Fin

Abstract

To provide a fin which has excellent steering properties in addition to the straightness of a board.SOLUTION: Disclosed is a fin 1C fitted to the side of a rear face 2a of a board 2. A core material 11 having high strength is arranged at the fin 1C so as to be biased toward the board 2.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a fin that is attached to a surfboard or the like. [Background technology]

[0002] Fins that act as rudders are attached to the underside of surfboards and other equipment to stabilize the straightness and maneuverability of the surfboard. The overall shape of such fins and their ease of bending affect the straightness and maneuverability of the surfboard. In particular, the ease of bending of a fin is largely dependent on the hardness of the material that makes up the fin, and it is known that hard fins that are difficult to bend improve straightness by making it difficult for them to hold water, while soft fins that are easy to bend improve maneuverability by making it easier to hold water.

[0003] The fin of Patent Document 1 is made by laminating a thick core mat or the like having substantially the same shape as the fin between a pair of dies corresponding to the shape of the fin, applying polyester resin, and then laminating a glass cloth or the like made of woven glass fibers on the outside of that, applying polyester resin, and hardening it under pressure. By laminating a thick core mat or the like inside the fin, the fin like that of Patent Document 1 not only simplifies the manufacturing process compared to conventional fins manufactured by laminating 20 to 30 layers of glass cloth, but also makes it possible to achieve a lighter fin while maintaining substantially the same thickness as conventional fins. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP-A-62-246383 (pages 2 to 3, Figure 1) Summary of the Invention [Problem to be solved by the invention]

[0005] However, in fins such as those described in Patent Document 1, a core mat or the like, which has approximately the same shape as the fin, extends to the tip of the fin, which is called the tip, and these are covered from the outside with glass cloth and hardened with polyester resin. Therefore, while the fin has excellent straight-line performance, the entire fin is hard and difficult to bend, making it difficult to hold water, resulting in poor maneuverability.

[0006] The present invention has been made in response to these problems, and has as its object to provide a fin that not only improves the straightness of the board, but also provides excellent maneuverability. [Means for solving the problem]

[0007] In order to solve the above problems, the fin of the present invention comprises: A fin attached to the underside of the board, The fin is characterized in that a core material having high strength is arranged biased toward the board side. According to this feature, the board side of the fin is less likely to bend due to fluid resistance when changing the direction of the board, while the tip of the fin is more likely to bend, providing a fin that not only provides the board with straight-line stability but also has excellent maneuverability.

[0008] The core material is characterized in that it is disposed along the outer shape of the fin. This feature makes it possible to create a strength distribution that does not impede the original function of the fin.

[0009] The core material is characterized in that it extends to the legs of the fins attached to the back side of the board. According to this feature, the legs can be reinforced by the core material.

[0010] The tip of the core material is located closer to the board than the apex of the rear edge portion of the fin. This feature makes it easier for the fin to bend towards the tip, improving the maneuverability of the board.

[0011] The rear end of the core material is located forward of the base point of the rear edge portion of the fin. This feature makes it easier for the fin to bend towards the rear end, improving the maneuverability of the board.

[0012] The core material is characterized in that it is a wire material. This feature allows the fin to be made lighter.

[0013] The core material is characterized in that it is adhered to the substrate. According to this feature, the strength of the base material and the core material that make up the fin can be increased mutually. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a bottom view showing a surfboard in accordance with a first embodiment of the present invention. [Diagram 2] FIG. 2 is a rear view of the surfboard seen from the tail side. [Diagram 3] FIG. 2 is a side view of a fin in the first embodiment. [Figure 4] 4 is a cross-sectional view taken along line AA in FIG. [Diagram 5] FIG. 2A is a front view showing the bending characteristics of the fin in the first embodiment, and FIG. 2B is a front view showing the bending characteristics of a conventional fin. [Figure 6] FIG. 11 is a side view of a fin in the second embodiment. [Figure 7] FIG. 7 is a cross-sectional view of FIG. 6 taken along line B-B. [Figure 8] FIG. 11 is a side view of a fin in the third embodiment. [Figure 9] FIG. 13 is a side view of a fin in the fourth embodiment. [Figure 10] 13A to 13C are diagrams illustrating a manufacturing method of a fin in the fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fin according to an embodiment of the present invention will be described below with reference to the accompanying drawings. EXAMPLES

[0016] A fin according to a first embodiment will be described with reference to Figures 1 to 5. In the following description, the upper side of Figure 1 is the front side (forward side) of the board, the right side of Figure 1 showing the back side of the board is the left side of the board, and the left side of Figure 1 is the right side of the board. The front end side of the board is sometimes called the nose side, and the rear end side is sometimes called the tail side.

