Savitsky 3 Roper 3 and Benen 



are closely represented by a single curve relating the data to L/v 1 /3. 

 Similar plots for other hull series are given in Reference 6 and also 

 indicate the pronounced dependence of low speed resistance on slen- 

 derness ratio. Using these results as a guide, it is concluded that a 

 value of L/v 1 /3 equal to at least 7. is essential for low resist- 

 ance at pre-hump speeds. For a displacement of 150, 000 lbs. , this 

 results in a minimum hull length of 92 ft. 



Comparing this criteria with possible combinations of 

 hull dimensions of page 429, it is seen that a hull beam should be at 

 least equal to or greater than 14 ft. This limitation is also plotted on 

 Figure 6. 



Metacentric Stability 



The specified requirement for metacentric stability is that 

 the GM be equal to at least 3.0 ft. An engineering estimate of GM 

 for a planing craft with deadrise is made using the following assump- 

 tions. 



KB =-| d = -f (3.5) = 2.33 ft. 



1 3. 



I = water plane moment of inertia = .55 (— L B ) 



Preliminary weight estimates for the present design showed that the 

 vertical center of gravity of the craft, KG, is 6. 2 ft. above the Keel. 

 Considering a minimum boat lenght of 92 ft. , as determined from 

 the low speed requirement, the following values of GM are comput- 

 ed for each assumed beam. 



430 



