The sail of the invention is manufactured according to a traditional technique, by joining together a fan-shaped series of suitably-shaped flat panels, in such a way that their ordered combination results in a large single piece having the shape and three-dimensional profile of a sail, with a concave side, capable of capturing the wind, and a convex side.

In modern sails, panels no longer consist in simple pieces of cloth. They are made of laminated fabrics that include several overlapped layers of thin sheets of flexible and impermeable material, with an intermediate bearing layer made of multiple threads that must support the entire load withstood by the sail when the sail is subjected to the strength of the wind.

To that end, the threads are laid along the direction of the lines of force that can be foreseen based on the dimensional, geometrical and aerodynamic characteristics of the sail.

The European patent EP 0249427 discloses a sail of this type, made up of multiple panels joined together, with each panel being formed of at least two non-bearing layers with an intermediate laminated bearing layer made up of a fan-shaped series of threads in non-parallel position.

The aforementioned European patent states that the location of each panel with respect to the entire surface of the sail must be taken into consideration in order to orient the threads according to the direction of the lines of force in the portion of the sail where the panel is located.

For example, in the case of a jib, in the three panels located in the cap, clew

and tack of the sail, the individual threads diverge in a radial way from the three angles, knowing that the lines of force converge in the three angles.

Vice versa, in the intermediate panels that join the highest panel (cap) and the two lowest panels (clew and tack, respectively), the individual threads are laid one next to each other in non-parallel position, oriented towards the direction in which the lines of force go across the intermediate panels.

The largest inconvenience during the construction of sails made up of multiple laminated panels is represented by the difficulties encountered in providing uniform tension to the diverging bundle of threads that are usually subjected to pre-load in order to increase the sail resistance.

Uniformity is extremely important for the sail to obtain a correct aerodynamic three-dimensional profile and guarantee correct resistance values.

The purpose of the invention is to devise a new construction method for three-dimensional sails made up of multiple flat laminated panels, capable of facilitating the uniform tensioning of all threads of the bearing layer of each laminated panel.

Another purpose of the invention is to devise a new construction method for three-dimensional sails made up of multiple flat laminated panels, which provides for the realisation of reinforced areas in the panel, in which overlapped threads create a grid capable of locally increasing the resistance of the laminated panels.

A further purpose of the invention is to devise a new construction method for three-dimensional sails made up of multiple flat laminated panels, which provides a variety of options in terms of location, extension and density of the areas reinforced by means of a grid of overlapped threads.

The aforementioned primary and secondary purposes are achieved by the construction method of the invention, which is based on the realisation of the bearing layer by means of multiple bundles of parallel threads, where each bundle is tilted with respect to the adjacent bundle, being provided that the bundles of threads near the external borders of the sail are oriented in parallel direction to the borders.

In other words, it can be said that the bearing layer is made with a fan-

shaped series of bundles of parallel threads that are overlapped with higher density and larger surface near the rotation centre of the fan-shaped series of bundles of parallel threads.

It appears evident that the location, extension and density of the areas reinforced by means of a grid of overlapped threads can be varied as desired, choosing from time to time-according to the geometrical shape and characteristics of the sail-the number of threads for each bundle and/or the distance between the threads in each bundle and/or the inclination angle between two adjacent bundles of parallel threads.

For major clarity the description of the invention continues with reference to the enclosed drawings, which are intended for purposes of illustration and not in a limiting sense, whereby: - Fig. 1 is a view of a typical jib, in which load lines are diagrammatically shown; - Figs. 2 to 5 shows four different steps in the lamination process of the clew panel ; - Figs. 6 to 8 show three clew panels with a different structure of bundles of parallel threads; - Figs. 9 to 11 show four different steps in the lamination process of the intermediate panel of the sail ; With reference to Fig. 1, the method of the invention is used to manufacture a jib or Genoa type of sail (V), by dividing the entire surface of the sail into five different panels (1,2, 3,4 and 5), i. e.: - cap (1) - tack (2) - clew (3) - two intermediate panels (4 and 5) With reference to Figs. 2 to 5, the description continues with the realisation of the clew (3) according to the construction method of the invention.

