All boats are displacement boats at rest. What makes a boat plane is speed and the shape of the hull. basically a planing hull has a square stern. A displacement boat narrows at the stern so less energy is needed to move the boat at slow speed. The length of the hull is a major factor in higher speed efficiency. So a planing hulll travels on top of the water, while a displacement hull travels through the water. So what about our latest fast attack boats which have two torpedo like power pods under water while the main platform rides above the waves ? How would you classify hydrofoils ?
