30 



a. Prom resistance curves calculated by Sretensky^* 



1 . n 2 1 .4- for 0.30 > F > 0.235, and 



2. n ~ 1 .6 for higher Proud e numbers 0.7 > P > 0.1+7; both are 

 valid in the neighborhood of H/L = 1/20. 



b. Using Wigley's paper the following data are obtained: 



1. n ~ 0.85 for 0.23 > P > 0.l8, 



2. n ~ 1 .3 to 1 .5 for the second hump 0.32 > F > 0.26. 



3. n ~ 1 .3 to 1 .7 for the first hump 0.6 > F > O.36. 



It seems that on the average the exponent n is higher for finer 

 ship forms. In Wigley's case the range of H/L is 



T^^ L ^32 



Mumford's curve agrees reasonably with theoretical computations for 

 the first hump; in the range of lower Froude numbers empirical values are 

 smaller than the theoretical ones. 



Using Michell's integral, both of the following cases, c and d, can 

 be easily derived from the two basic ones (a and'b). 



c. A number of well known experiments can be classified under the con- 

 ditions: BH = const, A^ = const and displacement constant. 



These are the sets of Taylor's Standaiid Series*^ B/H = 2.25 and 

 B/H = 3-75, Ackerson's Series, ■"■ Rota's, *■'■ and Kent's^'' experiments. 



Obviously, the wave resistance R increases with increasing B/H, as 

 the beam contributes more to the drag than the draft, although the total re- 

 sistance may change only slowly within a length/beam ratio 10 > L/B > 8. No 

 theoretical analysis has been applied to this case. 



d. In this case B/H = const; L/B and L/H are variable (similarity 

 transformation) and displacement varies with B^ . This problem has been studied 

 most thoroughly by D.W. Taylor,"*^ Ackerson,-"- and Bragg. ^ The displacement- 

 length ratios of the Taylor Standard Series models were varied by similarity 

 transformations. A comparison has been made between calculated and measured 

 resistances for sets of models defined analytically and run in the Berlin 

 Tank.*** 



The wave resistance grows very rapidly with increasing B, and the- 

 oretically with the fourth power for extreme values of P. For L/B = 6 the 

 theoretical values are excessive. 



