GB2030945A - Improvements in or relating to sails - Google Patents

Abstract

A sail for a wind-driven craft. The sail has at least one rib 14 extending thereacross, which rib is in the form of an inflatable tube. When inflated, the rib 14 adds stiffness to the sail, and assists filling by the wind. A connector pipe 16 allows the introduction or removal of air under pressure to or from the ribs. <IMAGE>

Description

SPECIFICATION Improvements in or relating to sails This invention relates to a sail for sailcraft, by which term is meant both sailing vessels and land vehicles provided with sails for propulsion.

Sailcraft usually carry a variety of designs of sails in order to make optimum use of the wind. In light conditions, it is usual to employ a relatively large sail in order to gain the maximum propulsion effect, but if a breeze is too light, a very large sail may not fill properly, giving a lesser propulsion effect than if a smallersail were used.

Consequently, it not infrequently is necessary to use a smaller sail than the ideal for given conditions.

It is an object of this invention at least to reduce the disadvantage mentioned above, whereby as large a sail as possible for given conditions may be used on a sailcraft.

According to this invention, there is provided a sail for a sailcraft, which sail includes at least one rib extending across the area thereof, the or each rib being in the form of a closed gas-tight tube attached to or defined in conjunction with the material of the major part of the sail and provided with a connector allowing the introduction of gas under pressure into the rib or the release of gas therefrom, whereby the stiffness of the or each rib may be adjusted by varying the gas pressure therewithin.

It will be appreciated that with a sail of this invention, provided the or each rib extends sufficiently over the area of the sail, pressuring the or each rib will tend at least partially to spread sail; in use on a mast this may assist the filling of the sail with wind, especially in light conditions. The or each rib may be pre-formed so that when inflated the or each rib has the profile of the sail when filled.

One possible form of the invention is for a gastight hose to be attached for instance by bonding to the material of the sail so as to extend thereover in a desired manner. The hose could alternatively be attached by means of a strip of material extending over the tube and attached for instance by stitching to the main part of the sail sheet.

Another possibility is to attach directly to the said material a strip of material along the long edges of the strip, so that the overlying areas of the strip and sail define a tube. In the latter case it may be necessary to treat at least the material of the sail where the strip is attached thereto, and possibly the material of the strip as well, with a suitable agent to render the tube defined thereby fully gastight. For example, the material of the sail may be treated with an elastomeric solution which leaves a flexible skin of natural or synthetic rubber on the treated area. The attaching of the strip may be effected by means of an adhesive which remains flexible when set, such as an elastomer-based adhesive. If required, such bonding may be reinforced with stitching.

The number of inflatable ribs provided on a sail as well as their disposition and extent across the sail, depends upon the degree of stiffness which is to be imparted to the sail when in use, though the stiffness would also depend upon the pressurisation of the ribs. The number and disposition may be varied from a single rib extending for example along the bottom edge of a sail or mid-way between the sides from the bottom to the top, to a plurality of ribs arranged either in a regular pattern over most of the sail area or disposed in strict dependence on the degree of support required at any particular point.

For instance, for a roughly rectangular sail four ribs may be provided each of which extends generally from one side of the sail to the other and which bisects the other ribs at the centre thereof. This has the advantage that all the ribs may intercommunicate, thus requiring pressurized gas to be introduced at a single point only. Another possibility is for several ribs to be disposed near the bottom of the sail to give increased stiffness in this region, further ribs being provided near the top of the sail to assist the filling of the entire sail.

Clearly, a wide variety of sails may be made in accordance with this invention, but it is envisaged that the invention will be of the greatest benefit with sails which are large and intended for use in relatively light conditions -- such as a spinnaker or a Genoa. Such sails are consequently difficult to use properly, and at times several efforts have to be made to get the sail fully filled with air: by providing ribs in accordance with this invention on such a sail, at least partial spreading of the sail can be achieved immediately, allowing the wind easily to fill the sail completely.

The connector may comprise a nipple communicating with the interior of a rib allowing the connection of an air-line or hose carrying pressurised gas. Alternatively, the connector may itself comprise a pipe communicating with the interior of a rib and provided at its end remote from the rib with means suitable for connection to a compressed air or gas source. Conveniently, the connector includes an automatic valve arrangement whereby pressurized gas may easily be introduced into a rib and yet the valve prevents the release of gas until manually operated. For instance, a Schrader-type of valve may be employed.

The gas to pressurize the ribs may be supplied by a manually-operated or foot-operated air pump, or may be supplied from a pressurized bottle, in which case gases other than air may be employed.

As mentioned above, the pressure used will depend upon the degree of stiffness which is to be imparted to a sail, and this in turn depends on various factors including number and disposition of the ribs, size of the sail and the rib dimensions, but a typical pressure may be as low as 2 to 3 Ibs/square inch gauge, though higher pressures may be used.