First of all, it must be noted that each panel is made up of at least two external layers of thin flexible impermeable material, between which an intermediate bearing layer made up of multiple threads is glued.

The first external layer (3a) is laid over a working surface used to perform the entire lamination process of the clew (3).

As shown in Fig. 2, the first bundle of parallel threads (F1) is laid along the entry (E) of the sail (V) in parallel direction, while the second bundle of parallel threads (F2) is laid along the base (B) of the sail (V) in parallel position, in such a way that a crossing and overlapping area (Z) is created between the two bundles (F1 and F2) in the clew angle.

The area (Z) is the rotation centre for the next fan-shaped series of bundles of parallel threads (F3, F4,... Fn).

Once the fan-shaped series of bundles of parallel threads has been completed, the lamination process of the clew (3) is performed by laying and gluing a second external layer over the fan-shaped series of parallel threads.

Fig. 6 shows that by changing the inclination angle between two adjacent bundles of parallel threads, it is possible to choose the number (nO, n2, n3, n4) of threads that cross over on the borders (L) of the clew (3) sewn to the adjacent panels.

Fig. 7 shows that, by choosing a suitable inclination angle, the distance between the intersection area of the bundles of parallel threads and the borders (L) of the clew (3) sewn to the adjacent panels can be changed as desired.

Fig. 8 shows a clew (3) made of bundles of parallel threads with different width and density at different inclination angles. Fig. 8 shows the large number of possible combinations and variants provided by the construction method of the invention.

With reference to Fig. 8, it must be noted that the reinforcement of the angle with highest stress is automatically carried out when laying down the different bundles of parallel threads, whose superimposition indirectly generates reinforced areas that, according to traditional construction methods, require the oriented application of laminated inserts that must be fixed to the sail in such a way that the thread warp is perpendicular to the thread warp in the area to be reinforced.

The cap (1) and tack (2) are obviously realised with the same constructive

modes as the clew (3).

With reference to Figs. 9 to 11, the description continues with the realisation of the intermediate panel of the sail (4) according to the construction method of the invention.

As mentioned above, the first external layer (4a) is laid over a working surface used to perform the entire lamination process of the intermediate panel (4).

As shown in Fig. 9, the first bundle of parallel threads (F10) is laid along the entry (E) of the sail (S) in parallel direction, while the second bundle of parallel threads (F20) is laid along the leech (BA) of the sail (V) in parallel position, knowing that the lines of force near the entry (E) and leech (BA) are basically parallel to the borders of the sail (V).

Additional intermediate bundles of parallel threads are then laid to reinforce the entire surface of the sail included between the two external bundles (F10 and F20), by inclining each intermediate bundle with respect to the immediately preceding bundle, in such a way that each bundle of parallel threads is given the same orientation as the lines of force in the portion of the sail where the bundle of threads which is being applied has to be laid.

In this case, reference can be indifferently made to one or more rotation centres for the fan-shaped series of bundles of parallel threads.

For instance, the intermediate panel (4) of Fig. 11 has a fan-shaped series of bundles of parallel threads that originate from different imaginary rotation centres located outside of the panel.

Once the fan-shaped series of bundles of parallel threads has been completed, the lamination process of the intermediate panel (4) is performed by laying and gluing a second external layer over the fan-shaped series of threads.

Finally, attention is drawn on the fact that the characteristic of the construction method of the invention, that is to say the capability of facilitating uniform tensioning of all threads of the bearing layer of the sail, originates from the presence of bundles of parallel threads with desired pre-load value by means of simple extensible support frames.

For illustrative purposes only, it must be noted that the two external layers of each laminated panel can be made of polyester or polypropylene film, while the intermediate bearing layer made of a fan-shaped series of bundles of parallel threads may be made of polyester, aramidic fibres and carbon yarns.