WO2013071329A1

WO2013071329A1 - Watercraft fin

Info

Publication number: WO2013071329A1
Application number: PCT/AU2011/001469
Authority: WO
Inventors: Courtney James POTTER
Original assignee: 3Dfins Pty Ltd
Priority date: 2011-11-14
Filing date: 2011-11-14
Publication date: 2013-05-23

Abstract

A watercraft fin including a leading foil, an inner foil and an outer foil, the leading foil, the inner foil and the outer foil having proximal ends for attachment to a watercraft and distal ends, the inner foil and outer foil being integrally formed at the distal ends to define a curved outer portion, and the leading foil being integrally formed with the curved outer portion at its distal end, and wherein the leading foil, the inner foil and the outer foil each have a nose and a tail, and the tail of the leading foil is located forward of the nose of the inner foil and outer foil.

Description

WATERCRAFT FIN

FIELD OF THE INVENTION

The present invention relates to a fin for a watercraft and in particular a fin for a surfboard.

BACKGROUND TO THE INVENTION

The Applicant previously disclosed a unique fin design in Australian Patent Application No 2009214814. For ease of explanation the contents of that application are incorporated herein by reference.

Prior to the earlier application it was common to use one or more fins on the underside or bottom of a surfboard. These fins provided the stability for the board rider, and still to this day are usually one or more single swept back foil(s). Fin designers traded manoeuvrability with speed in the design of these fins.

Watercraft speed and maneuverability depend on a variety of characteristics, including the craft and the attachments to that craft, principally fins. The principles of hydrodynamics involve the study of fluid or water past structures, such as occurs when the fin is attached to a watercraft and used in water.

Modern surfboards generally have 3 or 4 singular foil individual fins attached to the bottom of the surfboard. They are positioned with two fins on the outer edges of the surfboard and a middle fin(s) located behind and centrally between the two outer fins at a distance so as to not come into contact with the wake from the other fins.

The utilisation and placement of these single foil fins is still the accepted practice to this day. While the angle of curvature of the foil, and the size of the foil may be altered and accepted as good fin design, any departure from this conventional design is considered folly.

Contrary to this conventional thinking the Applicant developed the unique design disclosed in the earlier application which provided considerable improvements over the standard design. The invention included three smaller foils that are grouped together in place of the singular foil and fin located on the outer edges of the surfboard. The unique concept of three foils being integrally formed allowed for improved manoeuvrability with a smaller foil, which was contrary to conventional teachings. The design also allowed for greater speed. Again it was not expected with conventional designs for a fin to provide both improved manoeuvrability and speed. For example, the design of a conventional surfboard is ultimately a compromise between speed and maneuverability as a surfer moves through the surf. Typically, large fins tend to provide greater control but at a cost of increased drag and as a consequence reducing the top speed of the board. Increasing competition and professionalism in the sport of surfing has led to a desire for improved equipment performance.

While the applicants earlier design is a generational improvement over current conventional single foil fins, the applicant has discovered that the design of the fin was itself impeding the performance of the fin. That is whilst the earlier design is still markedly better then conventional fins, it is the design and performance of the fin itself which limits the fin.

As noted above modern conventional surfboards have 3 or 4 singular fins attached in a fixed figure configuration to the bottom of the surfboard. They are positioned so that each fin does not come into contact with the wake from the other fins as exemplified in Figure 1 .

With such an arrangement, a surfer who has 'caught a wave' and is in the process of propelling the board through the water feels the effects of the physics of fluid mechanics which dictate that the so called 'attached laminar fluid flow' around either side of each of the fins occurs following the Coanda effect during this linear motion.

Unlike conventional boards that had the fins spaced apart to avoid the wake, the applicants prior invention which adopted three integrally formed foils, resulted in the rear foils coming into direct contact with the wake of the forward foils. This can be seen in Figure 3. That is whilst conventional surfboards had the fins spaced widely apart to avoid any wake, the applicants prior invention was not so designed and thus the design was in itself impeding performance.

