Surfboard fin
Kind Code:

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.

Turkington, Britt Keith (Port Isabel, TX, US)
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International Classes:
B63B35/79; (IPC1-7): B63B1/00; B63B3/38; B63B35/00; B63B41/00
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Primary Examiner:
Attorney, Agent or Firm:
Britt Turkington (Port Isabel, TX, US)

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.



[0001] Invented is a fin which pertains to water planing devices, namely, a surfboard (a wave riding vehicle). The invented fin (located in the center rear position) works in conjunction with side fins, which are in most cases, already existing on the surfboard. This new technology could, however, lend itself to custom placed side fins to achieve a different result. The invented fin is a vertical foil, with two bilaterally attached horizontal foils toward the vertical fin tip. These foils are forward leaned, to control the water flowing between said horizontal foil, the vertical foil, the surfboard surface and the opposing side fin configuration. This creates two chambers (semi enclosed) of water passing under the rear section of said surfboard. The fin is constructed of, but not limited to, fiberglass or carbon fiber. First the vertical fin is constructed, currently in a mold, then set into a jig, where the horizontal foils are attached at a desired angle. The horizontal foils are also made of fiberglass or carbon fiber, and they also may be handcrafted or molded pieces. The horizontal foils are affixed to the vertical foil using a common bonding method (in surfboard manufacturing), using fiberglass rope at the seams, and laying fiberglass cloth over the rope and overlapping onto the desired adhered surfaces. The result is an inverted “T” shaped fin. This fin, when installed in the center rear position of a common modern three fin surfboard, will result in two semi controlled chambers of water passing under the rear section of said surfboard. Furthermore, if this invented fin were to travel backward it would provide lift, because of the reverse travel of the forward leaned horizontal foils. This characteristic lends itself to the ability to attach the same or similar fin configurations to both ends of the underside of a surfboard and achieve a surfboard that may be indiscriminately ridden without regard to nose and tail or front and rear. The forward mounted fin will provide lift, while the rearward mounted fin will provide down force.


U.S. Patent Documents

[0002] 1

5309859May 1994Miller114/274
5152705October 1992Rock441/74 
5057045October 1991Myers441/79 
5062378November 1991Bateman114/274
4320546March 1982Knox441/74 

Foreign Patent Documents

[0003] 2

2516472May 1983FR441/79
2828859January 1980DE441/74


[0004] The present invention is related to water planing devices herein referred to as a surfboard, and particularly a surfboard having hydrodynamic fin properties, which provide the surfboard with controlled chambers of water at the underside rear section of said surfboard, as well as providing lift should the hydrodynamic fin travel backward. This fin may be used as a replacement for the center rear fin of a common modern multi-fin surfboard, to achieve this chambering effect with negative lift properties. Furthermore, this fin when traveling backwards provides lift, should the surfer re-enter the breaking wave backward, with less incidence of submerging the tail of the backward traveling surfboard. These properties allow said fin to be positioned, with the complementing side fin configurations, at both ends of a surf or planar type board, to achieve a surfboard capable of generating speed, on a breaking wave, with either end being used as the tail or rear section. Inherently surfboards generate their speed using the fin configuration at the rear of the surfboard. the forward mounted fin will then be traveling backwards, with the reverse traveling foils providing lift to the forward section of said surfboard. A previous patent with down force technology, U.S. Pat. No. 4,320,546, is a surfboard. This patent describes down force technology in the same area of the surfboard, however, is not using a side fin configuration to create a variable between the center fin and a vertical side fin. The side fin configuration with horizontal foils in place on the center rear fin, does not create a complete enclosure, but the effects of chambering the water under the surfboard are obvious when used and adjusted with different fin sizes, profiles, angles, and placements. Furthermore, no patent researched uses the same or similar type fin on the front and rear of a surfboard to achieve a lift and down force effects simultaneously.


[0005] The invention comprises of a surfboard, having a planing hull, and a unique fin configuration characterized by a configuration consisting of at least three vertical foils; one foil located on each side toward the rear underside section and one vertical foil located further rearward in the center. This center rear vertical foil is constructed with two symmetrically placed horizontal foils located toward the fin tip. These horizontal foils are forward leaned to provide down force to the forward traveling surfboard, as well as lift for the tail, should the surfboard travel backward. This allows for the configuration to be applied to both ends of a surfboard, if desired, to achieve an omni-directional surfboard, or one that will be able to turn one hundred eighty degrees and continue to surf forward without loss of fin propulsion. If a surfer decides to replace the center rear fin of a common multi-fin surfboard, with the hydrodynamic fin, the benefits will be extra grip of the existing side fins as well as having a foil that maintains verticality while the surfboard is executing a turn. Furthermore, the hydrodynamic fin's profile is lower than that of a standard common vertical foil. This gives the surfboard a looser feel without sacrificing speed or maneuverability and also facilitates in tail-first re-entries, by providing positive lift due to the reverse traveling forward leaned horizontal foils.


[0006] FIG. 1 is a side and sectional rear bottom view of a conventional modern surfboard, using a three fin configuration. The arrow above the surfboard depicts the direction of travel in which the surfboard is capable of generating speed on a breaking wave.

[0007] FIG. 2 is a side and sectional rear bottom view of a conventional modern surfboard using the invented hydrodynamic fin in the center rear position.

