Pien 

 PROFESSOR WARD 



Professor Ward gives a clear picture as to how the ship resistance has 

 been divided into its components in many different ways. At the present time, 

 the "Modern Froude hjnpothesis (Hughes)" has been used until the technique of 

 obtaining the wavemaking resistance more directly is perfected. 



Another point raised by Professor Ward is related to my remarks on the 

 theoretical and experimental wavemaking resistance comparisons. I believe 

 this point has already been covered in my reply to Professor Weinblum's com- 

 ment. 



MR. SILVERLEAF 



Mr. Silverleaf's comment has been studied with great interest. The results 

 from their experiment with two bows, one having low wave resistance and the 

 other having resistful form, with a long parallel afterbody would be very reveal- 

 ing. I hope he will publish these results when they are available. 



Mr. Silverleaf has suggested that in assessing wave resistance alone, the 

 criterion should preferably involve only the displacement, speed, and length. 

 The basic aim of any ship design is to obtain a hull form to carry a specified 

 pay load at a specified speed, safely and economically. The principal dimensions, 

 especially the length, should be kept as small as possible so that the hull weight 

 and building cost can be kept low. On the other hand, the smaller the length, the 

 higher the V/sfL value and consequently, the higher the wave resistance. For a 

 chosen length, smaller beam and draft values would result in a higher prismatic 

 value. In the range of Froude number from, say, 0.9 to 1.2, increase in pris- 

 matic may also have a detrimental effect upon wave resistance. Higher resist- 

 ance means higher machinery weight, fuel weight, and fuel consumption. There- 

 fore, a final design is always a compromise between these contradictory factors. 

 Then how could we assess the merit of any design on wave resistance alone, 

 fairly? In view of the fact that the principal dimensions and the prismatic co- 

 efficient are decided upon by many factors besides wave resistance, we cannot 

 assess the merit of such decision purely from the resistance standpoint. There- 

 fore, for a fair comparison of wave resistance or total resistance, we have to 

 compare with forms of same principal dimensions and prismatic coefficient. 

 For this purpose, an equivalent Taylor's Standard Series form can be used as a 

 yardstick. 



CAPTAIN SHOR 



Captain Shor's explanation of the parameter /? as used by Professor Inui is 

 quite interesting. At present, even though a few semi-empirical parameters, as 

 used by Professor Inui, can bring the theoretical wavemaking resistance curve 

 into good agreement with an experimental curve, the values of these parameters 

 cannot be predicted accurately before the experiment is conducted. The flow 



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