Ship Maneuvering in Deep and Confined Waters 



concentrated to the leading edge as in case of a rectangular wing but 

 distributed over the forebody as an effect of fullness and section 

 shape. Certain modifications to the hull form are known to affect 

 the force derivatives, but do not appear in the simple form 

 parameters of Table III. The fin effect of screw and rudder con- 

 tributes to the derivatives even in the case of vanishing aspect ratio 

 of the hull. 



From the analysis of a large number of derivatives it has 

 been found that the scatter of data in a plot of, say, Yj^ versus the 

 parameter LT /V is somewhat smaller than the scatter of Y^ on 

 base of aspect ratio 2T/L. 



The diagrams Fig. 11-12 include stability derivative data 

 for normal ship form models with normal-sized rudders propelled 

 at medium Froude numbers on even keels. The dotted lines shown 

 correspond to the simple wing analogy. The full lines are derived 

 by linear regression and upon the tentative assumption of a - 1:2 

 relation of moment and force intercepts at zero aspect ratio. Their 

 equations are given as 



"Over- 

 lapping 



6 08 



LT2/ V 



06 0-8 



LT^/V 



Fig. 11. Stiffness force and moment derivative data with mean 

 regression line. (Cubic fit to experimental results.) 



841 



