Ship sail assembly and ship equipped with same

Abstract

The present invention relates to a sail assembly (80) for a watercraft having a deck, the sail assembly comprising: - a mast (81) mounted at an incline relative to the deck of the vessel on a motorized shaft having an axis of rotation inclined relative to the deck of the vessel; -Several spars (85) installed on both sides of the mast at an angle to the mast; - A sail (83) between the ends of two successive spars located on the same side of the mast, together with motorized means for unfurling and folding said sail. Equipped with. An embodiment of the present application discloses at least one sail comprising a rigid upstream half-sail (83) and a rigid downstream half-sail (82) connected together by a hinge (86) installed between two ends of a continuous spar (85).

Description

[Technical Field]

[0001] The present invention relates to a sail assembly for a vessel and to a vessel equipped with same, and is particularly applicable to the field of sail-powered propulsion of merchant vessels. [Background technology]

[0002] All sailing projects to reduce CO2 production rely on the following very simple equation to determine the aerodynamic force generated by the sails: F=0.5*ρ*s*v 2 *Coef Depends on where: F is the force in Newtons, P is the air density, S is the area of ​​the sail, V is the apparent wind speed, Coef is a coefficient of performance that depends on the shape of the rough surface extension, the Reynolds number, etc.

[0003] Some projects aim to increase the lift of the sail by using thicker profiles (like the profile of an airplane wing) and reduce the drag of the sail. Other projects to increase the aerodynamic force affect the speed by seeking wind above sea level or by generating artificial overspeed by rotating cylinders.

[0004] The asymmetric, thick profile generates a maximum lift coefficient of approximately 1.7.

[0005] A symmetrical, thick profile requires twice as much material as a thin profile, say a flexible sail, which would have roughly the same lift coefficient of 1 to 1.2. The relative reduction in drag from a thick profile is an important advantage for configurations where the apparent wind direction is very close to the vessel's path (such as a racing multihull or a cargo ship using sails as a backup). Wind speeds at 200 meters above sea level are 50% higher than at sea level, and with the square of the wind speed, one can expect twice the thrust for the same surface area. This is sufficient to stabilize kites with a surface area of ​​several hundred square meters.

[0006] However, none of the above sail assemblies have all the rigging qualities required for merchant ships, including: -Large surface area due to relatively weak average winds; -Easy reduction of surface area due to windy conditions, which may be strong or very strong; - limited clearance, where clearance is the total height of the rigging; -Efficient geometry when Rn is small, i.e. when wind is weak; -Good durability in strong winds; - Small footprint on deck to facilitate port operations; -Full automation, without affecting crew numbers; - Good retractability, i.e. very quick retraction with minimal resistance; -Relatively inexpensive; and -It must be sustainable.

[0007] Patent document 1 is known, which discloses a watercraft in which a rigid sail assembly comprises three half sails that together form an arc positioned at the top of a rotating mast, however, the three half sails form only one sail positioned on only one side of the mast.

[0008] Patent document 2 is known, which discloses a sail assembly consisting of three rigid sails that slide along the sail, however, the three sails are positioned on the same side of the mast.

[0009] Patent document 3 is known, which discloses a flexible sail assembly in which multiple sails are stacked one on top of the other and secured along the entire length of a spar, again with the sails only being installed on one side of the mast.

[0010] Patent document 4 is known, which discloses a rigid sail assembly comprising five sails stacked one on top of the other, however, these five sails form only a single large sail that is positioned on only one side of the mast. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Jitsuzen Showa 60-110098 [Patent Document 2] Chinese Patent Application Publication No. 104176222 [Patent Document 3] German Patent Application Publication No. 3718414 [Patent Document 4] U.S. Patent Application Publication No. 2021 / 163112 Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention proposes to obtain all or some of the above-mentioned qualities by means of at least one biplane sail assembly. [Means for solving the problem]

[0013] Other advantages, objects and particular features of the present invention will become apparent from the following non-limiting description of at least one particular embodiment of the sail assembly that is the subject of the invention, which description refers to the accompanying drawings, in which: [Brief explanation of the drawings]

