AU2006248818B2

AU2006248818B2 - Fin unit with elastic attachment system on an underside of a marine apparatus

Info

Publication number: AU2006248818B2
Application number: AU2006248818A
Authority: AU
Inventors: Hugo Heesterman
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-05-18
Filing date: 2006-05-18
Publication date: 2012-01-19
Anticipated expiration: 2026-05-18
Also published as: EP1893475A1; FR2885875A1; FR2885875B1; WO2006123054A1; BRPI0609886A2; ZA200710485B; US20080268730A1; AU2006248818A1

Abstract

The invention relates to a fin unit (2) with elastic attachment system on an underside (1) of a marine apparatus, such as a wind surf, kite surf, fly surf, wakeboard, knee board and particularly a surfboard. The fin in the mounting thereof is partially made to self-align in the flow of liquid medium with the aim of avoiding the hydrodynamic stall caused by the passage of high turbulence and/or large lateral movements caused by the surfer in extreme motion. The possibility for self-orientation is due to three fundamental parameters which are: the type of elasticity of the attachment system (3-4-5-27), the forward position of the centre of gravity G towards the leading edge (15) and the form of the root profile (9) of the fin (2) which has a thickening (7) of the trailing edge thereof.

Description

1 Fin unit with elastic attachment system on the underside of a marine apparatus The present invention relates to a fin unit with an elastic attachment system on the underside of a marine apparatus, such as a windsurfing board, a kite surfing 5 board, fly surfing board, wake board, a kneeboard and particularly a surfboard. Surfboards are usually equipped with one or with several fins, more commonly three, fixed at the tail of the board, on the careen (the lower surface of the board). Two methods of fixing exist, one entails bonding the fins on the board to make them interdependent, the other entails having removable and interchangeable fins via a box 10 or an insert of fixture incorporated in the board. The traditional fins are generally manufactured using a plate made up of a multitude of fiberglass layers and resin, machined or shaped by hand. Then they are made interdependent with the board by bonding with fiberglass fabrics, unidirectional fibre and resin. 15 This mode of fixing makes it possible to establish at the root a peripheral fillet to improve the hydrodynamic characteristics at the base of the fins. On the other hand, the presence of fixed fins on the board during manufacture involves an increased duration of the finishing operation and thus the cost of labour, as well as an increase in the weight and a reduction of the quality of the board finish 20 surrounding the position of the fins. For the last ten years, many companies have become involved in the manufacture of removable fin systems because they have multiple advantages, on one hand for surfers whom according to the type of sport use several types of fins with the same board. On the other hand, board manufacturers are seeking speedy 25 installation of the fins and a less cumbersome and an easier storage of the boards in the warehouse or during transportation. The boards are most commonly equipped with fins made of thermoplastic material reinforced with glass powder. They are heavy and present weak mechanical properties compared with traditional fins when they are submitted to a bending stress. 30 To obtain optimal performances in a wave, during the various stages of manufacture of a board, the shaper pays very detailed attention to the distribution of volume and on its balance compared to the board's widest point. SPEC-817035.doc 2 Despite everything, when the board is equipped with its fins, the weight of the fins induces a shift backwards of the centre of gravity compared to the required optimal position. Moreover, disappearance of the fillet, represented by an amount of resin at the 5 base of the fin, reduces the hydrodynamic performances while generating an inopportune stall of the fluid and a loss of control of the board by the surfer in certain configurations. Generally the fins are maintained in position on the board by a system including one or more screws which fix them in place in the inserts, as described in 10 Patent No. FR 2691943. That forces the surfer to use a specific tool in order to mount/dismount the fins, representing certain difficulties when one is on a beach. On certain marketed systems, a frequent assembly/disassembly of the fin or a too high tightening torque of the screw can damage the threading in the plastic insert, and even deteriorate the hexagonal head of the screw. This dysfunction can involve a 15 fin loss or render assembling/disassembling it