IMPROVEMENTS IN OR RELATING TO SAILS, BATTENS AND METHODS THEREOF

The present invention relates to battens and in particular fluid filled battens for sails and aerofoil structures. For aerofoil structures such as sails for a boat, parafoils for a kite and the like structures that are generally lacking in rigidity there is a need at least in some areas to impart rigidity to encourage the holding of the aerofoil shape to maintain desired camber or depth, chord or volume of the aerofoil section.

Increased efficiency can be obtained from a particular aerofoil (e.g. a sail) in a given set of conditions (e.g. wind speed, angle of sailing, sea state) if the aerofoil shape can be varied as the conditions change. For example changing of the depth, chord or similar, or the stiffness of the sail to achieve these properties can lead to better performance. This variability can allow an aerofoil to be varied over time to take advantage of the wind conditions present. Such improvements are desirable when trying to gain the greatest performance possible from an aerofoil (for example a sail on racing yachts), or when the sail has to be as multipurpose as possible (for example the sail on a super-yacht).

Previous methods for imparting such localized rigidity or shape to the aerofoil have involved battens that are held in a pocket of the aerofoil. These battens are of a predefined stiffness characteristic. The only way to alter the aerofoil-shape is to either increase or decrease the tension of the aerofoil or to change the batten to a more or less stiff batten.

To date battens have been manufactured from strips of material such as plastic, composite (e.g. carbon fibre, glass, Kevlar or similar) or wood. These have been simple strips, or a strip with a varied plan shape to vary rigidity over length. However their stiffness properties have not been variable over time.

Other solutions have involved inflatable spars to impart shape to the aerofoil. For example WO 2004/020284 by Gaastra relates to a "wing structure" for an airfoil (a paraglider) comprising a wing including an inflatable spar which is oriented at right angles to the airflow at the leading edge of the wing. The spar is oval, elliptic, or teardrop shaped for decreased drag. The spar is inflatable and includes a valve through which the spar may be filled. The wing further includes inflatable battens. The inflatable spar is formed from gas impermeable single layer fabric - including polyurethane (PU) and PVC. The spar includes an internal impermeable bladder, which is composed of PU. External stiffeners in the form of monofilament cord may be sewn into the exterior of the envelope of the spar.

This is a single skin solution and has several disadvantages. Long term retention of batten internal pressure is difficult with a single fabric layer integrally sewn into the wing. The fibres are also not oriented to impart maximum strength or formed as part of the batten to make a light, durable or strong structure. In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.

It is therefore an object of the present invention to provide a fluid inflatable aerofoil batten with variable properties, such as stiffness, to allow a change in its influence on the aerofoil shape to occur during use and methods of making such a fluid inflatable aerofoil batten, to provide an aerofoil batten with extended life and reduced wear, to overcome the above disadvantages or to at least provide the public with a useful choice.

In a first aspect the present invention may be said to broadly consist in method for making fluid (e.g. air, gas or liquid) impervious bladders ("bladders") for inflatable aerofoil battens that involves forming a tube, by the steps of, i) applying a matrix material ("first matrix material") to a forming body or bodies, H) applying a first reinforcing material to said first matrix material, iii) applying a further a matrix material ("second matrix material"), over said first matrix material, iv) compressing a lay-up resultant from (i) - (iii), and heating said lay-up resultant from (i) — (iii), to bond said first matrix material to said second matrix material and/or said reinforcement material.

Preferably said forming body or bodies is a male member.

Preferably said forming body or bodies is/are a mandrel(s).

Alternatively said forming body or bodies is/are a female mould member(s).

Preferably a release layer is provided in between said forming body or bodies and said first matrix material.

Preferably said release layer is a release agent.

Alternatively said release layer is a release film.

Preferably said release layer is both a release agent and a release film.

Preferably said first matrix material is a strip material.

Preferably there is an initial matrix material applied to said forming body or bodies prior to said first matrix material being applied in step i).

Preferably said first matrix material is wound onto said forming body.

Preferably a retaining material is applied before or after said first matrix material is wound thereon.

Preferably said retaining material is applied after said first matrix material is wound on.

Preferably said retaining material is a spray glue.

