Abstract: A method of attaching a fin to an adjustable fin holder of a surfboard or sailboard that protects the fin, fin holder and board structure around the fin holder from damage if the fin strikes an under water object.

Abstract: A high-speed planing catamaran is comprised of hulls, each of which has a canard planing surface well forward of the catamaran's center of gravity and a main planing surface aft of and closer to the center of gravity. At planing speeds, the canard surface leaves a trough in the water which substantially encloses the hull portion aft of the canard surface. The main planing surface rides on water between the hulls, but outside the trough. The angle of incidence of all surfaces may be adjustable, as may the vertical and lateral positions of each hull's propeller.