Patent ID: 6843693

Claim:
A method for improving a swim fin, comprising: (a) providing a foot attachment member; (b) providing an active portion connected to said foot attachment member and forming a substantially forward extension of said foot attachment member, said active portion having a root portion adjacent to said foot attachment member and a blade free end portion remote from said root portion and said foot attachment member, said active portion having a predetermined longitudinal dimension between said root portion and said blade free end portion, said active portion having a longitudinal midpoint between said root portion and said free end portion, said active portion having a first half portion between said root portion and said midpoint, said active portion having a three quarter position that is located midway between said midpoint and said free end portion; (c) providing a hinging region disposed within said first half of said active portion, said hinging region being a region of increased flexibility within said swim fin, said active portion having a pivoting blade portion forward of said hinging region, said hinging region being arranged to permit said pivoting blade portion to pivot around a transverse axis to a deflection of at least 10 degrees from a neutral position to a deflected position under a relatively light load condition such as created during a relatively light kicking stroke used to achieve a relatively slow swimming speed, said hinging region having a tension surface portion capable of experiencing an elongation range of at least 3% during said deflection, said tension surface portion being made with an elastic material capable of permitting said tension surface to experience an elastic recovery from said elongation range at the end of a kicking stroke, said elastic recovery being sufficient to snap said pivoting blade portion back from said deflected position toward said neutral position at the end of a kicking stroke; and (d) providing said active portion with sufficient transverse flexibility to bow between said outer side edges from an unbowed position at rest to a bowed position during use to form a bowed three quarter position concave scooped channel along said attacking surface at said three quarter position, said bowed three quarter position concave scooped channel having a predetermined three quarter position depth of scoop between said unbowed position and said bowed position that is at least 5% of said predetermined transverse dimension at said three quarter position, said active portion having sufficient longitudinal flexibility along said predetermined longitudinal dimension to permit said active portion to form a substantially S-shaped wave alone said predetermined longitudinal dimension during an inversion phase of a reciprocating kick stroke cycle.