[0017] The fin of the present invention is attached to the underside of the board. In this embodiment, the fin is attached to a surfboard 2 as a board, but the fin may be attached to other boards such as a bodyboard or a wakeboard.

[0018] As shown in Figures 1 and 2, the tail side of the underside 2a of the surfboard 2 of this embodiment is provided with a center fin 1C located in the center in the left-right direction, and a pair of side fins 1L, 1R positioned on either side of the center fin 1C.

[0019] The center fin 1C is disposed at the left-right center of the surfboard 2 so as to be approximately perpendicular to the underside 2a. The side fins 1L, 1R are disposed shifted forward from the center fin 1C. More specifically, the side fins 1L, 1R are inclined so as to move away from each other in the left-right direction toward the bottom end, and are also inclined so as to move away from each other in the left-right direction from the front end to the rear end. Note that, in the surfboard 2 of this embodiment, a form in which three fins 1L, 1C, 1R are provided has been described, but this is not limiting, and the number and arrangement of the fins may be freely changed.

[0020] Next, the structure of the center fin 1C will be described. The side fins 1L and 1R have substantially the same structure as the center fin 1C, except that the side fins 1L and 1R are so-called flat foils in which the surfaces facing inward in the left-right direction are flat and the surfaces facing outward in the left-right direction are convexly curved (see FIG. 2). Therefore, the description thereof will be omitted.

[0021] As shown in Fig. 3, the center fin 1C (hereinafter sometimes referred to as the fin) of this Example 1 is composed of a base material 10 that forms the outer shape of the fin, and a core material 11 that is biased toward the surfboard 2 side, i.e., the upper side, inside the base material 10. The fin in this Example is thick on the front and upper sides and gradually becomes thinner toward the rear and lower sides, and has a streamlined cross-sectional shape (see Fig. 4).

[0022] In this embodiment, the base material 10 is made of polycarbonate as a main material, and has elasticity due to the addition of an appropriate amount of glass powder. In addition, the base material 10 is translucent and lightweight due to being made of polycarbonate as a main material. The base material 10 of this embodiment has an overall outer shape that gradually extends rearward from its upper base end side to its lower tip end side. In particular, the rear edge portion 10a forming the rear outer edge of the base material 10 has an outer shape that gradually curves and extends rearward from the base point P1 at its upper end to the apex P2 (the rearmost point) at the tip.

[0023] In addition, as long as the base material has the elasticity required for the fin, it may be primarily made of other synthetic resins such as polyester resin or silicone resin, or rubber, in addition to polycarbonate, and fillers and various additives may be added.

[0024] In this embodiment, two legs 12, 12 are integrally formed on the base 10, one in front and one in back, which protrude upward from a base 10b that extends substantially horizontally and constitutes the upper end of the fin. The fin in this embodiment is attached to the underside 2a of the surfboard 2 by inserting the legs 12, 12 into a fin box 3 provided on the underside 2a of the surfboard 2 and fixing them with bolts 4 (see FIG. 1). The shape of the legs is not limited to that in this embodiment, and for example, a single leg extending in the fore-aft direction of the base may be integrally formed.

[0025] In this Example 1, the core material 11 is a single wire made of stainless steel with a circular cross section (see FIG. 4), which is bent into a curved U-shape along the outer shape of the substrate 10 as described below. The core material 11 is a wire having the same diameter over its entire length. The core material 11 is made of a different material from the substrate 10 and has a higher strength than the substrate 10. More specifically, the core material 11 is a member having a larger Young's modulus than the substrate 10, in other words, the core material 11 is a member that is harder and less likely to bend than the substrate 10.

