Fin for surf craft

Abstract

A fin ( 410 ) with a discrete structural strand layer ( 420 ) that may include high tensile carbon fibre strands ( 422, 424 ) and high tensile strength and toughness Kevlar ( 426 ) strands. These structural strands may have a tensile strength substantially greater than the other materials typically used in a fin body. The structural strand layer ( 420 ) provides an economic and ready technique to vary and control a stiffness characteristic of the fin in a variety of directions or about a variety of axes of rotation; without varying the other common components that may be used in a fin body, for example core ( 412 ), layers of fibreglass fabric ( 414 ) and/or resin.

1 . A fin for surf craft comprising:
 a fin body; and   at least one layer of structural strands, located within the fin body;   wherein the structural strands are in one or more non-woven arrangements; and   the structural strands have a physical property greater than a corresponding physical property of other material forming the fin body; and   wherein the physical property is selected from at least one of a toughness, a tensile strength, an elastic moduli and a Youngs modulus.   
     
     
         2 . A fin according to  claim 1 , wherein the fin comprises a base portion and a tip portion and at least a portion of the structural strands extends substantially from the base portion to the tip portion of the fin. 
     
     
         3 . A fin according to  claim 1 , wherein the fin comprises a base portion and a leading edge portion and at least a portion of the structural strands extends substantially from the base portion to the leading edge portion of the fin. 
     
     
         4 . A fin according to  claim 1 , wherein the fin comprises a leading edge portion and a trailing edge portion and at least a portion of the structural strands extends substantially from the leading edge portion to the trailing edge portion of the fin. 
     
     
         5 . A fin according to  claim 1 , wherein the fin comprises opposing faces and at least one layer of structural strands in one or more arrangements is located within the fin body such that the at least one layer of structural strands is substantially parallel to the opposing faces of the fin. 
     
     
         6 . A fin according to  claim 1 , wherein the structural strands of at least one layer are substantially parallel to each other. 
     
     
         7 . A fin according to  claim 6 , wherein the fin comprises a sweep angle and, in a first arrangement, the substantially parallel structural strands are generally parallel to the sweep angle of the fin. 
     
     
         8 . A fin according to  claim 6 , wherein the fin comprises a sweep angle and, in a first arrangement, the substantially parallel structural strands are at a first angle to the sweep angle of the fin, the first angle being in the range of up to 20 degrees. 
     
     
         9 . A fin according to  claim 8 , the first angle is approximately 10 degrees. 
     
     
         10 . A fin according to  claim 6 , wherein, in a second arrangement the substantially parallel structural strands are at a second angle to the vertical of the fin, the second angle being in the range of 20 to 40 degrees. 
     
     
         11 . A fin according to  claim 6 , wherein the fin comprises a vertical component and, in a second arrangement, the substantially parallel structural strands are at an angle of approximately 30 degrees to the vertical of the fin. 
     
     
         12 . A fin according to  claim 6 , wherein, in a third arrangement, the substantially parallel structural strands are generally vertical. 
     
     
         13 . A fin according to  claim 6 , wherein the fin comprises a sweep angle and, in a primary arrangement, the substantially parallel structural strands are generally perpendicular to a sweep angle of the fin. 
     
     
         14 . A fin according to  claim 13 , wherein, in a secondary arrangement, the substantially parallel structural strands are at a first angle to a sweep angle of the fin, the first angle being in the range of 20 to 40 degrees. 
     
     
         15 . A fin according to  claim 13 , wherein, in a secondary arrangement, the substantially parallel structural strands are at a first angle of approximately 30 degrees to a sweep angle of the fin. 
     
     
         16 . A fin according to  claim 13 , wherein, in a tertiary arrangement, the substantially parallel structural strands are generally vertical. 
     
     
         17 . A fin according to  claim 1 , wherein at least one layer of structural strands comprises of a plurality of structural strands extending from at least one substantially common point in a substantially radial formation. 
     
     
         18 . A fin according to  claim 17 , wherein the fin comprises a base portion and the at least one substantially common point is adjacent the base portion of the fin. 
     
     
         19 . A fin according to  claim 17 , wherein the fin comprises a leading edge portion and a trailing edge portion and the at least substantially common point is adjacent at least one of a leading edge portion and a trailing edge portion of the fin. 
     
     
         20 . A fin according to  claim 1 , wherein at least one structural strand comprises of a plurality of filaments. 
     
     
         21 . A fin according to  claim 1 , wherein at least one structural strand is made of at least one of carbon fibre, Kevlar, aramide, natural fibres and synthetic fibres. 
     
     
         22 . A fin according to  claim 1 , wherein at least one structural strand has a tensile strength that is at least 1.5 times greater than the tensile strength of the other material forming the fin body. 
     
     
         23 . A fin according to  claim 1 , wherein at least one structural strand has a Youngs modulus that is at least 1.5 times greater than a Youngs modulus of the other material forming the fin body. 
     
     
         24 . A fin according to  claim 1 , wherein at least one structural strand has a toughness that is greater than a toughness of the other material forming the fin body. 
     
     
         25 . A fin according to  claim 1 , wherein at least a portion of the structural strands comprises unidirectional filaments in a ribbon configuration. 
     
     
         26 . A fin according to  claim 1 , wherein at least a portion of the structural strands have a width in the range of 0.5 to 3 mm. 
     