[0008] FIG. 3 is a side and bottom view of a surfboard using the invented fin, with side fin configurations, on the forward and rearward sections of said surfboard. The arrow placed above the top surface of the surfboard depicts the directions of travel in which the surfboard is capable of generating speed on a breaking wave.

[0009] FIG. 4 is a perspective view of the bottom rear section of a modern surfboard 1 having a replaceable fin fixture system 4, wherein the invented fin 3 is used to replace the center fin of said conventional surfboard.

[0010] FIG. 5 is a side view of the invented hydrodynamic fin 3 with an arrow placed above the fin to depict the direction of travel to generate down force.

[0011] FIG. 6 is a bottom view of the invented hydrodynamic fin 3 depicting the profile of the horizontal foils 6.

[0012] FIG. 7 is a front view of the invented hydrodynamic fin 3, illustrating the horizontal foils 6 attached to the vertical foil 5.


[0013] FIG. 1 is a side and bottom rear sectional view of a conventional modern surfboard using a three fin configuration. The illustration depicts that there is a top and bottom surface of the surfboard, and that the vertical fins are located on the bottom rear section of the surfboard. The arrow placed above the top surface of the surfboard depicts the direction of travel in which the surfboard is capable of generating speed on a breaking wave. The bottom rear sectional view illustrates the positioning of the three vertical foils.

[0014] FIG. 2 is a side and sectional bottom rear view of a conventional surfboard, with the invented hydrodynamic fin replacing the common vertical foil. The bottom rear sectional illustrates the profile of the horizontal foils attached to the center rear vertical foil. The illustration also depicts that there are two vertical foils placed forward and toward the sides of the bottom rear section of the surfboard.

[0015] FIG. 3 is a side and bottom view of an exemplary embodiment of this invented fin. When accompanied by the vertical side fins, and mounted on the forward and rearward sections of a surfboard, enables the surfboard to generate speed with the rearward placed fin configuration, while the reverse traveling forward fin provides lift, due to the reverse travel of the otherwise negative lift inducing horizontal foils. The arrow placed above the top of the surface of the side view indicates the surfboard is capable of generating speed in two directions. The bottom view illustrates the cluster of the fin configurations located at each end of the surfboard.

[0016] FIG. 4 is a perspective view of the bottom rear section of a conventional surfboard 1, generally constructed from shaping closed cell foam and encasing the shape with fiberglass and polystyrene or epoxy resins, and fitted with a common fin fixture system 4, i.e. U.S. Pat. No. 5,464,359, which is a molded plastic receptacle which receives a fin 2 manufactured with a male counterpart or tab. The fin is held in place by a set screw, located in the receptacle 4. The invented hydrodynamic fin 3 is shown to replace the vertical profile fin 2 in the rear center position.

[0017] FIG. 5 is a side view of the invented hydrodynamic fin 3. This fin is constructed with either fiberglass, carbon fiber, or molded plastic. Currently, the vertical foil 5 is made by using a pre-cut piece of balsa wood for core. This is encased by carbon fiber cloth and placed in a mold, which is then injected with polystyrene resin. The horizontal foils are made in the same manner. The vertical foil is then placed in a jig, which will hold the horizontal foils 6 at a desired angle for attachment to the vertical foil. The hydrodynamic fin 3, may also be manufactured using a four piece mold and injected with plastic. The hydrodynamic fin 3 may be manufactured to fit in receptacles as illustrated in FIG. 4, or manufactured to be permanently attached to the surfboard (the plastic fin excluded). Fiberglass and/or carbon fiber are preferred for permanently placed fins. In this case the vertical foil is made without a male counterpart to the receptacle, and fastened to the surfboard before the installation of the horizontal foils. This allows for a stronger assembly. It is possible, however, to attach a prefabricated hydrodynamic fin by means of fiberglass cloth and strands of fiberglass rope, which is currently the most popular way of permanently affixing fins to a fiberglass surfboard. The vertical foil 5 extends arcuately downward and rearward with the radius decreasing toward the trailing edge. The horizontal foils 6 are attached bilaterally toward the vertical fin tip, and leaned forward to an indeterminate number, depending on the desired effect. A neutral fin would have horizontal foils 6 placed with an equal distance between surfboard to leading edge and surfboard to trailing edge. A negative lift fin would have a lesser number from surfboard to trailing edge as opposed to the measurement from surfboard to leading edge. The effects of a neutral foil are noticeable. However, some down force is usually desired. The arrow above the vertical foil 5 indicates forward.

[0018] FIG. 6 is a bottom view of the hydrodynamic fin 3 wherein the vertical foil 5 is joined with the horizontal foils 6 mounted symmetrically on opposing sides. The horizontal foils 6 arcuately extend rearward with the trailing edge being somewhat arcuately relieved. The arrow in the diagram indicates forward.

[0019] FIG. 7 is a front view of the hydrodynamic fin 3, wherein the vertical foil 5 is joined with the horizontal foils 6 located bilaterally toward the vertical foil 5 fin tip. The illustration indicates a slight forward lean of the horizontal foils 6. This down force angle adjusts the amount of water traveling between the side fins 2, horizontal foils 6, vertical foils and surfboard bottom. 1. This angle also induces a faster turning surfboard. This reaction takes place when the maneuvering surfboard turns, it tilts, causing the horizontal foils 6 to tilt toward vertical. When influenced by a forward leaned foil, this causes or facilitates a sharper or tighter turn.