WO2010122526A1

WO2010122526A1 - System and method for stabilization of a boat

Info

Publication number: WO2010122526A1
Application number: PCT/IB2010/051794
Authority: WO
Inventors: Roberto Rossi; Michele Sferrazza
Original assignee: Rodriquez Marine System Srl
Priority date: 2009-04-23
Filing date: 2010-04-23
Publication date: 2010-10-28
Also published as: ITMI20090692A1; IT1397067B1

Abstract

The present invention refers to a stabilization system (20) for a boat (10) having a roll axis X. The system (20) comprises a detecting device (140) suitable for detecting at least one parameter associated to the motion of the boat (10) with respect to the roll axis X; a control unit (130), suitable for processing the at least one parameter provided by the detecting device (140); and at least one water jet unit (30). Such a water jet unit (30) is able to generate, on the basis of the data received from the control unit (130), a water jet that causes a force whose moment, calculated with respect to the roll axis X, opposes the roll motion Mr of the boat (10). The invention also concerns a method for dynamic stabilization of a boat (10) by using such a system (20).

Description

"System and method for stabilization of a boat"

Description

The present invention concerns a system and a method for stabilization of a boat, in particular a system and a method for stabilization having the function of reducing the roll of an anchored boat, i.e. when said boat is not in navigation.

Roll is the oscillation of a land, sea or air vehicle around a longitudinal axis.

In the specific case of a boat, it consists of a complete low-frequency oscillation of the boat around an instantaneous rotation axis; such an axis, arranged on the plane of symmetry, can be considered to be barycentric. By complete oscillation we mean the angular movement carried out by the boat to go from one inclined position to the opposite one and go back to the initial one.

The main roll depends on wave motion, the size of the boat and its shape.

Any person located on a rolling boat has a complex system of forces acting upon them. As a result of such forces their coordination skills may be affected and the symptoms of seasickness may occur, characterized by paleness in the face and difficulty breathing. Seasickness may be accompanied by nausea and vomiting.

The present invention • refers in particular to a system and method for dynamic stabilization having the function of reducing the roll of an anchored boat, i.e. with the boat stopped or, put another way, when it is not in navigation.

Various means for stabilization of an anchored boat are known.

Gyrostat means exploit the principle of the gyroscope, according to which a rotating physical device, through the effect of the law of conservation of angular momentum, tends to keep its rotation axis oriented in a fixed direction. If a force is applied to the rotation axis of the gyroscope to change its direction, it tends to arrange itself along the direction perpendicular to the plane defined by the force applied and by the axis itself; the latter is set in motion describing an ideal cone. The movement, known as precessional motion, is caused by the combined action of the force applied and the angular momentum of the rotating body. In the specific case of boats, through gyrostat systems the rolling moment is transformed into a pitching moment. This translates into greater stability of the boat since the moment of inertia of the boat, calculated with respect to the transversal axis, is greater than the moment of inertia calculated with respect to the longitudinal axis. Generally, the gyrostat system is arranged at the midships section of the boat, where by midships section we mean the transversal section that encloses the maximum immersed area. The gyrostat, fixedly connected to the hull in a suitable manner, is rotated at a high speed about its own vertical axis by an electric motor. The constraints ensure that, with the exception of axial rotation, any movement of the gyrostat is transferred directly to the hull; any transversal moment to which the gyrostat is subjected transforms through gyrostatic precession into a moment rotated by 90° degrees, for which reason the roll moment is transformed into a pitching moment.

Alongside the category of gyrostats described above, classifiable as passive, in recent years "active" gyrostat systems have also been developed. In so-called passive systems, indeed, only with substantial roll oscillations is there an appreciable reaction of the gyroscopic effect. In "active" gyroscope systems, on the other hand, the gyroscopic precession is forced: the pitching moment is no longer induced by the roll moment of the hull but is forced by suitable actuator systems. The gyrostat, following stress received around the pitching axis, produces a roll moment that opposes the roll moment induced by the wave motion. These systems have some drawbacks. A first drawback is represented by their bulk.

