WO2009083892A2

WO2009083892A2 - Device for stabilising the rolling motion of boats.

Info

Publication number: WO2009083892A2
Application number: PCT/IB2008/055488
Authority: WO
Inventors: Daniele Maria Bertin
Original assignee: Calzoni S.R.L.
Priority date: 2007-12-28
Filing date: 2008-12-22
Publication date: 2009-07-09
Also published as: ITBO20070851A1; WO2009083892A3

Abstract

The stabilising device for boats comprises two propulsion units (2) emerging from a hull of the boat and positioned on opposite sides of a boat longitudinal axis (A3), each of the propulsion units (2) comprising a fin (3) and motor means for rotating the fin (3) both about its first axis (Al) of longitudinal extension, and about a second axis (A2).

Description

Device for stabilising the rolling motion of boats

Technical Field

The present invention relates to a device for stabilising rolling motion for boats and, in particular, a device able to stabilise boats relative to rolling motion.

Background Art

Rolling is the oscillation of a boat about its longitudinal axis, which is therefore also known as the roll axis.

In boats, ships and watercraft in general, rolling is an oscillating motion caused not just by the effect of wave motion, but by the shifting of weights on board and the interaction of all external forces having a component transversal to the longitudinal axis.

To oppose and/or reduce the rolling motion of boats, many different methods were developed, more or less effective even according to the dimensions of the boat. For example, a known solution is to have fins emerging from the hull of a craft and immersed in the water, of the fixed type or rotating about a respective axis. The fins are effective when the craft is moving, since they can generate lift using the thrusting action of the water on them.

In contrast, patent document GB 780,836 describes the use, to oppose rolling motion, of cycloidal propulsion systems with rotary blades, also known as

Voith-Schneider propellers. In particular, said document indicates that the propellers should be placed in suitable recesses made in the hull of the boat, to limit exposure of their blades to fluid dynamic currents while navigating.

The stabilising devices described above, designed to oppose the rolling motion of a boat, although being effective in predetermined circumstances, have significant limitations linked to their specificity.

The fins emerging from the hull do not offer any capacity for damping the rolling motion when the boat is not moving, nor when the boat is moving at low speed. The rotary blade propulsion systems described in document GB 780,836 are, in contrast, substantially ineffective when the boat is moving, since they are not exposed to the hydrodynamic flow.

Disclosure of the Invention The present invention therefore has for an aim to overcome the above- mentioned disadvantages by providing a device for stabilising boats which is effective substantially in all circumstances and which, at the same time, is simple and practical to use.

The technical features of the invention according to the aforementioned aim may be easily inferred from the content of the appended claims, especially claim 1 , and preferably any of the claims that depend, either directly or indirectly, on claim 1.

Brief Description of the Drawings The advantages of the present invention are more apparent from the detailed description which follows, with reference to the accompanying drawings which illustrate a preferred embodiment of the invention provided merely by way of example without restricting the scope of the inventive concept, and in which:

Figure 1 is a schematic plan view of a first embodiment of a stabilising device in accordance with the present invention;

Figure 2 is a schematic elevation view of a portion of a hull on which the device of Figure 1 is installed;

Figures 3 to 5 are respective schematic plan views of three different operating modes of the device of Figure 1 ; Figure 6 is a graph illustrating the operating mode of Figure 5; Figure 7 is a schematic plan view of another operating mode of the device of Figure 1;

Figure 8 is a graph illustrating the operating mode of Figure 7;

Figures 9 and 10 illustrate, in respective schematic elevation views, two alternative geometric arrangements of the device in accordance with the present invention;

Figures 11 and 12 illustrate, in respective schematic plan views, two different operating modes of a first alternative embodiment of the device in accordance with the present invention; Figures 13 and 14 illustrate, in respective schematic plan views, two different operating modes of a second alternative embodiment of the device in accordance with the present invention;

Figures 15 and 16 illustrate, in respective schematic plan views, two different operating modes of a third alternative embodiment of the device in accordance with the present invention.

Detailed Description of the Preferred Embodiments of the Invention

As illustrated in Figures 1 and 2, the numeral 1 denotes the visible parts of a portion of a device for stabilising boats, hi particular, Figures 1 and 2 schematically illustrate a propulsion unit 2 in accordance with a first embodiment of the device 1.

The propulsion unit 2 comprises a fin 3 having a first, longitudinal axis Al and a main body 4, designed to rotate about a second axis A2. The body 4 is represented in the accompanying drawings as a circle drawn with a dashed line.

