WO2012010948A1

WO2012010948A1 - Foresail, rigging therefor and boat comprising said rigging

Info

Publication number: WO2012010948A1
Application number: PCT/IB2011/001667
Authority: WO
Inventors: Fiorenzo Bertan; Diego Ersetig
Original assignee: Fiorenzo Bertan; Diego Ersetig
Priority date: 2010-07-19
Filing date: 2011-07-19
Publication date: 2012-01-26
Also published as: IT1402236B1; ITUD20100144A1

Abstract

A foresail able to be hoisted autonomously forward of the mast of a boat (30) is of a shape substantially assimilable to quadrangular and has four tops respectively defining four angles (α, β, γ, δ) of which a tack angle (a), a first head angle (β), a second head angle (γ) and a clew angle (δ), and four sides, respectively foot or base (14, 1 14) of the sail, comprised between the tack angle (a) and the clew angle (δ), forward leech (16, 1 16) comprised between the tack angle (a) and the first head angle (β), stern leech (18, 1 18) comprised between the clew angle (δ) and the second head angle (γ) and an upper base (20, 120), comprised between the first head angle (β) and the second head angle (γ), and disposed in an opposite position and having a length which is less than the foot, or base (14, 1 14) of the sail.

Description

FORESAIL, RIGGING THEREFOR AND BOAT COMPRISING SAID RIGGING

FIELD OF THE INVENTION

The present invention concerns a foresail, the sail structure for a foresail and the boat comprising said sail structure.

BACKGROUND OF THE INVENTION

It is known that modern sailing boats are the type with a Bermuda or Marconi sail. In particular, in sloop rig sailing boats a stern sail called spanker is normally provided, bent on the main mast, and a foresail, able to be raised forward of the mast. Typically, in sloop rig the foresail is the jib, or Genoa jib, bent on the forward stay, as can be seen in the drawing (attached) showing the state of the art. Other foresails can be the gennaker, MPS and spinnaker, but normally these are not bent.

The shape of the jib, disregarding the slight curves of the sides that are necessary for an optimum practical use, is traditionally triangular and has three tops defining respectively three corners, that is, tack corner, head or peak corner and clew or sheet corner, and three edges, respectively foot or base of the sail, comprised between the tack corner and the clew corner; forward leech or luff, comprised between the tack corner and the head corner; and stern leech, or after leech, comprised between the clew corner and the head corner.

Currently, there is a growing tendency to increase the performance of sailing boats, for example for regattas and, since the sailing sector is extremely competitive and crowded, there is a growing need to make continuous improvements and perfections that can contribute to solve certain technical problems, so as to obtain competitive advantages and better performance.

If we consider the intensity of the wind in the open sea, we notice that the pressure is lower when one approaches the surface of the water, and increases as one gradually rises to a height of about 15 meters. This phenomenon is due to the turbulence of interference that slows down the wind near the surface of the sea.

From the studies done by Czeslaw A. Marchaj, it is known that in mid ocean, given a wind speed of 5.4 knots at 1.5 meters in height, at 15 meters in height the speed reaches about 8.7 knots, with an increase of about 60%. As happens on the surface of the sail or of any winged profile immersed in a stream, the wind too, in contact with the surface of the sea, generates a friction that slows down the free stream of air. The greater the height of the stream of air from the surface of the water, the greater and more constant its speed will be. Sail planes should therefore have the greatest possible surface near the peak of the mast, so as to exploit the greater intensity and constancy of the wind.

Consequently, to confirm this theory, from the view point of resistance induced, the worst shape for a sail is the triangle.

In modern designs for trysails for regatta boats, for some years now what is called the "randa top square" has been used - see US-A-4.461.231, which precisely provides a "randa top square". Using a trysail with an upper base which, in relation to the sizes of the sail, can go from 50/60 cm up to measurements of more than a meter, guarantees a considerable increase in the performance of the sail.

The "randa top square" is simple to make in that the forward part of the sail is bent to the mast and is therefore fixed. The lower base of the sail is then made by inserting supporting slats made of very light plastic material which allow to keep the geometric shape of the sail with any type of wind.

