SAIL STRUCTURE

Abstract

Disclosed is a sail comprising a head, a tack, and a luff extending between the head and the tack; a luff region extending along the luff; wherein the luff region has a significantly higher degree of elasticity compared to the average elasticity of a remainder of the sail. Also disclosed is a method of making a sail comprising laying out material to form the sail; arranging material in a luff region of the sail and in the remainder of the sail such that in the direction of the luff, the luff region has a higher degree of elasticity compared to the remainder of the sail; curing or sewing the sail to form a cohesive structure.

Claims

1. A sail, comprising, a head, a tack, a luff extending between the head and the tack; and a luff region extending along the luff; wherein the luff region has a higher degree of elasticity compared to a remainder of the sail.

2. The sail of claim 1, wherein the luff region of the sail includes a first material and a remainder of the sail includes at least a second material, wherein the first material and the second material are different, and wherein an average stiffness of the second material is in a range of 2-20 times higher than an average stiffness of the first material.

3. The sail of claim 1, wherein the sail is a mainsail.

4. The sail of claim 1, wherein the sail is a headsail.

5. The sail of claim 2, wherein the first material has a failure strain of at least about 2.5% to about 30%.

6. The sail of claim 2, wherein the first material has a failure strain of at least about 2 to about 10 times the failure strain of the second material.

7. The sail of claim 2, wherein the first material has an average Young's Modulus of about 1 to about 60 GPa.

8. The sail of claim 2, wherein the first material has an average elasticity that is at least about 100% to about 2400% higher than an average elasticity of the second material.

9. The sail of claim 1, wherein there is an absence of sail fibres, or sailcloth fibres, that extend in a direction parallel, or at least substantially parallel, to the luff in the luff region of the sail.

10. The sail of claim 7, wherein there are sail fibres, or sailcloth fibres, in the luff region of the sail, the sail fibres, or sailcloth fibres, extending in a line that leaves an angle of greater or equal than about 15 degrees free from fibres relative to a direction parallel to the luff of the sail.

11. The sail of claim 2, wherein the first material extends at least 50% to about 95% of a distance between the head and the tack of the sail.

12. The sail of claim 2, wherein the first material extends up to about 10% to about 50% of a width of the sail towards a leech of the sail.

13. The sail of claim 10, wherein the first material extends towards a leech of the sail to a greater extent in the middle of the sail relative to a height of the sail compared to the luff regions towards the head and the tack of the sail.

14. The sail of claim 1, wherein the sail includes a third region having an elasticity less than other regions of the sail, this third region extending along at least a portion of a margin of the luff region between the luff region and the remainder of the sail.

15. The sail of claim 14, wherein the third region extends from the head to the tack of the sail.

16. The sail of claim 14, wherein the third region comprises carbon.

17. The sail of claim 2, wherein the first material comprises a gradient of reducing elasticity in a direction from luff to leech, as defined by its: (i) failure strain, or (ii) average Young's Modulus, or (iii) both (i) and (ii).

18. The sail of claim 17, wherein the first material comprises polyester.

19. The sail of claim 17, wherein the first material comprises polyester in combination with one or more of aramid and UHMWPE.

20. The sail of claim 1, wherein a difference in elasticity is achieved by a lesser material thickness in the luff region compared with the remainder of the sail.

21. The sail of claim 1, wherein in a luff direction, a ratio of a stiffness of regions outside the luff region and the stiffness of the luff region is in a range of 2-25 times greater.

22. The sail of claim 1, wherein an orientation of a material in the luff region is different from an orientation of a material in the remainder of the sail, such that the luff region has a higher degree of elasticity compared to the remainder of the sail.

23. The sail of claim 1, wherein the luff region does not comprise any carbon fibres oriented within 15 degrees of parallel to the luff, and wherein the remainder of the sail does comprise carbon fibres oriented within 15 degrees of parallel to the luff.

24. The sail of claim 1, wherein the sail is a twin skin mainsail having two skins defining the sail, wherein each skin has a luff region extending along the luff, and wherein each luff region has a higher degree of elasticity compared to a remainder of the respective skin.

25. A sails comprising: a head and a tack; a luff edge extending between the head and the tack; and a luff region comprising the luff edge and at least a portion of the sail adjacent the luff edge; wherein a degree of elasticity of the luff region and a degree of elasticity of a region of the sail adjacent the luff region are configured such that, when the sail is mounted to a sailing boat, tensioning the luff region assists to flatten the sail to a greater extent than would be achievable if the luff was of equivalent stiffness to a remainder of the sail.