[0014] [Figure 1]FIG. 1 shows a schematic perspective view of the general inventive concept of the present invention. [Figure 2] FIG. 2 shows a schematic top view of a first particular embodiment of the sail assembly that is the subject of the present invention. [Figure 3] FIG. 3 shows a schematic perspective view of the sail assembly shown in FIG. 2 partially deployed and partially folded. [Figure 4] FIG. 4 shows a schematic perspective view of a second particular embodiment of the sail assembly that is the subject of the present invention, partially deployed and partially folded. [Figure 5] FIG. 5 shows a schematic side view of a first particular embodiment of the vessel that is the subject of the present invention. [Figure 6] FIG. 6 shows a schematic top view of different points of the sails of a second particular embodiment of the vessel that is the subject of the invention, with all sail assemblies deployed. [Figure 7] FIG. 7 shows a schematic side view of a third particular embodiment of the watercraft that is the subject of the present invention, with the sail assembly partly deployed and partly folded. [Figure 8] FIG. 8 shows a schematic top view of the vessel shown in FIG. 5 with the mast pivoted to release the vessel deck. [Figure 9] FIG. 9 shows a schematic perspective view of a third particular embodiment of the sail assembly that is the subject of the present invention, partially deployed and partially folded. [Figure 10] FIG. 10 shows a schematic top view of the mechanism for deploying and folding the sail assembly shown in FIG. [Figure 11] FIG. 11 shows a schematic top view of different points of the sail of a fourth particular embodiment of the vessel that is the subject of the invention. [Figure 12] FIG. 12 shows a schematic side view of a fifth particular embodiment of the vessel that is the subject of the present invention. [Figure 13] FIG. 13 shows a schematic top view of a third particular embodiment of the sail assembly shown in FIG. [Figure 14]FIG. 14 shows a schematic top view of different points of the sails of a sixth particular embodiment of the vessel that is the subject of the present invention, with all sail assemblies deployed. [Figure 15] FIG. 15 shows a schematic top view of the sail assembly shown in FIG. 2 with the sail assembly deployed in various ways. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention aims to remedy all or some of the inconveniences of the prior art. To this end, according to a first aspect, the invention contemplates a biplane sail assembly for a vessel having a deck, the sail assembly comprising: - a mast extending along an axis, installed at an incline relative to the deck of the vessel, on a motorized shaft having an axis of rotation inclined relative to the deck of the vessel; -Several spars installed on each side of the mast at an angle to the mast; - for each side of the mast, a sail between the ends of two consecutive spars located on the same side of the mast, together with motorized means for unfurling and folding this sail; Equipped with.

[0016] These configurations provide biplane sails with low clearance. Additionally, motorization of the rotation of each mast allows adjustment of the position of the sail relative to the sail point of the sailing vessel.

[0017] Furthermore, a sail assembly that is biplane or has a small angle of incidence between the two sails on one spar (for example 15°) will provide better lift and will not loosen in the wind.

[0018] In some embodiments, the sail assembly comprises a yard at each end of each spar, each yard extending along an axis perpendicular to the axis of the mast, and each sail is flexible and mounted between two parallel yards, the yards on either side of the mast being parallel to each other.

[0019] These configurations allow flexible sails to be implemented at low cost.

[0020] In some embodiments, the axis of one yard on one side of the mast is parallel to the axis of one yard on the other side of the mast.

[0021] In some embodiments, the axis of one yard on one side of the mast intersects the axis of one yard on the other side of the mast. In some embodiments, the sail assembly comprises, for each flexible sail, a retaining line between the yards surrounding the sail, the line being positioned on the windward side of the yard, and the motorized means for deploying and folding the sail comprises a sail furler consisting of a cylindrical tube rotating about a fixed cable, the sail being connected to the furler by a bolt rope passing through a channel in the furler.

[0022] These configurations allow for motorized sail deployment.

[0023] In some embodiments, the sail assembly comprises two parallel masts that jointly support a spar.

[0024] In some embodiments, at least one sail comprises a rigid upstream half-sail and a rigid downstream half-sail connected together by a hinge located between two ends of a continuous spar.

[0025] In some embodiments, the half sails on one side of a spar have the same orientation as the half sails on the other side of the spar.

[0026] In some embodiments, the half sails on one side of a spar have a different orientation than the half sails on the other side of the spar.

[0027] These configurations allow the sails to be folded or deployed by rotating one half sail about a hinge shared with the other half sail.

[0028] In some embodiments, each half sail is a parabolic arc.

[0029] With these configurations, the shape of the deployed sail roughly corresponds to the shape of a flexible sail catching the wind.

[0030] In some embodiments, for each rigid sail, the motorized means for deploying and folding the sail comprises an actuator.

