WO2022064195A1

WO2022064195A1 - A wing sail for a wing propelled craft

Info

Publication number: WO2022064195A1
Application number: PCT/GB2021/052466
Authority: WO
Inventors: Gregory Owen Johnston
Original assignee: Advanced Wing Systems Limited
Priority date: 2020-09-22
Filing date: 2021-09-22
Publication date: 2022-03-31

Abstract

The present invention relates to a wing sail (100) having a leech (102) and a luff (101) defining a first direction therebetween, the wing sail (100) comprising: first and second sail portions (110, 120), wherein the first sail portion (110) comprises a first sail portion luff (111) and a first sail portion leech (112), wherein the second sail portion (120) comprises a second sail portion luff (121) and a second sail portion leech (122), wherein the first sail portion luff (111) and the second sail portion luff (121) are spaced apart from each other in a direction transverse to the first direction to define a thickness of the wing sail (100); a first batten (130) in contact with the first sail portion (110), the first batten (130) extending from a first batten luff end (131) to a first batten leech end (132), wherein the first batten luff end (121) is proximal to the first sail portion luff (111) and the first batten leech end (132) is proximal to the first sail portion leech (112); and a first tension element (150) extending from a first luff connection (151) to a first leech connection (152), wherein the first luff connection (151) is proximal to the first batten luff end (131) and the first leech connection (152) is proximal to the first batten leech end (132), such that on tensioning of the first tension element (150), the first tension element (150) draws the first leech connection (152) directly towards the first luff connection (151) thereby bending the first batten leech end (132) towards the first batten luff end (131) to change the shape of the first sail portion (110).

Description

A Wing Sail for a Wind Propelled Craft

Field of the Invention

The present invention relates to a wing sail for wind propelled craft. In particular, the present invention relates to controlling camber and thickness in a wing sail. Camber refers to curvature of the sail and is generally defined as the maximum depth of a section of sail in the direction of the flow expressed as a percentage of the chord length of the sail at that particular section. The chord length of the sail is the length between the leading edge (luff) and the trailing edge (leech) of the sail.

The apparatus of the present invention will hereinafter be described with particular reference to wind propelled craft being sailing vessels such as sailing dinghies, sailing catamarans, or sailing keel boats. However, it is understood that the apparatus is of general applicability.

Background of the Invention

Wing sails are also described as twin-skin sails/double skin sails in the art. Wing sails employ two sail portions that are typically substantially identical, each having a luff (a front edge towards the bow or front of the craft) and a leech (a trailing edge towards the stem or rear of the craft). The two sail portions are typically secured to the mast along their luff and the two sail portions are secured together at their leech. Wing sails may have a rigid construction (i.e. the sail portions are formed of a rigid material) that are only stowed upon removal from the boat (i.e. they cannot be furled). Alternatively, wing sails may have a soft construction (i.e. the sail portions may be formed of a flexible material) such that they can be furled and stored on board.

Sails or aerofoils create lift by the action of a differing air velocity from one side of the sail to the other. Stagnation of the air at the luff or mast (i.e. the leading edge of the sail) on the windward side of the sail, along with the shape of the aerofoil section, creates an asymmetry in the air path from the windward to the leeward sides of the sail or aerofoil. Consequently, given that other aerodynamic conditions are satisfied regarding the joining of the flow streams downwind of the sail or aerofoil, this asymmetry creates increases the speed of the air on the leeward side relative to the windward side and hence a pressure difference between the leeward and windward sides. This pressure differential results in aerodynamic lift. It is this lifting force which then propels the vessel. At the same time, the sail or aerofoil also produces aerodynamic drag, which when sailing upwind, for example, can reduce the force which propels the vessel. Hence it is desirable for wind propelled vessels to be able to produce relatively high lift and relatively low drag, particularly for sailing with the wind forward of the beam of the vessel.

While the rigid and/or thick asymmetrical wing sails used on vessels such as the recent 35^th America’s Cup catamarans and other high-performance sailing craft can provide very good lift and drag characteristics, these wing sails have practical limitations. These wing sails are constructed to be light weight and rigid. As discussed above, such rigid wing sails cannot be collapsed for easy storage. Further, they cannot be reefed or stowed when sailing if it is desirable to have less sail area. These wing sails are also generally quite fragile and can be easily damaged in the event of a capsize or collision.

The 36^th America’s Cup will use soft wing sails to provide a more efficient sail configuration. The configuration and control of these sails will be limited by the rules of the event and this will impose limitations on the control methods employed.

According to sources involved in the development of the rules for the 36^th America’s Cup, the soft wing sails will use a “D Mast” configuration (i.e. a mast having a leading edge that defines a convex surface and a trailing edge that defines a flat surface) with two sails hoisted behind it much as proposed by Herreshoff in 1927 and described in US1613890A.

The inventor's previous patent, EP3052379B1, describes an arrangement where the battens are pivotally connected to a respective port side or starboard side of the mast and rotation of the mast causes the batten of one sail portion to be compressed and the batten of the other sail portion to be tensioned so as to change the shape of the aerofoil formed by the sail. The leech ends of the sail portions are connected together by, for example, a tie, such that movement of one leech end relative to the other leech end is limited. Control lines running inside the batten pocket and connected to the luff of the respective sail portion may be employed to bring the leech ends closer together to change the spacing between the sail portions and so thickness of the wing sail. The control lines do not exert a bending force on the battens and do not bend the leech end of the battens towards the respective luff ends of the battens. Another invention from the inventor of the present application is described in AU1986052399 and US4,766,831 where the luff of each sail portion is pivotally attached to a control rod rotatably attached to the boom such that angular displacement of the control rod with respect to the boom using a lever causes a corresponding rotation of the control rod and an opposite rotation of the mast. This is turn causes a batten of one sail portion to be compressed and the batten of the other sail portion to be tensioned. Notably the leeches of the sail portions are connected together.

Inducing opposite cambers in the head or top part of that sail to those in the bottom or foot part of the sail is desirable to control heeling of the wind propelled craft. The reason behind this is that the opposite cambers in the head of the sail create an aerodynamic force which assists in keeping the boat upright. For this force to be generated it is desirable that the top part of the sail has a very low, or even negative angle of attack to the wind relative to the bottom of the sail, thus creating an aerodynamic force in substantially the opposite direction. Opposite cambers refers to an arrangement where the bottom half of the sail is shaped such that the camber is on the opposite side of the chord line to the camber of the top part of the sail. In other words, the curvature of the top part of the sail is inverted relative to the curvature of the bottom portion of the sail.

A challenge for the designers of wing sails using a “D Mast” configuration is producing a design which allows the cambers to be reversed/inverted along the span of the sail or wing (i.e. from bottom to top of the sail) such that the bottom and top parts of the sail or wing have opposite cambers. Recent attempts to do this have being only marginally successful. It would appear from analysis of the videos released by ETNZ that sails with substantially conventional shapes are being used. That is, the sails have cambers formed into the shape of the sail, either by moulding or by the common practice of broadseaming.

A limitation of this design is once the cambers, or shape, is designed into the sail it is difficult to change that shape without introducing stress creases in the sails. As such, the ability to change the shape of such sails is limited. The common practice of broadseaming restricts the ability to induce inverted cambers. Reversing the cambers along the span of the sail would be very difficult without pre-shaping the sail to have opposite cambers. This again limits the range of shapes that can be achieved.

Given the 36^th America’s cup will be sailed in high performance yachts which employ hydrofoils to reduce hydrodynamic drag, such vessels need a wide dynamic range of performance in the sails used such that high lift wing sections can be created for lower speed sailing while the vessel makes the transition from non-foiling to foiling mode. Once foiling, lower lift and also much lower drag sections are desirable, as it the ability to reduce heeling moments by creating opposite cambers and angle of incidence to the wind at the top of the sail.

Thus, sails with substantial pre-shaping in terms of cambers will be problematic in providing the required dynamic range of shapes.

It is also desirable to be able to control "twist" of the sail. Twist refers to a difference in attack angle in the top part of the sail compared to the bottom part of the sail. Twist promotes airflow over the sail in light winds and depowers the sail in heavy winds. A video release by ETNZ has shown the use of a rigid control spar/pole at the topmost part of the sail which can be used to force the upper portions of the sail to adopt a substantially different angle relative to the wind compared to the bottommost sections. This method of controlling the “twist” in the sail and to induce inverted cambers can afford the ability to create the desired opposite angle of incidence in the upper portions of the sail but is hindered by the issues relating to reversing cambers noted above.

Summary of the Invention

The present invention provides a wing sail having a leech and a luff defining a first direction therebetween, the wing sail comprising: first and second sail portions, wherein the first sail portion comprises a first sail portion luff and a first sail portion leech, wherein the second sail portion comprises a second sail portion luff and a second sail portion leech, wherein the first sail portion luff and the second sail portion luff are spaced apart from each other in a direction transverse to the first direction to define a thickness of the wing sail; a first batten in contact with the first sail portion, the first batten extending from a first batten luff end to a first batten leech end, wherein the first batten luff end is proximal to the first sail portion luff and the first batten leech end is proximal to the first sail portion leech; and a first tension element extending from a first luff connection to a first leech connection, wherein the first luff connection is proximal to the first batten luff end and the first leech connection is proximal to the first batten leech end, such that on tensioning of the first tension element, the first tension element draws the first leech connection directly towards the first luff connection thereby bending the first batten leech end towards the first batten luff end to change the shape of the first sail portion.

Such a wing sail is advantageous as it enables control of camber and/or thickness of a wing sail without relying on rotation of the mast. As the wing sail does not rely on rotation of the mast to induce camber, when rigged with a mast, the mast can rotate towards the wind to provide an aerodynamically smooth leading edge to the aerofoil while camber is induced. Furthermore, the mast can be rotated somewhat independently of the induced camber thus providing a further degree of tuning of the aerodynamic shape of the sail. This is in contrast to the inventor's previous patents, EP3052379B2 and US4766831 A, where camber was induced by rotation of the mast. It is noted that the control lines described in EP3052379B2 adjust the spacing between the leech ends of the batten and so the thickness of the wing sail. In particular, the present invention enables control of camber in a wing sail rigged with a "D" shaped mast. Furthermore, it is possible to induce a greater amount of camber according to the present invention as such camber is not limited by the rotation of the mast.

The sail portions may be flexible. The sail portions may be flexible such that they can be furled and stored on-board. The sail portions may be substantially flat prior to use such that there is no or minimal precambered shape formed into the sail portions (i.e. less than a few percentage points of the length of the batten or sail chord). For example, the sail portions may be substantially flat panels having a curvature of less than 1-2% in any direction when not attached to the mast and when the first and second tension elements are slack. Accordingly, each sail portion can adopt a shape of camber using the tension elements without the introduction of stresses which result in substantial creases and local deformations in the surface of the sail portion.

The first tension element when tensioned exerts a bending force on the first batten, the first batten being configured to bend under the bending force. The bending of the first batten is such that the first batten leech end is drawn towards the first batten luff end.

On applying tension to the first tension element, a compressive force is exerted on the first batten causing the first batten to bend.

The wing sail may also comprise: a second batten in contact with the second sail portion, the second batten extending from a second batten luff end to the second batten leech end, wherein the second batten luff end is proximal to the second sail portion luff and the second batten leech end is proximal to the second sail portion leech; and a second tension element extending from a second luff connection to a second leech connection, wherein the second luff connection is proximal to the second batten luff end and the second leech connection is proximal to the second batten leech end, such that on tensioning of the second tension element in use, the second tension element draws the second leech connection towards the second luff connection thereby bending the second batten leech end towards the second batten luff end to change the shape of the second sail portion, wherein the first and second tension elements are optionally separately controllable.

The second tension element when tensioned exerts a bending force on the second batten, the second batten being configured to bend under the bending force. The bending of the second batten is such that the second batten leech end is drawn towards the second batten luff end.

Each sail portion may employ multiple tension elements extending between a respective luff connection and a respective leech connection to respectively control the bending of a plurality of battens.

Each tension element may be tethered to the respective luff connection and the respective leech connection.

By employing tension elements in both of the sail portions that are separately controllable, a wider range of sail shapes are possible. Both the thickness and camber (curvature) of the wing sail (aerofoil formed by the wing sail) may be adjusted by separately controlling the curvature of the first and second sail portions (i.e. the windward and leeward sail portions). For example, both sail portions may be brought into compression. Alternatively, in use, the tension applied to the first tension element may be increased and the tension applied to the second tension element may be reduced such that the first batten is compressed more and its curvature increased compared to the second batten which is compressed less and consequently less curved. By differentially tensioning the first and second battens, an asymmetric shape (i.e. an aerofoil) is formed where one sail portion has relatively less camber (less curvature) than the other sail portion. It may be advantageous for the windward batten to have less curvature than the leeward batten such that the aerofoil formed is aerodynamically desirable. The first tension element and the second tension element (when present) may be arranged inside the wing sail. Accordingly, the luff, leech and/or twist connections may also be arranged inside the wing sail, for example on the inner surfaces of the respective sail portion or on the respective batten or pocket. Each batten and pocket may extend along an inner surface of the respective sail portion.

Optionally, the tension elements and the first and second battens are arranged in an upper half or a top part or head of the respective sail portion. For example, the tension elements and the first and second battens may be positioned in the upper 50%, 40%, 30%, 20% or 10% of the respective sail portion. The tension elements and the first and second battens may be arranged proximal to the uppermost edge (head) of the respective sail portions. The tension elements may be positioned in the upper half of the respective sail portion such that the camber in the upper half of the tension elements is controlled by the tension elements and the camber in the lower half of the respective sail portion is otherwise controlled, for example by the outhaul and wind loads. In such an arrangement, opposite camber may be induced in the upper half of the wing sail compared to the camber induced in the lower half of the wing sail. Alternatively, the first and second tension elements may form a first pair of tension elements and the first and second battens may form a first pair of battens and the wing sail may comprise a further pair of tension elements and a further pair of battens similarly configured. The first pair of tension elements, first pair of battens and respective connections may be arranged in the upper half or a top part or head of the wing sail and the second pair of tension elements, second pair of battens and respective connections may be arranged in the lower half or bottom part of the wing sail. The first pair of tension elements may be separately controllable from the second pair of tension elements such that the camber/curvature in the upper half may be separately controlled from the curvature/camber in the lower half of the wing sail. In such an arrangement, opposite camber may be induced in the upper half/part of the wing sail compared to the camber induced in the lower half/part of the wing sail. The camber in the upper half/part of the wing sail may be induced using a single pair of tension lines coupled to a single batten pair and so the remaining batten pairs in the upper half/part of the sail may not have tension lines coupled thereto. Similarly, the camber in the lower half/part of the wing sail may be induced using a single pair of tension lines coupled to a single batten pair and so the remaining batten pairs in the lower half/part of the sail may not have tension lines coupled thereto. The wing sail may comprise a plurality of pairs of battens, one or more of the plurality of batten pairs having a pair of tension elements coupled thereto.

Opposite camber refers to opposite curvature. For example, if in the bottom part of the sail, the windward battens are in tension and the leeward battens are in compression (either by use of a further pair of tension elements to bend a further pair of battens or due to control of the out haul), then the tension elements in the upper half/part of the wing sail may be used to, for example, bring the windward batten(s) into compression and leeward batten(s) into tension in the upper half/top part/head of the sail.

As the sail portions are substantially flat and so have no or minimal precambered shape formed into the sail portion, each sail portion can adopt a shape cambered in one direction at the bottom part of the sail that is opposite to the camber in the top part of the sail without the introduction of stresses which result in substantial creases and local deformations in the surface of the sail portion.

