The performance advantage to be gained from using wing type rigs has been appreciated for some, time, and several types of wing rig have been built, mainly for 'C class catamarans. These wing rigs have mainly comprised sections of substantially rigid aerofoil section. Although such sections can generate high levels of propujsive thrust, their rigid structure means that the aerofoil section of the wing is fixed. It is also known to have multiple sections in which individual sections are fixed but can be moved in unison to adopt a required profile. The rigid structure of such rigs means that reefing or stowage of the wing is either not possible or extremely cumbersome.

GB2386884 discloses a variable camber airfoil in which spaced pairs of actuators disposed inside the airfoil envelope configure movable parts thereof to apply deflections to resiliently flexible surfaces to vary the camber. This system appears to be primarily suited for aircraft rather than wind powered craft, as the provision of such mechanisms inside a sail is not a practical option for a sail. Furthermore, GB2386884 does not disclose an arrangement in which the opposed surfaces are made of a flexible sail material, that is one that can be stowed, reefed etc.

Accordingly, I have designed a sail arrangement in which it is possible to change the shape of the wing sail to suit tack, wind direction and so on.

In one aspect of this invention, there is provided a sail arrangement for a wind-propelled craft, said sail arrangement being of generally aerofoil section and comprising forward and aft generally longitudinal side-by-side mast elements capable of relative hinging movement with respect to each other, the rearward mast element having associated therewith first and second sail surfaces of flexible sail material which are connected together at a leach region and which extend forwardly to connect to spaced lateral regions of said aft mast element thereby to define a sail section, each of said sail surfaces in use adopting an adjustable degree of curvature in use when exposed to airflow across the sail according to the different effective chord lengths imparted to the respective sail surfaces by movement of the aft mast element away from a neutral position relative to said sail surfaces, and the forward mast element defining a leading edge region hingable with respect to said aft mast element.

In this manner, rotation of the aft mast element effectively shortens or relaxes one of said first and second sail surfaces (i.e. it shortens the effective distance between its forward connection to the aft mast element, and the leach region) whilst lengthening or tensioning the other, thereby allowing said first and second surfaces to adopt respective curvatures when exposed to wind flow.

Conveniently, said forward mast element is mounted on the craft by a mast step arrangement which allows the mast to pivot about at least substantially vertical mast pivot axis.

For other applications such as windsurfing, the mast may pivot about three axes.

In order to provide a self-tacking ability, a stay element is preferably connected to the mast at a distance from said pivot axis, whereby, under a wind load, said forward mast element tends to turn towards the wind.

Advantageously, the arrangement includes a boom arrangement connected at a forward end region to said forward mast element at a boom connection point forward of said pivot axis and connected at a rearward end region to said leach region. The boom arrangement may take many forms including that of a double-sided boom of wishbone form. The boom may be attached to the foot of the sail or, in an arrangement similar to that of a windsurfer, the wishbone boom may be located part way up the sail.

Various control means may be provided to control, or constrain, the movement of the forward and aft mast elements. Thus for example, the arrangement may include a forward mast element control means associated with said boom for controlling the angular position, and/or limiting the locus of movement, of the forward mast element relative to the boom on port and starboard tacks. The forward mast element control means may include a lever extending rearwardly from said forward mast element coupled to a first anchorage point on said boom, optionally by a flexible tie. Likewise, the arrangement may include an aft mast element control means associated with said boom for controlling the angular position, and/or limiting the locus of movement, of the aft mast element relative to said boom. Preferably, said aft mast control means includes a lever extending rearwardly from said aft mast element coupled to a second anchorage point on said boom, optionally by a moveable slider block. • Conveniently, the anchorage points referred to above are located on a transverse member connected between opposite sides of the boom, aft of the aft mast element. Where the wishbone boom passes intermediate the head and foot of the. sail, the first and second sail surfaces may be provided with respective generally aligned apertures through which the transverse element passes.

Preferably, the arrangement includes an outhaul which in use is operable to apply an adjustable tension between said leach region and the boom connection point on said mast thereby to modulate the curvature of the first and second wind surfaces.

Preferably, the forward mast element is hinged to said aft mast element about a hinge axis spaced rearwardjy of a forward region of said aft mast element. A fairing means may be associated with the forward mast element and/or the aft mast element to provide a generally continuous surface extending between forward and aft mast elements. The forward mast element may be a single element of fixed section (which may vary along its length) or it may be a plurality of fixed section elements hingedly interconnected, or it may comprise a unitary element which is resiliently reconfigurable.