Even if the most recent devices are characterized by smaller sizes, their installation inside a boat, particularly small and medium-sized ones, is not easy due to the large spaces required for installation. Another drawback is represented by their weight. The presence of heavy and concentrated loads means than the hull of the boat is subjected to high torsional strain during the roll and pitching movement with the consequent risk of deformation of the hull itself.

Other known anchored stabilization means are active stabilizer fins, similar to the ones used for stabilization during navigation. One or more pairs of fins are positioned at the sides of the hull to generate a hydrodynamic thrust that opposes the roll motion. The motion of the fins is controlled by suitable software that is able to determine the period, speed, acceleration and angle of the oscillations of the boat, and to synchronize the movement of the fins with the motion of the boat.

The motion of the fins must be wide and instantaneous in order to be able to damp the acceleration that the mass of the hull undergoes with the wave when the hull is anchored. The effectiveness of fins is directly influenced by their geometry since every geometry is associated with a certain lift coefficient.

Lift is also influenced by the size of the fins. In general, the greater the surface of the stabilizing blades, the more effective they are. This requirement, however, must be mediated with design restrictions deriving from reduction in bulk and reduction in friction. Large fins, indeed, could on the one hand jeopardize the handling of the boat and on the other hand it could disturb its navigation.

The purpose of the present invention is therefore to overcome the drawback of the prior art. In particular, a task of the present invention is to provide a system and a method for dynamic stabilization having the function of reducing the roll of an anchored boat, in other words when it is not in navigation.

The purpose and the task indicated above are accomplished by a dynamic stabilization system according to claim 1 and by a method for dynamic stabilization in accordance with what is claimed in claim 11.

The characteristics and the further advantages of the invention shall become clear from the following description of some example embodiments, given for indicating and not limiting purposes with reference to the attached drawings, in which: - figure 1 represents a schematic view of the system according to the invention;

- figure 2 schematically represents a plan view of the system according to the invention;

- figure 3 represents a schematic view of another embodiment of the system according to the invention;

- figure 4 represents a schematic view of a further embodiment of the system according to the invention;

- figure 5 schematically represents a side view of an element of the system according to the invention; - figure 6 schematically represents a front view of the element of figure 5;

- figure 7 schematically represents a view from above of the element of figure 5;

- figure 8 represents a schematic view of the element of figure 5, positioned inside a boat, in operating condition; - figure 9 represents a schematic view of the element of figure 5, positioned inside a boat, in rest condition; - figure 10 schematically represents a boat, highlighting an absolute reference system and a reference system fixedly connected to the boat;

- figure 11 schematically represents a cross section of a boat in which a generic roll angle is highlighted; - figure 12 represents a schematic view of a boat tilted with respect to the plane of the water following the action of a roll moment;

- figure 13 represents a schematic view of a boat tilted with respect to the plane of the water following the action of a roll moment opposite to what is depicted in figure 12; - figure 14 schematically represents the functional connection between the components of the system according to the invention.

The present invention refers to a stabilization system 20 for a boat 10 having a roll axis X. The system 20 comprises a detecting device 140 suitable for detecting at least one parameter associated to the motion of the boat 10 with respect to the roll axis X; a control unit 130, suitable for processing the at least one parameter provided by the detecting device 140; and at least one water jet unit 30. Such a water jet unit 30 is able to generate, on the basis of the data received from the control unit 130, a water jet that causes a force whose moment, calculated with respect to the roll axis X, opposes the roll moment of the boat 10. In the description of the system 20 and of its individual components that is made hereafter, the terms bow and stern respectively indicate the front a rear part of a boat. The front part of the boat is the part that parts the surface of the water in its forward motion, the rear part is the part situated at the opposite end to the front part. It can also be considered that the boat is symmetrical with respect to a longitudinal plane perpendicular to the plane of calm water, where by longitudinal we mean a direction that extends in the direction of the length of the boat, from bow to stern. Such a plane of symmetry is indicated with XZ; the axis X is positive if facing towards the bow of the boat and the axis Z is positive if facing upwards. Hereafter the axis X will be indicated as roll axis and the roll motion will be defined by the rotation of the plane XZ about the axis X- In the absence of wave motion and of forces acting upon the boat, the plane XZ coincides with the plane XZ that is presumed fixed and perpendicular to the plane of calm water.

