Mainmast of a sailing boat

Abstract

A mainmast (21) for a sailing boat (1) has a support base (S) and an upright (P), which extends along an axis from the support base (S) and defines an airfoil symmetrical with respect to an ideal median plane (M), with a leading edge (50) and two convex surfaces (21a,21b) that extend from the leading edge (50); the upright (P) can be oriented about its axis with respect to the support base (S), in order to position, in use, the leading edge (50) with respect to an incident air flow; the upright (P) has a lower portion (P1) and an upper portion (P2), which supports two slats (52a,52b), symmetrical to each other with respect to the ideal median plane (M), in positions spaced apart from the convex surfaces (21a,21b), respectively, so as to define respective slots.

Description

The jib 26 (therefore the aerofoil Q2) is instead arranged in front of the jib 25, precisely between the latter and the bow 12 . The jib 26 defines a slot 28 of given dimensions with the jib 25 (Figures 1 and 2). Preferably, with reference to Figure 1, the jib 25 comprises: - a support element 29 with an elongated geometry along a respective main direction A having a prevalent extension with respect to the other dimensions, arranged in front of the mainmast 21 and protruding upwards with respect to the hull 11 along the aforementioned main direction A; - a plurality of ribs 31, each defining a respective aerofoil QI and carried transversally in a cantilevered manner by the support element 29 in parallel positions and spaced apart from one another along the main direction A of extension of the support element 29; and - a sail 33 fitted on the ribs 31 in the manner of a bag open at its opposite ends so as to form a respective closed loop around the ribs 31. In the illustrated case, the aerofoils QI of the ribs 31 have dimensions that gradually taper upwards, to be fitted by a triangular sail 33; according to a possible alternative not illustrated, the aerofoils QI of the ribs 31 could also have constant dimensions. Similarly to what has been shown for the jib 25, the jib 26 also preferably comprises: - a support element 30 with an elongated geometry along a respective main direction B having a prevalent extension with respect to the other dimensions, arranged in front of the mainmast 21 and the support element 29 and protruding upwards with respect to the hull 11 along the aforementioned main direction B; - a plurality of ribs 32, each defining a respective aerofoil Q2 and carried transversally in a cantilevered manner by the support element 30 in parallel positions and spaced apart from one another along the main extension direction B of the support element 30; and - a sail 34 fitted on the ribs 32 in the shape of a bag open at its opposite ends forming a respective closed loop around the ribs 32. In the illustrated case, the support elements 29, 30 are defined by forestays that connect a portion of the upper end 21c of the mainmast 21 to a portion of the bow of the hull 11. The main directions A, B having prevalent extension of the support elements 29, 30 are therefore oblique with respect to the vertical axis Z and transverse with respect to the plane identified by the longitudinal axis X and transversal axis Y. Preferably, the sailing boat 1 comprises, furthermore, one or more actuators (not illustrated) to move the ribs 31, 32 and / or the support elements 29, 30 along planes transverse to the longitudinal axis X and to the vertical axis Z. In the illustrated case, a first actuator is used to move the support element 29 and a second actuator, different from the first, to move the support element 30. Preferably, the support elements 29, 30 engage respective through grooves 39, 40 obtained in the deck 16 and shaped like cams to define the movement trajectories of the support elements 29, 30. The positions obtainable by the support elements 29, 30 and therefore by the ribs 31, 32 and by the respective jibs 25, 26 along the trajectories defined by the grooves 39, 40 are schematically illustrated in Figure 2. Said positions can be varied according to the direction of the apparent wind during navigation. In particular, in the case of tacking or jibing, the profiles QI, Q2 can be oriented towards the wind on the opposite tacks . The effect of this preferred configuration of the jibs 25,26 is to orient the aerodynamic load vector more along the advancement direction V of the sailing boat 1. In practice, the curvature of the airfoil defined by the assembly of sails is advanced in front of the mainmast 21, at the jibs 25, 26, thus creating a profiling continuity with the mainsail 22. According to an aspect of the present invention, as schematized in Figure 3, the lower portion Pl of the upright P is mounted on the support base S so as to be rotatable about the axis Z. In other words, the upright P can be oriented with respect to the support base S (and therefore with respect to the surrounding space) about the axis Z using known techniques, for example by operating an actuator 51 (schematically illustrated) carried by the support base S and / or arranged below deck in Figure 3) . In this way, it is possible to adjust the position of the leading edge 50 of the airfoil of the upright P as a function of the angle of incidence of the air flowing towards the upright P, in order to optimize the aerodynamic conditions of the air flow along the surfaces 21a and 21b. In particular, this adjustment of orientation about the axis Z is performed as a function of the configuration of the jib 25, which determines the angle of incidence of the air flowing in the slot 27 towards the leading edge 50 at the lower portion Pl of the upright P. In particular, the jib 25 has a height that is less than the one of the mainmast 21, so it influences the angle of incidence of the air flow only for the lower portion Pl, but not for the remaining part of the upright P, defined by an upper portion indicated with the reference P2 in Figures from 3 to 6. The upper portion P2, in fact, is impacted by a free air flow, which is substantially not influenced by the presence of the jibs 25 and 26. In this regard, considering Figure 