FIELD OF THE INVENTION

This invention relates to a fin for a board such as a surfboard and the like.

BACKGROUND TO THE INVENTION

Boards that are used in water sports, such as surfboards, are fitted with fins to provide grip in the water. The board itself is smooth, and even polished. This reduces drag - as it is intended to do - but of course it also means a board in itself has no significant steering capability.

Surfboards are therefore fitted with one or more fins extending into the water from its operative bottom rear. Fins contribute significantly to the speed and power attainable with a surfboard, which impacts its performance.

Specific fins suit specific conditions better. Central fins are often as stabilisers whilst rail fins, mounted on the sides of the central fin, are often foiled on one side only. The dimensions of the fins may vary, each being suitable for specific wave conditions. Rail fins may also be toed- in, which means the leading edge of the rail fin is angled slightly inwards towards the centre fin.

Several aspects of a fin design determines the fin’s performance, and these characteristic aspects include the fin’s area, base, depth, sweep, flex, template, foil, toe angle, cant, and angle of attack.

A limitation with conventional fins is that each fin has a predetermined fixed characteristic, through a predetermined shape and configuration. Different fins suit different conditions, but no prior art fin is adaptable to changing conditions.

Fins used to be glassed-in which set a specific fin configuration to a board. Since the 1960’s removable fins have been used, which allow a surfer to change the style, shape and size of fins fitted to a board at will. This is done by means of a key, typically in the form of a screw driver. Even though removable fins provide a surfer with for more options, it also complicates his life since he now has to carry as many spare fins with him as he may need for the changing conditions he may encounter on a surfing outing. And then each fin is only really perfectly suited for one set of conditions, so if the conditions change to somewhere between what is best served by two different fins, then the surfer won’t have a specific fin for such conditions and whichever fin he uses will be a compromise to the present conditions.

OBJECTIVE OF THE INVENTION

It is an objective of the invention to provide a fin which at least partly overcomes the abovementioned problems.

SUMMARY OF THE INVENTION

In accordance with this invention there is provided a board fin which includes a base for securing the fin to a board, with a fin body extending from the base; the fin body comprising an internal structure covered by a flexible skin, with the internal structure being adjustable to change the external characteristic of the fin body, the fin being provided with means to adjust the internal structure whilst the fin is secured to a board.

There is further provided for the internal structure to be adjustable to change the external characteristic of the fin in respect of any one or more of its area, base, depth, sweep, flex, template, foil, toe angle, cant, and angle of attack.

There is also provided for the adjustment means to comprise at least one movable member extending into the internal structure, and being movable between a minimum and maximum position, the movable member being accessible by means of a key through a key hole located in the fin, preferably in the base of the fin, operatively to allow adjustment of the movable member.

The one moveable member may be in the form of a full fin and the full fin may be moveable between a minimum and maximum position and thereby controlling at least one aspect of the external characteristics of the board fin through adjustment thereof by the key through a complementary key hole.

There is further provided for the fin to include a plurality of movable members extending into the internal structure, each being movable between a minimum and maximum position and each controlling at least one aspect of the external characteristic of the fin through adjustment thereof by the key through a complimentary key hole. There is further provided for the fin to be a glassed-in fin or a removable fin, and for the fin to be a surfboard fin. In the case of a removable fin, the surfboard fin may include a fin attachment means which provides for adequate attachment of the board fin to the board.

There is further provided for the skin to be comprised of a resiliently flexible material, preferably a rubber material.

These and other features of the invention are described in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention is described by way of example only and with reference to the accompanying drawings in which:

Figure 1 is a side elevation view of a section through a fin according to a first embodiment of the invention;

Figure 2 is an end elevation of the fin of Figure 1 in its normal position;

Figure 3 is an end elevation of the fin of Figure 1 curved to its right;

Figure 4 is an end elevation of the fin of Figure 1 curved to its left;

Figure 5 is a side view of the fin box;

Figure 6 is a perspective view of the base of the surfboard fin including prongs;

Figure 7 is a side view of the board fin engaged with the fin box; and

Figure 8 is a perspective view of the board fin and the fin box, showing the knurled head of the pin.

DETAILED DESCRIPTION OF THE INVENTION

The“ Surf Science” Internet blog (http://www.surfscience.com) provides a succinct analysis of the goals and characteristics of surfboard fins and how they impact the way a surfboard handles, which includes the following: Goals of Surfboard Fins

Drive

Simply said, fins will help you accelerate out of turns if you put enough pressure against them. While fins produce drag for a board going straight, the water surging against a fin in mid turn will produce a feeling of acceleration. This is known as drive. The best analogy to use is a swimmer approaching a pool wall, preparing to hit the wall and catapult in the opposite direction. Springing off the wall is similar to laying into a turn and applying a lot of pressure against the fins. Both actions will accelerate the athlete out of the turn. This is drive.

Lift

This is the force on a fin that provides vertical lift. Fin cant increases fin lift. The greater the lift, the greater the hold a fin will have in a waves face.

Hold

Hold prevents a surfboard from sliding out during turns.

Characteristics of Surfboard Fins

Area

Measures the two-dimensional area of a fin in square millimetres. Larger surfers will need more area to provide necessary hold, while smaller area will result in a looser board.

Base

The length of the fin where it meets the board. Fin base affects the drive of the board. The longer the base, the more surface area a surfer has to push against the wave, producing more drive. Fins with a smaller base will have a shorter turning arc.

Depth

Measures how far a fin penetrates the water. Depth influences drive and hold. A fin with shorter depth will offer more slide to a surfer. Longer depth will produce more hold. This is especially true of center fins.

Sweep

This is a fancy way of identifying how far the fin curves backward. The degree is measured between a vertical line extending straight upward from the midpoint of the fin's base to the line connecting the midpoint of the base to the fin's highest point. A higher degree sweep produces longer arcing turns while less sweep allows more of a pivot movement.