[0031] In some embodiments, the sail assembly comprises means for controlling the motorization means for deploying and folding the upstream half-sail relative to the downstream half-sail, the control means being configured to fold the half-sails on top of each other when tacking and gybing and to reverse curves between starboard and port tacks.

[0032] According to a second aspect, the invention contemplates a watercraft equipped with at least one sail assembly according to the invention.

[0033] In some embodiments, the watercraft comprises a sail assembly according to the invention around the foremast and a sail assembly according to the invention around the mizzen mast.

[0034] This description is non-limiting, and each feature of one embodiment may be advantageously combined with any other feature of any other embodiment. Note that the drawings are not to scale.

[0035] As will be understood from reading this description, different inventive concepts can be implemented by one or more methods or devices described below, some examples of which are given here. The acts or steps performed within the framework of a method or device implementation can be ordered in any suitable way. As a result, it is possible to construct embodiments in which these acts or steps are performed in an order different from that shown herein, including performing some acts simultaneously, even though in the embodiments shown herein they are presented as acts performed sequentially.

[0036] As used in this document and in the claims, the term "and / or" shall be understood to mean "one or the other, or both" of the elements connected by the term, i.e., whether consecutive or separate. Multiple elements listed with "and / or" shall be interpreted in the same manner, i.e., "one or more" of the elements connected by the term. Elements other than the elements specifically identified by the "and / or" clause may be present, whether or not associated with those elements. Thus, as a non-limiting example, when the term "A and / or B" is used in conjunction with an open-ended phrase such as "comprising," this may refer, in one embodiment, to only A (but potentially including elements other than B); in another embodiment, to only B (but potentially including elements other than A); or in yet another embodiment, to both A and B (but potentially including other elements).

[0037] As used in this description and in the claims, the phrase "at least one" in reference to a list of one or more elements shall be understood to mean at least one element selected from one or more elements in the list of elements, but not necessarily including at least one of each element specifically listed in the list of elements, and not excluding any combination of elements in the list of elements. This definition allows for the optional presence of elements other than those specifically identified in the list of elements, whether or not the phrase "at least one" is associated with those elements. Thus, as a non-limiting example, "at least one of A and B" (or synonymously "at least one of A or B," or synonymously "at least one of A and / or B") can mean that in one embodiment, at least one, and possibly more than one, A is present and no B (but may include elements other than B); in another embodiment, at least one, and possibly more than one, B is present and no A (but may include elements other than A); in yet another embodiment, at least one, and possibly more than one, A, and at least one, and possibly more than one, B (but may include other elements); etc.

[0038] In the claims and the following description, all transitional expressions such as "comprising," "including," "bearing," "having," "containing," "involving," "made of," "formed of," etc., shall be understood to be open-ended, i.e., meaning "including, but not limited to." Only the transitional expressions "consisting of" and "consisting essentially of" shall be understood as closed or semi-closed expressions, respectively.

[0039] FIG. 1 shows a sail assembly 20 for a vessel (not shown) having a deck 24. The sail assembly 20 includes a mast 21 mounted at an angle relative to the vessel's deck 24 on a motorized shaft (not shown) having a rotation axis 25 inclined relative to the vessel's deck. Typically, the mast and rotation axis 25 are vertical, although in some variations they are inclined. The axis of the shaft generally corresponds to the axis of the mast 21. The sail assembly 20 also includes multiple spars (not shown) mounted on either side of the mast 21 at an angle relative to the mast 21. The sail assembly 20 includes at least one sail 22, 23 on each side of the mast 21 and motorized means (not shown) for deploying and folding the sail. For example, a furler (not shown) is positioned at the windward end of the yards 34 and / or 36 to enable the flexible sail 22 to be deployed or folded. A sail furling system generally consists of a cylindrical tube that rotates around a fixed line. The sail is connected to the furler by a bolt rope which passes through a channel in the furler.

[0040] Sail assembly 20 is therefore biplane, which allows sails 22, 23 to harness a greater portion of the wind's force.

[0041] In a first embodiment of the sail assembly shown in Figures 2 and 3, the mast 31 supports multiple spars 35 inclined relative to the mast 31. In this embodiment, the spars 35 extend in a plane perpendicular to the mast 31 at various heights above the mast 31. Each end of each spar 35 supports a yard 34 and / or 36. The yards 34 and / or 36 may be parallel to one another. Each yard 34 and / or 36 extends along an axis 26 and / or 28, respectively, parallel to a vertical plane (not shown) perpendicular to the axis 25 of the mast 31. For example, each sail is flexible and is installed between two parallel yards 34 and / or 36. Preferably, the yards 34 and / or 36 on one side of the mast 31 are parallel to one another. Preferably, the yards 36 on one side of the mast 31 are parallel to the yards 34 on the other side of the mast 31. In other words, the axis 26 of the yard 34 is preferably parallel to the axis 28 of the yard 36 .