The amount of rotation of the boat about the roll axis X will be identified through the angle 9 between the plane XZ and the plane XZ. Moreover, the references upstream and downstream should be taken with respect to the entry 42 of the system 20 (which will be described in detail later on): upstream will identify a position relatively close to the entry 42, downstream will identify a position relatively far from the entry 42, along the path defined for the water by the system 20.

In the following description, the references clockwise and anti-clockwise should be taken with respect to the roll axis X, assuming the point of view of a hypothetical observer who is located at the bow of the boat facing towards the stern.

With reference to the attached figures, the water jet system 30 can be made up of a suction assembly 40, a pumping assembly 50, a forced flow duct 60, two adjustment groups, 70 and 90, and two stabilization groups, 110 and 120. The suction assembly 40 can comprise an entry 42, positioned generally at the central keelson.

Through such an entry 42, the stabilization system 20 is placed in fluid communication with the outside of the boat 10.

Downstream of the entry 42, there can be a first rectilinear suction duct 44. Such a duct 44 is parallel to the axis Z, and has the task of conveying into the system 20 the sea water flowing through the entry 42. Downstream of the first suction duct 44 there can be a second suction duct 46 that, with reference to the attached figures, consists of a first rectilinear section 47 parallel to the axis Z, an elbow section 48 and a second rectilinear section 49 perpendicular to the plane of symmetry XZ. The first suction duct 44 and the second suction duct 46 are connected together in a per se known way, for example through bolted flanges. The second suction duct 46 has the task of conveying the water received from the duct 44 towards the pumping assembly 50.

The pumping assembly 50 can be made up of a standard centrifugal pump 52 and of the relative actuation motor 54.

In the attached figures, a single-stage centrifugal pump 52 with suction in the direction perpendicular to the plane XZ and delivery in the direction parallel to the axis Z. The pump is generally mounted at the mid-section of the boat and can be used, when it does not actuate the system 20, as a pump for normal services.

The actuation motor 54 is generally an electric motor. Pump 52 and motor 54 are arranged on a base plate 56, usually made from steel, which can be equipped with anti-vibration and antishock resilient mountings (not shown in the attached figures).

Downstream of the pumping assembly 50 there can be the forced flow duct 60.

Such a duct has the task of conveying the water exiting from the pumping assembly

60 towards the two adjustment groups 70 and 90.

Connected to the pump 52 in a per se known way, for example through bolted flanges, it can consist of a first rectilinear section 62, parallel to the axis Z, a union tee, 64, and two rectilinear sections, 66 and 68, perpendicular to the plane XZ and that extend in two opposite directions.

Through such a union tee, 64, the water sucked in by the pump 52 is divided into two distinct water flows of equal flow rate, which are directed in the direction perpendicular to the roll plane XZ towards the two sides of the boat 10. A first water flow is conveyed, through the duct 66, towards the adjustment group 70, a second water flow is conveyed, through the duct 68, towards the adjustment group 90. Figures 3 and 4 represent two further embodiments of the water jet system 30, each characterized by the presence, between the duct 60 and the pumping assembly 50, of a rectilinear duct 61 parallel to the axis Z. The length of such a section 61 is defined at the design stage of the system 30. On the one hand, the introduction of such a duct 61 increases the load losses within the system 30, and on the other hand it allows the lever arm of the stabilizing force generated by the system itself to be increased. A greater lever arm, for the same stabilizing moment M_s, requires the generation of a lower stabilizing force F_s and consequently allows a smaller pump to be installed.

