Lang 



As far as the ratios of the various weights are concerned, our 

 preliminary calculations indicate a structural weight to total weight ratio 

 on the order of 40 per cent for a moderately sized ship, if the ship 

 is made out of aluminium. Thus, we are proposing that a ship of this 

 type be made of aluminium to help to solve the weight problem. 



In regard to the power plant, we would propose that the po- 

 wer plant on small craft be located in the top cross structure, with 

 some type of a drive mechanism to transmit the power down to the 

 propeller. In ships of a few thousand tons or greater, we would pro- 

 pose that the power plants be located in the tailcones of submerged 

 hulls, with direct drive to the propeller through a gearbox. Alterna- 

 tively, a cryogenically cooled electric power system 



"We are proposing gas turbines for power because of their light weight 

 and efficiency, especially in the larger size range. 



In answer to the last question, on ballasting, we do have pro- 

 vision for ballasting in all the proposed designs. In very shallow water 

 ports, the loaded ship minus fuel provides a draft about equivalent to 

 that of a monohull ; therefore such a ship could be fully loaded at the 

 dock and the fuel topped off in the deeper region of the harbor. 



DISCUSSION 



Nils Salve sen 



Naval Ship Research and Development Center 

 Bethesda, Maryland 3 U.S.A. 



I have recently made an investigation of the seakeeping cha- 

 racteristics of low-water-plane catamarans and I found it a very inte- 

 resting subject, Reference 1. What makes it so much more interes- 

 ting than for conventional ships is that the seakeeping characteristics 

 of catamarans and in particular LWP catamarans are extremely 

 sensitive to changes in the hull geometry. For conventional monohulls, 

 on the other hand, large changes in the hull parameters are required 

 in order to produce any substantial effects on the seakeeping charac- 

 teristics. 



It is recognized that as far as the seakeeping is concerned, 

 the major advantage of the LWP catamaran over conventional hulls 

 is that they have a very low natural frequency due to their small water- 



574 