Preferably said first and/ or second matrix material includes any one or more whether blended or not of i) thermoplastic polyurethane (TPO), ii) polycarbonate, iii) polyester, iv) polyvinyl chloride, v) polyethylene, vi) a thermoplastic material, vii) rubberised epoxy, or vϋi) a thermoset material.

Preferably said reinforcing layer includes any one or more of i) kevlar™,

H) carbon fibre, iii) polycarbonate, iv) fibre glass, v) spectra™, vi) vectran™ and/ or vii) a reinforcing material.

Preferably between steps ϋ) and iii) there is an intermediate matrix material applied over said first matrix material.

Preferably between steps ii) and iii) there is an intermediate reinforcing material applied over said intermediate matrix material.

Preferably said second matrix material is also a strip material.

Preferably said second matrix material is wound onto said reinforcing layer.

Preferably between steps iii) and iv) there is a second reinforcing material applied over said second matrix material.

Preferably between steps iϋ) and iv) a matrix material ("third matrix material") is applied over said second reinforcing material.

Preferably said compressing utilises a compressive tape if the forming body or bodies is/are a mandrel. Alternatively said compressive utilises a vacuum bag or bladder if said forming body is a female mould.

Preferably said reinforcing material is encapsulated by said matrix materials such that there are at least some fibres of said reinforcing materials) able to move transversely and axially to one another. Preferably all of said reinforcing material is able to move transversely and axially in one bundle.

Preferably one bundle is defined as a group of fibres that is surrounded completely by said matrix material.

Preferably one of said first and second reinforcing material is aligned to provide strength to the bladder in the axial direction of said bladder.

Preferably one of said first and second reinforcing materials is aligned to provide strength to the bladder about the circumference ("hoop") of said bladder.

Preferably there is a layer of aluminium in said lay-up.

Preferably said layer of aluminium is interposed anywhere between said first matrix material and said third layer of matrix material.

Preferably said layer of aluminium is interposed between said first matrix material and said first reinforcing layer.

Preferably said layer of aluminium is intermediate said first matrix material and said first reinforcing layer. Preferably said matrix strip is tapered over its length prior to application to said mandrel or said lay up.

Preferably said impervious air bladder is tapered over at least part of its length.

Preferably said matrix material is between 25 micrometers and 10 millimetres thick.

Preferably said matrix material is 0.6 millimetres thick. Preferably said reinforcing material may be of a tape, strip, cloth form or may be a tow or filament form wound onto said lay-up.

Preferably said lay-up is heated up to 160 degrees Celsius.

Preferably said thermoplastic matrix material used is a high elongation polymer with elongation up to 800 percent.

Preferably the resultant said bladder can withstand pressures within the range of 400 PSI (1723 kPa) to 500 PSI (2153 kPa) internal relative pressure.

Preferably the resultant said bladder is inflated up to 250 PSI (1723 kPa) internal relative pressure. Preferably the resultant said bladder has varying diameter over its length.

Preferably there is present an opening to allow control of the internal pressure of said bladder.

Preferably said opening includes any one or more of: i) a valve; ii) a fluid connection fitting iϋ) a conduit.

Preferably said bladder is elongate and one end ("sealed end") of said bladder is sealed to prevent air escape.

Preferably said sealing is achieved by any one or more of: i) welding (ultrasonic or otherwise) ii) gluing (heat or chemical activation) iϋ) bonding iv) moulding, and or pinching.

Preferably said sealed end is created by a plug sealed at least to the internal surface of said bladder.

Preferably the other end of said bladder is sealed with a plug.

Preferably said plug contains said fitting,

Alternatively said valve is mounted on the body of said bladder (for example on the side of said bladder). In another aspect the present invention consists in an inflatable batten of or fot an aerofoil, comprising or including, an elongate fluid impervious bladder ("bladder"), said bladder constructed of a fibre reinforced matrix material, and pressure adjusting means in fluid communication with said bladder, whereby the pressure of said bladder can be adjusted such that the shape characteristics of said aerofoil can be varied.

Preferably said bladder is flexible.

Preferably said bladder is of a composite structure.

Preferably said bladder is tubular.

Preferably said bladder is formed from a lay-up of thermoplastic matrix material and at least one reinforcing material.

