GB2122561A - Sailboard - Google Patents

Abstract

A sailboard has a mast 18 joined by a universal joint to a board 12, an aerofoil shaped sail 22 having a line of symmetry as between upper and lower halves of the sail, a swivel joint 26 about which the sail is joined to the mast along a line substantially coincidental with the line of symmetry, swivel limiting means 40, 41 to limit the swivelling of the sail to approximately 180 DEG between an upright port tack position and an upright starboard tack position, the sail passing through a 90 DEG position intermediate these positions where the sail is substantially horizontal and provides lift for gliding, and a pair of holding bars 32, one for each of the port and starboard tack positions, for a user to support the sail and mast in respectively the port and starboard tack positions. <IMAGE>

Description

SPECIFICATION Improvements in sailboards This invention relates to sailboards or surfboards as they are sometimes called and in particular to a type of-sailboard which has the capability of gliding when sufficient forward momentum has been built up.

Sailboarding is a sport which has become extremely popular of recent times. Basically a sailboard consists of a board on which the sailor stands and he holds a wishbone which in turn supports the sail and mast, the sailer balancing his weight against the wind force acting on the sail. The mast is universally joined at its lower end to the board and the wishbone is symmetrical as seen in plan view so that the sailer can hold one or other side depending upon whether he is on a port or starboard tack. As with conventional sailing craft, therefore, the wind bears on one or other side of the sail depending upon the tack.

Extremely competent sailboard sailers have recently been able to achieve spectacular jumps by building up momentum in a sea where there are large waves and then by riding up over the top of a wave a spectacular jump can be achieved from the top of the wave. Obviously, the sailor needs to be attached to the board in some temporary fashion and foot-straps are provided on the surface of the board for this purpose.

The resulting jumps which can be achieved in this way are of a short duration and distance and so it is an object of this invention to provide a sailboard where the distance and duration of such jumps can be significantly increased.

According to the invention, there is provided a sailboard having a mast joined by a universal joint to a board, an aerofoil shaped sail having a line of symmetry as between upper and lower halves of the sail, a swivel joint about which the sail is joined to the mast along a line substantially coincidental with the line of symmetry, swivel limiting means to limit the swivelling of the sail to approximately 180 between an upright port tack position and an upright starboard tack position, the sail passing through a 90 position intermediate these positions where the sail is substantially horizontal and provides lift for gliding, and a pair of holding bars, one for each of the port and starboard tack positions, for a user to support the sail and mast in respectively the port and starboard tack positions.

In normal sailing conditions, this sailboard will function in a manner very similar to a conventional sailboard. Thus, although the sail is of aerofoil shape so that the wind is only designed to bear on it from one direction, the sailer uses his body weight to counter the force of the wind on one or other tack and he swivels the sail past the 90 intermediate position to the other tack position when he changes tack. However, once he has built up sufficient forward momentum, a gliding position can be achieved by quickly moving the sail up to the 90 intermediate position where the aerofoil shaped sail will act as a wing and allow the board to glide for a distance rather like a'hang-glider until the board lands again on the water.Gliding is therefore best initiated from the top of a wave when considerable forward momentum has been achieved.

The sail is of aerofoil shape and it is only designed for the wind to impinge on it in one direction. Therefore, the sail can be designed to provide the best aerofoil and does not have to be a compromise to allow the sail to drive the boat for either tack as does a convention sail. This means that the sail can be of normal sail cloth made up of a number of appropriately shaped panels or formed in one piece such as from a shaped film of synthethic plastics material and equally the sail material could be of relatively rigid material. Also the sail may be formed from a single layer of material or at least the forward part of the aerofoil can be formed from two spaced shaped layers of material. Further the sail may be provided with battens to assist in the shaping and/or stiffening of the sail.

The aerofoil shaped sail is of course akin to an aircraft wing and so the various tecnhiques which have been adopted in the design of such aerofoils can be used. In particular, the techniques of light weight with maintenance of high strength which have been used in designing hang gliders and steerable parchutes and in designing the ultralight-weight human powered aircraft can be used in the deisgn of the aerofoil shaped sails.

It is believed that the sail used in the sailboard of the invention will be capable of driving the sailboard during normal sailing faster than a conventional sailboard.

Preferably the sail has a leading edge which is either straight or rearwardly swept at an angle, for example, of up to 25 as conventional aircraft wings frequently are.

In order to increase the sail area for gliding, retractable wing tips may be provided at either end of the sail, that is to say, the top and bottom of the sail in the sailing as opposed to the gliding position. These wing tips can be retracted, e.g. hinged in or out, in the sailing position but once a gliding position is achieved, they can be opened manually by the sailer or automatically to increase the wing area for gliding. Also, when the sail is in the upright position, the upper wing tip could be opened automatically or manually, if desired, to increase sail area.

The mast of the board can be joined by means of a universal joint at its lower end to the board in a manner which is conventional for sailboards. The mast need not and indeed will not normally be as tall as conventional sailboard masts since it only needs to extend up to the symmetrical line or half height of the sail. At this point, the sail is joined to the mast in a manner which allows the sail to rotate through the required 180 between tacks and also allows the angle of the sail relative the board (as seen from above) to be varied to suit the apparent wind direction, e.g.

for close-haled, reaching and running conditions, and further allows the angle of the sail relative the horizontal (as seen from the side) to be varied to alter the centre of effort and so assist in steering the board as in conventional sailboards. By way of example, the sail can be joined to the mast by a swivel joint and a universal joint similar to the one used at the base of the mast in conventional sailboards.

Conveniently the swivel limiting means are in the form of hooks, yokes or abutments which engage with the mast so that swivelling of the sail beyond the 180 positions on port and starboard tacks is limited by the engagement of these means with the mast.