It is therefore desirable to further improve the performance of the applicants prior invention. SUMMARY OF THE INVENTION

In a broad form, there is provided a fin for a surfboard or other watercraft, including three individual foils with the individual foils positioned so that the leading edge of the rear foil is situated behind the rear edge of the leading foil.

This foil arrangement assists to control, realign and utilize the vortices and turbulence created as a foil member passes through the water during varying angles of attack of the surfboard, and reduces drag thereby increasing the speed of the surfboard.

The foil arrangement of the present invention reactivates the turbulent water by drawing the turbulent flow from the leading foil into the path of the rear foils and creates an even flow over the rear foils, utilizing the canola effect of water passing faster over the rear fins, increasing the speed of the surfboard.

The smaller individual foils grouped together provide greater drive and maneuverability, while maintaining hold and grip in the water, that is usually sacrificed when reducing the size of a singular foil.

In one aspect the present invention provides a watercraft fin including a leading foil, an inner foil and an outer foil, the leading foil, the inner foil and the outer foil having proximal ends for attachment to a watercraft and distal ends, the inner foil and outer foil being integrally formed at the distal ends to define a curved outer portion, and the leading foil being integrally formed with the curved outer portion at its distal end, and wherein the leading foil, the inner foil and the outer foil each have a nose and a tail, and the tail of the leading foil is located forward of the nose of the inner foil and outer foil.

In another aspect the present invention provides a fin for a watercraft including

a leading foil having a leading foil tail ;

an inner foil having an inner foil nose; and

an outer foil having an outer foil nose;

wherein the leading foil, inner foil and outer foil chord lines are all substantially parallel, and the leading foil tail is located forward of the inner foil nose and outer foil nose.

If a series of lines was to join the inner foil nose, outer foil nose and leading foil tail then these lines would define a triangle. Preferably the angle formed by the lines at the leading foil tail is between 55° to 57° the angle formed by the lines at the inner foil nose is between 90° to 92° and the angle formed by the lines at the outer foil nose is between 33° to 35°.

Ideally the angle formed at the leading foil tail is about 56° the angle formed at the inner foil nose is about 89° and the angle formed at the outer foil nose is about 35°.

In a preferred arrangement the distance between the leading foil tail and inner foil nose is about 31 to 35 mm, the distance between the leading foil tail and outer foil nose is about 62 to 64 mm, and the distance between the inner foil nose and outer foil nose is about 50 to 54 mm.

Ideally the distance between the leading foil tail and inner foil nose is about 34 to 35 mm, the distance between the leading foil tail and outer foil nose is about 63 to 64 mm, and the distance between the inner foil nose and outer foil nose is about 52 to53 mm.

In still a further aspect the present invention provides a watercraft with a bottom including at least three fins on the bottom, the three fins comprising a leading fin having a leading foil tail, an inner fin having an inner foil nose, and an outer fin having an outer fin nose,

wherein the leading fin, inner fin and outer fin chord lines are all substantially parallel, and the leading fin tail is located forward of the inner fin nose and outer fin nose.

In yet another aspect the present invention provides a watercraft with a bottom including at least three fins on the bottom, the three fins comprising

a leading fin having a leading fin tail;

an inner fin having an inner fin nose; and

an outer fin having an outer fin nose;

In yet a further aspect the present invention provides a watercraft, such as a surfboard for example, with a bottom including provision on the bottom for at least a leading fin having a leading foil tail, an inner fin having an inner foil nose, and an outer fin having an outer fin nose, wherein if fins were attached to the bottom the leading fin, inner fin and outer fin chord lines would all be substantially parallel, and the leading fin tail would be located forward of the inner fin nose and outer fin nose.

The placement of the fins in the present invention follows the same arrangement as the placement of the foils of the preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

An illustrative embodiment of the present invention will now be described with reference to the accompanying figures. Further features and advantages of the invention will also be apparent from the accompanying description.

