Centreboard unit for a sail boat

The present invention rφfers in general to sail boats, and more specifically to sail boats in which the hull is associated with a movable centreboard.

In sail boats, it is common to use vertically movable centreboards, such as dagger boards, which can traslate to change the extension of their immersed portion, or centreboard rotatable about a horizontal axis. The vertical movement of such centreboards allows the draught of the boat to be changed, in particular to reduce it, and it also allows a deep centreboard to be available during navigation, which is therefore effective. Moreover, lifting of the centreboard is useful to adjust its action depending on the sailing point and the force of the wind, being well known that close hauled requires a greater centreboard surface rather than that necessary in broad reaches or down wind. Instead, in most common boats provided with a fixed centreboard, the surface of the centreboard is necessarily the same in all circumstances .

Sail boats provided with a centreboard unit of the type defined in the preamble of appended claim 1, are also known.

These boats, for example disclosed by FR-A-2 376 787, US-A-3 903 827, US-5 163 377 and US-A-5 280 760, comprise a deep keel which may swing about a longitudinal axis parallel to the waterline, to allow the movement of the ballast windward in order to increase the righting moment of the boat, which is needed for balancing the action of the wind on the sails. Usually, a lever arm is associated with such a type of centreboard, commonly called kanting keel, which arm extends

inside the hull and allows the rake of the centreboard to be controlled.

The object of the present invention is to provide a centreboard unit of the type defined above, having characteristics of greater versatility of use and of better adaptability of the action of the centreboard to various sailing points of the boat.

This object is reached by a centreboard unit having the features mentioned in appended claim 1.

By virtue of such characteristics, the centreboard unit of the invention allows the action of the centreboard to be adjusted in a more accurate manner, depending on the force of the wind and the sailing point (therefore of the angle of course with respect to the wind) .

According to a first advantageous aspect of the invention, the centreboard unit comprises moving means for moving the centreboard in a direction transverse to said axis of rotation, in order to modify the extension of the immersed portion of the centreboard.

In this manner, both the righting moment caused by the windward movement of the ballast, resulting from rotation of the centreboard, and the immersed surface of the centreboard, can be modulated with a better effectiveness, depending on the sailing point of the boat.

Moreover, this arrangement allows, when it is needed, the draught of the boat to be reduced, for example close to shoals .

According to an other advantageous aspect of the invention, the axis of rotation of the centreboard is tilted of a predetermined angle with respect to the waterline of the boat, in such a manner that a rotation of the centreboard with respect to said axis causes also a positive incidence of the centreboard with respect to the advancing direction of the boat, so that, during navigation, it originates a lift applied to the centreboard and a resulting reduction of the drift angle of the hull.

In this manner, the centreboard unit of the invention is able to carry out a hydrodynamic action, also with a small tilt of the axis of rotation thereof with respect to the waterline of the boat, which involves a reduction of the drift angle of the hull and which improves, therefore, the performances of the boat particularly in close hauled sailing points, so that the overall drag of the boat in navigation is reduced.

Further characteristics and advantages of the invention will be made more clear from the following detailed description, provided as a non-limitative example and referred to the appended drawings in which: figure 1 is a schematic front elevational sectioned view of a boat provided with a centreboard unit according to a first aspect of the invention, in a first configuration of use, figure 2 is a schematic top elevational view from arrow

II of figure 1, figure 3 is a schematic side elevational view from arrow

III of figure 1,

figures 4 to 6 are views respectively similar to figures 1 to 3, of a second configuration of use of the centreboard unit according to the first aspect of the invention, figures 7 and 8 are views respectively similar to figures 1 and 2, of a third configuration of use of the centreboard unit according to the first aspect of the invention, figures 9 and 10 are views respectively similar to figures 1 and 2, of a fourth configuration of use of the centreboard unit according to the first aspect of the invention, figure 11 is a schematic side elevational view similar to figure 6, which shows guide means for guiding the transverse movement of the centreboard, figure 12 is a view similar to figure 1, of a modification of the first aspect of the invention, in a first configuration of use, figures 13 and 14 are schematic side elevational views from arrow XIII, XIV of figure 12, which show embodiments of the modification of the first aspect of the invention, respectively, figures 15 to 17 are schematic views similar to figure 12, showing configurations of use analogous to figures 4, 7 and 9, respectively, of the modification of the first aspect of the invention, figure 18 is a schematic side elevational view similar to figure 6, referring to a second aspect of the invention, and figure 19 is a view similar to figure 18, in another configuration of use.

With reference to the figures, the hull of a boat, generally indicated 10, has a waterline corresponding to the water

surface in stationary conditions, which is indicated 12. The keel line of the boat 10, which extends fore and aft and is defined by the intersection of a vertical and longitudinal midplane of the hull with its bottom, is indicated 14.

