Lang 



trolled model was used to test light crack avoidance and the problem 

 of hull flooding in case a crack cannot be avoided. The model was 

 operated at top speed and suddenly given full reverse thrust. In no 

 case did the bow submerge or was there water over the deck. The 

 main reason for this good behavior is that the relatively low water- 

 plane area has been concentrated near the front and the back of the 

 craft by making use of four struts. Thus, the metacentric height in 

 pitch is a maximum for a given waterplane area. This metacentric 

 height is adequate to prevent excessive pitch in the case of full re- 

 verse thrust from a condition of top forward speed. In the case of hull 

 flooding, the control surfaces were adequate to raise the platform to 

 trim conditions as speed increased. Trim at rest could be adjusted 

 by blowing water ballast or fuel on the damaged side and/or counter- 

 flooding on the opposite side. 



DISCUSSION 



Hans Edstrand 



Statens Skeppsprovningsanstalt 

 Goteborg, Sweden 



I have not read Dr. Lang's paper, but when I looked at the 

 beautiful film I wanted to ask a question. The model size seems to 

 me to be enormous compared with the tank dimensions, and I should 

 like to know if Dr. Lang has checked his results in a larger tank and 

 if he has used the measurement for quantitative development. 



REPLY TO DISCUSSION 



Thomas G. Lang 



Naval Undersea Research and Development Center 

 San Diego, California, U.S.A. 



The model size is slightly large for the tank it was tested in. 

 The model hull diameter was 4 inches and the model was 5 feet long; 

 the tank was 6 feet deep, 12 feet wide, and 300 feet long. The ratio 



578 