[0026] In addition, the core material may be made of other metals, such as aluminum or titanium, synthetic resin, wood, bamboo, etc., other than stainless steel, so long as it has a higher strength than the substrate. The core material may be made of the same material as the substrate, or may be made of the same material as the substrate to which a filler, such as glass fiber or carbon fiber, has been added to increase its strength.

[0027] The cross-sectional shape of the wire used as the core material is not limited to a circular shape, and may be other shapes such as an ellipse, a polygon, a T-shape, or an H-shape. The cross-sectional shape or cross-sectional area of ​​the wire used as the core material may be partially changed depending on the desired bending characteristics of the fin. The wire used as the core material may have a hollow structure.

[0028] Moreover, the core material 11 is disposed inside the base material 10 along the outer shape of the fin. More specifically, the core material 11 is bent along the outer shape of the fin, with the rear end 11a being located forward of the base point P1 of the rear edge portion 10a of the fin. In other words, the core material 11 is bent so as to be located forward of an imaginary line α that passes through the base point P1 and extends perpendicular to the base 10b of the fin. The rear end 11a of the core material 11 is the portion located at the rearmost end of the entire core material 11.

[0029] Furthermore, the tip 11b (lower end) of the core material 11 is located above the apex P2 of the rear edge portion 10a of the fin. In other words, the core material 11 is bent so that the tip 11b is located above an imaginary line β that passes through the apex P2 and extends parallel to the base 10b of the fin. The tip 11b of the core material 11 is the portion located at the most distal end (lowest end) of the entire core material 11.

[0030] Moreover, both upper end portions 11c, 11d of the core material 11 extend into the two front and rear leg portions 12, 12. In particular, the end face of the front upper end portion 11c is exposed on the upper surface 12a of the leg portion 12. The exposed portion of the core material 11 may be covered with the material of the base material 10, a caulking material, or the like.

[0031] 4, the core material 11 is disposed approximately in the center in the thickness direction (left-right direction) of the fin. The base material 10 is welded to the core material 11. That is, the core material 11 is embedded with its outer surface bonded integrally to the base material 10.

[0032] Here, a manufacturing method of the center fin 1C will be described. In this embodiment 1, the center fin 1C is manufactured by so-called insert molding, in which the core material 11 is fixed and arranged in advance at approximately the center in the thickness direction (left and right direction) of a mold corresponding to the shape of the fin, and the material of the base material 10 that has been heated and melted is poured into the mold and cooled and solidified. In this way, the base material 10 is welded to the core material 11.

[0033] As described above, the core material 11 having high strength is arranged on the fin, biased toward the surfboard 2 side (upper side). As a result, as shown in FIG. 5(a), the bending characteristics of the fin of this embodiment are such that the upper side of the fin is less likely to bend and the tip portion of the fin, called the tip, is more likely to bend than the bending characteristics of the fin of this embodiment composed only of the base material (see FIG. 5(b)). In detail, the fin of this embodiment is easier to accelerate the surfboard 2 because the upper side of the fin is less likely to bend due to the fluid resistance when changing the traveling direction of the surfboard 2. Also, even when the speed of the surfboard 2 is high, only the tip portion of the fin is more likely to bend due to the fluid resistance when changing the traveling direction of the surfboard 2, so the fin is more likely to hold water, and the tip portion of the fin is more likely to return from a bent state to a straight state due to the restoring force based on the elasticity of the core material 11, and the fin is more likely to release water, so a high-performance fin excellent in both straightness and maneuverability of the surfboard 2 can be provided.

[0034] Furthermore, since the core material 11 makes it easy to ensure strength on the surfboard 2 side (upper side) of the fin, the thickness of the fin can be reduced.

[0035] Furthermore, since the core material 11 is arranged along the outer shape of the fin, it is possible to create a strength distribution that does not impede the original function of the fin.

[0036] Furthermore, since the core material 11 extends to the inside of the legs 12, 12 of the fin attached to the underside 2a of the surfboard 2, the legs 12, 12 can be reinforced by the core material 11.

