WO2010143085A2

WO2010143085A2 - Anti-rolling device and method for a boat

Info

Publication number: WO2010143085A2
Application number: PCT/IB2010/052035
Authority: WO
Inventors: Michele Sferrazza
Original assignee: Rodriquez Marine System Srl
Priority date: 2009-05-11
Filing date: 2010-05-07
Publication date: 2010-12-16
Also published as: IT1394059B1; ITMI20090789A1; WO2010143085A3

Abstract

The present invention relates to an anti-rolling device for a boat (12). The boat comprises at least two fins (16) associated with the hull (14) and has two cruising speeds, a first slow cruising speed and a second fast cruising speed. The anti-rolling device is characterized in that the fins comprise at least one hydrodynamic appendix (20) which is movable at least between a first extracted position associated with the slow cruising speed and a second retracted position associated with the fast cruising speed. The invention further relates to an anti-rolling method.

Description

Anti-rolling device and method for a boat

DESCRIPTION

The present invention relates to an anti-rolling device for a boat.

Rolling is known to be the pivotal motion of a boat about the fore-and-aft axis of the boat, which is also known as longitudinal axis.

The rolling motion may occur in two different situations: with the boat at anchor, or with the boat under way. The present invention relates to an apparatus and a device for stabilizing the boat when it can move relative to water. Particularly, a relative motion of the boat is concerned, because the present invention is also applicable to a boat that is stationary relative to a fixed reference system, but moves relative to water. A number of anti-rolling systems are known in the art. One method, that has been known since ancient times and is still used, is load distribution.

With this method, load is arranged along the sides of the ship, symmetrically with respect to the longitudinal axis. When rolling is initiated due to external causes, the moment of inertia of the load acts as a damper, through a damping moment. It will be easily appreciated that the load distribution method applies to both dynamic and static situations.

Nevertheless, this method still has some drawbacks, for instance it is not applicable when the hold of the boat is of inadequate size. A second drawback arises, for instance, when the boat is in a no-load condition. Li these cases, no damping moment, as described above, can be generated. A second rolling stabilization method provides the use of a gyroscopic system. A gyroscope is known to be a rotating physical device which, due to the law of conservation of angular momentum, tends to hold its spin axis oriented in a fixed direction. Particularly, if the gyroscope is mounted to a Cardan's suspension, allowing free orientation of the gyroscope in the three directions of space, its axis is held oriented in the same direction even if orientation of the support changes.

The gyroscope property that is used for boats is gyroscopic precession. As a force is applied to the axis of the gyroscope the gyroscope reacts to the force with a 90° delay. In short, a moment applied to the gyroscope by a rolling motion is converted by the gyroscope into a pitch moment response. Since the longitudinal dimension of the boat is much greater than its transverse dimension, the effect of a pitch moment is smaller than that of a rolling moment of identical amount.

Application to a boat occurs through at least one gyroscope rotated by motor means. The gyroscopic system may be used according two operating modes. In a first operating mode, the spin axis of the gyroscope is integral with the boat structure so that, as a displacement is applied in the transverse rolling axis, it is converted into a reaction in the longitudinal pitch plane.

In a second operating mode, the spin axis is not integral with the boat structure, and is subjected to the action of actuators. Such actuators, controlled by a rolling sensitive unit, cause a pitch movement of the gyroscope axis relative to the axes of the boat. Such pitch movement is thus converted into a rolling moment which can damp the rolling movement of the boat caused by wave motion.

Like previous methods, this method also suffers from certain drawbacks, including the volume required by gyroscopes and their weight. Gyroscopes are placed in the hold of the boat, and occupy part of the space that would be otherwise available to the payload. Furthermore, torsional moments about the hull of the boat, caused by the weight of gyroscopes, are unavoidable.

A further method, which is also widely used in small oats, is the method of passive fins,

In this method, fixed fins are located at the sides of the boat hull, on a plane that passes through the longitudinal direction of the boat and is inclined by 45° to the plane of calm water.

The size of such fins is selected according to the cruising speed of the boat, their extension, chord and profile depend on special requirements and on the boat size.

Particularly, in one embodiment, the fins may pivot about a main axis that passes through the two end profiles of the fin, for variable angle of attack. Nevertheless, this solution also has drawbacks.

A first drawback is recognized when the ship has two cruising speeds, which occurs, e.g. when mixed propulsion is used, e.g. diesel engine and gas turbine propulsion.

This kind of boats may either use their diesel engine only, for a first slow cruising speed, or both engines at the same time, to obtain a second fast speed, higher than the first. As is known, the lift formula for any aerodynamic surface depends not only on speed but also on wing aspect ratio and area.