The adjustment group 70, with reference to the attached figures, consists of a first duct 72 that extends in the direction perpendicular to the plane XZ. Such a duct consists of a first rectilinear section 74, a divergent section 76 and a second rectilinear section 78. The definition at the design stage of the diameter of the second rectilinear section 78 must be carried out by balancing two opposing requirements. Indeed, if on the one hand, by increasing the diameter of the duct 78 the risk of a water hammer occurring inside the duct itself is reduced, on the other hand, the greater the diameter, the greater the bulk of the device. Downstream of the duct 72 there is a rectilinear duct 80, with constant diameter, which extends in the direction perpendicular to the plane XZ- Such a duct 80, joined in a per se known way, for example through bolted flanges, to the duct 70, has the task of conveying the water received from the forced flow duct 60 towards the flow adjustment device 82. Such a device 82 adjusts the flow rate of the water that flows outside of the adjustment group 70. It can pass from an all-open configuration, in which the flow of water proceeds substantially undisturbed towards the devices that are located downstream, to an all-closed configuration, in which the flow of water is completely intercepted by the adjustment device, and vice versa. Intermediate configurations are also permitted that allow the flow rate of the water to be partialised, according to requirements. The number of such configurations depends on the degree of precision of the adjustment device itself. With reference to the embodiment illustrated in the attached figures, the adjustment device 82 consists of a butterfly valve.

Such a valve can be actuated by an actuator device 83, for example an actuator with a pneumatic cylinder. A potentiometer 85 can be mounted on the shaft of the valve, which has the task of detecting the degree of opening of the valve itself.

Downstream of the adjustment device 82 there is a rectilinear duct 84 perpendicular to the plane of symmetry XZ.

Such a duct has the task of conveying the water that has flowed through the adjustment device 82 towards the duct 86.

Such a duct 86, joined in a per se known way to the duct 84, for example through bolted flanges, can consist of a first rectilinear section 87, a convergent section 88 and a second rectilinear section 89.

The definition at the design stage of the diameter of the second rectilinear section 89 must be carried out by optimizing two different requirements, thrust and load losses.

Consequently, by decreasing the diameter of the second rectilinear section 89, for the same flow rate, the exit speed of the jet is increased but a higher load loss is also recorded.

The adjustment group 90 is located, with reference to the plane of symmetry XZ of the boat 10, on the opposite side with respect to the side occupied by the adjustment group 70. In an analogous way to the adjustment group 70, the adjustment group 90 consists of a first duct 92 that extends in the direction perpendicular to the plane XZ.

Such a duct consists of a first rectilinear section 94, a divergent section 96 and a second rectilinear section 98. In a per se known way, the duct 92 has a rectilinear duct 100, with constant diameter, connected to it that extends in the direction perpendicular to the axis XZ.

Downstream of the rectilinear duct 92, there is an adjustment device 102 analogous to the device 82 and actuated by the actuator device 103. A potentiometer 105 has the task of detecting the degree of opening of the adjustment device 102. The device 102 is connected to the duct 104. Downstream of the duct 104 there is the duct 106 that consists in an analogous way to the duct 96, of first rectilinear section

107, a convergent section 108 and a second rectilinear section 109.

Downstream of the adjustment groups 70 and 90, there are the stabilization assemblies 110 and 120, respectively. The stabilization assembly 110 in the embodiment depicted in figure 2 is formed by a first rectilinear section 112 perpendicular to the plane of symmetry XZ, a union elbow 114 and a second rectilinear section 116 parallel to the axis Z.

Downstream of the duct 116, there is the duct 118. Such a duct 118 is rectilinear and parallel to the axis Z and places the stabilization assembly 110 in fluid communication with the outside of the boat 10. The water conveyed into the stabilization system 20 is ejected towards the exit 119 that is located at the lower end of the duct 118.

The duct 118 is connected to the duct 116 in a per se known way, for example through bolted flanges. Similarly to the stabilization assembly 110, the stabilization assembly 120, placed on the opposite side of the boat 10 with respect to the plane of symmetry XZ, consists of a first rectilinear section 122 perpendicular to the plane of symmetry XZ, a union elbow 124 and a second rectilinear section 126 parallel to the axis Z. Downstream of the duct 126, there is the duct 128 through the lower end 129 of which the water sucked into the stabilization system 20 is ejected towards the outside. Figures 3 and 4 represent two further embodiments of the stabilization assemblies 110 and 120.

The stabilization assembly 110 depicted in figure 3 comprises, downstream of the union elbow 114, a first rectilinear duct 115, parallel to the axis Z, with constant diameter.