Thus, said forward mast element may comprise at least two relatively angularly moveable elements mounted for movement above respective axes generally parallel to said mast pivot axis. In one arrangement said forward mast element comprises two elements pivoted together.

Alternatively, the forward mast element may comprise a plurality of flexibly connected sections which may be interconnected by pivot arrangements or flexural elements. Alternatively, said forward mast element may comprise a central, generally vertically extending flexural support element covered by a resiliently deformable material. Still further the forward mast element may comprise a longitudinal structural element surrounded at least partly by a resiliently deformable material such as e.g. a foam, contained within an elastically deformable outer layer e.g. of a synthetic elastomeric fibre such as Lycra®. The outer layer may also act as a continuous fairing extending to connect to the respective forward edges of the aft mast element to provide a continuous conformable fairing between the forward and aft mast elements. In order further to trim the sail, it is preferred to provide means to apply an adjustable twist to the aft mast element. This could, for example, comprise a pulley arrangement associated with the forward mast element and adapted to apply a torsion load to the aft mast element.

In another aspect, this invention provides a batten for use in conjunction with a sail, said batten being of generally D-section having a generally flat surface for being located to generally coplanar to the sail, and a bowed convex surface.

In another aspect, this invention provides a sail arrangement for a wind-propelled craft, said sail arrangement being of generally aerofoil section and comprising forward and aft generally longitudinal side-by-side mast elements capable of relative hinging movement with respect to each other, the rearward mast element having associated therewith first and second wing surfaces of flexible material which are connected together at a leach region and which extend forwardly to connect to spaced lateral regions of said aft mast element thereby to define a. main wing section, each of said wing surfaces having sufficient associated flexural stiffness for causing said surfaces to adopt a self-sustaining adjustable degree of curvature, in use when exposed to airflow across the sail, according to the extent of compression and tension imparted to the respective wing surfaces by movement of the aft mast element away from a neutral position relative to said wing surfaces, the forward mast element defining a leading edge region hingable with respect to said aft mast element, with at least one fairing element extending between said forward mast element and said aft mast element to span the gap therebetween.

In many instances the windward wing surface will be concave or flat and the leeward surface will be convex. In this way, the sail arrangement is configured so that it is possible to alter the profile of the wing, section by adjusting the orientation of the aft mast element relative to the wing surfaces selectively to apply compression to one and tension to the other, reacted e.g. by a reaction force applied to a boom or the like via a main sheet. The leading edge defined by the forward mast element is hingable to allow it to be hinged towards the wind and also to create, together with the main wing section, the required overall aerofoil shape. The flexible nature- of the first and second wing surfaces allows reefing of the surfaces where required. The aerofoil shape may be generally constant in the height direction of the aft mast element or it may vary along this direction. Where the section varies, this may be either to vary the shape of the aerofoil or it may be to impart a twist such that the aerofoil shape is. generally constant but that the angular orientation of the axis, connecting the leading edge and trailing edge of the aerofoil section with respect to the mast element varies. The twist may be controllable so that a required twist can be imparted to the aft mast element by activation of a suitable control device, or it may be a passive twist such that the mast element has a predetermined resistance to twisting which means that the sail adopts a degree of twist which allows for wind shear and/or for an amount of wind to spill from the upper region of the sail. In this manner the angular deflection at the bottom of the sail arrangement diminishes with progression up the mast so that there is much less or no angular deflection on the top. This allows release of leach tension. The twisting may also allow for control of the chord dimension of the sail arrangement. In one arrangement, there may be a sail head device which comprises a structural element that is secured to the top of each of the wing surfaces.

At the lower end, the wing members are preferably connected at the foot to a boom or similar device. The boom may be a conventional rigid straight boom or it may be made of a plurality of interconnected relatively rigid sheet elements or plates hinged end to end such that they are capable of flexing to accommodate the local curvature of the adjacent wing surface but resistant to upward movement.

Preferably, the wing surfaces have battens to provide flexural stiffness and/or compression resistance with the remainder of the wing surfaces being of flexible material of the type commonly used, for manufacture of sails. Preferably the battens are secured to the wing member at spaced vertical stations to allow the sail to be stowed or reefed as required.

