Hydrodynamic Design of an S Semi submerged Ship 



DISCUSSION 



Gerald E. Bellows 



Universitdt Hamburg, Institut fur Schiffbau 

 Hamburg 3 Germany 



I would like to thank Dr. Lang for an excellent presentation. 

 It is evident that this type of ship has extremely good seakeeping pro- 

 perties. This is perhaps its major advantage over the monohull. I 

 have studied ships of this type and have found that, with the cargo 

 loaded on the deck, it is difficult to obtain sufficient GM in both the 

 longitudinal and transverse directions. I wonder if Dr. Lang could 

 give us a weight breakdown, including the structure, fuel, and cargo 

 (or payload). I also would like to know what type of power plant would 

 be used and if it would be located in the underwater hulls. I would like 

 to know if it is possible to alter the draft by ballasting. Dr. Lang has 

 mentioned in his report that the draft could be a problem, but this 

 could be overcome by using ballast to alter the draft when entering 

 port. 



REPLY TO DISCUSSION 



Thomas G. Lang 



Naval Undersea Research and Development Center 

 San Diego j California, U.S.A. 



To answer the first question, the metacentric height (GM) 

 increases a little faster than the square of the distance between the 

 waterplane areas. Thus by concentrating the waterplane area near the 

 four corners of the platform through using four struts we obtain a 

 maximum GM for a given waterplane area in both roll and pitch. As 

 a result, it is possible to have a GM that is on the order of three or 

 four times that of the conventional monohull in roll, and a GM which 

 is much less than a monohull in pitch but yet one that gives very good 

 pitch response. The result, as seen in the film, is an acceptable me- 

 tacentric height in both roll and pitch. 



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