Preferably said pressure adjusting means is or includes a fitting.

Preferably said tube has two ends, at least one of said ends of said tube is sealed with a plug.

Preferably said plug is sealed at least to the internal surface of said tube.

Preferably said pressure adjusting means also includes a supply of fluid to said bladder to increase or decrease the pressure therein to allow adjustment of the stiffness properties of said bladder to in turn adjust the physical properties of the aerofoil on the fly. Preferably said fluid is any one or more of a gas (for example but not limited to join) and/ or a liquid.

In yet a further aspect still the present invention consists in an aerofoil with a plurality of fluid (e.g. gas or liquid) inflatable battens as here in described wherein the pressure in each of the plurality of said battens may be varied independent of the others to vary the properties of said aerofoil when said aerofoil is in use.

Preferably said aerofoil utilises said plurality of bladders as said battens.

Preferably said bladders are integral with said aerofoil.

Alternatively said battens slide into pockets on or of said aerofoil.

Preferably said aerofoil is a sail. In another aspect the present invention consists in an inflatable sail batten comprising of a double ended elongate sock capable of receiving and containing an inflation fluid (e.g. gas or liquid), said sock defined of a moulded fibre reinforced matrix.

Preferably said reinforcing material includes any one or more of i) kevlar, it) carbon fibre, iii) polycarbonate, iv) fibre glass, v) spectra, and/or any other reinforcing material. Preferably said moulded fibre reinforced matrix consists of at least one layer of reinforcing material extending in the direction of hoop stress of said sock, and one layer of reinforcing material extending in the axial direction of said sock.

Preferably said sock includes an opening for the passage of said inflation fluid into and out of said sock.

Preferably the pressure of said inflation gas in said sock can be varied over time when said sail batten is in use.

Preferably the bending force rigidity of said sock is proportional to the pressure of said inflation fluid in said sock wherein the rigidity can be varied by varying the inflation fluid pressure when said sail batten is in use.

Preferably said varying can be an increase and a decrease in pressure.

In a further aspect the present invention consists in a resiliently flexible fluid filled aerofoil batten comprising or including, an elongate bladder that includes a first and second end and that is sealed at both ends to define an enclosure for said fluid, the wall of said bladder including at least one laminated multi-layer assembly of; a first fibre reinforced layer of flexible resilient material, a second fibre reinforced layer of flexible resilient material, and a layer of flexible resilient material intermediate of said first and second fibre reinforced layer of flexible resilient material.

Preferably said first fibre reinforced layer includes a plurality of unidirectional longitudinally extending fibre filaments wherein all filaments extend in the longitudinal direction and do not contact each other..

Preferably said second fibre reinforced layer includes a hoop stress resistant fibre lay- up wherein the or all fibres do not contact each other.

Preferably said second fibre reinforced layer comprises of one spirally wound filament having a pitch large enough to ensure no self contact.

Preferably said batten is inflatable with said fluid via at least one opening to said enclosure. Preferably said batten is deflatable via an opening to said enclosure via which said fluid can egress from said enclosure.

Preferably said fluid is a gas.

Preferably said fluid is mixture of a gas or liquid

Preferably said fluid is a liquid. Preferably said batten is a sail batten.

In a further aspect the present invention relates to a sail shape influencing system of or for sail for a yacht that comprises or includes, a plurality of discreet inflatable sail battens each vertically spaced from each other, wherein each batten includes at least one bladder that can receive and retain a fluid to

pressurise said at least one bladder via a conduit engaged to an opening to said at least one bladder, and at least one pump to provide and pressurise fluid to each said at least one bladder via a respective conduit, a pressure controller for each batten to control pressure of each batten independent of the other battens.

Preferably said pressure controller is a controller that acts on a pump designated for one batten only.

Preferably said pressure controller is a pressure relief valve that is in fluid communication with said at least one bladder.

In yet another aspect the present invention consists in a system as herein described wherein the or each batten is as herein described.

