19 



Hence we can immediately derive the resistance per unit displacement for a 

 given b/a and shape when r is known. 



The introduction of the displacement A in [20] is open to objection 

 since so far we have not distinguished between the length of the body and the 

 distribution. We repeat the definitions: 



2a is the length of the distribution along the axis 

 L is the length of the generated body 

 2b = D is the diameter of the generated body 

 Obviously for the displacement of the body we must use L = 2 1. Then 



C n = Wg C 2 b 4 /a = A ^Cfbfa [25a] 



<*a 2 / 



Further, the ratio h/l = D/L is technically more important than b/a; hence 



r = R_4_ 11 <L [25b] 



4 2C 2 b 2 / 



or 



1-W4>„ ^c] 



(*) f ^ 



Later we shall use another coefficient 



r = f° = R J_ 

 l <t> A 2c2 \B ) I 



One should not, however, overestimate the influence of the length correction. 

 For the spheroid 



a_1_ 1 



I C 2 



+ \ (i)°) t 1 + ' (if) 



i.e., influences the C 2 correction by less than 10 percent. Further, even 

 the introduction of the more important C factor does not lead to an exhaustive 

 correction since we know that not only the midship section but the whole 

 trend of the curves changes with increasing b/a. Thus within the limited 

 accuracy of the present wave-resistance theory we generally can put I /a = 1 . 

 It is of course important to use all approximations in a consistent and 

 clearly defined way, so that fair comparisons can be made. 

 We note particularly, that for the spheroid 



| = V C 2 b 2 /a 2 