The first tension element typically forms a straight line between the first luff connection and the first leech connection when tensioned.

The second tension element typically forms a straight line between the first luff connection and the first leech connection when tensioned.

The luff connections are described as being proximal to the respective batten luff end and the leech connections are described as being proximal to the respective batten leech end. "Proximal to" as used herein refers to at or near. For example, the luff connection is at or near the respective batten luff end and the leech connection is at or near the respective batten leech end. The luff connection may be within a radius of the respective batten luff end, the radius being less than 20%, optionally less than 10%, optionally less than 5% of the length of the batten. The length of the batten is the distance from the luff end to the leech end of the batten. Similarly, the leech connection may be within a radius of the respective batten leech end, the radius being less than 20%, optionally less than 10%, optionally less than 5% of the length of the batten. The length of the batten being the distance from the luff end to the leech end of the batten.

The first tension element may be directly or indirectly coupled or connected to the first batten luff end via the first luff connection proximal to the first batten luff end and directly or indirectly coupled or connected to the first batten leech end via the first leech connection. The second tension element may be similarly configured. For example, the luff and/or leech connections may be arranged on the respective batten such that the tension element is directly coupled to the batten.

Alternatively, the luff and/or leech connections may be arranged adjacent to the respective batten, such as on the respective sail portion or on a pocket configured to receive the respective batten such that the tension element is indirectly coupled to the batten. The luff and/or leech connections may be arranged on a fitting attached to the respective batten or sail portion such that the tension element is indirectly coupled to the respective batten. For example, the luff connection may be provided on or in a fitting configured to couple the luff end of the respective batten to the mast (the luff box). In an arrangement where the wing sail is rigged with a mast, the tension element may be indirectly coupled to the luff end of the batten as the luff connection(s) may be arranged on a region of the mast proximal to the luff end of the respective batten.

In any arrangement, movement of the tension element through the respective luff connection or movement of the luff connection due to tensioning of the tension element causes the luff end of the respective batten to be drawn towards the leech end of the respective batten. Similarly, movement of the tension element through the respective leech connection or movement of the leech connection due to tensioning of the tension element causes the leech end of the respective batten to be drawn towards the luff end of the respective batten.

The leech connections and/or luff connections may be fixed connections, i.e. such that at the connections the tension element does not move relative to the respective batten, sail portion and/or pocket. The luff and/or leech connections may be receiving portions configured to attach to or be attached to the tension element. The luff and/or leech connections may be protrusions to which the tension element is affixed or tied and/or may be points on the respective batten, sail portion and/or pocket to which the tension element is attached, for example, with stitching, tape, adhesive or other mechanical fastening. The luff connections may be points on the mast to which the tension element is attached, for example, with stitching or tape, adhesive or other mechanical fastening. The luff and/or leech connection may be fixed points within a fitting attached to the respective sail portion/batten.

Alternatively, the luff and/or leech connections may not be fixed connections. For example, the luff and/or leech connections may be receiving portions or openings in, for example, the respective sail portion, pocket and/or batten. The luff and/or leech connections may be receiving portions or opening in a fitting attached to the respective sail portion/batten. The tension element may be received through and pulled through such opening or receiving portion to apply tension to the tension element and draw the connections together thereby bending the batten. The opening or receiving portion may be a loop, eyelet, channel or through-hole, or any other means of deflecting and/or receiving the tension element.

Optionally, at least one of the first luff and first leech connections is a fixed connection. Similarly, optionally, at least one of the second luff and second leech connections is a fixed connection.

Optionally, one of the first connections (i.e. first luff or first leech connections) is a fixed connection and one of the first connections is not fixed such that the first tension element may be movable through the non-fixed first connection such that on tensioning the first tension element, the length of the first tension element between the first luff and leech connections is reduced.

Similarly, in an optional arrangement, one of the second connections (i.e. second luff or second leech connections) is a fixed connection and one of the second connections is not fixed such that the second tension element may be movable through the non-fixed second connection such that on tensioning the second tension element, the length of the second tension element between the second luff and leech connections is reduced.

Optionally, at least one of the second luff and second leech connections is a fixed connection.

Each luff connection may be a fixed connection and each leech connection may not be a fixed connection. Each tension element may be moveable through the respective leech connection such that on tensioning each tension element, the length of each tension element between the respective luff and leech connections is reduced and each leech connection is moved towards the corresponding luff connection.

Alternatively, each luff connection may not be a fixed connection and each leech connection may be a fixed connection. Each tension element may be moveable through the respective luff connection such that on tensioning each tension element, the length of each tension element between the respective luff and leech connections is reduced and each leech connection is moved towards the luff connection. The luff connection and the leech connections may both be fixed connections and the middle of the tension element may be pulled to apply tension thereto.

Optionally, the first tension element may also extend from the leech connection proximal to the first batten leech end to a separator connection arranged proximal to the second batten such that on tensioning the first tension element in use, the first tension element also moves the leech of the first batten towards the luff of the second batten thereby inducing a torque between the first and second battens which are laterally separated along the mast. The separator connection proximal to the second batten may be closer to the second batten than the first batten.

The connection of the first tension element to the separator connection may keep the first batten leech end and the second batten leech end coupled together laterally. The separator connection may be positioned between the second sail portion leech and the second sail portion luff. The separator connection may be positioned closer to the luff of the second sail portion than the leech. The separator connection may be positioned closer to the leech of the second sail portion than the luff. The separator connection may be proximal to the leech or the luff of the second sail portion.

The first tension element may be directly or indirectly coupled or connected to the second batten via the separator connection.

For example, the separator connection may be arranged on the second batten such that the first tension element is directly coupled to the batten via the separator connection. Alternatively, the separator connection may be arranged adjacent to the second batten, such as on the second sail portion or on a pocket configured to receive the second batten. The separator connection may be arranged on a fitting attached to the second batten or to the second sail portion such that the first tension element is indirectly coupled to the second batten. For example the separator connection may be provided on or in a fitting configured to couple the luff end of the second batten to the mast (the luff box for the second batten). In an arrangement where the wing sail is rigged with a mast, the first tension element may be indirectly coupled to the second batten as the separator connection may be arranged on a region of the mast proximal to the second batten.

Similarly to the luff and leech connections, the separator connection may be a fixed connection i.e. such that at the connection the tension element does not move relative to the second batten, second sail portion and/or pocket of the second batten. The separator connection may be a receiving portion configured to attach to or be attached to the first tension element. For example, the separator connection may be a protrusion to which the first tension element is affixed or tied. The separator connection may be a point on the second sail portion, second batten and/or pocket receiving the second batten. The separator connection may be a point on the mast proximal to the second batten or a point within a fitting attached to the second batten or second sail portion. The separator element may be attached to the point forming the separator connection with, for example, stitching, tape, adhesive or other mechanical fastening.

Alternatively, the separator connection may not be a fixed connection. For example, the separator connection may be a receiving portion or opening in, for example, the second sail portion, second batten and/or pocket receiving the second batten. The separator connection may be a receiving portion or opening in a fitting attached to the second sail portion and/or second batten. The separator connection may be a receiving portion or opening arranged on a region of the mast proximal to the second batten. In use, the tension element may be received through and pulled through such opening or receiving portion to apply tension to the tension element. The opening or receiving portion may be a loop, eyelet, channel or through-hole.

The tension element may extend from the leech end to the separator connection via one or more pulleys.

The separator connection proximal to the second batten is referred to herein as the second separator connection. In a similar arrangement, the second tension element may extend from the leech connection proximal to the second batten leech end to a separator connection arranged proximal to the first batten such that on tensioning the second tension element in use, the second tension element also rotates the second batten relative to the mast. The separator connection proximal to the first batten is referred to as the first separator connection herein and may be configured similarly to the second separator connection as discussed above except that the first separator connection is proximal to the first batten rather than the second batten.

The luff connection of the first sail portion may be fixed, the leech connection of the first sail portion and the second separator connection may be configured such that the tension element is movable therethrough. Therefore, in use on applying tension to the first tension element, the tension element is drawn from the luff connection, through the leech connection, towards and through the second separator connection such that the leech connection is drawn towards the luff connection and towards the second separator connection. This causes the first batten to be bent towards its luff end and drawn towards the second batten thereby reducing the separation between the first and second battens. In such an arrangement the leech connection of the first sail portion may be, for example, an opening or receiving portion. The opening or receiving portion may be a loop, eyelet, channel or through-hole. The opening or receiving portion may be formed in any mechanical fixture. The opening or receiving portion may be arranged in the first sail batten, in the pocket that receives the first sail batten and/or in a fitting attached to the first sail batten or first sail portion.

The invention also provides a rigging comprising: a mast; and the wing sail described above, wherein the first sail portion and the second sail portion are each mounted to the mast.

The mast may comprise a leading edge and a trailing edge defining the first direction therebetween and a second direction transverse to the first direction.

The leading edge of the mast is the front edge of the mast and the trailing edge of the mast is the rear edge of the mast.

The sail portions may be mounted to the trailing edge of the mast.

Each sail portion may be slidable along the length of the mast to reef and hoist the sail.

The luff of the sail portions may be mounted at the trailing edge of the mast. In particular, the sail portions may be mounted to the trailing edge of the mast via their batten luff ends. In particular, the batten luff ends may be pivotally mounted to the trailing edge of the mast such that the battens can rotate relative to the mast.

The luff of the first sail portion may be spaced apart from the luff of the second sail portion along the trailing edge of the mast or may be arranged on either sides of the mast.

Optionally, the mast is D-shaped, i.e. shaped such that the leading edge defines a convex surface and the trailing edge defines a flat surface. Accordingly, the mast can be rotated towards the wind during use which provides an aerodynamically smooth leading edge to the aerofoil.

The rigging may comprise a boom pivotally mounted to the mast at one end and coupled to the leech of the sail portions at the other end such that the boom can rotate relative to the mast. The first sail portion may be coupled to a first side of the boom and the second sail portion may be coupled to a second side of the boom, Alternatively, the first and second sail portions may be mounted on an upper surface of the boom. The boom has a length extending in the first direction of the wing sail (i.e. from luff to leech). The boom may be mounted to the upper half or the lower half of the mast. The boom may be mounted to the mast using a gooseneck and the first and second sail portions may be coupled to the boom using clews.

The boom may be controllably articulated between its ends. One or more boom arms, such as lever arms or quadrant arms, may extend laterally from the boom (lateral is transverse to the length of the boom). A first boom arm may extend from the first side of the boom and a second boom arm may extend from the second side of the boom such that the first and second arms extend outwardly from the wing sail. The first tension element may lead from the luff connection to a first boom connection arranged on the first boom arm such that an angular change between the mast and the boom causes the first arm to apply tension to the first tension element so as to induce tension between the luff connection and the leech connection. The first boom connection may be a fixed connection. Similarly, the second tension element may lead from the luff connection to a second boom connection arranged on the second boom arm. The second boom connection may be a fixed connection such that an angular change between the mast and the boom causes the second arm to apply tension to the second tension element so as to induce tension between the luff connection and the leech connection. In such an arrangement, the tension applied to the respective tension element increases or decreases depending on the direction and magnitude of the angular displacement between the boom and the mast.

In an arrangement, a clockwise angular displacement between mast and boom when viewed from the top of the wing sail results in the tension element on the port sail portion to be tensioned and the tension element on the starboard sail portion such to be loosened, thus causing the sail portions at the top of the sail to twist in an opposite direction to the angular displacement between the mast and the boom at the bottom of the sail. An anticlockwise angular displacement would have a correspondingly opposite effect. In embodiments comprising a boom, the first separator connection described above may be provided on the boom where the second sail portion is attached. Similarly, the second separator connection described above may be provided on the boom where the first sail portion is attached.

There is also provided a method of using the wingsail or rigging or wind propelled craft described above, the method comprising: applying tension to the first tension element to bend the leech end of the first batten towards the luff end of the first batten to thereby change the shape of the first sail portion.

The method may further comprise applying tension to the second tension element to bend the leech end of the second batten towards the luff end of the second batten to thereby change the shape of the second sail portion, wherein optionally the tension applied to the second tension element is different from the tension applied to the first tension element.

The invention also provides a rigging comprising: a mast having a leading edge and a trailing edge defining a first direction therebetween and a second direction transverse to the first direction; a wing sail having a leech and a luff, wherein the wing sail is pivotally attached to the mast and comprises: first and second sail portions, each having a leech and a luff, wherein the first sail portion luff and the second sail portion luff are spaced apart from each other in the second direction transverse to define an effective thickness of the wing sail; a first batten in contact with the first sail portion, the first batten extending from a first batten luff end to a first batten leech end, wherein the first batten luff end is proximal to the first sail portion luff and the first batten leech end is proximal to the first sail portion leech; and a rigid first stop extending along and coupled at the first batten luff end and extending at least partially across the thickness of the wing sail, wherein the first stop is configured such that when the mast is rotated in a first rotational direction, the first stop abuts the mast and exerts a bending force on the first batten, to thereby change the shape of the first sail portion.

Such an arrangement is advantageous because the batten is bent/curvature is induced in the same direction as the mast direction thereby maintaining an aerodynamically smooth attachment of the batten to the mast.

The mast may comprise a leading edge and a trailing edge. Optionally, the wing sail may be pivotally attached to the trailing edge of the mast. Optionally, the first sail portion luff and the second sail portion luff are spaced apart along the trailing edge of the mast or are arranged on either sides of the mast.

Such an arrangement is therefore particularly advantageous in the embodiment where the mast is D-shaped (i.e. where the leading edge defines a convex surface and the trailing edge defines a flat surface). The trailing edge of the mast may also be referred to herein as the rear face of the mast.

Optionally, the first stop may abut a portion of the mast when the mast is rotated in the first rotational direction.

Optionally, the first stop may abut the trailing edge of the mast when the mast is rotated in the first rotational direction.

The wing sail may optionally further comprise a second batten in contact with the second sail portion, the second batten extending from a second batten luff end to a second batten leech end, wherein the second batten luff end is proximal to the second sail portion luff and the second batten leech end is proximal to the second sail portion leech; and a rigid second stop extending along and coupled at the second batten luff end and extending at least partially across the thickness of the wing sail, wherein the second stop is configured such that when the mast is rotated in a second rotational direction, which is opposite from the first rotational direction, the second stop abuts the mast and exerts a bending force on the second batten, to thereby change the shape of the second sail portion.

Typically the wing sail is mounted to the mast at the luff ends of the first and second battens. For example, the luff end of each batten may be pivotally mounted to the mast such that the battens can rotate relative to the mast.

Optionally, the second stop may abut a portion of the mast when the mast is rotated in the second rotational direction.

Optionally, the second stop may abut the trailing edge of the mast when the mast is rotated in the second rotational direction. The first stop and/or the second stop are typically rigid such that the first and second stop do not deform on rotation of the mast such that the bending force from rotation of the mast is exerted on the respective batten. In other words, the first stop and/or the second stop are rigid such that the first stop and the second stop do not deform under normal forces in use in this application to any degree that affects its function. The first stop and/or second stop may be formed of, for example, a rigid plastic or metal.

The first stop may be configured such that a separation between the first stop and the trailing edge of the mast increases on rotation of the mast in a second rotational direction, which is opposite from the first rotational direction. Similarly, the second stop may be configured such that a separation between the second stop and the trailing edge of the mast increases on rotation of the mast in the first rotational direction. This functionality is enabled as the first stop is rigidly coupled to the first batten but not to the mast and similarly the second stop is rigidly coupled to the second batten but not to the mast. In other words, each stop is only coupled to the mast via the respective batten (i.e. the first stop is not coupled directly to the mast but is instead coupled to the mast via the first batten and the second stop is not coupled directly to the mast but is instead coupled to the mast via the second batten). This is advantageous as the windward batten can move away from the trailing edge of the mast on rotation of the mast such that less camber is induced in the windward batten than the leeward batten thereby producing the asymmetric aerofoil shape that is aerodynamically desirable.

