Abstract: Methods are disclosed to design resilient hydrofoils (164) which are capable of having substantially similar large scale blade deflections under significantly varying loads. The methods permit the hydrofoil (164) to experience significantly large-scale deflections to a significantly reduced angle of attack under a relatively light load while avoiding excessive degrees of deflection under increased loading conditions. A predetermined compression range on the lee portion of said hydrofoil (164) permits the hydrofoil (164) to deflect to a predetermined reduced angle of attack with significantly low bending resistance.

Abstract: Methods are disclosed for increasing lift and decreasing turbulence and drag on hydrofoils and swim fins. Fins are disclosed having at least one pivoting blade region connected to the swim fin with a flexible joint element made from reduced blade thickness, blade cutout regions, and injection molding of the flexible material of the foot pocket. Methods are also provided for limiting the deflections of at least one pivoting blade region with a movable blade limiting member connected to both the pivoting blade region and a blade limiting load bearing member with a chemical bond created during molding. Methods are disclosed for orienting at least one pivoting blade region at a reduced angle of attack sufficient for increased efficiency and reduced effort. Injection molding assembly methods with chemical bonds and mechanical bonds are provided. Fins having transverse flexible elements, transverse recesses, longitudinal recesses and venting systems are also disclosed.

Abstract: Methods are disclosed for increasing lift and decreasing drag on hydrofoils and swim fins. These methods include providing a hydrofoil with a highly swept back leading edge portion and orienting the hydrofoil at a significantly reduced angle of attack in which the reduced angle of attack occurs at an angle that is substantially transverse to the hydrofoil's direction of movement through a surrounding fluid medium. The lee surfaces of the hydrofoil is provided with a substantially unobstructed flow path as well as a separation reducing contour so as to permit lift generating attached flow conditions to form along such lee surfaces. Substantially rigid structural reinforcement is provided to prevent the hydrofoil from deforming significantly during use. Methods are disclosed for providing a hydrofoil with a substantially longitudinal recess or venting system located substantially along the center axis of the hydrofoil.

Abstract: Methods are disclosed to design resilient hydrofoils (164) which are capable of having substantially similar large scale blade deflections under significantly varying loads. The methods permit the hydrofoil (164) to experience significantly large-scale deflections to a significantly reduced angle of attack under a relatively light load while avoiding excessive degrees of deflection under increased loading conditions. A predetermined compression range on the lee portion of said hydrofoil (164) permits the hydrofoil (164) to deflect to a predetermined reduced angle of attack with significantly low bending resistance.

Abstract: A hydrofoil and swim fin is provided for increasing lift and decreasing drag. In a preferred embodiment, the hydrofoil has a swept back leading edge and is oriented at a reduced angle of attack substantially transverse to the direction of movement of the hydrofoil. Structural reinforcement may be used to inhibit hydrofoil deformation during use, and a recess may be incorporated into the hydrofoil to direct fluid flow with respect to the hydrofoil surface. Torsional stress that acts on the hydrofoil when in use is also addressed.

Abstract: Methods are disclosed for increasing lift and decreasing drag on hydrofoils and swim fins. These methods include providing a hydrofoil with a highly swept back leading edge portion and orienting the hydrofoil at a significantly reduced angle of attack in which the reduced angle of attack occurs at an angle that is substantially transverse to the hydrofoil's direction of movement through a surrounding fluid medium. The lee surfaces of the hydrofoil are provided with a substantially unobstructed flow path as well as a separation reducing contour so as to permit lift generating attached flow conditions to form along such lee surfaces. Substantially rigid structural reinforcement is provided to prevent the hydrofoil from deforming significantly during use. Methods are disclosed for providing a hydrofoil with a substantially longitudinal recess or venting system located substantially along the center axis of the hydrofoil.

Abstract: Methods for using tip generated vortices to improve performance of foils. These methods include generating a substantially streamwise beneficial vortex (74) near the outboard end (60) of a foil (82). This beneficial vortex (74) spins in the opposite direction of an induced drag vortex (62), and is used to create an upwash field (76) which neutralizes induced drag by deflecting the flow behind the trailing edge (56) at an upward angle. Upwash field (76) causes the lift vector (118) on the foil (82) to tilt forward, thereby creating a forward directed force of induced thrust upon the foil (82). Beneficial vortex (74) is also used to contain and compress the high pressure field existing along the attacking surface of the foil (82), and displace the induced drag vortex (62) inboard from the tip of the foil (82). Numerous performance parameters are improved dramatically by using beneficial vortex (74), as well as by using a double vortex pattern (124).