CONFIDENTIAL REPORT 2G-21
S88
     
 
FORMER GERMAN SUBMARINE TYPE XXI
 
 
 
 
DAMAGE CONTROL
 
     
 
SUMMARY
 
     
          There is not the possibility of controlling damage on this type of vessel which existed in earlier types.  Fewer means are available, and these are applicable, generally speaking, to a surfaced vessel if there has been any break in the pressure hull.  
          List and trim control are obtained by transfer of water in the trimming system and in the regulating tank piping system, as on earlier vessels, but in certain respects these systems have in the course of simplification lost flexibility.  
     
     
     
     
     
     
     
 
July, 1946
 
 
 
 
PORTSMOUTH NAVAL SHIPYARD, PORTSMOUTH, N. H.
 
     
     
     
 
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  REPORT 2G-21
S88
     
 
DAMAGE CONTROL
 
     
  GENERAL  
          There is not as much choice in the means for controlling damage on this type of vessel as there is on the earlier types of vessel.  The limited reserve buoyancy circumscribes the value of counter flooding, although this is possible when an exterior tank on one side has been damaged.  List and trim control also fail to develop the alternatives available on earlier vessels.  
     
  CHECK-OFF LIST  
          This is similar in contents and format to that on all other types of vessel, although the listed items apply only to this type of vessel.  
     
  PARTIES  
          No information is at hand on the number of character of damage control parties.  
     
  MEASURES  
           The general information book provides tables showing the effect of damaged hull, damaged tanks, and of damaged hull and adjacent tanks on trim and weight for a surfaced vessel.  For a submerged vessel the damaged tank table is indicated as applicable but it is further stated that there is no means to compensate for the flooding of a room when the vessel is submerged except for the conning tower and after compartment.  
          Measures discussed are:  
          a)  Blowing, under which head the full capacity of the air banks is said to be sufficient to blow all MBT once at 70 meters (230 feet).  Under this head is also given the possibility of blowing normal fuel oil tanks with the qualification that this is no emergency measure because of the small size of the piping.  
          b)  Segregation of compartments, which includes a list of valves to be closed.  
     
 
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  REPORT 2G-21
S88
     
          c)  Pumping, which includes curves for the surface drain pump and deep drain pump which plot the area of a leak which can be offset against the submerged depth of the vessel.  
          No mention is made of counter flooding.  
          Trim control is made possible by the trim tanks and their related air and water piping, which provide for the transfer of water forward or aft as desired, between the corresponding halves of the forward and after trim tanks.  No transverse connection is provided, so there is no possibility of using the trim connections for list control.  Additional possibilities for trim control lie in the regulating tank and regulating bunker piping, which permits transfer of water or oil either forward, aft, or across ship to the opposite half tank.  The air and water piping connections between the WRT tanks and the torpedo tubes, and the further piping from the WRT tanks to the drain pump, permit control of trim and, by thwartships connections, list.  It is possible to fill the tubes from the WRT tanks, or the WRT tanks by draining the tubes.  It is also possible to pump the WRT tanks dry by use of either drain pump, and it is further possible to blow water from one WRT tank to the other.  
     
     
     
     
     
     
     
     
     
     
     
 
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