CHAPTER VIII 



EFFECT ON RESISTANCE AND DHP OF VARIATION 

 IN SHIP PROPORTIONS 



The experiments described in the last section showed that the original choice of LCB 



positions had not been too far from the optimum, although improvement could be obtained in 



certain areas. For the final series of experiments, in which the effect of variation in Cg , 

 A 



L B 



— , — , and / Z/ « upon resistance and propulsive efficiency were determined, the five 



B H 



(— T 



Vioo/ 



models chosen as parents were those of the LCB series having the LCB in the position 

 nearest to the optimum. 



Cb 



0.60 



0.65 



0.70 



0.75 



0.80 



Model Number 



4210 



4218 



4221 



4213 



4214 



LCB as Percent Lgp 

 from 25g p 



1.5 aft 



1.54 aft 



0.55 aft 



1.5 fwd 



2.5 fwd 



LCB in Original 

 Series 60 Parents 



1.5 aft 



0.5 aft 



0.5 fwd 



1.5 fwd 



2.5 fwd 



It will be seen that the change involves a movement of the LCB aft in the 0.65 and 0.70 C g 

 models. The models chosen for the final phase are also indicated in Figure 1. In developing 



this geometrical series, the assumption has been made that the optimum location of LCB for 



' L B _ 



the model having the — and — ratios of any one parent will remain near-optimum with 



L B^ ^ 



changes of — and — for the same block coefficient. This assumption has not been tested 

 B H 



in the present research, but any other would have led to a great extension of tiie test program. 



Paving chosen the new parents, eight additional models were made for each block 

 coefficient, making a total of 45 models in all, including the original parents. 





L 

 VARIATION OF — AND 



B 



— RATIOS 



H 



Cb 



Ran/ 



^e of Variation in 





L 



B 



A 





B 



H 



(L/100)3 



0.60 



6.5-8.5 



2.5-3.5 



67.8-162.4 



0.65 



6.25-8.25 



2.5-3.5 



78.0-190.3 



0.70 



6.0-8.0 



2.5-3.5 



89.3-222.4 



0.75 



5.75-7.75 



2.5-3.5 



102.0-259.3 



0.80 



5.5-7.5 



2.5-3.5 



116.2-302.4 



A typical pattern of the variation (for C g = 0.60) is shown in Figure 2. 



VlII-1 



