Patent Description:
The study of the forces generated on a boat by the interaction of sail and wind and of drift, hull and rudder with water is very complex.

To understand the problem, here it is stated only that even if generating also lift forces, drift and rudder act almost exclusively by resistance. In particular, while sailing between abeam and close-hauled, the drift avoids an excessive leeway of the boat.

Besides leeway it is also needed to avoid heeling, to allow to increase the sail area exposed to the wind (and so the "useful" force).

To such aim, the evolution of sailing race boats has been oriented to the so called "form stability", given by the resistance that the hull itself opposes to heeling. Therefore, ever larger and flatter monohulls have been realized, and also catamarans and trimarans.

For the same reason, keels have become separated elements from the hull, they have become longer, and their weight has been brought on the bottom, concentrated in a lead bulb. The advantage of this solution is that the hull is far from the center of gravity of the keel and the consequent increase of the righting force exerted.

It is also known the usage of oscillating drifts, thanks to which while sailing abeam and close-hauled the mass (bulb) provided on the bottom of the drift can be displaced windward, thus increasing the righting moment.

However, this causes a problem: by taking a more horizontal position, the drift loses its function of contrasting leeway while sailing close-hauled. For this reason, in some boats as for example IMOCA or Mini <NUM> "dagger boards" have been introduced", which are additional, slightly tilted drifts, which add the contrast factor to transverse forces which is lost with oscillating keel.

In addition to the just described elements, it is also known the usage of "foils". With "foil" it is indicated a specific type of appendage, not present in the "traditional" boats, configured to generate: an upward hydrodynamic thrust in order to lighten the boat and so to contrast friction, and a righting force in order to increase the sail area which can be exposed to the wind.

In some conditions, the upward thrust makes the sailing boats "fly" (meaning that the sailing boat proceeds with the hull lifted from water) so that water friction is reduced noticeably. Yet, there is still the water friction with the foils themselves, which is however very much lower than the one with the hull.

Boats known at the state of the art, which use foils.

After the general introduction, various examples of sailing boats using foils known at the state of the art are described, among which the following types are distinguished:.

For completeness, it is also to be stated that other boats exist which are provided with foils, as for example flying inshore catamarans and many projects of drifts in addition to the first flying drift, the Moth.

While developing these boats, the first goal was to try to increase the righting force. In addition to the oscillating kill a horizontal hydrodynamic profile was added on leeward, configured to generate an upward thrust, thus contributing to contrast the capsizing force exerted by the wind. This side retractable "blade" foil was introduced on boats as Wild Oats XI, winner of Sidney Hobart. The next development was to give an "L" shape (also said whisker) to the foils, present for example on "Figaro <NUM>", provided also with oscillating keel. In this case, the horizontal portion of the foil has the role of "righting" the boat, the vertical portion has the role to recover the resistance to leeway lost after oscillating the keel.

However, the America's Cup catamarans were the first ones to sail totally lifted from water. To reach this aim, they were provided with inverted T o L shaped foils.

So, they had a vertical portion aiming at contrasting leeway and a horizontal portion aiming at lifting the hull. To improve the multihull balancing it was also provided another T shaped foil on each rudder.

Referring again to monohulls instead, currently two main types exist: on the one hand totally "flying" boats, as those of America's Cup <NUM>, and on the other hand boats (Mini <NUM>, IMOCA) which never sail totally lifted from water.

The first ones are configured for protected and flat waters and fly at a distance from water, but the design solutions adopted for these boats will never satisfy the safety and stability criteria required for oceanic classes. In fact, America's Cup sailing boats with foil rely on the same foils for their capacity to remain right; if, accidentally a foil goes out water for a wrong maneuver, the boat lays down and is not able to set oneself upright anymore. The Mini <NUM> and IMOCA classes require instead a positive righting force in case of <NUM> degrees angle of heeling.

Also, <CIT> discloses a sailing boat comprising two oscillating foils. And <CIT> discloses a motor boat with two oscillating foils which can be nested along the hull.

The performances and the speeds obtained with sailing boats provided with foils are impressive comparing only to just few years ago. Comparing to past boats, today a well-done project using foils is surely faster than displacement boats.

In the embodiments known at the state of the art, anyway, still some drawbacks exist limiting the application of foils to very expensive and complex boats, and which in some cases limit their use strongly only to certain wind conditions.

Firstly, it is observed that, with low wind, when the speed is not sufficient to make the boat plane or fly, the immersed appendages provided in the various shown configurations, slow down the boat, since their friction is added and not substituted to the one of the hull.

