Abstract: [Problem] The present invention relates to a surfboard fin attachment structure. More specifically, the invention addresses the problem of providing a surfboard fin attachment structure, which is capable of detachably attaching a fin to a surfboard, wherein the attachment structure is capable of tight fitting even though easy attachment and detachment are possible and allows fitting without fin shaking or shuddering. [Solution] A surfboard fin attachment structure comprising: pin insertion recesses on both side surfaces of a cavity and, continuous therewith, grooves that continue in the depth direction of the cavity, said grooves extending from a given depth towards the back of the direction of board movement in the longitudinal direction of the fin box; and, on both sides of the fin attachment base, pins corresponding to the pin insertion recesses.

Abstract: Tool-less detachable fins and fin assemblies for watersport boards (e.g, surfboards, wake boards, windsurfing boards, kite boards, stand-up paddle boards and the like) are disclosed. Some embodiments are directed toward detachable fin assemblies which include a fin having a mounting tang defining at least one detent recess in an edge thereof, and a fin box defining an elongate mounting channel for receiving the mounting tang of the fin. The fin box includes at least one spring-biased ball detent assembly having a ball detent positioned so as to engage the at least one detent recess when the mounting tang is positioned within the mounting channel to thereby removably fix the fin to the fin box. The fin box may include at least one threaded aperture for receiving a ball detent assembly therein.

Abstract: [Problem] The present invention relates to a surfboard fin attachment structure. More specifically, the invention addresses the problem of providing a surfboard fin attachment structure, which is capable of detachably attaching a fin to a surfboard, wherein the attachment structure is capable of tight fitting even though easy attachment and detachment are possible and allows fitting without fin shaking or shuddering. [Solution] A surfboard fin attachment structure comprising: pin insertion recesses on both side surfaces of a cavity and, continuous therewith, grooves that continue in the depth direction of the cavity, said grooves extending from a given depth towards the back of the direction of board movement in the longitudinal direction of the fin box; and, on both sides of the fin attachment base, pins corresponding to the pin insertion recesses.

Abstract: To provide a fin attachment structure capable of facilitating the attachment/detachment of a fin and also of making the attachment of the fin robust, wherein if the fin comes into contact with human body from behind during surfing, the impact of the fin can be eliminated to restrict the damage to the human body to an extreme minimum and thus safety is improved.

Abstract: An object of the present invention is to provide fin in which the fin can be easily attached or detached to a board, its attached state can be maintained well, and the fin readily comes off in an emergency such as when the fin is brought into contact with human body. Furthermore, it is an object of the present invention to allow the reduction of rattle when the fin is attached. To solve such problems, provided is a fin, comprising a hollow part at a side surface of an attachment base portion of the fin to be attached to a groove in a bottom surface of a surfboard, wherein a ball part is biased outwardly of the hollow part by an elastic member in the hollow part; and wherein the ball part in the hollow part of the attachment base portion of the fin is moved into the hollow part against a biasing force from the elastic member, and thus the fin is detachably mounted in the attachment groove of this board under elastic compression force.

Abstract: An object of the present invention is to provide fin in which the fin can be easily attached or detached to a board, its attached state can be maintained well, and the fin readily comes off in an emergency such as when the fin is brought into contact with human body. Furthermore, it is an object of the present invention to allow the reduction of rattle when the fin is attached. To solve such problems, provided is a fin, comprising a hollow part at a side surface of an attachment base portion of the fin to be attached to a groove in a bottom surface of a surfboard, wherein a ball part is biased outwardly of the hollow part by an elastic member in the hollow part; and wherein the ball part in the hollow part of the attachment base portion of the fin is moved into the hollow part against a biasing force from the elastic member, and thus the fin is detachably mounted in the attachment groove of this board under elastic compression force.

Abstract: To provide a fin attachment structure capable of facilitating the attachment/detachment of a fin and also of making the attachment of the fin robust, wherein if the fin comes into contact with human body from behind during surfing, the impact of the fin can be eliminated to restrict the damage to the human body to an extreme minimum and thus safety is improved.

Abstract: To provide a fin attachment structure capable of attaching a fin detachably and easily on a board without using any tools, and particularly, to a fin attachment structure capable of reducing the damage to human body as much as possible when the fin comes into contact with the human body during surfing etc. and having an extremely high safety, and a fin. The above problem can be solved by a fin attachment structure and a fin, in which a groove part is provided on the bottom surface of the surfboard and a hollow part 10 is provided on the inner surface thereof, the hollow parts being further provided at the opposing positions on both side surfaces of the groove part, and an elastic member is provided at the deep side within the hollow part and a bail part at the opening side for biasing in the direction in which it projects to outside, wherein by the insertion of the fin attachment base portion into the groove part, the fin is biased and sandwiched and held by the ball part.