The battens may have a constant or varying profile along their length in order to provide predetermined flexural characteristics. Furthermore, all or selected ones of the battens may incorporate a tensile constraint which provides low or no resistance to flexing of the sail member in one sense to provide a convex external surface but which is placed in tension when the wing surface flexes in the other sense, thereby limiting flexing movement in that sense on the windward side. In one arrangement, the batten may have a series of spaced spacer elements projecting into the interior of the wing envelope and having a tension element extending between the free ends of at least some of the spacer elements. The wing interior may also include other tensile or compressive elements to rig the wing profile so that it adopts a required configuration in particular conditions. In some arrangements, telescoping rods may be provided within the wing envelope, interconnecting the inner wing surfaces and operable to constrain the minimum displacement therebetween.

In one arrangement, the forward mast element has a generally continuous leading edge fairing comprising in a generally V-shaped nose region with respective surfaces extending back to overlap the leading portions of the respective first and second wing surfaces. The fairing element may be naturally resilient and formed so that the trailing edges of the fairing are urged into engagement with the respective first and second wing surfaces by their shape, so as to provide sliding contact. If required, further bias means or tension elements may be provided to apply a restraint and/or bias force such that the fairing is kept in contact with the leading portions of the first and second wing surfaces. In another arrangement, the fairing may be multi-sectioned with each section sliding over its neighbour to provide a generally smooth region at the interface between the forward and aft mast element in armadillo fashion. In a particularly preferred design, the forward fairing is made of a plastics composite material such as carbon fibre reinforced plastics material.

In another arrangement there may be a fairing element extending forwardly from the aft mast element and co-operating with the forward mast element or a fairing attached thereto. Thus the fairing element may be made of stretchable fabric (possibly including a stretchable foam pad) attached to the rear mast adjacent the luff region of each sail and stretching over the forward mast element,

In most applications, the sail arrangement will be required to be rotatable about an axis parallel to one or both, or coincident with one of, the forward and aft mast elements so that the wing section can be directed appropriately relative to the wind. In some applications the axis of rotation of the wing will be coincident with the hinging axis between the forward and aft mast elements, but in other arrangements it may be preferred to have the wing rotate about an axis displaced from the hinge axis. The mast elements may be moved or set in a number of different ways, but a preferred arrangement is to provide each with a separate drive arrangement. This may take the form of a respective lever or other suitable actuating member associated with each mast element, thereby allowing the angular orientation of each to be adjusted and set.

The first and second wing surfaces may be attached to the rearward mast element by a variety of means. In a preferred arrangement, each wing surface is provided with a fixing on the sail member or a batten attached thereto which co-operates with a mast fixing, such as e.g. a track, to allow the sail element to be raised or lowered relative to the. mast element, and to allow reefing of the sail. This is an important feature as it allows the sail arrangement to be used on offshore vessels as it allows de-powering of the sail arrangement. In one embodiment an arrangement such as gearing is provided such that hinging one of said forward and aft mast elements in one direction is accompanied by hinging of the other thereof in the opposite direction. In this way, the wing profile can be configured as appropriate for either tack.

The aerodynamic profile may be used for arrangements other than sails where a variable configuration aerodynamic element is required, for example for wings, propellers, deflectors or ducts. Thus, in another embodiment this invention provides a reconfigurable aerodynamic arrangement, said arrangement being of generally aerofoil section and comprising forward and aft generally longitudinal side-by-side spar elements capable of relative hinging movement with respect to each other, the rearward spar element having associated therewith first and second wing surfaces of flexible material which are connected together at a trailing edge region and which extend forwardly to connect to spaced lateral regions of said aft spar element thereby to define, a main wing section, each of said wing surfaces having sufficient associated flexural stiffness for causing said surfaces to adopt a self-sustaining adjustable degree of curvature, in use when exposed to airflow, according to the extent of compression and tension imparted to the respective wing surfaces by movement of the aft mast element away from a neutral position relative to said wing surfaces, the forward mast element defining a leading edge region hingable with respect to said aft mast element, with at least one fairing element extending between said forward mast element'and said aft mast element to span the gap therebetween.

Whilst the invention has been described above, it extends to any inventive combination or sub-combination of the features set out above, or in the following description.

