The trial book (Tests for Type XXI Submarines) is similar in general layout to the one described for the 9C vessels, but as the arrangement is different and the items covered do not all duplicate those on the earlier vessel types, a description is given below.  
          The book is divided under the following principal headings:  
          A.  Forward.  
          B.  Principal characteristics.  
          C.  Tests of individual systems.  
          D.  Questions to be answered by the trial board.  
          E.  Advice on special reports.  
          F.  Trials by other agencies.  
          G.  Final report.  
          H.  Tabulated material and trial reports.  
          There are 54 pages of text material describing what is covered under headings A to G, inclusive.  Points covered in addition to the headings listed in the 9C report are:  
          a)  Condition of buoyancy.  
          b)  Preliminary and final inclining experiment.  
          c)  Sallying ship.  
          d)  Limiting rpm.  
          e)  Turning circles and turning rates.  
          f)  Behavior when stopping vessel.  
          g)  Behavior at sea, and influence of wind on maneuvering.  
          h)  Snorkel tests.  
          i)  Dynamic stability.  
          j)  Depth control when firing torpedoes.  
          k)  Communications control.  
          l)  Static dive.  
          m)  Quick dive.  
          n)  Deep dive as a substitute for pressure dock test.  
          o)  Tests of noises emanating from the ship.  
          p)  Much more complete tests of major components and single systems, effecting main engines, main motors, battery, ballast tank flooding, negative tank, rudder, log, hydraulic system, torpedo handling, ship's heating and cooling, air regenerating, refrigeration, WC, washing arrangements and galley equipment.  
          The questions which cover nineteen pages, pertain to weights and stability, surface characteristics, submerged characteristics, compartmentation, each system, diving and  


  REPORT 2G-21
  depth control, compensating and drain arrangements, ship control, arrangements for arms and armament, arrangements for the crew, rescue arrangements, and to allowance lists.
          The tabulated material, the curves and charts cover more ground than those for the 9C, and in addition, provide information as to test dives made to determine the effect of certain changes in the hull, with report thereon.  The book also contains a set of wave form curves at four rates of speed.  
          The type 21 test book has been of great value in the preparation of the reports on the various portions of the vessel.  The data actually provided is not complete, although the data required by the text is a good deal more thoroughgoing than that required for 9C vessels.  
          The test book is a valuable reference work, and covers in a formal manner the same ground which is covered on full scale trials in U.S. Naval practice.  
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