The holding bars will not be in the form of a wishbone, that is a pair of arcuate bars joined end to end and one on either side of the sail, as with conventional sailboards because the sailor will only ever support the sail by pulling in a direction away from the underside of the aerofoil shape. Therefore both holding bars will be on the same side of the sail, i.e. the underside of the aerofoil shape, and will be positioned one across each half of the sail. Thus one can then be grasped by the sailer when on the port tack and the other when the sail has been swivelled through 180 and grasped by the sailer on the other tack.

The invention will now be described, by way of example, with reference to the accompanying drawing which is a diagrammatic elevation of a sailboard according to the invention.

The sailboard 10 shown in the drawing comprises a largely conventional board 1 2 having a skeg 14 projecting downwardly from the underside of the board near the stern.

Upstanding from the top of the board is a mast 1 8 joined to the board by a universal joint 20.

The mast 1 8 supports a sail 22 which is symmetrical as between top and bottom halves about a line of symmetry 24. The sail is joined to the top of the mast by means of a joint 26 which includes a swivel joint and a universal joint similar to the joint 20 at the base of the mast. This enables the sail to turn about a substantially horizontal axis coincident with the line of symmetry 24. Also, the sail can rotate about the axis of the mast to allow the angle of attack of the sail to be adjusted to suit the direction of the apparent wind, e.g.

to change the sail from close-hauled through reaching to running conditions. Further, the centre of effort can be changes as in conventional sailboards by adjusting the tilt of the sail relative to the board; this is in the plane of drawing.

The luff of the sail is joined to a rigid spar 30 which is of a V-shape so giving a slightly swept back leading edge to the sail, the point of the V coinciding with the line 24. This spar 30 is of light weight material such as aluminium or carbon fibre reinforced composite material for strength. Joined to the spar 30 are holding bars 32 whose rear ends are joined to one another at the point 34 at the trailing edge of the sail.

The sail itself is made of a number of panels of sail cloth 34 extending rearwardly from the spar 30. The fullness built into the shaped panels of the sail cloth is such as to give the sail an aerofoil section. Although not shown in the drawing, the sail cloth could be extended to wrap around the spar 30 and extend back at least part-way of the sail to form a hollow aerofoil section near the landing edge of the sail.

The top and bottom edges of the sail are defined by struts 36 joined to the tips of the spar 30, and reinforcing ties 38 extend from the rear tips of the struts 36 to pegs 40 and 41 projecting forwardly of the spars 30 and then onto the point V of the spar 30.

The pegs 40 and 41 are provided for temporary abutment of the sail against the mast so as to avoid sudden wind pressure causing a loss of control by the sailer.

Although not shown, hinged tips for the sail can be joined to the struts 36. The upper one for each tack can be opened to increase the sail area. Both can be opened when the board is gliding.

The sailboard 10 is shown in the drawing on a port tack with the wind coming from the portside and as shown in the drawing it is the underside of the aerofoil shaped sail which is visible. The sailer stands on the board 1 2 and graspes one of the holding bars 32 so holding the sail and mast substantially upright and controlling the sailing of the sailboard 10 in a fashion similar to a conventional sailboard.

When he wishes to tack, the sail is swivelled by 180 about the joint 26 about the line 24 as he passes through the eye of the wind. On the starboard tack he then holds the other bar 32 and again sails the board 10 in a fashion similar to a conventional sailboard. Also the other peg 41 now abuts the mast to hold the sail in place.

When sufficient forward momentum has been achieved the board 10 can be arranged to glide. This is achieved by swivelling the sail to an intermediate 90 position relative the position shown in the drawing so that the aerofoil shaped sail is now substantially horizontal and so provides lift. To keep the sailer and board together, suitable footstraps 42 under which the sailer can hook his feet are provided.

When the sailboard 10 lands on water again after gliding, the sailer turns the sail to an upright position either on the port or starboard tack as appropriate and continues to sail.

Claims (12)

1. A sailboard having a mast joined by a universal joint to a board, an aerofoil shaped sail having a line of symmetry as between upper and lower halves of the sail, a swivel joint about which the sail is joined to the mast along a line substantially coincidental with the line of symmetry, swivel limiting means to limit the swivelling of the sail to approximately 180 between an upright port tack position and an upright starboard tack position, the sail passing through a 90 position intermediate these positions where the sail is substantially horizontal and provides lift for gliding, and a pair of holding bars, one for each of the port and starboard tack positions, for. a user to support the sail and mast in respectively the port and starboard tack positions.

2. A sailboard as claimed in Claim 1 in which the sail has been formed of sail cloth made up of a number of appropriately shaped panels.

3. A sailboard as claimed in Claim 1 in which the sail has been formed in one piece from a shaped film of synthetic plastics material.

4. A sailboard as claimed in any preceding claim in which at least the forward part of the aerofoil has been formed of two spaced shaped layers of material.

5. A sailboard as claimed in any preceding claim in which the sail has a leading edge which is either straight or rearwardly swept at an angle of up to 25 .

6. A sailboard as claimed in any preceding claim in which, in order to increase the sail area for gliding, retractable wing tips are provided at either end of the sail.

7. A sailboard as claimed in Claim 6 in which these wing tips are hinged to the rest of the sail.

8. A sailboard as claimed in any preceding claim in which the mast is joined by means of a universal joint at its lower end to the board.

9. A sailboard as claimed in any preceding claim in which the sail is joined to the mast by a swivel joint and a universal joint.

10. A sailboard as claimed in any preceding claim in which the swivel limiting means are in the form of hooks.

11. A sailboard as claimed in any preceding claim in which the holding bars are on the same side of the sail and are positioned one across each half of the sail.

12. A sailboard substantially as herein described with reference to the accompanying drawing.