The first stop may be rigidly coupled to the first batten luff end such that a fixed point on the first stop does not move relative to a fixed point on the first batten luff end. Similarly, the second stop may rigidly coupled to the second batten luff end such that a fixed point on the second stop does not move relative to a fixed point on the second batten luff end.

The first stop and/or the second stop are within the wing sail i.e. extend from the respective batten luff end into the cavity formed by the first and second sail portions.

The first stop may have a first abutting edge extending across a section of the thickness of the wing sail (i.e. from the first batten luff end towards the second batten luff end) and a first coupling edge extending along and coupled to a portion of the length of the first batten luff end. In this arrangement, the portion of the first stop that is configured to abut the mast is a portion of the first abutting edge. The coupling edge may be rigidly coupled to the portion of the length of the first batten luff end such that the coupling edge does not move relative to the portion of the length of the first batten luff end. In such an arrangement, the point about which the first batten bends is at the distal end of the first coupling edge (i.e. the end of the couphng edge distal from the mast). Similarly, the second stop may have a second abutting edge extend across a section of the thickness of the wing sail (i.e. from the second batten luff end towards the first batten luff end) and a second coupling edge extending along and coupled to a portion of the length of the second batten luff end. The second coupling edge may be rigidly coupled to the portion of the length of the second batten luff end such that the second coupling edge does not move relative to the portion of the length of the second batten luff end. In such an arrangement, the point about which the second batten bends is at the distal end of the second coupling edge (i.e. the end of the second coupling edge distal from the mast).

The abutting edges of the first stop and the second stop may overlap.

The first stop and/or the second stop may be configured such that the abutting edge may be at an angle of 70-100°, preferably substantially perpendicular, to the coupling edge.

The first and/or second stop may be configured such that they do not initially abut the trailing edge of the mast. The first stop may be configured to abut the trailing edge of the mast on rotation of the mast from an initial position through a first threshold angle in the first rotational direction and wherein further rotation of the mast beyond the first threshold angle exerts the bending force on the first batten to thereby change the shape of the first sail portion. The second stop may be configured to abut the trailing edge of the mast on rotation of the mast from an initial position through a second threshold angle in the second rotational direction and wherein further rotation of the mast beyond the second threshold angle exerts the bending force on the second batten to thereby change the shape of the second sail portion.

The first and/or second threshold angle may be determined by, respectively, the length of the first or second abutting edge and the angle between the first or second abutting edge and the first or second coupling edge.

The first and/or second stop may be configured such that the first and/or threshold angle is/are less than 90°. For example, the first and/or second threshold angles may be less than 70°, less than 50°, less than 30°, less than 20°, less than 10° or less than 5°. Alternatively, the first stop and/or the second stop may be configured to initially abut the trailing edge of the mast (i.e. the first and second threshold angles being 0°).

The first stop and/or the second stop may be located at the luff of each of the battens in a batten pair, respectively, such that they extend laterally from the luff of the respective sail portions (in a plane substantially in the same plane as the cross section of the mast) and extend inwards substantially perpendicular to the luff so that when the mast is rotated the first stop or the second stop contacts the rear face of the mast and a bending moment is applied to the batten to camber the batten in the same direction as the mast rotation and to maintain an aerodynamically smooth attachment of the batten to the mast.

Optionally, the first stop and the second stop are coupled together by a linking element that restricts movement of the first stop relative to the second stop beyond an upper limit, such that (i) rotation of the mast in the first rotational direction causes the second stop to move relative to the first stop such that a separation between the second stop and the trailing edge of the mast increases until the upper limit is reached and further rotation of the mast exerts a bending force on the first and second batten to thereby change the shape of the first and second sail portions; and (ii) rotation of the mast in the second direction causes the first stop to move relative to the second stop such that a separation between the first stop and the trailing edge of the mast increases until the upper limit is reached and further rotation of the mast exerts a bending force on the first and second battens to thereby change the shape of the first and second sail portions.

The linking element therefore may not initially restrict movement of the second stop relative to the first stop such that the leeward batten can camber/curve less than the windward batten. However, at increased mast rotation and so increased displacement between the first and second stops, the upper limit is reached that restricts further displacement between the first and second stops thus increasing camber/curvature in both the leeward and windward battens with further mast rotation.

The movement restricted by the linking element may be rotation of the first and second stops relative to each other. The linking element may comprise, for example, complementary engagement means that are slidably coupled. For example, the linking element may comprise a receiving a portion such as slot, groove or channel in one of the stops and a protrusion extending from the other stop that is configured to be received within the receiving portion. The movement of the protrusion within the receiving portion may be restricted by the length of the receiving portion. Accordingly, the length of the receiving portion may be selected according to the upper limit. The linking element may be a mechanical actuator that restricts the angular displacement between the first and second stops.

The upper limit may be an angle between the range of, for example, 5-30°.

Optionally, the first stop and/or the second stop extend substantially in the same plane as the cross section of the mast, optionally perpendicular to the luff of the respective sail portion.

Optionally, the first stop and/or the second stop are formed as plates or frames. The first stop and/or the second stop may be planar and extend in the same plane as the cross section of the mast.

The first stop and/or the second stop may extend laterally from the luff of the sail portions such that they extend inwards substantially perpendicular to the luff.

Each sail portion may employ multiple pairs of first stops and second stops to respectively control the bending of the multiple pairs of first and second battens. The first pair of stops and first pair of battens may be arranged in the upper half or top part or head of the wing sail and the second pair of stops and second pair of battens may be arranged in the lower half or bottom part of the wing sail.

The present invention also provides a method of using the rigging described above, the rigging comprising a wing sail, which in turn comprises at least a first stop, wherein the first sail portion is the leeward sail portion and the second sail portion is the windward sail portion, the method comprising: rotating the mast in a first rotational direction such that at least a portion of the first stop abuts the trailing edge of the mast and a bending force is exerted on the first batten, to thereby change the shape of the first sail portion.

The features and methods relating to the wing sail having a first tension element exerting a bending force on the first batten can be combined with the rigging having the first stop. The first and second stops can be employed to induce curvature in the respective battens and further curvature can be obtained using the first and/or second tension elements. The luff connection proximal to the first batten luff end may be arranged on the first stop and the luff connection proximal to the second batten luff end may be arranged on the second stop. The present invention also provides a rigging comprising a mast having a trailing edge and a leading edge defining a first direction therebetween and a second direction transverse to the first direction; and a wing sail mounted to the mast, the wing sail having a leech and a luff, the wing sail comprising: first and second sail portions, wherein the first sail portion comprises a first sail portion luff and a first sail portion leech, wherein the second sail portion comprises a second sail portion luff and a second sail portion leech, wherein the first sail portion luff and the second sail portion luff are spaced apart from each other in the second direction to define a thickness of the wing sail; a first batten in contact with the first sail portion, the first batten extending from a first batten luff end to a first batten leech end, wherein the first batten luff end is proximal to the first sail portion luff and the first batten leech end is proximal to the first sail portion leech; and a first twist element extending from a first twist connection to a first lateral connection, wherein the first twist connection is proximal to the first batten and wherein the first lateral connection is laterally displaced from the first batten and arranged on a first rigid linkage such that tensioning the first twist element causes rotation of the first batten relative to the mast.

This arrangement is advantageous as, unlike known arrangements, it enables inducement of twist rather than simply control of twist. Twist refers to rotation of the sail portion/wing sail relative to the mast such that the angle of attack is changed as discussed above. In particular, the inducement of twist of the first sail portion occurs in the area of the first sail portion proximal to the first batten. The control lines of the inventor's earlier patent, EP3052379B1, cannot induce twist but simply adjust the separation of the leech ends of the battens coupled together to accommodate twist.

The wing sail may further comprise a second batten in contact with the second sail portion, the second batten extending from a second batten luff end to a second batten leech end, wherein the second batten luff end is proximal to the second sail portion luff and the second batten leech end is proximal to the second sail portion leech; and a second twist element extending from a second twist connection to a second lateral connection, wherein the second twist connection is proximal to the second batten and wherein the second lateral connection is laterally displaced from the second batten and arranged on a second rigid linkage such that tensioning the second twist element causes rotation of the second batten relative to the mast.

The luff of the sail portions may be mounted to the mast. In particular, the sail portions may be mounted to the mast via their batten luff ends. In particular, the batten luff ends may be pivotally mounted to the mast such that the battens can rotate relative to the mast. The batten luff ends may be pivotally mounted to the trailing edge of the mast.

The twist connections are described as being proximal to the respective batten. For example, the twist connection proximal to the first batten is at or near the first batten and the twist connection proximal to the second batten is at or near the second batten. The twist connection proximal to the first batten may be closer to the first batten than the second batten. The twist connection proximal to the second batten may be closer to the second batten than the first batten.

The first twist element may be directly or indirectly coupled or connected to the first batten via the first twist connection. Similarly, the second twist element may be directly or indirectly coupled or connected to the second batten via the second twist connection.

For example, the twist connections may be arranged on the respective batten such that the twist element is directly coupled to the batten. Alternatively, the twist connections may be arranged adjacent to the respective batten such that the twist element is indirectly coupled to the respective batten. For example, the twist connections may be arranged adjacent to the respective batten such as on the respective sail portion, on a pocket receiving the respective batten, on a portion of the mast proximal to the respective sail portion and/or on a fitting coupled to the respective batten or respective sail portion.

In any arrangement, movement of the twist element through the respective twist connection or movement of the twist connection due to tensioning of the twist element causes rotation of the respective batten about the mast.

The twist connection(s) may be fixed connections, i.e. such that at the connections the tension element does not move relative to the respective batten, sail portion and/or pocket. The twist connections may be receiving portions configured to attach to or be attached to the twist element. For example, the twist connections may be protrusions to which the tension element is affixed or tied. The twist connections may be points on the respective batten, sail portion, portion of the mast proximal to the respective batten and/or fitting attached to the respective sail portion/batten to which the twist element is attached, for example, with stitching, tape, adhesive or other mechanical fastening. Alternatively, the twist connections may not be fixed connections. For example, the twist connections may be receiving portions or openings in, for example, the respective batten and/or pocket. The twist connections may be receiving portions or openings in a fitting attached to the respective sail portion and/or batten or on a portion of the mast proximal to the respective batten. The twist element may be received through and pulled through such opening or receiving portion to apply tension to the twist element and move the twist connection towards the respective lateral connection thereby applying a torque to the batten to cause the batten to rotate relative to the mast in a direction towards the lateral connection. The opening or receiving portion may be a loop, eyelet, channel or through-hole.

The lateral connection is laterally displaced from the respective batten. The first lateral connection is laterally displaced from the first batten and the second lateral connection is laterally displaced from the second batten. The first lateral connection is therefore spaced apart from the first batten along a direction lateral (transverse) to the longitudinal direction of the first batten. The second lateral connection is therefore spaced apart from the second batten along a direction lateral (transverse) to the longitudinal direction of the second batten. As discussed, each batten is elongate and its longitudinal direction is along its length i.e. from the luff end to the leech end of the batten.

The first lateral connection may be nearer to the mast than the first twist connection. The first lateral connection may be proximal to the mast and the twist connection may be proximal to the leech end of the wing sail. The second lateral connection and second twist connection may be similarly configured.

When tensioned, the first twist element may form a straight line between the first twist connection and the first lateral connection. Similarly, the second twist element may form a straight line between the second twist connection and the second lateral connection.

The first lateral connection may be arranged on a first rigid linkage and the second lateral connection may be arranged on a second rigid linkage. The first and/or second rigid linkages are rigid such that they do not deform or bend under normal forces in use in this application to any degree that affects their function.

The first rigid linkage and/or the second rigid linkage may have at least a portion extending in a direction lateral (i.e. transverse) to the longitudinal direction of the respective batten. The first and/or second arm may be or form part of a frame, which may be a lateral frame.

Each twist connection and each lateral connection may be arranged outside the wing sail (i.e. outside the cavity formed by the sail portions). Each twist connection may be arranged on outer surface of the respective sail portions. Each twist element may be arranged outside the wing sail (i.e. outside the cavity formed by the sail portions). Each lateral connection may be arranged outside the wing sail (i.e. outside the cavity formed by the first and second sail portions).

In particular, the first and/or the second lateral connection may be arranged on a distal part of the respective rigid linkage (i.e. the outermost extremity), which is distal from the respective batten. The first and/or the second linkage may extend outwardly of the wing sail (i.e. in a direction away from the cavity formed by the first and second sail portions).

The first linkage may be coupled to the first batten. The first linkage may be pivotally or rigidly coupled to the first batten. The first linkage may be configured to abut the mast on tensioning the first tension element. In such an arrangement, the first linkage may be coupled to a portion first batten proximal to the first batten luff end. The first rigid linkage may be spaced apart from the mast until tension is applied to the first twist element. The first rigid linkage may be rigidly coupled to a portion of the first batten proximal to the first batten luff end such that the first rigid linkage does not move relative to the portion of the first batten.

The first rigid linkage may comprise a first abutting portion configured to abut the mast on tensioning the tension element, a first protruding portion laterally spaced from the first batten on which the first lateral connection is arranged and a first coupling portion configured to couple to the first batten. The first abutting portion, the first protruding portion and the first coupling portion may be rigidly coupled together such that they do not move relative to each other.

The first abutting portion may extend along a direction transverse to the longitudinal direction of the first batten away from the second batten. The first protruding portion may extend along a direction transverse to the longitudinal direction of the first batten towards the second batten. The first coupling portion may extend along a longitudinal direction of the first batten.

The first abutting portion may be configured to abut a trailing edge of the mast. The first abutting portion may form a part of a first abutting arm that extends across at least a part of the thickness of the wing sail towards the second batten (i.e. within the cavity). The first protruding portion may form a part of a first protruding portion that extends in a direction away from the mast and second batten (i.e. outside the cavity). The first protruding portion, and so the first lateral connection, may be arranged on a distal end of the first protruding arm, the distal end being distal from the mast.

The first abutting arm and the first protruding arm may extend in a direction lateral (transverse) to the longitudinal direction of the first batten. The first abutting arm and the first protruding arm may be parallel.

The first abutting portion and the first protruding portion may be integrally formed.

The first coupling portion may form part of a first coupling arm extending in a direction parallel to the longitudinal direction of the first batten.

The first coupling portion, the first abutting portion and the first protruding portion may be joined together at a central point. Alternatively, the first coupling portion, the first abutting portion and the first protruding portion may form parts of an integrally formed rigid member. The integrally formed rigid member may be triangular in shape and the first protruding portion, the first coupling portion and the first abutting portion may form corners of the rigid member.

In use of such an arrangement, on tensioning the first twist element, the first rigid linkage rotates about the first batten luff end until the first abutting portion abuts the mast and further tensioning of the first twist element generates a torque between the mast and the first batten causing the first batten to rotate about the mast.

The second linkage may be coupled to the second batten. The second linkage may be pivotally or rigidly coupled to the second batten. The second linkage may be configured to abut the mast on tensioning the second tension element. In such an arrangement, the second linkage may be coupled to a portion second batten proximal to the second batten luff end. The second rigid linkage may be spaced apart from the mast until tension is applied to the second twist element. The second rigid linkage may be rigidly coupled to a portion of the second batten proximal to the second batten luff end such that the rigid linkage does not move relative to the portion of the second batten.