from the board impossible. Other disadvantages have been identified in existing systems, such as the possibility of perforating the board's fibre reinforcement during fin assembly/disassembly because of a front/back swing. As well as the importance of board repair after insert's tear off in the case of violent impact, the shape and the 20 weight of the used insert of fixture and its mode of embedding in the board. Moreover the stiffness of fin/board assembly mounting causes, in extreme configuration of the convolutions practiced by the surfer, the formation of vortex and vibrations. A reference herein to a patent document or other matter which is given as prior 25 art is not to be taken as an admission that the document or matter was known or that the information it contains was part of the common general knowledge as at the priority date of any of the claims. According to an aspect of the present invention, there is provided a removable fin unit including a fin having a profile and a root; and an elastic fastener for fastening 30 the fin to a careen of a marine apparatus wherein the fin is partially self directional in its progression in a fluid environment in order to retard a hydrodynamic stall while receiving large turbulences and/or the lateral movements applied by a surfer in motion, by means of an elastic means of fastening providing partial mobility of the fin SPEC-817035doc 3 around a vertical axis Oz in yaw Mz and around a horizontal axis 0,, in roll Mx combined with a centre of gravity G of the fin being in front of 0z axis. An aspect of the invention is to facilitate the control of the board by a surfer by having removable fins whose constitution, shape and assembly on the board, allow to 5 obtain on one hand, an improvement of the hydrodynamic efficiency by reducing the formation of vortexes/vibrations and on the other hand, to increase the range of evolution in the waves in a marine environment. This goal is reached by making the fin semi articulated or partially self directional in its fluid environment, in order to retard the hydrodynamic stall caused by 10 the crossing of high turbulences and/or by the strong lateral movements applied by the surfer in motion, providing partial mobility of the fin about an axis Oz in yaw during Mz and abut on axis Ox in role Mx, due to an elastic means of fastening combined with the forward position of the centre of gravity G toward the leading edge and the shape of the root profile of the fin. 15 The fin unit with elastic attachment system in accordance with the present invention, presents certain advantages. The fin is mounted semi articulated on the board. In addition it improves the hydrodynamic performance and, it improves the service life of the whole assembly with respect to mechanical shocks or hydrodynamic fluctuations, which are absorbed by the elastic attachment system. 20 According to another characteristic of the invention, the shape of the fin profile out of the root includes a thickening of the trailing edge to a value equal or less than the thickness of the master couple located at approximately 25% of the airfoil chord, the said thickening being built on a height H of value at least equal to that of the master couple. 25 According to another characteristic of the invention, all the fastening means are represented by an insert taken in the mass of the hull containing an elastic matter coating a sleeve to imprison at least a tenon protruding from the base of the fin, which together allow a partial elastic mobility of the fin around the axes Oz and Ox. According to another characteristic of the invention, the fin assembled with its 30 fastening means is able to move angularly (Al and AJ), in the case of excessive pressure stresses of hydrodynamic nature AP, about vertical axis Oz in yaw Mz and about longitudinal axis O, in roll Mx According to another characteristic of the invention, the fin, in the case of extreme evolutions or important variations speed AV of great incidence i, effect of SPEC-817035.doc 4 motion or gust, generate strong variations of thrust AP, is self-adjustable in incidence by the fact that the tenon/insert assembly is elastic and that forces of inertia applied to the centre of gravity G and hydrodynamic forces applied to the centre of pressure 0', depend on the swirling effects of induced trails tm and on the root turbulences te, 5 induce yawing moments M, and rolling movements Mx which counter act the effect of gust by angular variations Al and AJ. The invention is described hereafter using examples and references to joined illustrations, in which: - Figure 1 is a side plan view representing the principal components 10 between fins and careens. - Figure 2 is a cross sectional view of drawing 1 showing the shape of the tenon profile and the insert, - Figure 3 illustrates the fin in its work configuration in the fluid with its associated turbulent flows. 