200 A, Hadjidakis 
As the behavior of a hydrofoil craft in the most unfavorable conditions is of decisive 
importance for its seaworthiness and comfort, the critical accelerations at A/lJ = 2/3 and 
d/l = 3/2 have been plotted in Fig. 8 as a function of craft length. This graph is valid for 
one speed only, i.e. 30 knots, which makes it possible also to show the variation of the 
Froude number with the craft length. The vertical acceleration at the bow for A// = lis 
also shown. 
a 
ris 
9 
—__ 
= 
= 
9 
So 
Aa) 
us 
wz 
Q 
a 
3 
Ge 
2 
ce) 
LENGTH OF CRAFT —=— 
Fig. 8. Maximum vertical acceleration at the bow for critical values of A// as a function of 
craft length / at a constant speed of 30 knots 
Of these curves the one for A// = 3/2 is the most important, because the critical accel- 
erations at A/I = 2/3 occur at relatively higher frequencies and can therefore be more 
easily attenuated or even eliminated by means of foil suspension or similar improvements. 
The influence of the speed of the craft is shown in Fig. 9, where the curve for \/l = 
3/2 has been drawn for five different speeds. Evidently the vertical acceleration is approxi- 
mately proportional to the square of the speed for a given craft length. 
Thus it can be stated that vertical accelerations decrease rapidly with increasing 
length of the hydrofoil craft, which means that the comfort, depending on the frequency of 
variation of the accelerations (jerk), improves even more rapidly. 
