The total vertical lift, dynamic and hydrostatic, was found to be 



L = lAiqb^ +B [3] 



where B is the total buoyancy or hydrostatic lift. The large angle of attack 

 attained by the float in the submerged condition without stalling is attri- 

 buted to its low aspect ratio (4) . 



Although these data were sufficient for designing an optimum sur- 

 face float under given loading conditions, it was not possible to predict 

 accurately the performance of the float in the planing regime. Therefore 

 the tests of the float for the catenary-type minesweeping arrangement were 

 extended to fill in the missing data. Since the tests were planned original- 

 ly to provide a rapid check on the application as catenary-sweep floats, it 

 was not considered expedient to develop dynamometers for the single design. 

 However, the data proved to be sufficiently accurate to justify the use of 

 the technique described in the following paragraphs in completing a definite 

 program. A similar technique, which proved entirely reliable and on which 

 the present method is based, is described in a report on the NRL Mark 3 buoy. 

 Reference (5). 



TEST METHODS A^fD TECHNIQUES 



In tests of the NRL Mark 3 buoy (5), the maximum loading capacity 

 under loads which increased with an increase in speed had to be determined. 

 For this purpose, a carefully calibrated depressor was suspended below the 

 buoy. The shape of the buoy was such as to give sharply defined combinations 

 of loads and speeds at which the buoy became overloaded. For the TMB planing 

 float, on the other hand, it was desired to determine the resistance and be- 

 havior under approximately constant loads over a considerable range of speeds. 

 The tests were further complicated by the difficulty of determining the speeds 

 at which true planing was obtained. 



Based on the method used in testing the NRL Mark 3 buoy, a series 

 of faired weights (or depressors) was designed for the application of the de- 

 sired loads. The weights were designed to provide a family of loading curves 

 with sufficient separation to cover the range of loads and speeds desired 

 without exceeding the initial reserve buoyancy of the model tested. The four 

 weights, shown in Figure 5, could be towed from either of two towpoints. For 

 reasons of stability and to provide a slight negative angle of attack, the 

 center of gravity of each weight was placed forward of the forward towpoint. 

 The purpose of the negative angle of attack was to provide additional down- 

 ward lift in order to counterbalance the upward lift forces on the weight 

 towline. 