The second rigid linkage may comprise a second abutting portion configured to abut the mast on tensioning the tension element, a second protruding portion laterally spaced from the second batten on which the second lateral connection is arranged and a second coupling portion configured to couple to the second batten. The second abutting portion, the second protruding portion and the second coupling portion may be rigidly coupled together such that they do not move relative to each other.

The second abutting portion may be configured to abut a trailing edge of the mast.

The second abutting portion may form a part of a second abutting arm that extends across at least a part of the thickness of the wing sail towards the second batten (i.e. within the cavity). The second protruding portion may form a part of a second protruding portion that extends in a direction away from the mast and second batten (i.e. outside the cavity). The second protruding portion, and so the second lateral connection, may be arranged on a distal end of the second protruding arm, the distal end being distal from the mast.

The second abutting arm and the second protruding arm may extend in a direction lateral (transverse) to the longitudinal direction of the second batten. The second abutting arm and the second protruding arm may be parallel.

The second abutting portion may extend along a direction transverse to the longitudinal direction of the second batten away from the second batten. The second protruding portion may extend along a direction transverse to the longitudinal direction of the second batten towards the first batten. The second coupling portion may extend along a longitudinal direction of the second batten. The second coupling portion may be arranged between the second abutting portion and the second protruding portion.

The second abutting portion and the second protruding portion may be integrally formed.

The second coupling portion may form part of a second coupling arm extending in a direction parallel to the longitudinal direction of the second batten. The second coupling portion, the second abutting portion and the second protruding portion may be joined together at a central point. Alternatively, the second coupling portion, the second abutting portion and the second protruding portion may form parts of an integrally formed rigid member. The integrally formed rigid member may be triangular in shape and the second protruding portion, the second coupling portion and the second abutting portion may form corners of the rigid member.

In use of such an arrangement, on tensioning the second twist element, the second rigid linkage rotates about the second batten luff end until the second abutting portion abuts the mast and further tensioning of the second twist element generates a torque between the mast and the second batten causing the second batten to rotate about the mast.

In an alternative arrangement, the first and/or second rigid linkages may not abut the mast on tensioning the tension element. Instead, the first and/or second rigid linkages may be coupled to the mast.

The first and/or second rigid linkages may be mounted on the mast or rigidly coupled to the mast. The first and/or second linkages may be directly coupled to the mast. The first and/or second linkages may be integrally formed with the mast.

The first rigid linkage may be a first arm extending from the mast and/or the second linkage may be a second arm extending from the mast. The first arm may extend in the second direction (i.e. the direction transverse to the direction defined between the leading and trailing edge of the mast). The first arm may extend in a direction transverse to the longitudinal direction of the first batten. The second arm may also extend in the second direction (i.e. in the direction transverse to the direction defined between the leading and trailing edge of the mast). The second arm may extend in a direction transverse to the longitudinal direction of the second batten. In other words, the first arm may extend from the mast in a direction away from the cavity formed between the first and second sail portions. The second arm may extend from the mast in a direction away from the cavity formed between the first and second sail portions. Accordingly, the first and second arms may extend outwardly from the mast.

The first lateral connection may be arranged on a portion of the first arm distal from the mast and the second lateral connection may be arranged on a portion of the second arm distal from the mast.

In use, on tensioning the first tension element, a torque is induced between the first batten and the mast thereby causing the first batten to rotate about the mast. Similarly, on tensioning the second tension element, a torque is induced between the second batten and the mast thereby causing the second batten to rotate about the mast.

The lateral connections may be fixed connections i.e. such that at the connections the twist element does not move relative to the respective linkage. The first and/or second lateral connection may be a receiving portion configured to attach to or be attached to the respective twist element. For example, the first and/or second lateral connection may be a protrusion to which the respective twist element is affixed or tied. The first and/or second lateral connection may be a point on the respective linkage. The tension element may be secured to such points forming the lateral connections with, for example, stitching, tape, adhesive or other mechanical fastening.

Alternatively, each lateral connection may not be a fixed connection. In other words, each twist element may be moveable through the respective lateral connection. For example, the first and/or second lateral connection may be a receiving portion arranged on or opening in, for example, the respective linkage or a fitting rigidly coupled to the respective linkage. The opening or receiving portion may be a loop, eyelet, channel or through-hole. The first twist element may be moveable through the first lateral connection such that on tensioning the first twist element, the length of the twist element between the first lateral connection and the first twist connection is reduced. Similarly, the second twist element may be moveable through the second lateral connection such that on tensioning the second twist element, the length of the second twist element between the second lateral connection and the second twist connection is reduced.

Optionally, at least one of the first twist and first lateral connections is a fixed connection. Similarly, optionally, at least one of the second twist and second lateral connections is a fixed connection.

Optionally, one of the first twist and lateral connections is a fixed connection and one of the first twist and lateral connections is not fixed such that the first twist element may be movable through the non-fixed first connection such that on tensioning the first twist element, the length of the first twist element between the first twist and lateral connections is reduced. Similarly, in an optional arrangement, one of the second twist and lateral connections is a fixed connection and one of the second twist and lateral connections is not fixed such that the second twist element may be movable through the non-fixed second connection such that on tensioning the second twist element, the length of the second twist element between the second twist and lateral connections is reduced.

In an arrangement, the first twist connection may be a fixed connection and the first lateral connection may not be a fixed connection such that on tensioning the twist element is pulled through the first lateral connection to reduce the length of the first tension element between the first lateral connection and the first twist connection and move the first twist connection towards the lateral connection thereby rotating the first batten about the mast in a direction towards the first lateral connection. Similarly, the second twist connection may be a fixed connection and the second lateral connection may not be a fixed connection such that the twist element is received through and pulled through the second lateral connection to reduce the length of the second tension element between the second lateral connection and the second twist connection and move the second twist connection towards the lateral connection thereby rotating the second batten about the mast in a direction towards the second lateral connection. Such an arrangement may be employed where the first lateral connection is arranged on the first linkage coupled to the mast and/or the second lateral connection is arranged on the second linkage coupled to the mast.

In an alternative arrangement, the first twist connection and the first lateral connection may both be fixed connection whereby the twist element is tensioned by applying tension to the middle of the tension element to move the first twist connection towards the lateral connection thereby rotating the first batten about the mast in a direction towards the lateral connection. Similarly, the second twist connection and the second lateral connection may both be fixed connection whereby the twist element is tensioned by applying tension to the middle of the tension element to move the second twist connection towards the lateral connection thereby rotating the second batten about the mast in a direction towards the lateral connection. Such an arrangement may be employed where the first lateral connection is arranged on the first linkage coupled to the mast and/or the second lateral connection is arranged on the second linkage coupled to the mast.

In an arrangement where the first lateral connection is arranged on a first linkage configured to abut the mast, the first lateral connection may be a fixed connection and the first twist connection may not be a fixed connection such that on tensioning the first twist element, the first twist element is pulled through the first twist connection to reduce the length of the tension element between the first lateral connection and the first twist connection and rotate the first linkage such that the first linkage abuts the mast and on further tensioning of the first twist element (and so further reduction of the length of the twist element between the first lateral connection and the first twist connection), the first batten is rotated about the mast in a direction towards the first lateral connection. Similarly, in an arrangement where the second lateral connection is arranged on a second linkage configured to abut the mast, the second lateral connection may be a fixed connection and the second twist connection may not be a fixed connection such that on tensioning the second twist element, the second twist element is pulled through the second twist connection to reduce the length of the tension element between the second lateral connection and the second twist connection and rotate the second linkage such that the second linkage abuts the mast and on further tensioning of the second twist element (and so further reduction of the length of the twist element between the second lateral connection and the second twist connection), the second batten is rotated about the mast in a direction towards the second lateral connection.

The first and/or second linkages may extend laterally in the same plane as the cross section of the mast.

Each of the first and/or second linkages may be frames. Each frame may be located at the luff of each of the first and second battens and may extend laterally from the luff of the respective sail portion (in a plane substantially in the same plane as the cross section of the mast) such that it extends outwards substantially perpendicular to the luff and inwards substantially perpendicular to the luff such that if a rearward load is applied to the outermost end of the frame (the protruding portion), the frame makes contact with the rear face (trailing edge) of the mast so as to resist the applied load. Each twist element may be attached from the respective batten near the batten leech end (at the twist connection) to near the outermost extremity of the linkage, which may be a frame (the lateral connection at the protruding portion) such that a torque can be applied to the batten to cause it to rotate about the luff towards the outermost extremity of the linkage.

The first and second twist elements may form a first pair of twist elements and the first and second battens may form a first pair of battens and the wing sail may comprise a further pair of twist elements and a further pair of battens similarly configured. The first pair of twist elements and first pair of battens may be arranged in the upper half or a top part or head of the wing sail and the second pair of twist elements and second pair of battens may be arranged in the lower half of the wing sail and the first pair of tension elements may be separately controllable from the second pair of twist elements such that the twist in the upper half may be separately controlled from the twist in the lower half of the wing sail. The mast may have a leading edge and a trailing edge. The first sail portion luff and the second flexible sail portion luff may be spaced apart along the trailing edge. The first sail portion and the second sail portion may be mounted at the trailing edge of the mast.

The rigging may comprise a boom pivotally mounted to the mast at one end and optionally coupled to the leech of the sail portions at the other end such that the boom can rotate relative to the mast. Accordingly, the first sail portion may be coupled to a first side of the boom and the second sail portion may be coupled to a second side of the boom. The boom has a length extending in the first direction of the wing sail (i.e. from luff to leech). The boom may be mounted to the upper half or the lower half of the mast.

In an arrangement, the boom may be controllably articulated between its ends. One or more boom arms, which may be quadrant arms or lever arms, may extend laterally from the boom where lateral in this instance means transverse to the length of the boom. In an arrangement, the boom may be controllably articulated between its ends. A first boom arm may extend from the first side of the boom and a second boom arm may extend from the second side of the boom.

The first twist element may lead from the lateral connection to a first boom connection arranged on the first boom arm. The first boom connection may be configured such that an angular change between the mast and the boom causes the first boom arm to apply tension to the first twist element so as to induce tension between the first lateral connection and the first twist connection. The first boom connection may be a fixed connection. Similarly, the second twist element may lead from the second twist connection to a second boom connection arranged on the second boom arm. The second boom connection may be a fixed connection such that an angular change between the mast and the boom causes the second arm to apply tension to the second twist element so as to induce tension between the second lateral connection and the second twist connection. In such an arrangement, the tension applied to the respective twist element increases or decreases depending on the direction and magnitude of the angular displacement between the boom and the mast.

In an arrangement, a clockwise angular displacement between mast and boom when viewed from the top of the wing sail results in the twist element on the port sail portion to be tensioned and the twist element on the starboard sail portion such to be loosened, thus causing the sail portions at the top of the sail to twist in an opposite direction to the angular displacement between the mast and the boom at the bottom of the sail. An anticlockwise angular displacement would have a correspondingly opposite effect.

The invention also provides a method of using the rigging comprising a wing sail having the first tension element, the method comprising: applying tension to the first twist element to rotate the first batten relative to the mast.

The first batten rotates relative to the mast thereby inducing/changing the twist of the first sail portion in the area of the first batten.

The invention also provides a wind propelled craft comprising the wing sail and/or rigging of any of the aspects of the invention described above.

A wing sail or rigging according to the invention may include any combination of the features described in the invention. For example, the tension elements, luff and leech connections may be combined with the first and second stops and/or may be combined with the twist elements, rigid linkages, twist and lateral connections. The first and second stops may be combined with the twist elements, rigid linkages, twist and lateral connections.

Generally, any of the above mechanisms described to work on one sailing tack or wind angle of attack direction are applicable on for the other sailing tack or wind angle of attack direction. That is the mechanisms described apply to both port and starboard tack configurations.

The following may apply to all of the embodiments disclosed herein.

"Proximal to" as used herein refers to at or near.

The sail portions may be flexible and so form a "soft construction" or "semi rigid" construction wing sail such that the sail portions can be hoisted, reefed, furled and stowed. The sail portions may be formed of a fabric. The change in the shape of the first sail portion is a change in curvature of the first sail portion i.e. a change in camber of the first sail portion. In particular the change in shape of the first sail portion occurs in the area of the first sail portion proximal to the first batten.

Optionally, the first batten leech end is free to move relative to the second batten leech end. The first batten leech end and the second batten leech are not coupled together. Optionally, the first batten leech end and the second batten leech are coupled together via an element of variable length such that the first batten leech end may move relative to the second batten leech end. Optionally, the first batten leech end and the second batten leech end may freely move laterally and in the first direction (i.e towards or away from the luff of the wing sail). Optionally, the spacing between the first batten leech end and the second batten leech end can freely increase or decrease without restriction. Such an arrangement is advantageous compared to the inventor's previous patents, EP3052379B 1 and US4766831 where the leech ends of the battens are coupled together thereby restricting relative movement of the leech ends of the battens, which in turn restricts twist of the wing sail.

The first sail portion is generally opposite the second portion thereby forming a cavity between first and second sail portions. The reference herein to “inner” or “inside” refers to within the cavity formed between the first and second sail portions and the reference to “outer” or “outside” refers to outward of the cavity between the first and second sail portions. The first sail portion and the second sail portion may be of a similar shape and size such that the first and second sail portions have the same height (i.e. length from head to foot) and the same chord length (length from luff to leech). Optionally, the first and second sail portions have the same shape and size. Optionally, the first and second sail portions are substantially identical. The first and second sail portions are typically arranged to give the sail a thickness which is substantially greater than either of the first and second sail portions individually.

The first and second battens may be positioned at the same height or position along the length of the mast such that the first and second battens form a pair of battens (batten pair).

The first and second battens may be elongated and have longitudinal flexure which stiffen the respective sail portion from luff to leech.

The first batten may be one of a plurality of first battens connected to the first sail portion and the second batten may be one of a plurality of second battens connected to the second sail portion, wherein optionally the first plurality of battens have similar vertical spacing and similar lengths to the second plurality of batten such that the batten of the first plurality of battens at the same vertical position as the batten of the second plurality of battens are a pair of battens.

Each batten may be received within a corresponding pocket on the sail portion. The pocket may extend at least partially along the respective sail portion between the luff and the leech of the respective sail portion. The pocket may be secured to the sail portion with, for example, stitching. The pocket may extend along the inner surface of the respective sail portion. The pocket may be formed of a same or similar material to the sail portions, e.g. a fabric.

When the wing sail is rigged to a mast, each batten may be pivotally mounted to the mast such that battens may rotate about the mast.

Each of the twist and/or tension elements may be a flexible inextensible member such as a line, chord, wire or tape. Inextensible refers to an element that does not extend under normal forces experienced during use to any degree that affects its function. Tension may be applied to the each twist and/or tension element via pulleys. The pulleys may be configured such that the tension applied to the twist and/or tension elements may be controlled from the bottom of the sail. For example, in arrangements where the first and second battens and luff and leech connections and/or twist connections are arranged in the top half of the sail, the tension element and/or twist element extending from the leech connection point to the luff connection point may then be led through a pulley and towards the bottom of the sail thereby enabling control of the tension applied to the tension and/or twist element from the bottom of the wing sail. The tension element and/or twist element may be led along the luff of the respective sail portion. For example, the first tension and/or twist element may be led from through the pulley along the luff of the first sail portion. The second tension and/or twist element may be similarly configured. Tension may be applied to the tension and/or twist elements manually or by, for example, a hydraulic, pneumatic or electric actuator or ram (or any other such means of applying a tensional force). Each of the tension and/or twist elements may be a hydraulic, pneumatic or electric actuator or ram.