The invention may be performed in various ways, and a number of embodiments thereof will now be described by way of example only, reference being made to the accompanying drawings in which:

Figure 1 is a general view of a self-tacking sail arrangement for a soft wing rig of this invention;

Figure 2 is a schematic section view through the sail and showing a wishbone boom; Figures 3(a), (b), (c), (d) are views of alternative embodiments of a forward mast element;

Figure 4 is a schematic view showing an embodiment of soft wing rig fitted to a windsurfer; ■ ^{•' •}

Figure 5 is a schematic view of an arrangement for imparting twist to the upper end of the aft mast element; Figure 6 is a general view of a sail arrangement for soft wing rig of this invention;

Figures 7(a) and (b) are respective horizontal section views through the wing rig profile in an up-wind/close hauled configuration, and when configured for operating with the wind further aft/on the beam or 'down-wind ¹ , respectively;

Figures 8(a) and (b) are respective section views through a typical batten for use in the wing rig;

Figure 9 is a detailed view of an example of a tensile arrangement for modifying the flexural characteristics of the battens; Figure 10 is a detailed view of an alternative example of a tensile arrangement for providing a pre-stressed region along a forward edge of the batten;

Figures 11 (a), (b) and (c) are respective detailed views showing track or similar arrangements for securing the battens/wing surfaces to the forward mast element; Figure 12 is a detailed view of an example of an articulated boom for use in the wing rig arrangement;

Figure 13 is a detailed view of a possible arrangement for the mast head area of the wing rig arrangement;

Figure 14 is a schematic view of a further embodiment of the invention in a gaff rig configuration; ^'

Figure 15 is a section view on lines A-A of Figure 14, and

Figures 16 to 18 are detailed horizontal section views through the leading edge of the sail ^{^} arrangement of Figures 14 and 15, showing a floating fairing for the leading mast element.

Referring initially to Figure 1, in this arrangement a sailing craft is fitted with a self-tacking soft wing rig. The soft wing rig comprises a forward mast element 110 (see Figure 2) which is pivotally connected for movement about a vertical pivot axis 12 to the hull 114. Pivoted to the forward mast element 110 is a rear mast element 18 (see Figure 2) which is in the form of an elongate member or extrusion to the opposite lateral extremities of which are attached a first and second sail elements 120, 122 respectively. The sail elements pass rearwardly from their attachment to the aft mast element to a leach region 124 where they are joined together to form a closed envelope. Each sail surface has 120, 122 batten sets 126 to enable to the surfaces to adopt respective curvatures as to be described in more detail below.

The forward mast element 110 comprises a main body portion and two aft extending fairing portions which cooperate with the aft mast element 118 and the sail surfaces to ensure that, on both port and starboard tacks, there is a smooth generally continuous surface extending from the leach to the leading edge on both the leeward and windward sides.

• A forestay 128 and shrouds 130 are attached to the leading edge of the forward mast section 110 at a fixing 132. The forces channelled through the forestay / stays and shrouds will cause the forward mast section to rotate in a direction generally in line with the notional direction of the wind load on the rig, This effectively enables the forward mast section 110 to rotate so that the leading edge moves towards the apparent wind direction, as is the case in many so-called

. rotating 'wing-section' type masts. In this arrangement a boom.34 of wishbone form is disposed adjacent the foot of the sail and pivotally coupled at 136 to the leading edge of the forward masf element 110 and connected by an outhaul 138 to the leach of the sail. It will be appreciated that when the sail is set, the angular disposition of the boom will be set by the mainsheet and the wind will fill the sail. On the windward side, as seen in Figure 2, the stay will tend to pivot the forward mast element towards the wind and this will cause the aft mast element 118 to pivot in the opposite sense so as effectively to pull the windward side 120 forward and let out the leeward side 122 so that an aerofoil section is defined having a flatter windward side and a bowed leeward side to provide a good aerofoil shape. . In order to control the self-tacking facility, the forward mast element 110 has a control lever 140 which extends rearwardly and is coupled to an anchorage point 142 on a transverse strut 144 on the wishbone by means of a flexible line 146 which limits the extent of the angular movement at the lever 140. In this way the lever 140 is linked to the boom so that, when the boom is let out, the lever will rotate accordingly to rotate the forward mast element. An aft mast control lever 148 of Y-shaped form extends rearwardly from the front part of the aft mast element. The stem of the Y of the control lever 148 passes through an eyelet in a block 150 that is mounted on the transverse strut 144 that extends between the two arms of the wishbone and so again the angular position of the aft mast element is controlled in part by the angular position of the boom. The block 150 may be mounted on a traveller, as shown, so that the lever may be moved to windward or leeward for possible fine tuning of the rear mast section.

