Abstract: A boat comprising a tread drive system including pedals which are adjustable to the size of the operator. An axle extends through the bottom of the boat at the center of the tread system and is connected for oscillating movement therewith, the axle carrying at its lower end a horizontal swing arm. A vertical fin is mounted on the free end of the swing arm for pivotal movement relative thereto. The fin is a flat rigid plate which is tiltable between angular stops. The fin widens rearwardly and is confined by top and bottom baffles. The fin is arranged beneath the center area of the boat between an aft stabilizing fin and a front fin acting as a rudder whose pivot bearing may be coaxial with that of the tiltable fin. The aft stabilizing fin corresponds in size and shape to the rudder and is rigidly fastened to the bottom of the boat near its stern, preferably underneath the seat area for the operator. The boat is steered by a horizontal tiller or steering wheel joined to the upper end of the rudder shaft.

Abstract: A minimum drag fluid reaction element including a rotatable shaft adapted to be supported by a vessel carried upon or within a fluid medium; and a rigid fluid reaction fin fixedly attached to the shaft for extension into the fluid medium, the shaft and the fin extending in opposite directions from a common intersection and forming an angle other than a right angle therebetween; the axis of rotation of the shaft lying in a plane generally normal to the fin whereby rotation of the shaft moves the fin through a path describing a right conical section. The angle between the fin and the shaft is preferably obtuse and the plane containing the axis of rotation of the shaft peripherally bisects the fin.

Abstract: A surfboard fin is disclosed which is formed of shaped plastic opposed members which are joined and sealed to form a hollow light-weight buoyant construction, which provides an external contour to reduce drag in surfboarding. The novel profiled plastic surfboard fin is readily mounted to conventional boards and replaces the present conventional fiberglass fins.

Abstract: A keel assembly or similar fin-like underwater appendage for a boat is provided which is adjustable to adapt its characteristics to the operating conditions of the boat, for example to optimize hull performance of a sailing boat on opposite tacks. The assembly comprises a support and a pair of curved flexible side plates carried by the support and connected at their leading and trailing edges, the curvature of the side plates being adjustable to render the assembly asymmetrical. The leading and trailing portions of the plates are provided by blade assemblies interconnected so as to be oppositely pivotable about axes parallel to leading and trailing edges of the support, the trailing blade assembly having its pivoted axis adjacent its leading edge.

Abstract: A sailboat having a hull, a sail assembly and a keel. The keel is shaped as a longitudinally and horizontally extending hydrofoil which developes a vertically downward force. When the boat is traveling in a heeled position, the keel member exerts a downwardly and outwardly directed keel force having a lateral force component to substantially counteract an opposite lateral aerodynamic force component exerted by wind against the sail assembly, thus diminishing the yaw angle in the travel of the boat. Further, the keel force acts through the center of gravity of the boat to produce a righting moment which tends to counteract the capsizing moment developed by the force of the wind against the sail assembly.

Abstract: A small, wave-following, relatively stable marine buoy designed for floating at the surface of a body of water and for carrying data measuring equipment. The buoy comprises a buoyant hull member of substantially cylindrical configuration of relatively small axial extent, a mast, and a keel. The keel comprises a spar and a ballast weight attached to the spar. Both the mast and the keel are guyed to the hull at opposite ends thereof, and supported thereagainst by couplings which do not transfer bending moment between the hull and each of the mast and spar.

Abstract: A sailboat keel, especially for shoal draft sailboats, which reduces turbulence and generated vortices and increases laminar flow along the hull and keel, which comprises a upper portion attachable to the canoe hull and a body portion extending downwardly from the upper portion, the body portion flaring outwardly so as to have a maximum width at its plane of intersection with the keel bottom which is preferably smoothly curved.

Abstract: A stabilizer keel for water surface vehicles. The keel includes a pair of pivoted keel plates that are pivoted on a stationary base member by an integral hinge. The plates are urged apart about the axis of the hinge to normally form a V-configuration for the purpose of stabilizing the object to which the keel is mounted; for example, a water ski. The hinge axis is inclined so the plates, when in the open, V-configuration, will lift upwardly against the ski upon movement of the ski in a forward direction. As forward velocity is increased, pressure against the plates also increases, causing them to swing inwardly against resistance of the spring. Thus, at relatively high speeds, the plates come together to form a substantially standard shaped keel.

Abstract: A sailboat, and a variable foil appendage, ie., keel or rudder for a sailboat, the appendage having a central core portion, and movable skin portions on either side thereof, the skin portions being connected to the core portion essentially along the forward and trailing edges of the skin portions, at least one of such connections being movable, and a fluid-operated skin movement control system being provided in the core portion, operation of the control system producing outward bulging or flattening of one or other of the skin portions to form a bulged generally convex profile extending upwardly and downwardly along one side of the core portion, while the skin portion on the opposite side of the core may be bulged or flat, the control system being selectively operable thereby enabling the foil section of the appendage to be changed, as the sailboat comes about from one tack to the other.

Abstract: A boat is provided having front and rear ends, a bottom and upwardly projecting sides extending upwardly to an elevation spaced above the static water line of the boat. A depending central strut (fixed or upwardly retractable) projects downwardly from the bottom and a pair of elongated downwardly convergent opposite side flexible foils including leading and trailing longitudinal edges facing in front and rear directions, respectively, of the boat are provided and have their lower ends anchored to the lower end portion of the strut. The upper end portions of the foils are anchored relative to upper portions of the corresponding sides of the boat above the static water line thereof outwardly of the boat sides and the foils are free of support from the boat intermediate the upper and lower ends of the foils.

Abstract: A sailboat pivotally carries a pair of weighted complementary shaped keels for independent rotation about a common longitudinally directed medial hinge axis for influencing the roll, moment of inertia and draft of the boat. The keels are independently supported at variable angles with respect to the vertical by lines directed upward along opposite sides of the boat. The upper ends of the lines are attached to a winch mechanism within the boat which includes one rotatable drum for varying the angle between the keels while maintaining the orientation of the angle bisector substantially constant and another rotatable drum for varying the orientation of the angle bisector while maintaining the angle between the keels substantially constant. A bolt carried slideably by the keels selectively locks the keels together for rotation as a unit. The bolt is remotely operated from within the boat via a controlling cable.

Abstract: A sailboat hull adapted to receive a mast and sailboat rigging with an interior concave keel forming an interior walkway. The keel is sufficiently deep and open to allow one to walk in the keel to provide sufficient head room for a person of normal height. The keel sides have a relatively vertical relationship to the bottom of the boat, and also has a relatively flat bottom. The upper hull itself has a substantially flattened bottom and sides extending from the transom forwardly in substantially vertical relationship to provide a substantially "stiff" sailing performance to the boat. The sides and bottom are configured so that a substantially geometrically normal angular relationship between them is maintained along a substantial portion of the length of the hull.