26. A method of making a sail comprising the steps of: laying out material to form the sail; arranging material in a luff region of the sail and in a remainder of the sail such that in a direction of the luff, the luff region has a higher degree of elasticity compared to the remainder of the sail; and curing or sewing the sail to form a cohesive structure.

27. The method of claim 26, wherein the step of laying out material comprises laying out tapes of resin infused fibrous material.

28. The method of claim 26, wherein the step of laying out material comprises laying out fibres glued between sheets of plastic laminate.

29. The method of claim 26, wherein the step of laying out material comprises sewing together component pieces of fabric or laminate.

30. A method of making a sail having a luff region, wherein in a direction along a luff of the sail, the luff region has a higher degree of elasticity than a remainder of the sail.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0063] The invention will now be described by way of example only and with reference to the drawings in which:

[0064] FIG. 1 is a stylised side view of a Bermuda rigged sailboat, having a main sail and headsail.

[0065] FIG. 2 is a side view of sail.

[0066] FIG. 3 is a cross section through a sail.

[0067] FIG. 4 is a cross section through a sail showing a sail (D) with tension released on the luff of the sail to produce a sail with increased camber and a sail (E) with tension applied to the luff of the sail to produce a sail with the camber moved towards the bow and having a flatter profile.

[0068] FIG. 5 is a top stylised view of a batten as it may attach to, or bear upon a forestay.

[0069] FIG. 6 is a top view of a twin skin mainsail.

[0070] FIGS. 7-9 depict a side view of the sail in different configurations when in use.

[0071] FIGS. 10A-10C are cross sectional views through a sail when in use.

[0072] FIG. 11 is a side view of a sail with square or quadrilateral shape.

[0073] FIGS. 12A-12B show results of numerical analysis in relation to a behaviour or a performance of sails.

DETAILED DESCRIPTION OF THE INVENTION

[0074] Described is a sail having material with a lower elastic modulus and higher failure strain in the luff region compared to the body of the sail. This provides for a sail that is effective to power up or power down the sail in response to the wind speed or the heading of the yacht relative to the wind direction.

[0075] Sail power is controlled by three main power sources being angle of attack, camber (or depth) and twist.

[0076] Camber is the amount of curvature (otherwise known as depth) in a sail. It is measured as a proportion of the distance from luff to leech. A mainsail with a maximum camber of 5% is a flat sail, while a camber of 15% would mean a deep or full main.

[0077] A deep (or fuller) sail provides more force while a flatter sail creates less drag for a given amount of total force. A flatter shape is better in heavy air when a boat is overpowered. A deep sail is better in lighter air when a boat is underpowered.

[0078] A sail can be controlled by the amount of depth as well as its position. The usual goal is to put the deepest draft position about 40-50% of the way aft from luff to leech in a mainsail and 30-40% aft for the jib.

[0079] Draft position (along with camber) is adjusted using the halyard and/or cunningham. Ideally the draft is set and is kept at about 30% to about 50% away from the luff. However, as the wind strength increases, wind pressure will move the draft position aft and the halyard and/or cunningham will require tensioning to move the draft forward once again.

[0080] Old sails, which have been permanently deformed, show their age because more and more halyard and/or cunningham tension is required to keep the sails flat and to maintain the draft correctly positioned.

[0081] In light winds it is often advantageous to move the draft aft by slackening the halyard or cunningham.

[0082] Tightening the headsail halyard, or cunningham, will typically move the draft forward and make it flatter. Easing the genoa halyard, or cunningham, will typically move it aft and make the sail fuller.

[0083] The general arrangement of the most basic elements of a yacht 1 is shown in FIG. 1, which depicts a Bermuda rigged yacht. While a Bermuda rigged yacht is shown it should be appreciated that the elastic luff can be utilised on other rig styles. A yacht 1 typically comprises a mainsail 3 and a head sail 4 (which includes genoas, jibs and staysails). The mainsail 3 body comprises a head 9, being the top, a tack 10, being the leading edge bottom corner, and a clew, being the trailing edge bottom corner. The mainsail 20 further has a luff 8, being the leading edge, a leech 6, being the trailing edge, and a foot 7, being the bottom.