Referring now to Figures 3 (a) to (d), there are shown section views of various fore and aft mast arrangements. In Figure 3(a) the forward mast element 10 is a single unit pivoted on the aft mast element. The forward mast element has the fairings 28 ^' extending rearwardly to cover the gap between the forward and rearward mast elements. The rearward mast element has lateral channels 52 into which the battens 26 are slotted. The battens 26 are preferably kinked inward to help the attached sail element 120, 122 fair into the forward mast element.

In the arrangement of Figure 3(b) the forward mast element 110 comprises two elements 110', 110" pivotally attached, each having fairings 128 in armadillo fashion to provide a smooth and generally continuous profile. As in the previous embodiment, the arrangement can be self- tacking with a stay attached to the nose of the leading forward mast element.

This may be extended further to provide a forward mast element 110 of segmented form with spaced individual segments 110 ¹ to 110 ⁶ interconnected so that they can rock relative to their neighbours to adopt a profile as shown in Figure 3(c). The individual segments 110 ¹ to 110 ⁶ may be connected by pivots 152 or by flexural elements. The segments could be made for example of a foam material such as Styrofoam that has been faced with carbon fibre or epoxy. The carbon fibre/epoxy Styrofoam segments may be made by solvent evacuation. The segments are spaced apart and, at the centre of each segment, there is a reinforcing packer on which each segment may rock. The segments 110 ¹ to 110 ⁶ may be held together by a number of fibre cordage lengths that pass through each of the sections and their reinforcing strips so as to act as a series of hinges.

A yet further arrangement is shown in Figure 3(d), where the forward mast element has a central flexural spine 154 running through a body 156 made of resiliently deformable material of a resilient foam.

In each of the above embodiments in which the forward mast element is itself flexible or articulatable, the mast element may be incorporated in a self-tacking arrangement.

It will be noted that the rotation of the forward mast section is assisted by the load from the wind counteracted by the restraining force of the shrouds and fore stay attached to the leading edge of the mast.

Referring to Figure 4, in this arrangement, a soft wing rig has been designed for use on a windsurfer. Here the forward mast element 110 is attached to the board 160 by an articulatable pivot arrangement 162 that allows the mast to pivot about three axes. Here the construction of the mast in section is similar to that shown in Figure 2 but, as the wishbone boom 134 is now part way up the sail, the anchorage strut 144 passes through the sail elements through respective aligned apertures 162. As with the previous sail arrangement, the boom is pivotally connected to the forward mast element and connected to the leach region of the sail 120, 122 by an outhaul. When exposed to wind on one side, the wind loading causes the forward mast element to turn towards the wind with a corresponding turning away from the wind of the aft mast element. This movement of the aft mast element thus pulls the leading edge of the windward sail forward thus tensioning it and pulling it flatter, whilst at the same time moves the leading edge of the leeward sail rearward, thus letting it out and allowing that surface to adopt a more bowed curvature to provide an aerofoil section. Referring now to Figure 5, in a soft wing sail arrangement, like other conventional mainsails, the wing or sail will twist off as it extends upwards. The amount of twist is mainly dependent on the amount of mainsheet tension. Twist in a sailing rig is important as it allows one to optimise the sail shape for the difference in apparent wind direction, both at water level and also higher up, sometimes referred to as wind sheer. It also enables the sailor to de-power the rig by twisting it off.

It is therefore an important feature of this wing rig design that the rear mast be able to twist substantially as it extends upwards. It is intended that this section be built so as to accommodate lateral twist. It may be preferable that a certain amount of susceptibility to twist be built into the mast so that the tensile and compressive forces, generated in the sails when the mast is rotated, cause the mast to twist.

In this arrangement two sets of twist-controlling mechanisms are located approximately 4/5th of the way up the mast. In this instance the mechanisms are a set of restraining ropes 166 or wires that pass from the rear mast 118 through to the forward mast 110, down pulley arrangements 68 which may be tensioned by lines 170, 172 that pass down the mast to deck level.