However, it is not possible to translate the concept of "randa top square" to make a foresail, since the aerodynamic effects induced are different and the use of the two sails is certainly different. Furthermore, foresails are not bent on the mast and therefore the structural and dynamic considerations valid for the trysail are not valid for foresails. A simple use forward of a "randa top square" with the structural system with slats would not be possible, since the force of the wind would bend the upper end of the sail, modifying the design geometries and inevitably worsening the general performance of the sail plan.

A trapezoidal sail is also known, held by an upper peak and a lower boom, as present in BE-A-884.950.

This sail is a variant, with smaller sizes, of the known "lateen" sail, which has always been widely used in the Mediterranean.

The front and rear part are interconnected to constitute a single sail with all the problems deriving therefrom in exploiting the wind, in terms of sailing upwind, stability and speed. Purpose of the present invention is to achieve a foresail, a sail structure for a foresail and a boat comprising said sail structure, which has better performance than traditional foresails, in particular compared with traditional triangular jibs.

The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claims, while the dependent claims describe other characteristics of the invention or variants to the main inventive idea.

In accordance with the above purpose, a foresail according to the present invention is able to be raised forward of the mast and is substantially like a quadrangle in shape and has four tops defining respectively four corners, that is, tack corner, first head corner, a second head corner and clew corner, and four sides, respectively foot or base of the sail, comprised between the tack corner and the clew corner; forward leech or luff, comprised between the tack corner and the first head corner; stern leech, or after leech, comprised between the clew corner and the second head corner, and an upper base, comprised between the first head corner and the second head corner and disposed in an opposite position and being shorter in length than the foot or base of the sail.

It is clear that the four sides of the sail, for all practical effects, are slightly arched, for example the after leech is slightly concave, while the other three sides are slightly convex or rounded, so as to adapt to the real conditions of use of the sail. Within the framework of the present invention, considering the shape of the sail as substantially similar to a quadrangle, the four sides are considered similar to linear segments that, converging, define tops.

In some forms of embodiment, the first head angle is acute.

In some forms of embodiment, the amplitude of the first head angle is comprised between about 60° and about 90°.

In some forms of embodiment, the second head angle is obtuse.

In some forms of embodiment, the amplitude of the second head angle is comprised between about 90° and about 120°.

In some forms of embodiment, the tack angle is acute, for example the amplitude is less than 90°, to about 45°.

In some forms of embodiment, the shape of the sail is substantially trapezoidal or similar to a trapezium. In this case, the foot or base of the sail is parallel to the upper base, or is in a condition of sub-parallelism, meaning an inclination of a few degrees, for example an inclination of less than about 30° with respect to the horizontal, for example about 12-15°.

In some forms of embodiment, the sail according to the present invention is a jib.

In some forms of embodiment, the sail according to the present invention is a Genoa sail.

Still other forms of embodiment provide that the sail according to the present invention is a gennaker.

According to some forms of embodiment of the present invention, the ratio between the length of the upper base of the sail and the length of the foot or base of the sail is comprised between about 1 : 1 1 and about 1 :3.

For example, if the foresail is a jib or Genoa, the ratio may be comprised between 1 :5 and 1 :3. If it is a gennaker, taking into account that the tack point will be after the bows, on the bowsprit, the ratio may be comprised between 1 : 1 1 and 1 :8.

According to some variant forms of embodiment, the length of the upper base of the sail is therefore chosen according to the type of boat and type of sail plan, taking into account the correlations in length with the foot or lower base.

For example, in some solutions of the present invention the upper base of the sail can have a length comprised between about 60 cm and about 80 cm.

In some forms of embodiment, the foresail according to the present invention is able to be bent on a stay constrained in the upper side to the mast and in the lower side to a point comprised between the mast and the bows, which may be a jib or a Genoa. Or, in other forms of embodiment, the sail according to the present invention can be a gennaker, mounted on a lower boom or bowsprit, properly calibrating its dimensional ratios according to the present inventive idea.