The twist element may be a twist control line. Each of the twist and/or tension elements (and the first and second battens) may be arranged in an upper half or a top part or head of the respective sail portion. For example, the tension and/or twist elements (and the first and second battens) may be positioned in the upper 50%, 40%, 30%, 20% or 10% of the respective sail portion. The tension and/or twist elements (and the first and second battens) may be arranged proximal to the uppermost edge (head) of the respective sail portions.

The tension and/or twist elements may be positioned in the upper half of the respective sail portion such that the camber and angle of attack in the upper half of the tension elements is controlled by the tension and/or twist elements and the camber and angle of attack in the lower half of the respective sail portion is otherwise controlled, for example by the outhaul and wind loads. In such an arrangement, opposite camber may be induced in the upper half of the wing sail compared to the camber induced in the lower half of the wing sail. The angle of attack in the upper half of the wing sail may be different from the angle of attack in the lower half of the sail due to the inducement of twist.

The tension and/or twist elements may form a first pair of tension and/or twist elements and the first and second battens may form a first pair of battens. The wing sail may comprise a further pair of tension and/or twist elements and a further pair of battens similarly configured. The first pair of tension and/or twist elements, first pair of battens and respective connections may be arranged in the upper half or a top part or head of the wing sail and the second pair of tension and/or twist elements, second pair of battens and respective connections may be arranged in the lower half or bottom part of the wing sail. The first pair of tension and/or twist elements may be separately controllable from the second pair of tension and/or twist elements such that the camber and/or twist in the upper half may be separately controlled from the camber and/or twist in the lower half of the wing sail. In such an arrangement, opposite camber and/or twist may be induced in the upper half/part of the wing sail compared to the camber and/or twist induced in the lower half/part of the wing sail.

The inducement of rotation of one batten in the pair of battens may induce a similar rotation in the other batten of the pair of battens as the rotational force between the mast and the one batten will be in a direction towards the mast such that the other batten will be acted on by the first batten to twist in the same direction. Accordingly, rotation is induced for the pair of battens on applying tension to a single twist element thereby inducing twist for the area of the wing sail proximal to the pair of battens.

Brief Description of the Figures

The figures set out non-limiting specific examples of possible implementations of the aspects of the present invention.

Figure 1 is a schematic side view of a wind propelled craft having a wing sail according to the present invention, the wing sail comprising first and second battens and first and second sail portions.

Figures 2(a) and (b) are schematic plan views of the first batten and first tension element of a wing sail according to the invention where the first tension element is under less tension in Figure 2(a) than in Figure 2(b).

Figure 3(a) is a schematic plan view showing a section through a mast and wing sail having first and second tension elements in accordance with the invention on a port tack.

Figure 3(b) is a schematic plan view showing a section through a mast and wing sail having first and second tension elements in accordance with the invention on a starboard tack.

Figure 4 is a schematic plan view showing a section through a mast and wing sail having a first tension element in accordance with the invention.

Figure 5 is a schematic plan view showing first and second sections through a mast and wing sail having a first tension element in accordance with the invention, with the representation on the left showing a section of the upper half of the wing sail having the first tension element and the representation on the right shown a section of the lower half of the wing sail not having the first tension element.

Figure 6 is a schematic side view of a wing sail in accordance with the invention.

Figure 7 is a schematic plan view showing a section through a mast and wing sail having a first stop in accordance with the invention. Figure 8 is a schematic plan view showing a section through a mast and wing sail having a second stop in accordance with the invention.

Figure 9(a) is a schematic plan view showing a section through a mast and wing sail having a first stop and a second stop in accordance with the invention. Figure 9(b) is a magnified view of part of the section of the mast and wing sail shown in Figure 9(a).

Figure 10 is a schematic plan view showing first and second sections through a mast and wing sail having a first tension element in accordance with the invention, with the representation on the left showing a section of the upper half of the wing sail having the first tension element and a twist element and the representation on the right shown a section of the lower half of the wing sail not having the tension element or the twist element.

Detailed Description

Figure 1 is a schematic side view of a wind propelled craft, which is a sailing vessel 10 comprising a deck 20 and a rigging 30. The rigging comprises the wing sail 100 in accordance with the invention and a mast 50.

In this exemplary implementation, the mast 50 is connected to the deck 20 by a connector (not shown). The mast 50 is supported by, for example, stays or shrouds (not shown) supported partway up the mast 50 by a spreader (not shown). The mast 50 has a leading edge 51 and a trailing edge 52 defining a first direction therebetween and a second direction transverse to the first direction.

The wing sail 100 has a luff 101 (front edge) and a leech 102 (trailing edge). The wing sail 100 has a height extending between its head 103 and foot 104. The wing sail comprises a first sail portion 110 and a second sail portion 120. In this exemplary implementation, the first and second sail portions are flexible. In this side-on view only the first sail portion 110 is visible. Each sail portion 110, 120 has a luff (front edge) and a leech (trailing edge). The first sail portion has a first sail portion luff 111 and a first sail portion leech 112 and the second sail portion has a second sail portion luff 121 and a second sail portion leech 122. The first sail portion 110 has a first sail portion head 113 and a first sail portion foot 114 and the second sail portion has a second sail portion head and a second sail portion foot.

The first sail portion 110 is generally opposite the second portion 120 thereby forming cavity 105 between first and second sail portions 110, 120. The reference herein to inner or inside refers to within the cavity 105 formed between the first and second sail portions 110, 120 and the reference to outer or outside refers to outward of the cavity 105 formed between the first and second sail portions 110, 120. The first sail portion 110 and the second sail portion 120 are of a similar shape and size such that the first and second sail portions 110, 120 have a similar height and similar chord length (length from luff to leech). The first and second sail portions 110, 120 are arranged to give the sail a thickness which is substantially greater than either of the first and second sail portions 110, 120 individually.

The wing sail 100 has a first batten 130 in contact with the first sail portion 110, the first batten 130 extending from a first batten luff end 131 to a first batten leech end 132. The first batten luff end 131 is proximal to the first sail portion luff 111 and the first batten leech end 132 is proximal to the first sail portion leech 112.

The wing sail 100 has a second batten 140 in contact with the second sail portion 120, the second batten 140 extending from a second batten luff end 141 to a second batten leech end 142. The second batten luff end 141 is proximal to the second sail portion luff 121 and the second batten leech end 142 is proximal to the second sail portion leech 122. In particular, each batten 130, 140 is in contact with an inner surface of the respective sail portion such that each batten 130, 140 is within the cavity 105 formed between the sail portions 110, 120.

The first and second battens 130, 140 are elongated and have longitudinal flexure. The first and second battens 130, 140 are arranged so that they stiffen the respective sail portions 110, 120 from luff to leech.

The first and second battens 130, 140 are arranged at a similar vertical height (i.e. the same vertical position) and have a similar length thereby forming a pair of battens.

The mast 50 has a leading edge 51 defining a convex surface and a trailing edge 52 defining a flat surface.

Each batten 130, 140 is pivotally connected to the trailing edge 52 of the mast 50 such that each batten 130, 140 can rotate relative to the mast 50. The first baten 130 may be received within a first batten pocket 133 extending along the interior of the sail portion 110 along a part of the first sail portion between the first sail portion luff 111 and the first sail portion leech 112 (i.e. in the first direction). Similarly, the second batten 140 may be received within a first batten pocket 143 extending along the interior of the sail portion 120 along a part of the first sail portion between the first sail portion luff 121 and the first sail portion leech 122 (i.e. in the first direction).

The first batten pocket 133 and the second batten pocket 143 may be formed of the same material as the sail portion, e.g. a fabric and may be attached to the respective sail portion by, for example, stitching.

In the specific embodiment shown in Figure 1, the wing sail 100 has multiple pairs of battens and corresponding batten pockets that are spaced apart from each other along the height of the sail. Each batten on the first sail portion 110 at a similar vertical height to the batten on the second sail portion 120 form a pair of battens.

In use, stagnation of the air at the luff 101 or mast 50 on the windward side of the wing sail, along with the shape of the aerofoil section, creates an asymmetry in the air path from the windward to the leeward sides of the sail or aerofoil. Consequently, given that other aerodynamic conditions are satisfied regarding the joining of the flow streams downwind of the sail or aerofoil, this asymmetry creates increases the speed of the air on the leeward side relative to the windward side and hence a pressure difference between the leeward and windward sides. This pressure differential results induces aerodynamic lift to the wing sail 100, which in turn propels the vessel 10.

As best shown in Figure 2, in accordance with a first aspect of the present invention, the wing sail 100 comprises a first tension element 150 extending from a first luff connection 151 to a first leech connection 152. The first luff connection 151 is proximal to the first batten luff end 131 and the first leech connection 152 is proximal to the first batten leech end 132. The first tension element 150 extends between the first luff connection 151 and the first leech connection 152 such that on tensioning of the first tension element 150, the first tension element 150 draws the first leech connection 152 towards the first luff connection 151 thereby bending the first batten leech end 132 towards the first batten luff end 131 to change the shape of the first sail portion. In other words, on tensioning the first tension element 150, the first tension element 150 exerts a bending force on the first batten 130, the first batten 130 being configured to bend under the bending force to thereby change the shape of the first sail portion 110. The shape of the first sail portion 110 is changed as the curvature of the first sail portion 110 in the area of the first batten 130 is increased. Figure 2(b) demonstrates the increased curvature achieved by applying more tension to the first tension element 150 compared to Figure 2(a). The first tension element 150 is inextensible. In this exemplary implementation, the first tension element 150 may be a line, tape or chord. The first luff connection 151 may be arranged on the first batten luff end 131 , on an area of the pocket 133 receiving the batten proximal to the first batten luff end 151 or on an area of the first sail portion 110 proximal to the first batten luff end 131. The first luff connection 151 may be in/on a fitting (not shown) connected to the first batten luff end 131 or connected to the area of the first sail portion 110 proximal to the first batten luff end 131.

The first luff connection 151 may not be a fixed connection such that the first tension element 150 can be moved therethrough. The first luff connection 151 may be an opening or receiving portion such as a loop, eyelet, channel or through-hole.

The first leech connection 152 may be arranged on the first batten leech end 132, on an area of the pocket proximal 133 to the first batten leech end 132 or on an area of the first sail portion 110 proximal to the first batten luff leech end 132. The first leech connection 152 may be in/on a fitting connected to the first batten leech end 132 or to the area of the first sail portion 110 proximal to the first batten leech end 132.

The first leech connection 152 may be a fixed connection i.e. such that at the first leech connection 152, the first tension element 150 does not move relative to the first batten leech end 132, the area of the first sail portion 110 proximal to the first batten leech end 132 and/or area of the pocket 133 proximal to the first batten leech end 132. The first leech connection 152 may be a receiving portion configured to attach to or be attached to the first tension element 150. The first leech connection 152 may be a protrusion to which the first tension element 150 is affixed or tied and/or may be a point on the first batten 130, first sail portion 110 and/or pocket 133 receiving the first batten 130 proximal to the first batten leech end 132 to which the first tension element 150 is attached, for example, with stitching, tape, adhesive or other mechanical fastening. The first leech connection 152 may be a point within a fitting attached to the first sail portion 110 or first batten 130 proximal to the first batten leech end 132.

In use, on tensioning the first tension element 150, the first tension element 150 may be drawn through the first luff connection 151 such that the length of the first tension element between the first luff connection 151 and the first leech connection 152 is reduced thereby drawing the first leech connection 152 towards the first luff connection 151 and bending the first batten leech end 132 towards the first batten luff end 131. In other words, tensioning the first tension element 150 exerts a compressive force on the first batten 130 causing the first batten 130 to bend.

Bending the first batten 130 increase curvature in the first sail portion 110 in the area proximal to the first batten 130 thereby changing the shape (camber) of the first sail portion 110.

Tension may be applied to the first tension element 150 by pulling the first tension element 150 (manually or, for example, with a hydraulic actuator) through the first luff connection 151.

The first batten leech end 132 and the second batten leech end 142 are not coupled together such that the first batten leech end 132 may move freely relative to the second batten leech end 142.

As shown in Figure 2, the first tension element 150 forms a straight line between the first luff connection 151 and the first leech connection 152 when tensioned. Similarly, the second tension element 160 forms a straight line between the second luff connection 161 and the second leech connection 162 when tensioned.

Figures 3(a) is a schematic plan view showing a section through the wing sail 100 and mast 50 in accordance with the first aspect of the invention on a port tack. Figure 3(b) is a schematic plan view showing a section through the wing sail 100 and mast 50 in accordance with the first aspect of the invention on a starboard tack.

As best shown in Figure 3(a), the wing sail 100 also comprises a second tension element 160 extending from a second luff connection 161 to a second leech connection 162. The second luff connection 161 is proximal to the second batten luff end 141 and the second leech connection 162 is proximal to the second batten leech end 142. The second tension element 160 extends between the second luff connection 161 and the second leech connection 162 such that on tensioning of the second tension element 160, the second tension element 160 draws the second leech connection 162 towards the second luff connection 161 thereby bending the second batten leech end 142 towards the second batten luff end 141 to change the shape of the second sail portion 120. In other words, on tensioning the second tension element 160, the second tension element 160 exerts a bending force on the second batten 140, the second batten 140 being configured to bend under the bending force to thereby change the shape of the second sail portion 120. The shape of the second sail portion is changed as the curvature of the second sail portion 120 in the area of the second batten 140 is increased. The first tension element 150 is inextensible. In this exemplary implementation, the second tension element 160 may be a line, tape or chord. The luff connection 161 may be arranged on the second batten luff end 141, on an area of the pocket 143 receiving the second batten 140 proximal to the second batten luff end 141 or on an area of the second sail portion 120 proximal to the second batten luff end 141. The second luff connection 161 may be in/on a fitting connected to the second batten luff end 141 or to the area of the second sail portion 120 proximal to the second batten luff end 141. The second luff connection 161 may not be a fixed connection such that the second tension element 160 can be moved therethrough. The second luff connection 161 may be an opening or receiving portion such as a loop, eyelet, channel or through-hole.

The second leech connection 162 may be arranged on the second batten leech end 142, on an area of the pocket 143 proximal to the second batten leech end 142 or on an area of the second sail portion 120 proximal to the second batten leech end 142. The second leech connection 162 may be in/on a fitting connected to the second batten leech end 142 or to the area of the second sail portion 120 proximal to the second batten leech end 142.

The second leech connection 162 may be a fixed connection i.e. such that at the second leech connection 162, the second tension element 160 does not move relative to the second batten leech end 142, area of the second sail portion 120 proximal to the second batten leech end 142 and/or area of the pocket 143 proximal to the second batten leech end 142. The second leech connection 162 may be a receiving portion configured to attach to or be attached to the second tension element 160. The second leech connection 162 may be a protrusion to which the second tension element 160 is affixed or tied and/or may be a point on the second batten 140, second sail portion 120 and/or pocket 143 receiving the second batten 140 proximal to the second batten leech end 142 to which the second tension element 160 is attached, for example, with stitching, tape, adhesive or other mechanical fastening. The second leech connection 162 may be a point within a fitting attached to the second sail portion 120/second batten 140 proximal to the second batten leech end 142.

In use, on tensioning the second tension element 160, the second tension element 160 may be drawn through the second luff connection 161 such that the length of the second tension element 160 between the second luff connection 161 and the second leech connection 162 is reduced thereby drawing the second leech connection 162 towards the second luff connection and bending the second batten leech end 142 towards the second batten luff end 141. In other words, tensioning the second tension element 160 exerts a compressive force on the second batten 140 causing the second batten 140 to bend.