Downstream of such a duct there is a convergent tube 121 that conveys the water towards a second rectilinear duct 117. The positioning of the lower end 119 of the duct 117, with respect to the hull of the boat 10, will be optimized in order to maximize the lever arm of the force F_s. Similarly to the stabilization assembly 110, the stabilization assembly 120 consists of a first rectilinear duct 125, a convergent tube 131 and a second rectilinear duct 127. The stabilization assembly 110 depicted in figure 4 comprises, downstream of the union elbow 114, a curved union 122. Such a union 122 has the task of conveying the water towards a first rectilinear duct 123, tilted with respect to the axis Z. Downstream of the duct 123, there is the convergent tube 124 and the second rectilinear duct 125. Through the lower end of the duct 125, the water is ejected outwards along a direction that is incident with respect to the axis Z. The exit point of the water jet is closer, with respect to the embodiments described earlier, to the plane of symmetry XZ of the boat. In this way the lever arm F_s and consequently the stabilizing moment is increased. Similarly to the stabilization assembly 110, the stabilization assembly consists of a curved duct 132, a first rectilinear duct 133, a convergent tube 134 and a second rectilinear duct 135. Figures 5,6,7, 8 and 9 illustrate a further embodiment of the stabilization assemblies 110 and 120. The description given hereafter of the components of the stabilization assembly 110 should also be considered to be valid for the stabilization assembly 120.

With reference to figures 5, 6 and 7, the stabilization assembly comprises a water jetting turret 201. Such a turret 201, cylindrical in shape, can run inside a rectilinear guide 202, tilted with respect to the plane of symmetry XZ of the boat 10 and arranged along a direction parallel to a stabilizer fin 200 placed on the side of the boat 10. In the lower part of the turret 201 a plurality of nozzles 203 are arranged. Such nozzles 203 are aligned with one another and have the exit hole facing stern wards.

Arranged along an axis parallel to the axis of the turret 201, they allow the water jet exiting from the water jet 30 to be directed towards the lifting surface of the stabilizer fin 200, so as to substantially tangentially lick such a lifting surface, so that the water jets running over the upper profile of the stabilizer fin 200 gain speed, and exert a lower pressure than that produced by the seawater located beneath the fin itself.

Above the fin 200 a depression is consequently created, whereas in the part beneath a pressure develops; the resulting lift in turn generates a stabilizing moment Ms that can oppose the roll motion Mr to which the boat is subjected. Advantageously, the upper profile of the fin on which the water jets emitted by the water jetting turret 201 run is a convex surface with a profile that is suitable for generating the aforementioned lifting effect.

As illustrated in figure 7, the water jetting turret is positioned so as to be offset with respect to the middle line of such a fin 200, so that the water jets emitted manage to substantially tangentially lick just the upper wall of such a fin. The turret 201 can go from a passive configuration to an active configuration and vice versa. The passive configuration is for when the boat is in motion, see figure 9, the active configuration when the boat is anchored, see figure 10, in other words when the boat is not in navigation. In the passive configuration the turret is housed inside the guide 202 and does not project outside of the hull of the boat 10; in such a configuration the stabilization system is not active.

In the active configuration the turret 201 projects outside of the hull of the boat 10; in such a configuration the stabilization system is active and through the nozzles, placed in the lower end of the turret 201, the water sucked in by the water jet system 30 is ejected outside.

The stabilizer fin 200 towards which the water jets exiting from the nozzles 203 are directed can be either a fin already present in the structure of the boat, for example one of the fins usually used to stabilize the boat during navigation, or else a fin dedicated to the stabilization system 20.

The stabilization system 20 also comprises, with reference to figure 14, a detecting unit 140 and a control unit 130.

The detecting unit 140, in a per se known way, has the task of obtaining from sensors, not shown in the attached figures, parameters relative to the motion of the boat 10, like for example roll angle θ, roll speed dθ/dt, or roll acceleration 3²θ/5t².

Moreover, through the potentiometers 85 and 105, it is able to determine the opening angle of the valves 82 and 102.

