Also, a mode of movement in windsurfing (and other kinds of speedsailing as well) when the board does not cut through the water, displacing it, but rather slides over the surface. Naturally, it is much faster than the displacing mode, and much more fun. Most windsurfers don't even consider sailing if the wind is not enough to plane . Normally, about 12 knots is required for an average shorboard to start planing, although specialised boards start planing at considerably lower winds. By the way, sailing in planing conditions is sometimes called funboarding.
When planing, the windsurfer commits most of her weight to the sail through the boom, either hanging with the hands or using a harness. The foot pressure is only used to compensate the lift produced by the fin, in other words, just to keep the board flat on the water.
The speed is inversely proportional to the wetted surface of the board. Thus, to increase the speed when planing (which is often quite enough to scare anyway -- up to over 40 kt) the fin and the mast base have to be mounted closer to the back of the board.