Panel Discussion 



t is the strut thickness, 



Pa is the mass density of air, 



Pw is the mass density of water. . ,, 



Dr. Breslin said that he would expect a considerable scale effect in such em- 

 pirical determinations, since the spray sheets from the strut are continuous in 

 model scale, causing an early closure of the ventilated cavity, as compared to 

 full scale, where the spray sheets break up near the leading edge into discon- 

 nected droplets, allowing air to flow nearly unobstructed into the cavity at the 

 base of the strut. Elata surmised that such effects would only change the con- 

 stant in his inequality. 



TOPIC 3 



The third category, viz., current features of hydrofoils now under develop- 

 ment, was opened by W. Carl (Grumman Aircraft, Bethpage, N.Y.) who showed 

 an impressive film taken of the PGH-1 while operating during deck-gun firing. 

 This craft cruises at 50 knots in six-foot waves. Carl pointed out that at 

 Grumman the prospects of flutter are considered real and that both by design 

 and experiment, they have managed to avoid flutter. This vessel is propelled by 

 a KaMeWa controllable pitch propeller giving greater range and efficiency than 

 the water- jet propulsion of the competing design developed by Boeing. 



Dr. M. Kinoshita (Hitachi Shipbuilding Co., Osaka) gave a detailed analysis 

 of data from commercial craft operating between the islands of Japan. He 

 showed that suspension of service due to rough seas is a vital factor which 

 could be reduced by research on the seakeeping characteristics of hydrofoils. 

 This analysis was very thorough but, unfortunately, the unprepared charts could 

 not be effectively projected. 



Dr. Breslin asked if Dr. Kinoshita had established a relationship between the 

 foilborne clearance and the wave height at which service had to be curtailed. No 

 definitive answer was secured, although Dr. C. Hook (Hydrofin Design Centre, 

 Bosham, England) allowed as how the relationship also depends upon speed. 

 "The faster you go, the higher you must stand." 



Baron H. W. Von Schertel (Supramar, Lucerne) showed slides and a motion 

 picture. The slides depicted a new large car-carrying ferry. His new craft em- 

 ploy a pneumatic scheme to reduce lift by allowing air to be sucked by the lower 

 pressure areas on the foils. The air supply is controlled by a valve, which is 

 activated in response to pitch angle, roll angle, and roll angular rate. High re- 

 liability is claimed for this control system, which, when applied to only one foil 

 (after) in conjunction with a surface-piercing foil forward, gives a smooth ride. 

 The film shewed an experimental craft with fully submerged foils employing the 

 controlled ventilation principle. This craft was built for the U.S. Navy. The op- 

 eration of this craft, as could be ascertained from the movie, was certainly 

 impressive. 



1605 