Importantly such twist controls may be left 'set' during tacking as they would not restrict the mast from assuming its rotation for the other tack.

The rig design is intended to be an improvement on mast-mounted sails - those that would usually be described as mainsail, mizzen or the like. Although the new design may be used on its own, it is also intended that it be used in combination with other types of sail (jib, spinnaker etc). Referring now to Figures 6 to 18, the embodiments and variants of the wing rig described below again provide a wing rig arrangement which has a generally aerofoil-shaped profile that can be adjusted in terms of curvature of the chord, wind attitude etc. whilst at the same time being made of a flexible material that allows the sale to be reefed for offshore sailing.

Referring initially to Figure 6, there is shown the sail arrangement 10 connected via a mast step 12 to a craft 14. At the leading edge of the wing arrangement there is shown . the

■forward fairing 16, aft of that being the principle sail area 18 at the foot of which there is a segmented boom 20 whose angular position is adjusted by a main sheet 22.

Referring now to Figures 7(a) and (b) the wing arrangement is made up of a forward mast element 22 hinged at 24 to an aft mast element 26. Connected to either side of the aft mast 26 are port and starboard wing surfaces 28 and 30 respectively, with the aft ends being connected at a leach region. Forward fairing 16 is connected to the forward edge of the forward mast element 22 and extends rearwardly to slide over the forward portions of the port and starboard wing surfaces 28, 30. As discussed in greater detail below, the fairing is suitably biased to ensure that its aft surfaces are kept in sliding contact with the wing surfaces to prevent a gap therebetween, during the normal range of operating conditions. The wing surfaces 28, 30 each have spaced vertical batten arrangements comprising battens 32 which may be provided with internal tension arrangements 34 as to be described below. The battens are connected internally of the principle sail membrane 36 which can be of any material or cloth suitable for use in the manufacture of sails. The wing surfaces 28, 30, each made up of the membranes 36 and battens 32, are secured to the aft mast 26 by means of a fixing allowing vertical sliding movement a to be described below, so that the wing surfaces can be reefed as required. In this arrangement, the port and starboard wing surfaces together 28,30 with the forward fairing 16 define an overall aerofoil shape which can be adjusted from a symmetric in-line shape with both port and starboard wing surfaces outwardly slightly convex, to a position shown in Figure 7(a) where one surface (the windward side) is usually flat or slightly concave (here the port wing surface 28) with the other surface (here the starboard wing surface 30) convex. This can be continued to the more deeply curved configuration of Figure 7(b). The adjustment between the neutral or equilibrium in-line position is achieved by rotating the forward mast element 22 and the aft mast element 26 so as to direct the forward fairing 16 in the appropriate direction and to configure the two wing surfaces by placing one in compression and the other in tension. The sail element in compression flexes to provide an outwardly convex surface whereas the surface in compression is flat or concave. As can be seen from a comparison of Figures 7(a) and (b), increasing the deflection and thus curvature of the convex surface causes the wing to have a fuller shape (i.e. a larger camber).

The above arrangement provides a design which comprises two rotatable mast elements 24 and 28 which are hinged together, with a fairing 16 which encapsulates the masts and two fully battened sail-like elements 28, 30 which attach to the aft mast 26 and link at the trailing edge or leach region of the rig.

When the two mast sections are rotated to create a shape of the desired aerofoil section, this varies the shape and attitude of not only the mast fairing 16 but also the batten/sail elements 28 and 30. As noted, the degree to which the forward aft mast elements 22 and 26 are rotated will also determine the desired depth of the wing section. When the vessel is close hauled the arrangement can be made to adopt a flatter shape and when the wind is further back on the beam the arrangement can be adjusted to have a fuller shape. In use the forward and aft mast elements 22, 26 can be rotated to provide an optimum rig configuration for efficient sailing in the given specific wind direction. In general, the mast elements are rotated in the following directions; the forward mast element 22 is rotated so that its leading edge moves towards the oncoming wind, whilst the rear mast element is rotated in the opposite direction. By increasing the amount to which the rear mast element 26 is rotated, the depth of the sail/wing profile is also increased. It will be appreciated that rotating the aft mast element 26 alters the shape of the rear sail area by putting the windward set of battens 32 into tension relative to the compression of the leeward set of battens.