The present invention also concerns a sail structure for the foresail as above, comprising a mast having an oblong element or strut, which extends in length by a desired amount in a forward direction, that is, aligned with the direction of advance of the boat, facing toward the bows. The oblong element or strut is disposed at a desired height in substantial proximity to the head or peak of the mast, and the forward stay on which the forward leech of the foresail according to the present invention is bent is attached.

In this way, the strut displaces forward the attachment of the first head angle of the foresail, leaving the movement of the second head angle of the upper base free.

In some forms of embodiment, the strut is disposed at about 9/10 of the height of the mast.

In some forms of embodiment, the strut is positioned at the height of lateral crosstrees at the head of the mast, being substantially configured as a front crosstree.

According to some forms of embodiment of the present invention, the strut of the sail structure is connected with flying rigging to the main deck.

In some forms of embodiment, the angle between the strut and the axis of the mast is substantially about 90°. In this case, during normal use the strut is substantially horizontal.

In other forms of embodiment, the strut may be inclined upward or downward, according to needs and the choice of the construction materials.

It is known that lateral crosstrees and the head of the mast define a so-called diamond structure. The diamond structure defined by the present invention is totally innovative, providing the strut in a forward position as well.

The strut according to the present invention will be subjected to the forces transmitted from the upper peak point of the jib, tending to rotate in the direction of the wind.

In some cases, the presence of normal lateral crosstrees may in itself contrast this force. Or, in other cases, two adjustable flying crosstrees may be necessary, to connect the end of the upper lateral crosstrees present on the mast at the stern of the boat, and which tend to contrast these forces, allowing the sailor to manage the rotational force of the strut in the best possible way.

In some forms of embodiment, the stay on which the forward leech of the sail according to the present invention is bent is the forward stay.

In other forms of embodiment, the stay on which the forward leech of the sail according to the present invention is bent is not the forward stay but an auxiliary stay in an intermediate position between the mast and the bows.

In some variants of this form of embodiment, the auxiliary stay is constrained in an intermediate position between the mast that supports the sail structure and the bows, and the point of constraint is definable on each occasion so as to selectively vary the angular position of the auxiliary stay with respect to the axis of the boat.

In some variant forms of embodiment, the auxiliary stay is positionable angularly inclined with respect to the axis of the boat, and is mobile, being selectively fixed on each occasion at a desired point between the mast and the bows, so that the sailing axis may not coincide with the axis of the boat but may also be inclined to the right or left of the axis of the boat. The misaligned bending which can be obtained thus allows to arrange the boat better to the wind, particularly when sailing close-hauled.

In variant forms of embodiment, the auxiliary stay is constrained to a connection element mobile along a guide or rail, substantially transverse to the direction of advance of the boat, disposed on the main deck in an intermediate position between the mast that supports the sail structure according to the present invention and the bows. In this way it is possible to adjust the inclined position of the auxiliary stay with respect to the axis of the boat.

Furthermore, in other forms of embodiment, the stay on which the forward leech of the sail according to the present invention is bent is an auxiliary stay constrained beyond the bows, for example on a bowsprit.

In some forms of embodiment of the present invention, the length of the strut is correlated to the extension of the upper base of the foresail according to the present invention.

According to some forms of embodiment of the present invention, the extension in length of the strut is comprised between about 10 cm and about 150 cm, preferentially between 20 cm and 120 cm, more preferentially between 30 cm and 80 cm, also depending on the type of material chosen.

The inventive idea of the present invention allows to exploit the greater force of the wind and serves to bring the shape of the whole sail plan of the boat, consisting of the trysail and the jib, closer to the elliptical shape which in fact represents the best profile that can be achieved, as far as the ratio between lift and resistance is concerned.

The foresail according to the present invention can be used on all types of sailing craft by means of easy modifications to the mast and to the bows maneuvers. On boats fitted out with the sail structure of the new sail plan according to the present invention the rigging can be revised and adjusted since the greater sail surface of the upper part of the jib can modify the general design parameters of the boat.

