FIELD OF THE DISCLOSED SUBJECT MATTER

The present invention refers to the technical field of leisure and commercial navigation with hydrofoil boats (i.e., a special type of boat which is fitted with hydrofoils).

More particularly, this invention discloses hydrofoils which can be employed in a conventional way during their operation condition and which, simultaneously, are capable of retraction when are not in use.

BACKGROUND OF THE INVENTION

Hydrofoils were invented by Forlanini more than 100 years ago.

These elements usually have at least one wing shaped portion and contrary to conventional boats which use mainly hydrostatic pressure to create buoyancy, hydrofoils exploit the hydrodynamic vertical lift created by said wing shaped portions in the water to counteract the weight of the boat.

Hydrofoils need a certain minimum speed (known as take off speed) to create the desired lift. Below the take off speed a conventional hull is needed. Above the take off speed the hull rises out of the water (a condition usually known as the “foiling mode”) with a great reduction of drag. In addition to the drag reduction, hydrofoils are interesting because of the lower accelerations induced by waves in seaway, which results in increased comfort and the low wash created (which result in a lower environmental impact).

One of the problems of hydrofoils is the stabilization of the flight (i.e., controllability during the foiling mode). While a hydrofoil can be easily designed to produce enough lift, the instantaneous request of lift is continuously changing because of the variability of the forces acting on the boat (change of speed, waves, wind, etc). In this respect, there are two main kinds of hydrofoils which are normally used, surface piercing and submerged. Surface piercing hydrofoils create stability thanks to their ability to passively change their immersed area with changes of immersion. Submerged hydrofoils have always the same area immersed, and the lift is controlled actively through changes of the angle of the whole wing or a part of it (flap) relative to the flow. There are also a variety of hybrids solutions.

Ideally the efficiency of a hydrofoil can be improved by increasing its span, reducing its area and increasing its immersion. From a practical point of view, some of these requirements are in conflict with each other and a compromise solution must normally be found. Even the number of hydrofoils to be mounted on a boat and their position, may vary significantly depending on the case and type of boat.

While normally hydrofoils are mounted in a fixed position, in some cases design requirements carry the need of having hydrofoils able to modify their relative position to the boat.

Thus, boats such as the AC75 (which took part in the last America’s Cup - 2021 ), are designed in such a way that two hydrofoils were able to cant independently (i.e., to rotate around a longitudinal axis), resulting in an increase of performance. Thus, the windward foil can be canted up to reduce the hydrodynamic drag and to increase the boats stability.

A similar approach was previously used on some classes of US Navy patrol boats. In this case the scope was the retraction of the foils out of the water when docking. In most cases the vertical retraction of the foils is commonly used for both sailing and power boats.

Nevertheless, there is still a need for a rotating system capable of taking the hydrofoils completely out of the water when not in use. This is an important requirement for any boat for maintenance and navigation in shallow waters; for instance, it is necessary to clean the entire surface of the hydrofoils in order to maintain its efficiency, since marine fouling rapidly degrades performances. Other situations in which it is also necessary to retract the hydrofoils are, for example, in shallow waters and ports with depth restrictions. In addition, most of the folding systems for hydrofoils which are already known in the art are heavy, bulky, complex (since they are formed by many different parts) and difficult to operate. Therefore, it would be advantageous to develop more compact systems capable of providing a high torsion moment to the rotating parts, which facilitates the folding and unfolding operations of the hydrofoils.

Usually, increasing the span of a hydrofoil leads to higher achievable efficiency. Nevertheless, it is difficult to manage said large span hydrofoils, especially when their span exceeds the beam of the boat. Additionally, having a foil span smaller than the maximum beam is often a requirement as when docking or to avoid obstacles, the foils tips must be protected and as a consequence within the beam of the vessel. Therefore, it would be advantageous to develop hydrofoils having a span bigger than the maximum beam of the boat during their unfolded condition and which are capable of folding up to a span which is smaller than the maximum beam of the boat.

To sum up, it is therefore necessary to develop systems which are not only capable of keeping the hydrofoils out of the water when not in use, but also to avoid excessive width at docking, while hydrofoils are in their folded condition.

Consequently, there is still a need for hydrofoils which are able to maximize efficiency and simultaneously solving problems of hoisting and retraction out of the water, while not in use.

DESCRIPTION OF THE INVENTION

The present invention is intended to address some of the problems and disadvantages of the prior art, mentioned above.

