17 



Towing Speed, 0.5 Knot 



Towing Speed, ^.0 Knots 









' "^ 





Towing Speed, ^.5 Knots Towing Speed, 9.0 Knots 



Figure 14 - Photographs of T^E 4l-Inch Planing Float Being Towed 



These tests were made under loads imposed by the 50-pound weight towed from the forward towpolnt. 



Throughout the submerged region, the drag of the float varies rough- 

 ly as the square of the speed. At low speeds, for the loads under which the 

 float does not become submerged, the drag is due primarily to skin friction 

 and, in small part, to wave-making resistance, and varies as the speed to a 

 power less than 2. At speeds that are sufficiently high, the float develops 

 dynamic lift on the surf ace, in addition to its buoyancy until it reaches the 

 "hump" speed characteristic of planing surfaces, beyond which the load- 

 carrying capacity of the float is attributable almost wholly to planing ac- 

 tion. Just where the float reaches true planing action beyond the hump is 

 difficult to determine. However, for purposes of the analysis made in sub- 

 sequent sections, the planing region was taken to be the region beyond the 

 peaks of the humps in the drag curves of Figure 10. 



In general, the TMB planing float was stable throughout the various 

 tests made. However, for the loading conditions Imposed by the 75-pound and 



