Patent Application
20140209006
This patent application relates generally to the field of watercraft and, in particular, a stabilizing fin for watercraft.
Stabilizing fins are primarily used on a watercraft such as sail boats or any similar water going vessels which use a fin or keel and water sports boards such as surfboards, wind-surf boards, kite-surf boards, stand up paddle boards, wake boards and the like. Generally, surf boards, windsurf boards, SUP boards, wake boards and kite surfing boards have a fin or multiple fins attached to their bottoms that enable steering of the board and the ability to counteract the lateral force that tends to move the board in a lateral direction due to the direction of moving of the board on a wave.
In sail boats the main purpose of the keel is to counteract the force of the wind. On sail boats, the wind provides a force which enables the sail boat to move in its desired direction. The force which is caused by the wind is a lateral force which tends to tip the sailing boat.
When it is at rest, a watercraft's weight is borne entirely by the buoyant force of the watercraft. At low speeds generally the watercraft hull (or body, board, etc.) acts as a displacement hull, meaning that the buoyant force is mainly responsible for supporting the watercraft. As speed increases through the water, the shape of the hull causes hydrodynamic lift to increase as well. At some speed, hydrodynamic lift becomes the predominant upward force on the hull and the craft is “planing”. Planing decreases drag on the body of the watercraft and allows for increased speed of the watercraft.
Standard fin structures for use in watercraft such as water sports boards generally have one or more single solid fin structures (i.e. not having any openings for the water to flow through) extending from the bottom of the watercraft into the water. Current standard fin structures generally extend along a vertical axis of symmetry and have a symmetrical profile across that axis. Standard fin structures can vary by having different depths, rake angles (extending in the direction of water flow), surface area and cross-section profiles that all depend on the purpose of the board and operating conditions and desired performance characteristics.
In the case of standard fin shapes, when moving through the water, water is flowing in the direction from the leading edge of the fin towards the trailing edge of the fin. In the vicinity of the fin, the water flow deflects and follows the shape of the fin. On each side of the fin, the local water velocity is increased relative to the hull which causes a pressure differential and lateral force is generated and acting on the surface of the fin, perpendicular to the axis of symmetry and direction of water flow. Because the cross section of standard fins have a symmetrical hydrodynamic profile, the lateral force is generated equally on the two opposing sides and act against each-other thereby giving lateral stability to the hull. Because the fin is moving through water, resistance force which occurs acting in the direction the water is flowing, causing what is commonly referred to as fin drag. In addition, because of the symmetric profile of the fin structure, no significant longitudinal force (hydrodynamic lift) is generated to counteract the force of gravity pushing the board into the water therefore does not get the board on plane more easily.
What is desired is a fin structure that provides lateral stability and generates hydrodynamic lift allowing the watercraft to get on plane more easily.
It is with respect to these and other considerations that the disclosure made herein is presented.
According to a first aspect, a fin structure for use in water is provided. The fin structure includes a body having a first end and opposite second end. The body has a first sidewall and a second sidewall that are at least partially spaced apart from one another so as to form an opening in between the two sidewalls. The sidewalls extend from first end toward the second end, and as the two sidewalls extend, the sidewalls diverge away from each other in the upper region. The two sidewalls then converge in the lower region. In addition, the fin structure can include a bottom portion that connects at least a portion of the first and second sidewalls.
According to another aspect, a fin structure for use in water is provided. The fin structure includes a body having a top end and a bottom end and a pair of sidewalls at least partially spaced apart from one another so as to define a through hole formed between the sidewalls. The through hole has: (1) a height measured along a longitudinal axis of the body that runs the length of the body and (2) a width measured along a horizontal axis that is perpendicular to the longitudinal axis. In addition, the height of the through hole is greater than the width of the through hole at any horizontal axis that is perpendicular to the longitudinal axis.
These and other aspects, features, and advantages can be appreciated from the accompanying description of certain embodiments of the invention and the accompanying drawing figures and claims.