In this embodiment, the forward fairing 16 is designed to provide as much as possible a generally continuous aerodynamic surface by distorting against the mast and the sail to which it makes contact. To achieve this, the fairing is made so that its shape and flexural characteristics are such as to conform to the desired configuration. Likewise, the battens 32 are designed to distort in such a way as to create, with the sail membrane 36 a good aerodynamic shape for this part of the rig. In another variant of the rig, contact between the fairing and the wing surfaces may be enhanced by the use of cordage (either elastic or inelastic) to hold a fairing in place.

The forward and rearward mast elements may be formed of carbon fibre-epoxy laminate surrounding a foam core material. I have found that this combination allows for lightweight sections of mast with good stiffness and torsional properties. It is quite possible to tailor the shape of the mast sections to provide varying degrees of torsional resistance so that, when under wind- load, a desired degree of twist may be induced in the mast section, The hinges 24 that connect the forward and rearward mast elements 22, 26 may also be manufactured from carbon fibre reinforced plastics materials.

Referring now to Figures 8(a and (b), the battens 32 may conveniently be formed of a suitable composite material such as carbon fibre reinforced plastics. These can be successfullymade using, in the main, hollow section. Each batten has a generally planar surface 44 where it is bonded to the sail membrane 36. 1 have found that this D-shaped batten provides good qualities although a multiplicity of different shapes, core materials and the types of fibre may be used.

The flexible characteristics of the battens may be varied not only by changing the shape or depth of the batten sections, but also by incorporating a supported tensile element 46 along much or part of the batten length, as shown in Figures 9 and 10. In this arrangement the tensile element 46 spans a major portion of length of the batten and is held away therefrom by means of spacers 48. The arrangement of Figure 9 resists a tendency of the windward battens to flex concavely to close the wing void somewhat under wind pressure. However the tensile element does not restrict convex flexing of the batten.

The battens 32 may also be pre-stressed using such a support system which may be limited to certain areas of the batten as seen in Figure 10. In this arrangement the forward section of the batten comprises a tensile element 50 which is under tension even when the batten is otherwise unstressed. Such a tensile member and its accompanying support system may also assist the compressive performance of the batten structure.

Each batten 32 will have a suitable fixing to allow sliding vertical movement with respect to the mast for reefing or stowage purposes. Figures 11 (a) to (c) show a number of different alternative arrangements. In Figure 11 (a) the aft mast element 26 is provided with a mast track 52 in the form of a groove with re-entrant lips in which a terminal 54 (typically of lozenge shape) may slot to retain the batten 32. In Figure 11(c) an upstanding track 56 of e.g. T-shaped section is secured to the aft mast element 26 and a car with a C-shaped groove designed slidably to interlock with the track is pivoted to the ^' end of the batten 32.

The battens are also interconnected at their end by suitable arrangements such as a leach end terminal (not shown) that links both sets of battens with their respective partners. The leach end terminals comprise a hinge-type bracket or other suitable arrangements such as an interlocking stud, to provide batten linkage. The terminals are designed in such a way that they can be readily released or uncoupled if so wished. Between the battens, the trailing, leach, area of the membrane 36 of the wing surfaces may also have means for releasably securing to the other membrane, such as Velcro ^® hook and loop fastenings to splice the two sails leaches together. The joining of the leach areas of the wing sails may be done to reduce leach flutter, drag or simply to provide structural integrity within this area of the rig. The use of a material such as Velcro ^® that can be easily separated and rejoined may assist in any reefing operation or make for ease of sail preparation.

The battens 32 may be bonded onto the inner face of the sail membrane 36 by use of a high peel strength adhesive material such as thermoplastic polyurethane film that may be placed between the batten face and sail membrane and heat welded together. Alternatively, double-sided adhesive tapes may also be employed for this task.

Although not shown, the batten sets may also be linked together within the void inside the aerofoil shape by spacer type bars. These could be telescopic so as to adjust to variations in the sail profile depth. The spacer bars may be arranged at intervals along the length of each batten or, if necessary, may even be used singly if so wished. The spacer bar may conveniently be attached by a flexible or hinged terminal at its connection to each batten.

The soft sail membranes 36 may comprise any of the usual fabrics used in sail manufacture and the choice of fabric will depend on what best suits each configuration of rig.

