The present invention is related to a sail for producing propulsive power on a vessel and a vessel or a sailboat comprising such a sail.

A type of sail which is commonly used in high performance racing and sail development is the wing sail. The wing sails that are made today comprise a frame and a surface covering the frame giving the sail the shape of a wing. The problem with existing wing sails is that the sails are rigid constructions such that the lift force acting on the sail can not be adjusted or can only be adjusted to a limited degree. Generally, airfoil shaped sails in use today have limited possibilities for adjustment of the shape of the cross-section of the sail once the sail construction including the mast, is mounted on the deck of the sailboat.

Other, more commonly used and simpler sails are made up of a layer having a curved shape such that a lift force is created on the sail during sailing. The problem with these sails is again that once the sail is rigged on the sailboat, there are very limited possibilities for adjustment of the sail so as to adjust the lift forces acting on the sail during sailing.

The objective of the present invention has therefore been to develop a sail which is adjustable such that the lift forces on the sail can be adjusted during sailing.

A further object of the present invention has been to develop a sail which can be continuously adjusted during sailing.

These objectives are achieved with a sail as defined in claim 1 and a sailboat as defined in claim 35. Further embodiments of the sail and the sailboat are defined in the dependent claims.

The sail generally has a cross-sectional shape of an airfoil which provides a lift or a propulsive force on the sail, but there is also an embodiment which can be used with only one layer. The sail preferably comprises two separate layers (i.e. so-called sail canvases) which form a generally airfoil- shaped sail, when subjected to a wind load, and preferably a cap unit which covers the leading edges of the two layers. The sail may further be provided with shape forming elements which are used to help forming the shape of the two layers and/or the cap unit into the desired shape at any given time during sailing. The sail may also be provided with one or more tension elements which are used to adjust the shape of the two layers and the cap unit, preferably by adjusting the tension in the first layer and/or the second layer and/or the cap unit. Tension elements may also be used to adjust shape of the shape forming elements, for example by adjusting the tension in the shape forming elements, such that the desired shape of the shape forming elements is obtained. The tension elements may be cords, ropes, wires, pumps, motors or any other device that can provide tension in the two layers and/or the cap unit and/or the shape forming elements. The two layers are preferably independently adjustable, and the cap unit can be adjusted independently of the adjustment of the two layers. In this way a very flexible sail is obtained for which the cross-sectional shape, which generally has the shape of an airfoil, can be easily adjusted to the desired shape at any moment during sailing.

There is provided a sail for producing propulsive power or lift in a fluid. The device comprises a first layer and a second layer where the first layer and the second layer are connected along at least one corresponding side. The first layer and the second layer define a cross-sectional shape of the device substantially perpendicular to a longitudinal direction of the device. The shape of the first layer is adjustable and/or the shape of the second layer is adjustable such that the cross- sectional shape of the sail is adjustable.

The first layer comprises a plurality of sides with edge portions and an interior portion bounded by the edge portions and the second layer comprises a plurality of sides with edge portions and an interior portion bounded by the edge portions. The interior portion of the first layer and the interior portion of the second layer are unconnected which allows the first layer and the second layer to be adjusted independently. At least one edge portion of the first layer and a corresponding edge portion of the second layer are connected to each other. The first layer, the second layer and the cap unit are preferably made of a material, such as a canvas material, Kevlar® or any other suitable material or combinations of materials that will allow the shape of the first layer and/or the second layer, and thereby the cross-sectional shape of the sail, to be adjusted.

The shape of the first layer and the shape of the second layer are preferably independently adjustable, i.e. the shape of the first layer only may be adjustable or the shape of the second layer only may be adjustable or the shape of both the first layer and the shape of the second layer may be adjustable. By using independently adjustable first and second layers, the cross-sectional shape of the sail may be adjusted to virtually any desired shape and consequently the lift forces on the sail can be adjusted according to what is required or desired at any specific moment during sailing. At least one edge portion of the first layer and a corresponding edge portion of the second layer are connected to each other, for example by gluing, sewing or with ropes, but depending on the use of the sail several or all corresponding sides of the first layer and the second layer may be connected to each other. If the first layer and the second layer are connected along only one edge portion, it is preferably along the trailing edge of the sail.

In order to carry out adjustments of the two layers the sail preferably comprises a first layer adjustment element for adjustment of the shape of the first layer and/or a second layer adjustment element for adjustment of the shape of the second layer. The first layer adjustment element is preferably adapted for adjustment of the tension in the first layer whereby the shape of the first layer can be adjusted.

Similarly, the second layer adjustment element is preferably adapted for adjustment of the tension in the second layer whereby the shape of the second layer can be adjusted. The first layer adjustment element and the second layer adjustment element are preferably independently operable so that the tension in the first layer and the tension in the second layer can be adjusted independently, i.e. only the tension in the first layer may be adjusted or only the tension in the second layer may be adjusted or the tension in both the first layer and the second layer may be adjusted.

The first layer adjustment element and the second layer adjustment element may comprise various types of means or devices. The first layer adjustment element may for example comprise at least one first motor or at least one first pump for adjustment of the tension in the first layer and the second layer adjustment element may comprise at least one second motor or at least one second pump for adjustment of the tension in the second layer. Alternatively, the first layer adjustment element may comprise at least one first cord element, at least one first wire element or any similar suitable elements for adjustment of the tension in the first layer and the second layer adjustment element may comprise at least one second cord element, at least one second wire element or any similar suitable element for adjustment of the tension in the second layer. The at least one first cord element and the at least one second cord element may pass over one or more pulleys or other suitable devices for guiding the cord elements as necessary to one or more winches or similar devices which is suitable for adjustment of the tension in the cord element or to a position on the vessel where a person can operate the first and second cord elements manually to adjust the tension in the first and/or the second layer.

The first layer may further comprise at least one first layer shaping element for adjustment of the shape of the first layer. The at least one first layer tension element is preferably made of an elastic material so that the at least one first layer shaping element bends out radially when it is subjected to axial tension. The first layer shaping element preferably has an elongated shape, i.e. it has the shape of a rod or a stick or a similar object. The at least one first layer shaping element may be positioned in a pocket in the first layer where the pocket is adapted to the size of the at least one first layer shaping element, or the at least one first layer shaping element may be fastened to the first layer with straps or any other suitable fastening means.

Similarly, the second layer may further comprise at least one second layer shaping element for adjustment of the shape of the second layer, where the at least one second layer shaping element is preferably made of an elastic material so that the at least one second layer shaping element bends out radially when it is subjected to axial tension. The second layer shaping element preferably has an elongated shape, i.e. it has the shape of a rod or a stick or a similar object. The at least one second layer shaping element may be positioned in a pocket in the second layer where the pocket is adapted to the size of the at least one second layer shaping element, or the at least one second layer shaping element may be fastened to the second layer with straps or any other suitable fastening means.

The axial tension in the at least one first layer shaping element may be adjusted so that the at least one first layer shaping element bends out radially and thereby helps shaping the first layer into a desirable shape. In order to effectuate the axial tensioning of the at least one first layer shaping element, the sail may be provided with at least one first layer shaping element adjustment element for adjustment of the axial tension in the at least one first layer shaping element.

The at least one first layer shaping element may further be designed with a varying size of the cross-sectional area perpendicular to the longitudinal direction of the at least one first layer shaping element and/or a varying shape of said cross-sectional area and/or with a varying elasticity in the longitudinal direction of the at least one first layer shaping element, for example by designing the at least one first layer shaping element such that it comprises a plurality of different materials having different elasticities. In this way the at least one first layer shaping element may be designed to bend more along a desired part of the at least one first layer shaping element than along the remaining part of the at least one first layer shaping element when the at least one first layer shaping element is being subject to axial tension.

