Hydrofoil Size and Seaworthiness 201 
be 
F] 
VERT. ACCELERATION 
° 20 0 60 1206. 
LENGTH OF CRAFT) —=— 
Fig. 9. Influence of the speed on the maximum vertical acceleration at the bow as a function of 
craft length for the critical value A/J = 1.5 
CONCLUSIONS 
Assuming that the wavelength and height are proportional to the length of the hydrofoil 
craft, in other words, that a craft of double length is running on waves which are twice as 
long and high, it may be concluded that: 
1. On a following sea, where maximum pitch is the critical factor, the seaworthiness is 
nearly unaffected by size. Actually the seaworthiness improves slightly with decreasing 
Froude number, i.e., increasing length. 
2. When going against the waves, vertical accelerations are critical, which, with 
increasing length of the craft, decrease more than proportionally with the Froude number. 
Consequently the seaworthiness increases with the length of the craft, the more so 
when the comfort is taken into consideration. 
LIST OF SYMBOLS 
a = angle of attack (effective) 
b = maximum span of hydrofoils 
C; = lift coefficient 
c = _ speed of wave propagation 