     
         27 . A fin according to  claim 1 , wherein at least a portion of the structural strands has a width in the range of 1 2 mm. 
     
     
         28 . A fin according to  claim 1 , wherein at least a portion of the structural strands comprises of at least about 3,000 filaments per structural strand. 
     
     
         29 . A fin according to  claim 1 , wherein the fin comprises a base portion and a tip portion and a spacing between at least a portion of the structural strands is less towards the base portion compared with the tip portion of the fin. 
     
     
         30 . A fin according to  claim 1 , wherein a spacing between at least a portion of the structural strands is in the range of 1 to 30 times a width of one structural strand. 
     
     
         31 . A fin according to  claim 30 , wherein a spacing between at lest a portion of the structural strands is in the range of 4 to 13 times a width of one structural strand. 
     
     
         32 . A fin according to  claim 1 , wherein a spacing between at least a portion of the structural strands is in the range of 4 to 15 mm. 
     
     
         33 . A fin according to  claim 32 , wherein a spacing between at least a portion of the structural strands is in the range of 9 to 13 mm. 
     
     
         34 . A fin for surf craft comprising:
 a fin body; and   at least one layer of structural strands, located within the fin body;   wherein the structural strands are in one or more woven arrangements that are at least one of an open weave and a scrim;   wherein the structural strands have a physical property greater than a corresponding physical property of other material forming the fin body; and   wherein the physical property is selected from at least one of a toughness, a tensile strength, an elastic moduli and a Youngs modulus.   
     
     
         35 . A fin according to  claim 34 , further including a core structure located within the fin body. 
     
     
         36 . A fin according to  claim 35 , wherein at least one layer of structural strands in one or more arrangements is embedded within a body of the fin such that the layer of structural strands is substantially parallel to a face of the core structure. 
     
     
         37 . A fin according to  claim 35 , wherein the fin comprises opposing faces and the at least one layer of structural strands are located intermediate the core structure and at least one of the opposing faces of the fin. 
     
     
         38 . A fin according to  claim 35 , wherein the core is at least one of a foam core structure and a solid, non-foam core structure. 
     
     
         39 . A fin according to  claim 35 , wherein at least a portion of the core structure is made of at least one of PVC foam, polyurethane foam, resin impregnated fibreglass, hardened resin, polyester mat, microspheres, plastic, bamboo and wood. 
     
     
         40 . A fin according to  claim 34 , wherein the fin body comprises a base portion and further includes at least one layer of unidirectional carbon fibre fabric towards the base portion of the fin body. 
     
     
         41 . A fin according to  claim 40 , wherein the at least one layer of carbon fibre fabric is located about a periphery of the fin body. 
     
     
         42 . A fin according to  claim 34 , having a sweep angle of from 20 to 60 degrees. 
     
     
         43 . A method of controlling a fin physical property for a surf craft, the method comprising:
 selecting one or more structural strands having a structural strand physical property greater than a corresponding physical property of other materials in a body of the fin;   selecting a number of structural strands to provide the fin physical property;   providing a layer of the structural strands in one or more arrangements; and   embedding the layer of structural strands in the body of the fin;   whereby varying at least one of the structural strands selection, the number of structural strands or the arrangement of the structural strands varies the fin physical property; and   wherein the fin physical property is selected from at least one of: a stiffness characteristic, a bending resistance, a twisting resistance, a resistance to a deflection, a flexibility and a high elastic recoil; and   wherein the structural strand physical property is selected from at least one of: a toughness, a tensile strength, an elastic moduli and a Youngs modulus.   
     
     
         44 . A method according to  claim 43 , wherein the step of providing a layer of structural strands includes the use of a template to locate one or more structural strands of one or more arrangements. 
     
     
         45 . A method according to  claim 44 , wherein the step of using a locating template further includes providing at least one of pins, adherents and securing systems to locate one or more structural strands. 
     
     
         46 . A method according to  claim 44 , wherein the step of using a locating template further includes the steps of:
 providing one or more reliefs machined into the template, and   laying individual structural strands into respective reliefs to form a three dimensional structural strand layer.   
     
     
         47 . A method according to  claim 44 , wherein the step of providing a layer of structural strands includes the use of a numerically or a computer controlled machine to locate one or more structural strands of one or more arrangements. 
     
     
         48 . A method according to  claim 43 , wherein the step of providing a layer of structural strands further includes a step of:
 configuring the arrangement of structural strands in a layer to vary the fin physical property.   
     
     
         49 . A method according to  claim 43 , further including providing one or more structural strands largely parallel to a sweep angle of the fin such that the fin is provided with an increased resistance to a twisting of the fin. 
     
     
         50 . A method according to  claim 43 , further including providing one or more structural strands at a first angle of up to 20 degrees to a sweep angle of the fin to provide the fin with an increased resistance to a twisting of the fin. 
     
     
         51 . A method according to  claim 43 , further including providing one or more structural strands at a second angle in the range of 20 to 40 degrees to the vertical axis of the fin such that the fin is provided with an increased resistance to a deflection from the vertical axis 
     
     
         52 . A fin for surf craft produced according to the method of  claim 43 . 
     
     
         53 . (canceled) 
     
     
         54 . (canceled)