238 H. von Schertel 
Boat not foilborne 
| travel at full power 
Height of Waves 
0 20 71) 60 80 100 120 
length of boat ft ——=— 
Fig. 4. Limits of seaworthiness of Supramar boats 
readings of the maxima taken during a period of 4 minutes. The roll angle is, of course, at 
its maximum in a beam sea. Compared with displacement boats of similar size, however, 
that angle is still small and the angle of pitch is very small indeed. 
Figures 6 and 7 show the influence of speed or Froude number respectively and of 
wavelength on the vertical accelerations of a surface-piercing front foil. These diagrams 
are taken from a hitherto unpublished theory developed by Mr. de Witt of the scientific staff 
of Supramar. For the accelerations shown in the figures the most unfavorable course of the 
boat in relation to the direction of the waves was assumed in each case. The thick curve 
ling one 
sabe 
<—ei——Wa ve——— > airection ——=— cea 
Fig. 5. Mean values of pitching and rolling in rough water for the 
PT 50 (wave height, 5 to 6-1/2 feet; wavelength, 100 to 150 feet) 