[0037] In addition, because the rear end 11a of the core material 11 is located forward of the base point P1 of the rear edge portion 10a of the fin, the fin bends more easily toward the rear end, improving the maneuverability of the surfboard 2. In addition, because the tip 11b of the core material 11 is located above the apex P2 of the rear edge portion 10a of the fin, the fin bends more easily toward the tip end, improving the maneuverability of the surfboard 2.

[0038] Moreover, since the core material 11 is a wire material, the fin can be made lighter while still exhibiting high strength.

[0039] In addition, since the base material 10 is welded to the outer surface of the core material 11 and bonded thereto, the strength of the base material 10 and the core material 11 that constitute the fin can be mutually increased. Furthermore, since the core material 11 is less likely to come into direct contact with water, corrosion of the core material 11 can be prevented. Furthermore, since no gap is formed between the core material 11 and the base material 10, it is possible to suppress the intrusion of water into the inside of the fin or the increase in the weight of the fin due to moisture absorption by the base material 10 or the core material 11.

[0040] In addition, since the base material 10 is made semi-transparent by using polycarbonate as the main material, the core material 11 arranged inside the base material 10 can be confirmed from the outside, and abnormalities such as misalignment and breakage can be discovered early. Also, by making the core material 11 arranged inside the base material 10 visible from the outside, the design can be improved. In this way, it is preferable that the base material has translucency.

[0041] Moreover, since the fins of the first embodiment are manufactured by insert molding, the manufacturing process can be simplified.

[0042] Needless to say, the bending characteristics of the fin in this embodiment 1 can be adjusted by changing the bending shape of the wire material constituting the core material. In order to achieve the above-mentioned bending characteristics of the fin that can achieve both the straightness and maneuverability of the surfboard 2, it is preferable that the rear end of the core material is bent forward of the base point P1 of the rear edge portion 10a of the fin and the tip (lower end) of the core material is positioned above the apex P2 of the rear edge portion 10a of the fin. In other words, by not disposing the core material behind the imaginary line α and below the imaginary line β, the elasticity of the core material is increased at the base end side of the fin and the inherent flexibility of the base material 10 is ensured at the tip side of the fin, that is, the bending characteristics of the fin that can achieve both the straightness and maneuverability of the surfboard 2 are easily achieved.

[0043] Furthermore, the base material is not limited to being composed of a single layer, and may be composed of, for example, a plurality of layers made of different materials laminated together.

[0044] Moreover, both upper ends of the core material do not have to extend to the inside of the legs 12, 12. In this case, from the viewpoint of exerting the bending characteristics of the fin that can achieve both strength of the fin and straightness and maneuverability, it is preferable that the upper end of the core material extends to the vicinity of the base 10b.

[0045] The core material may be composed of a plurality of wires separated in the extending direction, or may be composed of a plurality of wires arranged in parallel in the width direction. EXAMPLES

[0046] Next, a fin according to Example 2 will be described with reference to Figures 6 and 7. In Example 2, a side fin 1L formed on a flat foil will be described as an example, and a description of the same configuration as in the previous example will be omitted.

[0047] As shown in FIG. 6, the side fin 1L of this Example 2 (hereinafter sometimes referred to as the fin) is composed of a base material 10 which forms the outer shape of the fin, and core materials 211A, 211B which are positioned inside the base material 10 and biased toward the surfboard 2, i.e., the upward side.

[0048] In this Example 2, the core materials 211A and 211B are two wire materials made of stainless steel and have a circular cross section (see FIG. 7). The core materials 211A and 211B are wire materials of the same diameter, and the core material 211A arranged on the front side is longer than the core material 211B arranged on the rear side.

[0049] The core members 211A and 211B may be made of wires that differ not only in length but also in thickness, material, and the like.

[0050] Moreover, core materials 211A and 211B are disposed along the outer shape of the fin inside substrate 10. In particular, core material 211A is curved along the shape of the front side of the fin, and core material 211B is curved along the shape of the rear side of the fin.

[0051] Furthermore, of the core materials 211A and 211B, the rear end 211Ba of the core material 211B that extends to the rear side is located forward of the base point P1 of the rear edge portion 10a of the fin. In other words, the core materials 211A and 211B extend to a position forward of the imaginary line α that passes through the base point P1 and extends perpendicular to the base 10b of the fin. The rear end 211Ba of the core material 211B is the part located at the rearmost end of the entire core material 211B.