The new sail plan according to the present invention tends to increase the performance of the boat, in particular when sailing close-hauled, and also increases the listing force. In this case, by increasing the surface or lift of the jib, the sail center is displaced higher and toward the bows, and consequently the boat becomes more leeward, tending to rotate the boat according to the direction of the wind.

Possible other adjustments may also include an increase in the ballast on the keel, to contrast the greater listing force induced by raising the sail center. On the other hand, using a randa top square entails similar interventions on the rigging of the boat because it displaces the sailing force applied toward the stern; the use of the foresail according to the present invention would at least partly balance the modification to the sail plan, possibly actuated with a randa top square.

According to the present invention, the mast of the sail structure in question can be a mainmast or a foremast or a mizzenmast.

The present invention also concerns a sailing boat comprising a sail structure for the foresail as described above, and also the foresail itself.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics of the present invention will become apparent from the following description of a preferential form of embodiment, given as a non-restrictive example with reference to the attached drawings wherein:

- fig. 1 is a perspective view of one form of embodiment of a sail and the relative sail structure associated with a sailing boat according to the present invention;

- fig. 2 is a perspective view of another form of embodiment of a variant of the sail and the relative sail structure in fig. 1 ; - fig. 3 is a lateral view of fig. 1 ;

- fig. 4 is a lateral view of fig. 2;

- fig. 5 is an enlarged detail of the sail structure in figs. 1 and 3;

- fig. 6 is an enlarged detail of the sail structure in figs. 2 and 4;

- fig. 7 is a detail of the tack point in figs. 1 and 2;

- fig. 8 is a detail of the tack point in figs. 2 and 4;

- fig. 9 is a comparative diagram of the linear sizes between a state-of-the-art sail and the sails in figs. 1, 3 and 2, 4;

- fig. 10 is a comparative diagram of the surface sizes between a state-of-the-art sail and the sails in figs. 1, 3 and 2, 4.

To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings.

It is understood that elements and characteristics of one form of embodiment can conveniently be incorporated into other forms of embodiment without further clarifications.

DETAILED DESCRIPTION OF A PREFERENTIAL FORM OF

EMBODIMENT

With reference to the attached drawings, figs. 1, 3, 5 and 7 show a first form of embodiment of a sail structure, indicated by the reference number 10, for a sailing boat 30, comprising a mast 22 which, in this case of a sloop rig, is a main mast.

In a traditional manner, the boat 30 in this case is rigged with a randa top square 1 1.

The sail structure 10 comprises a foresail 12, in this specific case a jib.

The foresail 12 according to the present invention has a shape substantially similar to a quadrangle and has four tops defining four angles α, β, γ, δ of which:

- a tack angle a,

- a first head angle β,

- a second head angle γ,

- and a clew angle δ.

The foresail 12 has four sides 14, 16, 18 and 20, respectively:

- foot or base 14 of the sail, comprised between the tack angle a and the clew angle δ, - forward leech or luff 16 comprised between the tack angle a and the first head angle β,

- stern leech or after leech 18 comprised between the clew angle δ and the second head angle γ, and

- an upper base 20, comprised between the first head angle β and the second head angle γ, disposed in an opposite position and having a shorter length than the foot or base 14 of the sail 12.

Consequently, unlike traditional triangular jibs, the forward leech 16 and the after leech 18 do not converge at a common top, but converge in two different tops from which the upper base 20 extends for a desired length L.

As can be seen in the attached drawings, the sides 14, 16, 18 and 20 of the sail 12 are slightly arched, however in the present description they are treated as linear segments.

In some forms of embodiment, the shape of the sail 12 is substantially like a trapezoid.

According to the present invention, the sail structure 10 comprises an oblong element or strut 26, disposed in this case substantially horizontal and facing toward the bows, on the mast 22 at a desired height in substantial correspondence with the head 24 of the mast 22, in this case at 9/10 of the height of the mast. The strut 26 extends, in this case forming an angle of about 90° with the main mast 22, but it could be inclined upward or downward according to other forms of embodiment, in length M by a desired amount in a forward direction. The stay 25 on which the forward leech or luff 16 of the sail 12 according to the present invention is bent is attached to the strut 26.

