NZ719265B2 - Method for rigging and controlling a wing sail - Google Patents

Abstract

rigging for a wing propelled craft comprises a mast having a starboard side and a port side, wherein the mast is controllably rotatable in either direction about a longitudinal axis; a flexible sail comprising a starboard flexible sail portion and a substantially identical port flexible sail portion, each flexible sail portion having a luff and a leach, wherein the luff of each sail portion is connected to a respective side of the mast; and a plurality of elongated battens, each of which extends substantially between the luff and the leach of one of the respective sail portions, each of which is in contact with the respective flexible sail portion. Rotation of the mast causes the battens connected to one of the sail portions to be compressed along their length so as to bend one of the sail portions to increase the camber thereof and causes the battens connected of the other sail portions to be tensioned along their length so as to partly straighten the other sail portion which changes the shape of an aerofoil formed by the sail. on, each flexible sail portion having a luff and a leach, wherein the luff of each sail portion is connected to a respective side of the mast; and a plurality of elongated battens, each of which extends substantially between the luff and the leach of one of the respective sail portions, each of which is in contact with the respective flexible sail portion. Rotation of the mast causes the battens connected to one of the sail portions to be compressed along their length so as to bend one of the sail portions to increase the camber thereof and causes the battens connected of the other sail portions to be tensioned along their length so as to partly straighten the other sail portion which changes the shape of an aerofoil formed by the sail.

Description

Method for Rigging and Controlling a Wing Sail Field of the Invention The present invention relates to a wing sail for wind propelled craft.

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

In general sails used to propel craft are either vely thin, compared to their length, or comprise combinations of thick ric aerofoils, such as in AC72 class catamarans seen in the 2013 America’s Cup competition.

Sails or ils 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 on the windward side of the sail, along with the shape of the aerofoil section, s 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 d side relative to the windward side and hence an 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 d of the beam of the vessel.

While the thick symmetrical wing sails used on AC72 catamarans and other high performance sailing craft can provide good lift and drag characteristics. These wings are typically made from two or more symmetrical wing sections configured relative to one another to e camber. There is no ability to induce asymmetry into the individual wing sections. Thus, these wing sails have practical limitations. These wing sails are constructed to be light weight and rigid. They 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.

While reefable and stowable “soft” wing sails exist, they are generally quite complex and heavy.

A wing sail is described by Johnston, Patrick Murray (in patents AU1986052399 and US4,766,831, the contents of which are incorporated herein by reference). The wing sail comprises two substantially identical flexible sail portions each having a leach and a luff.

Elongated battens are in contact with the flexible sail portions. A control rod has the battens and luffs of the sail portions rotatably attached so that the perpendicular distance between the sail portions varies wherein angular displacement of the control rod with respect to the boom causes the battens to be ssed along their length so as to bend one of the sail ns to se the camber thereof and causes the battens of the other sail portions to be tensioned along their length so as to partly straighten the other sail portion which decrease the distance from each other at the luff, but increase the perpendicular distance between the sail portions away from the luff, resulting in asymmetry of the aerofoil. Notably the leaches of the sail ns are connected. Further the control rod is recessed in a concave shaped ng edge of a mast. A leading edge of the mast is semi-elliptical and namic, so as to have a wing mast profile.

It is noted that the term ’ is also spelt ‘leech’ by persons skilled in the art.

The present invention provides improvements over this prior wing sail. nce to any prior art is not an admission that they form part of the common general knowledge of a skilled person in any jurisdiction. In this specification the terms "comprising" or "comprises" are used inclusively and not exclusively or tively. y of the Invention According to an aspect of the t invention there is provided a rigging comprising: a mast having a starboard side and a port side, wherein the mast is controllably ble in either direction about a longitudinal axis; a flexible sail comprising a starboard flexible sail portion and a substantially identical port flexible sail portion, each flexible sail portion having a luff and a leach, wherein the luff of each sail portion is ted to a respective side of the mast; a plurality of elongated battens, each of which extends substantially n the luff and the leach of one of the tive sail portions, each of which is in contact with the respective flexible sail portion, and each of which is pivotally connected to a respective outermost part of the starboard or port side of the mast; wherein rotation of the mast causes the battens connected to one of the sail portions to be compressed along their length so as to bend one of the sail portions to increase the camber f and causes the battens ted on the other sail portions to be tensioned along their length so as to partly straighten the other sail portion which changes the shape of an aerofoil formed by the sail.

In an embodiment the mast comprises substantially flat portions at an angle to each other, each flat portion ending in a corner on one of the sides of the mast and at which the respective flexible sail portions are connected, wherein when the mast is rotated in one direction the surface of the flat portion on the side with the sail portion having the resulting increased camber and the surface of the that sail n have an air flow there-over that is relatively flat or oes a relatively small change in direction.

In an embodiment the surface of the flat portion on the side with the sail potion having the resulting increased camber and the e of the that sail portion have the air flow thereover that is most flat substantially before a maximum rotation of the mast in that direction.

In an embodiment an interface n the mast and the sail portion that is partly straightened has a rounded or non-sharp corner.

In an embodiment the interface comprises an acute angle, wherein the airflow passing the interface reattaches to the sail portion relatively close to the mast.

In an embodiment the mast is profiled so that when the mast is rotated in one direction airflow passing from the mast to the sail portion with the sed camber that remains relatively attached to the sail portion.

In an embodiment the mast is profiled so that when the mast is rotated in one ion airflow passing from the mast to the sail portion that is partly straightened reattaches to the sail portion relatively close to the mast.

In an embodiment the attachment of the luff of at least one of the sail portions is such that there is no gap or only a small gap between the luff and the mast.

In an embodiment the small gap is such that it discourages airflow on the windward side through the gap.

In an embodiment the small gap is oned where it is most likely for there to be an airflow separation bubble on the windward side.

In an embodiment the angle between the flat ns is between 60 and 100 degrees, preferably between 70 and 95 degrees and most preferable about 90 s.

In an embodiment there is a convex curved portion n the flat portions.

In an embodiment the mast is symmetrical on its port and starboard sides.

In an embodiment the mast is rotatable to a maximum amount in either direction ing to the angle between the flat portions.

