Chine

A chine is a sharp longitudinal edge where two hull surfaces meet at an angle instead of a fair curve, most often the corner between the bottom and the topsides on a planing or hard-chine hull. The chine fixes the line where flow separates cleanly off the hull, which is what lets a planing craft lift and shed spray rather than drag a rounded bilge through the water. A single hard chine defines a V-bottom planing hull; multiple chines approximate a round bilge with developable plate panels, which simplifies construction in steel, aluminum, or plywood. Round-bilge displacement hulls have no chine. The chine angle and its rise above the keel set the deadrise and govern lift and ride in waves.