The stabilising device 1 comprises two propulsion units 2 positioned on opposite sides of a longitudinal axis A3 of a boat 5, the axis A3 also forming a respective roll axis for the boat 5. Figure 2 illustrates a portion of a cross-section of the boat 5 where the outermost edge of the hull is shown. From the hull there emerge, respectively on the right and left of the line of symmetry Sm, the respective fins 3 of the two propulsion units 2. Basically, the two propulsion units belonging to the boat 5 mirror one another relative to the vertical line Sm passing through the roll axis A3.

In other words, relative to an observer positioned on the stern of the boat along the roll axis A3, a first propulsion unit 2 is positioned on his right and a second propulsion unit 2 is positioned on his left. The stabilising device 1 also comprises motor means, not visible in the accompanying drawings, both for rotating the fin 3 about its first axis Al, and for rotating the body 4, and therefore also the fin 3 supported by it, about the second axis A2.

The motor means are designed to drive the two above-mentioned rotations even independently of each other, as described in detail below.

As illustrated in Figures 9 and 10, the propulsion unit 2 is positioned on the keel of the boat, in an optimum position for generating a torque force for opposing the roll torque, and may comprise one or more fins 3.

The embodiment of the propulsion unit 2 illustrated in Figure 9 comprises one or more fins 3 positioned with the first axis Al parallel with the second axis A2 of rotation of the main body 4.

In contrast, the embodiment illustrated in Figure 10 comprises one or more fins 3 positioned with the first axis Al at an angle to the second axis A2 of rotation of the main body 4. Figure 11 shows a second embodiment of the propulsion unit 2 in which the unit 2 comprises two fins 3a, 3b positioned in such a way that they are paired.

Basically, fins are paired by positioning a pair of fins 3a, 3b close together so that the changes to the hydrodynamic flow caused by one affect the other.

Although fin size must be taken into consideration, for the purposes of this description paired fins shall be defined as two fins 3 a, 3 b whose respective first axes Al are separated by an angle which is at least less than 180° and, advantageously, less than 90°.

Again with reference to Figure 11, the two paired fins 3a, 3b are illustrated respectively with a dashed line and with a continuous line in two different configurations for use. Figures 13 and 14 illustrate a third embodiment of the propulsion unit 2 in which the unit 2 comprises two fins 3a, 3b which are positioned so that they are diametrically opposed to each other relative to the second axis A2.

Figures 15 and 16 show a fourth embodiment of the propulsion unit 2 in which the unit 2 comprises two pairs of fins 3a, 3b and 3a', 3b' which are paired.

The stabilising device 1 also comprises a control unit, not illustrated, for the motor means, also not illustrated.

The control unit comprises an inclinometer and/or an accelerometer for measuring the boat 5 instantaneous angle of roll relative to a horizontal reference plane. For the device I₃ the inclinometer and accelerometer therefore form means for measuring the angle of roll.

In practice, thanks to said measuring means, the control unit measures the angle of roll, that is to say, the boat 5 instantaneous angle of inclination on its longitudinal axis. When the boat 5 is moving, the stabilising device 1 advantageously implements a passive operating mode, in which the fins 3 operate in a similar way to the normal lateral fins of a hydrofoil, therefore generating a lift P able to counterbalance the rolling motion of the boat 5.

In this operating mode, depending on the angle of inclination measured by the measuring means, the control unit controls the motor means so that they drive a consequent angular rotation of the fins 3 about their respective first axis Al of longitudinal extension or about the second axis A2 or a combination of rotations about the two axes Al and A2.

Normally, the greater the angle of inclination is, the greater the angle of rotation of the fins 3 about the first axis Al will be, relative to a minimum or null lift condition, which is taken as a reference. As is known, lift increases with an increase in the striking angle which, as is known, is the angle between the direction of the flow and a central plane of the fin.

The device therefore operates using feedback in a loop, with continuous readings of the inclination of the boat and consequent continuous adjustments of the inclination of the fins 3.

As illustrated in Figures 3 and 4, the inclination of the fins 3, at least in the case of propulsion units 2 equipped with a single fin 3, may be obtained with rotations of the fin 3 about its own first axis Al, or with rotation of the fin 3, stationary relative to the first Al, about the second axis A2, or with partial rotations about both of the axes Al, A2. The latter opportunity is advantageously used to optimise the thrusts, exploiting transitory hydrodynamic phenomena induced by the movement of the fin 3.