In an embodiment the degree of rotation of the mast controls the compression and tension in the battens.

In an embodiment the leaches are controllably moveable relative to each other such that one of the leaches is closer to the mast than the other according to a tack of the sail.

In an embodiment the nt of the leaches is controlled by controlling the separation allowed between leach ends of the battens.

In an embodiment movement of the leaches controls the mean camber of the aerofoil.

In an embodiment the rigging further comprises a boom pivotally coupled to the mast at one end and which at another end the sail ns are coupled at a clew.

In an embodiment the amount of separation between the leaches is varied according to the length along the leach from the clew.

In an embodiment the boom is l in a al plane, wherein an angle of the boom in the vertical plane is controllable and the angle of the boom in the vertical plane is configured to control the separation allowed between leach ends of the battens.

In an embodiment the boom is pivotal in a ntal plane between its end and rotation of the mast is adjusted relative to a longitudinal axis of the boom.

In an embodiment the boom is controllably articulated between its ends.

In an ment the mast is a spar and the sail is a headsail, wherein rotation of the spar is controlled relative to a deck of the boat on to which the rigging is installed.

In an embodiment the flat portion of the mast is formed by a mast pocket stretched between mast collars.

In an embodiment each sail portion is le along the length of the mast.

According to an aspect of the present ion there is provided a rigging comprising: a mast having a starboard side and a port side, wherein the mast is controllably ble in either direction about a longitudinal axis; a flexible sail comprising a starboard flexible sail portion and a substantially identical port flexible sail portion, each flexible sail portion having a luff and a leach, wherein the luff of each sail portion is connected to a respective side of the mast; a plurality of elongated battens, each of which extends substantially between the luff and the leach of one of the respective sail portions, each of which is in contact with the respective le sail portion; wherein the battens ted to one of the sail portions may be compressed along their length so as to bend one of the sail portions to increase the camber thereof and causes the battens connected of the other sail portions to be tensioned along their length so as to partly straighten the other sail portion which changes the shape of an aerofoil formed by the sail; wherein the leaches are controllably moveable relative to each other such that compression is applied to the one or more of the battens on a leeward side of the sail by tension in a ponding one or more of the battens on a windward side of the sail.

In an embodiment, the leaches are llably moveable relative to each other so as to determine the spacing between the leaches.

In an embodiment, the control of the movement of the leaches is according to the height of the respective s in the flexible sail.

According to an aspect of the present invention there is provided a rigging sing: a mast having a starboard side and a port side, wherein the mast is controllably rotatable in either ion about a longitudinal axis; a flexible sail comprising a starboard flexible sail portion and a substantially identical port flexible sail portion, each flexible sail portion having a luff and a leach, wherein the luff of each sail portion is ted to a respective outermost side of the mast; a plurality of ted battens, each of which extends substantially between the luff and the leach of one of the respective sail portions, each of which is in t with the respective flexible sail portion; wherein the battens connected to one of the sail portions may be compressed along their length so as to bend one of the sail portions to increase the camber thereof and causes the battens connected of the other sail portions to be tensioned along their length so as to partly straighten the other sail portion which changes the shape of an aerofoil formed by the sail; wherein leach end of battens are moveable relative to each other.

In an ment the relative displacement of each of the leach ends of the battens is controllable.

In an ment the relative displacement of the leach ends of the battens is automatically controlled by the angle of a boom to which the sail portions are attached.

In an embodiment the sail portions provide differing relative movement of corresponding portions of the leaches to each other, where the amount of relative movement is controlled according to the height of the leach portions from a deck of a boat on which the rigging is installed. ing to an aspect of the present invention there is ed a rigging comprising a mast pocket covering the mast and ted to sail portions forming either side of a wing sail, wherein the leading profile of the mast pocket is provided by a plurality mast collars for attachment of battens extending inside and in contact with the sail portions, such that the battens control the namic shape of the sail portions by increasing the camber of one of the sail portions according to a direction of rotation of the mast.

In an embodiment the mast collars profile the mast such that when the mast is rotated in one direction airflow passing from the mast to sail portion with the increased camber remains relatively attached to the sail n.

According to an aspect of the present invention there is a mast collar for coupling to a mast, the mast collar rotatable with the mast and connected to on each side to a sail portion, the sail portions forming either side of a wing sail, the mast collar being configured for pivotable attachment of battens extending inside and in contact with the sail ns, such that the battens control the aerodynamic shape of the sail portions by sing the camber of one of the sail portions according to a direction of rotation of the mast.

According to an aspect of the present invention there is provided a rigging comprising: a mast having a starboard side and a port side, wherein the mast is controllably ble in either direction about a udinal axis; a flexible sail comprising a starboard flexible sail portion and a substantially identical port flexible sail n, each le sail portion having a luff and a leach, wherein the luff of each sail portion is connected to a respective side of the mast; a plurality of elongated battens, each of which extends substantially between the luff and the leach of one of the respective sail portions, each of which is in contact with the respective le sail portion; a boom pivotally coupled to the mast at one end and which at r end the sail portions are coupled at a clew, wherein the boom is controllably articulated between its ends; n articulation of the boom causes the mast to rotate and then causes the battens connected to one of the sail portions to be compressed along their length so as to bend one of the sail portions to increase the camber thereof and causes the battens connected of the other sail portions to be tensioned along their length so as to partly straighten the other sail portion which changes the shape of an aerofoil formed by the sail.

According to an aspect of the invention there is a spreader between ends of the mast that is rotatable about an axis of rotation of the mast, such that the spreader is substantially stationary relative to the deck of the boat.

According to an aspect of the invention there is provide a wind led craft comprising the rigging described above.

In this specification the terms ising” or “comprises’’ are used inclusively and not exclusively or exhaustively.

Any references to documents that are made in this specification are not intended to be an admission that the information contained in those documents form part of the common general dge known to a person skilled in the field of the invention, unless explicitly stated as such.