Figure 1 shows a bottom view of a surfboard utilising conventional fin arrangement of a modern surfboard and showing the dynamics of water passing the fin showing the Coanda effect and laminar fluid flow.

Figures 2 and 3 show the foil arrangement of the applicants prior application.

Figure 4 shows the Coanda effect and laminar fluid flow of water over the foils of the applicants prior application.

Figure 5 shows the foil arrangement of preferred arrangement of the present invention.

Figure 6 shows the Coanda effect and laminar fluid flow of water over the foils of the present invention.

Figure 7 shows the triangle formation of spacing between foils in the preferred arrangement of the present invention.

Figure 8 shows a preferred arrangement of the foils.

Figure 9 shows the turning radius of conventional fins and also the turning radius of foils of the present invention.

Figure 10 shows the improved water flow of the present invention and applicants prior invention.

Figure 1 1 shows the three foiled fins mounted on a body board, kiteboard and wakeboard.

Figure 12 shows a surfboard with fins mounted in the arrangement of the present invention. DESCRIPTION OF PREFERRED EMBODIMENT

The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention. The present invention is not intended to be limited to the embodiments shown, but is to be construed at the widest scope consistent with the principles and features disclosed herein.

The Applicants disclosed in their prior application a single fin which comprised three foils arranged as shown in Figure 2. As can be seen the fin included three separate foil sections 1 , 2, 3 joined together to form an integral unit. For simplicity these foils are an inner foil 2, an outer foil 3, and a leading foil 1 .

In the prior application the foils were arranged such that the leading foil 1 when mounted on a surfboard was mounted forward of the inner 2 and outer 3 foils. This can best be seen in Figure 3. In Figure 3 it can be clearly seen that the leading foil 1 is mounted forward of the inner foil 2, and that the nose 4 of the inner foil 2 is located forward of the tail 5 of the leading foil 1 .

The foil arrangement of the Applicants prior invention resulted in water flowing about the foils as shown in Figure 4. As can be seen the laminar flow of water combined with the colander effect resulted in turbulent water flowing from the tail of each foil. In particular it can be seen that the spacing of the foils means that the inner 2 and outer 3 foils are unable to re-align the vortices and turbulent water flow coming from the leading foil 1 . This reduces the effectiveness of the inner 2 and outer 3 foils as they do not enjoy the benefit of the laminar flow of water that the leading foil 1 receives.

The present invention is the positioning and arrangement of the three foils 1 , 2, 3, to form a single fin in such a way as to utilize the turbulence created in the wake of a fin and to allow lateral water flow (created in modern surfboard maneuvers) to pass between the foils. The invention includes three smaller foils that are grouped together in place of the singular fin located on the left and right outer edges of the surfboard.

The principles of hydrodynamics show vortices (and turbulences) flow in the wake of a structure, such as a fin in water. These vortices are staggered and the foil arrangement of the present invention mimics this stagger in order for the inner 2 and outer 3 foils to come into direct contact with the water flowing from the leading foil 1 . The precise spacing of the foils is important to be able to draw the water from the leading foil 1 into the inner 2 and outer 3 foils.

The preferred spacing arrangement is shown in Figure 5. The two sets of foils shown in Figure 5 represent fins to be placed on the left side of a surfboard and the right side of a surfboard. They are in effect mirror images of each other.

In the example of Figure 5, the leading foil 1 is 62 mm long, and both the inner 2 and outer 3 foils are 52 mm long. In this arrangement the inner foil nose 4 is spaced 34-35 mm from the leading foil tail 5. The outer foil nose 6 is spaced 63-64 mm from the leading foil tail 5, and the inner foil nose 4 and outer foil nose 6 are spaced 52-53 mm apart.

Ideally the chord line of each foil should all be parallel to ensure the optimum flow of the water. This also means that each foil has the same angle of attack as the surfboard moves through the water.

Further the chord line of the leading foil 1 should be approximately equidistant from the chord lines of the inner 2 and outer 3 foil chord lines. In the example of Figure 5 the distance between the chord line of the leading foil 1 and that of both rear foils 2,3 is about 20.7 mm.