[0052] Furthermore, of the core materials 211A and 211B, the tip 211Ab (lower end) of the core material 211A that extends to the tip side (lower side) is located above the apex P2 of the rear edge portion 10a of the fin. That is, the core materials 211A and 211B extend to a position above an imaginary line β that passes through the apex P2 and extends parallel to the base 10b of the fin. The tip 211Ab of the core material 211A is the portion located at the forefront (lowest end) of the entire core material 211A.

[0053] The cores 211A and 211B extend downward so as to gradually approach each other. The cores 211A and 211B are not limited to being formed with the same diameter over their entire length, and for example, the leading end 211Ab of the core 211A or the rear end 211Ba of the core 211B may be formed with a large diameter or may be formed in a tapered shape.

[0054] Additionally, upper ends 211Ac and 211Bc of the core materials 211A and 211B extend into the interiors of the two front and rear leg portions 12, 12, respectively. End faces of the ends 211Ac and 211Bc of the core materials 211A and 211B are exposed on the upper surface 12a of the leg portion 12. The exposed portions of the core materials 211A and 211B may be covered with the material of the base material 10, a caulking material, or the like.

[0055] 7, the core materials 211A and 211B are disposed approximately in the center in the thickness direction (left-right direction) of the fin. The outer surfaces of the core materials 211A and 211B are bonded to the base material 10 by the adhesive 210. That is, the core materials 211A and 211B are formed integrally with the base material 10 via the adhesive 210. For ease of explanation, FIG. 7 shows only the state of adhesion of the core material 211A to the base material 10 by the adhesive 210 in an enlarged portion, but the state of adhesion of the core material 211B to the base material 10 by the adhesive 210 is the same as that of the core material 211A.

[0056] Here, a method for manufacturing the side fin 1L will be described. In this Example 2, the side fin 1L is manufactured by first pouring the material of the base material 10, which has been heated and melted, into a mold corresponding to the shape of the fin, cooling and solidifying it, and then inserting the core materials 211A and 211B from the upper surfaces 12a of the legs 12 of the base material 10. In detail, the mold is configured so that when the base material 10 solidifies in the mold, insertion holes 10c for inserting the core materials 211A and 211B are formed in the upper surfaces 12a of the legs 12 and 12 in advance, respectively, and the core materials 211A and 211B are inserted in a state in which an appropriate amount of adhesive 210 is filled in the insertion holes 10c. As a result, the outer surfaces of the core materials 211A and 211B are bonded to the base material 10 by the adhesive 210 over the entire length in the insertion holes 10c.

[0057] The fins of the present embodiment 2 may be manufactured by insert molding, similar to the fins of the above-mentioned embodiment 1. In this case, the base material 10 is welded to the outer surfaces of the core members 211A and 211B.

[0058] According to this, by dividing the core materials 211A, 211B into two wires, it is easier to reduce the strength of the tip side of the core materials 211A, 211B compared to wires having a bent shape as in Example 1, making it possible to make the tip portion of the fin easier to bend.

[0059] Furthermore, of the core materials 211A, 211B, the rear end 211Ba of the core material 211B that extends to the rear side is located forward of the base point P1 of the rear edge portion 10a of the fin, so the fin is more easily bent toward the rear end, improving the maneuverability of the surfboard 2. Furthermore, of the core materials 211A, 211B, the tip 211Ab (lower end) of the core material 211A that extends to the tip side (lower side) is located above the apex P2 of the rear edge portion 10a of the fin, so the fin is more easily bent toward the tip side, improving the maneuverability of the surfboard 2.

[0060] In addition, since the outer surfaces of the core materials 211A and 211B are bonded to the base material 10 by the adhesive 210, the strength of the base material 10 and the core materials 211A and 211B that constitute the fin can be mutually increased. Furthermore, since the core materials 211A and 211B are less likely to come into direct contact with water, corrosion of the core materials 211A and 211B can be prevented. Furthermore, since no gap is formed between the core materials 211A and 211B and the insertion hole 10c in the base material 10, it is possible to suppress the intrusion of water into the inside of the fin or the increase in weight of the fin due to moisture absorption by the base material 10 and the core materials 211A and 211B.