Description of Drawings In order to provide a better understanding of the present invention embodiments will now be described may be described, by way of example only, with reference to the drawings, in which:- Figure 1 is a side elevation of a sailing vessel having rigging according to an example embodiment of the present invention; Figure 2 is a side view of the rigging of Figure 1, including a wing sail; Figure 3 is a section view of the wing sail rotated to give a port tack setting; Figure 4 is a ntal sectional view of a mast with port and starboard batten slide assemblies; Figure 5 is a screen capture from Xfoil CFD software showing performance of a wing sail according to an embodiment of the present invention; Figure 6 is an enlargement of the screen e of Figure 5; Figure 7 is an enlargement of the screen capture of Figure 6; Figure 8 is a screen capture from Xfoil CFD software showing performance of a wing sail according to an embodiment of the present invention; Figure 9 is an oblique view of the mast of Figure 4, with a port side batten assembly in exploded view; Figure 10A is an partial oblique view of a luff n of a port wing sale portion with a cut out in the luff tape of the sail portion and luff rope with a sail slide fitted to the luff rope according to an embodiment of the t invention; Figure 10B is a partial oblique view of the luff portion of Figure 12 with a luff end batten receptacle fitted; Figure 11 is a l horizontal cross section of the mast of Figure 4, with an alternative ment structure of the port sail portion; Figure 12 is an oblique view of a mast collar according to an embodiment of the t invention; Figure 13 is an oblique view of an assembly of the mast, mast key, mast collar of Figure 12 and batten ends ing to an ment of the present invention; Figure 14 is an e view of a batten end fitting which fit into the collar of Figure 13, with a cord attaching the sail portion to the batten fitting; Figure 15A is a side profile of a mast fitted with a collar according to an embodiment of the present invention; Figure 15B is a horizontal cross section of the mast and collar of Figure 15A; Figure 15C is an elevation of the a sail including the mast and collars of Figures 15A and 15B according to an embodiment of the present invention; Figure 16 is a screen capture of a horizontal cross section of a sail according to the present invention with the mast rotated to 30 degrees by (say) 15 degrees of rotation and 15 degrees of sail twist; Figure 17 is a screen capture of a horizontal cross section of a sail according to the t invention with the mast d to 30 degrees but the leaches allowed to slip 1.7% of the chord length; Figure 18 is a screen capture of a horizontal cross section of a sail according to the present invention with the mast rotated to 15 degrees with no slip at the leach; Figure 19 is an oblique view of battens of the sail of Figure 2; Figure 20A is a schematic diagram showing a leach control line running along the battens of Figure 19 in a port setting; Figure 20B is a schematic diagram showing a leach l line running along the battens of Figure 19 in a starboard setting; Figure 21 is an oblique view of battens of the sail of Figure 2, with an ative leach control ism; Figure 22 is a schematic diagram showing the leach control line of Figures 20A and 20B running along a batten pocket and through an end of the batten; Figure 23 is a schematic diagram showing the attachment of the leach control line to a luff control line on the uppermost controlled batten in the sail; Figure 24 is a schematic diagram showing attachment of the luff l line to the boom; Figure 25 is a schematic diagram showing attachment of le luff control lines to the boom; Figure 26 is a schematic partial side elevation showing an articulated boom attached to the mast according to an embodiment of the present invention; Figure 27 is a top view of the articulated boom of Figure 26 rotated to 15 s for a port tack setting; Figure 28 is an oblique view of the articulated boom of Figure 26 affixed to the mast; Figure 29A is a schematic elevation of a mainsheet system used to articulate boom to required position when sail load is applied according to an embodiment of the present invention; Figure 29B is a schematic plan view of the system of Figure 29A; Figure 30A is a side elevation of a configuration of shrouds which support spreaders on the ng mast of Figure 2; Figure 30B is a front view of the uration of Figure 30A; Figure 30C is a top view of the configuration of Figure 30A; Figure 31 is an e view of the er assembly of Figures 30A to 30C; Figure 32 is an oblique view showing the attachment of the spreader assembly of Figure 30 to the mast; Figure 33 is another oblique view of the showing the attachment of the spreader assembly of Figure 30 to the mast; and Figure 34 is an oblique section of the mast of Figure 4 adapted to fit a ring of the Description of e Embodiments Referring to Figures 1 and 2 there is shown a sailing vessel 10 comprising a deck 20 and a rigging 12 according to an embodiment of the t invention. The rigging 12 comprises a wing sail 14, a mast 16 and a boom 18. The mast 16 is ted to the deck 20 or other part of the vessel 10 (such as a cabin) by connection 24. The boom 18 is ted to the mast 16 by a gooseneck 26. In an embodiment the mast 16 is supported by guy lines in the forms of stays or shrouds 36, 38, 40 and 42 supported partway up the mast by a spreader 22.

Referring to Figure 3 the wing sail 14 comprises port and starboard substantially identical sail portions 60 and 62, each of which have a luff 28 and leach 30. The sail portions 60 and 62 are connected to the boom 18 at a clew 34 of the foot 32 of the sail 14.

The wing sail 14 is rotated to give a port tack setting. The boom 18 is set to an angle of degrees between axis 72 of boom 18 and the longitudinal axis 70 of the vessel 10. The mast 16 is rotated clockwise by 10 degrees relative to the longitudinal axis of the boom 18..

In this instance the rotation of the mast is actually 5 s from the longitudinal axis of the vessel. This will change with the sheeting angle. The try of the sail is, in this embodiment, fixed relative to the boom 18. Thus changing the sheetin g angle (or angle of attack) does not change the wing geometry. This is ant where the wing sail 14 is a mainsail as the sheeting angle changes can be large and frequent, whereas, if it is deployed as a headsail, the angle changes are typically smaller and much less frequent and hence adjusting the spar rotation relative to the vessel 10 may be an effective solution. In fact, as the headsail sheeting angles are typically in the order of 6-12 degrees, it is possible that the spar would require only small adjustment from tack to tack. In such an embodiment the mast is a spar for the headsail and rotation of the spar is controlled relative to the deck of the boat.

Between the sail portions 60 and 64 is a cavity 64. The sail is shaped by a plurality of elongated battens (270 and 272 in Figure 20), each of which extends substantially between the luff 28 and the leach 30 of one of the respective sail portions 60 and 64.

Each of the battens is in contact with an inside surface of the respective sail portion 60 or 64. Each of the battens is pivotally connected to a respective starboard or port side of the mast 16 as described in more detail below.