As shown in Figure 3(a), when the first batten 130 forms the windward batten and the second batten 140 forms the leeward batten, the tension applied to the first tension element 150 is less than the tension applied to the second tension element 160 such that the leeward batten has greater curvature than the windward batten thereby forming an asymmetric aerofoil shape, which is aerodynamically desirable.

As shown in Figure 3(b), when the first batten 130 forms the leeward batten and the second batten 140 forms the windward batten, the tension applied to the first tension element 150 is greater than the tension applied to the second tension element 160 such that the leeward batten has greater curvature than the windward batten thereby forming an asymmetric aerofoil shape, which is aerodynamically desirable.

As shown in Figure 4, the first tension element 150 may extend from the first luff connection 151 to the first leech connection 152 and then through the first leech connection 152 to a separator connection 153 proximal to the second batten 140. In this exemplary implementation, the first luff connection 151, the first leech connection 152 and separator connection 153 may arranged within the wing sail 100 (i.e. within the cavity 105 formed by the first and second sail portions 110, 120).

As described above, the first tension element 150 is inextensible. In this exemplary implementation, the first tension element 150 may be a line, tape or chord.

The first luff connection 151 may be arranged on the first batten luff end 131, on an area of the pocket 133 proximal to the first batten luff end 131 or on an area of the first sail portion 110 proximal to the first batten luff end 131. The first luff connection 151 may be in/on a fitting connected to the first batten luff end 131 or to the area of the first sail portion 110 proximal to the first batten luff end 131. The first luff connection 151 may not be a fixed connection such that the first tension element 150 can be moved therethrough. The first luff connection 151 may be an opening or receiving portion such as a loop, eyelet, channel or through-hole.

The first leech connection 152 may be arranged on the first batten leech end 132, on an area of the pocket 133 proximal to the first batten leech end 132 or on an area of the first sail portion 110 proximal to the first batten leech end 132. The first leech connection 152 may be in/on a fitting connected to the first batten leech end 132 or to the area of the first sail portion 110 proximal to the first batten leech end 132. The leech connection 132 may not be a fixed connection such that the first tension element 150 can be moved therethrough. The leech connection 132 may be an opening or receiving portion such a loop, eyelet, channel or through-hole.

The separator connection 153 may be arranged on the second batten 140, on an area of the pocket 143 receiving the second batten 140, or on an area of the second sail portion 120. The separator connection 153 may be in/on a fitting connected to the second batten 140 or second sail portion 120. The separator connection 153 may be a fixed connection i.e. such that at the separator connection the tension element does not move relative to the second sail portion 120, second batten 140 and/or pocket 143 receiving the second batten 140.

The separator connection 153 may be a fixed connection i.e. such that at the separator connection 152, the first tension element 150 does not move relative to the second batten 140, the pocket 143 receiving the second batten and/or the second sail portion 120. The separator connection 153 may be a receiving portion configured to attach to or be attached to the first tension element 150. The separator connection 153 may be a protrusion to which the first tension element 150 is affixed or tied and/or may be a point on the second batten 140, second sail portion 120 and/or pocket 143 receiving the second batten 140 to which the first tension element 150 is attached, for example, with stitching, tape, adhesive or other mechanical fastening. The separator connection 153 may be a point within a fitting attached to the second sail portion 120/second batten 140 to which the tension element is attached, for example, with stitching, tape, adhesive or other mechanical fastening.

In the exemplary implementation shown in this figure, the separator connection 153 is positioned between the luff and the leech ends of the second batten.

The tension element 171 may be lead through a pulley 200 between the separator connection 153 and the first leech connection 152. As discussed above, the first luff connection 151 may not be a fixed connection such that the first tension element 150 can be moved therethrough. The first luff connection 151 may be an opening or receiving portion such as a loop, eyelet, channel or through-hole.

The first leech connection 152 may also not be a fixed connection such that the first tension element 150 can be moved therethrough. The first leech connection 152 may be an opening or receiving portion such as a loop, eyelet, channel or through-hole.

In use, the first tension element 150 may be drawn through the first leech connection 152 and towards through the first luff connection 151 such that on pulling the first tension element 150 to apply tension thereto, the first leech connection 152 is drawn towards the first luff connection 151 and towards the separator connection 153 thereby bending the first batten leech end 132 towards the first batten luff end 131 and drawing the first batten 130 towards the second batten 140. In other words, tensioning the first tension element 150 exerts a compressive force on the first batten 130 and applies a torque between the first and second battens 130, 140. Accordingly, both the camber and thickness of the wing sail in the area of the first and second battens 130, 140 is changed.

The effect of tensioning first tension element 150 on camber is further demonstrated by Figure 5. As discussed above, in Figure 5, the representation on the left shows a section of the upper half of the wing sail having first and second battens 130, 140 forming a first pair of battens connected to the first tension element 150 and the representation on the right shown a section of the lower half of the wing sail having third and fourth battens 180, 190 forming a second pair of battens not have a tension element coupled thereto. The first pair of battens being vertically spaced apart from the second pair of battens as shown in Figure 1. The first tension element 150, luff, leech and separator connections 151, 152, 153 described in respect of Figure 4 equally applies to the first section shown in the representation on the left of Figure 5. Accordingly, as demonstrated by Figure 5, by using the first tension element 150, the camber of the upper part of the sail having the first and second battens 130, 140 may be opposite from the camber of the lower part of the sail having the third and fourth battens 180, 190 which may otherwise be controlled, for example, by the out haul. Accordingly, the upper and lower parts of the wing sail 100 may be controlled to have opposite camber.

Figure 6 is a side view of the wing sail 100 in accordance with the invention where tension is applied to the respective tension element via a pulley 240 arranged at the luff end of the respective batten. The tension element may then be lead down the luff of the respective sail portion such that the tension element may be controlled from the bottom of the sail. A pulley may be employed for both sail portions. However, as only one side of the sail is visible in Figure 6, this arrangement will be described for the first sail portion 110 having the first tension element 150 and first batten 30. The pulley 240 may be configured to receive the first tension element 150, from the first luff connection 151 such that the first tension element 150 may then be lead down the luff 111 of the first sail portion 110 such that the first tension element 150 may be controlled from the bottom of the wing sail 100. In other words, the first tension element 150, which may be a tension line, may be lead down the mast 50 to allow adjustment at the deck 20. Such a pulley 240 may be provided for each batten 130, 140 (i.e. this configuration may be repeated for the second batten 140). In this arrangement, the first and second battens 130, 140 are arranged in the upper part (head) of the wing sail. Tension may be applied to the tension elements 150, 160 via the pulley(s) 240, manually or using, for example, a hydraulic or numeric actuator or ram.

Figure 7 is a schematic plan view showing a section through the wing sail 100 and mast 50 in accordance with the invention where the wing sail employs first and/or second stops 210, 220 to induce and control camber/curvature. The first stop 210 is a rigid stop extending along and coupled at the first batten luff end 131 and extending at least partially across the thickness of the wing sail 100. The first stop 210 is typically formed of, for example, a rigid plastic or metal.

The first stop 210 has a first abutting edge 211 extending across a section of the thickness of the wing sail 100 (i.e. from the first batten luff end 131 towards the second batten luff end 141 ) and a first coupling edge 212 extending along and coupled to a portion of the length of the first batten luff end 131. The coupling edge 212 may be rigidly coupled to the portion of the length of the first batten luff end 131 such that the coupling edge 212 does not move relative to the portion of the length of the first batten luff end 131. In the exemplary implementation shown in this figure, the first coupling edge 212 is at approximately 90° to the first abutting edge 211. In this exemplary implementation, the first abutting 211 does not initially abut the trailing edge 52 of the mast 50 but abuts the trailing edge 52 of the mast 50 on rotation of the mast 50 from an initial position through a first threshold angle in a first rotational direction. The threshold angle may be approximately 0°-10°. According to this figure, the first rotational direction is clockwise.

On further rotation of the mast 50 in the first direction beyond the threshold angle, a bending force is exerted on the first batten 130 due to rotation of the mast 50 and abutment of the trailing edge 52 of the mast 50 against the first stop 210 rigidly atached to the first batten luff end 131. This bending force causes the first batten 130 to bend (i.e. the curvature of the baten to increase) to thereby change the shape of the first sail portion 110 in the area of the first batten 130.

The first abutting edge 211 and the first coupling edge 212 may be integrally formed. The first coupling edge 212 may have one or more channels formed therein for receipt of the portion of the length of the first batten luff end 131 therethrough.

The first stop 210 may be rigidly coupled to the first baten luff end 131 using, for example, screws.

The first stop 210 is configured such that a separation between the first stop 210 and the trailing edge of the mast 52 increases on rotation of the mast 50 in a second rotational direction, which is opposite from the first rotational direction. In the figure, the second rotational direction is anti -clockwise. This functionality is enabled as the first stop 210 is rigidly coupled to the first batten 130 but not to the mast 50. In other words, the first stop 210 is only coupled to the mast 50 via the first baten 130.

Figure 8 is a schematic diagram showing a second stop 220 coupled to the second baten luff end 141. The second stop 220 is configured similarly to the first stop 210. In other words, the second stop 220 is a rigid stop extending along and coupled at the second baten luff end 141 and extending at least partially across the thickness of the wing sail 100. The second stop 220 is typically formed of, for example, a rigid plastic or metal.

The second stop 220 has a second abuting edge 221 extending across a section of the thickness of the wing sail (i.e. from the second batten luff end 141 towards the first baten luff end 131) and a second coupling edge 222 extending along and coupled to a portion of the length of the second batten luff end 141. The second coupling edge 222 may be rigidly coupled to the portion of the length of the second batten luff end 141 such that the second coupling edge 222 does not move relative to the portion of the length of the second batten luff end 141. In this exemplary implementation, the second coupling edge 222 is at approximately 90° to the second abutting edge 221. In this exemplary implementation, the second abuting edge 221 does not initially abut the trailing edge 52 of the mast 50 but would abut the trailing edge 52 of the mast 50 on rotation of the mast 50 from an initial position through a second threshold angle in a second rotational direction. The threshold angle may be approximately 0°-10°. According to this figure, the second rotational direction would be anti-clockwise.

On further rotation of the mast 50 in the second rotational direction beyond the threshold angle, a bending force is exerted on the second batten 140 due to rotation of the mast 50 and abutment of the trailing edge 52 of the mast 50 against the second stop 220 rigidly attached to the second batten luff end 141. This bending force causes the second baten 140 to bend (i.e. the curvature of the second baten 140 to increase) to thereby change the shape of the second sail portion 120 in the area of the second batten 140.

The second abutting edge 221 and the second coupling edge 222 may be integrally formed. The second coupling edge 222 may have one or more channels formed therein for receipt of the portion of the length of the second batten luff end 141 therethrough.

The second stop 220 may be rigidly coupled to the second baten luff end 141, for example, using screws.

The second stop 220 is configured such that a separation between the second stop 220 and the trailing edge 52 of the mast 50 increases on rotation of the mast 50 in a first rotational direction, which is opposite from the second rotational direction. In the figure, the first rotational direction is clockwise and the second rotational direction is anti-clockwise. This functionality is enabled as the second stop 220 is rigidly coupled to the second batten 140 but not to the mast 52. In other words, the second stop 220 is only coupled to the mast 50 via the second batten 140.

In an arrangement where the first baten 130 is the leeward baten, as shown in Figure 7, the mast 50 may be rotated in a first rotational direction such that camber (curvature) in the first batten 130 may be increased. In an arrangement where the second batten 140 is the windward batten, as shown in Figure 8, the mast 50 may be rotated in a first rotational direction such that the separation between the second stop 220 and the trailing edge 52 of the mast 50 is increased and camber (curvature) in the second baten 140 may be decreased.

This is advantageous for forming an asymmetric aerofoil which is aerodynamically desirable.

Figure 9 is a schematic plan view showing a section through the wing sail 100 and mast 50 in accordance with the invention, the wing sail 100 employing both first and second stops 210, 220. The first and second stops 210, 220 are configured as described above. In the specific implementation shown in Figure 9, the first stop 210 and the second stop 220 are coupled together by a linking element 230 that restricts movement of the first stop 210 relative to the second stop 220 beyond an upper limit, such that (i) rotation of the mast 50 in the first rotational direction causes the second stop 220 to move relative to the first stop 210 such that a separation between the second stop 220 and the trailing edge 52 of the mast 50 increases until the upper limit is reached and further rotation of the mast 50 exerts a bending force on the first and second battens 130, 140 to thereby change the shape of the first and second sail portions 110, 120; and (ii) rotation of the mast in the second rotational direction causes the first stop 110 to move relative to the second stop 120 such that a separation between the first stop 210 and the trailing edge 52 of the mast 50 increases until the upper limit is reached and further rotation of the mast 50 exerts a bending force on the first and second battens 130, 140 to thereby change the shape of the first and second sail portions 110, 120.

The linking element 230 therefore does not initially restrict movement of the second stop 220 relative to the first stop 210 such that the leeward batten can camber/curve less than the windward batten. However, at increased mast 50 rotation and so increased displacement between the first and second stops 210, 220, the upper limit is reached that restricts further displacement between the first and second stops 210, 220 thus increasing camber/curvature in both the leeward and windward battens with further mast rotation 50.

The movement restricted by the linking element 230 may be rotation or angular displacement of the first and second stops 210, 220 relative to each other. The linking element 230 may comprise complementary engagement means that are slidably coupled. The linking element 230 may comprise a receiving portion such as a slot or groove or channel 230a in one of the first and second stops 210, 220 and a protrusion (not shown) extending from the other of the first and second stops 210, 220 that is configured to be received within the receiving portion 230a where the length of the receiving portion (slot/groove/channel) may be selected according to the upper limit. The receiving portion, which may be a slot, groove or channel 230a, may be shaped as an arc.

Figure 10 are schematic plan views showing first and second sections through a mast 50 and wing sail 100 according to the invention where a first twist element 170 is employed to induce and control twist in addition to the first tension element 150. The representation on the left shows a section of the upper half of the wing sail 100 having first and second battens 130, 140 forming a first pair of battens, the first tension element 150 and a first twist element 170 coupled thereto and the representation on the right shown a section of the lower half of the wing sail having third and fourth battens 180, 190 forming a second pair of battens but not having a tension element 150 or twist element 170 connected thereto. The first pair ofbattens 130, 140 being vertically spaced apart from the second pair of battens 180, 190, as shown in Figure 1.

The first tension element 150, luff, leech and separator connections 151, 152, 153 described in respect of Figure 4 equally applies to the first section shown in the representation on the left of Figure 10. The embodiment shown in Figure 10 differs from the embodiment shown in Figure 4 in that it also comprises a twist element 170. It will be appreciated that although the twist element 170 is only shown in combination with the first tension element 150 that the twist element 170 may be employed in a wing sail without the first tension element 150.

The twist element 170 extends between a twist connection 171 arranged on the second batten 140 and a lateral connection 172 arranged on a rigid linkage 300. The lateral connection 172 is laterally displaced from the second batten 140 (i.e. spaced apart from the second batten 140 in a direction transverse to the longitudinal direction of the second batten 140).

The twist connection 171 may be arranged on the second batten 140 or on an area of the second sail portion 120. The twist connection 171 may be in/on a fitting connected to the second batten 140 or second sail portion 120. The twist connection may be arranged on an outer surface of the second sail portion 120.

The twist connection 171 may not be a fixed connection such that the twist element 170 can be moved therethrough. The twist connection 171 may be a receiving portion arranged on or an opening in the second sail portion 120 or second batten 140 or fitting coupled to the second sail portion 120 or second batten 140 such that the twist element 170 is movable therethrough. The opening or receiving portion may be a loop, eyelet, channel or through-hole.

