Originally Posted by jeffstevens763@g
do you think, and that in the rough its better since the floor can straiten in the troughs between waves [somewhere to go] whilst on the flat its not got any room to move [totally supported]?
OK - so my theory is that on flat calm you have a seal around the hull. When the revs get up there is a suction under the boat, essentially the prop is pulling the water out from under the keel and causing the bulge at the rear, this in turn causes the front (under the petrol tank) to be forced into the void/pressurised area under the aft/before the prop and you get the characteristic concave/convex wave shape in the floor.
In rough water the suction cannot build up as the seal around the hull is incomplete and thus the effect is significantly reduced...
That's my take on it anyway...