Flex

Flex is the amount a fin will bend from the straight position. A fin with more flex will be forgiving loosening the board while a stiffer fin will respond better, improve speed and drive. A fin with a stiff base with a more flexible tip is an ideal setup.

Template

This is the outline of a fin's shape. It includes the depth, area, base, and sweep of the board.

Foil

This is the shape of the fin if viewed upside down, staring at the bottom of the fin. Some foils are totally symmetrical, where the inside surface and outside surface are curved exactly the same. Other foils are asymmetrical, having one surface shaped differently than the other. Foil affects the lift and drag of a fin similar to how an airplane wing’s foil creates lift.

Toe Angle

The angle of the side fins in relation to the stringer.

Cant

This measures the degrees in which a fin leans away from being totally perpendicular to the board's bottom surface. Picture the fin leaning toward the outside rail or toward the middle of the board.

Angle of Attack

The fin's angle in relation to the water moving around it.

The invention

The invention provides a board fin (1 ) which includes a base (2) for securing the fin (1 ) to a board (not shown). The base (2) includes at least two prongs (2A, 2B, 2C, 2D) which are shaped and configured to removably secure the fin in an attachment means, namely a fin box (10) which forms a part of the board (not shown) or attachable to a board to allow for securing the board fin (1 ) thereto. The board fin (1 ) includes a fin body (3) that extends from the base (2). The fin body (3) comprises an internal structure (4) covered by a flexible skin (5), in this instance a resiliency flexible rubber with a smooth surface. The internal structure (5) is adjustable to change the external characteristic of the fin body (3).

In an embodiment of the invention, the internal structure (5) comprises one moveable member, in the form of a full fin (1 ) including a base (2) which defines a number of prongs, which follow a helical profile longitudinally and are complimentarily shaped, dimensioned and configured to engage the fin box (10).

The fin box (10) includes a number of complimentary shaped recesses to accept the prongs defined by the base (2) of the surfboard fin (1 ). The prongs (2A, 2B, 2C, 2D) complementarily engage the fin box (10).

A number of the prongs (2A, 2B, 2C, 2D) and the fin box (10) define complementary located apertures shaped to receive a key / pin (12), the key being in the form of a lead screw, which is seated in and rotates in the complementary located apertures, thereby securing the surfboard fin (1 ) to the fin box (10) of the board and allowing for movement of the board fin (1 ) by the user.

The lead screw of the key / pin (12) defines a knurled head (14) which, when rotated by the user, assists in the movement of the surfboard fin (1 ). The rotation of the knurled head (14) provides a combination of linear and angular movement of the surfboard fin (1 ). The rotation of the knurled head (14) of the key (12), and approximately 5mm of linear motion can provide an angular adjustment of the surfboard fin (1 ) of approximately 10 degrees.

Adjustment of the design of the base prongs (2A, 2B, 2C, 2D) and the fin box (10) can control the degrees of movement of the surfboard fin (1 ).

In a second embodiment of the invention the internal structure comprises a set of interconnect segments (6), which in assembly provides a framework for the skin. The segments (6) includes a first segment (6A) secured to the base segment (6A). A second segment (6C) is secured to the first segment (6B), a third segment (6D) to second segment (6C), and so on up to 8 segments (6A - 6H ) in this embodiment of the fin (1 ). The first segment (6B) is slightly rotatably adjustable with respect to the base segment (6A), allowing it to be located in a neutral centre position where it is perfectly level with the base segment (6A), as shown in Figure 2, a right angled configuration as shown in Figure 3, and a left angled configuration as shown in Figure 4.

Similarly, the second segment (6C) is rotatably adjustable with respect to the first segment (6B), and so forth for each further segment that is rotatably adjustable with respect to the segment to which it is secured on the side of the base segment (6A).

This means that each segment (6B to 6H) from the second segment onwards is rotatably adjustable with respect to the segment that precedes it in the segment assembly. Although each rotational adjustment is relatively small, the cumulative effect of the adjustments is significant when comparing the tip (7) of the fin (1 ) to the base, as shown in Figures 3 and 4.

In Figure 3 the assembly is angled to the right (8), and as shown in Figure 4 the assembly is angled to the left (9)

In the second embodiment shown in Figure 1 to 4, the fin (1 ) includes adjustment means to adjust the internal structure whilst the fin is secured to a board. The adjustment means (not shown) comprises a movable member extending into the internal structure (4), and being movable between a minimum and maximum position, the movable member (not shown) being accessible by means of a key (not shown) through a key hole (not shown) located in the fin (1 ), operatively to allow adjustment of each movable member.

There is further provided for the internal structure to be adjustable to change the external characteristic of the fin in respect of any one or more of its area, base, depth, sweep, flex, template, foil, toe angle, cant, and angle of attack. Each of these aspects of the characteristic of the fin will be adjustable by configuring the internal segments to be movable with respect to each other in the assembly, and by providing a key to rotate a movable member to move the segments in the assembly each between its minimum and maximum positions, corresponding with the extremes that each such aspects of the characteristic of the fin is adjustable between.

It will be appreciated that the range of movement required to move a movable member between a minimum and maximum for one of the aspects may be different from that required for another aspect. Each movable member may be provided with its own key hole, located at a position to give optimal access to the specific movable member.

It will be appreciated that use of the adjustable board fin allows it to be used in a more traditional glassed-in configuration or in the more modern removable configuration.

It will be appreciated that the embodiment described above is given by way of example only and is not intended to limit the scope of the invention. It is possible to alter aspects thereof without departing from the essence of the invention.

It is for example possible to use the fin according to the invention with water boards other than surfboards, for example with kite surfing boards, wave boards and the like.