Since the size of the fins may be selected for one cruising speed only, they cannot be effective for two cruising speeds. Particularly, when the size of the fins is selected in view of a fast cruising speed, its area will be insufficient for the slow cruising speed. Conversely, when the size of the fins is selected in view of a slow cruising speed, a larger area will be obtained, which will increase the drag of the ship at the fast cruising speed.

Therefore, the present invention is aimed at obviating the above drawbacks.

A first object of the present invention is to provide an anti-rolling device that is compact and can be used on both small and large boats. A second object of the present invention is to provide an anti-rolling device that can be IB2010/052035

effective at least at two separate cruising speeds.

Further advantages and characteristics of the present invention will appear more clearly from the following detailed description of a few embodiments, which is given by way of example and without limitation, with reference to the annexed drawings, in which: - Fig. 1 is a side view of a boat having an anti-rolling device of the invention in a first configuration;

- Fig. 2 is a side view of a boat having an anti-rolling device of the invention in a second configuration;

- Fig. 3 is a schematic front view of a boat having an anti-rolling device of the invention in a first configuration;

- Fig. 4 is a schematic front view of a boat having an anti-rolling device of the invention in a second configuration;

- Fig. 5 is a perspective view of an anti-rolling device of the invention in a first configuration; - Fig. 6 is a perspective view of an anti-rolling device of the invention in a second configuration;

- Fig. 7 is a perspective view of a detail of an anti-rolling device of the invention;

- Fig. 8 is a side view of an anti-rolling device of the invention; and

- Fig. 9 is a perspective view of a second embodiment of the anti-rolling device of the invention.

Referring now to Figs. 1 and 2, the anti-rolling device 15 of the invention has at least two fins 16 associated with the hull 14 of the boat 12. The boat 12 is designed to sail at least at two cruising speeds: a slow cruising speed and a fast cruising speed. The device of the invention is characterized in that each of said fins 16 comprises at least one aerodynamic appendix 18 movable between at least one extracted position and a retracted position. As used herein, the term retracted position is intended to designate a position in which the appendix has a water-impinged surface whose area is at least 30% smaller than in the extracted position.

Particularly, the extracted position is associated with the slow cruising speed sailing condition and the retracted position is associated with the fast cruising speed sailing condition. According to the embodiment as described herein, each of the fins 16 has two hydrodynamic appendices 18 and 20, at least one whereof is movable between a first extracted position and a second retracted position. Referring to Figures 1 and 3 the following definitions apply: - a longitudinal direction (designated in Fig. 1 by numeral 11) is any direction parallel to the fore-and-aft line of the boat;

- a transverse direction (designated in Fig. 3 by numeral 13) is any direction perpendicular to the previous one, and parallel to the calm water plane; and

- a longitudinal plane is parallel to the longitudinal direction and perpendicular to the transverse direction.

Referring to Figures 3 and 4, the fin 16 of the invention has a first hydrodynamic appendix 18 associated with the hull 14 of the boat 12, and a second hydrodynamic appendix 20 associated with the first hydrodynamic appendix 18.

The fins 16 may be located all along the submerged portion of the hull 14, preferably in symmetric positions with respect to the longitudinal plane of the boat 12.

Furthermore, the angle a between the plane that contains the fin 16 and the longitudinal plane (see Figure 3) is from 0° to 90°, preferably from 30° to 60°.

Both appendices 18, 20 may have any aerodynamic profile selected from those that are typically used in the naval and aeronautical fields, e.g. concave-convex or plane-convex profiles. In one embodiment, the fin 16 is connected to the hull 14 of the boat by means of a rod 22 that can be fixed or rotate about its longitudinal axis 24 (see Figures 5, 6 and 9). If the rod 22 rotates about its longitudinal axis 24, it can also cause rotation of the fin 16 about such axis 24. The appendix 18 is the portion of the fin 16 adjacent to the hull 14, and the surface of the appendix 18 adjacent to the hull 14 is particularly defined as root.

The appendix 18 comprises a leading edge 26 and a trailing edge 28 and can be retracted relative to the hull 14 in two modes. In a first mode, it slides parallel to the axis 24 to full or partial insertion into the hull 14. In a second mode, the fin is pivoted parallel to its lying plane so that, with the appendix 18 retracted, its leading edge is substantially parallel to the outer surface of the hull 14.

In both modes, a door (not shown) may be used, which is able to isolate the appendix 18 from the environment, when it is in the retracted position.

