THE EFFECT OF WAVES UPON A TAFFRAIL LOG. 125 
exactness; they, of course, correspond to the speeds of maximum and mini- 
mum wave interference and the theoretical conception of these speeds has 
been verified by experimental work in towing basins and elsewhere. The 
speed of a trochoidal wave is definitely represented by the following formula: 
Vy a 
Pe Ua C=1.34V) 
where 
c= speed of advance of crest, in knots. 
g= acceleration due to gravity in feet per second. 
\= length from crest to crest of one wave. 
The wave making length of a ship is slightly larger than the length between 
perpendiculars from 1.05 to 1.2 according to Naval Constructor D. W. 
Taylor, U. S. N.,* and if we let m represent this factor and L the length 
between perpendiculars of the ship me will be the number of waves there 
are between the first transverse ‘crest of the bow and the first transverse 
crest of the stern systems. When this is a whole number the resultant 
waves at the stern are at their maximum height and when it has a value of . 
half units the waves will be neutralized. 
Now as c=1.34 Vy 
and 
mL 
oa ae number of waves 
we have C=1.34'd 
3 1.795 mL 
Zs 
nN 
and ee =number of waves= aS 
mL _1.795m 
whence Mi [ ee 
s 
so that assuming different numbers of waves and solving for the speed of 
the ship corresponding, we get the results shown in Table I for a ship 188 feet 
long between perpendiculars. 
From this, at the speeds of 14.05, 11.05, 9.18 and 7.75 knots we should 
expect the variation of the log constant from the still-water line (A-B) to 
*Speed and Power of Ships. 
