Abstract: The invention comprises a waterborne craft having a hull, board or base, and a fin, keel, centerboard or the like. One or more air conduits exit the hull, board or base at or adjacent at least one side of the fin, keel or centerboard, or exit the fin, keel, or centerboard, excluding the leading edge of the fin, keel or centerboard in use, in a position such that the conduit in use provides or the conduits in use provide air to a position at or adjacent at least one side of the fin, keel or centerboard.

Abstract: The invention comprises a waterborne craft having a hull, board or base, and a fin, keel, centreboard or the like. One or more air conduits exit the hull, board or base at or adjacent at least one side of the fin, keel or centreboard, or exit the fin, keel, or centreboard, excluding the leading edge of the fin, keel or centreboard in use, in a position such that the conduit in use provides or the conduits in use provide air to a position at or adjacent at least one side of the fin, keel or centreboard.

Abstract: Keel or fin (1) for a watercraft such as a surfboard is conventional in shape but comprises major portion (2) fixed to the board by peg (10) and minor, flexible, trailing portion (3) fixed to major portion (2). Minor portion (3) has a more rigid leading edge (16) which slides dovetail fashion onto trailing edge (8, 9) of major portion (2) and is locked in place by grub screw (7). Minor portion (3) has core (11) of rubber allowing it to flex sideways under water pressure. Excessive movement of trailing edge (12) of minor portion (3) is prevented when edge (12) contacts stops (4) positioned on either side on the board. Minor portion (3) may be completely surrounded in an aperture in major portion (2) or may have apertures to which air is fed via ducting.

Abstract: Keel or fin (1) for a watercraft such as a surfboard is conventional in shape but comprises major portion (2) fixed to the board by peg (10) and minor, flexible, trailing portion (3) fixed to major portion (2). Minor portion (3) has a more rigid leading edge (16) which slides dovetail fashion onto trailing edge (8, 9) of major portion (2) and is locked in place by grub screw (7). Minor portion (3) has core (11) of rubber allowing it to flex sideways under water pressure. Excessive movement of trailing edge (12) of minor portion (3) is prevented when edge (12) contacts stops (4) positioned on either side on the board. Minor portion (3) may be completely surrounded in an aperture in major portion (2) or may have apertures to which air is fed via ducting.