An alternative embodiment is shown in Figure 8, in which the leading foil 1 is 62 mm long, and both the inner 2 and outer 3 foils are 52 mm long. In this arrangement the inner foil nose 4 is spaced 31 -35 mm from the leading foil tail 5. The outer foil nose 6 is spaced 62-64 mm from the leading foil tail 5, and the inner foil nose 4 and outer foil nose 6 are spaced 50-54 mm apart.

The location of the leading foil tail 5, inner foil nose 4, and outer foil nose 6, can map a triangle which best defines the location of the respective foils. This triangle can be seen in Figure 7. Provided that the leading foil tail 5 is located at point 8, the inner foil nose 4 is located at point 7, the outer foil nose 6 is located at point 9, and the chord lines for each foil are substantially parallel, then the arrangement of the present invention provides an improved performance.

Figure 7a shows the preferred angles which the applicant believes provides the best performance. It can be seen that the angle formed at point 8 is about 55°, the angle at point 7 about 34°, and the angle at point 9 about 90°.

Testing has shown however that favourable results can also be achieved with the angle at point 8 ranging from 53° to 57°, the angle at point 7 ranging from 32° to 35°, and the angle at point 9 ranging from 88° to 92°.

The foil arrangement and positioning is in such a way that the turbulence and vortices created by the lamina separation of the water from the leading foil 1 are drawn into the inner foil 2 and outer foil 3 (or rear foils 2,3) path and this contact with the leading edge of the rear foil 2,3 results in the realignment of the water into an even flow as is shown in Figure 6.

The result is a faster flow of the water over the rear foils 2,3, thereby reducing the drag created by the turbulent water flow and creating more energy that propels the surfboard faster through the water.

The distance between the tail 5 of the leading foil 1 and the nose 4 of the rear foils 2,3 has the additional purpose of allowing the passing of sideways water flow between the foils relatively unhindered (which occurs when the surfboard moves on a lateral plane), resulting in greater maneuverability of the surfboard or watercraft. This is demonstrated in Figure 10. Figure 10a shows the ability for the water flow to pass between the foils allowing for greater interplay between the foils. This can be contrasted with Figure 10b which shows the arrangement of the applicants prior invention. In Figure 10b it can be seen that the water does not flow easily between the foils, and thus the spacing of the foils blocks the water flow and restricts maneuverability. That is the arrangement of the applicants prior invention in which the rear edge of the leading foil overlapped the leading edge of the rear foils inhibits the water flow passing sideways between the foils during different angles of attack, and prohibits the lateral movement of water between the foils therefore inhibiting maneuverability of the surfboard.

The overlapping of the rear foils 2,3 to one another, and the overall smaller size of each individual foil also results in a smaller combined side profile surface area than the standard surfboard single fin allowing for less resistance to be met when turning the surfboard or maneuvering laterally. This is demonstrated in Figure 9. Figure 9a shows the turning radius of a conventional single fin, whereas Figure 9b shows the turning radius of the foils of the present invention. The smaller individual fins also provide for a smaller turning radius (relative to that of a standard fin) given the position of the fins relative to one another. It can thus be seen that the present invention enables a much tighter turning radius then the conventional fin allowing for modern surfing maneuvers to be completed more successfully.

The primary objective of conventional fin systems and arrangements is to avoid contact with turbulent water flow and the fins are placed laterally apart to ensure each fin always receives clean water. The present invention actually utilizes the turbulent water to effectively re-energise the water and gain improved performance.

Modern surfing results in a surfboard turning on a 360 degree axis and through all angles of attack, with such maneuvers speed is crucial. With the conventional surfboard fin design the turbulent water created flows out under the rear of the surfboard, with the turbulent water creating drag and reducing the speed of the surfboard.

This invention is the unique arrangement and the positioning of each of the rear foils of the fin in relation to the leading foil so that the rear foil directly contacts with the turbulence and utilizes the energy so created. This is achieved by positioning the leading edges of the rear fins behind (and with a space between) the rear edge of the leading fin.