Although it is intended that each of the sail membranes is manufactured from substantially flat material, some shape may be incorporated into the sail as is done in other sail manufacture. The sail elements may be secured at the usual 'head' 'foot' 'leach' reefing points and mast track and further securing points along the foot and head of each sail may be incorporated into the rig designs. Figure 12 shows an articulated boom that provides sail attachment points along the foot of the sail. The flexible arm may comprise a series of articulated segments 60 articulated edge to edge or hinging about generally vertical axes such that, when fastened to the foot of the sail, they resist movement out of a horizontal plane and so are able to contribute to the tensioning of the sail. The arrangement may also incorporate the more full headed 'tornado' type of sail shape as shown in Figure 13, although this is not a strict requirement.

Attachments may be made along the head area of the sail, particularly if the sail head comprises more rigid structural elements that secure the top of each or both sail elements.

Although it is intended to 'hang' the rig off the forward mast element 22, the rig may be hung off the aft mast element or indeed from a location roughly in line with the axis of the hinge

26.

Although in many instances this will not be required, it may be beneficial in certain circumstances to design the rig to have sufficient strength in the mast section not to require 'diamond' type structural help, such devices may be incorporated if desired. The diamond or jumper type structures may be attached to any part of the rig structure.

It is intended that the mast entity sits atop a single mast step 12 this is designed to allow both mast sections to rotate about the mast step location in unison. The design of the mast step may also allow for more general movement to enable the rig to be raked or to assist in the stepping of the rig. Thus a ball and socket type stepping joint may be used. The sail elements of the rig may be hoisted up the rear mast section by means of a halyard or halyards. It may prove practical that a single, or linked halyards are used to raise the two sail elements although this is not entirely necessary. An important feature of this embodiment is that the arrangement may be reefed and so reefing points may also be built into the design of the sail.

Reefing points may also be built into the sails design. Further in the interests of reducing windage on the rig it may be desirable that any reefing lines run within the wing sail central void. It is intended that a boom is located at the foot of the sail area although this is not strictly necessary, as the ^' sail' may have something of a ^' free' foot.

The boom type structure may incorporate the foot tensioning armature described earlier or indeed may just comprise the armature components alone.

Where a boom strut is used it is intended that it extends from an area roughly adjacent the mast stepping point. It may be desirable that the area in which it is secured at the at the foot end is independent of the rotation rear mast section this is not strictly necessary.

The boom may be roughly conventional in character providing tension along the foot of the sail and tension through the sail by mainsheet tension it may also incorporate boom type vangs, kicking type straps and so forth. Referring now to Figures 14 to 18, there is shown another embodiment of a sale arrangement for a soft wing rig in accordance with this invention, of a gaff-type configuration,which allows the depth of the wing rig to be increased.

In this arrangement the wing rig 60 is supported off a mast assembly 62 made up of a forward mast element 64 and a rearward D-sectioned mast element 66 respectively pivoted together at 65. The mast is supported by halyards 68, and a gaff spar 70 supports the upper part of the wing rig. The upper part of the mast is provided with an aft foil section 74.

Referring now especially to Figures 16 to 18, the forward mast element 64 has an elongate V-sectioned flexible forward fairing section 76 bonded to it in the forward nose region 78, the fairing being closed at its rear end by an elongate U-sectioned aft fairing section 80, with the meeting edges 82 being joined by tape or similar. The forward and aft fairing sections together define a compliant aerodynamically smooth outer fairing or glove to the forward master element.

As will be seen by comparing Figures 16 to 18, as the forward mast element 64 is pivoted relative to the aft mast element 66, the interaction of the outer fairing 76 with the mast elements 64, 66 deflects the outer fairing with respect to the forward mast element to provide a smooth aerodynamic surface.

Furthermore, the lateral extremities 82 of the D-sectioned aft mast element are exposed when the forward mast element is deflected beyond a certain amount and forms part of the deflected wing surface (see upper exposed surface in Figures 17 and 18). As previously, the aft mast element 66 has attached to its opposite edges two wing surfaces 84 and 86 which extend rearwardly and are connected to each other at a leach region.

The operation and various possible internal mechanisms and elements for maintaining the shape of the wing surfaces described above may be used in part or whole, in this embodiment.