15 - Figure 4 is a bottom plan view of the board equipped with three fins. - Figure 5 is a rear view of the board. - Figure 6 is a perspective view of the fin/insert assembly. - Figure 7 is a rear view of the fin considering the trailing edge. - Figure 8 illustrates different shapes and surface conditions of tenons. 20 - Figure 9 is a perspective view of the insert embedded in the board. - Figure 10 is a cross sectional view of the insert including its angular jig fitted in the board. Figure 1 illustrates the whole assembly of the fin (2) on the careen (1) or lower surface of the board. 25 The fin is equipped with at least one tenon (3) which is introduced into an insert (5) bonded to the careen (1) including an elastic matter (4) coating if necessary a sleeve (27) in order to hold and lock the tenon after its insertion in the housing. The mechanical unit thus defined represents an elastic means of fastening (3 4-5-27). They bring a partial mobility of the fin around the Oz axis with yawing moment 30 M2 and around Ox axis with rolling moment Mx. Figure 2 represents, a cross sectional top view of, the shape of the insert (5), the shape of the tenon (3) and the shape of the root profile (9) of the fin (2). The root profile includes a thickening (7) of the trailing edge (8) of a value equal or lower than the maximum cross section thickness situated at approximately SPEC-817035.doc 5 25% of the airfoil cord. This thickening (7) is built on a height H of value at least equal to that of the maximum cross section Mc. The fin equipped with tenon (3) is manufactured in such a way that it can float in water. It is composed of a profiled core (16) made of very light material covered 5 with a skin (17) of great strength with a leading edge (15) reinforced by successive layers. The fin is fitted with a ballast (6) for two reasons. Namely, the first; in order to position the fin centre of gravity G close to the root (9) and in front of Oz axis, the second; in order to adjust the Eigen frequencies Hx and Hz around the Ox and Oz axes. 10 Figure 3, explains how the fin (2) reacts when it is submitted to more or less laminar and fluctuating flows. Indeed, for a given speed V and an angle of incidence i the fin is subjected to a lift P and a drag T whose centre of action 0' is located at the back of the Oy fastener axis. For an angle of incidence close to stall we observe an amplification of marginal 15 tip vortex tm, an amplification of root turbulences te and of vibrations. These can be rather destructive when they are close to the natural frequencies HP of the assembly in a turbulent fluid environment. Various disadvantages are ameliorated while making the fin reactive and partially self directional while exploiting three fundamental parameters. They are: 20 - The elastic means for fastening (3-4-5-27), which depending on the grade of elasticity, determines the importance of the angular displacement Ai and Aj around Ox - Oy axis. Thus a strong variation of lift AP, caused by a strong variation of speed AV, swirl or gust, will be limited by the rotation of the fin in the way of angle of attack reduction by considering that action centre 0' is located at the rear of Oz axis. 25 - The form of the root (9) profile of the fin, whose trailing edge (8) includes a thickening (7) as shown in Figure 1 and 2. At a strong variation of lift AP, this shape limits the stall due to the imperfections of the fin/careens surfaces junction and thus limit the displacement of the action centre towards the leading edge of the fin. 30 - The position of the centre of gravity G that will be generally adjusted via a ballast (6) so that the inertial forces bring back to Ox and Oy axis generate, during the increase of speed AV, a rotation of the fin in the way of incidence reduction. SPEC-817035.doc 6 It is under these conditions that the fin, in the case of an extreme motion or important variations of speed AV at great incidence, is self adjustable by the fact that the tenon (3)/insert (5) linkage is elastic and that inertial forces, applied at the centre of gravity G and that the hydrodynamic forces applied to the action centre 0', induce 5 yawing moments Mz and rolling moments Mx which reduce the gust effect by the angular variations Ai and Aj. The tenon (3), according to the mountings, can have a circular section or be rectangular or have a more or less elliptical section as shown in Figure 2. The fin can contain at its end a notch or a throttling (10) as to self position it in 10 its sleeve (27) during insertion