Flow dynamics determines water flowing over the curved surface of a foil (such as a fin) accelerates and therefore is an energized flow. This flow results in turbulence which then trails the rear edge of each fin. The present invention is unique in that it seeks to control the turbulence created once the water flow passes over the surface of the fins, rather than the conventional practice of avoiding the turbulence.

The disclosure above has focused on the improvements over the applicants prior invention wherein the three foils are integrally formed to create the improved fin. However, the applicants discovery can also be used to arrange conventional fins on a surfboard as exemplified in Figure 12 to achieve an improved performance.

In this arrangement the surfboard 10 can include one or more 'sets' of fins, whereby each set is arranged as disclosed herein. That is, each set includes a leading fin 1 1 , inner fin 12, and outer fin 13. The fins are arranged such that the tail 14 of the leading fin 1 1 is mounted forward of the nose 15 of the inner fin 12. The relative positions of the inner fin nose 15, outer fin nose 16 and leading fin tail 14, can form a triangle and should be set out as shown in Figure 7. The result would not be dissimilar to the arrangement shown in Figure 5, and the chord line for each fin should all be substantially parallel.

Due to the improved performance provided the actual size of the fins can be reduced from that which would have been used if a single fin was employed. The size of a fin is usually dictated by the size of a surfer and to a less extent the size of the wave. A larger surfer usually employs a larger fin as this allows the larger surfer to apply the extra pressure without the surfboard spinning out. In extreme size surf a smaller fin is desired for less drag and less lift.

A typically or normal fin size for a small to average size surfer using current conventional arrangements is a height of between 1 14 mm - 125 mm and a base length of between 109 mm - 1 15 mm.

By using the present invention the Applicant has found that the fin size can be reduced to between about 94 mm and 1 14 mm, and with a base between 42 mm - 72 mm, with the optimum size for the fin being about 104 mm for most surfing conditions and averaged sized surfers. This new arrangement allows a larger surfer to ride the smaller fins without sacrificing the control or grip normally provided by larger fins, whilst also having the added advantage of less drag. Thus using the new arrangement the overall size of the fin can be reduced with sacrificing performance.

The reduced fin size also allows for Naca foils to be used in the construction of the fin. Conventional fins are typically constructed of fibre glass (carbon fibre) and varying layers of materials (foam cores, aluminium fibre) to maintain Strength and flex. The process is very wasteful and un-recycleable, and the environmental foot print is large due to the many process and complex materials and processes used. The use of Naca foils is advantageous as they have a more efficient lift to drag ratio as compared to conventional fins made of fibre glass. Previously the surfing industry has avoided using Naca foils as their surface area has been considered inadequate to provide the stability that a surfer requires. The present invention in allowing for smaller foils or fins to be used means that Naca foils can now be used. Some embodiments may however still use conventional material for aesthetic reasons and because surfers are accustomed to the feel.

Normal fins are typically made up of Fibre glass(carbon fibre) and varying layers of materials(foam cores, aluminium fibre )to maintain Strength and flex, the process is very wasteful and un-recycleable and the environmental foot print is large due to the many process and complex materials and processes.

Due to the shape and the size (smaller fins) the materials used can vary more than normal fins, Flex is not necessary for this design therefore a larger range of materials can be used such as: Polycarbon (PC is a 100% Recyclable plastic, Currently used in our design), Aluminium, Wood.

While the present invention has been explained in relation to a fin for a surfboard, it will be understood that the fin could be used on other watercraft. For example, a bodyboard, kiteboard or wakeboard as shown in Figure 1 1 .

Reference throughout this specification to "one" or "an" embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment.

Furthermore, the particular features, structures, or characteristics may be combined in a suitable manner in one or more combinations. It will be appreciated that persons skilled in the art could implement the present invention in different ways to the one described above, and variations may be reduced without departing from its spirit and scope.