Finally, the detecting unit 140 controls the control unit 130 through which the actuator devices 83 and 103 and the motor 54 are actuated. Hereafter we shall briefly describe the operation of the stabilization system 20 according to the invention. The stabilization system 20 can be actuated at the moment when the boat 10 on which it is mounted ceases navigation and is at anchor, for example within a port, a natural inlet or else in open sea.

Through the control unit 130 the motor 54 of the pumping assembly 50 is started, setting the impeller of the pump 52 in rotation.

The seawater that spontaneously penetrates inside the pump 52 through the suction assembly 40, since the pump is arranged at a lower level than sea level, is pushed outside of the pump body through the centrifugal force generated by the impeller. The accelerated water flow is sent by the pump 52 towards the forced flow duct 60 and from here it is divided into two equal flow rates that are channeled towards the two adjustment groups 70 and 90.

If the boat is not subject to any roll motion M_r, since the centrifugal pump 52 is able to work even if the deliveries are closed, the two adjustment devices 82 and 102 can be kept in closed configuration, preventing the water flow sucked in by the pump 52 from proceeding towards the stabilization assemblies, 110 and 120. It should be noted that in this way the noisiness of the entire stabilization device is reduced and this ensures greater comfort for the people located on board.

In another embodiment, in the absence of roll motion Mr the two adjustment devices 82 and 102 can be kept in an identical partially open configuration thus generating two identical flows towards the stabilization assemblies, 110 and 120. Also in this case the moment generated is zero, but the dissipation phenomena due to the turbulence induced by the water jets beneath the boat help stabilization. Hereafter we shall refer to the embodiment in which the two adjustment devices 82 and 102, in the absence of roll motion Mr, are kept in closed configuration. As soon as the unit 140 detects a tilting of the plane of symmetry of the boat XZ about the roll axis X, due to the appearance of a roll motion, the adjusting devices 82 and 102 are actuated. Specifically, with reference to figure 12, if the boat 10 is subject to a roll motion Mr that tends to make it rotate in the clockwise direction, the detecting unit 140, through the actuator 103, will actuate the adjustment device 102. The opening of the device 102 ensures that a pressurized water jet goes through the duct 106 to the stabilizing assembly 120 and that from here, through the opening 129, it is ejected into the sea.

As known, according to the Newton's second law of motion, the exiting water jet, at the opening 129, generates a reaction force F_s proportional to the exit speed of the jet itself V_s, to the flow rate Q and to the density p of the fluid, in detail F₅= pxQxV_s. The force F_s in turn creates a stabilizing moment M_s, equal to M₅= F_sxb_s, where b_s is the lever arm of the force F_s calculated with respect to the roll axis X- The stabilizing moment Ms opposes the roll motion Mr and causes an anti-clockwise rotation on the boat that tends to take the boat 10 back into equilibrium. The value of the force Fs depends, as described above, upon the flow rate Q that flows through the stabilization assembly 120 and consequently the degree of opening of the adjustment member 102.

With the valve 102 in all-open configuration, and the symmetrical valve 82 closed, the maximum value of the stabilizing force Fs is obtained, the flow rate Q flowing through the stabilization assembly 120 being at maximum and the exit speed V_s of the water jet also being at maximum.

Intermediate stabilizing force values can be obtained by partialising the flow rate that flows towards the stabilization assembly 120, by suitably actuating the adjusting member 102. The detecting unit 140, once at least one parameter relative to the motion of the boat has been received, indeed has the task of determining what force value Fs must be generated to create a stabilizing moment Ms that neutralizes the roll motion Mr acting upon the boat 10.

Hypothesizing Fs is equal to Mr/b_s, the adjustment device 102, disregarding the load losses that occur along the stabilization system 20, must allow a flow rate Q equal to [(M_rxA_s)/( b_sxp)]^1/2 to flow inside the stabilization assembly 120, where A_s indicates the cross section of the exit 129.

Analogously, with reference to figure 13, if the boat 10 is subjected to a roll motion Mr that tends to make it rotate in the anti-clockwise direction, the detecting unit 140, through the actuator 83, actuates the adjustment device 82. The opening of the device 82 ensures that a pressurized water jet goes through the duct 86 to the stabilizing group 110 and that from here, through the opening 119, it is ejected into the sea.