The end edge 30 of the appendix 18 opposite to the root has a blind or through lead-in aperture 32. The aperture 32 is adapted to allow the second appendix 20 to slide into the first appendix 18.

Referring now to Figures 7 and 8, numeral 34 designates the inner surface of the aperture 32 and numeral 36 designates the track of said inner surface 34 on the end edge 30. The track 36 will be of such a size as to allow some clearance between the first appendix 18 and the second appendix 20 when the latter is inserted in the first appendix 18. The inner surface of the aperture 32 is designed to be coupled with some clearance with the outer surface 38 of the second appendix 20.

In one possible embodiment, a seal, e.g. made of rubber, may be used, which is situated at the end edge 30 of the first appendix 18 and is adapted to prevent the ingress of water into the space between the inner surface 34 of the aperture 32 and the outer surface 38 of the second appendix 20. The second appendix 20 has at least two operating positions relative to the first appendix 18: a retracted position and an extracted position. It can be directly or indirectly connected to the rod 22 and follow its movements like the first appendix 18. The second appendix 20 has a leading edge 40 and a trailing edge 42. The appendix 20 is retractable relative to the first appendix 18, by sliding parallel to the axis 24 to full or partial insertion into the first appendix 18. A door (not shown) may be used, which is able to isolate the appendix 20 from the environment, when it is in the retracted position. Referring now to the alternative embodiment of the invention as shown in Figure 9, a possible configuration is shown, in which a lead-in aperture 44 is formed on an inner edge 46 opposite to an end edge 48 of the second appendix 20. Like in the previous case, an inner surface 50 of the lead-in aperture 44 is designed to be coupled with some clearance with an outer surface 52 of the first appendix 18. Particularly, the track 54 of the inner surface 50 on the inner edge 46 is adapted to be coupled with some clearance with the outer surface 52 of the first appendix 18. One alternative embodiment may provide the use of plates, designated by references 56, 58 and 60. These plates have a longitudinal plane profile similar to the profile of the appendices 18 and 20, but a larger size.

The plates 56, 58 and 60 are arranged on planes perpendicular to the axis 24. They are located: - at the root of the appendix 18 (plate 56);

- at the inner edge 46 of the second appendix 20 (plate 58; and

- at the end edge 48 of the second appendix 20 (plate 60).

Their function is to maintain as much as possible the lack of turbulence of the water that impinges upon the fin, and particularly to prevent end effects, e.g. caused by the discontinuity between the two appendices, from perturbing the laminar flow. The movement of the appendices 18 and 20 is obtained by the use of a linear actuator (not shown), which may be, for instance, of pneumatic, elecrropneumatic or rack-and- worm type. Particularly, by coupling said actuators in a known manner to the appendices 18 and 20, the following movements may be obtained.

According to a first embodiment, at least one hydrodynamic appendix 18 may be used, which is movable between a first fully extracted position to a retracted position. In this embodiment, there are three possible operating conditions:

- a first condition in which the appendix is fully extracted; - a second condition in which the appendix is partially extracted and has a water- impinged surface area smaller than the previous case; and

- a third condition in which the appendix is fully retracted in the hull 14. According to this embodiment, there are at least two hydrodynamic appendices, therefore there may be two cases: - a first case in which the first appendix 18 is rigidly fixed to the hull 14 of the boat 12 and the second appendix 20 is movable relative to the first appendix 18; and

- a second case in which the first appendix 18 is movable relative to the hull of the boat 12 and the second appendix 20 is movable relative to the first appendix 18.

In the first case, there may be two possible operating conditions: - a first operating condition with the second appendix 20 extracted; and

- a second operating condition with the second appendix 20 retracted. In the second case, there may be three possible operating conditions:

- first appendix 18 extracted and second appendix 20 extracted;

- first appendix 18 extracted and second appendix 20 retracted; and - both first and second appendices 18, 20 retracted. The size of the fin 16 is selected based on an expected lift value required of the fin, as is known:

P =i pv²SC_p where P : lift; p : water density; v² : relative speeds of water and moving body; S : wing area; and C_p : lift coefficient.

The size will be thus apparently selected for a given cruising speed (v²) and will be followed by the selection of a wing shape (C _p) and by the calculation of a wing area value (S).

The above structure allows sizing to fit two separate cruising speeds, as two different extensions of the hydrodynamic surfaces may be used. Thus, for example, a first size may be selected for a first slow cruising speed, which accounts for the extension of the surface of the fin 16 having at least both the first appendix 18 and the second appendix 20 extracted.