In the form of embodiment shown in figs. 1, 3, 5 and 7, the stay 25 on which the forward leech or luff 16 of the sail 12 according to the present invention is bent is the forward stay. In this way, the tack point of the sail 12 is to the bows, in this case fixed.

The sail structure 10 according to the present invention comprises upper lateral crosstrees 28 at the head 24 of the mast, in this case inclined, typically, astern. Preferentially, the strut 26 is disposed at the same height as the upper lateral crosstrees 28.

The strut 26, the lateral crosstrees 28 and the head 24 of the mast 22 define an innovative diamond-type structure according to the present invention.

According to some forms of embodiment of the present invention, the strut 26 is connected with lateral rigging, or in other embodiments with adjustable flying rigging, to the main deck.

In some forms of embodiment of the present invention, the length M of the strut 26 is correlated to the extension of the upper base 20 of the sail 12 according to the present invention.

Figs. 2, 4, 6 and 8 show a second form of embodiment of the sail structure according to the present invention, indicated by the reference number 1 10 and comprising a foresail 1 12, in this case a jib, with a shape substantially similar to a quadrangle and having tops that define identical four angles, that is, a tack angle, a first and second head angle and a clew angle, and four sides, a foot or base 1 14, forward leech or luff 1 16, stern leech or after leech 1 18 and upper base 120, opposite and having a shorter length than the foot 1 14.

The shape of the sail 1 12 is substantially the same as that of the sail 12 described above, but with different sizes, in particular with a smaller foot or base of the sail and hence a smaller surface, as shown better in the comparative examples.

In some forms of embodiment, the sail 1 12 is substantially similar to a trapezoid in shape.

Moreover, in the sail structure 1 10, the stay on which the forward leech or luff 1 16 of the sail 1 12 is bent is an auxiliary stay 125 constrained not directly to the bows, but between the mast 22 and the bows.

In this way, the tack point of the sail 1 12 is between the mast 22 and the bows. In some forms of embodiment, the point of constraint of the auxiliary stay 125 can be selectively defined on each occasion, depending on the sailing conditions and requirements, and it is thus possible to incline the sailing axis with respect to the axis of the boat 30.

In some forms of embodiment, the auxiliary stay 125 is tracked, that is, constrained to a connection element 31 (figs. 2, 6 and 8), for example a spring clip or cleat, mobile in a guided manner along a rail 32 substantially transverse to the direction of advance of the boat 30.

The rail 32 is disposed on the main deck in an intermediate position between the mast 22 that supports the sail structure 1 10 and the bows. In close hauling, in particular, this form of embodiment is advantageous because it allows to selectively vary the tack point, reducing the angle at which the wind hits.

As a consequence of the tack point being further back, the length of the lower base 1 14 has been correspondingly reduced, as mentioned above, with respect to the length of the lower base 14 of the form of embodiment 10. The following

Table

summarizes the ranges of angular amplitude in degrees of the three angles , β, γ (the clew angle δ is deduced, case by case, by the difference from 360°), the ratio R between the length L of the upper base 20 of the sail and the length of the foot 14, and the value of the length M (in centimeters) of the strut 26, in some forms of embodiment according to the present invention.

These ranges of values may be considered both for the first form of embodiment 10 and also for the second form of embodiment 1 10.

The value of the length L (in centimeters) of the upper base 20 can be found from the value R and the value of the length of the foot of the sail, which can vary on each occasion depending on the type of boat and the sail plan.

For example, if the foresail is a jib or a Genoa jib, there may be a ratio R comprised between 1 :5 and 1 :3.

For example, for a sail, like a jib, with a foot of 313 cm and an upper base of 70 cm, the value R is about 0.22. On the contrary, for a sail with a foot of 225 cm, again with an upper base of 70 cm, the value R is about 0.31.

