4.4 Forward speed.

　

 In figures 4 and 5, the lateral force and yawing moment are non-dimensionalised making use of the square of the speed. Especially in shallow water, several curves are obtained for different speed values, indicating that lateral force and yawing moment cannot always be considered to be purely proportional to the square of the forward speed, but rather tends to follow a higher power.

　

 Figures 4 (Y: h/T=1.1) and 5 (Y: h/T=1.2) also show that the h/T value at which the attraction- repulsion transition takes place, is Froude number dependent: the transition occurs at higher h/T with increasing speed. This can be explained by squat effects, which tend to diminish the net under keel clearance.