Sharma 



considered, where the transverse cut analysis result is higher. Thus the com- 

 parison is encouraging and lends further support to the author's comment, in 

 the last paragraph of the section "Experimental Verification," that this meas- 

 ured quantity, which N. Hogben has aptly termed "wave pattern resistance," 

 seems to be definable in a practical sense. Further details on these results, 

 including if possible results on a longitudinal cut method using the wave slope, 

 should be forthcoming in a joint paper as mentioned by the author in his aclaiowl- 

 edgments. 



Let me make a comment on the specific question of the paper, that is, the 

 experimental design of a bulb for a given ship. This is that the obvious suita- 

 bility of the spectrum result in the present method of wave analysis for investi- 

 gating size and location of the bulb does not preclude the consideration of other 

 methods under the same assumptions, to solve the same problem in the tank. 

 These are (a) linearity of the bulb wave system to the bulb strength and (b) fixed 

 relative location of the bulb wave system with the bulb itself. In particular, one 

 could construct the bulb X and Y signals (not the product) from the test data or 

 from theory and apply this record through a computer analysis to the basic ship 

 X and Y records to find optimum locations and strengths, without substantially 

 more effort than required in analyzing and integrating the spectrum for the 

 same purpose. 



I am glad to see, that the author has included a plug for full-scale tests of 

 wave resistance using one of these methods; a task which would require great 

 effort but which would also, in my opinion, afford correspondingly great promise 

 to learn something useful as well. Let me conclude by again thanking the author 

 for preparing such an interesting paper; indeed one of a growing number of 

 papers in this field with results and techniques which are of practical use to the 

 ship designer. 



DISCUSSION 



K. W. H. Eggers 



Institut fur Schiffbau der Universitdt Hamburg 



Hamburg University 



Dr. Sharma showed us some computed results regarding the efficiency of 

 wave analysis based on wave height along a longitudinal cut. In his Fig. 3 we 

 may observe to what degree the spectrum of the free wave system may be de- 

 termined from a profile of finite length. He also gives values for the ratio of 

 wave resistance calculated from information of a finite cut to exact theoretical 

 resistance. 



I want to complete his presentation by a general survey of the dependence 

 of this ratio on the sidewise distance y of a cut from the ship's path as well as 

 from location X of the truncation point. For the same model and for a speed 



768 