The lateral connection 172 may be a fixed connection i.e. such that at the leech connection 172, the twist element 170 does not move relative to the rigid linkage 300. The lateral connection 172 may be a receiving portion configured to attach to or be attached to the twist element 170. The lateral connection 172 may be a protrusion to which the twist element 170 is affixed or tied and/or may be a point on rigid linkage 300 to which the twist element 170 is attached, for example, with stitching, tape, adhesive or other mechanical fastening. The lateral connection 172 may be an opening or eyelet to which the twist element 170 is tied. The lateral connection 172 is arranged on rigid linkage 300.

In this exemplary implementation, the rigid linkage 300 has an abutting portion 301 and a protruding portion 302. Rigid linkage 300 also has a coupling portion 303 coupled to the second batten luff end 142. The protruding portion 302 is outside the cavity 105 formed by the first and second sail portions 110, 120 and laterally displaced from the second batten luff end 142. The abutting portion 301 is inside the cavity 105 formed by the first and second sail portions 110, 120. In this exemplary implementation, the abutting portion 301, the protruding portion 302 and the coupling portion 303 form parts of a unitary rigid member, which, in this exemplary arrangement, is shaped as a triangle having an edge proximal to the mast and extending in a direction transverse to the longitudinal direction of the second batten 140. In this example, the protruding portion 302 and the abutting portion 301 are each sections of the unitary member. Each of the protruding portion 302 and the abutting portion 301 form a comer of the triangle and are arranged on the edge of the triangle proximal to the mast 50. The abutting portion 301 is spaced apart from the mast 50 when the twist element 170 is slack and configured to abut the mast on tensioning the twist element 170. On tensioning the twist element 170, the rigid linkage 300 rotates such that the abutting portion 301 abuts the mast 50. On further tensioning the twist element 170, a torque is generated between the second batten 140 and the mast 50.

The rigid linkage 300 is mounted to the luff end 141 of the second batten 140. The lateral connection 172 is arranged on the protruding portion 301. More specifically, the lateral connection 172 is arranged on the region of the rigid linkage 300 distal from the mast 50 and second batten 140. The rigid linkage 300 is rigidly coupled to a portion of the second batten luff end 142 via its coupling portion 303 such that the rigid linkage 300 does not move relative to the portion of the length of the second batten luff end 142.

The twist element 170 is inextensible. In this exemplary implementation, the twist element 170 may be a line, chord or tape.

The twist element 170 extends outside the wing sail 100 (i.e. outside the cavity 105 formed between the first and second sail portions 110, 120) and the tension element extends within the wing sail 100 (i.e. within the cavity 105 formed between the first and second sail portions 110, 120).

In use, as discussed above, in respect of Figure 4, the first tension element 150 may be pulled through the first luff connection 151 to apply tension to the first tension element 150 to move the first leech connection 152 towards the first luff connection 151 and towards the separator connection 153 thereby bending the first batten leech end 132 towards its luff end 131 to increase its curvature and moving the first luff connection 151 towards the separator connection 153 to reduce the spacing therebetween.

The twist element 170 may be pulled through the twist connection 171 to thereby reduce the length of the twist connection between the twist connection 171 and the lateral connection 172. This causes the rigid linkage 300 to rotate about the second batten luff end 141 and abut the mast 50 such that on further tensioning of the twist element 170, a torque is induced between the second batten 140 and the mast 50 and the second batten 140 rotates about the mast 50. Rotation of the second batten 140 about the mast in turn induces a rotation in the first batten 130 about the mast 50.

Rotation of the first and second battens 130, 140 about the mast 50 changes the angle attack of the wing sail 100 in the area proximal to the first and second battens 130, 140 and so induces twist in the wing sail 100.

Accordingly, as demonstrated by Figure 10, by using the second tension element 160, the twist and camber of the upper part of the wing sail 100 to which the first and second battens 130, 140 may be connected may be opposite from the twist and camber of the lower part of the wing sail 100 which may otherwise be controlled, for example, by the out haul. Indeed, it can be seen that the first and second battens 130, 140 may be rotated in the opposite direction relative to the mast 50 compared to the third and fourth battens 180, 190 thereby changing the angle of attack for the upper part of the wing sail 100 relative to the lower part of the wing sail 100 thereby inducing twist of the wing sail 100. It can also be seen the curvature (camber) induced in the first and second battens 130, 140 is opposite from the curvature (camber) induced in the third and fourth battens 180, 190. Accordingly, the upper and lower parts of the wing sail 100 may have opposite camber.

Although only one rigid linkage 300 coupled to the second batten 140 has been shown, it is of course contemplated that a similarly configured rigid linkage coupled to the first batten 130 may be provided.

The present invention is also described in accordance with the following statements. The present invention is an improvement of the original invention by Johnston, Patrick Murray (Patents AU1986052399, US4,766,831) and an alternative to an invention by Gregory Owen Johnston and Patrick Murray Johnston files under PCT application PCT/AU2014/050264. The present invention provides for the control of the curvature, or camber, of the leeward battens of a double surface wing sail. Further, this invention describes the ability to control the cambers in the upper part of a wing sail such that the cambers in the upper part of the wing sail are opposite in curvature to the cambers in the lower part of the wing sail. Further, it provides a means whereby the cambers in the sail are controlled by means of applying a bending moment on the battens.

As with the previous inventions cited above, the wing sail being controlled in the present invention is characterised in that comprises a flexible sail comprising two substantially identical flexible sail portions, each having a leach and a luff, the flexible sail portions being arranged to give the sail an effective thickness which is substantially greater than either of the flexible sail portions individually and a pocket means arranged to receive an elongated batten having longitudinal flexure which stiffen the sail portions from luff to leech. Further, the battens in each sail portion are arranged so that they have similar vertical spacing and similar lengths such that the battens at the same vertical position of each of the pair of sails can be considered a pair of battens.

The present invention differs from the cited inventions in that rather than using a counter rotation of the mast to induce the camber, the mast is a “D” shaped section which is rotated towards the wind to provide an aerodynamically smooth leading edge to the aerofoil.

In accordance with one aspect of the present invention, the curvature of the leeward batten is increased by applying tension between the luff end and leech end the batten which in turn compresses the batten causing it to bend (see Figure 2).

In accordance with a further aspect of the present invention, the curvature of the windward batten is reduced by applying less tension between the luff end and leech end the batten which reduces the compression in the batten causing it to bend less.

In accordance with a further aspect of the present invention, the tension between the luff and leech ends of the battens is provided by a differentially tensioning the battens in a pair from the port and starboard sail portions such that one batten is compressed to increase camber and the other is relatively less tensioned to reduce camber in such a manner as to create an asymmetric shape where one sail portion has relatively less camber than the other sail portion. (See Figure 3)

In accordance with a further aspect of the present invention, the tension line from the leech of one batten in a pair of battens can be connected/tethered partway along the other batten or batten pocket of the pair, towards to luff to keep the leech ends of the batten pair together laterally.

In accordance with a further aspect of the present invention, the tension line from the leech of one batten in a pair of battens can be tethered partway along the other batten or batten pocket of the pair, towards to luff such that tension in the line pulls the leech of one batten towards the tethering position on the other batten resulting in a torque being applied to the batten pair. (See Figure 4).

In accordance with a further aspect of the present invention, each tension line is lead through a pulley so that it can lead along the vertical length of the luff such that the tension can be controlled from the bottom of the sail. (See Figure 6).

In one embodiment of the present invention, the tension in the tension lines are adjusted by the lines being attached to quadrant or lever arms mounted on a boom at either the top or the bottom of the sail so that when an angular change in the plane of the cross section of the mast is induced between the boom and the mast the tension between the leech end of each batten and the luff end each the batten increases or decreases respectively, depending upon the direction and magnitude of the angular displacement.

Other embodiments which lead the tension line along the opposite batten are also contemplated. For example, the difference in tension between the sail portions in the batten pair at the foot or the bottom of the sail can be achieved by a connection on the boom where the sails are attached (the clew of the sail).

In accordance with a further aspect of the present invention, the tension in the tension lines towards the top of the sail are adjusted such that a clockwise angular displacement between mast and boom when viewed from the top of the wing results in the tension lines attached to the leeches on the starboard sail portion to be tensioned more than the tension lines attached to the leeches on the port sail portion such that more camber is induced in the starboard sail portion than the port sail portion, thus causing the sail portions at the top of the sail to camber in the opposite direction to the camber at the bottom of the sail. An anticlockwise angular displacement would have a correspondingly opposite effect. (See Figure 5).

In one embodiment of the present invention, tension lines are only used on the upper section of the sail such that it can be controlled separately from lower sections.

In accordance with a further aspect of the present invention, the uppermost batten pair in the sail portions are located at the uppermost edge of the sail portions.

In accordance with a further aspect of the present invention, a frame is located at the luff of each of the uppermost battens which extends laterally from the luff of the sail portions (in a plane substantially in the same plane as the cross section of the mast) such that it extends outwards substantially perpendicular to the luff and inwards substantially perpendicular to the luff such that if a rearward load is applied to the outermost end of the frame, the frame makes contact with the rear face of the mast so as to resist the applied load.

In accordance with a further aspect of the present invention, a twist control line is attached from the batten near the leech to near the outermost extremity of the lateral frame such that a torque can be applied to the batten to cause it to rotate about the luff towards the outermost extremity of the lateral frame. (See Figure 10).

In accordance with a further aspect of the present invention, the twist control line is lead to the luff and then vertically along the luff such that the twist control line tension can be adjusted from the bottom or top of the sail.

In one embodiment of the present invention, the frames described above are also fitted to other batten pairs below the top batten pair.

In one embodiment of the present invention, the tension in the twist control lines is adjusted by the line being attached to a quadrant or lever arm mounted on a boom at either the top or the bottom of the sail so that when an angular change in the plane of the cross section of the mast is induced between the boom and the mast the tension in the twist control line increases or decreases respectively, depending upon the direction and magnitude of the angular displacement.

In one embodiment of the present invention, there is a twist control line and a lateral frame on each uppermost batten.

In accordance with a further aspect of the present invention, the tension in twist control lines at the top of the sail are adjusted such that a clockwise angular displacement between mast and boom when viewed from the top of the wing results in the twist control line on the port sail portion to be tensioned and the twist control line on the starboard sail portion such to be loosened, thus causing the sail portions at the top of the sail to twist in an opposite direction to the angular displacement between the mast and the boom at the bottom of the sail. An anticlockwise angular displacement would have a correspondingly opposite effect.

In accordance with a further aspect of the present invention, a frame is located at the luff of each of the battens in a batten pair, and which extends laterally from the luff of the sail portions (in a plane substantially in the same plane as the cross section of the mast) such that it extends inwards substantially perpendicular to the luff so that when the mast is rotated the frame contacts the rear face of the mast and a bending moment is applied to the batten to camber the batten in the same direction as the mast rotation and to maintain an aerodynamically smooth attachment of the batten to the mast. (See Figure 7).

In accordance with a further aspect of the present invention, the frames above are attached only to the sail portion such that it is possible for frames on the battens on the windward side of the sail to move away from the rear face of the mast such that the windward batten can have relatively less camber than the leeward batten. (See Figure 8).

In accordance with a further aspect of the present invention, the frames on a batten pair are linked such that the angular displacement between the frames is not rigid but is limited such that initially the frames are not restricted in their angular displacement such that the windward batten cambers less than the leeward batten but at increase mast rotation and hence increased angular displacement between the frames, contact is made that restricts further angular displacement, thus increasing the camber in both leeward and windward battens with further mast rotation. (See Figure 9).

In accordance with a further aspect of the present invention, the sail portions are substantially flat in that there is no or minimal precambered shape formed into each sail portion (i.e. less than a few percentage points of the length of the batten or sail chord), such that each sail portion can adopt a shape of cambered in one direction at the bottommost portions of the sail to cambered in the opposite direction in the uppermost portions of the sail without the introduction of stresses which result in substantial creases and local deformations in the surface of the sail portion. The present invention contemplates the use of purchase systems in any of the control lines or tension lines.

The present invention contemplates other embodiments which control the positions of the end of the battens, such as actuators, rams, etc.

Claims

1. A wing sail having a leech and a luff defining a first direction therebetween, the wing sail comprising: first and second sail portions, wherein the first sail portion comprises a first sail portion luff and a first sail portion leech, wherein the second sail portion comprises a second sail portion luff and a second sail portion leech, wherein the first sail portion luff and the second sail portion luff are spaced apart from each other in a direction transverse to the first direction to define a thickness of the wing sail; a first batten in contact with the first sail portion, the first batten extending from a first batten luff end to a first batten leech end, wherein the first batten luff end is proximal to the first sail portion luff and the first batten leech end is proximal to the first sail portion leech; and a first tension element extending from a first luff connection to a first leech connection, wherein the first luff connection is proximal to the first batten luff end and the first leech connection is proximal to the first batten leech end, such that on tensioning of the first tension element, the first tension element draws the first leech connection directly towards the first luff connection thereby bending the first batten leech end towards the first batten luff end to change the shape of the first sail portion.

2. The wing sail of claim 1 further comprising a second batten in contact with the second sail portion, the second batten extending from a second batten luff end to the second batten leech end, wherein the second batten luff end is proximal to the second sail portion luff and the second batten leech end is proximal to the second sail portion leech.

3. The wing sail of claim 2 further comprising a second tension element extending from a second luff connection to a second leech connection, wherein the second luff connection is proximal to the second batten luff end and the second leech connection is proximal to the second batten leech end, such that on tensioning of the second tension element, the second tension element draws the second leech connection towards the second luff connection thereby bending the second batten leech end towards the second batten luff end to change the shape of the second sail portion, wherein the first and second tension elements are optionally separately controllable.

4. The wing sail of any preceding claim, wherein the first tension element forms a straight line between the first luff connection and the first leech connection when tensioned and/or wherein the second tension element forms a straight line between the second luff connection and the second leech connection when tensioned.

5. The wing sail of any one of claims 2 to 4, wherein the first batten leech end is free to move relative to the second batten leech end.

6. The wing sail of any one of the preceding claims, wherein the first tension element extends from the first leech connection proximal to a separator connection proximal to the second batten such that on tensioning the first tension element, the first tension element moves the first batten towards the second batten and/or wherein the second tension element extends from the second leech connection to a separator connection proximal to the second batten such that on tensioning the second tension element, the second tension element moves the first batten towards the second batten.

7. The wing sail of any one of claims 1 to 5, wherein one or more of the leech connection(s) are a fixed connection.

8. The wing sail of any one of claims 1 to 6, wherein the first tension element is moveable through the first leech connection such that on tensioning the first tension element, the length of the first tension element between the first luff connection and the first leech connection is reduced and/or wherein the second tension element is moveable through the second leech connection such that on tensioning the second tension element, the length of the second tension element between the second luff connection and the second leech connection is reduced.

9. The wing sail of any one of claims 1 to 8, wherein one or more of the luff connection(s) are a fixed connection.

10. The wing sail of any one of claims 1 to 8, wherein the first tension element is moveable through the first luff connection such that on tensioning the first tension element, the length of the first tension element between the first luff connection and the first leech connection is reduced and/or wherein the second tension element is moveable through the second luff connection such that on tensioning the second tension element, the length of the second tension element between the second luff connection and the second leech connection is reduced.

11. The wing sail of any preceding claim, wherein one or more of the leech connection(s) and/or luff connection(s) are arranged on the sail portions.

12. The wing sail of any one of claims 1 to 10, wherein one or more of the leech connection(s) and/or luff connection(s) are arranged on the respective battens.

13. The wing sail of any preceding claim, wherein one or more of the batten(s) is received in a corresponding pocket on the respective sail portion, optionally wherein one or more of the leech connections and/or luff connections are arranged on the pocket(s).