The axial tension in the at least one second layer shaping element may also be adjusted so that the at least one second layer shaping element bends out radially and thereby helps shaping the second layer into a desirable shape. In order to effectuate the axial tensioning of the at least one second layer shaping element, the sail may be provided with at least one second layer shaping element adjustment element for adjustment of the axial tension in the at least one second layer shaping element.

The at least one second layer shaping element may also be designed with a varying size of the cross-sectional area perpendicular to the longitudinal direction of the at least one second layer shaping element and/or a varying shape of said cross- sectional area and/or with a varying elasticity in the longitudinal direction of the at least one second layer shaping element, for example by designing the at least one second layer shaping element such that it comprises a plurality of different materials having different elasticities. In this way the at least one second layer shaping element may be designed to bend more along a desired part of the at least one second layer shaping element than along the remaining part of the at least one second layer shaping element when the at least one second layer shaping element is being subject to axial tension. The at least one first layer shaping element preferably extends from a first layer leading edge and backwards from the first layer leading edge, i.e. substantially in the direction of flow of air passing the sail during sailing. In the same way the at least one second layer shaping element preferably extends from a second layer leading edge and backwards from the second layer leading edge, i.e. substantially in the direction of flow of air passing the sail during sailing.

Preferably, at least a portion of the first layer along a first layer leading edge and at least a portion of the second layer along a second layer leading edge are stiff.

Increased stiffness along the leading edges, in addition to the inherent stiffness of the first layer and the second layer, may be obtained by providing the leading edges of the first layer and the second layer with reinforcing material such as glass fibres, Kevlar or any other suitable strengthening material.

The sail preferably comprises a cap unit which at least covers the first layer leading edge and the second layer leading edge and covers the gap between the leading edge of the first layer and the leading edge of the second layer. The cap unit is preferably provided with an aerodynamic shape and is preferably adjustably configured such that the trailing edges of the cap unit lies close to the first layer and the second layer respectively and the angle of attack may be adjusted.

In a similar way as the first layer and the second layer, the cap unit may comprise at least one cap unit shaping element for adjustment of the shape of the cap unit. The at least one cap unit shaping element is preferably made of an elastic material so that the at least one cap unit shaping element bends out radially when it is subjected to axial tension. The at least one cap unit shaping element preferably has an elongated shape, i.e. it has the shape of a rod or a stick or a similar object. The at least one cap unit shaping element may be positioned in a pocket in the cap unit where the pocket is adapted to the size of the at least one cap unit shaping element, or the at least one cap unit shaping element may be fastened to the cap unit with straps or any other suitable fastening means. The at least one cap unit shaping element may be attached to a connecting element extending backwards therefrom. The axial tension in the at least one cap unit shaping element may be adjusted so that the at least one cap unit shaping element bends out radially and thereby helps shaping the cap unit into a desirable shape. In order to effectuate the axial tensioning of the at least one cap unit shaping element, the sail is provided with at least one cap unit adjustment element for adjustment of the axial tension in the at least one cap unit shaping element. The adjustable shape of the cap unit can for example be used to change the angle of attack of the sail whilst the sailboat, on which the sail is mounted, is sailing. The at least one cap unit shaping element may also be designed with a varying size of the cross-sectional area perpendicular to the longitudinal direction of the at least one cap unit shaping element and/or a varying shape of said cross-sectional area and/or with a varying elasticity in the longitudinal direction of the at least one cap unit shaping element, for example by designing the at least one cap unit shaping element such that it comprises a plurality of different materials having different elasticities. In this way the at least one cap unit shaping element may be designed to bend more along a desired part of the at least one cap unit shaping element than along the remaining part of the at least one cap unit shaping element when the at least one cap unit shaping element is being subjected to axial tension. This can be particularly helpful in order to obtain the desired angle of attack on the sail during sailing.

The sail may further comprise at least one, but preferably a plurality of connecting elements which are adapted for connection of the sail to an external member such as a corresponding connecting element on a mast, a boom, a leech or any other suitable fixed place or point on a vessel. The connecting elements may be positioned within the interior of the sail or extend in part into the interior of the sail where one or more of the adjustable tension elements, such as the various first layer, second layer and cap unit adjustable tension elements mentioned above, preferably are connected to the at least one connecting element and/or passes through the at least one connecting element, for example by means of a ring for cords or by means of pumps, motors or any other suitable means that can be used to adjust the tension in the various tension adjustment elements. If the at least one connecting element is completely positioned in the interior of the sail, any external member to which the at least one connecting element is connected, will have to be brought into the interior of the sail and connected to the at least one connecting element with a quick connection or any other suitable connection.

The sail preferably comprises a plurality of adjustable tension means for adjusting the tension in and/or the shape of the various parts of the sail, such as the tension in and/or the shape of the first and second layers, the tension in and/or the shape of cap unit and possibly the tension in and/or the shape of other parts of the sail.

The sail may, as mentioned above, comprise at least one first layer adjustment element where the at least one first layer adjustment element extends between the first layer and the at least one connecting element, and where the at least one first layer adjustment element is adapted for adjustment of the tension in the first layer.

Increasing the tension in the first layer will straighten the first layer, while reducing the tension in the first layer will result in the first layer assuming a more curved shape. The extent of the change of the shape of first layer when the tension is increased or decreased will obviously depend on the wind load on the sail. Thus, by adjusting the tension in the first layer, the shape of the first layer is adjusted and thereby the cross sectional shape of the sail is adjusted.

The sail may also comprise at least one first adjustment element extending between the first layer and the cap unit where the at least one first adjustment element is adapted for adjustment of the distance between the first layer and the cap unit. It is preferable that the cap unit lies close to the first layer and that the transition zone between the cap unit and the first layer is as smooth as possible so as to avoid formation of turbulence and to obtain a smooth flow of fluid, i.e. normally air, over the transition zone between the cap unit and the first layer. Such an at least one first adjustment element will enable the adjustment of the distance between the first layer and the cap unit as desired. The at least one first adjustment element can also be configured such that the shape of the first layer and/or the cap unit is adjusted when the tension in the at least one first adjustment element, or the length of the at least one first adjustment element, is increased or reduced. The sail may further comprise, as mentioned above, at least one second layer adjustment element extending between the second layer and the at least one connecting element, and where the at least one second layer adjustment element is adapted for adjustment of the tension in the second layer. Increasing the tension in the second layer will straighten the second layer, while reducing the tension in the second layer will result in the second layer assuming a more curved shape. The extent of the change of the shape of second layer when the tension is increased or decreased will obviously depend on the wind load on the sail. Thus, by adjusting the tension in the second layer, the shape of the second layer is adjusted and thereby the cross sectional shape of the sail is adjusted. The sail may further comprise at least one second adjustment element extending between the second layer and the cap unit where the at least one second adjustment element is adapted for adjustment of the distance between the second layer and the cap unit. As mentioned above, it is preferable that the cap unit lies close to the second layer and that the transition zone between the cap unit and the second layer is as smooth as possible so as to avoid formation of turbulence and to obtain a smooth flow of fluid, i.e. normally air, over the transition zone between the cap unit and second layer. Such an at least one second adjustment element will enable the adjustment of the distance between the second layer and the cap unit as desired. The at least one second adjustment element can also be configured such that the shape of the at least one second layer and/or the cap unit is adjusted when the tension in the at least one second adjustment element, or the length of the at least one second adjustment element, is increased or reduced.

Furthermore, the cap unit may be attached to the first layer and to the second layer, in which case preferably the trailing edge of the cap unit is attached to the first layer and the second layer slidingly, or by fasteners like press studs or buttons, gluing, welding, stitching or any other suitable method or combination of methods for attachment of the cap unit to the first layer and the second layer.

