Free Surface Effects tn Hull Propeller Interaction 
this is what we have called the self-induced wave wake. Ambient 
waves caused by wind or moving objects other than the hull and pro- 
peller have not been considered in our paper. 
Professor Telfer's final comment deals with the Hughes- 
Prohaska method of determining form factors and the value obtained 
for our model, Taking the value first, we agree with him that if the 
two-dimensional plane friction formula is assumed to be 
2 
Goin. minis 901 MOB eB 2) 
then the ''true"' form factor for our model becomes 1.025 - 75/67 = 
1.15. The length/breadth ratio of a flat plate ane gris to a sub- 
merged double model of our hull form would be L 2/s = 5.79... From 
Figure 10 of Hughes (1954) we find that the form factor of sucha 
plate arising from three-dimensional edge effects would be about 1.11, 
which compares well with our value for the model. We do not know 
how Professor Telfer derived his minimum value of 1.225. Turning 
now to the method itself, we have followed the Hughes (1963) idea as 
reflected in our Equations (7) to (11) because it is consistent with our 
data (see Figure 4) and the linearized theory of the wave resistance 
of thin ships. In fact our Equation (B28) for the theoretical wave re- 
sistance can be shown to have the asymptotic representation : 
_ 2048 5 
i ering Cg, "= sais. 8h b“/s) F = * + 0(F_”) ~ 3.15 F 
4 
That the measured coefficient, see Equation (12), is only about 1/4 
of the theoretical value may be explained by the fact thatas F,—s0 
the stern becomes almost totally ineffective in wavemaking. - We 
agree with Professor Telfer that if extrapolation rather than analysis 
were our goal, the most direct and reliable method would have been 
to test geosims., 
To Professor Weinblum 
We are most grateful to Professor Weinblum for his kind re- 
marks ; the comparison with Dickmann's legendary work is almost 
too much of a compliment. His reference to the work of Yamazaki, 
Nakatake and Ueda (1972) is very much to the point. This is evidently 
the most comprehensive theoretical study of the complete interaction 
problem of hull, propeller and rudder published to date. Due to the 
complexity of the problem we decided to restrict our study to the 
simpler hull-propeller system. The interaction between propeller 
and rudder has been theoretically calculated also by Isay (1965) and 
Lo5i7, 
