Abstract
The fields of application of the present invention is within the industry related to the manufacturing of nautical/marine and sport equipment, and more precisely to the field of fins design for any type of board within a fluid environment. The novelties of the Spinfins, compared to traditional fin designs, are: (i) the curvature in the vertical direction permits the fin to have sufficient surface exposed to the fluid to ensure directional control but its lower height yields to a lower drag in the direction of the motion and consequently is faster than traditional fins; and (ii) the angle of twist in the vertical direction of the fin permits to modify the leading and trailing edges angles relative to the flow resulting in a more uniform pressure on the concave surface of the fin. The more uniform pressure on the concave surface makes the force exerted by the fin more efficient throughout a turn.
Claims
1. The side-Spinfins have a curvature starting from the chord line at the asymmetric base of the fin and extending to the tip of the fin. The side-Spinfins has a continuous convex defbrmation in the vertical direction while the outside surface has a constant concave deformation.
2. The center-Spinfins is two side-Spinfins put together from their concave outside surface. The two side-fins put together create a symmetric foil at the base and a continuous curvature goes from center line (chord lide) to the point where the two side fins are not connected any longer. From that location to the tip the two extremities keep their unsymmetric foil cross-section.
3. Spinfins are the only fins that have a twist about the vertical axis. The angle of twist can be counterclockwise or clockwise modifying the angle of attack of the leading edge in the chord wise direction. The angle of twist create a variable angle of attack in the chord wise direction
4. Spinfins twist angle allows to have a more uniform pressure on the inside of the fin throughout a turn as compared to vertical fins.
Description
BRIEF DESCRIPTION OF DRAWINGS
[0021] In order to facilitate a fuller understanding of the present invention, reference is new made to the appended drawings. These drawings should not be construed as limiting the present invention, but are intended to be exemplary only:
[0022] FIGS. 1A-1D is schematic representation of a reference fin to be used for comparison purposes.
[0023] FIG. 2 is a schematic of the reference fin and an exemplary Spinfins.
[0024] FIGS. 3A-3D is a schematic of the side Spinfins from different views.
[0025] FIGS. 4A-4D is a schematic of the center Spinfins from different views.
[0026] FIGS. 5A-5C is a schematic of an exemplary fin indicating how the twist of the Spinfin is defined.
[0027] FIG. 6 is the plot of C.sub.d Vs. Angle of Attack for reference and exemplary Spinfins.
[0028] FIG. 7 is the plot of C.sub.L Vs. Angle of Attack for reference and exemplary Spinfins.
[0029] FIG. 8 is the plot of C.sub.L/C.sub.d Vs. Angle of Attack for reference and exemplary Spinfins.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0030] FIG. 1A shows the geometry of a traditional side fin that is used as a reference and comparison object for the present patent application. The figure shows the side view of the reference fin with the general terminology used to describe a fin. The base is defined as the distance between the leading edge to the trailing edge of the fin. The depth is the distance from the base to the maximum distance of the fin in the vertical direction. The sweep is the measurement that defines how far back the fin curves in relation to its base.
[0031] FIG. 1B shows the front view of the reference fin and it clearly indicates that the reference fin, like most all fins, do not have any curvature in the vertical direction.
[0032] FIG. 1C shows the isometric view of the reference fin with a demarcation for the detailed view of the cross section.
[0033] FIG. 1D shows the detailed view of the cross section. The figure indicated that contour shape of the cross section follows a foil geometry. Foil refers to the shape of the outside and inside faces of the fin, thinnest near the tip and thicker near the base. Foil alters the flow of the water over the fin surface and has a direct impact on the performance of your fins and board. Middle fins are always symmetrical and convex on both sides (50/50) for even distribution and stability, while outside fins are usually convex on the outside face and flat or curved on the inside. A flat inside face creates a solid balance of control, speed, and playfulness, while a curved or concave inside face maximizes lift with minimal drag, ideal for speed generation and fluidity.
[0034] FIG. 2 shows the side view of the reference fin and Spinfins at a 1:1 scale. It is clear that both fins have a similar base but the depth is very different. The difference in depth is the major factor for the Spinfins to have a smaller drag coefficient than the reference fin.
[0035] FIG. 3A shows the side view of the side Spinfins. The contour of the fin is defined as the line that creates a close surface from the leading edge to the trailing edge by passing through the tip.
[0036] FIG. 3B shows that iri the vertical direction of the side Spinfins has a concave (inside) and/or convex (outside) curvature in the vertical direction that does not exist for the reference fin. The curvature in the vertical direction is between 0.5-10 degrees and is defined by the line joining the fiat curve of the base with the point at the tip of the fin.
[0037] FIG. 3C shows the isometric view of the side Spinfins and the cant angle is shown in the figure. The cant angle is defined as the angle between the chord line and the line joining the chord line to the apex of the fin.
[0038] FIG. 3D shows the top view of the side Spinfins and helps to show the concave curvature of the fin in the vertical direction.
[0039] FIG. 4A shows the side view of the center Spinfins. Basically, the center fin was defined as two side Spinfins connected on their concave side (outside).
[0040] FIG. 4B shows that in the vertical direction of the center Spinfins has two concave surfaces and a cant angle defined as the angle made by a line connecting the chord of the fin to the apex of the fin.
[0041] FIG. 4C shows the isometric view of the center Spinfins.
[0042] FIG. 4D shows the top view of the center Spinfins and helps to show the two concave curvature of the fin in the vertical direction.
[0043] FIG. 5A-5C shows a cut of the side Spinfins in order to more clearly indicate the angle of twist about the vertical direction. The angle of twist is defined as the rotation of the Spinfins about its vertical direction. Values for the angle of twist are relatively small and should never exceed 15 degrees.
[0044] FIG. 6 shows the drag coefficient C.sub.d in the flow direction (x-direction) versus different angle of attack for the Reference and Spinfins. The figure indicates the resistance coefficient of the fin to move in the direction of the flow when the angle of attack varies between 0 to 90 degrees. The angle of attack is defined as the angle between the chord of the fin foil and the direction of the flow. The chord is the imaginary straight line connecting the leading edge e to the trailing edge.
[0045] FIG. 7 shows the lift coefficient C.sub.L in the flow direction versus different angle of attack. For a hydrofoil the lift is defined as the force perpendicular the inside/outside of the fin that is produced by the motion of the fin in the fluid. The higher the lift coefficient, the more effective is the fin to generate lateral force.
[0046] FIG. 8 shows the drag coefficient C.sub.L/C.sub.d in the flow direction versus different angle of attack. The ratio C.sub.L/C.sub.d is an indication of the fin efficiency.
