Surfboard fin

Abstract

A t-shaped, hydrodynamic fin (“t-fin”) for surfboards designed to maximize performance and maneuverability of the surfboard by creating, in conjunction with two vertical side fins, two chambers to funnel and control the flow of water. The crosspiece of the t-fin is parallel to the surfboard and is horizontal when the surfboard is level from side to side. But also functions as a vertical fin when the board is tilted sideways (in either direction) and the side fins lose their verticality. The t-fin enhances surfboard maneuverability by maintaining fin perpendicularity on the board at all times. The t-fin is fastened to the underside of the surfboard, at the stern, but a second t-fin may be fastened at the same time to the bow underside, to achieve a surfboard that can be used reversibly. T-fins are custom-made, shaped and contoured, and the crosspiece of the t-fin affixed, to achieve the desired hydrodynamic effect. T-fins utilize fin replacement systems, so that different designed t-fins (of varying degrees and profiles) may be used interchangeably with one another, but not limited to interchangeable fin systems. A fixed fin configuration (permanently attached) is sometimes desired.

I claim:  
     
         1 . A t-fin for use dorsally at the centerline of the underside of the surfboard (or planar-type board) that 
 (a) is custom-made, -shaped, -contoured and -designed to achieve the desired hydrodynamic effect;    (b) consists of a cross-piece attached to a (conventional) vertical tail fin (frontally appearing like an inverted t) with the leading edge of the crosspiece angled (in relation to trailing edge) at fixed, intermediate degrees, to achieve the desired hydrodynamic effect; and    (c) utilizes a standard plug-in system for attaching the t-fin to the surfboard, so that the custom-built t-fins (with crosspieces of varying angles) may be used interchangeably with one another.    
     
     
         2 . A t-fin as claimed in No. 1 above, used in conjunction with two vertical, side fins, in a 3-fin configuration that 
 (a) is positioned to form two chambers that funnel the flow of water;    (b) maintains fin perpendicularity at all times, including when the surfboard is tilted sideways; and    (c) keeps the trailing end of the surfboard (where the fins are attached) from lifting off the surface of the water as the surfboard moves forward.    
     
     
         3 . A t-fin, as claimed in No. 1 above (or a 3-fin configuration, as claimed in No. 2 above), used in conjunction with a second t-fin (or a second 3-fin configuration), each t-fin (or 3-fin configuration) attached to opposite ends of the surfboard, facing the other, that allows the surfboard to be used reversibly.