High efficiency hydrofoil and swim fin designs

A method for connecting a pivoting blade region to a propulsion hydrofoil, comprising connecting said pivoting blade region to a load bearing structure with a flexible thermoplastic hinge element, said flexible thermoplastic hinge element being made with a relatively flexible thermoplastic material, said pivoting blade region being made with a relatively stiffer thermoplastic material, and said relatively flexible thermoplastic material being connected to said relatively stiff thermoplastic material with a thermal-chemical bond created during a phase of injection molding.

A method for providing a swim fin, comprising:

• (a) providing a foot attachment member;
• (b) providing a blade member connected to said foot attachment member and forming a forward extension of said foot attachment member, said blade member having opposing surfaces, outer side edges, a root blade portion adjacent said foot attachment member and a blade free end spaced from said root blade portion and said foot attachment member, said blade member having a longitudinal midpoint between said root blade portion and said blade free end, said blade member having sufficient flexibility to flex around a transverse axis from a neutral blade position to a reduced angle of attack during use;
• (c) providing said blade member with at least one enclosed vent disposed within at least one of said opposing surfaces, at least one portion of said at least one enclosed vent being located forward of said longitudinal midpoint.

A method for connecting a pivoting blade region to a propulsion hydrofoil, comprising connecting said pivoting blade region to a load bearing structure with a transverse flexible thermoplastic hinge element, said transverse flexible thermoplastic hinge element being an elongated region of reduced blade thickness that is molded within said pivoting blade region during injection molding, and providing said transverse flexible thermoplastic hinge element with sufficient flexibility to permit said pivoting blade region to experience pivotal motion around said transverse flexible element during use.

A swim fin comprising:

• (a) a foot attachment member;
• (b) a blade member molded to said foot attachment member with a chemical bond, said blade member having a root portion adjacent said foot attachment member and a free end portion spaced from said root portion and said foot attachment member, a recess disposed within said free end portion of said blade member, said a recess sufficient to divide said free end portion into two tip portions, said recess defining inner edges of said blade member, at least one of said inner edges having a first inner edge portion having a first inner edge alignment, said first inner edge alignment being more longitudinally oriented than transversely oriented, said at least one of said inner edges also having a second inner edge portion having a second inner edge alignment, said second inner edge having a different alignment than said first longitudinal alignment.