and to be locked in at its end of travel on an elastic strip (28) or a spring ring of the circlips (20) type. The disassembly of the fin operates by pulling it along the Oz axis while pushing on a located point on the insert as to disengage the elastic strip or the pin from the tenon notch. The fin, in another type of arrangement can be locked in position by a cord (11) 15 fixed at the tenon end or on the root (9) of the fin. This cord crosses through the thickness of the board in order to be fixed and tended by a rubber band (12) located and fixed (13) in a slot (14) practiced in the deck of the board. The Figure 6 represents another type of arrangement according to which the fin (2) is attached to the careen (1) by two tenons (3a-3b) inserted in two mortises 20 (19a-19b) of a non elastic material. Each mortise includes inside one or more elastic matter rings (18a-18b) in such a way that the tenons, once introduced, are maintained by the radial pressure of the rings which allow however a light elastic displacement of the fin (around Ox and Oz axis) in the gap left between the diameter of the tenons and that of the mortises. 25 The Oz axis position is between the axis of the tenons (3a-3b). But in the case where we want to adjust Oz axis as close as possible to the tenon (3a) axis, it is enough to use rings with different elastic deformation under the same effort. It is the case in our assembly where the rings (18a) have a smaller modulus of elasticity, that is to say harder than the rings (18b). A difference of size or shape of the ring 30 contained in the mortises (19) before and back can produce the same effect with an identical modulus of elasticity. Figure 8 represents the use of various tenons. The tenon is a part brought back during the manufacture of the fin (2) whose material is either a stainless or titanium, or a composite. The tenon has on its outside a smooth or ridged or knurled SPEC-81703. doc 7 surface to strengthen the interaction of the assembly with the rings (18a-18b). There is a tubular cavity (22) where there is a flexible bond (23) of safety connecting one and the other of the two ends (24-25) of the tenon which in the event of rupture makes it possible to not lose the fin in the fluid environment. 5 The Figure 9 shows insert (5) assembled in the board. It is a kind of very hard material cage including outside protruding parts (26) for mooring and bonding in the careen (1). Inside the insert other protruding parts (29) are arranged to receive equipments allowing coupling with at least one tenon (3). This assembly, to ensure cost savings by reducing manufacture time and by 10 facilitating installation in the board, includes, as shown in Figure 10, an angular positioning jig (30) composed of three arms (31-32a-32b) each one provided with a pin (33). The arm (31) has a length greater than that of the arms (32a-32b) and is provided with at least a divisible pin (34) dimensioned and specified with the required angle (y). 15 This angle (y) is defined by the designer for the angular positioning of the lateral fins, and it defines its angular position of origin. Each ignition pin (34) represents an angular increment (Ay) of between 0,25" and 10, with regard to the precedent. During the lateral fins installation the designer must break one or more pins (34) in order to obtain the angle that he wishes to set for 20 the fin, given by the plane support of the pin (34) and the pins (33). With regard to the installation of the central fin, it is necessary to break all the pins (34) to obtain an angle of 00, given by the plane support generated by the three pins (33). In order to maintain the contact between the three pins and the careen surface, 25 the use of a weight on the insert may be necessary during its installation by bonding in the board. Once the inserts are installed on the board at the desired angle, a final grinding is carried out to level the insert with the careen of the board in order to eliminate all the protruding members, represented in the hatched part (35) on FIG 10. 30 In the case where the external surface of the equipped insert does not align itself exactly with that of the careen (1) or presents asperities, the clearances or the gaps between fin and careen will be filled by an elastic joint (21) bonded on the careen or at the base of the fin. SPEC-817035.doc 8 Where the terms "comprise", "comprises", "comprised" or "comprising" are used in this specification (including the claims) they are to be interpreted as specifying the presence of the stated features, integers, steps or components, but not precluding the presence of one or more other features, integers, steps or components, or group 5 thereto. SPEC-817035.doc

