Planing Craft 

 1. INNOVATIONS IN PLANING-CRAFT DESIGN 



Commander P. DuCane of Vospers, Ltd. described the application of a 

 "surface" propeller to a deep-veed racing boat of the international Rl class. 

 It might be explained that in a "surface" propeller the axis of the propeller is 

 so placed that only about one-half the disc is immersed. This is necessary to 

 avoid propeller blade cavitation by allowing the propeller to break the water sur- 

 face and thus ventilate the negative pressure side of the blade. Further, no ap- 

 pendages excepting a rudder will be under the boat, thereby eliminating the ap- 

 pendage drag arising from shaft and propeller strut. The propeller itself was a 

 three -bladed supercavitating type with blunt trailing edge. In full-scale trials, 

 other conditions being essentially identical, the fully submerged propeller drove 

 the boat at 54.8 mph and the surface propeller drove the boat at 60 mph. Subse- 

 quent discussions indicated general interest in the application of a surface pro- 

 peller to shallow-draft planing hulls and surface-effects ships. 



D. F. Calkins of the U.S. Naval Undersea Warfare Center, discussed the de- 

 sign features and model test results for a three -point ram-wing hydroplane in- 

 tended for unlimited hydroplane racing. This unique hull, which is a concept 

 developed jointly by D. F. Calkins and B. Bryant, consists of two parallel planing 

 surfaces that provide lateral stability and are located forward of the center of 

 gravity; an NACA 4406 wing section between the planing surfaces and central 

 hull operating in ground effect, and the vertical component of propeller thrust. 

 The planing surfaces are extended aft along the wing tip chord to act as wing 

 fences, thus creating a ram-wing hydroplane. The intent is to design a vehicle 

 which has the C.G. forward of wing aerodynamic center and thus provide for 

 longitudinal stability of the craft — conventional hydroplanes suffer from a lack 

 of longitudinal stability at high speed. Tow-tank tests were conducted on a model 

 of the ram-wing configuration up to model speeds of 60 fps. These tests, which 

 were conducted at the Marine Technology Center, General Dynamics, showed that 

 at 100 mps (full-scale equivalent) the lift-drag ratio of the ram-wing design was 

 approximately twice that of the conventional hydroplane designs which generally 

 consist of two sponsons (connected to a center hull) planing on their aft extremi- 

 ties and the lift of a "surface" propeller. Further, the test results showed that 

 the trim of a conventional hull increases with speed up to the point that it liter- 

 ally flies from the water surface, whereas the trim of the ram-wing hull de- 

 creased with increasing speed in the high-speed range. Work is now proceeding 

 on optimizing the configuration. 



A report was presented on the work of E. P. Clement of NSRDC on the dyna- 

 plane boat concept. This is a stepped planing hull where most of the lift is pro- 

 vided by a cambered planing lifting surface of moderately high aspect ratio lo- 

 cated just forward of the center of gravity with an adjustable lifting surface at 

 the stern providing balance, stability, and control of trim. The large portion of 

 superfluous wetted area of the conventional unstepped planing boat is eliminated 

 by this approach and a drag decrease results from this fact together with the 

 more favorable value of aspect ratio. Model tests at NSRDC showed that for 

 boats of 100,000 pounds gross weight, the dynaplane design requires 10% more 

 horsepower than the conventional unstepped design at a speed of 25 knots and 

 50% less horsepower at speeds of 55 knots. The respective values of lift to 

 drag ratio at 55 knots are 6.2 for the conventional design and 12.5 for the dyna- 

 plane design. 



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