Any discussion or documents, devices, acts or knowledge in this specification is included to explain the context of the invention. It should not be taken as an omission that any of the material forms part of the prior art base or the common general knowledge in the relevant art, in any country, on or before the filing date of the patent application to which the present specification pertains.

Claims

CLAIMS:

1 . A watercraft fin including a leading foil, an inner foil and an outer foil, the leading foil, the inner foil and the outer foil having proximal ends for attachment to a watercraft and distal ends, the inner foil and outer foil being integrally formed at the distal ends to define a curved outer portion, and the leading foil being integrally formed with the curved outer portion at its distal end, and wherein the leading foil, the inner foil and the outer foil each have a nose and a tail, and the tail of the leading foil is located forward of the nose of the inner foil and outer foil.

2. A fin for a watercraft including

a leading foil having a leading foil tail;

an inner foil having an inner foil nose; and

an outer foil having an outer foil nose;

3. A fin for a watercraft as claimed in claim 1 or claim 2 wherein a series of lines joining the inner foil nose, outer foil nose and leading foil tail define a triangle, and wherein the angle formed by the lines at the leading foil tail is between 53° to 57°, the angle formed by the lines at the inner foil nose is between 88° to 92°, and the angle formed by the lines at the outer foil nose is between 32° to 35°.

4. A fin as claimed in claim 3 wherein the angle formed at the leading foil tail is about 55°, the angle formed at the inner foil nose is about 90°, and the angle formed at the outer foil nose is about 34°.

5. A fin as claimed in any preceding claim wherein the distance between the leading foil tail and inner foil nose is about 31 to 35 mm, the distance between the leading foil tail and outer foil nose is about 62 to 64 mm, and the distance between the inner foil nose and outer foil nose is about 50 to 54 mm.

6. A fin as claimed in claim 5 wherein the distance between the leading foil tail and inner foil nose is about 34 to 35 mm, the distance between the leading foil tail and outer foil nose is about 63 to 64 mm, and the distance between the inner foil nose and outer foil nose is about 52 to53 mm.

7. A watercraft with a bottom including at least three fins on the bottom, the three fins comprising a leading fin having a leading foil tail, an inner fin having an inner foil nose, and an outer fin having an outer fin nose,

8. A watercraft with a bottom including at least three fins on the bottom, the three fins comprising

a leading fin having a leading fin tail ;

an inner fin having an inner fin nose; and

an outer fin having an outer fin nose;

9. A watercraft as claimed in claim 7 or claim 8 wherein a series of lines joining the inner fin nose, outer fin nose and leading fin tail define a triangle, and wherein the angle formed by the lines at the leading fin tail is between 53° to 57°, the angle formed by the lines at the inner fin nose is between 88° to 92°, and the angle formed by the lines at the outer fin nose is between 32 ° to 35 °.

10. A watercraft as claimed in claim 9 wherein the angle formed at the leading fin tail is about 55°, the angle formed at the inner fin nose is about 90°, and the angle formed at the outer fin nose is about 34°.

1 1 . A watercraft as claimed in any one of claims 7 to 10 wherein the distance between the leading fin tail and inner fin nose is about 31 to 35 mm, the distance between the leading fin tail and outer fin nose is about 62 to 64 mm, and the distance between the inner fin nose and outer fin nose is about 50 to 54 mm.

12. A watercraft as claimed in claim 1 1 wherein the distance between the leading fin tail and inner fin nose is about 34 to 35 mm, the distance between the leading fin tail and outer fin nose is about 63 to 64 mm, and the distance between the inner fin nose and outer fin nose is about 52 to 53 mm.

13. A watercraft with a bottom including provision on the bottom for at least a leading fin having a leading foil tail, an inner fin having an inner foil nose, and an outer fin having an outer fin nose,

wherein if fins were attached to the bottom the leading fin, inner fin and outer fin chord lines would all be substantially parallel, and the leading fin tail would be located forward of the inner fin nose and outer fin nose.

14. A fin for a watercraft substantially as hereinbefore described.