[0042] In some variations (not shown), the axis 26 of the yard 34 on one side of the mast 31 intersects the axis 28 of the yard 36 on the other side of the mast 31. In other words, the yards 34 on one side of the mast 31 are parallel to each other. The yards 36 on one side of the mast 31, for example, have a different orientation than the yards 34 on the other side of the mast 31. In other words, the orientation of the yard 91 on one side of the mast 93 may be independent of the orientation of the yard 92 on the other side of the mast, and the link between the yard and the spar is pivotable and motorized for this purpose. The acute salient angle (not shown) formed by the intersecting axes 26 and / or 28, referred to as the "angle of attack," may be 20° or less. Preferably, the acute salient angle (not shown) formed by the intersecting axes 26 and / or 28 is 10° or less.

[0043] In some variants, the spar consists of two parts mounted on a pivot link with an axis parallel to the axis of the mast, and motorisation allows the angle between these two parts of the spar to be changed.

[0044] Between two consecutive yards 34 and / or 36 on the same side of the mast 31 there is a flexible sail, for example made of canvas. The flexible sail on the left side of the mast 31 is designated 32, and the flexible sail on the right side of the mast 31 is designated 33. A line 37 connects the two ends of the consecutive yards 34 and / or 36 on the same side of the mast 31 at the front (left side in Figures 2 and 3), i.e. the windward side, of the sail assembly. This line 37 holds the leading edge of the flexible sail 32 or 33. Figures 2 and 3 show three flexible sails 32, 33 on each side of the mast 31, strung between four yards 34 and / or 36. Naturally, in some variations of this first embodiment of the sail assembly that is the subject of the present invention, the number of sails and yards may be different.

[0045] FIG. 2 shows the resultant aerodynamic forces acting on the sails 32, 33 in a crosswind, in the form of arrows F1, F2. Note that these resultant forces F1, F2 are located aft of the axis of rotation 25, allowing the sail assembly 30 to be retracted. More generally, the location of the aerodynamic forces depends on the angle of attack of the profile relative to the wind. In this case, the force is located at approximately 25% of the chord length. This situation is most unfavorable for allowing the rigging to be retracted. This corresponds to a small angle of attack, on the order of 20°. As the angle of attack increases, the point of application of the force "move back," terminating at 50% of the chord length at a 90° angle of attack. In other words, when the mast 31 is free to rotate about the axis of rotation 25, the sail assembly 30 automatically orients itself upwind, thereby counteracting the resultant aerodynamic forces.

[0046] 15 shows sail assembly 30 with sails 32 and / or 33 deployed in various ways. For example, a furler (not shown) may be positioned at the windward end of yards 34 and / or 36 to allow for the deployment or folding of flexible sails 32, 33. The furler may deploy or fold one sail 32 and / or 33 relative to the other.

[0047] The sail assembly 30 is free to rotate about the mast 31 while maintaining its biplane configuration, for example.

[0048] In some variations, the sail assembly 30 rotates freely around the mast 31 while maintaining the same acute convex angle formed by the axes 26 and / or 28 of the yards 34 and / or 36.

[0049] The second embodiment of the sail assembly 40 shown in Figure 4 is similar to the first embodiment with two flexible sails on each side of the mast, except that the mast 31 is replaced by two parallel masts 38, 39 which jointly support the spar 35 and yards 34 and / or 36.

[0050] Figure 5 shows a vessel 50 with two masts 31 on a deck 54 and two sail assemblies 30 around these masts 31. In this figure 5, all sails 32, 33 are unfurled and tensioned.

[0051] As shown in FIG. 6, different points on the sail of a vessel 60 equipped with a sail assembly 30 can harness the power of the wind by motorized rotation of the mast 31 according to the orientation of the sail as known in the prior art.

[0052] Figure 7 shows a vessel 70 with a sail assembly 30 around a foremast 31 and a sail assembly 40 around double mizzen masts 38, 39. In this Figure 7, the upper sails 32, 33 are folded and the lower sails 32, 33 are unfolded and tensioned.