Moreover, the impact with the waves is reduced in comparison to the traditional boats, but only until the wave becomes too high. Finally, the use of foils shows limits both with low wind (typically under <NUM> knots, i.e. approximately <NUM>/s) and strong wind (over <NUM> knots; i.e. approximately over <NUM>/s) and formed wave.

Moreover, the great number and the excessive dimensions of the immersed appendages make their widespread use impossible, both for the complexity of their control and the excessive dimensions in mooring step.

Finally, with reference to safety requirements, many of these boats are not provided with self-righting capacities.

Therefore, aim of the present invention is to provide a hull for sailing boats which overcomes the just described drawbacks.

More in particular, aim of the present invention is to provide a hull for sailing boats provided with a stability and lift control system which allows both traditional and planar sailing or "flying".

Moreover, the hull according to the present invention is provided with a stability and lift control system which allows a safe use also in condition of strong wind and formed wave, and which has self-righting capacities.

Finally, the present invention provides a hull for sailing boats provided with a stability and lift control system which reaches all the just described aims, and whose realization and use are less complex than the embodiments known at the state of the art.

The invention realizes the prefixed aims since it is a boat comprising at least two oscillating hydrodynamic profiles or foils (<NUM>, <NUM>), symmetrical to the longitudinal middle axis of the hull (<NUM>) of said boat and hinged in their upper portion, one for each body side, to the topside of said hull (<NUM>) so that they can rotate moving away and close to said hull (<NUM>), characterized in that each of said foil (<NUM>, <NUM>) comprises fastening means (<NUM>) positioned at their upper end, by means of which the foil is hinged to the body side of said hull; a first portion (<NUM>) having such shape that it can approach the body side of the boat adhering to the same along its whole development; a second portion (<NUM>), whose hydrodynamic profile is configured to exert a lift thrust after the boat proceeds in water, said second portion (<NUM>) being configured to be vertically positioned when said first portion (<NUM>) is approached to the shape of the hull and in that said hull (<NUM>) and said foils (<NUM>, <NUM>) can take: a first rest configuration in which said foils (<NUM>, <NUM>) have their first portions (<NUM>) approached to the shape of the hull, and their second portions (<NUM>) vertically positioned at the middle of the hull and under it; a second configuration in which said second portions (<NUM>) are substantially horizontal; any intermediate configuration between these two.

Firstly, it is to be said that, regardless of the type of the hull shown as a way of example in the appended images, the stability and lift control system according to the invention can be applied to any type of light displacement boat.

As it is shown in <FIG>, the hull (<NUM>) according to the present invention comprises a double oscillating keel functioning as foil (<NUM>, <NUM>). The two profiles (<NUM>, <NUM>) constituting the double oscillating keel are symmetrical to the longitudinal middle axis of the boat, and are hinged in their upper portion, one for each body side, to the topside of the hull so that they can rotate moving away and close to the hull. Preferably, the two foils (<NUM>, <NUM>) are hinged at the height of the washboard, so to use the whole height of the hull and to maximize the distance at which the profiles, when open, are arranged, as detailed in the following.

Even if not shown in the appended figures, the hull comprises also a system of actuators configured to make each of said foils (<NUM>, <NUM>) rotate around the axis (<NUM>) of the hinged fastening by means of which they are fastened to the hull, so that each of said foil (<NUM>, <NUM>) can take anyone of the positions comprised between the maximum opening position (<FIG>) and the rest position (<FIG>).

Each of said foils (<NUM>, <NUM>) is characterized in that it comprises:.

It is to be specified that with "to replicate the shape of the hull" it is intended that the shape of the first portion (<NUM>) of each hydrodynamic profile (<NUM>, <NUM>) is such that it can approach the body side of the boat adhering to the same along its whole development.

Preferably, but not limitingly, the second portion is divided in two portions (<NUM>, <NUM>) tilted to each other by an angle (α).

Said second portion (<NUM>) is configured to be substantially vertical when the foils (<NUM>, <NUM>) are in rest configuration, with the first portion (<NUM>) of the foil (<NUM>, <NUM>) adhering and overlapping the body side of the hull.

In this way, the hull (<NUM>) and the foils (<NUM>, <NUM>) can take:.

Moreover, preferably, in the terminal portion of each foil a ballast can be introduced, for example in lead, to guarantee the possibility of self-righting of the hull, according to what explained better in the following.

