Your hull speed is 1.32 X the square root of your waterline length period. On most sailboats, as you heel, the waterline length increases slightly, as does your hull speed. As a displacement boat moves through the water, it creates a bow wave. The faster the boat moves, the longer (measured crest to crest) this wave becomes. When this wave becomes as long as the waterline, the boat must climb over the wave it is creating. This is very obvious on a power boat transitioning to a plane. You can also feel this on sailboats that plane.