128 M. P. Tulin 
RMS Vertical Velocity in ft/sec 
Depth Below Free Surface in feet 
Fig. 4. Effect of depth on vertical velocities 
in a seaway 
Frequency of Encounter, w, in rad/sec 
6 
Sea State 
2 
4 
2 Ya 
fe) a a 
80 60 40 20 (0) 20 40 60 80 
—— Into Wind Boat Speed in knots With Wind —=— 
Fig. 5. Frequencies with which a boat encounters waves of 
various sea states corresponding to various wind speeds 