Yet, it is to be specified that at the rotation axis (<NUM>) the foil comprises preferably inserts in metal material (<NUM>), introduced in the realization step inside the profile in composite material, integral with the foil and connected to rotation shafts (<NUM>) which, in turn, are controlled by suitable movement and control means of the hydrodynamic profiles.

In fact, it is to be specified that the boat according to the present invention is conveniently provided with electronic control means, configured to control the movement of the hydrodynamic profiles and their coupling angle as well.

With reference to the appended <FIG>, it is to be specified that the section (<NUM>) of said second portion can take any shape of hydrodynamic profile configured to generate lift (flat/convex, concave/convex or bi-convex) as a function of the results of the fluid-dynamic computation carried out for each specific project.

Moreover, preferably, said second portion (<NUM>) is configured so that it can rotate so to change its coupling angle and is provided with means for adjusting the coupling angle.

What shown graphically in the appended figures is to be intended as a way of pure example not limiting the effective structural embodiment of the fastening means.

It is also to be specified that the positioning of the foils (<NUM>, <NUM>) on the longitudinal axis of the boat will depend on the project of the single hull, and what shown in the appended figures is to be intended as example and not limiting.

Moreover, preferably the hull (<NUM>) of the boat comprises, on the outer surface of each body side, a housing seat (<NUM>) for the foils (<NUM>, <NUM>), so that when the foils are in their "rest" configuration, with the first portion adhering to the hull of the boat, there is no discontinuity in the outer profile opposed to water.

It is clear that, as it is shown in detail A of <FIG>, when the foil (<NUM>) is open, the profile of the boat is not perfectly hydrodynamic.

Anyway, in that case, as it is shown in <FIG>, the boat is lifted and is "flying" or "planing" and so the friction with water is not considered as a problem.

It is to be specified that the hull comprises also a rudder (<NUM>) provided with hydrodynamic profiles for adjusting the longitudinal trim, and even if not shown in the appended figures, it can comprise also a drift, possibly of bayonet type.

After explaining the configuration of the main elements of a boat, it is now possible to explain its functioning in the various configurations provided.

This "resting" trim, shown in <FIG>, <FIG> and <FIG>, allows to obtain great technical advantages which allow to overcome the most of the problems highlighted concerning the boats known at the state of the art.

In this configuration, in fact, the boat is completely similar to a traditional drift, and in case of too low or too strong wind the boat can behave exactly as a traditional boat.

The force scheme shown in <FIG> indicates in fact that in this configuration the hydrodynamic forces on the two profiles cancel each other, and only the resultant downwards of the ballast possibly provided remains.

Moreover, in this configuration, the boat can be moored, with great stability as well, without additional inserts comparing to the ones of a traditional boat.

As it is shown in <FIG>, in the configuration with open keels, the lift force exerted by both the hydrodynamic profiles (<NUM>, <NUM>) will be directed in vertical direction, thus lightening the boat up to make it plane or "fly" as a function of the reached speed.

In this configuration, shown in <FIG>, the hydrodynamic forces exerted by the two hydrodynamic profiles, in the balance to rotation, give a net contribution opposing to the moment exerted by the wind on the sail.

Claim 1:
Boat comprising at least two oscillating hydrodynamic profiles or foils (<NUM>, <NUM>), symmetrical to the longitudinal middle axis of the hull (<NUM>) of said boat and hinged in their upper portion, one for each body side, to the topside of said hull (<NUM>) so that they can rotate moving away and close to said hull (<NUM>), whereby
each of said foil (<NUM>, <NUM>) comprises:
- fastening means (<NUM>) positioned at their upper end, by means of which the foil is hinged to the body side of said hull;
and characterized in that each of said foil (<NUM>, <NUM>) further comprises:
- a first portion (<NUM>) having such shape that it can approach the body side of the boat adhering to the same along its whole development;
- a second portion (<NUM>), whose hydrodynamic profile is configured to exert a lift thrust after the boat proceeds in water, said second portion (<NUM>) being configured to be vertically positioned when said first portion (<NUM>) is approached to the shape of the hull,
and in that said hull (<NUM>) and said foils (<NUM>, <NUM>) can take:
- a first rest configuration in which said foils (<NUM>, <NUM>) have their first portions (<NUM>) approached to the shape of the hull, and their second portions (<NUM>) vertically positioned at the middle of the hull and under it;
- a second configuration in which said second portions (<NUM>) are substantially horizontal;
- any intermediate configuration between these two.