[0084] The mainsail is typically attached to the mast, the mast generally including a track through which a portion of the edge of the sail luff 8, or clips that attach to the sail luff, travel to retain the sail to the mast 2. A main halyard attaches to the head 9 of the sail and is used to host the sail up the mast 2. A boom 12 extends from the mast and attaches to the foot 7 of the sail. The boom 12 typically includes a tract that through which a portion of the edge of the sail foot 7, or clips that attach to the sail foot 7, travels to retain the sail to the boom 12. On larger yachts, the boom 12 may include a self-furling system such as an in-boom furling system. Some yachts may not have a boom and instead are sheeted directly to the yacht.

[0085] The sail typically includes 1 or more battens 11 that assist sail shape and performance. The battens can be more or less evenly-spaced along the leech of the sail. These battens tension the sail, provide rigidity and help maintain a smooth aero dynamic shape. The battens 11 typically are inserted into a slot or sleeve in the sail that extends from the leech 6 of the sail 3 towards the luff 8 of the sail 3. Given sails are formed by a flexible sheet material, typically made largely of non-rigid materials and rigid materials, the battens help the sails to resist compression, which would lead to wrinkling of the sail. Battens are formed of rigid materials such as fibre reinforced plastics of fibreglass, carbon fibre, or a combination thereof. Once inserted into the sleeve in the sail 3, the battens are typically placed under longitudinal compressive load. For example, through the use of an elastic portion within the sleeve.

[0086] The headsail 4, if present, sits forward of the mainsail 3 and typically attaches to the forestay 5, using attachment devices such as by clips or pockets on the luff 7 of the headsail 4. The headsail 4 can be hoisted up the forestay 5 via a headsail halyard that extends from the mast 2. There are a range of different types of headsails 4 with the Genoa and Jib being the most commonly used. Both these types have different subtypes depending on their intended use. Headsails 4 are usually classified according to the relative weight of the sailcloth used and the size or total area of the sail. The headsail 4 may include battens 11 that assist in maintaining an optimal shape for the sail.

[0087] As described, the luff region of the headsail or mainsail can be formed from material that has a degree of elasticity. Suitable materials may comprise, for example, yarns, filaments, fibres, fabric or film. This elastic material provides for greater stretch, for example, in a direction parallel to the luff or mast, as tension is applied in this direction. It is to be understood that the luff region includes the luff but can include regions of the sail that extend some way aft from the luff as well, as indicated in, for example, FIG. 7.

[0088] In general terms, techniques of manufacturing the sail comprise composite tapes where the load bearing fibers are impregnated with resin (no external films, 3Di), laminated string sails where the load bearing fibers (yarns) are sandwiched between plastic films, and panel sails where rectangular or triangular panels of fabric are stitched or glues together. It is to be understood that any of the above techniques may be used to manufacture both the luff region of the sail and the remainder of the sail, and that the orientation of the load bearing fibers or yarns may be varied in the luff region and the remainder of the sail to achieve a higher degree of elasticity in the luff region. As explained above, the term “higher degree of elasticity” includes the meaning of “lower stiffness” and/or the meaning of “higher failure strain”, and/or generally “higher deformability”.

[0089] In one embodiment, the sails of a yacht (i.e., mainsail and the headsail) comprise an elastic material in the luff region and a stiff material running from the tack to head through the body of the sail. Due to this arrangement of the materials, in the present invention, when pulled down on the tack with the head fixed (or vice versa), the primary structural band (the second, or stiffer, material) of the sail straightens and thus flattens the sail.

[0090] In this embodiment, the elastic material may extend along at least 50% of the distance between the head and tack of the sail, and at least a portion of the elastic material extending on average up to 50% of the width of the sail towards the leech of the sail. By allowing the luff region to stretch the tack can be pulled down further which straightens the primary structural band through the body of the sail. This flattens the sail to a much greater degree than would be achievable if the luff region was stiff.

[0091] In one embodiment the elastic region comprises a fibrous material with a linear density of about 200, 600, 1000, 1400, 1800, 2200, 2600, 3000, 3400, 3800 or 4200 dtex, and suitable ranges may be selected from between any of these values. In one embodiment the fiber material that forms the elastic region has an elongation at break of about 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20%, and up to 30%, and suitable ranges may be selected from between any of these values. In one embodiment the material that forms the elastic region comprises, or is formed from, polyester.

