data for the TMB floats have been reduced to nondimensional form so that they 

 may be used in the selection of geometrically similar floats for any applica- 

 tions in which submerged loads must be towed from surface floats. 



Since the characteristics of the TMB planing """.oat under load in 

 the displacement regime were already known (2), the tests were extended to 

 determine its performance in the planing regime. For the range of Reynolds 

 numbers over which this design is likely to be used, it was possible to com- 

 pile the data in the planing regime into a single nondimensional relationship 

 between drag, total load, and speed-length ratio. The characteristics of the 

 balsa-wood float are also presented in nondimensional form as a family of 

 curves of drag coefficient plotted against speed-length ratio, with a load 

 coefficient as parameter. Since the performance of the NMWTS float Indicated 

 that this float is not useful for towing submerged loads, no analysis has 

 been made for this float. 



The tests disclosed phenomena in the region of transition from sub- 

 surface to surface operation of a symmetrical shape such as the TMB planing 

 float, which it is believed have not been reported hitherto. A hysteresis 

 loop in the drag characteristics of the float was also discovered in this 

 unstable region. It was found that this float, as well as the balsa-wood 

 displacement float, exhibits the same type of striations in the flow over 

 the float when towed near the water surface. Just before complete emergence, 

 as is shown by spheres and projectiles dropped through an air-water Interface. 

 A hypothesis based on the instability of the vortex formed near the point of 

 separation of flow is offered in explanation of the latter observation. 



The particular sizes of floats used in the tests considered herein 

 were determined on the basis of the catenary-sweep project. Since this pro- 

 ject represents only one application of these floats, the results are analyzed 

 in terms of the general problem. Accordingly, the overall considerations of 

 hydrodynamic design and performance of the TMB floats are considered in the 

 body of the report. The tests of the NMWTS float are discussed in Appendix 1. 

 The applications to the catenary-sweep problem including observations of the 

 floats during full-scale trials in a seaway are considered in Appendix 2. 

 Problems of the structural design of the planing float as well as the results 

 of submergence tests on this float to determine the maximum safe depth x)f sub- 

 mergence before failure are discussed in Appendix 3 • Problems of construction 

 and waterproofing of the balsa -wood float are considered in Appendix 4. 



PERFORMANCE CHARACTERISTICS OF THE TMB PLANING FLOAT 



It has been pointed out that the particular floats used in the ex- 

 periments discussed herein were selected on the basis of the catenary-sweep 