[0061] Furthermore, the fin of the second embodiment is manufactured by subsequently inserting the core members 211A and 211B into the base material 10 formed by a die, and therefore the manufacturing process can be simplified.

[0062] The insertion holes 10c are not limited to those formed by a mold, but may be formed by boring holes in the molded base material 10 using a drill or the like.

[0063] Furthermore, the gaps between the core materials 211A, 211B and the insertion holes 10c do not have to be filled with adhesive. In this case, however, it is preferable that the gaps are small enough that the core materials 211A, 211B do not move relative to the base material 10.

[0064] Furthermore, it goes without saying that the bending characteristics of the fins in this embodiment 2 can be adjusted not only by changing the length, thickness, material, etc. of the wire that constitutes the core materials 211A and 211B, but also by changing the curvature and arrangement of the core materials 211A and 211B.

[0065] The core material may be made up of one wire or three or more wires. EXAMPLES

[0066] Next, a fin according to a third embodiment will be described with reference to Fig. 8. Note that a description of the same configuration as in the previous embodiment will be omitted.

[0067] As shown in Figure 8, the fin of this Example 3 is composed of a base material 10 that forms the outer shape of the fin, and a core material 311 that is positioned inside the base material 10 and biased toward the surfboard 2, i.e., the upward side.

[0068] In this Example 3, the core material 311 is a plate material made of stainless steel. The core material 311 is a flat plate material having a substantially uniform thickness.

[0069] In addition, the core material may be made of other metals, such as aluminum or titanium, synthetic resin, wood, bamboo, etc., other than stainless steel, so long as it has a higher strength than the base material. The core material may be made of the same material as the base material, or may be made of the same material as the base material to which a filler, such as glass fiber or carbon fiber, has been added to increase its strength.

[0070] The plate material used as the core material is not limited to one having a substantially uniform thickness, and may be made thin and easy to bend by, for example, pressing the tip side (lower end side).The plate material used as the core material may be provided with grooves, through holes, or the like so that the tip side is easy to bend.

[0071] Moreover, the core material 311 is disposed inside the base material 10 along the outer shape of the fin. More specifically, the core material 311 has an outer shape close to the outer shape of the fin, and its rear end 311a is located rearward of the base point P1 of the rear edge portion 10a of the fin. That is, the core material 311 extends to a position rearward of an imaginary line α that passes through the base point P1 and extends perpendicular to the base 10b of the fin. This allows the high rigidity of the core material 311 to be exerted up to the rear end side of the fin. The rear end 311a of the core material 311 is the part located at the rearmost end of the entire core material 311.

[0072] Furthermore, tip 311b (lower end) of core material 311 is located above apex P2 of rear edge portion 10a of the fin. That is, core material 311 extends to a position above imaginary line β that passes through apex P2 and extends parallel to fin base 10b. Tip 311b of core material 311 refers to the portion located at the most distal end (lowest end) of the entire core material 311.

[0073] According to this, by forming core material 311 from a plate material, strength can be ensured even if core material 311 is thin, and the thickness of the entire fin can be reduced.

[0074] Furthermore, since the core material 311 can be formed to have an outer shape close to that of the fin, it is possible to create a strength distribution that does not impede the original function of the fin.

[0075] The fin of this Example 3 can be manufactured by either the insert molding method as in Example 1, or the insert molding method in which a core material is inserted after molding the base material 10 as in Example 2.

[0076] Additionally, the core material 311 may have a protrusion extending into the inside of the legs 12,12.

[0077] Furthermore, the core material 311 may be divided into a plurality of pieces. For example, the plate material constituting the core material may be divided into a front side and a rear side. EXAMPLES

[0078] Next, a fin according to a fourth embodiment will be described with reference to Fig. 9. Note that a description of the same configuration as in the previous embodiment will be omitted.

[0079] As shown in Figure 9, the fin of this Example 4 is composed of a base material 10 which forms the outer shape of the fin, and core materials 411A, 411B which are positioned inside the base material 10 and biased towards the surfboard 2, i.e., the upward side.