4 and the cross section in Figure 5, it can be noted that the jib 26 extends higher than the jib 25, but the upper end of the jib 26 is relatively distant from the upright P, so it does not tend to influence the direction of the air flow towards the upper portion P2 . Given the considerable height of the mainmast 21 (typically around 15 meters, for example), the air flow that impacts the upper portion P2 of the upright P tends not to be influenced even by aerodynamic resistance and / or boundary layer effects caused by the surface of the Earth, namely, by the free surface of the sea on which the sailing boat 1 is travelling. Consequently, as mentioned above, the conditions of the air flows directed towards the airfoil of the upright P are different depending on the height position along the upright P. To overcome the different directions of incidence of said air flows, according to the present invention the mainmast 21 comprises two slats 52a and 52b, defined by respective rigid elements that are elongated in directions parallel to the axis Z, are arranged exclusively at the upper portion P2 of the upright P, and are fixed to the upper portion P2 in positions spaced apart from the surfaces 21a and 21b, so as to define respective slots 53a and 53b (Figure 6) with respect to said surfaces 21a and 21b. At the same time, the lower portion Pl does not support any slats. The slats 52a and 52b are symmetrical to one another with respect to the plane M, so as to make the behaviour of the airfoil of the upper portion P2 of the upright P equal in the case of starboard tacks and port tacks. For example, each of the slats 52a and 52b is fixed in a cantilever manner to the upper portion P2 of the upright P, by at least two legs, provided for example at the lower end and at the upper end of the same slat 52a,52b. According to not illustrated alternatives, the slats 52a, 52b could be defined by substantially rigid elements, for example by plates, which are movable between a close position and a spaced position with respect to the upper portion P2 of the upright P, preferably independently of one another, under the action of an actuator mechanism arranged inside the upright P, namely, with an activation and deactivation movement similar to the one which occurs for the slats usually provided for lifting wings in the aeronautic field. Preferably, the rigid, or substantially rigid, elements defining the slats 52a and 52b have a cross-section with position, shape and dimensions that are invariant at the different heights of the upper portion P2 of the upright P. However, the crosssections of the slats 52a, 52b could also be designed with variations along the axis Z with regard to position and / or shape and / or dimensions. As illustrated in a simplified way in the example of Figure 6, the slat 52b is arranged downwind and performs a guiding function that channels the air flow into the respective slot 53b, thus counteracting the tendency for the air flow to detach from the respective surface 21b and therefore counteracting the stalling of the airfoil at the upper portion P2 of the upright P. In other words, the slat 52b allows to increase the angle of incidence of the air flow with respect to the leading edge 50, at the upper portion P2 where it is mounted, without incurring stalling phenomena of the airfoil. The same situation obviously occurs when the slat 52a is the one arranged downwind. It is therefore evident that slats 52a and 52b allow the operating range of the airfoil of the upper portion P2 of the upright P to be extended, in relation to the angle of incidence of the air flow directed towards the leading edge 50. In other words, the stall conditions are moved away towards greater angles of incidence compared to the case in which slats 52a and 52b were absent. Thanks to this extension of the operating range of the airfoil of the upper portion P2, it is possible to set the orientation of the upright P about the axis Z so that the airfoil of its lower portion Pl is optimized for the flow conditions caused by the jib 25, without losing aerodynamic efficiency at the upper portion P2. At the same time, the extension of the operating range with respect to the angles of incidence of the air flows at the upper portion P2 allows to better deal with gusts of wind with variations in direction, as well as the small and continuous adjustments of course normally associated with the rudder command during a sailing competition. The preferred solution presented is also extremely simple, and easy to install. Finally, it is clear that modifications and variations can be made to the mainmast 21 and to the sailing boat 1 described and illustrated herein with reference to the attached figures without going beyond the scope of protection defined by the following claims. In particular, the presence of slats 52a, 52b on the upper portion P2 of the mainmast 21 is independent of the type and number of jibs that are provided in front of the mainmast 21 (for example, the jib sails could be of the traditional type, without ribs). Furthermore, slats 52a and 52b could be useful even without the use of any jib in front of the mainmast 21, in order to compensate for differences in the angle of incidence of the apparent wind on the leading edge 50 of the upright P, depending on the height of the latter, due to the boundary layer effects caused by the sea surface, which tends to change the wind conditions compared to those at the upper end of the mainmast 21. Furthermore, the external profile of the slats 52a, 52b could be different from the one illustrated in the attached figures as an example. Furthermore, as mentioned above, while maintaining mutual symmetry with respect to the plane M, the position of the slats 52a and 52b with respect to the surfaces 21a and 21b (as well as the shape and / or size of the cross-section of the slats 52a and 52b) could vary as the height along the upper portion P2 varies, so they may not be perfectly parallel to the axis Z. Finally, the axis of the upright P may not coincide with the yaw axis of the boat 1 and / or may not be straight: for example, the upper portion P2 could be canted towards the stern.