In yet another aspect the present invention consists in a flexible fluid impermeable and pre-stressable wall structure of an elongate tubular fluid inflatable batten comprising or including, a first matrix material encapsulated fibre reinforced layer comprising of a plurality of longitudinally extending filaments extending in the elongate direction of said batten wherein none of the longitudinally extending filaments contact each other, a second matrix material encapsulated fibre reinforced layer comprising a spirally wound filament that does not contact any of the longitudinally extending fibres by virtue of the spirally wound filament being located at a different level within the wall structure to said longitudinally extending filaments.

Preferably said spirally wound filament does not contact itself.

In another aspect the present invention consists in a sail for a yacht that in use can have the individual pressures of battens within the sail of the yacht varied to form the desired shape of said sail.

In yet a further aspect the present invention consists in a moulded inflatable sail batten of a matrix of fibre and flexible thermoplastic material.

In another aspect the present invention consists in a sail batten or bladder as a product made by a process as herein described.

In a further aspect still the present invention consists in a yacht carrying a sail with battens having variable pressure as herein described.

Preferably said variable pressure can be controlled from the hull of said yacht.

In another aspect the present invention consists in a sail or sail structure including or able to use a sail batten of the present invention.

In a further aspect the present invention consists in a method of manufacturing an air impervious bladder as herein described. In another aspect the present invention consists in a bladder as herein described with reference to any one or more of the accompanying drawings.

In another aspect the present invention consists in an air impervious bladder made by any one or more of the processes and methods herein described with reference to any one or more of the accompanying drawings. Where used in this specification the term matrix means the material into which the reinforcing fibre is embedded; the material that the fibre reinforces. The matrix is a monolithic material, and is completely continuous. This means that the matrix material connects any point in the composite to any other point in the composite.

Where used in this specification the term reinforcing material means the material that is held by the matrix material and is the material that takes the majority of the tensile and/ or compressive stress. The reinforcing material is a discrete elongate material whether or long or short strand, and is either oriented or randomly oriented The reinforcing material can be a high modulus material known in the art, but may also be of a lower modulus material where necessary for the properties of the bladder for the batten. The reinforcing material may also come as a pre-impregnated material with some or all of the matrix material already applied.

Where used in this specification the term layer does not necessarily refer to a discrete layer, rather it also covers a layer, whether discrete or not, that has been bonded to another layer to form a continuum. However identifiable within the continuum are regions or zones - these are also referred to as layer. For example a region or zone of matrix, a region or zone of reinforcing material, or other added materials.

Where used in this specification the terms fibre(s) or filament(s) can mean a single fibre of filament or a number of fibres or filaments together. A plurality of fibres or filaments is also referred to as a bundle of fibres of filaments. The term 'comprising' as used in this specification means 'consisting at least in part of, that is to say when interpreting statements in this specification which include that term, the features, prefaced by that term in each statement, all need to be present but other features can also be present.

This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

With reference to Figures 1 through 6 preferred embodiments of the present invention will now be described, in which;

Figure 1 shows in perspective view a fluid inflatable bladder forming a batten, Figure 2 shows a cross section of the bladder of Figure 1 along the plane AA of

Figure 1,

Figure 3 shows a localised cross section of the lay up of the bladder,

Figure 4 shows an axial cross section of the bladder,

Figure 5 shows an aerofoil as a sail for a yacht with a plurality of battens, the bladders of the battens having pressure lines leading off them to allow independent remote adjustment of the pressure within each bladder,

Figure 6 shows a yacht with a sail having a batten formed from a bladder,

Figure 7 shows further ways of closing the ends of the bladder, by a) an integrally formed closure, and b) a pinched end formed closure, Figure 8 shows a cross section through a bladder under internal pressure p,

Figure 9 shows Detail A from Figure 8, showing one form of lay-up of the bladder, with internal additional fluid-proofing and/or release sheet, hoop fibres with encapsulating matrix, separating matrix layer, axially oriented fibres and outer encapsulating layer,

Figure 10 shows a hypothetical tube subjected to bending forces, Figure U shows the result of bending that tube, the bend outer surface, goes into tension (+), the bend inner surface goes into compression (-),

Figure 12 shows a bladder similar to that of Figure 8 with internal pressure, the axially oriented fibres of the tube are pre-tensioned by the internal pressure,