In the case of a gennaker, considering that the tack point will be beyond the bows, on the bowsprit, it will be possible to have a ratio R comprised between 1 : 1 1 and 1 :8.

For example, in the case of a gennaker, with a bowsprit of about 270 cm and again considering an upper base of 70 cm and a foot of 583 cm, the value of R is about 0.12.

In some forms of embodiment, the length of the strut 26 is preferentially between 20 cm and 120 cm, still more preferentially between 30 cm and 80 cm, also depending on the type of material chosen to make it. In the comparative examples shown below, the state-of-the-art sail structure is called Jl , while the forms of embodiment 10, 1 10 of the sail structure according to the present invention are indicated respectively by J2 and J3.

COMPARATIVE EXAMPLES

The present invention was tested for experimental purposes on a prototype belonging to the class "MINI 650 proto", which are ideal boats, normally used also in solo ocean regattas like the Transat 6.50, on which to try out new solutions, also because they allow to considerably reduce the costs since these are boats which are only 6.50 meters long with a very limited weight. At the same time they are boats that have to overcome the demanding solo ocean crossing. They therefore represent an optimum field of application to try out technological and innovative solutions.

The tests involved making a complete three-dimensional model, a perfect copy of the real boat, on which the new foresail was virtually raised. Thanks to the availability of all the design data of the sails on the trial boat, the geometric shape and sizes were perfectly reproduced. This allowed us to have a perfect reference for comparison with the design sails.

The shape and rig of the boat were redesigned using Rhinoceros software, a powerful three-dimensional solid modeler.

When the model was complete, the file was imported into a specific modeling software, dedicated exclusively to the design of sails, opting for "SailPack", a powerful parametric software for the design and verification of sails, produced by BSG Developments.

The three-dimensional model was then imported into "SailPack" where the original sail plan and the two different types of trapezoid jib J2 and J3, achieved according to the present invention (forms of embodiment 10 and 1 10), were designed:

- Traditional jib (Jl):

The geometry of the original jib of the test boat was reproduced, inserting the parameters relating to the sizes of the sail (base, after leech and forward luff), to the percentage and position of the belly, or curve, and the head twist of the sail. The area of the jib Jl is 14.90 m2 (figs. 9 and 10).

- Trapeze jib (J2): Following the dimensional parameters of the original sail a jib was designed with a trapezoidal shape with the foot 14 or lower base of 313 centimeters (same measurement as the original jib Jl) and the upper base 20 of 70 centimeters. The jib is rigged conventionally in its lower base 14 with the tack point fixed in the bows and the sheet point adjustable from the cockpit. The peak point is tacked on the bow end of the strut 24 leaving the second top of the upper base 20 free. The surface of the sail thus advantageously increases to 18.47 m2 compared with the 14.90 m2 of the original jib, with an increase of about 23% (figs. 9 and 10). The increase in surface occurs only in the upper part of the sail where the intensity of the wind is greater and constant, thus obtaining an advantageous increase in performance.

- Trapeze jib on rail (J3):

The third jib was designed again following the dimensional parameters of the original boat and sail. This jib is trapezoidal in shape with an upper base 120 of 70 centimeters long (as in the case of J2), but the foot 1 14 or lower base is shorter, measuring only 225 centimeters (figs. 9 and 10). Indeed, as we said, the tack point of the jib has been moved back, as it has been positioned not fixed to the bows of the boat but on the rail 32 which allows the tack point to slide transversely.

This modification entails a slight reduction in the sail surface to 14.35 m2 (almost equivalent to the jib Jl which was 14.90 m2).

This second form of embodiment, compared with the original jib Jl, has an advantage in that the extension of the sail, although equivalent to that of the original jib, has an increase in surface in the upper part of the sail. Measuring the surface in the center line of the sail, the jib Jl has a surface of 3.94 m2 in the upper half and 10.96 in the lower half, whereas the sail J3 has an upper part of 5.57 m2 and a lower part of 8.78 m2.