The at least one first layer adjustment element and/or the at least one second layer adjustment element and/or the at least one first layer shaping element adjustment element and/or the at least one second layer shaping element adjustment element and/or the at least one cap unit adjustment element and/or the at least one first adjustment element and/or the at least one second adjustment element preferably comprise(s) at least one of the members in the following group: an actuator, a piston/cylinder assembly, a pump, a motor, a cord, a wire, a chain, a winch or any other actuator or device that would be suitable for adjusting the tension in the respective tension adjustment elements mentioned above, i.e. the at least one first layer adjustment element, the at least one second layer adjustment element, the at least one first layer shaping element adjustment element, the at least one second layer shaping element adjustment element, the at least one cap unit shaping element adjustment, the at least one first adjustment element, the at least one second adjustment element.

Furthermore, at least one first adjustment element may be slidingly connected to the cap unit. To obtain such a sliding connection, the at least one first adjustment element may in one end be attached to a slide which is slidingly connected to a corresponding guide element which is attached to the cap unit. This will ensure that the at least one first adjustment element automatically adjust its position of connection to the cap unit such that the direction of the force pulling on the cap unit is optimal, i.e. the force necessary to pull the cap unit and the first layer close to each other is minimized.

Similarly, at least one second adjustment element may be slidingly connected to the cap unit in the same way as explained above. The at least one second adjustment element may in one end be attached to a slide which is slidingly connected to a corresponding guide element which is attached to the cap unit. This will ensure that the at least one second adjustment element automatically adjusts its position of connection to the cap unit such that the direction of the force pulling on the cap unit will be optimal, i.e. the force necessary to pull the cap unit and the second layer close to each other is minimized.

The at least one first layer adjustment element and/or the at least one first layer shaping element adjustment element and/or the at least one second layer adjustment element and/or the at least one second layer shaping element adjustment element and/or the at least one cap unit adjustment element and/or the at least one first adjustment element and/or the at least one second adjustment element is or are preferably located within the interior of the sail. Thus, only ropes, wires etc. which must be pulled in or let out in order to adjust the various tension elements in the interior of the sail will normally be visible from the outside. If pumps or similar devices are used, which may for example be wirelessly controlled, all adjustment parts of the sail may be arranged within the interior of the sail. The at least one first layer adjustment element and/or the at least one first layer shaping element adjustment element and/or the at least one second layer adjustment element and/or the at least one second layer shaping element adjustment element and/or the at least one cap unit adjustment element may be connected to the at least one connecting element or a similar element which is suitable for the particular adjustment elements used, and preferably within the interior of the sail.

The sail is adapted for connection to at least one fixed point of the sail boat, for example the mast and/or a boom and/or a bowsprit and/or a forestay, where the connection provides no means for adjustment of first layer, second layer, cap unit or the shaping elements of the first layer, second layer and/or the cap unit through the fixed point. As mentioned above, all the adjustment elements for adjustment of these parts of the sail, which determines the cross-sectional shape of the sail, are located within the interior of the sail. The fixed point or points on the vessel, to which the sail is connected, therefore need no inherent properties or means for adjustment of the cross-sectional shape of the sail. The sail may further comprise at least one sail shaping element which preferably has an elongated shape, i.e. it has the shape of a rod or a stick or a similar object, and extends substantially from the sail' s leading edge to the sail' s trailing edge, i.e. from positions close to the leading edge and trailing edge since the sail shaping element preferably is located within the interior of the sail and therefore must be understood to be supported at positions close to, but not exactly at the leading edge and the trailing edge. The at least one sail shaping element may for example be attached to one of the connecting elements which is located close to the leading edge, and to a wire or similar which is running along the trailing edge of the sail. The at least one sail shaping element may also be supported in a pocket on the first layer or on the second layer or in a separate pocket attached to the sail at the connection between the first layer and the second layer. The at least one sail shaping element is preferably made of an elastic material which allows the at least one sail shaping element to bend out radially when it is subjected to an axial load. The sail shaping element is, as mentioned, preferably arranged in the interior of the sail, between the first layer and the second layer of the sail.

The sail may further be provided with at least one sail shaping element adjustment element for adjustment of the axial tension in the at least one sail shaping element, and thus the degree to which the at least one sail shaping element bends out radially. The at least one sail shaping element adjustment element is also preferably arranged in the interior of the sail and may comprise a rope, a cord or similar element which is attached to the at least one sail shaping element at the trailing end of the sail and further passes through the connecting element or any other suitable element close to the leading edge of the sail before continuing down to the vessel itself where the rope may be manually operated by a person or be attached to a manually operated or motorized winch which can be used to increase or reduce the tension in the rope. When the tension in the rope is increased by pulling in rope, the at least one sail shaping element will be forced to bend out due to increased axial tension in the at least one sail shaping element. Depending on the wind load on the sail during use, the at least one sail shaping element can be made to bend towards the first layer or the second layer and help providing the first layer or the second layer with a desired curved shape during sailing. The amount of bending of the at least one sail shaping element will obviously depend on the axial tension in the at least one sail shaping element and the elasticity of the material that the at least one sail shaping element is made of.

The at least one sail shaping element may further be designed with a varying size of the cross-sectional area perpendicular to the longitudinal direction of the at least one sail shaping element and/or a varying shape of said cross-sectional area and/or with a varying elasticity in the longitudinal direction of the at least one sail shaping element, for example by designing the at least one sail shaping element such that it comprises a plurality of different materials having different elasticities. In this way the at least one sail shaping element may be designed to bend more along a desired part of the at least one sail shaping element than along the remaining part of the at least one sail shaping element when the at least one sail shaping element is being subjected to axial tension. This can be particularly helpful in order to obtain the desired angle of attack on the sail during sailing.

In an embodiment of the sail which includes at least one sail shaping element, the sail may comprise only a single layer. The at least one sail shaping element still extends between a position close to the leading edge, where the at least one sail shaping element can be attached to a connecting element, and the trailing edge of the sail where the at least one sail shaping element is attached to the single layer. The at least one sail shaping element may be arranged in a pocket which is attached to the single layer of the sail or the at least one sail shaping element may be attached to the single layer with straps or any other suitable attachment means.

Apart from having only one layer instead of two layers, the rest of the design of this embodiment of the sail is the same as for the embodiment of the sail described above which comprises two adjustable layers, i.e. the first layer and the second layer, and at least one sail shaping element extending substantially from the sail' s leading edge to the sail' s trailing edge. It should be noted that all the adjustment elements mentioned above, i.e. the at least one first layer adjustment element and/or the at least one first layer shaping element adjustment element and/or the at least one second layer adjustment element and/or the at least one second layer shaping element adjustment element and/or the at least one cap unit adjustment element and/or the at least one first adjustment element and/or the at least one second adjustment element is or are preferably located within the interior of the sail and are preferably configured so that they can be operated from the vessel by an operator, either by operating the tension means by wireless control means such as Bluetooth™ or any other suitable wireless technology, or cable or manually by for example ropes, cords or similar elements which extend from the respective tension element down to deck when the sail is rigged such that one or more operators can pull in rope or let out rope as required during adjustment of the cross-sectional shape of the sail.

The sail is obviously particularly suitable for use on a sailboat, but may also be adapted for use on any other type of floating vessel. For example, when used on large ocean going vessels, in combination with regular ship engines, the fuel consumption may be considerably reduced.

There is also provided a vessel which is provided with a sail as described above where the sail is attached to the rig of the vessel. There is also provided a sailboat which is provided with a sail as described above where the sail is attached to the rig of the sailboat.

Preferably, the first layer and the second layer have at least three common attachment points to the rig.

The rig preferably comprises at least one mast or an element on the vessel to which the sail is connected, where the at least one connecting element of the sail is connected to a corresponding connecting element on the mast. Preferably the sail is provided with a plurality of connecting elements which are connected to

corresponding connecting elements on the mast or the element on the vessel to which the sail is connected. The sail according to the present invention with a number of non-limiting embodiments will now be explained in detail with reference to the figures where:

Figure 1 schematically illustrates an embodiment of the sail where the sail comprises adjustment elements in the form of one or more cords or lines to alter the tension in the first layer and/or the second layer and/or the first layer shaping element and/or the second layer shaping element and/or the cap unit shaping element. Figure 2 schematically illustrates an embodiment of the sail where the sail comprises adjustment elements comprising one or more pumps, motors, winches or similar adjustment elements to alter the tension in the first layer and/or the second layer and/or the first layer shaping element and/or the second layer shaping element and/or the cap unit shaping element.