The rotation of the mast 16 relative to the boom 18 causes the battens connected to one of the sail portions (in this case starboard sail n 60) to be compressed along their length so as to bend the starboard sail portion 60 to increase its camber. Rotation of the mast 16 relative to the boom 18 also causes the battens connected of the port sail portion 62 to be tensioned along their length so as to partly straighten the port sail portion 62 which decreases at the connection to the mast, but further from the mast ses, the perpendicular distance between the sail portions 60 and 62, thus changing the resulting shape to increase the asymmetry of an aerofoil formed by the sail 14. In particular, the deflection of the starboard batten moves the batten away from the mean camber line.

Note, that the namic forces on the sail portions with tend to pull the ard batten out and push the port batten in, thus assisting the battens in ting in the correct direction.

Air flow travelling over the starboard sail portion 60 (from left to right of the page) has further to travel than the air flow over the port sail portion 62, which induces aerodynamic lift to the wing sail 14, which in turn propels the vessel 10.

Referring to Figure 4 a cross section of the mast 16 has profiled windward face that is about twice as broad as it is proud. The profile is rical about a central axis and has a starboard 80 side and port 82 side. The profile comprises substantially flat portions 84 and 86 at an angle to each other. The flat portions 84 and 86 may have a slight convex curve. Each flat portion 84 and 86 ends in a corner on one of the sides and at which the respective flexible sail portions 60 and 62 are connected by slide connections. n the flat portions 84 and 86 is a convex curved n 88. The mast has a aft-ward profile 102 to increase the forward-aft dimension of the mast so as to se its moment of inertia in that direction and to provide clearance between for the batten assembly 96 and the profile 102 when the sail portion is in tension (in this case port side). W hen the mast 16 is rotated in one direction the surface of the flat portion on the side with the sail potion having the resulting increased camber (in this case flat portion 84) and the surface of the that sail portion (in this case portion 60) have a relatively flat air flow over these surfaces.

Thus the airflow passing from the mast 16 to sail n 60 s relatively attached to the sail portion 60.

The ace between the mast 16 and the sail portion that is partly straightened (in this case the interface between flat portion 86 and port sail portion 62) comprises an acute angle. This shape creates an unfavourable corner at the sail-mast juncture on the windward side of the sail 14. To minimise the impact of this effect (which is most apparent at angles of incidence below 7-8 degrees) the junction between the sail 14 and mast 16 should create a somewhat rounded profile or non-sharp . This junction may not be aerodynamically smooth but the “imperfections” created by the sail and mast junction should be relatively small in dimension such that the air flow only a few millimetres from the surface is smooth and that separated airflow ches vely close to the mast 16. Further due to the profile 102 air is not encouraged to flow into the cavity 64. To e this the air gap between the luff and the mast track 92 should be kept small - only a few millimetres.

In an embodiment the angle between the flat portions is between 60 and 100 s, preferably between 70 and 95 degrees and most preferable about 90 degrees. In an embodiment the mast is proud of the corners by n 35% and 60 % of the distance between the corners of the mast 16. Preferably these amounts are between 40% and 50% and most preferably about 50%.

It is desirable that the junction between the flat portion of the mast on the leeward side and the sail on the d side is very slightly less than 180 degrees. Generally it is undesirable for the angle to be greater than 180 s due to the adverse re gradients developed being such that re-attachment of the separation bubble formed on the flat part of the mast does not reattach. An angle of less than 180 degrees causes an increase in pressure at that point such that the separation bubble is prevented from propagating further along the sail. At this point there is then reattachment of a turbulent boundary layer. The critical angles are not fixed and are dependent upon wind speed, and angle of attack of the foil, among other things.

Because the clew of the sail is ed to the boom, the amount of n applied to the sail along the boom is also important as this controls the distance between the clew and the mast. This in turn affects the amount of camber that is introduced in the sail. This camber is induced by: the action of the wind loads; by physically pulling the clew towards the mast (in-hauling); or by curvature induced by a ence between the curvature of the mast along its span (or longitudinal axis) relative to the curvature of the sail panels along the luffs. Rotation of the mast will then further increase the compression in the leeward sail portion and increase the tension in the windward sail portion, inducing a difference in camber relative to this already induced camber such that the leeward side is more cambered and the rd side is less cambered.

It is desirable in some stances (such as with high angles of attack, as when sailing off the breeze) to increase mast rotation to reduce the angle between the mast and the sail portion to provide better pressure nts to encourage chment of the separation bubble.

In an embodiment the surface of the flat portion on the side with the sail potion having the resulting increased camber and the surface of the that sail portion have the air flow thereover that is most flat substantially before a maximum rotation of the mast in that direction.

This can allow over-rotation such that the leeward side angle n the flat portion and the sail portion is less than 180 degrees, as this can be beneficial in certain circumstances.

When the wing sail 14 is rotated to give a starboard tack setting the mast 16 can be rotated in anti-clockwise to provide mirrored asymmetry of the aerofoil formed by the sail 14 to that described above. In other words this allows swapping the asymmetry from port to starboard or vice versa as required by the direction of the tack.

The mast section and sail slide configuration shown in Figure 4 provides a good aerodynamic compromise while allowing the sail to be configured for both port and starboard ion.

Thus the shape of the mast section has a relatively clean aerodynamic shape that is achieved on both port and starboard settings. The shape of the mast is such that, when rotated to induce try in the wing section by compressing one set of elongated battens on the leeward side of the sail and tensioning the opposite set of elongated battens on the windward side of the sail, no significantly adverse pressure gradients are formed in the air flowing around the sail that would cause substantial separation of the air flow (i.e. separation without reattachment) and hence a significantly detrimental loss of aerodynamic lift. Convex ure, for example where the mast is a semi-circular section d of the sail ment , causes there to be a sufficiently large drop in pressure on the leeward side of the sail just prior to the sail attachment points such that the boundary layer does not reattach. By flattening the mast section as it leads to the sail attachment point, the pressure gradient is reduced to the extent that, while there is still some tion of the flow, it re-attaches very quickly with minimal reduction in aerodynamic lift.