[0053] 8 shows the vessel 50 with the sail assembly 30 spaced apart from the vertical plane of the vessel's deck. To this end, the foremast 31 is rotated so that the maximum extension of the yards 34 and / or 36 points towards the bow of the vessel 50. Conversely, the mizzen mast 31 is in a position such that the maximum extension of the yards 34 and / or 36 points towards the stern of the vessel 50. Such an implementation of the invention makes it possible to eliminate any overhang of the sail assembly elements from the central part of the deck 54 of the vessel 50, facilitating the loading and unloading of supplies or other products.

[0054] In the first two embodiments of the sail assemblies 30, 40, these sail assemblies are canvas biplanes that are automatically retractable, the yard is linear, and the aerodynamic force is behind the axis of rotation 25 of the mast 31 or 38, 39.

[0055] These two first embodiments 30, 40 of the sail assembly that is the subject of the present invention have the following advantages: -Large sail surface area; -Limited clearance; -Good durability in strong winds; -Small footprint on deck; - Mast rotation motor automation; -Automatic retractability.

[0056] In a third embodiment of a sail assembly, shown in Figures 9-13, a single mast 81 supports multiple spars 85 inclined relative to the mast 81. In this embodiment, the spars 85 extend in a plane perpendicular to the mast 81 at various heights above the mast 81. Each end of each spar 85 supports a rotating shaft 89 (see Figure 10) of a rigid half-sail 83 for a rigid downstream half-sail 82. A hinge 86 and a deployment / folding means 87 connect the downstream half-sail 82 to the upstream half-sail 83. Note that the rotating shafts 89 (see Figure 10) supported by the ends of spars 85 on the same side of the mast can be separate and rotated independently by multiple motors (not shown), or they can be combined and rotated by the same motor (not shown). In Figure 9, one upstream half-sail 83 is folded onto the downstream half-sail 82, and three upstream half-sails 83 are deployed.

[0057] 10, the deploying / folding means 87 for folding the downstream half sail 82 onto the upstream half sail 83 may be, for example, an electric or hydraulic actuator. By increasing the extension of this actuator, the upstream half sail 83 can be deployed. Conversely, by decreasing the extension of the actuator, the upstream half sail 83 can be folded onto the downstream half sail 82.

[0058] 9 and 13 show two sails articulated between three spars 85 on each side of the mast 81. Naturally, in some variations of this third embodiment of the sail assembly that is the subject of the present invention, the number of sails and yards may be different.

[0059] 9-13, each half sail 82 and / or 83 is a parabolic arc, i.e., has a symmetrical profile about the axis of rotation of, for example, the rotating shaft 89.

[0060] 11, the power of the wind can be harnessed at different points on the sail of a fourth embodiment of a vessel 90 equipped with a sail assembly 80 by motorized rotation of the mast 81 about the axis of rotation 25 and by deploying and folding the rigid upstream half-sail 83 according to sail orientations known in the prior art. However, the means for controlling the means 87 for deploying and folding the rigid upstream half-sail 83 are configured to fold the half-sail 83 relative to the downstream half-sail when the vessel 90 is tacking and gybing, and to reverse the curve of the deployed sail between starboard and port tacks.

[0061] For a given spar 85, the half sails 82, 83 on one side of the spar are symmetrical to the half sails 82, 83 on the other side of the spar, for example, about axis 95, which is the axis of symmetry of the mast 93, perpendicular to axis 25. In other words, the half sails 82, 83 on one side of the spar 85 have the same orientation as the half sails 82, 83 on the other side of the spar 85, for example.

[0062] Figure 13 shows a third specific embodiment of the sail assembly shown in Figure 9. For a given spar 85, the half sails 82, 83 on one side of the spar are asymmetrical with respect to, for example, the axis 95 from the half sails 82, 83 on the other side of the spar. In other words, the half sails 82, 83 on one side of the spar 85 have a different orientation than the half sails 82, 83 on the other side of the spar 85.

[0063] Figure 12 shows a fifth embodiment of a vessel 100, including a sail assembly 80 about a foremast 81 and a sail assembly 80 about a mizzen mast 81. In this Figure 12, the upstream half sail 83 is folded. Note that in strong winds, the upstream half sail 83 can be folded while maintaining wind load so that the vessel continues to move forward. Conversely, in light winds, the upstream half sail 83 can be deployed to maximize wind load.