Figure 3 schematically illustrates an embodiment of the sail where the sail comprises adjustment elements in the form of one or more cords or lines to alter the tension in the first layer and/or the second layer and/or the first layer shaping element and/or the second layer shaping element and/or the cap unit shaping element, where the cord runs in a zig-zag manner.

Figure 4 schematically illustrates the sail where some of the possible tensioning possibilities for the first layer, second layer and the cap unit are indicated.

Figure 5 schematically illustrates the first layer, the second layer, the cap unit and a connecting element of the sail.

Figure 6 schematically illustrates first layer and the second layer of the sail when no tension is applied to the layers and a fluid flows around the sail.

Figure 7 schematically illustrates the first layer and the second layer of the sail when tension is applied to a layer to straighten it and a fluid flows around the sail.

Figure 8 schematically illustrates in a cross section the sail when it has been manipulated with selected tension adjustment elements to form the shape of a wing or airfoil.

Figure 9 schematically illustrates an embodiment of the sail wherein a tension element is slidingly attached to the cap unit.

Figure 10 schematically illustrates an embodiment of the sail wherein a tension element is attached to the cap unit in one end and to another tension element in the other end.

Figure 11 schematically illustrates an embodiment of the sail where the sail is provided with a free sail shaping element in the interior of the sail where the sail shaping element extends between the leading edge and the trailing edge of the sail and is fastened to the sail only at its ends near the leading edge and the trailing edge of the sail.

It should be noted that the drawings of the various embodiments of the sail have been drawn to show important aspects of the sail. The figures are therefore not to scale and certain features and/or parts of the sail have been exaggerated in order to make the inventive features of the sail easy to grasp for a person skilled in the art.

Furthermore, the drawings are schematically drawn figures that show the important parts of the invention and leaves out features of sail which are not important for the understanding of how the present invention works. Figures 1-3 illustrate three slightly different variants of the sail 10 according to the present invention, with a transparent cap unit with only edge portions visible in order to illustrate the interior of the sail. The sail generally comprises two layers, a first layer 12 and a second layer 21 (see figures 4- 11), but since the sail is a side view of the sail, only the first layer is shown on the figures. The first layer and the second layer are, however, normally given the same shape, so a side view including the second layer 21 instead of the first layer would look substantially the same.

The first layer 12 is provided with a first layer leading edge 13, a first layer trailing edge 14 and a first layer lower edge 15 as indicated on figure 1. The first layer 12 further comprises a first layer edge portion 17 as indicated with the broken line L. The first layer edge portion 17 delimits a first layer interior portion 18 which is bounded by the first layer edge portions 17.

The second layer 21 is provided with corresponding second layer leading edge 22, second layer trailing edge 23 and second layer lower edge 24 (not shown on figures 1-3). The second layer 12 further comprises a second layer edge portion in the same way as the first layer. The second layer edge portion delimits a second layer interior portion which is bounded by the second layer edge portion also in the same way as the first layer 12.

The first layer edge portion and the corresponding second layer edge portion is generally a portion of the first layer and the second layer respectively which may be connected to each other. Generally, the first layer 12 and the second layer 21 are preferably attached to each other along at least one edge, for example along the trailing edge of the first layer and the second layer. The edge portions of the first layer and the second layer are then the portions of the first layer and the second layer which are connected to each other. The first layer 12 and the second layer 21 can be attached to each other by using a line, a rope or similar, by gluing or welding the first layer and the second layer together or any other suitable method for connecting the first and the second layer along one corresponding edge or several corresponding edges. The first layer interior portion 18 and the corresponding second layer interior portion are, however, not connected to each other, i.e. the first layer interior portion 18 and the second layer interior portion are unconnected. This allows for

independent adjustment of the tension in the first layer 12 and the second layer 21.

The sail 10 further comprises a cap unit 30 which is designed to cover the gap between the first layer leading edge 13 and the corresponding second layer leading edge 22, i.e. the cap unit 30 extends backwards some distance from the leading edges 13, 22 of the first and second layer respectively. The cap unit comprises two trailing edges 32, one trailing edge 32 positioned adjacent to the first layer 12 and one trailing edge 32 positioned adjacent to the second layer 21. The cap unit 30 further comprises a leading edge 31 which is will also be the leading edge of the sail 10 as a whole when the sail is part of the rig on the sailboat.

The sail 10 is further provided with at least one, but preferably a plurality of connecting elements 55 having a first end 56 and a second end 57. The second end 57 of the connecting elements 55 extends through the cap unit 30 and into the interior of the sail 10, while the first end 56 of the connecting elements 55 are positioned inside the cap unit 30. The connecting elements 55 are preferably secured to the cap unit 30 by suitable securing means, but may also be secured to other suitable parts of the sail 10 such as a wire or a similar element inside the sail running parallel to the leading edge 31 of the cap unit 30.

The connecting elements 55 may, as shown on the figures, be placed such that the first ends 56 of the connecting elements 55 are located within the interior of the sail 10 and the second ends 57 of the connecting elements 55 are located outside the sail 10. Alternatively, the connecting elements 55 may be entirely located within the interior of the sail 10. This may be suitable for example if the sail 10 is attached to the rig of a sailboat at three or more corners of the sail 10.

The first ends 56 of the connecting elements 55 may be provided with external connecting elements 59. The external connecting element 59 are preferably adapted for connection to corresponding connecting means on the rig of a sailboat, for example on the mast of the sailboat. Such connecting means are standard on sailboats and will not be described any further here.

The second end 57 of the connecting elements 55 are preferably provided with internal connecting elements 58 which may be various types of connecting means as will be further explained below. The internal connecting elements 58 are adapted for connection of various tensioning means which are used to independently adjust the tension in different parts of the sail 10 such as the first layer 12, the second layer 21 , the cap unit 30 and other parts of the sail 10 as will be explained in more detail below. Independently adjusting the tension in the different parts of the sail 10 means that the cross-sectional shape, as seen in a horizontal cross-section through the sail 10 when the sail is placed in a substantially vertical position, can be changed to adapt to varying sailing conditions, and as opposed to known sails, the adjustments of the various parts of the sail 10 can be done continuously during sailing in order to make sure that the sail 10 at all times has an optimal cross- sectional shape. In figure 1 , the internal connecting element 58 is one or more ring elements 63 or similar elements through which a line, rope, cord or similar elements can pass. In figure 1 it is further shown a main cord 61 which is divided into a number of connecting cords 62, one connecting cord 62 at each connecting element 55, which runs through the ring elements 63 and is attached to corresponding first layer connection elements 19. When the main cord is pulled at the bottom of the sail 10, for example by a manual or motorized winch or by a person, the tension in the main cord 61 and the connecting cords 62 are increased. The tension in the first layer 12 is consequently also increased and the shape of the first layer is adjusted to have a flatter shape. When the shape of the first layer 12 is adjusted, the cross-sectional shape of the sail 10 will also change and as a result the propulsive force on the sail 10 and the sailboat caused by the wind also changes. When separate cord elements 61 , 62 are provided for the various parts of the sail 10, such as the first layer 12, the second layer 21, the cap unit 30 and other parts as will be explained below, all said various parts of the sail 10 may be adjusted independently during sailing. It should also be noted that all the adjustment elements are located within the interior of the sail 10.