By way of example only, certain specific embodiments of this invention will now be described, reference being made to the accompanying drawings, in which: Figure 1 is a cut-away view through part of a sail arranged in accordance with this invention; Figure 2 is a diagrammatic view of one embodiment of a complete sail arranged in accordance with this invention; and Figures 3 to 5 are diagrammatic views of three further embodiments of sail.

Referring initially to Figure 1, there is shown a part 10 of a complete sail sheet to which is attached a gas-tight inflatible tube 1 The tube 11 is attached by means of a strip-like panel 12 of a material similarto that of the sail itself, which panel overlies the tube 11 and is attached by stitching 1 3 along the long edges thereof to the sail. In this way, the tube 1 1 is loosely supported on the sail, but may be withdrawn for replacement should it become damaged. Moreover, once the tube 11 is inflated, it bears firmly against the material of the sail and of the panel, and thus when inflated the tube is securely held in the required position.

The tube 11 is provided at a convenient point -for instance at a lowermost part of the sail with a pressure connector (not shown), allowing the introduction of compressed gas into, or the release of gas from, the interior of the tube. The construction should be such that the entire arrangement can withstand working gas pressures of up to at least 5 Ibs/square inch gauge. Tubes made of flexible synthetic resins such as polyethylene and polyvinylchloride may be particularly suitable, especially in view of their resistance to salt-water.

Figure 2 shows an embodiment of a complete sail of this invention. On this sail, a series of interconnected tubes is provided such that the tubes when inflated form ribs 14 which serve to spread the sail in the direction from top-tobottom. A further tube is also provided running parallel to the bottom of the sail and interconnecting the other tubes, and this further tube when inflated forms a rib 1 5 which serves to spread the sail at the bottom in the side-to-side direction. A flexible hose 1 6 is connected to the tube defining rib 15, to allow the introduction of gas or air under pressure into all of the tubes, as required. The free end 1 7 of the hose 16 is provided with an automatic valve (not shown) and -union, for receiving a standard air-line connector.

In use, the sail is set in the usual way, and then sufficient air is introduced under pressure through the hose 1 6 partially to spread the sail to allow it to fill with wind. The degree of pressurisation will of course depend on various factors, but can readily be adjusted as required through the hose 16.

Figures 3 and 4 show other possible forms of rib disposition on sails similar to that of Figure 2.

In Figure 3, the rib disposition is essentially radial from the approximate centre of the sail, all the tubes being interconnected at the centre. In Figure 4, the rib disposition is such that the sail readily is spread from side-to-side, especially at the bottom and mid-regions thereof.

Figure 5 shows a different design of sail, essentially of rectangular configuration and provided with tubes which divide the sail into four generally rectangular panels 17. The hose connector 1 8 for introducing air is disposed centrally along the bottom rib, for clipping to a mast 1 9. This design assists uniform spreading of the sail once set and inflated.

Many other designs of sail and rib configurations are of course possible and the above are given purely by way of example.

Claims (12)

1. A sail for a sailcraft, which sail includes at least one rib extending across the area of the sail, the or each rib being in the form of a closed gastight tube attached to or defined in conjunction with the material of the major part of the sail and provided with a connector allowing the introduction of gas under pressure into the rib or the release of gas therefrom, whereby the stiffness of the or each rib may be adjusted by varying the gas pressure therewithin.

2. A sail as claimed in claim 1, wherein the or each rib may be pre-formed so that when inflated the or each rib assumes the optimum profile of the sail when filled with wind.

3. A sail as claimed in claim 1 or claim 2, wherein the or each rib is constituted by a gastight hose attached to the material of the sail so as to extend thereover in a desired manner.

4. A sail as claimed in claim 3, wherein the gastight hose is attached by means of a strip of material extending over the tube and overlying the main part of the sail sheet in the region of the tube, the strip and sail being appropriately sewn together.

5. A sail as claimed in claim 1 or claim 2, wherein a strip of material is attached to the sail along the long edges of the strip of material so that the overlying areas of the strip and sail define a tube.

6. A sail as claimed in claim 5, wherein at least the material of the sail underlying the strip of material is treated with a suitable agent to render the tube defined by the sail and strip fully gastight.

7. A sail as claimed in claim 5 or claim 6, wherein the attaching of the strip is effected by means of an elastomer-based adhesive which remains flexible when set.

8. A sail according to any of the preceding claims, wherein the connector comprises a nipple communicating with the interior of a rib allowing the connection of an air-line or hose carrying pressurised gas.

9. A sail according to any of claims 1 to 7, wherein the connector comprises a pipe communicating with the interior of a rib and provided at its end remote from the rib with means suitable for connection to a compressed air or gas source.

10. A sail according to claim 8 or claim 9, wherein the connector includes an automatic valve arrangement whereby pressurised gas may easily be introduced into a rib and yet the valve prevents the release of gas until manually operated.

11. A sail substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

12. A spinnaker or Genoa sail whenever arranged according to any of the preceding claims.