Also in this case a force Fs is generated that is proportional to the flow rate Q and the exit speed V_s. Such a force F_s creates, with respect to the roll axis X, a moment Ms that acts in the clockwise direction and that opposes the roll motion recorded by the detecting unit 140.

As described earlier, the roll motion of a boat is by its very nature an oscillating motion, and consequently alternatively a clockwise roll motion Mr and an anticlockwise roll motion Mr act upon the boat 10. Therefore, during normal operation of the system 20, the stabilization steps described earlier follow on from one another: clockwise and anti-clockwise stabilizing moments Ms are generated alternately, with the purpose of keeping the boat in equilibrium. The operation of the stabilization system 20 illustrated in figures 5, 6, 7, 8, 9 is analogous to what has been described earlier relative to the step of detecting the motion of the boat and of actuating the flow adjusting devices. However, it does have some special features with regard to the operation of the two stabilization assemblies

110 and 120.

It is worth noting that at the moment when the boat ceases navigation, through the detecting unit 130, both the actuation motor 54 of the pump 52, and the translation device that allows the water-jetting turret 201, arranged at the sides of the boat 10, to run along the respective guides 202, are actuated.

The turrets 201 go from the passive configuration to the active configuration.

If the boat is not subject to any roll motion Mr. the two adjusting devices 82 and 102 are kept in closed configuration, preventing the water flow sucked in by the pump 52 from proceeding towards the stabilization assemblies 110 and 120.

In a second embodiment, in an analogous way to what has been described earlier, the two adjusting devices 82 and 102 can be kept in an identical partially open configuration thus generating two identical flows towards the stabilization assemblies 110 and 120. Hereafter we will refer to the embodiment in which the two adjusting devices 82 and

102, in the absence of roll motion Mr, are kept in closed configuration.

As soon as the detecting unit 140 detects a roll motion of the boat, as described earlier, through the control unit 130 the adjustment device, 82 or 102 is actuated; the water flows towards the stabilization assemblies 110 or 120. In this case, however, it is no longer a single water jet that is ejected by the stabilization system. The flow rate that has flowed through the adjustment device, 82 or 102, indeed, is divided into a plurality of jets, the number of which is equal to the number of nozzles 203 arranged on the water jetting turret 201.

The water jets are directed onto the lifting surface of a stabilizer fin 200 arranged near to the water jetting turret 201. The exit direction of such jets is parallel to the roll axis X and therefore the stabilizing force Fs that is created based on the impulse principle no longer generates a stabilizing moment analogous to what has been described earlier as Ms, since the relative lever arm of the force bs is zero. The water jets, however, striking the lifting surface of the fin 200, allow the lift of the fin itself to be exploited.

Indeed, the water jets that run over the upper profile of the stabilizer fin 200 gain speed, and exert a lower pressure than that produced by the seawater located beneath the fin itself. Above the fin 200 a depression will consequently be created, whereas in the part underneath a pressure develops; the resulting lift in turn generates a stabilizing moment Ms that can oppose the roll motion Mr to which the boat is subjected. As will be clear to the man skilled in the art, the stabilization of an anchored boat, i.e. when the boat is not in navigation, allows the people on board not to suffer from the effects of seasickness. This allows better on-board living conditions, ensuring high comfort.

The man skilled in the art can add modifications and/or replacements of elements described with equivalent elements to the embodiments of the stabilization system 20 described above, in order to satisfy specific requirements, without for this reason departing from the scope of protection of the attached claims.

Claims

1. Stabilization system (20) for a boat (10) having a roll axis (X), comprising: at least one detecting device (140) suitable for detecting at least one parameter associated to a boat (10) motion about the roll axis (X); - a control unit (130) suitable for processing the at least one parameter provided by the detecting device (140); characterized in that it further comprises at least one water jet unit (30) suitable for generating, on the basis of the data received from the control unit (130), the ejection of a water jet which causes a force (Fs) whose moment, calculated with respect to the roll axis (X), opposes the roll motion (Mr) of the boat (10).

