The present invention relates in a general way to the field of sailing.

As is known, in the context of sailing the term "head" denotes the part of the sail terminating at the upper vertex of a triangular sail. The halyard for hoisting the sail is fastened to this vertex.

It is also known that, in boats with triangular sails, such as sloops, the air flows circulating around the head are turbulent, thus increasing the aerodynamic drag and thereby reducing the overall efficiency of the sail.

One object of the present invention is to overcome or at least mitigate the problems of turbulence associated with the air flows at the head, and thus improve the aerodynamic efficiency of the sail.

In view of these objects, the invention proposes a triangular sail for a vessel, comprising an upper end sail portion connected to the remaining part of the sail through a hinge extending in the direction of air flow with respect to the sail, said upper end sail portion thereby being movable in a laterally swivelling manner with respect to the remaining part of the sail.

In a sail according to the present invention, the "head", as it is known, is therefore made to be capable of swivelling by means of a hinge with respect to the remaining part of the sail, and is therefore adjustable by means of a control device such as a pulley having corresponding running rigging which is taken to the deck of the boat.

This is because it has been found that, by inclining the head laterally, particularly downwind with respect to the wind direction for close-hauled sailing, the interaction of the head with the air flows can be adjusted, improving its aerodynamic efficiency and thus improving the overall efficiency of the sail.

The present invention can be applied to sails made of flexible material and also to wing- sails, such as those used on boats competing in the America's Cup races.

Specific embodiments are described in the dependent claims, the content of which is to be considered as an integral part of the present description.

Other characteristics and advantages of the invention will be apparent from the following detailed description, which is given purely by way of non-limiting example, with reference to the attached drawings, in which:

Figure 1 is a simplified representation showing a right-hand side view of part of the rig of a boat;

Figure 2 is a simplified representation showing a perspective view of part of the rig of the boat of Figure 1 ; and

Figure 3 is a simplified representation showing a stern view of the boat of Figure 1.

The drawings show, for illustrative purposes but in a non-limiting way, a boat with a Marconi sloop rig. The boat comprises a principal sail of triangular shape, conventionally called a "mainsail" and indicated as a whole by the number 10 in the figures. The number 20 indicates a spar to which the forward edge 1 1 of the sail 10 is secured, while 30 indicates a boom to which a lower aft corner of the sail l O ^' is secured. The spatial terms used in the present description refer to the normal condition in which the sail is used.

The term "triangular" is not intended to mean that the sail must have an exactly triangular shape; in fact, it may have a shape which is only approximately triangular. In any case, the sail must be configured so as to have a vertical edge (or "luff) secured or capable of being secured to a spar.

In the example shown in the figures, the sail 10 is of flexible material; it may conventionally comprise a stiffening/supporting headboard 40 fixed to the sail 10 in the upper part (or "head") thereof. The headboard 40 is conventionally fastened to a cable or rope 50, called a "halyard" and provided for hoisting the sail.

The sail 10 comprises an upper end sail portion 60, which is connected to the remaining part of the sail 10 through a hinge 70 extending in the direction of the air flow with respect to the sail 10, indicated by the arrow F in Figure 1, that is to say in a direction which is substantially horizontal in use.

The hinge 70 is positioned between a lower end of the upper end sail portion 60 and an upper end of the remaining part of the sail 10, and interconnects these.

The hinge 70 may be formed by a single extended hinge element, or may be formed by a series of hinge units positioned along the direction of extension of the hinge. Possible examples of construction for the hinge include hinges of the type formed by a pair of leaves joined by a pin, or film hinges.

The upper end sail portion 60 is therefore movable in a laterally swivelling way with respect to the remaining part of the sail 10. For this purpose, a rotary control device 80 such as a pulley, is provided, and is positioned at an end of the hinge 70 for controlling the rotation of the upper end sail portion 60 with respect to the remaining part of the sail 10. The rotary control device 80 has an axis of rotation parallel to the direction of extension of the hinge 70; the stiffening/supporting element 61 of the upper end sail portion 60 is positioned so as to be rotationally fixed to the rotary control device 80. A cable or rope 81 (or "running rigging") is associated with the rotary control device 80 and is taken to the deck of the boat for controlling the rotation of the upper end sail portion 60. On the opposite sides of the sail 10 there are positioned guide members 82, for example rings, for guiding respective lengths of the running rigging is such a way that it does not interfere with other sheets of the boat.

Part of the hinge 70 and the rotary control device are supported by the stiffening/supporting headboard 40.

Since the halyard 50 is fastened to the sail 10 at the top of the part of the sail below the hinge 70, the upper end sail portion 60 must have a separate arrangement to enable it to remain in the unfurled condition; for this purpose, provision may be made for the upper end sail portion 60 to include a stiffening/supporting element 61, such as a batten, posi- tioned at a vertical edge of this portion.

A system (not shown) is also provided to ensure the return of the upper end sail portion 60 to the position of alignment with the rest of the sail 10, when the cable or rope 81 is not actuated by the crew operating the rigging.

With the arrangement described above, the inclination of the upper end sail portion 60 with respect to the sail 10 can be adjusted by acting on the cable or rope 81 connected to the control device 80. This inclination can be adjusted in either direction, depending on whether the sailing boat is sailing on the starboard or port tack. Figure 3 shows that the upper end portion 60 is not in alignment with the remaining part of the sail, but is inclined laterally.

A specific embodiment of the invention has been described here; as will be evident to a person skilled in the art, innumerable variants and modifications of what has been described (in terms of shape, dimensions, arrangements and parts with equivalent functions, for example) may be devised without departure from the scope of the invention as shown in the attached claims. In particular, the invention may equally well be applied to a sail of the wingsail type.