A first object of the present invention is a foldable hydrofoil for boats, provided with: a strut that comprises:

• an upper part connected to canting means;

• a lower part joined to a first portion of a nacelle;

- a nacelle comprising a first nacelle portion joined to the strut and a second nacelle portion joined to a wing;

- the canting means comprising a rotating portion located in the upper part of the strut connected to a fixed portion solidly joined to a hull of the boat;

- the wing joined to rotational means;

- the rotational means being arranged for reversibly rotating the wing between 0° and 90° with respect to the strut;

- - wherein the canting means are arranged for reversibly rotating the strut between a folded position, staying the wing outside of the water, and an unfolded position, staying the wing in contact with the water; wherein the angle of the strut, between the folded and the unfolded position, is comprised between 120° and 210°; wherein the strut is arranged for forming an angle between 60° and 90° with the horizontal direction, staying said strut in contact with the water during an unfolded condition; and wherein the rotational means are housed inside the strut, the wing and/or inside the nacelle.

Thus, the strut of the foldable hydrofoils, according to the present invention, is arranged to rotate between two end positions:

- a first end position, corresponding to an unfolded condition, wherein the strut is disposed substantially vertically (i.e., forming an angle between 60 and 90° with the horizontal direction) and in contact with the water. In this position, the wing can be disposed substantially horizontally (i.e., forming an angle between 60 and 90° with the vertical) and also in contact with the water. This position is usually employed during the normal foiling condition of the boat;

- a second end position, corresponding to a folded condition. To reach this position, from the first end position, the canting means are operated so they rotate the strut by 120° to 210° degrees until it reaches a substantially vertical position outside the water. The wing is outside of the water in this second position, and can be disposed substantially vertically (i.e., forming an angle between 0° and 30° with the vertical).

Therefore, the rotational means can be operated to rotate the wing from 0° to 90° degrees with respect the strut regardless of the position of the strut. In the second end position of the strut, the total width of the hydrofoil can be greatly reduced (since the wings can be disposed vertically to reduce their beam) and the hydrofoil can stay completely of the water. Consequently, this position is particularly advantageous for docking the boat and performing maintenance operations.

As already anticipated, thanks to the foldable hydrofoils according to the present invention, it is possible to maximize efficiency and simultaneously solve the problems of encumbrance and retraction out of the water while the hydrofoils are not in use.

In the folded condition, having the wing disposed substantially vertically, the total width of the hydrofoil is able to be kept within the maximum width of the boat, since the wing is disposed vertically, so this allows the use of wings having a bigger span than those used in the prior art. Moreover, foldable hydrofoils according to the present invention stay completely out of the water while they are in their (fully) folded condition.

Due to their specific design, the foldable hydrofoils of the present invention are capable of providing a high torsion moment to the rotating parts, which facilitates the folding and unfolding operations.

Furthermore, in the foldable hydrofoils of the present invention the parts of the rotational means are disposed inside the strut, wing and/or nacelle which makes them more compact and reliable to operate (since the risk of becoming entangled is significantly reduced).

In a preferred embodiment of the present invention, the rotational means comprises a rod located inside the strut, wherein said rod comprises a linear screw located in a lower extreme part of said rod, and a rotating gear which is engaged to the linear screw, wherein said rotating gear is solidly joined to the wing. In a preferred embodiment, the rotating gear is located inside the wing.

Thus, the linear movement of the linear screw can impart a rotation to the rotating gear and therefore to the wing, since the rotating gear and the wing are solidly joined to each other.

In a different embodiment of the present invention, the rotational means comprises a bevel gear, to transfer the rotation of the rod to the wing. In this embodiment, a rod is located inside the strut, and said rod comprises a first bevel gear located in a lower extreme part of said rod. A second bevel gear is solidly joined to the wing, and is engaged to the first bevel gear.

Alternatively, the rotational means can comprise other mechanism able to transform a linear motion of the rod into a rotation of the gear, or a system to transform a rotation motion of the rod into another rotation motion of the gear, shifted from a certain distance.

For example:

- the rod can comprise a lower extreme part attached to a hinge pin configured to push on a crank;

- the rotations means can comprise a cylinder or a piston configured to slide inside the strut, pushing a rod attached to hinge pin pushing on a crank; or

- the rotations means can comprise a slider cylinder inside the strut pushing directly on a crank.

The wing is preferably provided with adjustment means, configured to adjust the angle of attack of the wing relative to the water flow. On the other hand, the wing can be optionally fitted with flaps. Adjustment means preferably comprise a rotation shaft connected to a lever which is activated by a hydraulic cylinder, but other embodiments are possible to adjust the angle of the wing, such as a linear actuator.