Likewise, a second size may be selected for a second fast cruising speed, which accounts for the extension of the surface of the fin 16 having, for instance the first appendix 18 extracted and the second appendix 20 retracted. The skilled person will understand that the first size is selected for a slow cruising speed, that uses, for instance, one of the two engines, whereas the second size is selected for a second fast cruising speed that uses, for instance, both engines.

As used herein, the terms slow and fast cruising speed designate, for instance, speeds obtained using the diesel engine only or the diesel engine - gas turbine combination respectively. The fins 16 operate in response to a rolling movement, by generating an oppositely directed damping moment.

In a first embodiment, the fins 16 are passive, i.e. have no motion relative to the hull 14.

In this case, the rolling movement of the boat 12 will change the angle of attack of the fin 16 relative to water flow. This will generate the lift required for a damping moment to be applied to the boat 12.

In a second embodiment, the damping moment is obtained by changing the angle of attack of the fin 16 by rotation about the axis 24. Particularly, assuming that there is one fin 16 at each side of the hull 14, the above described movement will be obtained by rotating one of them to a positive angle of attack and the other fin 16 to a negative angle of attack. Thus, the rotation imparted to the hull 14 will impart a lifting movement to the side of the hull 14 with the fin 16 that forms the positive angle of attack . In a further embodiment, stabilizers are used at the trailing edges 28, 42 of the fins 16 for changing lift, in much the same manner as in aircrafts. The present invention further relates to an anti-rolling method for a boat 12 having two separate cruising speeds, i.e. a first slow cruising speed and a second fast cruising speed.

The boat further comprises at least two fins 16 associated with the hull 14, each of said fins 16 comprising at least one movable hydrodynamic appendix 18.

The anti-rolling method of the invention includes the step of moving the hydrodynamic appendix 18 between a first extracted position associated with the slow cruising speed and a second retracted position associated with the fast cruising speed, or vice versa.

The skilled person may elect to change elements of the above described embodiments and/or replace them with equivalents for the purpose of fulfilling particular requirements, without departure from the scope of the annexed claims.

Claims

1. Anti-rolling device for a boat, comprising at least two fins (16) coupled to the hull (14) of the boat (12), said boat (12) having two cruising speeds, a first slow cruising speed and a second fast cruising speed, characterized in that said fins (16) comprises at least an hydrodynamic appendix (20) movable between at least a first extracted position associated to the slow cruising speed, and a second retracted position associated to the fast cruising speed.

2. Device according to claim 1 characterized in that each of said fins (16) comprises a first and a second hydrodynamic appendixes (18, 20).

3. Device according to any preceding claim characterized in that the first hydiOdynamic appendix (18) is rigidly fixed to the hull (14), whereas the second hydrodynamic appendix (20) is retractable inside the first hydrodynamic appendix (18).

4. Device according to any claim 1 or 2 characterized in that the first hydiOdynamic appendix (18) is rigidly fixed to the hull (14), whereas the second hydrodynamic appendix (20) is retractable so that in the retracted configuration the first hydrodynamic appendix (18) is housed inside the second hydrodynamic appendix (20).

5. Device according to any claim 1 or 2 characterized in that said first and second hydrodynamic appendixes (18, 20) are both retractable.

6. Device according to any preceding claim characterized in that it comprises at least a plate (56, 58, 60) having a profile similar to that of the hydrodynamic appendix but having larger dimensions and being placed parallely to the profile of the hydrodynamic appendix (18, 20).

7. Device according to the preceding claim characterized in that said plates (56, 58, 60) are placed: at the root of the first appendix (18); at the internal edge (46) of the second appendix (20); and at the tip edge (48) of the second appendix (20).

8. Device according to any preceding claim characterized in that the angle (a) comprised between the plane containing the fin (16) and the longitudinal plane of the boat (12) is comprised between 0° and 90°.

9. Device according to the preceding claim characterized in that said angle (a) is comprised between 30° and 60°.

10. Anti-rolling method for a boat (12), said boat: having two different cruising speed, a first slow cruising speed and a second fast cruising speed, comprising at least two fins (16) coupled to the hull (14), each of said fins comprising at least a movable hydiOdynamic appendix (18), wherein said method comprises the step of moving said hydrodynamic appendix (18) from a first extracted position associated to the slow cruising speed and a second retracted position associated to the fast cruising speed, and vice- versa.

11. Anti-rolling method according to claim 10, wherein each one of said at least two fins (16) comprises a first hydrodynamic appendixes (18) rigidly fixed to the hull (14), and a second hydrodynamic appendix (20) which is retractable, wherein comprises the step of moving said second hydiOdynamic appendix (20) between said first extracted position during the slow cruising speed and a second retracted position during the fast cruising speed, and vice- versa.