A centreboard unit associated with the hull 10 includes a movable centreboard 16 the cross-section of which is typically shaped as a wing contour, which is provided with a ballast 18, having for example the shape of a bulb, fixed to the lower end of the centreboard 16.

According to a first aspect of the invention, and with specifical reference to figures 1 to 11, an elongated body 20, for example a spindle-shaped body such as shown in the figures, is rotatably and sealingly mounted in a respective case close to the keel line 14 and at a longitudinal lower opening of the hull 10, which is constrained so as to rotate about the longitudinal axis of the boat. In particular, the ends 20a and 20b, forward and astern, respectively, of the body 20, are articulated about a common axis A which coincides with the axis of the body 20 and extends parallel to the waterline 12, so that it lies in the longitudinal midplane of the boat.

The body 20 has a through transverse cavity 22, the shape of which corresponds to that of the profile of an upper portion 17 of the centreboard 16, the portion 17 being substantially cylindrical. The portion 17 of the centreboard 16 is slidably and sealingly mounted in the cavity 22, and crosses also the bottom opening of the hull 10.

In this manner, the centreboard 16 can rotate together with the body 20 about the axis A, in order to cause the lateral

O

movement of the ballast 18 with respect to the longitudinal midplane of the hull 10, and it may also slide with respect to the body 20 in the cavity 22, in order that it undergoes a movement transverse to the axis A with the aim of changing the extension of its immersed portion, also during navigation.

A pair of actuators 24 and 26, typically of the single-acting or double-acting fluid type, which can be controlled by pumps through a hydraulic circuit, may be provided to control the swing and translation movement of the centreboard 16, one end of said actuators being articulated at 28, for example at the upper end of the centreboard 16, and their opposite end being articulated to the hull 10, for example between a pair of floors, respectively at 30 and 32, about respective articulation axes parallel to the axis A.

The actuators 24 and 26 may be driven in a co-ordinated manner by changing their extension in order to obtain the rotation of the centreboard 16 about the axis A and/or its movement transverse to the axis A, so as to change the extension of the immersed portion of the centreboard. In such a manner, all desired combinations of movement may be obtained, to adjust the rake and depth of the centreboard 16.

In particular, the centreboard 16 may take on a vertical configuration lifted with respect to the keel line 14 (figures 1 to 3) , a vertical configuration lowered with respect to the keel line 14 (figures 4 to 6), a raked configuration lowered with respect to the keel line 14 (figures 7 and 8), a raked configuration lifted with respect to the keel line 14 (figures 9 and 10), and all other intermediate or symmetrical positions with respect to those

shown .

In a cruising boat of medium dimensions, the centreboard unit of the invention may be dimensioned so as to be settled under a table usually provided in the lounge, in order that it does not hinder the inner spaces and does not compromise habitability of the boat. That could involve a limitation of the transverse stroke of the centreboard 16 to about 70 cm, which would be at any rate enough to adjust significantly the draught of the boat between its overall lifted configuration and its overall lowered configuration.

In a racing boat, the transverse movement of the centreboard may be greater, to allow a wider adjustment of the extension of the immersed portion of the centreboard 16, depending on the sailing point and on the force of the wind.

Preferably, guide means are associated with the centreboard 16 and with the body 20, to guide the movement of translation of the centreboard 16 with respect to the cavity 22 of the body 20, in such a manner that its movement takes place by a mere translation, without any undesired angular movement.

Conveniently, these guide means comprise a pair of linear guides 38 (only shown in figure 11, in which one of the two guides can be seen) connected to the body 20 and, for example, fastened to the body 20 through bracing members or tension bars 40, which guides engage corresponding formations on the sides of the centreboard 16 (not shown) .

The position of the centreboard 16 with respect to the hull 10 can be controlled during navigation in order to affect the attitude of the boat. For this purpose, an electronic control

unit (not shown, since it is in the capacity of skilled person) may be convenientely provided on the boat to control the actuators 24 and 26, which is connected to a control panel adapted to receive values of the rake angle and of the depth of immersion of the centreboard 16 set by a user, and that, depending on the set values, is able to calculate the extension of the actuators 24 and 26 corresponding to the attitude required for the centreboard 16, and to drive, as a result, the actuators 24 and 26.

According to a modification of the present aspect of the invention shown in figures 12 to 17 in which the same numeral references have been used to indicate parts equal or similar to those described previously, a pair of plate appendages 23 are associated with the body 12, that extend sideways with respect to the centreboard 16 from the side of the body 20 opposite to the hull 10, the actuators 24 and 26 being articulated at 29 to said appendages 23, respectively, in order to control the lateral swing of the body 20 and, together with it, the swing of the centreboard 16 about the axis A.

