29 



5.2.2. The Effect of Variation of Draft for Constant Beam B 



In this case the volume is proportional to draft. 



Contrary to its dependence upon beam, the wave resistance cannot be 

 expressed in an explicit manner as a function of the draft in a general way. 

 However, approximate formulas can be derived from Michell 's integral; they can 

 be treated as special cases of the symbolic expression 



« = ^g ¥ e(t' " '^) 



[13] 



Only a small number of such calculations has as yet been made. ' '" 

 The form of the hull (??), especially the vertical distribution of displacement, 

 influences to some extent the relation between resistance and draft, but even 

 the longitudinal distribution can have some bearing on the problem. 



For simplicity the influence of n on the function E{hAi,77,P) can be 

 neglected. Then E is a function of hA and P only. Attempts have been made 

 to approximate H^E by a power relationship, R ~ C h"^^^' where C is a constant 

 [l6] (Figure 9). 































^ 



— 



n, (Beam) 





^ 



y^ 









__^ 



-^ 





ng (Draft) 























2.5 



2.0 



1.5 



1.0 



0.5 







I 2 



V 



Figure 9 - Muraford's Exponent Curves 



Obviously, such a simple approximation can be expected to hold only 

 for a limited range of H/L which again is dependent upon F.* Some values of 

 n are given below: 



*In the limiting case of H/L'-*> 0, a quadratic law n = 2 results as an asymptotic value, which, how- 

 ever, is of no practical use because of the breakdown of the theory. 