In figure 2 a variant of the sail in figure 1 is shown where the main cord 61 and the connecting cords 62 have been replaced by actuator means 64. The actuator means 64 are secured to respective first ends 56 of the connecting elements 55. A connecting member 65, for example a cord, a rope or a similar suitable element, is attached to a corresponding first layer connection element 19 on the first layer 12 and one of the actuator means 64 and each of the actuator means 64 is adapted to pull in the connecting member 65 or to let out the connecting member 65 so as to increase or decrease the tension in the first layer 12. The actuator means may comprise a pump, a winch, a piston/cylinder assembly or any other suitable mechanical means which can pull in and let out the connecting member 65. A plurality of actuator means 64 may be secured to each connecting element 55 so that the tension in the first layer 12, the second layer 21, the cap unit 30 and other parts of the sail 10 can be adjusted independently.

In figure 3 a slightly different version of the sail 10 is shown wherein a main cord 61 is arranged in a zigzag way between connecting elements 55 and first layer connection elements 19 from the topmost connecting element 55 of the sail to the lower edge of the sail where the main cord 61 may be attached to a manual or motorized winch which is capable of pulling in and letting out the main cord 61 and thereby adjusting the tension in the first layer 12. If it is feasible, the main cord 61 may also be pulled by a person, for example if a number of main cords 61 are used where each main cord 61 is connected to connecting elements 55 and first layer connecting elements 19 in a zigzag way as shown on the figures along a portion of the sail only. Together, the plurality of main cords 61 is capable of adjusting the first layer 12 along the entire vertical height of the sail 10 and may be handled by a person or by a mechanical or motorized winch to adjust the tension in the first layer 12. The same system of main cords 61 , each adjusting a portion of the vertical height of the sail 10, may be employed for all adjustable parts of the sail, such as the first layer 12, the second layer 21, the cap unit 30 and other parts as will be explained below.

Apart from the methods and means for adjusting the tension in the first layer 12, the second layer 21, the cap unit 30 and other adjustable parts of the sail as will be explained below, the other features of sail 10 illustrated in figures 1-3 and described in connection with figure 1 are the same and no further description of figures 2 and 3 will be included here.

Figure 4 schematically illustrates a typical horizontal cross-section through a sail 10 arranged in a substantially vertical position and without any of the tensioning means that might be included in the sail 10 to enable adjustment of the tension and shape of the first layer 12, the second layer 21, the cap unit 30 and other elements which will now be explained.

The first layer 12 and the second layer 21 are attached to each other along a first layer edge portion 17 (see figure 1) of the first layer trailing edge 14 and a second layer edge portion 26 (see figure 1) of the second layer trailing edge 23, for example by gluing, welding, stitching or any other suitable fastening method. Along the first layer leading edge 13 there is arranged at least one, but preferably a plurality of first layer connection elements 19 and along the second layer leading edge 22 there is arranged at least one, but preferably a plurality of second layer connection elements 28.

The first layer 12 and the second layer 21 may optionally be provided with at least one, but preferably a plurality of first layer shaping element 37 and second layer shaping elements 43 which can be arranged in first layer pockets 40 and second layer pockets 46 respectively. The first layer shaping element 37 and the second layer shaping elements 43 may also be fastened to the first layer 12 and the second layer 21 respectively by one or more straps, a combination of one or more pockets and straps or any other suitable fastening means. The first layer shaping elements 37 and the second layer shaping elements 43 are suitably made of an elastic material which allows the first layer shaping elements 37 and the second layer shaping elements 43 to bend out when they are subjected to axial tension. To obtain the desired shape of the first and second layer shaping elements 37, 43 when they are subjected to an axial load, the first and second layer shaping elements 37, 43 may be designed with a variable diameter along their axial lengths and/or a variable cross-sectional shape, i.e. a partly circular and a partly elliptic cross-section, such that one part of the first and second layer shaping elements 37, 43 bends out more than the remaining part of the first and second layer shaping elements 37, 43 when they are subjected to an axial load.

Each first layer shaping element 37 and second layer shaping element 43 extends backwards in a generally horizontal direction from the first layer leading edge 13 or near the first layer leading edge 13 and the second layer leading edge 22 or near the second layer leading edge 22 respectively. The length of the first layer shaping elements 37 and second layer shaping elements 43 is determined on basis of how much shaping capability it is desired that the first layer shaping elements 37 and second layer shaping elements 43 will have. Normally the first layer shaping elements 37 and second layer shaping elements 43 are included in the sail 10 to enable increased adjustment possibilities for the angle of attack of the sail, and the length of the first and second layer shaping elements should then be chosen so that such an adjustment is achievable. The first layer shaping elements 37 and the second layer shaping elements 43 may further have different lengths depending on the vertical position in the sail 10. The first layer shaping elements 37 and the second layer shaping elements 43 may for example have a gradually decreasing length from a lower part of the sail 10 towards the top of the sail in those cases where the sail has a triangular shape. The cap unit 30 covers the opening between the first layer leading edge 13 and the second layer leading edge 22 as explained in connection with figures 1-3 above. The connecting elements 55 pass through and are attached to the cap unit leading edge 31. The connecting elements 55 comprise internal connecting element 58 for various tension elements for adjustments of the tension and shape of the various parts of the sail 10. The connecting elements 55 also comprise an external connecting element 59 for connecting the sail to standard connecting means on a sailboat. As mentioned above, the entire connecting element may for certain sails 10 be located entirely within the interior of the sail 10, i.e. within the space bounded by the first layer 12, the second layer 21 and the cap unit 30 of the sail 10. The cap unit 30 may optionally be provided with at least one, but preferably a plurality of cap unit shaping element 49 with a first end 50 and a second end 51 which can be arranged in cap unit pockets 52. The first end 50 of the cap unit shaping elements are preferably secured to a connecting element 55 or a similar element within the sail 10 capable of taking up axial tension applied to a cap unit shaping element 49. The cap unit shaping element 49 may also be fastened to the cap unit 30 by one or more straps, a combination of one or more pockets and straps or any other suitable fastening means. Normally, a reason to include the cap unit shaping elements 49 in the cap unit 30 is to enable adjustment of the horizontal cross-sectional shape of the cap unit 30 and thereby increase the adjustment possibilities for the angle of attack of the sail 10. The cap unit shaping elements 49 are suitably made of an elastic material which allows the cap unit shaping elements to bend out when the cap unit shaping elements 49 are subjected to axial tension. To obtain the desired shape of the cap unit shaping elements 49 when they are subjected to an axial load, the cap unit shaping elements 49 may be designed with a variable diameter along their axial lengths and/or a variable cross-sectional shape, i.e. a partly circular and a partly elliptic cross-section, such that one part of the cap unit shaping elements 49 bends out more than the remaining part of the cap unit shaping elements 49 when they are subjected to an axial load.

Each cap unit shaping element 49 is arranged in a horizontal position and extends from the cap unit leading edge 31 or near the cap unit leading edge 31 towards the trailing edges 32 of the cap unit which lies adjacent to the first layer 12 and the second layer 21 respectively. The cap unit shaping elements 49 preferably extend to the trailing edges 32 or at least close to the trailing edges 32 of the cap unit 30 in order to avoid loose material at the end of the cap unit 30 causing unwanted turbulence during sailing in the transition zone between the cap unit 30 and the first layer 12 and the second layer 21 respectively. Alternatively the trailing edges 32 of the cap unit may be provided with a stiff material which is capable of preventing that the trailing edges 32 of the cap unit 30 flutter during sailing and cause turbulence. In figure 5 a number of possible ways of adjusting the shape and/or tension of the first layer 12, the second layer 21 and the cap unit 30, including the first layer, second layer and cap unit shaping elements 37, 43, 49 which may be included in the sail to increase the adjustability of the horizontal, cross-sectional shape of the sail 10 such that the lift force, i.e. the propulsive force on the sail, caused by the wind, can be continuously adjusted during sailing.