If the wind at 15 meters above the sea is more constant and has a greater force by about 60%, the new shape and the different percentage distribution of the surfaces create an undoubted advantage in the performance of the new sail.

And there is also another advantage of the second form of embodiment, given by the possibility of displacing transversely the tack point of the jib with respect to the bows of the boat. In this way it is possible to sail up the wind, in close hauling, with a smaller angle at which the wind hits the sail, compared with a tack point traditionally fixed to the bows.

Claims

1. Foresail, able to be hoisted autonomously forward of the mast (22) of a boat (30) without being bent in the mast itself, wherein the tack angle cooperates with the bows of the boat and the clew angle cooperates with the sheet, characterized in that it is of a shape substantially assimilable to quadrangular and has four tops respectively defining four angles (α, β, γ, δ) of which a tack angle (a), a first head angle (β), a second head angle (γ) and a clew angle (δ), and four sides, respectively foot or base (14, 1 14) of the sail, comprised between the tack angle (a) and the clew angle (δ), forward leech or luff (16, 1 16) comprised between the tack angle (a) and the first head angle (β), stern leech or luff (18, 1 18) comprised between the clew angle (δ) and the second head angle (γ) and an upper base (20, 120), comprised between the first head angle (β) and the second head angle (γ), and disposed in an opposite position and having a length which is less than the foot, or base (14, 1 14) of the sail.

2. Sail as in claim 1, characterized in that the amplitude of the first head angle (β) is comprised between about 60° and about 90°.

3. Sail as in claim 1 or 2, characterized in that the amplitude of the second head angle (γ) is comprised between about 90° and about 120°.

4. Sail as in any claim hereinbefore, characterized in that the amplitude of the tack angle (a) is less than 90°, to about 45°.

5. Sail as in any claim hereinbefore, characterized in that the ratio (R) between the length (L) of the upper base (20, 120) of the sail and the length of the foot, or base (14, 1 14) of the sail, is comprised between about 1 : 1 1 and about 1 :3.

6. Sail as in any claim hereinbefore, characterized in that its shape is substantially trapezoidal.

7. Sail structure comprising a mast (22), characterized in that it comprises an oblong element or strut (26), which extends in length (M) from the mast (22) by a desired amount in a forward direction, which is disposed at a desired height in substantial proximity to the head or peak (24) of the mast (22), to which oblong element or strut (24) the stay (25, 125) is attached on which the forward leech or luff side of the foresail is bent.

8. Sail structure as in claim 7, characterized in that the length (M) of the oblong element or strut (26) is correlated to the extension of the upper base (20) of the foresail.

9. Sail structure as in claim 8, characterized in that the length (M) of the oblong element or strut (26) is comprised between about 10 cm and about 150 cm.

10. Sail structure as in claim 7, 8 or 9, characterized in that the foresail is like a foresail (12, 1 12) as in any of claims 1 to 6.

1 1. Sail structure as in any claim from 7 to 10, characterized in that the oblong element or strut (26) is disposed at about 9/10 of the height of the mast (22).

12. Sail structure as in any claim from 7 to 1 1, characterized in that the stay on which the forward leech of the foresail is bent is the fore stay (25).

13. Sail structure as in any claim from 7 to 1 1, characterized in that the stay on which the forward leech of the foresail is bent is an auxiliary stay (125) in an intermediate position between the mast (22) and the bows.

14. Sail structure as in claim 13, characterized in that the auxiliary stay (125) is constrained in an intermediate position between the mast (22) which supports said sail structure and the bows, the point of constraint being definable on each occasion in order to selectively vary the angular position of the auxiliary stay (125) with respect to the axis of the boat.

15. Sail structure as in claim 14, characterized in that the auxiliary stay (125) is constrained to a connecting element (31) mobile along a guide (32) substantially transverse to the direction of advance of the boat, disposed on the main deck in an intermediate position between the mast (22) which supports said sail structure and the bows.

16. Sailing boat comprising a foresail (12, 1 12) as in any claim from 1 to 6 and/or a sail structure (10, 1 10) as in any claim from 7 to 15.