[0092] In some embodiments the elastic region comprises a fibrous material with a linear density of about 200, 600, 800, 1000, 1400, 1800, 2200, 2600, 3000, 3400, 3800 or 4200 dtex, and suitable ranges may be selected from between any of these values. In some embodiments the elastic region comprises a material with an elongation at break of about 2, 2.5, 3, 3.5 or 4%, and suitable ranges may be selected from between any of these values. In some embodiments the elastic region comprises of aramid fibres.

[0093] While polyester and aramid have been given as examples for materials suitable for use in the elastic (or first) region, other materials may be used as well, including such with elongation at break between the values given in the above for polyester and aramid. Materials may also be used that have larger values of elongation at break than those indicated for polyester, for example, nylon.

[0094] In one embodiment the elastic region comprises a material with a linear density of about 200, 6000, 1000, 1400, 1800, 2200, 2600, 3000, 3400, 3800, 4200 dtex, and suitable ranges may be selected from between any of these values. In one embodiment the material is a ultra-high molecular weight polyethylene.

[0095] In some embodiments, the luff region or elastic region does not include fibres oriented in a direction parallel to the luff. Instead, the sail in the luff region may be constructed from a material like carbon tapes or yarns that are oriented so that they do not have any fibers supporting load in the luff direction. In these embodiments, when the remainder of the sail does include fibers oriented in the direction parallel to the luff, a relative decrease in stiffness of the luff region parallel to the luff is achieved which leads to the favourable effects in relation to flattening the sail set out in this disclosure.

[0096] The elastic region may be formed from a combination of materials to form a composite, laminate, or fabric. The three types of materials defined above may be combined in ratios to provide the desired degree of elasticity, in combination with or without resin (matrix) material or a plastic film in the case of laminate sails.

[0097] The stiffer material may be selected from carbon, or may be formed from a combination of materials to form a composite, laminate or fabric. Examples of suitable materials include combinations of carbon and ultra-high molecular weight polyethylene (UHMWPE), aramid, and aramid/polyester. The stiffer material may have an elongation at break of about 0.5%, 1.0%, 1.5% or 2.0% and suitable ranges may be selected from between any of these values. The carbon may have a modulus of about 200, 250, 300, 350, 400, 450 to 500 Gpa, and suitable ranges may be selected from between any of these values.

[0098] The carbon may also be used in the material in the elastic region to give an element of stiffness but with the fibre orientation at a greater angle to the luff. A preferable range for this angle comprises angles greater or equal than 20 degrees.

[0099] The materials used in the luff region include, but may not be limited to 100% polyester (closest to the luff), polyester/aramid mixture and carbon or a carbon/UHMWPE mixture. The stiffness and strength of the elastic elements used in the luff region are be summarised below: [0100] Polyester [0101] Youngs Modulus=1-20 GPa [0102] Failure strain 6-10% [0103] Aramid [0104] Youngs Modulus=80-120 GPa [0105] Failure strain 2-3% [0106] UHMWPE [0107] Youngs Modulus=80-120 GPa [0108] Failure strain 3.0-4.0% [0109] Carbon [0110] Youngs Modulus=200-500 GPa [0111] Failure strain 0.5-2.0%

[0112] According to an embodiment of the invention, as depicted in FIG. 2, when the tack 10 is pulled down through a luff tensioner 17 in the downward direction, then the load predominantly travels from tack through the front of the stiff region of the sail. If the sail had constant stiffness then the load would predominantly travel though the most direct path which is directly up the luff of the sail. As tension is increased in the luff region, the area of greater stiffness 16 moves in the direction of the force F and straightens which results in a reduction of sail camber. The force F may produce compressive forces in the sail that are typically carried through to the forestay through the battens. This force can project the luff (and forestay) forward. In some embodiments, the sail could be designed without any battens but with bending stiffness so as to take compression in the direction of the force F, but this region would also need to have high elasticity in the direction parallel to the luff.

[0113] As mentioned, the sails may include battens that can bear and push the forestay forward and this effect is enhanced with the use of the elastic material on the luff.

[0114] As a mainsail is pulled down on the tack, the battens could push against the mast and may help it bend. Also, the aft angles of the primary load paths out of the tack and head of the sail, which is generated due to the shape of the front of the second (stiffer) region, induces increased bending of the mast.