Figure 13 shows the result of the bladder of Figure 12 under three point bending (for example when tacking an aerofoil or sale from one side of a mast to another); because at least the axially oriented fibres are pre-tensioned, this tension has to be overcome before the bend inner surface fibres go into compression, the result is a bladder that stalls the onset of budding and the associated detrimental effects on die fibres and matrix,

Figure 14 shows in side elevation direct extrusion of the matrix onto a mandrel (with any layers or matrix and or reinforcing material present), whereby the mandrel (and any layers) is (are) moved through the stationary extrusion head or heads, and reinforcing is shown being added over the newly laid matrix, in this case by filament winding, whereby the filament is wound either by rotation of the mandrel (and or layers) and new layer, or the spool of filament is wound around and onto the mandrel (and or layers) and the newly extruded layer,

Figure 15 shows an alternative whereby the mandrel (and any layers) is (are) stationary and the extrusion head or heads is/are moved over the mandrel (and any layers), again a filament of reinforcing is shown added, again by rotation of the filament spool, or the mandrel (and any layers) and the newly extruded layer,

Figure 16 shows, in cross-section, various shapes of forming bodies that can be used to form bladders and battens of the present invention, in this case the forming bodies are male forming bodies, but as equally could be female forming bodies, at a) is shown a circular cross-section shape, b) an oval cross-section shape, c) a two piece forming body of two "D" shaped forming bodies to form a multi chamber bladder, and d) a flattened oval shape forming body,

Figure 17 shows in a) through d) the resultant bladders from the forming bodies shown in Figure 16, Figure 18 shows various fibre orientations in the lay-up of the bladder, at a) axial fibres and double crossing hoop fibres at an angle θ, and at b a similar construction to a but with a non crossing hoop fibre wrap, again the bladder may be made of one or more layers of axial and hoop fibre layers,

Figure 19 shows a peel away sectional drawing of a preferred embodiment showing a lay-up on a forming body as a mandrel with a release layer, an initial matrix layer, a first matrix material and first reinforcing material axially aligned, an intermediate matrix material, an intermediate reinforcing material again axially aligned, a second matrix material, a second reinforcing material "hoops stress aligned, a third matrix material and a final compressing layer, and Figure 20 shows in perspective view a) a "raft" array of bladders or battens forming a larger batten, and b) a three dimensional array of four bladders or battens forming a larger batten.

Preferred forms of the present invention will now be described with reference to the accompanying drawings.

The batten (1) consists of one or more bladders (19). In the preferred form the bladder (19) is a tube, preferably circular in cross section. The bladder (19) forming the batten (1) is formed by lay up. A forming body (2) is used. In the preferred embodiment this is a male forming body in the form of a mandrel (21). However in alternative embodiments the forming body (2) may be a female mould into which each of the subsequent described layers can be laid and thereafter the resultant lay-up is pressure formed. In addition there may be one or more mandrels, for example two inner mandrels as shown in Figure 16c, or an inner mandrel (21) and an outer mould (22) (possibly applied at the end of the lay-up sequence). The outer mould (22) for example can supply the pressure for pressure forming. This outer mould (22) may be a rigid mould, or as described below may be a flexible wrap or vacuum bag.

In other embodiments the forming body (2) may be a semi-rigid body such as an inflated body about which the lay-up sequence is performed. For example an inflated bag, e.g. of nylon of other resilient material, as a male forming body may be present and the lay-up is built upon this. The semi-rigid forming body is removed once the lay-up (17) is completed. In yet other embodiments the semi rigid forming body may remain with and/or form part of the resulting lay-up, e.g. as an additional gas impermeable layer. Heat and/or pressure may be applied to any one or more of the layers of the lay-up (17) to fuse or cause these to adhere the semi-rigid body to the resultant lay-up (17).

The forming body (2) is also not necessarily round. It could be oval or of other form as for example shown in Figure 16 a) through d). In the situation where the forming body (2) is multi-part as shown in Figure 16(c), the resultant bladder, shown in Figure 17c) is a multi-chamber construction.

A release layer (4) may be placed on the forming body (2). In the preferred embodiment this release layer (4) is both a release sheet material and also a liquid release agent. Such release agents and layers are known in the art. The release material may be removed from the resultant lay-up (17) when completed, yet in other forms it is not important that it be removed and it may stay with the lay-up (17) and become integrated with it.