In addition, the rotating gear or the second bevel gear is preferably located inside the nacelle, and said nacelle also comprises a fairing, which improves the hydrodynamics behavior of the wing.

Therefore, both the first nacelle portion (joined to the strut) and the second nacelle portion (joined to the wing), can be shaped in the form of a bulb, which is hydrodynamically efficient.

A second object of the present invention is a boat comprising at least one foldable hydrofoil as those described above.

Preferably, the boat comprises two foldable hydrofoils each one attached to one side of the hull of the boat. The present invention also contemplates a boat comprising three (or more) foldable hydrofoils.

On the other hand, one embodiment of the present invention contemplates a boat provided with two hulls joined together (for example a catamaran), said boat being also provided with four foldable hydrofoils, each hydrofoil being attached to one side of one of the hulls.

More preferably, the span of the wings of the foldable hydrofoils is such that the total width of the foldable hydrofoils exceeds the beam of the hull of the boat.

BRIEF DESCRIPTION OF THE FIGURES

To complete the present description and with the aim of a better understanding of the characteristics of the invention, this description is provided with a series of drawings constituting an integral part of the same, which show, for purely illustrative purposes and by no means limitation, the following:

Fig. 1 shows a schematic perspective view of a first embodiment of a foldable hydrofoil according to the present invention;

Fig. 2 is an exploded schematic perspective view of the foldable hydrofoil of Fig.1 ;

Fig. 3A shows a detail, at enlarged scale, of some of the elements of the foldable hydrofoil shown in fig. 2, wherein the rotational means comprises a rod that comprises a linear screw located in a lower extreme part of said rod, and a rotating gear which is engaged to the linear screw;

Fig. 3B shows a detail, at enlarged scale, of some of the elements of the foldable hydrofoil wherein the rotational means comprises a rod that comprises a first bevel gear located in a lower extreme part of said rod and a second bevel gear which is engaged to the first bevel gear.

Fig. 4A is a schematic perspective view of a boat provided with two of the foldable hydrofoils of Fig.1 , said hydrofoils being in their unfolded condition;

Fig. 4B is a schematic perspective view of the boat of Fig 4a, with the hydrofoils in a folded condition, wherein the wings are disposed substantially horizontally;

Fig. 4C is a schematic perspective view of the boat of Fig 4a, with the hydrofoils in the folded condition, wherein the wings are disposed substantially vertically; and

Fig. 5 is a schematic perspective view of a boat provided with two foldable hydrofoils, wherein the struts of said hydrofoils are forming an angle about 60° with the horizontal and the wings are forming an angle about 90° with the struts, being the hydrofoils in an unfolded condition.

Fig 6A: is a schematic front view of a boat showed in Figure 5, wherein the struts of said hydrofoils are forming an angle about 60° with the horizontal and the wings are forming an angle about 90° with the struts, being said struts of the hydrofoils in an unfolded condition.

Fig 6B: is a schematic front view of a boat, wherein the struts of the hydrofoils are forming an angle about 60° with the horizontal and the wings are forming an angle different to 90° with the struts, being said struts of the hydrofoils in an unfolded condition.

Fig. 6C is a schematic front view of a boat according to the present invention, with the hydrofoils in the folded condition, wherein the wings are disposed substantially vertically, so the hydrofoils can be stored within the maximum beam of the boat.

NUMERICAL REFERENCES IN THE FIGURES

A list of the different elements that form part of the present invention and are represented in the figures, as well as the corresponding numerical references that have been designated to them, is provided below:

1 Strut;

2 Wing;

3, 3a Canting means;

3 Rotating portion (of the canting means);

3a Fixed portion (of the canting means);

4, 4a, 4b, 5, 5a Rotational means;

4 Rod (of the rotational means);

4a Linear screw of the rod;

4b First bevel gear

5 Rotating gear (of the rotational means);

5a Second bevel gear;

6 Rotation shaft (of the adjustment means);

7 Lever (of the adjustment means);

8, 8a, 8b Nacelle;

8 First nacelle portion joined to the strut;

8a Second nacelle portion connected to the wing;

8b Nacelle fairing;

9 Hull (of the boat);

H Horizontal direction;

V Vertical direction;

It also should be taken into account that expressions such as “upper part”, “lower part” and the like, describe the arrangement of the corresponding elements when the hydrofoil is in its unfolded condition shown, for example, in Fig. 1 , Fig 4A, 5, and Fig. 6A.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

A detailed description of several examples of preferred embodiments of the present invention is provided below with the aid of the attached Figures 1 to 6.