2. System (20) according to claim 1, characterized in that the water jet, generated by the water jet unit (130) and causing the force (Fs), is ejected out of the boat (10) by means of two stabilization assemblies (110, 120) positioned symmetrically each other with respect to a vertical plane of symmetry of the boat (10).

3. System (20) according to claim 1 or 2, characterized in that each of the two stabilization assemblies (110, 120) comprises a water jetting turret (201); a plurality of nozzles (203) being provided on said water jetting turret (201).

4. System (20) according to claim 3, characterized in that said water jetting turret (201) can translate inside a guide (202) so as to move from a passive configuration, in which it is housed inside the hull of the boat (10), to an active configuration, in which it is placed outside the boat (10) and vice versa.

5. System (20) according to any claims from 1 a 4, characterized in that it comprises a stabilizer fin (200) comprising a lifting surface; said water jet generated by said water jet unit (30) is directed towards the lifting surface of said stabilizer fin (200) so as to lick said lifting surface in a substantially tangential manner, so that said jet running over the upper profile of the stabilizer fin (200) gains speed and exerts a lower pressure than that exerted by the water on the surface of said fin (200) opposite said lifting surface.

6. System (20) according to claim 3 or 4 and the claim 5, characterized in that a stabilizer fin (200) is coupled to each of said water jetting turrets (201); the nozzles

(203) of said water jetting turrets (201) being suitable to direct the water jet generated by the water jet unit (30) toward the lifting surface of said fin (200) so as to lick said lifting surface in a substantially tangential manner, so that the jets running over the lifting surface of said stabilizer fin (200) gain speed and exert a lower pressure than that exerted by the water on the surface of said fin (200) opposite said lifting surface.

7. System (20) according to claim 5 or 6, wherein said lifting surface is a convex surface with a profile that is suitable for generating the aforementioned lifting effect.

8. System (20) according to claim 6 and 7, wherein said water jetting turret is positioned so as to be offset with respect to the middle line of such a fin (200), so that the water jets emitted manage to substantially tangentially lick just said convex lifting wall of such a fin.

9. System (20) according to any claims from 1 to 8, characterized in that the water jet unit (30) comprises two adjustment devices (82, 102) suitable to adjust the rate of the flow generated by the water jet unit (30), said devices (82, 102) being able to move from an all-open configuration to an all-closed configuration by passing through intermediate configurations, and vice versa.

10. System (20) according the claim 9, wherein each of said flow adjustment devices (82,102) comprises a butterfly valve.

11. System (20) according to claim 10, characterized in that each butterfly valve (82, 102) is coupled to a potentiometer (85, 105) suitable to detect the opening degree of the butterfly valve.

12. System (20) according to any of claim 1 to 11, characterized in that the water jet unit (30) comprises a suction assembly (40) suitable for conveying inside the water jet unit (30) the water sucked outside the boat (10).

13. System (20) according the claim 12, wherein the entry (42) of the suction assembly (40) is positioned on the central keelson of the boat (10).

14. Boat comprising a stabilization system, characterized in that said stabilization system is a system in accordance with any claims from 1 to 13, when said boat is not in navigation, said water jet unit (30) making it possible to generate the emission of said water jet that creates a force (Fs) the moment of which, calculated with respect to the roll axis (X), opposes the roll motion (Mr) of the boat (10).

15. Method for stabilization of a boat (10), having a roll axis (X), when said boat is not in navigation comprising the steps of:

- detecting, by means of a detecting device (140), at least one parameter associated to a boat (10) motion about the roll axis (X);

- processing, by means of a control unit (130), the at least one parameter detected by the detecting device (140); - generating, by means of a water jet unit (30) and on the basis of the data received from the control unit (130), a water jet causing a force (Fs) whose moment, calculated with respect to the roll axis (X), opposes the roll motion (Mr) of the boat (10).

16. Method for boat (10) stabilization according the claim 11, wherein the generated water jet is directed toward lifting surfaces (200) provided on the boat (10) sides so that the generated lift causes a moment, calculated with respect to the roll axis, which opposes the roll motion (Mr) of the boat (10).