In the preferred method the first matrix material (6), is located about the mandrel. Optionally (and preferably) before the first matrix material is applied, an initial matrix material (24) is applied about the forming body or bodies (2) and/or release material (4) if

pr esent. This initial tnattix material (24) can be applied by any of the methods in any of the forms described below.

The first matrix material may be wound on in a precursor form as a tape. In other embodiments it may be a sheet form or a preformed sock. In yet other embodiments still the matrix material may be deposited in a molten or semi molten form. For example the matrix material may be extruded, by one or more extrusion heads (23) onto the forming body (2) and its associated release material (4). Such extrusion may be by moving the forming body (2) with the extrusion head (23) still, or vice versa. Additionally there may be a rotation of the forming body (2) to aid formation of an even coating of the matrix material (6).

In the preferred embodiment the first matrix material (6) may be a resiliently elastic, elastomer, polymer, or monomer or compound. In preferred forms it is any one or more, or a blend of a thermoplastic polyurethane, polycarbonate, polyester, polyvinylchloride, polyethylene, rubber or rubberised epoxy, thermoset rubber polymers thermoplastic rubber, silicon, or any other thermoplastic or thermoset material.

The matrix may also exist in a precursor form such as a liquid for example an epoxy resin.

The matrix may also, either before or after further layers are added, have additional post processing applied. For example to form cross linking, either with itself, or subsequent layers, such as the next matrix layer or a subsequent reinforcing layer.

In the preferred embodiment a retaining material (such as a glue) is preferably applied after the first matrix material (6) is applied onto the mandrel.

The first reinforcing material is thereafter laid upon the first matrix material (6) (and retaining material if used). The first reinforcing material (8) is preferably a high modulus material. In preferred embodiment it is any one or more of, or a blend of,

Kevlar™ ,

carbon fibre, polycarbonate, fibreglass, Spectra™ Vectran™ or other reinforcing materials or combinations thereof.

In the preferred embodiment this first reinforcing material (8) is in the form of a strand or strands of fibres. The fibres of the first reinforcing material (8) are oriented with their direction of greatest strength substantially parallel to the axis of the bladder (19), the axial direction (5) to provide axial strength to the tube (20) that forms the bladder (19). The reinforcing material (8) may be applied as discrete strands extending parallel to the axial direction (5) of the bladder or as a single or multi-start filament(s) (18) applied by winding (at a very high pitch) axially onto the first matrix material.

Optionally and preferably an intermediate matrix material (26) is applied over the first matrix (6) and reinforcing (8) materials. This intermediate matrix material (26) can be applied in any of the forms as described in any of the methods as described. Over this intermediate matrix material (26) is also applied an intermediate reinforcing material (25). This intermediate reinforcing material (25) is applied in any of the forms as described by any of the methods as described. In the preferred embodiment this intermediate reinforcing material (25) extends along the axial direction (5) of the bladder.

Thereafter the second matrix material (10) is placed, preferably by winding, about the first reinforced material (8). However, any of the methods of application as mentioned above may also be used, e.g. a preformed sock or matrix material, extrusion etc, or may be present as a pre-impregnation of the first reinforcing material (8) or intermediate reinforcing material (25) if present.

The matrix materials described herein may perform several functions. The matrix can imbed and retain the reinforcing material. It acts to reduce wear of reinforcing fibres in the same and also adjacent reinforcing layers. In the preferred embodiment whilst imbedding and retaining the reinforcing fibres the matrix can allow substantial relative movement (but preferably not their contact or rubbing) of adjacent fibres to result in a strong yet flexible tube. The matrix also completely encapsulates each fibre or bundle of fibres. This reduces capillary pathways to prevent or reduce pressurising fluid escape. This also greatly reduces the risk of delaminations within a reinforcing layer.

The matrix material seals or separates one layer of reinforcing material from that of the next reinforcing layer. This offers the fluid-proofness required. Thus there are no, or very minimised, capillary pathways for the pressuring fluid to use to escape. The separation of one layer of reinforcing from the next also alleviates wear resultant from fibre to fibre contact and rubbing and therefore extends the life of the bladder.

