Lea and Feldman 
DISCUSSION 
irniest OF Guck 
Untverstty of Adelaide 
Adelatde, Australia 
Iam very please to see this done. One thing that bothers me 
is the condition that delta is order epsilon to the three halves. It seems 
very surprising that the theory should depend upon such a restriction. 
In my original linear theory, delta and epsilon were identical, and it 
seems unreasonable of a theory to demand such a geometrical cons- 
traint a priori. 
REPLY TO DISCUSSION 
George K. Lea 
Nattonal Setenee Foundatton 
Washington D.C., U.S.A. 
The odd power of 3/2 appears is due directly to the critical 
flow parameter Fyj-1. You must remember that the relation between 
€ and dis an artificial one, Their relative orders of magnitude are es- 
tablished through matching, with the a priori requirement that a rea- 
sonable solution can be obtainedas Fy,,~1. This type of proceedure 
must always be followed when more than one small parameter appears 
in the problem. The difference between this and your linear result is 
the difference between non-linear and linear approximations, 
DISCUSSION 
Ian W. Dand 
Nattonal Phystcal Laboratory 
Feltham, England 
We have obtained some measurements of sinkage and trim on 
tanker forms in sub-critical flow, but, using self-propelled and towed 
models. These showed that the effect of the propeller when the model 
was self-propelled was such as to modify appreciably the measured 
trim. I have two questions asa result. 
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