Claims

1.- A mainmast (21) for a sailing boat (1), the mainmast comprising:a) a support base (S) suitable to be fixed with respect to a hull (11) of said sailing boat (1);b) an upright (P) , which extends along an axis from said support base (S), comprises a lower portion (Pl), adjacent to said support base (S) , and an upper portion (P2) , opposite to said lower portion (Pl) along said axis, and defines an airfoil having a leading edge (50) and two convex surfaces (21a,21b);wherein said convex surfaces (21a,21b) extend from said leading edge (50) symmetrically to each other with respect to an ideal median plane (M), on which said leading edge (50) and said axis lie ;wherein said lower portion (Pl) is rotatable about said axis with respect to said support base (S) to orient said upright (P) and, therefore, said leading edge (50);wherein the mainmast further comprises two slats (52a,52b) symmetrical to each other with respect to said ideal median plane (M);characterized in that said slats (52a,52b) are arranged exclusively at said upper portion (P2) and so as to be spaced respectively from said convex surfaces (21a,21b) and, therefore, define respective slots (53a,53b).2.- The mainmast according to claim 1, wherein said slats (52a,52b) are fixed with respect to said upper portion (P2).3.- The mainmast according to claim 1 or 2, wherein said slats (52a,52b) are defined by respective substantially rigid bodies.4.- The mainmast according to any one of the preceding claims, wherein said slats (52a,52b) are parallel to said axis.5.- The mainmast according to any one of the preceding claims, wherein said slats (52a,52b) have a cross-section having an invariant position with respect to said convex surfaces (21a,21b) as the height varies along said upper portion (P2).6.- The mainmast according to any one of the preceding claims, wherein said slats (52a,52b) have a cross-section having an invariant shape as the height varies along said upper portion (P2 ) .7.- The mainmast according to any one of the preceding claims, wherein said slats (52a,52b) have a cross-section having invariant dimensions as the height varies along said upper portion (P2).8.- The mainmast according to any one of the preceding claims, wherein a mainsail (22) is hoisted on the mainmast.

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