[0115] In the present invention, the mainsail and/or the headsail comprises of stiff and elastic regions in which the elastic regions have high failure strain and low Young's modulus compared to the stiffer materials which have low failure strain and high Youngs modulus.

[0116] Furthermore, at the margin between the elastic region and the rest of the sail, there is a zone of material with higher stiffness.

[0117] The camber and draft position can be adjusted with forestay tension. This is easy to adjust on a masthead rigged boat if there is an adjustable backstay.

[0118] Referring to FIG. 6 embodiment, there is shown a mast 2 with respect to the leech 6 and luff 8 of the sailboat 1. In this embodiment two mainsails are attached with one each side of the aft face of the mast in order to make a smooth aerodynamic section. A skilled addressee will appreciate that even for these configurations with more than one sail, elastic material with high failure strain in the luff region in combination with relatively stiffer material aft in the sail can be used to enable more effective shape control and depowering through application of luff tension via the cunningham or halyard. The embodiments of the invention described previously for conventional mainsails apply equally to this twin mainsail configuration. In one embodiment, what is disclosed is a sail comprising a load bearing material in the luff region of the sail, wherein under highest stress, the elastic properties of the load bearing material in a direction within 15 deg of being parallel to the luff may have: (i) a failure strain of at least 2.5%, or (ii) an average Youngs Modulus of less than 60 GPa, or (iii) both (i) and (ii), the elastic material extending along at least 50% of the distance between the head and tack of the sail, and at least a portion of the elastic material extending on average up to 50% of the width of the sail towards the leech of the sail. The sail could be a mainsail or a headsail.

[0119] The sail may comprise two different materials being a first material in the luff region of the sail and a second material that defines the remainder of the sail, wherein the average elasticity of the first material (i.e. elastic material) is at least about 2, 4, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26 times higher than the average elasticity of the second material, and suitable ranges may be selected from between any of these values. The materials are preferably composite materials, or a mixture of two or more different types of materials.

[0120] The elastic or first material may have a failure strain of at least about 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5% to about 10%, and suitable ranges may be selected from between any of these values. The elastic material (or first material) may have an average Youngs Modulus of about 1 to about 60 GPa.

[0121] It will be appreciated that the material of the sail is a composite of multiple materials. Some of those materials will have a Youngs Modulus of less than 50 GPa (e.g. glue, mylar, plastics etc).

However, when referring to a failure strain, what is being referred to is the main load bearing material in a region of the sail, such as the luff region. While incidental material may include a failure strain less than 2.5%, given that material does not form a significant portion of the sail material, it is not to be considered when assessing failure strain.

[0122] The direction of the elasticity being considered may be limited to being along or within about 15° relative to the luff.

[0123] There may be an absence of sail fibres, or sailcloth fibres that extend in a direction parallel, or at least substantially parallel, to the luff in the luff region of the sail. The sailcloth fibres in the luff region of the sail extend in a line that is an angle of greater than about 15, 20, 25, 30, 35, 40 to about 45° relative to a direction that is parallel to the luff of the sail, and suitable ranges may be selected from between any of these values. As the skilled person will appreciate, such orientation of the fibres in the luff region leads to a limitation of the load that the material in the luff region can take in the luff direction. In other words, such wider angles contribute to the luff region having a lower stiffness in the luff direction.

[0124] The elastic material (or first material) may extend at least 50, 55, 60, 65, 70, 75, 80, 85, 90 to about 95% of the distance between the head and tack of the sail, and suitable ranges may be selected from between any of these values. The elastic material (or first material) extends up to about 20, 30, 40 to about 50% of the width of the sail towards the leech of the sail, and suitable ranges may be selected from between any of these values.

[0125] The elastic material (or first material) may extend towards the leech of the sail to a greater extent in the middle of the sail (relative to the height of the sail) compared to the luff regions towards the head and tack of the sail.

[0126] The elastic material (or first material) may comprise polyester, or polyester in combination with one or more of aramid and UHMWPE. The second and third materials may comprise carbon, aramid or a combination of carbon, aramid and UHMWPE. The composition or % of aramid and UHMWPE in the central region of the luff region of the sail may be lower than in the upper and lower regions of the sail.

[0127] The elastic material (or first material) may comprise a gradient of elasticity, as defined by its: (i) failure strain, or (ii) average Youngs Modulus, or both (i) and (ii), over the width of the elastic material within the luff region. The elasticity of the elastic material (or first material) may decrease from the elastic material adjacent the luff to the elastic material aft of the luff. This gradient of elasticity can be achieved either by varying stiffness or through the use of different materials, or concentrations of different materials.