The sail 10 can be provided with one or more tension elements 67 which are connected to respective first layer connection elements 19 and connecting elements 55 for adjustment of the tension and shape of the first layer 12. During sailing, the wind pressure on the first layer 12 will cause it to have a curved shape. When tension in the tension elements 67 is increased, the tension in the first layer is also increased and the first layer 12 will get a shape with less curvature. Applying sufficient tension in the tension elements 67 will cause the first layer 12 to be flat or nearly flat. Hence, by adjusting the tension in the tension elements 67, the horizontal cross-sectional shape of the sail 10 and thereby the lift force on the sail 10 caused by the wind during sailing can be adjusted to a desired level.

The sail 10 may further be provided with one or more tension elements 68 which are connected to respective second layer connection elements 28 and connecting elements 55 in order to enable adjustment of the tension in and shape of the second layer 21. As with the first layer 12, the wind pressure on the second layer 21 during sailing will cause the second layer to have a curved shape. When tension in the tension elements 68 is increased, the tension in the second layer 21 is increased and the second layer 21 will get a shape with less curvature. Applying sufficient tension in the tension elements 68 will cause the first layer 12 to be flat or nearly flat.

Hence, by adjusting the tension in the tension elements 68, the horizontal cross- sectional shape of the sail 10 and thereby the lift force on the sail 10 caused by the wind during sailing can be adjusted to a desired level.

Clearly, the sail 10 will usually be provided with both tensioning elements 67 and

68 in order to independently adjust the first layer 12 and the second layer 21 of the sail in order to obtain the optimal airfoil shape of the sail at any given time during sailing. The two tension elements 67 and 68 are thus the most basic tension elements for adjustment of the horizontal cross-sectional shape of the sail 10, and hence the lift forces on the sail during sailing, and they are further described in connection with figures 6 and 7 below. The cap unit 30 is usually provided with a plurality of cap unit shaping elements 49 as is also indicated in figure 5. In order to adjust the axial tension in the cap unit shaping elements 49, the sail is further provided with tension elements 73 which extend between the connection elements 55 and the cap unit 30 on respectively the side of the first layer 12, where tension elements 73 may be attached to the cap unit 30, and the second layer 21, where the tension elements 73 are attached to the cap unit 30. The tension elements 73 are preferably attached to the cap unit pockets 52 or directly to the cap unit shaping elements 49. When tension in the tension elements 73 is increased, the axial load or tension in the cap unit shaping elements 49 is also increased and the cap unit shaping elements 49 bend outwards and provide the cap unit 30 with a shape which is adjustable. Hence, adjusting the tension in the tension elements 73 will adjust the angle of attack on the sail 10. It should be noted that in figure 5 the tension in the tension elements 73 on both sides of the cap unit 30 has been increased to an extent where the cap unit 30 has the shape of more or less a drop. This is usually not a preferred shape of the cap unit 30 with regard to sailing and the tension in the tension elements 73 are preferably adjusted so that a more airfoil-like shape of the cap unit 30 and the sail 10 is obtained, i.e. more tension in the tension elements 73 on one sideof the sail than the other.

The first layer 12 of the sail 10 may be provided with at least one, but preferably a plurality of first layer shaping elements 37. In order to adjust the tension in the first layer shaping element 37, the sail can further be provided with tension elements 69 which extend between respective connection elements 55 and the first layer 12 where the tension elements 69 preferably are attached to the first layer pockets 40 or directly to the first layer shaping elements 37. When tension in the tension elements 69 is increased, the axial load or tension in the first layer shaping elements 37 is also increased causing the first layer shaping elements 37 to bend outwards and provide the first layer 12 with a curved shape in the portion of the sail that the first layer shaping elements 37 cover. Adjusting the tension in the tension elements

69 is particularly helpful for adjustment of the angle of attack of the sail 10. The second layer 21 of the sail 10 may also be provided with at least one, but preferably a plurality of second layer shaping elements 43. In order to adjust the tension in the second layer shaping element 43, the sail can further be provided with tension elements 70 which extend between respective connection elements 55 and the second layer 21 where the tension elements 70 preferably are attached to the second layer pockets 46 or directly to the second layer shaping elements 43. When tension in the tension elements 70 is increased, the axial load or tension in the second layer shaping elements 43 is also increased causing the second layer shaping elements 43 to bend outwards and provide the second layer 21 with a curved shape in the portion of the sail that the second layer shaping elements 43 cover. Adjusting the tension in the tension elements 70 is particularly helpful for adjustment of the angle of attack of the sail 10.

The sail 10 may further be provided with one or more tension elements 71 which extend between respective first layer connection elements 19 and a cap unit connection element 35 on the cap unit 30. When tension is increased in the tension element 71 the result can be that the cap unit 30 is pulled closer to the first layer 12 and/or that the shape of the cap unit 30 is adjusted depending on where the cap unit connection element 35 is fastened on the cap unit 30. Preferably there is no gap between the first layer 12 and the cap unit 30 in order to avoid formation of turbulence as air passes over the transition zone between the cap unit 30 and the first layer 12 and during sailing the tension in the tension element 71 may therefore be increased until no such gap is achieved.

Similarly the sail 10 may be provided with one or more tension elements 72 which extend between respective second layer connection elements 28 and a cap unit connection element 35 on the cap unit 30. When tension is increased in the tension element 72 the result can be that the cap unit 30 is pulled closer to the second layer 21 and/or that the shape of the cap unit 30 is adjusted depending on where the cap unit connection element 35 is fastened on the cap unit 30. Preferably there is no gap between the second layer 21 and the cap unit 30 in order to avoid formation of turbulence as air passes over the transition zone between the cap unit 30 and the second layer 21 and during sailing the tension in the tension element 72 may therefore be increased until no such gap is achieved.

The figures 6-7 schematically illustrate in greater detail certain aspects of the sail 10 and some variations that can be made to the sail 10. In figures 6 and 7 a sail 10 is shown, without a cap unit 30, comprising a first layer 12 and a second layer 21 which are connected along their corresponding trailing edge portions in the same way as explained above. A least one, but preferably a plurality of tension elements in form of a plurality of first layer adjustment elements 67 which are attached to respective first layer connection elements 19 along the leading edge 13 of the first layer 12 and extend to the internal connecting element 58 on connecting elements 55 as described above. Each of the first layer adjustment elements 67 may be a cord, a rope or any other suitable element as shown in figures 1 and 3, which pass through the internal connecting element 58 and continues down to lower part of the sail 10 where the cord or rope 67 is connected to a hand operated or motorized winch which can be used to adjust the tension in the first layer adjustment element 67.

The sail 10 further comprises at least one, but preferably a plurality of tension elements in form of a plurality of second layer adjustment elements 68 which are attached to respective second layer connection elements 28 along the leading edge 22 of the second layer 21 and extend to the internal connecting element 58 on connecting elements 55 as described above. Each of the second layer adjustment elements 68 may be a cord, a rope or any other suitable element as shown in figures 1 and 3, which pass through the internal connecting element 58 and continues down to lower part of the sail 10 where the cord or rope 68 is connected to a hand operated or motorized winch which can be used to adjust the tension in the second layer adjustment element 68.