An onal and not inconsiderable age is that a mast of this general shape has a relatively high moment of inertia as it is large in cross section, but with low aerodynamic drag as the mast essentially s part of the wing. Note that on a conventional mast the aerodynamic penalty of the mast being at the leading edge of the sail is significant.

The screen capture from Xfoil in Figure 5 shows the pressure co-efficient and boundary layers for a mast set with 10 degrees of rotation at 9 degree angle of incidence.

The screen captures in Figures 6 and 7 show the boundary layers for the windward corner of the mast set with 10 degrees of rotation at 9 degree angle of incidence. This shape is similar to the shape shown for the rd corner in Figure 4. The stagnation point is indicated by circle at 111. The increase in ce between the windward boundary layer 112 and the sail surface 62 indicates a region of separation behind the mast sail juncture.

The screen capture from Xfoil in Figure 8 shows the boundary layers for the windward corner of the mast set with 10 degrees of rotation at 7.5 degree angle of incidence. This image shows an se in distance between the windward boundary layer 112 and the sail surface 62 both aft of the mast sail juncture and further along the sail. Reducing the angle of attack below 7.5 degrees (for this set of conditions) will result in significant tion on the windward side and hence loss of aerodynamic performance.

Region 114 has been added to the screen capture to show an airflow separation bubble created by the corner at the intersection between the flat portion of the mast and the luff.

It is desired for this separation bubble to be as short as possible so that at its end 116 the airflow reattaches to the sail portion. The rounded shape of this corner is able to shorten the length of the separation bubble.

A small separation bubble at this corner is advantageous where a slide configuration is used on the luff. In this case it is desirable that the luff of the sail does not protrude h the separation bubble. If the luff protrudes through the separation bubble there will be a significant increase in the air wanting to flow into the cavity. While this is minimised by keeping the air gap small, if the luff is in the separation bumble there is little cy for flow into the cavity. ing to Figures 4, and 9, 10A and 10B, the sail portions 60 and 62 are connected to the mast 16, on each side 80 and 82 by slides comprising a track 92 in which there is a longitudinally extending groove that holds a slider pin 94 e. As seen in Figure 10A, the slider pin 94 is fitted over and pivotally coupled to a luff rope 106 that is connected to the luff 28 of the respective sail portion 60 / 62 by luff tape 112 and is continuous along the length of the luff of each sail portion 60 / 62.

Thus the sail slide 94 is articulated close to the sail track 92 so as to ensure that the shape referred to above is ed. This is important as a substantial (more than a few millimetres) separation between the mast and sail portions 60 and 62 results in an undesirable airflow into cavity 64 between the two sail portions effectively inflating the sail 14 and creating an undesirable aerodynamic shape with low lift and high drag.

Extending either side of the slider pin 94 and over the luff tape 112 is a side batten assembly 96 that es to the sail portion and receives the luff end of one of the battens in slot 98.

An alternative to use of a slider is to use a bolt rope.

The sails portions 60 / 62 and hence necessarily the ted battens are fixed directly to the mast at the luff 28 and not via a control rod as is the case in US4766831. Further the mast is not in a two piece mast configuration (mast and control rod) as described in US4766831.

Figure 11 shows an alternative attachment mechanism in which a webbing hinge 140 is used instead of the rigid hinge of Figure 4. Here the webbing 140 still ed to a slider 94 which is received in the groove of track 92. The flexibility of the webbing 140 will allow the batten assembly 96 to be set back ly further thus smoothing or rounding this corner 142 somewhat so as to position the luff 28 inside the separation bubble 114. The extent to which the corner 142 is d is a compromise because rounding the corner on the leeward side is undesirable.

In accordance with a further aspect of the present invention a r or standard mast 250 may be encapsulated in a pocket 300 which extends up the luff so as to form mast 16 that joins the two flexible sail portions 60 / 62 together with the shape of the leading edge of the aerofoil section being formed by mast collars 200 which are substantially similar in section as the mast section described above being fitted to a smaller mast section 250.

In this way a standard mast 250 may be retrofitted with a plurality of mast collars 200 and pocket 300 so as to operate as the mast 16 described above. A more flexible fabric can be used to join the two sail portions 60 / 62 to ensure a taught skin is stretched between the s.

Referring to Figures 12 and 13, the mast collar 200 has a body with a windward l 204 having an opening and void 202 for ing and holding captive a circular mast 250.

The channel has a keyway 298 for receiving a key or tab 252 attached to the mast so that the collar 200 is unable to rotate about the longitudinal axis of the mast 250. The body of the collar 200 also has port and starboard lobes at outward ities so as to provide the ntially flat portions 284 and 286. The lobes end in channel portions 290 and 292 to which batten connectors 280 are pivotally attached. The batten connectors 280 have pivotal batten hinge fittings 282 with batten receptacles 284 for ing the luff end of the battens 270 / 272.

In an embodiment the mast collars are substantially larger across the aft-ward part of the collar than the diameter of the mast as shown.

In an embodiment the batten connector 280 comprises an articulated join 288 to provide the pivotal connection to the hinge fittings 282 which allow for the s to be aligned non-perpendicular to the mast 250. The connections 280 have a post 286 spaced by a gap 285 from the join 288. The post 286 is received in the channel 294 of the l portions 290 / 292 and each of the channel portions 209 / 292 passes through the gap 285 so as to grasp the post 286.

As shown in Figure 14 in an embodiment the hinge fitting 282 provides a means such as hole 287 by which the hinge fitting 282 can be fixed to the luff 28 of the sail portion via a cord 289 which passes through the axis of the articulation of the hinge fitting 282.

As shown in Figure 15A to 15C, in an embodiment the leading edge can be formed by the luff pocket 300 being stretched tightly between the mast collars 200 by tension on the luff 28, foot 32 and along the battens 270 and 272.

The mast collars 200 can extend laterally (substantially perpendicular to the masts udinal axis) in front of the mast 250 so as to form a projection 306 from the mast 250. When the luff pocket 300 is stretched over the mast collars 200 a corrugated effect is produced by the projections 306, the ated effect forming leading edge tubercles 304 which are known to have beneficial effect on the aerofoils lift, drag and angle of stall.

In an embodiment the luff pocket 300 is joined longitudinally by (for example) a zip such that the two flexible sail portions 60 and 62 can be separated for manufacture or repair.

