Yamazaki 



where C^DoivO, ^r(Vi), and hj^(j]^) are constants to be determined experimen- 

 tally depending on the section shape and the surface roughness of the rudder. 

 The nondimensional components of the force and moment acting on the rudder 

 except Kjjp^ can be expressed approximately by only the terms due to the pres- 

 sure difference of both sides of the mean surface Sr, since the terms caused by 

 viscosity can be negligibly small. That is, we have, for example, 



ju ,1 r 



(SR) 



^RMx '^ 8 



I ^id^i I gR(^l.u,s)j[V*] 



dT7j dT7j 



^^m(^i) ^^UvO 



>-du 



(SR) 



dT7^ 



d77j 



(SR) 



y (SR) 



(48) 



Finally we consider the force and moment acting on the propeller (6,8). 

 Since the magnitude of the suction force at the leading edge of the propeller blade 

 is considered to be much smaller or at most the same order compared with the 

 section viscous drag, we may safely neglect it or take it to be included formally 

 in the viscous drag in this paper. Since the blade surface is closed and the blade 

 thickness is very thin, the direct effect of blade thickness on the forces is negli- 

 gibly small. Thus the force and moment acting on the propeller are generated 

 mainly by the vortex systems. We denote the components of the force in the x^, 

 Yj, and Zj directions by F,^, Fy, and F^ respectively, we denote the components 

 of the moment about the Xj, y^, and z^ axes by M^ , My, and M^ respectively, 

 and we define the nondimensional coefficients as 



Then these coefficients are expressed as 



^^'^'I'^^I L^-'^''' Kpy = j df I ^ (K^cos^b-K, sin^t,) dv, 



^B " 1 k= 1 ^B " 1 k= 1 



1 1 N J 1 N 



1 1 N 



(49) 



1 IN 



(50) 



30 



