GB2268918A - Tuneable sailboard sail - Google Patents

Abstract

An aerofoil section in the form of a sail 1 e.g. a sailboard sail comprises controllable openings 2 at "x" percentage chord length. The openings 2 are locally reinforced by a thin aerodynamic rings 3 which are flexible in bending out of plane with the sail 1, stiff in shear in the plane of the sail 1 and made fast to the sail 1 by bonding and/or fasteners. The openings 2 can be closed using removable tight fitting bungs 41, aerodynamically profiled on both sides and constructed of suitably flexible material to withstand repeatable flexing. Alternatively the openings may sealed by permanently attached flexible straps or closed by sliding shutters. <IMAGE>

Description

TUNEABLE WINDSURFER This invention relates to a sail, and more particularly to a tuneable windsurfer sail.

A sail works on the principle that an aerofoil section produces, under the action of relative forward motion in a compressible fluid, a pressure differential along it's chord length. The surface along the chord should be unbroken to achieve the full effect of the pressure profile developed.

However by introducing a small hole in the thin aerofoil, the pressure profile developed is reduced and thus the sail is effectively de-powered. Full power may be restored by simply covering the holes. Traditional methods of de-powering a sail are based on reducing the over-all sail area by means of reefing. This is already a well established method used in sail boats but is not well suited to windsurfers and has proven to be cumbersome and rather ineffective.

The tuneable windsurfer refers not to sail area but to the basic principle that any sail is an aerofoil, where a controllable interruption of the pressure profile along the aerofoil may be used to de-power and regain power to, the sail.

The objective of the tuneable windsurfer is to allow the sail to be easily-powered up and down without affecting the over-all sail area; enabling one to tune a single sail, not only to changing wind conditions, but also to ones windsurfing ability and learning curve.

In accordance to the present invention, there is provided a tuneable sail, comprising generally an aerofoil in the form of a sail, with one or more controllable openings at some percentage chord length, and the by which to control the said openings.

Specific embodiment of the invention will now be described by way of examples with references to the accompanying drawings in which: Figure 1 is a schematic cross-sectional view of a tuneable sail illustrating a typical pressure profile.

Figure 2 is a schematic cross-sectional view of the said sail, in which the pressure profile has been modified by uncovering the holes.

Figure 3 is an elevation of a sail, illustrating a typical application of holes and an exploded view of relevant components, in accordance with one application of the invention.

Figure 4 is a view of one of the holes of the sail in Fig 3 with the bung in place.

Figure 5 is an illustration of a different application of the invention, where permanently attached flexible flaps are employed to cover the holes.

Figure 6 illustrates a further application of the invention, showing enclosed sliding shutters and an exploded view of one shutter.

Figure 7 is a different application of the invention showing permanently attached shutters on hinges.

Referring to the drawings and initially to Figs 1 & 2, the tuneable sail 1 in accordance with the present invention comprises generally an aerofoil section in the form of a sail 1 with one or more controllable openings 2 at some percentage " x " chord length.

In accordance with one application of the invention Fig 3 illustrates openings 2 which are locally reinforced by a thin aerodynamic ring 3. The said ring 3 is flexible in bending out of plane with the sail 1,stiff in shear in the plane of the sail 1 and made fast to the sail 1 by bonding andor fasteners.

The removable tight fitting bungs 41 are aerodynamically profiled on both sides as illustrated in Fig 4 , and are constructed of suitably flexible material to allow repeatable flexing as experienced in removal and fitting to the opening 2 in the sail 1.

Fig 6-illustrates another application of the invention in which. the openings 2 are controlled by means of flaps 4.

The flaps 4 are of similar material to the sail 1 and are attached, along their length at one edge by means of stitching and,'or bonding thus acting like a hinged edge. The flaps 4 at their free edge will be stiffened with a batten 5. The flaps 4 when closed will allow the batten to fit with-in a small pocket 6 thus providing a relatively clean aerodynamic profile. The flaps d will be controlled by means of control lines 7 attached to the flap batten 5 threading forward through the batten pocket 8 of the sail 1 to the luff of the sail 1, through jam cleats 9.

An elastic shock chord 10 attached to the flap batten 5 threads aft through the batten pocket 8 and is attached to the trailing edge of said batten pocket 8.

When the control line 7 is released from the jam cleat 9, the elastic shock chord 10 will cause the flap 4 to pull open.

In accordance with yet another application of the invention shown in Fig 6 the openings 2 are defined by shutters, consisting of two locally stiff panels 12 and 13 ,bonded andor fastened at their edges to the sail,with an internal panel 14 free to move under the action of a knob 15.

Fig 7 illustrates a further application of the invention in which the openings 2 are locally stiffened with a panel 16 which is bonded and/or fastened to the sail 1. The said panel 16 is constructed from the same material as that used for rings 3 in Fig 2. The panel 16 is attached by means of a hinge 17 to a flap ;1 of similar material. The flap 11 is operated by means of control lines 7 and shock chord 10 as in Fig 5.

Claims (5)

1 A tuneable sail, comprising generally ar: aerofoil in the form of a sail with one or more controllable openings at some percentage chord length, and the means by which to control said openings.

2 A tuneable sail as claimed in claim 1 wherein the means to seal the openings are provided by removable closely fitting,aerodynamically profiled bungs.

3 A tuneable sail as claimed in claim 1 wherein the means to seal the openings are provided by permanently attached flexible flaps.

4 A tuneable sail as claimed in claim 1 wherein the means to seal the openings are provided by enclosed, locally stiffened sliding shutters.

5 A tuneable sail substantially as herein described with reference to Figs 1-7 of the accompanying drawing.