[0128] The structure and position of the stiffer material can be used to move the draft position forward or aft depending on where the structure lies relative to the natural draft position of the sail

[0129] As shown in FIG. 7, the shape and positioning of the elastic region 18 relative to the stiffer sail material 19 can be modified to effect different parts of the sail. For example, as shown in FIG. 7, a lower biased structure will have more influence on the lower part of the sail. In comparison, as shown in FIG. 8, an upper biased structure will have more influence on the upper part of the sail. This will also affect the section shapes due to the tendency of the position of the edge of the stiffer region 16 to move the position of maximum draft. As shown in FIG. 9, the positioning of the boundary or fringe between the two materials can be modified to influence the sectional shape of the sail. For example, as shown in FIG. 10A, forward positioning of the fringe pushes the position of maximum draft aft. In comparison, as shown in FIG. 10B, aft positioning of the fringe pushes the position of maximum draft forward.

[0130] FIG. 12 shows results of a Finite-Element-Analysis (FEA) comparing a prior art sail and a sail according to the present disclosure. In FIG. 12(a), the solid line represents a common sail with a luff region that has approximately the same stiffness and failure strain as the remainder of the sail, while the dashed line represents a sail in accordance with the present disclosure. The skilled person will appreciate that in the prior art sail, at 100% cunningham load (horizontal axis) a percentage increase in luff length, shown on the vertical axis, is about 0.38%. Contrary thereto, the sail according to the invention exhibits an increase in luff length of about 0.19% at 100% cunningham load. In other words, as is apparent from the figure, at a given elongation of the luff the load generated in the cunningham as a percentage of maximum load is much lower in the sail according to the present disclosure, because of its lower stiffness in the luff region. As a side note in FIG. 12(a), a negative increase in luff length in the range of between 0% and approximately 25% cunningham load should be interpreted as wrinkles in the luff region.

[0131] The graph shown in FIG. 12(b) has the same horizontal axis as the one of FIG. 12(a) but shows sail mid camber in percent in the vertical axis. As will be apparent to the skilled person, the mid camber in the sail as disclosed herein, at 100% cunningham load, is at about 6.2% while the corresponding value in the prior art sail is at about 8.3%. In other words, the sail disclosed herein exhibits a lower mid-camber at a high cunningham load and a higher camber at a low cunningham load.

[0132] The above concepts can be applied to a range of sail shapes. For example, as shown in FIG. 11, they can be applied to a sail with more of a rectangular or quadrilateral shape comprising a mast 2, elastic region 18 and stiffer material 19. The above concepts could also be applied to twin skin sails as shown in FIG. 6. It will be understood by the skilled person that in case of a twin skin sail, the sail has two luff regions, one in each of the two skins defining the twin sail. In this embodiment, each of the two luff regions has elastic properties in relation to the respective remainder of the sail that make the luff region less stiff in the luff direction than the remainder of the sail

[0133] Among other things, the above novel configurations provide an advantage in that the sail according to the present disclosure may be able to change its shape and to adjust to changes in the wind pressure or heading of the yacht relative to the wind direction.

[0134] Further, it has been found that some embodiments of the sail disclosed herein are typically lighter than a comparable prior art sail. The reason for this may be that the reduction in stiffness in the luff region may be achieved by a thinner material in this region, or by the absence of certain load bearing fibres in the direction parallel to the luff, as explained above. The saved material typically results in a lighter sail.

[0135] Moreover, in some situations, for example in yacht racing, a fixed weight of a sail is prescribed. In this case, the sail disclosed herein is advantageous over prior art sails in that the weight savings in the luff region allow for the allocation of more weight (and hence more material and stiffness) to areas of the sail where a higher stiffness is desirable to reduce stretch. These areas are typically in the body or centre of the sail where the bulk of the wind load is transferred to the head, clew and tack

[0136] Although embodiments have been described with reference to a number of illustrative embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the preferred embodiments should be considered in a descriptive sense only and not for purposes of limitation, and also the technical scope of the invention is not limited to the embodiments. Furthermore, the present invention is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being comprised in the present disclosure.

[0137] Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention as herein described with reference to the accompanying drawings.