APPLYING RESULTS OF 

 SEAKEEPING RESEARCH 



Edward V. Lewis 



Webb Institute of Naval Architecture 



Glen Cove, Long Island, New York 



ABSTRACT 



Although developments in the theory of seakeeping are still continuing 

 rapidly, this paper points out that presently available research results 

 can be effectively applied to practical problems of ship design. The 

 most useful tool is the method of superposition whereby almost any 

 ship response to irregular short-crested seas maybe predicted — pro- 

 vided the responses to regular waves are known. Pending the develop- 

 ment of completely satisfactory methods of calculating these responses 

 theoretically at all headings to waves, results of systematic model tests 

 can be used. 



A calculation procedure to be followed in making such predictions of 

 ship behavior in irregular waves is outlined, and typical results of cal- 

 culations are presented. These include trends of wave bending moments 

 with ship size, speed, and heading. In the same manner, trends of rel- 

 ative bow motion are presented under the influence of similar factors. 



Some general conclusions are drawn regarding the effects of ship size, 

 proportions, speed, and heading on seagoing performance of ships. 

 Needs for further oceanographic data, systematic model tests in waves, 

 and advances in seakeeping theory are outlined. Future possibilities in 

 the use of such research in developing improved naval ships are ex- 

 plored, with particular emphasis on the optimization of ship designs in 

 relation to seagoing performance. 



INTRODUCTION 



Professor B. V. Korvin-Kroukovsky in the introduction to his classic paper 

 on the theory of ship motions in regular waves [1] called attention to the need at 

 times to apply "vigor" as well as "rigor." The emphasis of this symposium has 

 been rightly placed on rigor — on refining and improving our theoretical tools 

 for calculating the motions of ships in waves. This paper, along with certain 

 other presentations, meanwhile, attempts to demonstrate that the application of 

 vigor — even with our presently available tools — can yield valuable conclusions 

 for the guidance of ship designers. 



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