T. H. HAVELOCK 
4 oR d 7/2 
p=-Spngo?| Sarl af| e “olf-z)sec ? 6 
—l 0 0 
x cos{x .(— A) sec otsec30dé. (5) 
The horizontal component of this pressure integrated over the surface 
of the ship gives the wave resistance; it may be noted that, with the 
usual approximation, we evaluate the pressure not at the actual sur- 
face of the ship but over the plane y = 0. We use this expression 
similarly for evaluating the moment of the pressure about the trans- 
verse axis Oy. Consider the total moment in two parts. First, for 
the horizontal component of the pressure, the moment will be of the 
order of the wave resistance multiplied by some fraction of the draft; 
it is found that this part is small compared with the moment of the 
vertical component and we neglect it meantime. However, when com- 
paring calculated and experimental results we allow for this correc- 
tion by estimating the moment of the total resistance of the model. 
For the moment of the vertical component of the pressure we have 
M = few dz dy, (6) 
taken over the water plane section of the ship, with p given by (5). 
3. We confine the calculations to a simple type of symmetrical 
model used at Teddington, for which experimental results are avail- 
able, and for which the numerical calculations are not unduly labori- 
ous. This set of models is defined by 
y=0(1-47)(1 + 0, %)(t ~3r) (7) 
For this form, we have 
l 
8 h ne 
p(2,2) = pond | {a — a) pt 2a, a dh x 
l 
d 
2 7/2 
[Galan 
0 
0 
x cos{« (x -A) sec 6}sec*9d6, (8) 
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