Faltitnsen 
given wave length the amplitudes of the pressure, force and moment 
for a given forward speed can be obtained from the corresponding 
values at zero-speed by multiplying the zero-speed results by acons- 
tant factor. 
V.2. Comparison with Experiments 
C.M. Lee has measured the pressure-distribution along a 
restrained, semi-submerged, prolate spheroid which was towed ata 
constant speed in regular head-sea waves. He used the experimental 
pressure values to calculate a longitudinal force distribution along 
the spheroid (C.M. Lee (1964) ). He did not publish the data for the 
pressure distribution along the spheroid, but he was kind and gave us 
those data. 
The surface of the prolate spheroid that C.M. Lee used can 
be described by the equation : 
2 DRETZ 
x +47 = 1, 
2 2 
=> 
om 
oO 
where { = 19.8" and bg = 3.3". x,y,z are defined by Figure 1. 
He measured the pressure at cross-sections located at x = -16" 
(called Cy), x= - 12.5" (called Bp), x=-7" (called Ap), 
x = 0 (called (QD), x = 7" (calledAy), x= 12.5" (called By), 
x = 16" (called Cy). He did the experiments for } /L = 0.5, 0.75, 
1.0, 1.25, 1.5 and 2.0 where A is the wave length and L is the 
length of the model. The Froude numbers of the model were F,, = 
0..0827,0.,.123, 0. 164,, 0..205,. 0. 246, 07526. 
In our theory we have assumed that the wave length is of the 
order of magnitude of the transverse dimensions of the ship. But 
note that this does not necessarily mean that the theory is bad for 
larger wave lengths. One can refer to the strip theory which has 
shown to give good results for a wider range of wave lengths that one 
rationally has to restrict oneself to. The comparisons with the ex- 
periments by Lee seems to indicate that our theory is not good for 
wave lengths \ /L= 0.75 and larger. We will therefore only show 
the comparisons for A/L = 0.5. 
There were evidently some irregularities in the experiments 
1806 