According to another aspect of the ion, battens are not rigidly fixed together at the leach.

According to an aspect of the present invention the s of the sail portions 60 / 62 are moveable relative to each other such that one of the leaches is closer to the mast 16 than the other according to the height of the leach from the clew. This allows the sail to twist.

Further control of the position of the s allows control of the aerofoil profile according to the height of the battens.

It is desirable to allow span-wise twist to account for an increasing angle of attack on the wing towards the top due to windshear, where wind at the bottom of the wing sail 14 is slower than wind at the top of the sail 14. The apparent wind seen by the sail 14 is the vector sum of the vessel velocity and the wind velocity and hence the angle is greater at the top.

Figure 16 shows the mast rotated to 30 degrees by (say) 15 degrees of rotation and 15 degrees of sail twist. Figure 17 shows the mast rotated to 30 degrees but the s allowed to slip 1.7% of the chord length. The slip is evident at the leach of the sail. Figure 18 shows the mast rotated to 15 degrees with no slip at the leach. Note how this section is substantially similar to the one in Figure 16.

Figure 19 shows a pair of battens 270 (starboard) and 272 (port), each with a fitting 320 and 322 at the leach end. The fittings 320 / 322 are for fitting to gs of the starboard sail portion 60 and webbings of the port sail portion 62, tively. The gs have a hole or slot for a control line 270 to be attached. Thus the leach ends of s are moveable relative to each other. Further the leaches of the sail portions 60 and 62 are moveable relative to each other. Sail portion 62 is translucent in Figures 19 and 21.

The sail portions 60 and 62 have batten pockets 350 and 352 for receiving battens 270 and 272, respectively.

A batten control line 330 runs along the batten pocket 350 in one sail portion (in this case sail portion 60). This l line 330 passes through the leach end of the batten at fitting 320 and extends to the other fitting 322 where it is then ated at the end of the other batten.

Figures 20A and 20B show port and starboard settings, respectively, of the leach control line 330 running along the batten 270, through the batten end fitting 320 and to the batten end fitting 322 of the other batten 272.

The sail portions 60 and 62 are shown with slip ve to each other at the leach 30 on a port tack setting. Cord 289 connects the leach of the sail n 60 / 62 to the batten 322.

Connecting loop 344 connects the cords 289 to hold the sail portions 60 / 62 together.

Figure 22 shows the leach control line 330 runs through a pocket opening 341 into and along the batten pocket 350 and through the end of the batten fitting 320. The line 342 is connected to the end of the corresponding batten on the other sail portion.

The batten l line 330 is connected to pulley 371 which is in turn connected to a luff control line 364. Figure 23 shows the attachment of the batten control line 330 to a luff control line 364 on the uppermost controlled batten in the sail 14. Luff control line 364 terminates at the loop 372 fixed to the luff. When the luff control line 364 is drawn, it pulls on pulley 371 via pulley 370 so as to draw the batten control line 330.

When the batten control line 330 is eased the s can then move relative to one another. The batten control line 330 is connected to the luff control line 364, such that the control line 364 can be adjusted from the bottom of the sail.

Thus in this embodiment there is an able or flexible join between the leach ends of battens of the same height up the sail. The adjustable or flexible join may be controlled to allow a substantial amount of movement between the two adjacent leaches along the length of the elongated battens thus allowing the sail portions to rotate at the luff end a substantial r amount before the compressive and tensile loads are induced in the elongated battens thus allowing the flexible sail portions to rotate, or twist, relative to the mast section without introducing thickness to the wing section. This is important because as the sail twists in the upper portions of the sail under wind load, effectively more mast rotation is induce relative to the sail portions. This subsequently causes more thickness to be induced into the wing section. This is undesirable as the section may become too thick and lead to stalling of the section, or it may also produce more lift (ahead of stall) and this may be undesirable.

In an embodiment the elongated battens on one sail portions are prevented from moving laterally apart at the leach from the corresponding batten on the other sail portion by a connecting ring or loop 344 which connects g straps / cords 289 which run longitudinally along the both batten pockets (and are typically also used to secure the batten into the ). The batten control line 330 can also pass through this loop or ring 344 so as to ensure that the loop or ring is pulled to the leach on each tack.

In an embodiment the amount of movement n the two adjacent leaches along the length of the elongated battens can be controlled to provide the appropriate amount of section thickness at the rotated or twisted cement of the sail portions.

In an embodiment a means is provided the allow substantially more amount of movement between the two adjacent leaches along the length of the elongated battens at the top of the sail portions relative to the bottom of the sail portions to allow an increasing onal displacement of the sail ns closer to the top of the sail. This is achieved by either a self-adjusting mechanism whereby the batten control lines 330 are fixed to a single luff control line 364 as shown in Figure 24 and the upper battens are more prone to twist and hence will take up more of the luff control line 364. Alternatively, as shown in Figure 25 each batten control line can have a luff l line 364, 365 and 366 and these can be affixed to a control lever 380 at the boom to allow adjustment and pre-setting of the twist.

In a still further aspect of the present invention controls of the amount of movement between the two adjacent leaches along the length of the elongated s can be linked to the boom section of the sail in a manner which allows the onal displacement at the top of the sail to increase as the downward force on the boom is decreased.

Figure 21 shows an alternative for of leach control. Here the amount of movement between the two adjacent leaches along the length of the elongated battens can be controlled by the use of a flexible elastic joiner 390, for example elastic shock cord. The n in the shock cord can be adjusted by the use of adjuster 392 to provide a varying amount of movement at each batten pair. Note that Figure 21 shows one possible attachment of the shock cord whereas any attachment either of the battens or the leaches adjacent to the battens may be used to achieve the same result.

According to an aspect of the present invention the boom pivotally d to the mast at one end and which at another end the sail portions are coupled at a clew, wherein the boom is controllable articulated between its ends.