[0064] 14 shows different points on the sail of a sixth particular embodiment of a vessel 105 equipped with a sail assembly 80. The orientation of the spars 85 of the upstream mast 81 may be different from the orientation of the spars of the downstream mast 81. Even if the spars 85 of the upstream mast 81 and the spars 85 of the downstream mast 81 have different orientations, the orientation of the half sails 82 and / or 83 of the upstream mast 81 may be the same as the orientation of the half sails 82 and / or 83 of the downstream mast 81.

[0065] The third embodiment of the sail assembly 80 that is the subject of the present invention has the following advantages: -Automatic retraction in all wind conditions; -Large surface area; -Limited clearance; -Has an efficient geometry when Rn is small; -Excellent durability in strong winds; -Small footprint on deck; - motorization of the rotation of the mast around the axis of rotation 25 and of the upstream half sail around the axis of the hinge 86, which can be easily automated; -It is sustainable.

[0066] Naturally, the mast 81 can also be replaced by two parallel masts jointly supporting a spar 85, as in the second embodiment of the sail assembly that is the subject of the present invention.

Claims

1. A biplane sail assembly (30, 40, 80) for a vessel (50, 60, 70, 90, 100, 105) having a deck (54, 94): - a mast (31, 38, 39, 81) extending along an axis (25) and mounted at an angle to the deck of the vessel on an electric shaft having an axis of rotation at an angle to the deck of the vessel; - a number of spars (35, 85) installed on either side of the mast and inclined relative to the mast; - for each side of the mast, a sail (32, 33, 82, 83) between the ends of two consecutive spars located on the same side of the mast, and motorized means (87) for unfurling and folding the sail; A biplane sail assembly (30, 40, 80) comprising:

2. 2. A sail assembly (30, 40) according to claim 1, comprising a yard (34, 36) at each end of each spar, each yard extending along an axis (26, 28) perpendicular to the axis (25) of the mast, each sail (32, 33) being flexible and mounted between two parallel yards, the yards on either side of the mast being parallel to each other.

3. 3. A sail assembly (30, 40) according to claim 2, wherein the axis (26, 28) of the yard (34, 36) on one side of the mast (31, 38, 39) is parallel to the axis (26, 28) of the yard (34, 36) on the other side of the mast.

4. 3. A sail assembly (30, 40) according to claim 2, wherein the axis (26, 28) of the yard (34, 36) on one side of the mast (31, 38, 39) intersects the axis (26, 28) of the yard (34, 36) on the other side of the mast.

5. A sail assembly (30, 40) according to any one of claims 2 to 4, comprising, for each of the flexible sails (32, 33), a retaining line (37) between the yards (34, 36) surrounding the sail, the line being positioned on the windward side of the yards, and the motorised means for unfurling and folding the sails comprises a furler for the sail, consisting of a cylindrical tube rotating around a fixed cable, the sail being connected to the furler by a bolt rope passing through a channel in the furler.

6. A sail assembly (30, 40) according to any one of claims 2 to 5, comprising two parallel masts (38, 39) jointly supporting the spar (35).

7. 7. A sail assembly (80) according to any one of claims 1 to 6, wherein at least one said sail comprises a rigid upstream half-sail (83) and a rigid downstream half-sail (82) connected together by a hinge (86) located between the two ends of successive said spars (85).

8. 8. A sail assembly (80) as set forth in claim 7, wherein the half sails (82, 83) on one side of a given spar (85) have the same orientation as the half sails (82, 83) on the other side of the spar (85).

9. 8. A sail assembly (80) as set forth in claim 7, wherein the half sails (82, 83) on one side of a given spar (85) have a different orientation than the half sails (82, 83) on the other side of the spar (85).

10. A sail assembly (80) according to any one of claims 7 to 9, wherein each half sail (82, 83) is a parabolic arc.

11. A sail assembly (80) according to any one of claims 7 to 10, wherein the motorised means (87) for deploying and folding the sail comprises an actuator.

12. 12. A sail assembly (80) according to any one of claims 7 to 11, comprising means for controlling the motorisation means for unfurling and folding the upstream half-sail (83) relative to the downstream half-sail (82), the control means being configured to fold the half-sails on top of each other when tacking and gybing and to reverse curves between starboard and port tacks.

13. A watercraft (50, 60, 70, 90, 100, 105) comprising at least one sail assembly (30, 40, 80) according to any one of claims 1 to 12.

14. A watercraft (50, 70, 100) according to claim 13, comprising a sail assembly (30, 40, 80) according to any one of claims 1 to 12 around a foremast (31, 81) and a sail assembly (30, 40, 80) according to any one of claims 1 to 12 around a mizzen mast (31, 38, 39, 81).

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