If buckling of the bladder and/or the fibre or bundles occurs then any damage to the fibres or bundle can be ininimised by preventing adjacent bundles from rubbing over each other.

If desired there may be matrix layers to bond the reinforcing layers, and additional same or different matrix material added to encapsulate the fibre(s) of the reinforcing. Bundles of fibres are encapsulated by the matrix.

In the preferred embodiment after the second matrix material (10) is applied, a second reinforcing material (12) is introduced. The second reinforcing material (12) is preferably introduced with the direction of greatest strength at or near 90° to the axis of the tube (20); the hoop" direction (7). It can be introduced as a filament that is applied in a strand like manner and wound onto the lay up. This reinforcing material (12) takes up the hoop stress imparted into the resultant lay-up when the bladder is pressurised. In other preferred forms the "hoop stress" reinforcing may be at +/- 45° to the axial direction (5) of the tube (20). In yet a further embodiment the hoops stress reinforcing is at the angle θ of 57.6°.

This angle has been shown to allow the least relative movement of two fibres or fibres bundles that cross to each other. This relative movement is also referred to as "scissoring". To avoid contact of fibre to fibre within its own layer the hoop stress resistant fibre lay-up may consist of a single unidirectional wound filament, as shown in Figure 18b), that does not cross over itself. In alternative embodiments where separation of crossing bundles is achieved (e.g. by presence of an additional matrix or separating layer) the hoop stress resistant fibres may have two or more lay-ups of fibre that cross each other as shown in Figure 18a).

Thereafter a furdier retaining material may be applied to temporarily hold the layer(s) in place.

A third matrix material (14) is then applied over the top of the second reinforcing material (12). This again may be wound on in strip form and may be a thermoplastic polyurethane or the like thermoplastic material or any other form of matrix material as herein described.

Thereafter a compressing means (16), such as in the form of a tape, a further forming body, or a vacuum bag may be applied tightly over the resulting lay up. The resulting lay up is then heated. Where the matrix is a thermoplastic material the temperature is to a softening temperature of the thermoplastic matrix material. Where the matrix material is a thermoset material the temperature is to that required to set or cook the thermoset matrix material.

The matrix material may thereby join to itself in between the available gaps of reinforcing material to encapsulate the reinforcing material. However if the reinforcing material has a softening temperature close to that of the matrix material(s) then this also can join to itself or the matrix material.

In other preferred forms pressure can be applied in known ways by vacuum moulding the layers.

Whilst two and three layers of matrix and reinforcing material have been described here, it is to be understood that more layers can be applied onto or between those described and fall within the scope of the invention. For example further axial and/ or hoop or other orientation reinforcing layers may be applied depending upon the application. There may be additional materials added also to impart further desired properties. For example an aluminium foil layer may be added in the lay-up to act as a pressurised fluid barrier. In other embodiments one or more of the reinforcing layers may be omitted if the matrix layer is inherently reinforcing. For example the matrix layer may be laid down having a reinforcing material located within the matrix.

Once the lay-up is completed (and any curing or bonding has occurred) the forming body is removed. Preferably there is heat applied prior to this step to allow at least partial integration of the layers of the lay-up (17). This may be removed by mechanically moving the forming body in relation to the lay-up. This can be achieved, for example, by twisting or pulling one off the other. In other methods air may be used to lift the forming body from the lay-up, or vice versa. In either case the release layer, as mentioned, may stay on the forming body or may stay on the lay-up. The result is a bladder (19) that has flexibility, is pressurising fluid impervious and that has high fatigue and wear resistance and therefore a long life under loading conditions.

Once the bladder (19) is fully or partially formed it can be plugged at both ends and an opening or a fluid connection (9) is located either at one or both ends and/or somewhere along its length. In the preferred embodiment the fluid connection (9) is at

one end of the elongate bladder (19). In one form the fluid connection (9) is a valve to allow direct altering of the pressure of the fluid within the bladder (19). In other embodiments the fluid connection (9) is an opening that connects to a remote control of the fluid to adjust the pressure of fluid in the bladder (19). In further embodiments both are present.