By way of overview and introduction what is disclosed is a fin structure for use with watercraft that is configured to provide lateral stability and generate hydrodynamic lift to counteract the force of gravity pushing the watercraft and the fin structure into the water and allow the watercraft to plane more easily. In a preferred arrangement the fin structure can be connected to the underside of a hull at a first end. Two sidewalls extend away from the first end down into the water (i.e. along a longitudinal (vertical) axis away from the underside of the hull). As the side walls extend away from the hull, they also first diverge relative to one another and then converge relative to one another to form a generally diamond shaped fin structure that is symmetric across the longitudinal axis and has an opening in between the sidewalls to allow water to flow through. Preferably, the sidewalls have a cross-section profile having outer surface of the sidewalls with more curvature than the inner surface. The symmetric shape of the fin structure provides lateral stability, while the asymmetrical cross-section creates hydrodynamic lift in the longitudinal direction and acting against gravity. In addition, maneuverability is increased.
The referenced systems and methods are now described more fully with reference to the accompanying drawings, in which one or more illustrated embodiments and/or arrangements of the systems and methods are shown. The systems and methods are not limited in any way to the illustrated embodiments and/or arrangements as the illustrated embodiments and/or arrangements described below are merely exemplary of the systems and methods, which can be embodied in various forms, as appreciated by one skilled in the art. Therefore, it is to be understood that any structural and functional details disclosed herein are not to be interpreted as limiting the systems and methods, but rather are provided as a representative embodiment and/or arrangement for teaching one skilled in the art one or more ways to implement the systems and methods.
In addition, the fin can include a bottom portion 160 that integrally connects the first and second sidewalls. In this exemplary variation of the disclosed embodiments, the bottom portion integrally connects the distal end of the first and second sidewalls such that the opening is completely bounded by the first and second sidewalls and the bottom portion. Alternatively, the bottom portion can integrally connect the first and second sidewalls at any location of the first and second sidewalls to define an opening that is bounded by a portion of the first and second sidewalls and the bottom portion. The bottom portion can be an arcuate shaped wall, however the bottom portion can take alternative shapes as would be understood by those skilled in the art. Moreover, preferably the bottom portion is bisected by the longitudinal axis 111.
Preferably, the fin structure is symmetric across the longitudinal axis and as such the first sidewall 115 and the second sidewall 125 mirror one another (have identical yet reversed shapes).
Fin 100 can also include one or more mounts 112 located at the first end. Mount 112 has the primary purpose of connecting the fin structure to a vessel as would be understood by those skilled in the art.
Turning briefly to
In reference to
Preferably, mount, first and second sidewalls and bottom portion are made from the same material, however a combination of materials can be used. In addition, the fin structure can be made from multiple pieces. One or more pieces of the fin structure can also be made by multiple pieces joined together by heat welding, glue or other adhesive, fasteners, joints or other suitable temporary or permanent joining means. Alternatively, one or more pieces of the fin structure can be formed as a single structure. Preferably, the fin structure is made of a light sturdy plastic, such as acrylonitrile-butadiene-styrene copolymer, polyethylene, polyvinyl chloride, polycarbonate, polyproplene or styrene and the like. It may, however, be made from any strong, sturdy and water resistant material, such as metals, composites, fiberglass and the like as would be understood by those skilled in the art.
In this exemplary embodiment, fin 100 has a generally diamond shape with a generally diamond shaped opening 102. More specifically, first upper sidewall 120 and second upper sidewall 140 each generally extend from the first end 110 along the longitudinal axis 111 and the horizontal axis 113 at the angle α1 relative to the longitudinal axis 111. Preferably angle α1 is within the range of 0 to 75 degrees, and can be varied according to the desired hydrodynamic characteristics of the fin. Preferably, and without limitation, the first and second upper sidewalls have an identical length 192 which is greater than 0 and less than the depth 190 of the fin 100. First lower sidewall 130 and second lower sidewall 150 extend from the distal end of the first upper sidewall 120 and second upper sidewall 140, respectively at an angle α2 relative to the longitudinal axis. Preferably, the length 194 of the first and second lower sidewalls is identical and is a function of the fin depth 190, length 192 and angles α1 and α2. In addition length 194 can also be a function of the dimensions of the bottom portion 160.