As shown in Figure 26 to Figure 29B, an articulated boom n is a means to rotate the mast 16 and induce the wing section asymmetry whereas the boom 18 which is lated with a vertical hinge 50 which allows the boom 18 to displace in the midsection to either port or starboard such that when the vessel is on a port heading the boom mid-section is displaced to port and when the vessel is on a starboard heading the boom mid-section is displaced to starboard and the boom is fixed to the mast in a manner that does not allow the lateral angle between the front section of the boom and the mast section to change. Thus when the boom mid-section is displaced to port the mast rotates in a clockwise direction as viewed from the top of the mast and when the boom midsection is displaced to ard the mast rotates in an anti-clockwise direction as viewed from the top of the mast. The boom 18 has a first portion 51 extending form the mast 16 to the hinge 50, and a second portion extending form the hinge 50 to the end of the boom In Figure 27 the articulated boom is rotated to 15 degrees for a Port tack setting.

Figure 29B shows the articulated boom affixed to a mast and d into a port tack configuration.

In an embodiment a means is provided by which the load required to articulate the boom is applied by the main sheet system 414 y the wing section asymmetry is induced by the force of the wind and thus s the try for a port heading when the wind is substantially from the port side of the vessel, and induces the asymmetry for a starboard g when the wind is substantially from the starboard side of the vessel.

In an embodiment a means is ed to limit the amount of lateral displacement of the boom mid-section to either port or starboard thus limiting the amount of mast rotation and hence wing section thickness that is induced.

Cords 410 and 412 are connected to the second portion of the boom 53. In this setting cord 410 is slack and cord 412 is tight urging to the boom 18 to articulate in a particular direction. The amount of articulation may be controlled by a control arm 402 connected to the second portion 53, but extending past the hinge 50. The arm may be controlled by a cord 416.

Cord system 52 may extend between the boom 18 and the deck 20 and in some ments may operate as the mainsheet system or may operate to provide control over the ntal angle of the boom 18 so as to e as a boom vang.

In ance with a still further aspect of the present invention the mast may be supported by stays or shrouds 36, 38, 40 and 42 and it may be an engineering requirement to have one or more spreaders 22 or mid panel support for the mast 16. The spreader 22 is rotatable about an axis of rotation of the mast, such that the spreader 22 is substantially stationary relative to the deck 20 of the boat. In an embodiment the mast 16 can rotate through an operational range (say +/-55degrees). The spreader 22 is ed to the mast via a ring or hoop 400 that is supported by the stays thus allowing the mast 16 to rotate about (or close to) its geometric centre and hence resulting in minimal deflection of the stays or shrouds when the mast is rotated.

Stays 38, 42 and Lower shrouds L1 and L2 attach to the deck at point 44 and stays 36, 40 and Jumper shroud 36 attach to the upper part of the mast at 46. The lower end of the Jumper shroud 36 and the upper ends of Lower shrouds L1 and L2 are coincidentally connected together (or in close proximity) to the Spreader 22. Where there are multiple spreaders used, the Jumper shroud is connected between the lower and upper spreaders (and then to the upper part of the mast) and the diagonal shrouds are connected for the upper spreaders are ted to the tips of the spreaders below. In this way multiple spreaders can be spaced along the length of the mast.

The spreader 22 has elongate arms 402 that are typically swept aft. The stays 38 and 40 are attached to tips of the arms 402. Stays 42 and 36 are attached between the nose 404 and the aft face 406 of the spreader 22. An aft face 406 opposite the nose 404 has the ring 400 connected to it by connection 410. The mast 250 is able to be located in the inside 408 of the ring 400. The ring 400 is supported at the d height on the mast 16. The spreader 22 is able to be both twisted and d downwards by connection 410 so as to provide two degrees of freedom of the spreader assembly. The spreader 22 may be provided with a hole 412 between the nose 404 and aft face 406 to allow the passage of cord from one side of the spreader 22 to the other. In this case a pin connecting the spreader 22 to the ring 400 passes through the hole 412 and the each of the Lowers shroud and the Jumper shroud are attached to this pin. The Lowers and the jumpershroud must be ted to the spreader assembly.

The ring 400 passes between the sail tracks 92 and the mast 16 to allow hoisting of the sail portions 60 and 62. Figure 34 shows an embodiment of a mast 16 that has lobes 424 separated by a gap 426. An insert 420 extends between the lobes 424 but also provides a space 422 in which the ring 400 is positioned. The lobes 424 and the insert 420 continue the flat portions (of which flat portion 84 is shown). The slider tracks 92 are formed in the lobes 424.

The present invention provides for a wing sail which can be hoisted, reefed and stowed much like a conventional sail and that can produce a semi rigid asymmetrical wing n aerofoil. The present invention provides for the y to adjust the thickness and camber of the aerofoil wing section and to e asymmetry on both port and starboard headings.

The present invention provides for substantial simplification over the prior wing sail, thus reducing weight and cost.

The present invention also provides a means of controlling span wise twist in the aerofoil section to further improve the aerodynamic performance of the wing sail. The present invention also provides means of attachment of the sail portions to the mast using sail slides which allow the sail to be stacked when not in use.

The t invention also provides for the use of a pocket luff sail where the leading edge shape is achieved by the use of mast collars which are ntially similar to the mast shape. The present invention also provides for leading edge tubercles being formed by the mast collars further enhancing the aerodynamic performance of the wing sail.

The present invention also es a means for controlling twist in the sail. The present invention also provides a means of supporting the wing sail rigging using rotating spreaders.

As with the original invention, the wing sail being controlled in the present invention is characterised in that comprises a le 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 flexure in at least two dimensions which stiffen the sail portions from luff to leach.

Modifications may be made to the present invention within the context of that described and shown in the drawings. Such cations are intended to form part of the invention bed in this specification.

Claims (26)

Claims

1. A rigging comprising: a mast having a starboard side and a port side, wherein the mast is controllably rotatable in either direction about a longitudinal axis; 5 a flexible sail comprising a ard flexible sail portion and a substantially identical port flexible sail portion, each flexible sail portion having a luff and a leach, wherein the luff of each sail portion is connected to a respective side of the mast; a plurality of elongated battens, each of which extends substantially between the luff and the leach of one of the respective sail portions, each of which is in contact with 10 the respective flexible sail portion, and each of which is pivotally connected to a respective outermost part of the starboard or port side of the mast; wherein rotation of the mast causes the s connected to one of the sail portions to be ssed along their length so as to bend one of the sail portions to increase the camber f and causes the battens connected on the other sail portions 15 to be tensioned along their length so as to partly straighten the other sail portion which changes the shape of an aerofoil formed by the sail.