Two auxiliary actuators 42 are also associated to the appendages 23 and to the centreboard 16, which are also typically of the type controlled by fluid. In particular, each of the auxiliary actuators 42 has an end connected to the centreboard at 44, for example at its upper end surface, and the opposite end connected to an auxiliary frame 27 fast to the body 20. By driving the auxiliary actuators 42 it is possible to control the transverse movement of the centreboard 16 and, in the arrangement shown in figure 14, to guide its translational movement with respect to the hull 10.

The pair of actuators 42 provided on each side of the centreboard 16 may be arranged according to a parallel configuration (figure 13) or according to a tilted configuration converging towards a common point of connection (figure 14 ) .

The modification of figures 12 to 17, even though more complex with respect to the previous one, has the advantage that it allows a greater amplitude and independence of the movements of rotation and translation of the centreboard 16, as well as that actuators with more extensions can be used, which are characterized by longer strokes, also of the single-acting type.

In the present modification also, the centreboard 16 may undergo a rotation about the axis A and/or a transverse movement with respect to the keel line 14, as a result of the combined driving of the actuators 24, 26 and 42, in order to take on a vertical and lifted configuration (figure 12), a vertical and lowered configuration (figure 15), a raked and lowered configuration (figure 16) , a raked and lifted configuration (figure 17), as well as all other intermediate or symmetrycal positions with respect to those shown.

According to an other aspect of the invention, and with reference to figures 19 to 18 in which the same numeral references have been used to indicate parts equal or similar to those of the aspect previously described, the elongated rotatable body, here indicated 21, is articulated about an axis B which is arranged tilted with respect to the longitudinal axis of the hull, in such a manner that its forward end 20a is raised with respect to its astern end 20b.

The centreboard 16 associated to the body 21, which extends through the opening formed at the bottom of the hull 10, may rotate together with the body 21 about the axis B.

In the neutral configuration of the centreboard 16, that is in its not swung and vertical configuration, it lies in the midplane of the hull 10 and its incidence is null with respect to the longitudinal axis of the boat.

When the centreboard 16 is rotated about the axis B, with a resulting lateral movement of the ballast 18, owing to tilting of its axis, it takes on an incidence with respect to the longitudinal axis of the boat, which is a function of its angle of swing with respect to the longitudinal midplane of the boat, that is with respect to the vertical neutral position. When the boat is in motion, this incidence generates a hydrodynamic lift applied to the centreboard 16, also in the absence of a leeway.

In the common sail boats it is necessary that the boat, in all sailing points except for stern wind, sails with a certain leeway, namely that the direction of its motion is not exactly parallel to the longitudinal axis of the boat. In fact, the plane of the centreboard is parallel to the longitudinal axis of the hull and therefore, in order that the centreboard may take on a positive incidence with respect to the motion, which is needed for generating the lift, it is necessary that also the hull takes on a small angle of incidence with respect to the motion, which is just called leeway.

The measure of tilting the axis B of rotation of the rotary body 21, such as previously described, allows that an

incidence with respect to the hull is applied to the centreboard when it is rotated, which adds to the leeway angle. Therefore, being the lift of the centreboard the same, the leeway angle is reduced (possibly so much that it may be nullified) .

For example, if the axis B of the body 21 is tilted of about 6° with respect to the waterline 12, and the rake of the centreboard 16 is for example 35° with respect to its neutral position, the centreboard 16 takes on a positive incidence of about 3.4° with respect to the longitudinal axis of the boat, by virtue of which, during navigation, a lift is originated, the transverse component of which allows the drift angle of the hull to be effectively opposed and the leeway and the drag of the boat to be reduced considerably in comparison with a boat having a traditional fixed centreboard.

The present aspect of the invention is particularly favourable since, in close-hauled, in which the centreboard 16 is preferably rotated of a wide angle with respect to the midplane of the boat in order to carry the ballast 18 windward so as to have a high righting moment, the angle of incidence of the centreboard 16 is more marked and therefore it causes a considerable effect of reduction of the leeway, while in sailing points in which the centreboard 16 is closer to its neutral position, typically in broad reaches, the angle of incidence of the centreboard 16 is small, until it nullifies when the centreboard 16 is exactly in its neutral configuration.

To control the swing of the centreboard 16 in the unit according to this aspect of the invention, a pair of actuators may be used which are analogous to the actuators 24

and 26 of the first modification of the first aspect described above, by using conveniently ball joints at the articulation points of the ends of the actuators 24 and 26.

Moreover, the body 21 may have the through cavity 22 described with reference to the previous aspect of the invention, in which case the centreboard 16 is slidably and sealingly mounted in the direction transverse to the keel line 14 in such a cavity of the body 21, such as indicated by arrow C of figure 19, in order to be able to take on a series of positions for changing the depth of the immersed portion thereof. In this case, measures and devices equal or analogous to those described above with reference to the previous aspect of the invention, could be used for controlling also the transverse movement of the centreboard 16 with respect to the body 21.