Turning now to
Referring now to
The particular shape of the cross-section 178 for the various portions of the first and second sidewall, transitions and bottom portion 160 of the fin vary depending on the desired performance characteristics of the fin 100. The main purpose of the fin is to provide stability of the board and better guidance during maneuvers and tricks on the water. More specifically, the performance of the fin generally depends of fin depth (i.e., length 190), fin rake angle, cross-section 178 and the surface area of the fin. The variations of cross-section shapes, including sidewall curvatures that can affect hydrodynamic lift, maneuverability and other performance characteristics would be understood by those skilled in the art. For example, in the upper region, the outer surface can have a greater curvature than the inner surface to provide hydrodynamic lift; in addition, for at least a portion of the lower region, the radius of curvature of the outer surface can be greater than the inner surface to provide some downward hydrodynamic force, in addition, the radius of curvature of the remaining pieces of the lower region including the bottom portion 160 can have an inner surface with a greater radius of curvature than the outer surface to provide hydrodynamic lift, generating a net lifting effect by the fin.
Although the disclosed embodiments of the present invention describe a fin 100 that is symmetric across the longitudinal axis it should be understood that, depending on the desired performance characteristics, the fin can be asymmetrical and first and second sidewalls and/or bottom portion can have non-mirrored cross-sections when taken in the transverse direction at the same point along the longitudinal axis. For example, non-symmetric fin shape may be desirable if, say, the fin needs to pull in a particular horizontal direction more.
In reference to
In practice, the direction of water flow 117 is from the leading edge 170 of the fin 100 towards the trailing edge 172. In the vicinity of the fin the water flow deflects around the fin and follows the shape of the fin. Because the cross-section of the fin is a hydrodynamic profile the disclosed embodiment generates beneficial performance characteristics
In a standard shaped fin 600, as depicted in
In the practical application of a standard shaped fin 600 on, say, a surfboard, the board itself must be buoyant to counteract gravity and keep the board and a surfer standing on the board afloat. The board itself is buoyant and floats on the water with the surfer on it the weight is increased and extra lift is needed to stay on the surface. When the board is moving the board shape generates hydrodynamic lift force in the longitudinal direction which supplements buoyancy and keeps the board and surfer on the surface. The greater the speed of the board, the greater the hydrodynamic lift is generated. As explained, standard fins moving through the water provide extremely small hydrodynamic lift or in most cases no hydrodynamic lift at all to counteract gravity.
In practical application of the fin structure 100 as described in relation to
For example, provided two equal boards, the first having a standard fin shape and the second having a fin 100 according to the disclosed embodiments, the second board will plane sooner. Moreover, the second board should have relatively better control and maneuverability on turns. More specifically, with a standard fin on a turn, the board is deflected and also is the fin (i.e., the board and fin are rotated about the direction of water flow 117). Because of the rotation, the surface area which provides lateral force in the horizontal direction 113, is reduced. The greater the deflection of the board and the fin, the greater the reduction of the surface area providing lateral force and consequently a decrease in lateral force which provides stability. However, when a turn is made using fin 100, significant lateral force is maintained because the generally diamond shape maintains significant surface area that is laterally inclined (i.e., oriented generally along the longitudinal axis 111) and providing lateral force. When upright (i.e., inclined in the longitudinal axis), the upper first sidewall 120, lower first sidewall 130 oppose the lower second sidewall 150, upper second sidewall 140 and lower second sidewall 150 are. In a turn, where the axis of rotation is the water flow direction 117 and we rotate the fin in a counterclockwise direction, than the upper second sidewall 140 and lower first sidewall 130 move toward alignment in the longitudinal axis 111. Accordingly, upper second sidewall 140 and lower first sidewall 130 oppose one another and provide a full surface on which lateral force in horizontal direction 113 is generated. In addition, the use of asymmetric profile adds to better maneuverability. Varying the length and cross-section of upper first sidewall 120, lower first sidewall 130, lower second sidewall 150, upper second sidewall 140 as well as angles α1, α2, rake angles and other physical attributes of fin 100 can adjust the performance characteristics of fin 100 including the amount of hydrodynamic lift, stability, drag and maneuverability as would be understood by those skilled in the art.
Thus, while there have been shown, described, and pointed out fundamental novel features of the invention as applied to several embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit and scope of the invention. Substitutions of elements from one described embodiment to another are also fully intended and contemplated. It is also to be understood that the drawings are not necessarily drawn to scale, but that they are merely conceptual in nature. The invention is defined solely with regard to the claims appended hereto, and equivalents of the recitations therein.