Alternatively, the first layer adjustment elements 67 and/or the second adjustment elements 68 may comprise one or more actuator means 64 such as a pump as shown in figure 2, which are attached to the connecting elements 55 and connected to the first layer 12 and the second layer 21 with respective ropes, cords or any other suitable elements. The pumps must be capable of increasing and decreasing the tension in the cords and thereby adjusting the tension in the first layer 12 and/or the second layer 21. In figure 6 the sail 10 is shown with wind W blowing towards the leading edges of the first layer 12 and the second layer 21 of the sail 10. The wind pressure causes the first layer 12 and the second layer to curve as indicated in figure 6. In figure 7 the tension in the first layer adjustment elements 67, and thereby the first layer 12, has been increased such that the first layer 12 is substantially flat while the tension in the second layer adjustment elements 68 remain the same, i.e. there is no change in the tension in the second layer 21. The result of the independent adjustment of the first layer and the second layer is that the horizontal cross-sectional shape of the sail 10 has changed in a way that will cause an increased lift force on the sail 10. As the sailboat is tacking during sailing, the tension in the first layer 12 and the tension in the second layer 21 can be adjusted independently so that the sail at all times has the optimal airfoil shape that provides the greatest possible lift force on the sail or any airfoil shape that provides a lift force smaller than the maximum possible lift force if that is desired. The important thing about the present sail 10 is that the two layers 12, 21 of the sail 10 are independently adjustable during sailing and that the cross-sectional shape of the sail therefore can be adjusted during sailing. In figure 8 a sail 10 is shown comprising a first layer 12, a second layer 21, a cap unit 30, connecting elements 55 and cap unit shaping elements 49 as explained several times above, where the cap unit shaping elements 49 are attached to respective connecting elements 55. The sail 10 is provided with a number of tension elements as will be explained briefly below. There is provided tension elements in form of at least one, but preferably a plurality of first layer adjustment elements 67 for adjustment of the tension in the first layer 12 and at least one, but preferably a plurality of second layer adjustment elements 68 for adjustment of the tension in the second layer 21 as shown figures 6-7 and explained in detail above. The sail 10 shown in figure 8 is also provided with tension elements in form of at least one, but preferably a plurality of cap unit adjustment elements 73 which are attached to the cap unit 30, for example to the cap unit pockets 52 or directly to the cap unit shaping elements 49 as explained above, and extend to respective internal connecting elements 58 of the connecting elements 55. Each cap unit adjustment element 73 may comprise a rope, a cord or a similar element, which passes through the internal connecting elements 58, which may be a ring or any other suitable element adapted for support of one or more ropes passing and sliding through it, and extends down to the bottom of the sail where the rope may be connected to a manually operated or motorized winch for adjustment of the tension in the rope and thereby increasing or decreasing the axial tension in the cap unit shaping elements 49. The cap unit adjustment elements 73 may also comprise a pump, a

piston/cylinder arrangement or any other suitable mechanical device that is capable of increasing and decreasing the tension in the cap unit adjustment elements 73. Adjusting the axial tension in the cap unit shaping elements 49 will result in an adjustment of the cross-sectional shape of the cap unit 30 and thereby the angle of attack of the sail 10. In figure 8, the cap unit adjustment elements 73 on the left side of the sail, i.e. the part of the cap unit 30 that lies next to the first layer 12, has increased tension such that the cap unit shaping elements 49 bends out while the cap unit adjustment elements 73 on the other side of the sail, i.e. the part of the cap unit 30 that lies next to the second layer 21, have no or very little tension applied to them and the cap unit shaping elements 49 on this side are therefore substantially straight. The result is cap unit 30 with a shape that helps the sail 10 form an airfoil shape.

The sail 10 shown in figure 8 is further provided with tension elements in the form of at least one, but preferably a plurality of first adjustment elements 71 and at least one, but preferably a plurality of second adjustment elements 72.

The first adjustment elements 71 extend between cap unit connection elements 35 and first layer connection elements 19. Each of the first adjustment elements 71 may comprise a rope, a cord or a similar element, which extends down to the bottom of the sail where the rope may be connected to a manually operated or motorized winch for adjustment of the tension in the rope and thereby increasing or decreasing the tension in the first adjustment element 71. The rope may be passed through either the cap unit connection elements 35 or the first layer connection elements 19 which may be formed with a ring element or any other suitable element adapted for support of one or more ropes passing and sliding through it. The first adjustment elements 71 may also comprise a pump, a piston/cylinder arrangement or any other suitable mechanical device that is capable of increasing and decreasing the tension in the first adjustment elements 71.

The second adjustment elements 72 extend between cap unit connection elements 35 and second layer connection elements 28. Each of the second adjustment elements 72 may comprise a rope, a cord or a similar element, which extends down to the bottom of the sail where the rope may be connected to a manually operated or motorized winch for adjustment of the tension in the rope and thereby increasing or decreasing the tension in the second adjustment element 72. The rope may be passed through either the cap unit connection elements 35 or the second layer connection elements 28 which may be formed with a ring element or any other suitable element adapted for support of one or more ropes passing and sliding through it. The second adjustment elements 72 may also comprise a pump, a piston/cylinder arrangement or any other suitable mechanical device that is capable of increasing and decreasing the tension in the second adjustment elements 72.

When the tension in the first adjustment elements 71 and/or the second adjustment elements 72 is increased the cap unit 30 is pulled towards the first layer 12 and/or the second layer 21 respectively so as to reduce the gap between the cap unit 30 and the first layer 12 and the second layer 21 in order to minimize the formation of turbulent air flow in the transition zone between the cap unit 30 and the first layer 12 and the second layer 21 during sailing.

In figure 9 there is shown a sail 10 which is very similar to the sail 10 shown in figure 8. The difference is that one of the tension elements, the first adjustment elements 71, are slidingly connected to the cap unit 30 as indicated on figure 9. The cap unit connection element 35 shown in figure 8 has been exchanged with a sliding connection 78 comprising a guide element 79 which is attached to the cap unit 30, and a sliding element 80 to which the first adjustment elements 71 are connected. When the tension in the first adjustment elements 71 is increased the sliding element 80 is allowed to slide along the guide element 79 and thereby automatically find its position along the guide element 79 which best balances the forces acting on the sliding connection 78. It should be noted that although only one sliding connection between a tension element, i.e. the first adjustment elements 71, and a part of the sail 10, i.e. the cap unit 30, is shown in figure 9, it should be understood that any connection between a tension element and a part of the sail 10 can be in the form of a sliding connection 78 as indicated in figure 9. The other features of the sail 10 shown in figure 9 are the same as already described above and will therefore not be repeated here.

In figure 10 there is shown a sail 10 which is very similar to the sails 10 shown in figures 8 and 9. The difference is that in figure 10, the sail is provided with at least one, but preferably a plurality of tension elements in form of secondary adjustment elements 75 as shown. The sail 10 in figure 10 is provided with tension elements in the form of cap unit adjustment elements 73 in the same way as described above. The secondary adjustment elements 75 extend between cap unit connection elements 35 and secondary connections 76 on the cap unit adjustment elements 73. Each of the secondary adjustment elements 75 may comprise a rope, a cord or a similar element, which extends down to the bottom of the sail where the rope may be connected to a manually operated or motorized winch for adjustment of the tension in the rope and thereby increasing or decreasing the tension in the secondary adjustment element 75. The rope may be passed through either the cap unit connection elements 35 or the secondary connections 76 which may be formed with a ring element or any other suitable element adapted for support of one or more ropes passing and sliding through it. The secondary adjustment elements 75 may also comprise a pump, a piston/cylinder arrangement or any other suitable mechanical device that is capable of increasing and decreasing the tension in the secondary adjustment elements 75.

The secondary connections 76 may be attached to the cap unit adjustment elements 73 in a fixed position. Alternatively the secondary connections 76 can be designed so that they can slide along the cap unit adjustment elements 73, for example by using a ring-shaped element which encircle the cap unit adjustment elements 73 and is capable of sliding along the cap unit adjustment elements 73. A sliding connection 78 as shown in figure 9 could also be used in some instances as long as the cap unit adjustment elements 73 is suitable for attachment of a guide element 79. The result is that the secondary connections 76 position themselves in the most favourable position along the cap unit adjustment elements 73 in relation to the forces acting on the secondary connection 76 and the position of the cap unit adjustment elements 73.

Although not shown in the figures, it should be noted that a plurality of secondary adjustment elements 75 may be employed which are extensions between the cap unit 30 and each cap unit adjustment element 73, where the secondary adjustment elements 75 may be slidingly or fixedly attached to the cap unit adjustment elements 73.

