Methods for creating large scale focused blade deflections

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.

1 . An improved swim fin comprising: 
 (a) a foot attachment portion;    (b) a blade member secured to said foot attachment portion and forming a substantially forward extension of said foot attachment portion, said blade member having a blade root portion adjacent said foot attachment portion and a blade free end portion remote from said blade root portion, said blade member having opposing surfaces and outer side edges;    (c) at least one substantially flexible elongated load bearing rib member secured to said blade member, said rib member having a rib root portion adjacent said foot attachment portion and a rib free end portion remote from said rib root portion and said foot attachment portion, said rib having a predetermined length between said rib root portion and said rib free end portion, said rib having a longitudinal midpoint, said rib member having a first half portion located between said root portion and said midpoint, said rib having a second half portion located substantially between said midpoint and said rib free end, said rib having a flexible rib region adjacent said rib root portion and within said first half portion, said flexible rib region being made with an extensible load bearing material, said extensible load bearing material is arranged to provide a major portion of the structural support of said blade member relative to said foot portion as relatively light load conditions are exerted on said blade member such as created during a light kicking stroke used by a swimmer to achieve a relatively slow to moderate swimming speed;    (d) said flexible rib region having predetermined amount of flexibility arranged to allow a predetermined light kick deflection angle of at least 10 degrees, said flexible rib region taking on a corresponding light kick bending radius;    (e) said flexible rib region having a sufficiently tall vertical rib dimension relative to said light kick bending radius to permit a tension surface portion of said extensible load bearing material to experience a predetermined light kick elongation range that is at least 3% during said light kick deflection, and said vertical dimension is sufficient to permit a compression surface portion of said load bearing material to experience a predetermined light kick compression range that is at least 1% during said light kick deflection;    (f) said flexibility of said flexible rib region is arranged to permit a significantly large amount of said light kick deflection to occur within said first half portion of said rib;    (g) said flexible rib region having a sufficiently large enough cross section to substantially prevent said flexible rib region from buckling excessively during said light kick deflection; and    (h) said extensible load bearing material is sufficiently extensible and compressible to permit said flexible rib region to experience said light kick elongation range and said light kick compression range under said light load conditions.    
   
   
       2 . The swim fin of  claim 1  wherein said flexible rib region is a region of reduced cross section.  
   
   
       3 . The swim fin of  claim 1  wherein said flexible rib region is a region of reduced transverse dimension.  
   
   
       4 . The swim fin of  claim 1  wherein said flexible rib region is a region of reduced vertical thickness.  
   
   
       5 . The swim fin of  claim 1  wherein said deflection is not less than 15 degrees.  
   
   
       6 . The swim fin of  claim 1  wherein said deflection is not less than 20 degrees.  
   
   
       7 . The swim fin of  claim 1  wherein said deflection is not less than 30 degrees.  
   
   
       8 . The swim fin of  claim 1  wherein said deflection is not less than 20 degrees and not substantially greater than 50 degrees.  
   
   
       9 . The swim fin of  claim 1  wherein said deflection is not less than 30 degrees and not substantially greater than 50 degrees.  
   
   
       10 . The swim fin of  claim 1  wherein said elongation range is not less than 7%.  
   
   
       11 . The swim fin of  claim 1  wherein said elongation range is not less than 10%.  
   
   
       12 . The swim fin of  claim 1  wherein said elongation range is not less than 15%.  
   
   
       13 . The swim fin of  claim 1  wherein said elongation range is not less than 20%.  
   
   
       14 . The swim fin of  claim 1  wherein said elongation range is not less than 30%.  
   
   
       15 . The swim fin of  claim 1  wherein said compression range is not less than 2%.  
   
   
       16 . The swim fin of  claim 1  wherein said compression range is not less than 5%.  
   
   
       17 . The swim fin of  claim 1  wherein said compression range is not less than 7%.  
   
   
       18 . The swim fin of  claim 1  wherein said compression range is not less than 10%.  
   
   
       19 . The swim fin of  claim 1  wherein said flexible rib region is formed by at least one notch-like cutout within said rib.  
   
   
       20 . The swim fin of  claim 1  wherein said flexible rib region is formed by a tension surface cutout along said tension surface and a compression surface cutout along said compression surface.