Applying Results of Seakeeping Research 



naval ship motions give pitch and heave amplitudes in regular head seas, but no 

 information of phase angles that would permit relative motion between bow and 

 wave to be computed, or vertical acceleration at any point along the length of 

 the ship. Furthermore, motions in oblique seas are unknown. It is to be hoped 

 that vigor will be applied here in systematic experimental work. 



A related development of great importance is the application of electronic 

 computers to the preliminary "feasibility study" stage of ship design. Pioneer- 

 ing work in the field of merchant ship design [19] is now being applied to the 

 naval design problem. The outstanding result of this work to date is the clear 

 demonstration that, insofar as the ship design problem for ideal, calm water 

 conditions is concerned, there are many possible technical solutions. Assuming 

 certain required characteristics, such as payload, range, and speed, the princi- 

 pal technical requirements to be met, which can be expressed in equation form, 

 are: displacement, volume, stability, and freeboard. But the number of ship 

 variables to choose from — as dimensions, fullness, power, etc. — is much 

 greater. In short, there are more unknowns than there are equations, a situa- 

 tion which is disturbir^ to a mathematician but intriguing to the naval architect 

 who discovers he has a wider freedom of choice than he had previously realized. 

 Following the traditional trial and error approach, the designer was apt to feel, 

 when a satisfactory compromise of all the factors was reached, that this was 

 the only possible design solution — or at least that he could not depart far from 

 it. But results show [19] that very wide variations in overall dimensions are 

 possible with only slight changes in the cost criterion used (capital charges 

 plus fuel). 



The significance of all this to the seakeeping problem is that the availability 

 of a method of realistically evaluating the seagoing performance of widely dif- 

 ferent alternative ship designs opens the door to definite improvements in the 

 economic efficiency of merchant ships and the military effectiveness of naval 

 vessels. The procedure is visualized as follows for the case of a destroyer- 

 type ship whose primary mission is patrol duty in the North Atlantic, for exam- 

 ple. A wide range of possible ships is determined, each of which has the re- 

 quired speed, payload, and range. The potential performance of each design is 

 then predicted on the basis of some criterion such as percentage of time that a 

 stated speed or speeds can be attained at sea without shipping water. Cost fac- 

 tors and operations research techniques must finally be brought into the picture 

 to ascertain which design is best from the viewpoint of military effectiveness. 

 It is my firm belief that the optimum ship designed in this way will not be the 

 same as that designed for minimum displacement, minimum power on trial, or 

 other purely technical criteria. In short, vigorous application of techniques now 

 at hand should lead to better ships for the Navy. 



These future developments will be greatly enhanced in value if much more 

 complete information on ocean wave spectra encountered on various trade routes 

 becomes available. The excellent work of Pier son [5] is only a beginning. Fur- 

 thermore, there is a real need for additional short- crested sea spectra, such as 

 those obtained by the National Institute of Oceanography in Britain [20]. Here 

 again vigor in obtaining and analyzing ocean wave data is the most urgent need. 



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