bureau of Ships (Plan No. 5 SCHR 424, "Schiffsschraube").  
     
  2.  GENERAL DESCRIPTION  
          The type XXI German submarine is propelled by twin screws of standard design that give a maximum surface speed of 18 knots at 330 rpms and a submerged speed of 16.5 knots at 320 rpms (from German test data).  
          The positioning of the propeller and its interrelationship with the rudder and stern plates is discussed under the S22 section of this report.  
          The propellers are made of cast steel, having a specified tensile strength of 64,000 psi, elastic limit of 31,000 psi and elongation of 22%.  This use of steel in lieu of bronze reflects the material shortage existent in Germany during the late years of the war.  
          Information relative to the design and location of the propellers is listed below:  
 
Weight
1590 lbs.
Outer diameter
84.6 ins.
Pitch
84.0 ins.
Developed blade area
18.0 sq.ft.
Projected blade area
15.5 sq.ft.
Propeller from C/L
5.6 ft.
Propeller above B/L
9,5 ft.
Hub forward of stern
18.6 ft.
Minimum dist. blade tip to hull
9.8 ins.
Clearance-hub to stern plane
5.5 ins.
 
          The propellers are secured to the shaft in the same manner as described for the IX C German submarine.  The screws turn outboard when going ahead -  
     
 
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  REPORT 2G-21
S44
     
  (Attention is called to the fact that several documents in existence stating that they turn inboard are in error.)  
     
  3.  CONCLUSIONS  
          Except for the fact that the screws are made from a substitute material, the propeller installation and design are standard in nature.  
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
 
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