Figures 3 and 4, representing the condition of the boat while navigating, illustrate two stabilising device 1 operating modes, both passive. In them, the torque opposing the rolling motion is generated by the lift P created not so much by the active movement of the fin 3, but due to the hydrodynamic flow striking it. hi the passive operating mode movement of the fins 3 is limited exclusively to their angling relative to the direction of boat 5 movement. When the boat 5 is not navigating, the fins 3 of the propulsion units 2, driven by respective motor means not illustrated, are caused to move both about their own first axis Al, and about the second axis A2, producing a stabilising device 1 active operating mode. hi Figure 5 the reaction of the fluid to rotation of the fins 3 about the axis A2 is exploited. Said reaction generates a thrust S on the fins 3, which, thanks to the distance between the fins 3 and the boat 5 longitudinal axis A3, may be translated into a torque able to oppose the boat 5 rolling motion.

The control unit synchronises the movement of the fins 3 of the two propulsion units 2 so that each of them provides a torque opposing that generating the boat 5 rolling motion.

In detail, as illustrated in Figure 5, with propulsion units 2 equipped with a single fin 3, it is appropriate to synchronise rotation of the fin 3 about the second axis A2 with the main rolling motion of the boat 5. In this way, with a clockwise rotation, at position A, a vertical thrust S is obtained, due to the reaction of the water on the fin 3, the thrust being directed downwards. Assuming that the optimum direction of thrust to be applied in order to balance the rolling motion is vertical, the control unit uses the motor means and controlled rotations of the fin 3 about the first axis Al, to keep the fin 3 substantially parallel with itself during rotation about the second axis A2. At the position labelled B in Figure 5, the fin 3 will substantially not receive any thrust from the water but, when the fin 3 reaches the position labelled C, diametrically opposed to the position A, the thrust S received from the water will be equal and opposite to that received at A and therefore, it is appropriate that the time taken by the fin 3 to pass from position A to position C, that is to say, to rotate through 180°, substantially coincides with the period of the boat 5 oscillation caused by the rolling motion.

At position D, similarly to position B, the fin 3 will substantially not receive any thrust from the water.

In other words, the control unit synchronises the movement of the fin 3 of each propulsion unit 2, both in terms of period and phase, so that the thrust S they generate opposes the torque generated by the wave motion which produces boat 5 rolling.

Said optimum condition is illustrated in the graph in Figure 6, in which the sine curve with the dashed line represents the trend over time of the torque value (relative to the boat 5 roll axis A3) which generates rolling. The sine curve with the continuous line represents the trend over time of the torque (again relative to the boat 5 roll axis A3) generated by the thrust produced by the fins 3. Therefore, in this case the fins 3 move according to a mode which may be defined as harmonic active. The stretch labelled p is the rolling period. According to the operating method illustrated by way of example in Figure 7, the force generated on the axis of the fin 3 is obtained not by the reaction of water on the fin but due to the prevalent effect of the fin 3 lift P.

In other words, assuming that the boat 5 is stationary, and therefore the water in which it is immersed is also substantially stationary, the relative movement between the fin 3 and the water is generated by rotation of the fin 3 about the second axis A2,

This is substantially the operating principle of the Voith-Schneider cycloidal propeller systems referred to earlier in this text.

With a single fin 3, it is again appropriate to synchronise rotation of the fin 3 about the second axis A2 with the main rolling motion of the boat. In this way, with reference to Figure 7, with a clockwise rotation of the main body 4, at the position

A, thanks to the fin 3 lift P, a vertical thrust is obtained which is directed downwards.

Also with reference to Figure 7, and still assuming that the optimum direction of the thrust to be applied to balance the rolling motion is vertical, the control unit uses the motor means and controlled rotations of the fin 3 about the first axis Al, to minimise the lift components which are not parallel with the vertical direction.

At the position labelled B in Figure 7, the fin 3 substantially does not generate any lift but, as the body 4 continues rotating clockwise about the second axis A2, when the fin 3 reaches the position labelled C and diametrically opposed to the position A₅ the lift P generated is concordant with that generated in A, then is substantially cancelled out when, as the rotation continues, the position labelled C is reached.

Advantageously, as is also qualitatively illustrated in the graph in Figure 8, angular rotation of the fins 3 of the two propulsion units 2 of the boat 5 (one on the right and the other on the left relative to the roll axis A3) and rotation of the respective bodies 4 about their second axes A2 are driven by the motor means in a synchronised fashion, using the control unit. hi other words, since in the period of time between one active phase (for example the position A) of generating lift and the next (the position C) of a fin 3 belonging to a propulsion unit 2 (for example on the right), the torque opposing the rolling motion is absent, the control unit simultaneously rotates the fin 3 belonging to the other unit 2 (on the left) about both of the axes Al and A2 so that, during said period of time, said fin 3 generates a respective lift P whose effect contributes to an overall torque force which opposes the rolling motion. The graph in Figure 8, which represents the torque values over time, provides a qualitative indication of the contribution to the total torque Ct opposing the rolling motion provided, respectively, by the fin 3 of the left-hand unit 2, labelled Csx, and by the fm 3 of the right-hand unit 2, labelled Cdx. The operating mode just described, due to its characteristics, may be defined asynchronous active.