It should also be noted that secondary adjustment elements 75 may be arranged between any tension element of the sail 10 such as the at least one first layer adjustment element 67, the at least one second layer adjustment element 68, the at least one first layer shaping element adjustment element 69, the at least one second layer shaping element adjustment element 70, the at least one cap unit adjustment element 73, the at least one first adjustment element 71, the at least one second adjustment element 72, and a part of the sail 10 such as the first layer 12, the second layer 21, the cap unit 30 or the connecting element 55. Any attachment points of the various tension elements may be fixedly or slidingly attached to the parts of the sail or other tension elements that they are attached to.

In figure 11 an embodiment of the sail is shown comprising at least one, but preferably a plurality of sail shaping elements 83 which extend through most of the sail 10 in a horizontal direction. The sail shaping elements 83 are suitably made of an elastic material which allows the sail shaping elements 83 to bend out when the sail shaping elements 83 are subjected to axial tension. To obtain the desired shape of sail shaping elements 83 when they are subjected to an axial load, sail shaping elements 83 may be designed with a variable diameter along their axial lengths and/or a variable cross-sectional shape, i.e. a partly circular and a partly elliptic cross-section, such that one part of the sail shaping elements 83 bends out more than the remaining part of sail shaping elements 83 when they are subjected to an axial load.

When the sail 10 has a generally triangular shape, which is a common shape of a sail, the length of the sail shaping elements 83 will vary according to each individual sail shaping element' s vertical position in the sail 10. The sail shaping elements 83 may be connected to connecting elements 55 as in the foremost part of the sail 10 shown in figure 11. At the rear of the sail 10 the sail shaping elements 83 may be arranged in pockets arranged at or near the trailing edge of the sail 10 as indicated in figure 1 1, for example between the first layer trailing edge 14 and the second layer trailing edge 23. The sail 10 is also provided with tension elements in the form of sail shaping element adjustment elements 74 which preferably is attached to the pockets at the trailing edge of the sail mention above and extend to the connecting elements 55. Each of the sail shaping element adjustment elements 74 may comprise a rope, a cord or a similar element, which extends from the connecting elements 55 down to the bottom of the sail where the rope may be connected to a manually operated or motorized winch for adjustment of the tension in the rope and thereby increasing or decreasing the axial tension in the sail shaping element adjustment elements 74. The rope may be passed through the connecting elements 55 comprising an internal connecting element 58 which may be formed with a ring element or any other suitable element adapted for support of one or more ropes passing and sliding through it. The sail shaping element adjustment elements 74 may also comprise a pump, a piston/cylinder arrangement or any other suitable mechanical device that is capable of increasing and decreasing the tension in the sail shaping element adjustment elements 74.

The sail illustrated in figure 11 is also shown with first layer shaping elements 37 and second layer shaping elements 43 arranged in respective first layer pockets 40 and second layer pockets 46 as described above.

First layer shaping element adjustment elements 69 extend between the rear end of the first layer pockets 40 and the connecting elements 55. Each of the first layer shaping element adjustment elements 69 may comprise a rope, a cord or a similar element, which further extends from the connecting elements 55 down to the bottom of the sail where the rope may be connected to a manually operated or motorized winch for adjustment of the tension in the rope and thereby increasing or decreasing the axial tension in the first layer shaping element adjustment elements 69. The rope may be passed through the connecting elements 55 comprising an internal connecting element 58 which may be formed with a ring element or any other suitable element adapted for support of one or more ropes passing and sliding through it. The first layer shaping element adjustment elements 69 may also comprise a pump, a piston/cylinder arrangement or any other suitable mechanical device that is capable of increasing and decreasing the tension in the first layer shaping element adjustment elements 69. Second layer shaping element adjustment elements 70 extend between the rear end of the second layer pockets 46 and the connecting elements 55. Each of the second layer shaping element adjustment elements 70 may comprise a rope, a cord or a similar element, which further extends from the connecting elements 55 down to the bottom of the sail where the rope may be connected to a manually operated or motorized winch for adjustment of the tension in the rope and thereby increasing or decreasing the axial tension in the second layer shaping element adjustment elements 70. The rope may be passed through the connecting elements 55 comprising an internal connecting element 58 which may be formed with a ring element or any other suitable element adapted for support of one or more ropes passing and sliding through it. The second layer shaping element adjustment elements 70 may also comprise a pump, a piston/cylinder arrangement or any other suitable mechanical device that is capable of increasing and decreasing the tension in the second layer shaping element adjustment elements 70.

In addition, the sail 10 in figure 11 is shown with further tension elements in the form of first layer adjustment elements 67 for adjustment of the tension in the first layer 12 and second layer adjustment elements 70 for adjustment of the tension in the second layer 21. These have been explained in detail above and will not be explained again here. Furthermore, as seen on figure 11 , the sail 10 is provided with cap unit shaping elements 49. The cap unit adjustment elements 49 for adjustment of the axial tension, and thereby the shape of the cap unit shaping elements 49, are, however, not shown in figure 1 1 due to lack of space on the drawing. The cap unit adjustment elements 49 will, however, be present in the same way as explained above. On figure 11 all there is no tension applied to any of the tension elements 67, 68, 69, 70, 74 or in the tension elements 73 (not shown in figure 11) adjusting the tension in the cap unit shaping elements 49, and the first layer shaping element 37, the second layer shaping element 43, the cap unit shaping elements 49 and the sail shaping elements 83 are therefore substantially straight. During sailing the tension in the sail shaping element adjustment elements 74 may be increased so that the axial tension in the sail shaping elements 83 is increased and the sail shaping elements 83 bends out to a desired degree. The sail shaping elements 83 can, with help from the wind pressure, easily be made to bend out towards the first layer 12 or the second layer 21 as desired and thereby help to give the sail 10 a desired cross- sectional shape.

The embodiment of the present sail with sail shaping elements 83 will also work with a sail having only one layer instead of having both first and second layers. The sail shaping elements 83 are arranged substantially between the leading edge and the trailing edge of the sail as indicated in figure 11, but as opposed to the embodiment in figure 11, where the sail shaping elements 83 are unconnected and free from the first and second layers 12, 21 between the attachment points at the front and the rear of the sail shaping elements 83, the sail shaping elements of the embodiment with only one layer must be attached, for example with straps, to the single layer of the sail at least at few points along the length of the sail shaping elements so that the single layer is forced to follow the shape of the sail shaping elements as they are forced to bend one way or the other.

To briefly summarize the sail 10 according to the present invention and as described above, the sail may be provided with a number of different parts including the first layer 12, the first layer shaping elements 37, the second layer 21 , the second layer shaping elements 43, the cap unit 30, the cap unit shaping elements 49, the connecting elements 55 and possibly sail shaping elements 83. The tension and shape of these parts of the sail 10 may be adjusted independently by employing various tension elements including the first layer adjustment elements 67, the second layer adjustment elements 68, the first layer shaping element adjustment elements 69, the second layer shaping element adjustment elements 70, the cap unit adjustment elements 73, the first adjustment elements 71 , the second adjustment elements 72, the secondary adjustment elements 75 and possibly sail shaping element adjustment elements 74. Any given sail may include all these parts and all or some of the tension elements. Other sails may include some of the parts of the sail mentioned above and a selected combination of tension elements which will provide the sail with the desired flexibility in the adjustment of the tension and shape of the various parts of the sail.

Since all the tension elements preferably can be operated independently and therefore adjust the tension in the various parts of the sail 10 to which they are connected, independently, the cross-sectional shape of the sail 10 may be adjusted to any desired shape within the physical limits of the adjustment of said parts of the sail during sailing.

It should be noted that all tension elements may be attached to a part of the sail using a sliding connection so that tension element adjusts itself to a position giving the most favourable direction of the tension force applied to that part of the sail.