[0080] In this fourth embodiment, core material 411A is a single wire material made of stainless steel, and core material 411B is a plate material made of stainless steel. Core material 411A is bent along a part of the outer periphery of core material 411B and is disposed so as to contact core material 411B. Core materials 411A and 411B may be separate bodies or may be integral.

[0081] The rear end 411Aa of the core material 411A is located forward of the base point P1 of the rear edge portion 10a of the fin. That is, the core material 411A is bent so as to be located forward of an imaginary line α that passes through the base point P1 and extends perpendicular to the base 10b of the fin. The rear end 411Aa of the core material 411A is the part located at the rearmost end of the entire core material 411A.

[0082] Moreover, the tip 411Ab (lower end) of the core material 411A is located above the apex P2 of the rear edge portion 10a of the fin. That is, the core materials 411A and 411B are bent so as to be located above an imaginary line β that passes through the apex P2 and extends parallel to the base 10b of the fin. The tip 411Ab of the core material 411A is the part located at the forefront (lowest end) of the entire core material 411A.

[0083] Moreover, both upper ends 411Ac, 411Ad of the core material 411A extend to the insides of the two front and rear leg portions 12, 12.

[0084] According to this, by combining core material 411A made of wire material and core material 411B made of plate material, core materials 411A and 411B can reinforce each other. EXAMPLES

[0085] Next, a fin according to a fifth embodiment will be described with reference to Fig. 10. Note that a description of the same configuration as in the previous embodiment will be omitted.

[0086] 10, the fin of this Example 5 is constructed by placing a core material 511, which is a stainless steel plate material, in the center of the fin's thickness direction, laminating four sheets of glass cloth 513 made of glass fiber on both sides of the core material 511, and hardening the laminate with polyester resin. The fin of this Example 5 is shaped by cutting out and polishing unnecessary portions of the base material solidified in a pair of molds.

[0087] The core material 511 in this embodiment has two legs, a front leg and a back leg, and is positioned inside the base material toward the surfboard 2 side, that is, toward the upper side.

[0088] In the base material in this fifth embodiment, a member other than the glass cloth 513 may be laminated on both sides of the core material 511 .

[0089] Further, the core material in this fifth embodiment is not limited to a plate material, and may be, for example, a wire material as in the first and second embodiments, or a combination of a wire material and a plate material as in the fourth embodiment.

[0090] Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention also includes modifications and additions that do not deviate from the gist of the present invention.

[0091] For example, in the above embodiment, examples have been described in which wire or plate material is used as the core material, but this is not limited to this, and the core material may be, for example, a bundle of thin wires such as piano wire, or a material processed into a mesh or woven fabric.

[0092] Additionally, the entire leg of the fin may be configured as part of the core material. [Explanation of symbols]

[0093] 1C Center fin (fin) 1L, 1R Side fins (fins) 2. Surfboard (Board) 2a back side 3 Fin box 4 Volts 10 Base material 10a Rear edge 10b Bass 10c Insertion hole 11 Core material 11a Rear end 11b Tip 11c,11d Upper end 12 Legs 12a Top side 210 Adhesive 211A Core material 211Ab Tip 211Ac end 211B Core material 211Bc End 211Bа Rear end 311 Core material 311a rear end 311b tip 411A Core material 411Aa rear end 411Ab Tip 411B Core material 511 Core material 513 Glass Cloth P1 base point P2 Vertex α,β Virtual line

Claims

1. A fin attached to the underside of the board, The fin is characterized in that a core material having high strength is arranged biased toward the board side.

2. The fin according to claim 1 , wherein the core material is arranged along the outer shape of the fin.

3. 3. The fin according to claim 1 or 2, wherein the core material extends to a leg of the fin attached to the back side of the board.

4. 4. The fin according to claim 1, wherein a tip of the core material is located closer to the board than an apex of the rear edge portion of the fin.

5. 5. The fin according to claim 1, wherein the rear end of the core material is located forward of a base point of the rear edge portion of the fin.

6. The fin according to any one of claims 1 to 5, wherein the core material is a wire material.

7. The fin according to any one of claims 1 to 6, wherein the core material is bonded to the base material.

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