As illustrated in Figure 11, with reference to a passive operating mode, with the boat moving, the fins 3 a, 3b are positioned in such away that they are paired to best exploit the hydrodynamic effects and increase the overall lift Pa+Pb which can be obtained.

The effect obtained, in the passive operating mode, with two paired fins 3 a, 3 b is not dissimilar to that obtained by fitting an aerodynamic surface with an aileron.

Again with reference to Figure 11, the two fins 3 a, 3 b are positioned and angled in such a way that the rear fin 3 b, relative to the hydrodynamic flow Fi striking at a predetermined moment of relative movement between the fins 3 a, 3 b and the fluid, acts like an aileron with an increase in lift compared with that which could be obtained with a fin having the total surface area equal to the sum of those of the individual fins 3a, 3b.

According to methods not illustrated but in any case identical to those just described, the same increase in lift is exploited, in the units 2 equipped with paired fines, when they are operating in the asynchronous active mode.

Figure 12, easily understood with reference to the similar descriptions above relating to the figure and reference characters already used, illustrates a propulsion unit 2 equipped with paired fins 3a, 3b, in the harmonic active operating mode. Figures 13 and 14, on the other hand, illustrate the alternative embodiment of the propulsion unit 2 comprising two fins' 3a, 3b which are positioned so that they are diametrically opposed to each other relative to the second axis A2. In particular, Figure 13 illustrates the unit 2 in the passive operating mode, with the fins 3 a, 3 b exposed to the hydrodynamic flow Fi. Figure 14 illustrates the unit 2 in the asynchronous active operating mode. As already indicated, Figures 15 and 16 show another embodiment of the propulsion unit 2 in which the unit 2 comprises two pairs of fins 3a, 3b and 3a', 3b' which are paired.

In particular, Figure 15 illustrates the unit 2 in the passive operating mode, with the fins 3a, 3b and 3a', 3b' exposed to the hydrodynamic flow Fi. Figure 16 illustrates the unit 2 in the asynchronous active operating mode.

The main advantage of the device disclosed is that, with different operation of the motor means which control the movement of the fins, it allows the rolling motion of boats to be compensated for, both when they are moving and when they are stationary.

In this way, the boat 5 is stabilised relative to the rolling motion.

The invention described above is susceptible of industrial application and may be modified and adapted in several ways without thereby departing from the scope of the inventive concept. Moreover, all details of the invention may be substituted by technically equivalent elements.

Advantageously, the positioning of two propulsion units 2 on the stern of the boat and two other propulsion units 2 on the bow of the boat, under the control of the control unit, allows the boat to also be stabilised relative to the pitching motion.

Claims

1. A stabilising device for boats, comprising at least two propulsion units (2) emerging from a hull of the boat and positioned on opposite sides of a boat longitudinal axis (A3), each of the propulsion units (2) comprising at least one fin (3) and motor means for rotating the fin (3) both about its first axis (Al) of longitudinal extension, and about a second axis (A2) outside the fin (3), there being the possibility of driving the rotations about the first axis (Al) and about the second axis (A2) independently of each other.

2. The device according to claim 1, characterised in that it comprises a control unit for the motor means, said control unit comprising means for measuring the boat (5) instantaneous angle of roll relative to a horizontal reference plane.

3. The device according to claim 2, characterised in that the measuring means comprise an inclinometer.

4. The device according to claim 2, characterised in that the measuring means comprise an accelerometer.

5. The device according to any of the claims from 1 to 4, characterised in that each propulsion unit comprises two fins (3 a, 3 b) positioned so that they are diametrically opposed to each other relative to the second axis (A2).

6. The device according to any of the claims from 1 to 4, characterised in that each propulsion unit comprises two fins (3a, 3b) whose respective first axes (Al) are separated by an angle relative to the second axis (A2), said angle being less than 180°.

7. The device according to claim 5, characterised in that the angle is less than 90°.

8. A use of the device according to any of the claims from 1 to 6, to generate a lift (P) opposing the rolling motion, both while the boat is moving and therefore navigating, and when the boat stops and so is stationary.