FIELD OF THE INVENTION

[0001] The present invention relates to a stabilizer system for damping the movement, primarily the rolling, of vessels that are stationary or that are travelling at low speed and, in particular, to a system of this type that, when inactive, does not interrupt the continuity of the vessel hull surface.

BACKGROUND OF THE INVENTION

[0002] In the case of a vessel that is stationary or that is travelling at low speed, the rolling movement generated by the sea's transverse component causes great inconvenience for the vessel's occupants and restricts anchoring areas in the case of passenger and recreational craft. In the case of working vessels, such as fishing boats, oceanographic vessels, and hospital and military ships, a marked rolling movement in many cases reduces operational capabilities and safety.

[0003] To prevent these drawbacks, stabilization systems have been developed for vessels with the aim primarily of minimizing the rolling effect. Systems of this type known to the applicant include the following:

[0004] Bilge keels: these constitute the most primitive and simplest system and consist of two surfaces fixed to the vessel's bilge that are usually aligned with the current lines and limit the rolling movement by offering resistance to the oscillating movement of the vessel in a direction transverse to its length. They are an economic but only moderately effective solution and constitute an increase in resistance to the forward movement of the vessel by forming an increase in the careen.

[0005] Dynamic stabilizers: those that can be termed “fixed” generally consist of fins with a hydrodynamic cross section that project from the vessel's sides, below the water line. Usually actuated by electrohydraulic means in order to generate a rotational movement about a geometric axis perpendicular to the surface of the hull, they are controlled by signals emitted by devices that detect the rolling movement of the vessel. The direction of the torque generated by the hydrodynamic lift of said fins is the opposite of that of the vessel's rolling movement and therefore the latter is damped. A dynamic stabilizer system has been developed for low speed or for a stationary vessel, based on the sudden rotary movement of the stabilizer fins. In addition to offering resistance to forward movement, this method has limitations arising from the small damping effect of the fin and also constitutes an increase in resistance under the vessel's normal conditions of operation.

[0006] As it is necessary for the water to strike the profile at a specific velocity for the fin to fulfil its stabilizing function, this type of dynamic stabilizer is effective only when the vessel is moving, and its configuration and arrangement on the hull are usually calculated to have maximum efficiency at cruising speed with small wavelets.

[0007] This is an effective system, but its technical complexity results in a high financial cost. In addition, as in the case of bilge keels, its installation means an increase in the careen and therefore they offer resistance to forward movement in all conditions.

[0008] To overcome this drawback of dynamic stabilizers, retractable dynamic stabilizers have been developed that are housed in the vessel's hull when not in use, but said housing obviously takes space away from inside the hull, their operation, for the rest, being identical to that of the fixed dynamic stabilizers mentioned above.

[0009] Antirolling tanks: known also as “water chambers”, they are usually placed on both sides of the vessel and intercommunicate via a system of tubes and valves. Their function is to damp rolling under all conditions by means of the transfer of fluid from one side of the vessel to the other, thereby creating a righting torque that opposes the rolling movement of the vessel. This is an effective system, although limited in its application, but its installation involves a high level of complexity, takes volume away from inside the hull and also results in a loss of stability torque in certain circumstances.

[0010] Finned cones: this system consists in suspending, from one or both sides of the vessel, a body of substantially conical or frustoconical shape that is closed via its smaller base, that is usually made of metal and provided with hinged fins on its surface and a weight suspended from its lower part. When the vessel lists towards the side from which the device is suspended, the fins open such that, through the action of weight, the body remains submerged. When the list is to the opposite side, the drag of the water over the surface of the cone opposes the movement. This is a simple, effective system that can be used only when the vessel is stationary. Nevertheless, its installation and operation are awkward, requiring the use of a crane or auxiliary davit.

SUMMARY OF THE INVENTION

[0011] The object of the present invention is to provide a stabilizer system that is simple and reliable in operation, capable of efficiently reducing the rolling of a vessel that is stationary or that is travelling at low speed without its incorporation adding resistance to forward movement, i.e. without its affecting the speed of the vessel when the system is inactive, in accordance with the characterizing part of claim 1.

[0012] The object of this invention is achieved by incorporating, on both sides of the boat, an element substantially like a fin that can adopt a first, active or deployed, position, in which it has a surface sufficient to damp, to the appropriate extent, the rolling of the vessel when the latter is stationary or travelling at low speed, and a second, inactive or non-deployed, position, in which it may be placed by virtue of being hinged by means of a hinge integral with the hull and in which it forms with the latter a surface with no interruption of continuity.

[0013] In said first, active or deployed, condition, the damping effect on rolling is achieved directly by virtue of the high hydrodynamic resistance of said element to the component of the flow normal to its surface area.

[0014] When said stabilizer element is in its aforesaid second, non-deployed, position, with its outer surface flush with the surface of the hull, its resistance to forward movement is practically zero.

[0015] Both the active surface of the abovementioned stabilizer element and its location on the hull, and the number of said stabilizer elements installed on each side, will suit the shapes of the hull and take into account the transverse stability parameters of the vessel.

[0016] Thanks to the incorporation of the stabilization system according to the invention, the following advantages are achieved:

[0017] optimization of the damping effect when the vessel is stationary or travelling at low speed, maximum effectiveness being achieved as compared with other systems;

[0018] simple operation;

[0019] it has no effect on resistance to forward movement;

[0020] it does not require dynamic functioning of the stabilizer elements (although the invention also covers this possibility);

[0021] its incorporation into a hull has a very small effect on the interior space, which allows easy installation both in newly constructed vessels and those already in existence;

[0022] as it does not constitute an element that affects the speed of the vessel, it affords the possibility of installing, in certain cases, a number of integral stabilizers in different regions of the hull in order to limit rolling, heaving and pitching movements;

[0023] it requires a marked increase in the amount of energy necessary for the vessel to reach severe angles of list, which constitutes an increase in safety when sea conditions are poor.

[0024] The above and other characteristics and advantages of the invention will become apparent to an expert in the art from reading the following detailed description of the preferred embodiments of the present invention taken together with the attached drawings.