14. The wing sail of any preceding claim, wherein the first and/or second tension elements are a flexible, inextensible member, optionally wherein the first and/or second tension elements are tension lines.

15. The wing sail of any preceding claim, wherein the luff and leech connections are arranged in the upper half of the respective sail portions.

16. The wing sail of any preceding claim, wherein the first batten and the second batten are arranged in the upper half of the respective sail portions.

17. The wing sail of any preceding claim, wherein the first and second sail portions are of the same shape and size, optionally wherein the first and second sail portions are substantially identical.

18. The wing sail of any preceding claim, wherein the first and second sail portions are arranged to give the sail a thickness which is substantially greater than either of the first and second sail portions individually.

19. The wing sail of any preceding claim wherein the first and second battens are elongated and have longitudinal flexure which stiffen the respective sail portion from luff to leech.

20. The wing sail of any preceding claim, wherein the first batten is one of a plurality of first battens connected to the first sail portion and the second batten is one of a plurality of second battens connected to the second sail portion, wherein optionally the first plurality of battens have similar vertical spacing and similar lengths to the second plurality of batten such that the batten of the first plurality of battens at the same vertical position as the batten of the second plurality of battens are a pair of battens.

21. The wing sail of any preceding claim, wherein the first and second sail portions are flexible.

22. The wing sail of any preceding claim, wherein the first and second sail portions are flat panels having a curvature of less than 2% in any direction when not attached to the mast and when the first and second tension elements are slack.

23. The wing sail of any preceding claim, wherein the first and/or second tension element extend within a cavity formed between the first and second sail portions.

24. A rigging comprising: a mast; and the wing sail of any preceding claim, wherein the first sail portion and the second sail portion are each mounted to the mast.

25. The rigging of claim 24, wherein the mast comprises a leading edge and a trailing edge, optionally wherein the first sail portion and the second sail portion are each mounted to and spaced apart along the trailing edge of the mast.

26. The rigging of claim 25, where the leading edge defines a convex surface and the trailing edge defines a flat surface, optionally wherein the mast is D-shaped.

27. The rigging of any one of claims 24 to 26, wherein one or more of the luff connections are arranged on the mast.

28. A method of using the wing sail of any of claims 1 to 23 or the rigging of any one of claims 24to 27, the method comprising: applying tension to the first tension element to bend the leech end of the first batten towards the luff end of the first batten to thereby change the shape of the first sail portion.

29. A rigging comprising: a mast having a leading edge and a trailing edge defining a first direction therebetween and a second direction transverse to the first direction; a wing sail having a leech and a luff, wherein the wing sail is pivotally attached to the mast and comprises: first and second sail portions, each having a leech and a luff, wherein the first sail portion luff and the second sail portion luff are spaced apart from each other in the second direction to define an effective thickness of the wing sail; a first batten in contact with the first sail portion, the first batten extending from a first batten luff end to a first batten leech end, wherein the first batten luff end is proximal to the first sail portion luff and the first batten leech end is proximal to the first sail portion leech; and a rigid first stop extending along and coupled to the first batten luff end and extending at least partially across the thickness of the wing sail, wherein the first stop is configured such that when the mast is rotated in a first rotational direction, the first stop abuts the trailing edge of the mast and exerts a bending force on the first batten, to thereby change the shape of the first sail portion.

30. The rigging of claim 29. wherein the wing sail is pivotally attached to the trailing edge of the mast.

31. The rigging of claim 29 or claim 30, wherein the first stop is configured such that a separation between the first stop and the mast increases on rotation of the mast in a second rotational direction, which is opposite from the first rotational direction.

32. The rigging of any one of claims 29 to 31, wherein the first stop is configmed to abut the mast on rotation of the mast from an initial position through a first threshold angle in the first rotational direction and wherein further rotation of the mast beyond the first threshold angle exerts the bending force on the first batten to thereby change the shape of the first sail portion.

33. The rigging of any one of claims 29 to 32, wherein: the wing sail further comprises a second batten in contact with the second sail portion, the second batten extending from a second batten luff end to a second batten leech end, wherein the second batten luff end is proximal to the second sail portion luff and the second batten leech end is proximal to the second sail portion leech; and a rigid second stop extending along and coupled to the second batten luff end and extending at least partially across the thickness of the wing sail, wherein the second stop is configured to abut the mast such that rotation of the mast from in a second rotational direction, which is opposite to the first rotational direction, exerts a bending force on the second batten, to thereby change the shape of the second sail portion.

34. The rigging of claim 33, wherein the second stop is configured such that a separation between the second stop and the trailing edge of the mast increases on rotation of the mast in the first rotational direction.

35. The rigging of claim 33 or claim 34, wherein the second stop is configured to abut the mast on rotation of the mast from an initial position through a second threshold angle in the second rotational direction and wherein further rotation of the mast beyond the second threshold angle exerts the bending force on the second batten to thereby change the shape of the second sail portion.

36. The rigging of any one of claims 29 to 35, wherein the first stop is rigidly coupled to the first batten luff end and/or wherein the second stop is rigidly coupled to the second batten luff end.

37. The rigging of any one of claims 29 to 36, wherein the first stop is configmed such that the first threshold angle is less than 90° and/or wherein the second stop is configured such that the second threshold angle is less than 90°.

38. The rigging of any one of claims 29 to 37, wherein the first batten is pivotally mounted at the trailing edge of the mast and/or wherein the second batten is pivotally mounted at the trailing edge of the mast.

39. The rigging of any one of claims 29 to 38, wherein the first stop and the second stop are coupled together by a linking element that restricts movement of the first stop relative to the second stop beyond an upper limit, such that (i) rotation of the mast in the first direction from the neutral position causes the second stop to move relative to the first stop such that a separation between the second stop and the mast increases until the upper limit is reached and further rotation of the mast exerts a bending force on the first and second batten to thereby change the shape of the first and second sail portions; and (ii) rotation of the mast in the second direction from the neutral position causes the first stop to move relative to the second stop such that a separation between the first stop and the mast increases until the upper limit is reached and further rotation of the mast exerts a bending force on the first and second battens to thereby change the shape of the first and second sail portions.

40. The rigging of claim 39, wherein the linking element restricts angular displacement of the first stop relative to the second stop beyond the upper limit, wherein the upper limit is an angle of maximum angular displacement between the first stop and the second stop.

41. The rigging of any one of claims 29 to 40, wherein the first stop and/or the second stop are rigid.

42. The rigging of any one of claims 29 to 41, wherein the leading edge defines a convex surface and the trailing edge defines a flat surface, wherein optionally the mast is D-shaped.

43. The rigging of any one of claims 29 to 42, wherein the first stop and/or the second stop extend substantially in the same plane as the cross section of the mast, optionally perpendicular to the luff of the respective sail portion.

44. The rigging of any one of claims 29 to 43, wherein the first stop and/or the second stop are plates or frames.

45. The rigging of any one of claims 29 to 44, wherein the first batten leech end is free to move relative to the second batten leech end.

46. The rigging of any one of claims 29 to 45, wherein the first stop and/or the second stop are arranged within the cavity formed by the first and second sail portions.

47. The rigging of any one of claims 29 to 46, wherein the first stop and/or the second stop are configured to abut the trailing edge of the mast.

48. A method of using the rigging of any one of claims 29 to 47, wherein the first sail portion is the leeward sail portion and the second sail portion is the windward sail portion, the method comprising: rotating the mast in a first rotational direction such that at least a portion of the first stop abuts the trailing edge of the mast and a bending force is exerted on the first batten, to thereby change the shape of the first sail portion.

49. A rigging comprising: a mast having a leading edge and a trailing edge defining a first direction therebetween and a second direction transverse to the first direction; and a wing sail mounted to the mast, the wing sail having a leech and a luff, the wing sail comprising: first and second sail portions, wherein the first sail portion comprises a first sail portion luff and a first sail portion leech, wherein the second sail portion comprises a second sail portion luff and a second sail portion leech, wherein the first sail portion luff and the second sail portion luff are spaced apart from each other along the second direction to define a thickness of the wing sail; a first batten in contact with the first sail portion, the first batten extending from a first batten luff end to a first batten leech end, wherein the first batten luff end is proximal to the first sail portion luff and the first batten leech end is proximal to the first sail portion leech; and a first twist element extending from a first twist connection to a first lateral connection, wherein the first twist connection is proximal to the first batten and the first lateral connection is laterally displaced from the first batten and arranged on a first rigid linkage such that tensioning the first twist element causes rotation of the first batten relative to the mast.

50. The rigging of claim 49 further comprising: a second batten in contact with the second sail portion, the second batten extending from a second batten luff end to a second batten leech end, wherein the second batten luff end is proximal to the second sail portion luff and the second batten leech end is proximal to the second sail portion leech; and a second twist element extending from a second twist connection to a second lateral connection, wherein the second twist connection is proximal to the second batten and the second lateral connection is laterally displaced from the second batten and arranged on a second rigid linkage, such that tensioning the second twist element causes rotation of the second batten relative to the mast.

51. The rigging of claim 49 or claim 50, wherein the first and second sail portions define a cavity therebetween, wherein the first and/or second lateral connections are arranged outside the cavity.

52. The rigging of any one of claims 49 to claim 51, wherein the first linkage is coupled to the mast and/or wherein the second linkage is coupled to the mast.

53. The rigging of claim 52, wherein the first linkage is mounted on the mast and/or wherein the second linkage is mounted on the mast.

54. The rigging of claim 52 or claim 53, wherein the first linkage is a first arm extending from the mast in a direction transverse to the longitudinal direction of the first batten and/or wherein the second linkage is a second arm extending from the mast in a direction transverse to the longitudinal direction of the second batten.

55. The rigging of claim 54, wherein the first lateral connection is arranged on a portion of the first arm distal from the mast and wherein the second lateral connection is arranged on a portion of the second arm distal from the mast.

56. The rigging of any one of claims 49 to 51, wherein the first linkage is coupled to the first batten and/or wherein the second linkage is coupled to the second batten.

57. The rigging of claim 56, wherein the first linkage is configured such that on tensioning the first twist element the first linkage abuts the mast and further tensioning of the first twist element causes the first batten to rotate about the mast; and/or wherein the second linkage is configured such that on tensioning the second twist element the second linkage abuts the mast and further tensioning of the second twist element causes the second batten to rotate about the mast.

58. The rigging of claim 57, wherein the first linkage comprises a first abutting portion configured to abut the mast on tensioning the tension element, a first protruding portion laterally spaced from the first batten on which the first lateral connection is arranged and a first coupling portion configured to couple to the first batten and/or wherein the second linkage comprises a second abutting portion configured to abut the mast on tensioning the tension element, a second protruding portion laterally spaced from the second batten on which the second lateral connection is arranged and a second coupling portion configured to couple to the second batten.

59. The rigging of claim 58, wherein the first abutting portion, the first coupling portion and the first protruding portion are rigidly coupled together such that they do not move relative to each other and/or wherein the second abutting portion, the second coupling portion and the second protruding portion are rigidly coupled together such that they do not move relative to each other.

60. The rigging of claim 58 or claim 59, wherein the first abutting portion extends in a direction transverse to the longitudinal direction of the first batten and away from the second batten and the first protruding portion extends in a direction transverse to the longitudinal direction of the first batten and towards the second batten.

61. The rigging of any one of claims 58 to 60, wherein the first protruding portion forms part of a first protruding arm extending from the first batten in a direction transverse to the longitudinal direction of the first batten and away from the second batten and wherein the first abutting portion forms part of a first abutting arm extending in a direction transverse to the longitudinal direction of the first batten and towards the second batten; and/or wherein the second protruding portion forms part of a second protruding arm extending from the second batten in a direction transverse to the longitudinal direction of the second batten and away from the second batten and wherein the second abutting portion forms part of a second abutting arm extending in a direction transverse to the longitudinal direction of the second batten and towards the second batten.

62. The rigging of any one of claims 58 to 61, wherein the first coupling portion is configured to couple to at least a portion of the first batten luff end; and/or wherein the second coupling portion is configured to couple to at least a portion of the second batten luff end.

63. The rigging of claim 62, wherein the first coupling portion extends along at least a portion of the first batten luff end and/or wherein the second coupling arm extends along at least a portion of the second batten luff end.

64. The rigging of claim 63, wherein the first coupling portion forms part of a first coupling arm extending in a direction parallel to the longitudinal direction of the first batten and/or wherein the second coupling portion forms part of a second couphng arm extending in a direction parallel to the longitudinal direction of the second batten.

65. The rigging of any one of claim 56 to 64, wherein the first linkage is spaced apart from the mast when the twist element is not under tension and/or wherein the second linkage is spaced apart from the mast when the twist element is not under tension.

66. The rigging of any one of claims 58 to65, wherein the first abutting portion, the first coupling portion and the first protruding portion are integrally formed and/or wherein the second abutting portion, the second coupling portion and the second protruding portion are integrally formed.

67. The rigging of any one of claims 58 to 66, wherein the first and second sail portions define a cavity therebetween, wherein the first abutting portion extends within the cavity and the first protruding portion extends outside the cavity and/or wherein the second abutting portion extends within the cavity and the second protruding portion extends outside the cavity.

68. The rigging of any one of claims 49 to 67, wherein the first twist connection and/or the second twist connection proximal is a fixed connection.

69. The rigging of any one of claims 49 to 67, wherein the first twist element is moveable through the first twist connection such that on tensioning the first twist element, the length of the first twist element between the first lateral connection and the first twist connection is reduced and/or wherein the second twist element is moveable through the second twist connection such that on tensioning the second twist element, the length of the second twist element between the second lateral connection and the second twist connection is reduced.

70. The rigging of any one of claims 49 to 69, wherein the first lateral connection and/or the second lateral connection is a fixed connection.

71. The rigging of any one of claims 49 to 69, wherein the first twist element is moveable through the first lateral connection such that on tensioning the first twist element, the length of the first twist element between the first lateral connection and the first twist connection is reduced and/or wherein the second twist element is moveable through the second lateral connection such that on tensioning the second twist element, the length of the second twist element between the second lateral connection and the second twist connection is reduced.

72. The rigging of any one of claims 49 to 71, wherein the first twist element forms a straight line between the first lateral connection and the first twist connection when tensioned and/or wherein the second twist element forms a straight line between the second lateral connection and the second twist connection when tensioned.

73. The rigging of any one of claims 49 to 72, wherein the first twist connection is proximal to the first batten leech end and/or the second twist connection is proximal to the second batten leech end.

74. The rigging of any one of claims 49 to 73, wherein the first twist connection is arranged on the first flexible sail portion or on the first batten and/or the second twist connection is arranged on the second flexible sail portion or on the second batten.

75. The rigging of any one of claims 49 to 74, wherein the first batten leech end is free to move relative to the second batten leech end.

76. The rigging of any one of claims 49 to 75, wherein the first batten is received in a first pocket on the first sail portion and/or the second batten is received in a second pocket on the second sail portion.

77. The rigging of claim 76, wherein the first twist connection is arranged on the first pocket and/or the second twist connection is arranged on the second pocket.

78. The rigging of any one of claims 49 to 77, wherein the first and/or second twist elements comprise a flexible member, an inextensible member and/or twist lines.

79. The rigging of any one of claims 49 to 78, wherein the first twist connection and first lateral connection are arranged in the upper half of the wing sail and/or wherein the second twist connection and the second lateral connection are arranged in the upper half of wing sail.

80. A method of using the rigging of any one of claims 49 to 79, the method comprising: applying tension to the first twist element to rotate the first batten relative to the mast.