Constant-pressure planing

Constant-pressure planing is the idealized planing condition in which the dynamic pressure over the wetted bottom is taken as uniform rather than peaking at the spray root, a simplifying model used to derive lift and wetted-area relations for planing surfaces. The real pressure distribution on a planing plate rises to a stagnation peak at the spray-root line where the rising sheet meets the bottom, then falls aft; assuming a constant mean pressure replaces this with one representative value, which eases the bookkeeping of lift L = p A and the location of the center of pressure. It underlies the lift-coefficient correlations behind the Savitsky method and the comparison of planing surfaces of different deadrise, where stagnation-line geometry corrects the idealization.