Throughout the present description, as well as in the attached figures, the elements with the same or similar functions will be designated with the same numerical references.

Figs. 1 , 2 and 3A show a first embodiment of a foldable hydrofoil according to the present invention.

Said foldable hydrofoil comprises a hollow strut (1 ) which, in this particular embodiment of the invention is arranged for forming an angle of almost 90° with the horizontal direction during its unfolded condition (that is, to stay substantially vertical).

It also comprises a wing (2) which, in this particular embodiment of the invention, are arranged for forming an angle of almost 90° with the vertical direction during its unfolded condition (that is, to stay substantially horizontal).

The upper part of the strut (1 ) is connected to canting means (3, 3a), which comprises a rotating portion (3) located in the upper part of the strut (1) and a fixed portion (3a) solidly joined to the hull (9) of the boat. In this particular embodiment, the canting means (3, 3a) are arranged for reversibly rotating the strut (1) approximately 180° until the strut (1 ) reaches a folded condition outside the water.

In the preferred embodiment of the invention, the wing (2) is connected to rotational means (4, 4a, 5a) which comprises a rod (4) provided with a linear screw (4a), at its lower extreme, and a rotating gear (5a) which is engaged to the linear screw (4a). The wing (2) is solidly joined to a rotating gear (5) so the rotational means (4, 4a, 5) are arranged for reversibly rotating the wing (2) approximately 90° with respect to the strut (1 ).

Alternatively, other embodiment of the invention showed in figure 3B, the rotational means (4, 4b, 5a) can comprise a bevel gear (4b, 5a), to transfer the rotation of the rod (4) to the wing (2). In this embodiment, a rod (4) is located inside the strut (1 ), and said rod (4) comprises a first bevel gear (4b) located in a lower extreme part of said rod (4). A second bevel gear (5a) is solidly joined to the wing (2), and is engaged to the first bevel gear (4b). In addition, in this embodiment of the invention, the foldable hydrofoil comprises a nacelle provided with a first nacelle portion (8) joined to the strut, a second nacelle portion (8a) joined to the wing and a fairing (8b). Moreover, the nacelle portion (8a) houses the adjustment means (6, 7) including a rotation shaft (6) connected to a lever (7) which is activated by a hydraulic cylinder or linear actuator in order to adjust the angle of attack of the wing (2) relative to the water flow.

Fig. 4A shows a boat provided with two of the foldable hydrofoils of Figure 1 . The struts (1 ) of the said hydrofoils are in their unfolded condition, in which -as it can be clearly seen in Fig 4a- struts (1) are disposed substantially parallel to the vertical direction (V), while wings (2) are disposed substantially parallel to the horizontal direction (H).

Fig. 4B is a schematic perspective view of a boat, in which the struts (1) of the hydrofoils are in their folded condition. As it can be clearly seen the struts (1 ) have been rotated approximately 180° degrees by the canting means (3, 3a) until they have reached a substantially vertical position outside the water. The wings (2) are, in turn, also outside the water, but still disposed substantially horizontally.

Fig. 4C is a schematic perspective view of a boat, in which the struts (1) of the hydrofoils are in the folded condition and the wings (2) are now in their folded condition and are disposed vertically.

Fig. 5 is a schematic perspective view of a boat provided with two foldable hydrofoils of the present invention. In this embodiment of the invention, the struts (1 ) of the hydrofoils are in their unfolded condition, but said struts (1) are no longer parallel to the vertical direction (V). Similarly, the wings (2) describe an angle of approximately 30° with the horizontal direction (H). This embodiment of the invention is particularly suitable for sailing boats.

Figure 6A shows a front view of the boat shown in Figure 5 with the wings (2) forming an angle of 90° with the struts (1 ). Figure 6B shows a boat with two foldable hydrofoils wherein the struts (1 ) of said hydrofoils are in their unfolded condition but they are not in a vertical position and the wings (2) are forming an angle different to 90 degrees with the struts (1 ). Figure 6C shows a front view of the boat showed in Figure 5, with the hydrofoil fully folded and stored within the maximum beam of the boat. The present invention is in no way limited to the embodiments herein disclosed. For a person skilled in the art, other possible different embodiments will be evident in light of the present description. As a result, the scope of protection of the present invention is exclusively defined by the following set of claims.