36 



bow. The development of dynamic lift by the elevators largely offsets the 

 downward force on the hull, so that the float remains on a more or less even 

 keel. The combined effect, however, results in a greater submergence than 

 would be obtained without the elevators. As the speed is increased, the in- 

 crease in lift on the large elevators is sufficient to cause a positive in- 

 crease in the angle of attack (or trim) of the float. As the angle of attack 

 is increased, the hull, acting as a hydrofoil of very low aspect ratio, de- 

 velops sufficient dynamic lift to cause the float to begin to rise. This 

 sequence is illustrated by a number of photographs which were taken during 

 the model-basin tests and which are discussed below. 



TECHNIQUES AND RESULTS OP TESTS OP 

 THE TMB DISPLACEMENT FLOAT 



The same methods were used in the model-basin tests of the TMB dis- 

 placement float as were used for the planing float. However, before syste- 

 matic load-carrying tests were made with the displacement float, a number of 

 tests under a single loading condition were first carried out to determine 



2 4 6 8 10 12 

 Speed In knots 



Figure 30 - Drag Curves for TMB Displacement Float 