2. A rigging according to claim 1, wherein the mast comprises substantially flat portions at an angle to each other, each flat portion ending in a corner on one of the sides 20 of the mast and at which the respective le sail portions are connected, wherein when the mast is rotated in one direction the surface of the flat portion on the side with the sail portion having the resulting increased camber and the surface of the that sail portion have an air flow there-over that is relatively flat or undergoes a relatively small change in direction.

3. A rigging according to any one of the preceding claims, wherein an interface between the mast and the sail portion that is partly htened has a rounded or nonsharp corner. 30

4. A rigging according to any one of the ing , wherein the mast is profiled so that when the mast is rotated in one direction airflow passing from the mast to the sail portion with the increased camber remains relatively attached to the sail n.

5. A rigging according to any one of the preceding , wherein the mast is 35 profiled so that when the mast is d in one direction airflow passing from the mast to the sail portion that is partly straightened reattaches to the sail portion relatively close to the mast.

6. A rigging according to any one of the preceding claims when dependent on claim 5 2, wherein the angle between the flat portions is between 60 and 100 degrees.

7. A rigging according to any one of the preceding claims, wherein the degree of rotation of the mast controls the compression and tension in the battens. 10

8. A g according to any one of the preceding claims, wherein the leaches are controllably moveable relative to each other such that one of the leaches is closer to the mast than the other according to a tack of the sail.

9. A rigging according to claim 8, wherein the movement of the leaches is controlled 15 by controlling the separation allowed between leach ends of the battens.

10. A g according to claim 8 or claim 9, wherein nt of the leaches controls the mean camber of the aerofoil. 20

11. A rigging according to any one of the ing claims when dependent on claim 8, n the rigging further comprises a boom pivotally coupled to the mast at one end and which at another end the sail portions are coupled at a clew.

12. A rigging ing to claim 9 or 10, wherein the amount of separation n 25 the leaches is varied according to the length along the leach from the clew.

13. A rigging according to any one of the preceding claims when dependent on claim 8, further comprising a boom that is pivotal in a horizontal plane, wherein an angle of the boom in the horizontal plane is controllable and the angle of the boom in the ntal 30 plane is configured to control the separation allowed between leach ends of the battens.

14. A rigging according to any one of claims 1 to 12, further comprising a boom that is l in a horizontal plane between its ends and rotation of the mast is adjusted relative to a udinal axis of the boom.

15. A rigging according to any one of the preceding , wherein the flat portion of the mast is formed by a mast pocket stretched between mast collars.

16. A rigging sing: a mast having a starboard side and a port side, wherein the mast is controllably rotatable in either direction about a longitudinal axis; a flexible sail comprising a ard flexible sail portion and a substantially 5 identical port flexible sail portion, each flexible sail portion having a luff and a leach, wherein the luff of each sail portion is connected to a respective side of the mast; a plurality of elongated battens, each of which extends substantially between the luff and the leach of one of the tive sail portions, each of which is in t with the respective flexible sail portion; 10 wherein the battens connected to one of the sail portions may be compressed along their length so as to bend one of the sail portions to increase the camber thereof and causes the battens connected of the other sail portions to be tensioned along their length so as to partly straighten the other sail portion which changes the shape of an aerofoil formed by the sail; 15 wherein the leaches are controllably moveable relative to each other such that compression is applied to the one or more of the battens on a leeward side of the sail by n in a corresponding one or more of the battens on a windward side of the sail.

17. A rigging according to claim 16, wherein the leaches are controllably moveable 20 relative to each other so as to determine the spacing between the leaches.

18. A rigging according to claim 16 or 17, wherein the control of the movement of the leaches is according to the height of the respective battens in the flexible sail. 25

19. A rigging sing: a mast having a starboard side and a port side, n the mast is controllably rotatable in either ion about a longitudinal axis; a flexible sail sing a starboard flexible sail portion and a substantially cal port flexible sail portion, each flexible sail n having a luff and a leach, 30 wherein the luff of each sail portion is connected to a respective outermost side of the mast; a plurality of elongated battens, each of which extends substantially between the luff and the leach of one of the respective sail portions, each of which is in contact with the respective flexible sail portion; 35 wherein the battens connected to one of the sail portions may be compressed along their length so as to bend one of the sail portions to increase the camber thereof and causes the battens connected of the other sail portions to be tensioned along their length so as to partly straighten the other sail portion which changes the shape of an aerofoil formed by the sail; wherein leach end of battens are moveable relative to each other.

20. A rigging according to claim 19, wherein the ve displacement of each of the leach ends of the battens is controllable.

21. A rigging according to claim 19 or 20, wherein the relative cement of the 10 leach ends of the s is automatically controlled by the angle of a boom to which the sail portions are attached.

22. A rigging ing to any one of claims 19 to 21, wherein the sail portions provide ing relative movement of corresponding portions of the leaches to each other, where 15 the amount of relative movement is controlled according to the height of the leach portions from a deck of a boat on which the rigging is led.

23. A rigging comprising a mast pocket covering the mast and connected to sail portions forming either side of a wing sail, wherein the leading profile of the mast pocket is 20 provided by a plurality mast collars for attachment of battens extending inside and in contact with the sail portions, such that the s control the aerodynamic shape of the sail portions by increasing the camber of one of the sail ns according to a direction of rotation of the mast. 25

24. A rigging according to claim 23, wherein the mast collars profile the mast such that when the mast is rotated in one direction airflow passing from the mast to sail portion with the increased camber remains relatively attached to the sail portion.

25. A mast collar for coupling to a mast, the mast collar rotatable with the mast and 30 connected to on each side to a sail portion, the sail portions forming either side of a wing sail, the mast collar being configured for pivotable attachment of battens extending inside and in t with the sail portions, such that the battens control the aerodynamic shape of the sail portions by increasing the camber of one of the sail portions according to a direction of on of the mast.

26. A wind propelled craft comprising the rigging as claimed in any one of the previous claims. 1 /18 2 /18 3 /18 on +25o Boom @15o 94 96 96 102