In the multi-chambered embodiment of the bladder (19), shown as an example only in Figure 17, there may be one fluid connection (9) to adjust the fluid pressure with internal fluid communication between the chambers of the multi-chambered bladder (19). In other embodiments each chamber of the multi-chambered bladder (19) is separately controlled. The other or both ends of the tube are sealed to form the pressure chamber of the bladder (19). The sealing may be achieved by pinch closing and heating of the end as shown in Figure 7b, or insertion of a plug and heating or welding (Figure 2) or integral forming of the seal as shown in Figure 7a). The end may be sealed about any fluid connection (9) present or the fluid connection may be present in the plug that is sealed therein.

Figure 1 shows a batten that is formed from a fluid-tight or air impervious bladder (19) or tube (20) from the method described above. The bladder has a fluid connection or opening (9) at least at one end for communication with a pressure adjustable means (13). In the preferred embodiment the fluid connection (9) is a valve. The pressure adjustable means (13) may be a supply of pressurized fluid. The fluid may be gas for example air for example from a compressor, or a tank of compressed gas. In other embodiments a liquid may be used where desirable.

The result being that the internal pressure of the bladder (19) of the batten (1) can be adjusted via the pressure adjustable means (13) to vary the stiffness characteristics of the batten (1). The batten (1) is preferably formed from a tube (20) (as described above) of which each end is sealed. However other cross-sections are within the scope of the present invention as are multi-chambered bladders (19) - for example as shown in Figures 17a -d).

In the preferred embodiment the sealing is by locating a plug (Ha and 1 Ib) at each end. The plug may be made from the material similar to that of the inner presenting surface of the tube (20). In the preferred embodiment the inward presenting material of the tube (20) and thus also the material of the end plug (Ha and lib) is a thermoplastic material, and preferably a thermoplastic polyurethane.

The end plug (1 IA) can connect directly to the pressure adjustable means or indirectly via a fluid connection (9). In other embodiments there may be a permanent

connection to a source of compressed fluid that can be regulated to increase or decrease the pressure within the bladder (19) of the batten (1). The result is that an aerofoil (3) with an array of battens (1) where each of the pressures can be individually varied then the physical characteristics and shape of the aerofoil (3) can be varied. The batten (1) as part of, or inserted into a pocket of, a sail (an aerofoil (3)) mounted on a yacht (15) can then vary the characteristics of the sail.

The use of pressure within the batten puts at least the axially oriented reinforcing fibres into tension. When the bladder is bent to follow or form the curvature of the aerofoil the pressurised bladder can take a higher bend before the inside of the curve of bending goes into compression. In this way the onset of compression buckling of the bladder (19) is delayed. When reinforcing fibres are bent or buckled (for example when tacking the aerofoil) they may be permanently damaged and weakened. This can shorten the life of the bladder. The present invention delays the onset of buckling of the bladder and or fibres. Where buckling of the bladder or fibres does occur the separation of adjacent bundles of fibres can allow them to move relative to each other with out rubbing each other.

The advantage the present invention conveys is longevity of the bladder (19) and hence the batten (1) by reducing the buckling and bending and rubbing of the reinforcing fibres. This is particularly advantageous when the bladder (19) is cyclically fatigued by bending in one direction and then another, e.g. when tacking a sail.

The axially oriented fibres, eg in (8) and (25) in Figure 19 also offer resistance to undesired elongation of the bladder (19) due to the internal pressure p. The hoop stress fibres, eg (12) in Figure 19, offer resistance to the internal pressure p to prevent undesired circumferential enlargement of the bladder (19) and hence the batten (1). Additionally if the bladder is bent in only one direction or a set curve then it can be formed into this curve during the lay-up process. The pressurising of the bladder serves to make an even more resilient aerofoil batten.

The internal pressure p of the bladder (19) also serves to strengthen the bladder (19) walls and prevent or alleviate crushing of the bladder (19). In yet further embodiments, as shown in Figure 20a, a number of bladders (19) or battens (1) could be joined side by side to produce a "raft" forming a large batten (1) thus allowing fine trimming of aerofoil stiffness and properties. In other embodiments, as shown in Figure 20b, the array of battens (1) or bladders (19) may be three dimensional.

The foregoing description of the invention includes preferred forms thereof. Modifications may be made thereto without departing from the scope of the invention.