Claims

1. A removable fin unit including a fin having a profile and a root; and an elastic fastener for fastening the fin to a careen of a marine apparatus wherein the fin is partially self directional in its progression in a fluid environment in order to retard a 5 hydrodynamic stall while receiving large turbulences and/or the lateral movements applied by a surfer in motion, by means of an elastic means of fastening providing partial mobility of the fin around a vertical axis Oz in yaw Mz and around a horizontal axis 0, in roll Mx combined with a centre of gravity G of the fin being in front of Oz axis. 10

2. A removable fin unit according to claim 1, wherein the form of the profile of the fin out of root includes a thickening of the trailing edge of a value equal or lower than the maximum cross section thickness situated at approximately 25% of an airfoil cord, the said thickening being built on a height H of value at least equal to that of the maximum cross section. 15

3. A removable fin unit according to claim 1 or 2, wherein the elastic fastener comprises an insert embedded in the careen including an elastic matter coating a sleeve in order to hold at least a tenon out of root of the fin, which assembly allows a partial mobility of the fin around the vertical Oz axis and the horizontal Ox axis.

4. A removable fin unit according to any one of claims 1 to 3, wherein the fin 20 assembled with its elastic fastener is configured to have angular displacement (Ai and Aj), in the case of over lift pressure of hydrodynamic nature AP, around vertical axis Oz in yawing Mz and around longitudinal axis Ox in rolling Mx.

5. A removable fin unit according to any one of claims 1 to 4, wherein the fin equipped with tenon is manufactured in such a way that it can float in the water, and 25 is composed by a profiled core made of very light material covered with a skin of great strength with a leading edge reinforcement by successive layers, which includes a ballast to adjust the natural frequencies HP, to position the centre of gravity (G) of the fin close to the root and in front of the vertical Oz axis.

6. A removable fin unit according to any one of claims 1 to 5, wherein the fin, in 30 the case of motion or variations of speed AV at incidence i, swirl or gust, inducing a significant variation of lift AP, is self adjustable by the tenon/insert linkage being elastic and that inertial forces, applied at the centre of gravity G and that the hydrodynamic forces applied to the action centre 0', depending on the swirling effect SPEC-817035.doc 10 from induced drag tm, and root turbulence te, induce yawing moments Mz and rolling moments M, which reduce a gust effect by the angular variations Ai and Aj.

7. A removable fin unit according to claim 3, wherein the tenon is of circular section or rectangular or more or less elliptic, and the tenon contains a notch or a 5 throttling as to self position the tenon in the sleeve during insertion and to be locked in the end of travel on an elastic strip or a spring ring of circlips type.

8. A removable fin unit according to claim 3 or 7, wherein the fin is locked in position by a cord fixed at the tenon end or on the root of the fin, which cord crosses through the thickness of the board in order to be fixed and tended by a rubber band 10 located and fixed in a slot positioned in the deck of the board.

9. A removable fin unit according to claims 1 or 7, wherein the fin is attached to the careen by two tenons inserted in two mortises of a non elastic material, each mortise including one or more elastic matter rings such that the tenons are maintained by radial pressure, at the level of the throttling, which allow an elastic displacement of 15 the fin (around horizontal axes Ox and vertical axes Oz) in the gap left between the diameter of the tenons and that of the mortises.

10. A removable fin unit according to claim 9, wherein the elastic matter rings present different elastic deformations under the same load, due to a difference of modulus of elasticity and/or a difference of the shape of the elastic matter rings as to 20 position the vertical Oz axis as closer to a front tenon axis.

11. A removable fin unit according to claims 3 and 9, wherein the tenons are brought back during the manufacture of the fin and a material used is either metal stainless or titanium, or a composite, tenon including outside a smooth or ridged or knurled surface to strengthen the interaction of the assembly with the elastic matter 25 rings and including inside a tubular cavity where there is a flexible bond of safety connecting one and another of the two ends of the tenon which makes it possible not to lose the fin in the fluid environment in the event of rupture.

12. A removable fin unit according to claim 3, wherein the insert is a hard composite material cage including outside the protruding parts for the mooring and 30 the bonding in the careen and inside other protruding parts to receive equipments allowing the coupling with at least one tenon, the insert being configured for installation in the board with an angular positioning jig composed of three arms each arm provided with a pin, the said arm of length greater than that of arms is provided with at least a detachable pin having an angle (y). SPEC-817035 doc 11

13. A removable fin unit according to claim 2, wherein the fin includes at the root an elastic joint filling the clearances or the gaps between fin and careen.

14. A removable fin unit according to any one of the preceding claims, wherein the removable fin unit is installed and marine apparatus selected from a yaw of a 5 surfboard, a kite surfing board, a fly surfing board, a wake board, a knee board and windsurfing board.

15. A removable fin unit substantially as hereinbefore described with reference to any one of the embodiments shown in the drawings. 0 SPEC-817035 doc