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. This predetermined compression range is significantly used up during the deflection to the predetermined angle of attack in an amount effective to create a sufficiently large leeward shift in the neutral bending surface with the load bearing portions of the hydrofoil ( 164 ) to permit the hydrofoil ( 164 ) to experience a significantly large increase in bending resistance as increased loads deflect the hydrofoil ( 164 ) beyond the predetermined reduced angle of attack. The shift in the neutral bending surface causes a significant increase in the elongation range required along an attacking portion of the hydrofoil ( 164 ) after the predetermined angle of attack is exceed. Methods are also disclosed for designing the hydrofoil ( 164 ) so that it has a natural resonant frequency that is sufficiently close the frequency of the reciprocating strokes used to attain propulsion in an amount sufficient to create harmonic wave addition that creates an amplified oscillation in the free end of the reciprocating hydrofoil ( 164 ). Methods are also disclosed for focusing energy storage and blade deflections along focused regions of load bearing members and the hydrofoil ( 164 ). Methods are also disclosed for reducing induced drag vortex formation along the lee surface of the hydrofoil ( 164 ), reducing drag and increasing the formation of lift forces.

1 . A method for providing an improved hydrofoil comprising:
 (a) providing a predetermined body that is arranged to experience reciprocating motion;   (b) connecting a blade member to said predetermined body to form an extension of said predetermined body wherein said blade member is subjected to said reciprocating motion, said blade member having a blade root portion adjacent said predetermined body and a blade free end portion remote from said blade root portion and said predetermined body, said blade member having opposing surfaces and outer side edges;   (c) providing at least one substantially flexible elongated load bearing rib member molded 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 between said longitudinal midpoint and said rib root portion, said rib member having a second half portion between said midpoint and said rib free end portion;   (d) providing said rib member with an first elongated portion being made with a first thermoplastic material during an early phase of an injection molding process and a second elongated portion made with a second thermoplastic material, both said first elongated portion and said second elongated portion being at least half of said predetermined length, at least one portion of said first elongated portion being vertically thicker than at least one portion of said blade member, said first elongated portion being connected to said second elongated portion; and   (d) providing said first half of said rib member and said second half of said blade member with sufficient flexibility to permit said rib member to form at least one longitudinal sinusoidal wave having at least two opposing directions of curvature along said predetermined length during at least one phase of said reciprocating motion.   
   
   
       2 . The method of  claim 1  wherein said first elongated portion is an elongated core disposed within said rib member. 
   
   
       3 . The method of  claim 1  wherein said second elongated portion has a Shore A hardness that is less than 70 durometer. 
   
   
       4 . The method of  claim 1  wherein said rib root portion has a region of reduced cross section. 
   
   
       5 . The method of  claim 1  wherein said first elongated portion is made during an earlier step of an injection molding process and said second elongated portion is made during a later step of an injection molding process, and said second elongated portion is arranged to be more extensible than said first elongated portion. 
   
   
       6 . The method of  claim 1  wherein said first elongated portion is made during an earlier step of an injection molding process and said second elongated portion is made during a later step of an injection molding process, and said first elongated portion is arranged to be relatively harder than said second elongated portion. 
   
   
       7 . The method of  claim 1  wherein said first elongated portion extends along a majority of said predetermined length of said rib member. 
   
   
       8 . The method of  claim 1  wherein said first half portion of said rib member is arranged to pivot to a lengthwise reduced angle of attack sufficient to significantly reduce the resistance of said blade member to surrounding fluid medium during said reciprocating motion. 
   
   
       9 . The method of  claim 1  wherein sinusoidal wave is sufficient to increase the propulsion of said hydrofoil. 
   
   
       10 . The method of  claim 1  wherein said first elongated portion has lateral sides and said second elongated portion extends around a significant portion of said lateral sides. 
   
   
       11 . The method of  claim 1  wherein at least one portion of said rib member has a Shore A hardness that is substantially between 80 and 98 durometer. 
   
   
       12 . The method of  claim 1  wherein at least one portion of said rib member has a Shore D hardness that is substantially between 45 and 75 durometer. 
   
   
       13 . The method of  claim 1  wherein rib member is arranged to have a Shore D hardness substantially between 45 and 75 durometer. 
   
   
       14 . A method for providing a hydrofoil comprising:
 (a) providing a blade member secured to a predetermined body, said blade member having a blade root portion near said predetermined body and a blade free end portion spaced from said blade root portion and said predetermined body, said blade member having opposing surfaces and outer side edges;   (b) providing at least one substantially flexible elongated rib member molded to said blade member, said at least one substantially flexible elongated rib member having a rib root portion adjacent said blade root portion and a rib free end portion remote from said rib root portion and said predetermined body, said at least one substantially flexible elongated rib member having a predetermined length between said rib root portion and said rib free end portion, said rib member having a flexible load bearing portion that is arranged to provide a majority of the structural support for said rib member, said flexible load bearing portion having a Shore A hardness that is not greater than 98 durometer;   (c) providing said rib root portion with a substantially ovular cross sectional shape having a predetermined vertical cross section dimension and a predetermined horizontal cross section dimension, said predetermined vertical cross section being greater than said predetermined horizontal cross section, said predetermined horizontal cross section dimension being sufficient to significantly; and   (d) providing said rib free end portion with a substantially rounded cross sectional shape that is less ovular than said rib root portion.   
   
   
       15 . The method of  claim 14  wherein said rib member is arranged to pivot around a transverse axis near said rib root portion to a significantly reduced lengthwise angle of attack during use. 
   
   
       16 . The method of  claim 14  wherein said rib member is arranged to be sufficiently flexible to form a longitudinal sinusoidal wave along said predetermined length during at least one phase of a reciprocating stroke cycle, wherein said sinusoidal wave has at least two opposing directions of curvature 
   
   
       17 . The method of  claim 14  wherein at least one portion of rib member near said rib root portion has a region of reduced cross sectional volume. 
   
   
       18 . A method for providing a hydrofoil comprising:
 (a) providing a blade member secured to a predetermined body, said blade member having a blade root portion near said predetermined body and a blade free end portion spaced from said blade root portion and said predetermined body, said blade member having a predetermined length between said blade root portion and said blade free end portion, said blade member having opposing surfaces and outer side edges, said blade member being made with a relatively hard thermoplastic material;   (b) providing at least one substantially flexible elongated rib member made with an extensible thermoplastic material molded to at least one of said opposing surfaces of said blade member with a weld bond, said at least one substantially flexible elongated rib member having a rib root portion adjacent said blade root portion and a rib free end portion remote from said rib root portion and said predetermined body;   (c) providing said rib member with sufficient flexibility near said rib root portion to permit said blade member to experience the formation a longitudinal sinusoidal wave along said predetermined length during at least one phase of a predetermined reciprocating propulsion stroke cycle; and   (d) providing said rib member with a predetermined transverse dimension that is arranged to be sufficiently large enough to substantially prevent said rib member from twisting excessively around a substantially lengthwise axis during said formation of said sinusoidal wave.   
   
   
       19 . The method of  claim 18  wherein said rib member is made with at least two different materials both of which extend a predetermined distance from at least one of said opposing surfaces of said blade member. 
   
   
       20 . The method of  claim 18  wherein said rib root portion has a region of increased flexibility sufficient to cause said rib root portion to pivot to a lengthwise reduced angle of attack around a transverse axis near said predetermined body in an amount sufficient to significantly reduce the energy required to generate propulsion with said blade member.