 A qualitative interpretation of the wave resistance plot is that a displacement hull resonates with a wave that has a crest near its bow and a trough near its stern, because the water is pushed away at the bow and pulled back at the stern.A planing hull simply pushed down on the water under it, so it resonates with a wave that has a trough under it.If it has about twice the length it will therefore have only square root (2) or 1.4 times the speed.