Improved mast, in particular for sailboards

Abstract

 Mast with an improved structure, in particular for sailboards or the like, comprising one or more tubular elements having a progressively variable diameter, the body portion of said elements being made by winding fibre sheets impregnated with synthetic resins on a mandrel.
Each such tubular element (3) of the mast has two sectors (4) arranged in opposition and symmetrically relative to the plane of the sail (2), which are provided with reinforcements imparting a degree of flexural rigidity to the mast that is greater in the plane (B) perpendicular to the sail plane than the degree of flexural rigidity in the sail plane (A).

Description

[0001] The present invention refers to a mast with an improved structure, adapted for use in conjunction in particular with sailboards, but more generally also with other small boats or the like.

[0002] Usually, masts used to sustain sails have a circular or, anyway, somehow rounded cross-sectional shape, the diameter of which is gradually decreasing, i.e. becomes progressively smaller starting from the base at which it is attached to the deck of the boat, or the board, and moving towards the tip or highest extremity thereof. Various kinds of materials are used to manufacture these masts, and these include aluminium, glass-reinforced or carbon-reinforced plastics and fibrous materials. In all cases, masts are however requested to comply a number of mutually clashing requirements, such as lightness on the one side and great strength to aerodynamic stresses and loads on the other one.

[0003] One of the main properties that a mast is required to possess is a rigidity that enables it to maintain the sail in the intended form and shape designed in view of ensuring the highest possible aerodynamic or wind utilization efficiency. Any distortion or deformation in the mast means a corresponding deformation in the sail and, as a result, a corresponding drop in performance levels. In particular, this results in a lower propelling force and a smaller capacity to stem or pick up the wind.

[0004] Currently, masts for use in conjunction with sailboards are characterized by a number, i.e. the so-called IMCS (or Index Mast Control System), and two curvature ratios, or coefficients, defining the curvature and the rigidity thereof.

[0005] Another characteristics of masts for sailboards is the so-called "reflex", i.e. the response capacity of the mast in returning the energy absorbed or taken up by it during a deformation brought about by a temporary load or stress.

[0006] Various kinds of differently reinforced masts have been proposed in the art.

[0007] For example, the US patent publication No. 3,765,360 describes a mast with a wooden, cross-shaped inner structure and an outer body portion of thermoplastic material having a substantially oval cross-section. Reinforcing metal wires are wound round the body portion of the mast. This kind of construction, however, turns out as being quite complex, owing in particular to the use of a number of different materials; furthermore, the purpose and the related advantage of such construction lie in differentiating the weight and the strength of the mast along the longitudinal thereof.

[0008] The US patent publication No. 4,501,214 describes in turn a mast with a rounded-up rectangular cross-section, which is constructed with a glass-reinforced polyurethane foam core clad with laminated fibreglass. This mast is intended to ensure a minimum extent of aerodynamic resistance and a maximum extent of rigidity and tenacity, i.e. strength to rupture. In particular, the mast cross-section has its major axis (oriented in the forward direction) with a length that amounts to at least 2.5 times the length of the minor axis thereof, so that the flexibility of the mast turns out as being higher in the direction of said minor axis.

[0009] Disclosed in EP 0 305 674 is a mast for sailboards, which features, for approximately one third of its total length, an oval cross-section having the major axis thereof extending parallel to the sail, whereas for the remaining two thirds of its length it has an oval cross-section with the major axis thereof extending orthogonal to said major axis of the first section. The section with a greater length extends from the base of the mast and is arranged with the major axis parallel to the forward direction, whereas the section with a shorter length forms the upper end portion of the mast and the major axis thereof is orthogonal to the forward direction.

[0010] A largely felt problem in connection with this kind of masts lies in the ability of providing a degree of rigidity in the forward direction of the sailboard, which is different from the degree of rigidity in a transverse direction, i.e. a direction across the forward one. Up to now it has been practically impossible for particularly rigid masts to be made without affecting or impairing the afore-cited required IMCS property.

[0011] It is therefore a main purpose of the present invention to provide a mast for sailboards or the like, which has a flexural rigidity that is free of axial symmetry, the purpose being in particular to obtain a flexural rigidity of the mast which is smaller in the plane of the sail and greater in the plane extending orthogonally thereto.

[0012] A further purpose of the present invention is to provide a mast for sailboards or the like, that has as advantageous as possible an IMCS feature.

[0013] Yet another purpose of the present invention is to enable masts with such improved properties to be provided by using materials and manufacturing or processing techniques of a traditionally and widely known kind, so as to avoid affecting production costs to any significant extent.

[0014] According to the present invention, these and further aims are reached in a mast having an improved structure as defined and recited in the appended claims 1 et seq.

[0015] Anyway, features and advantages of the present invention may be more readily understood from the description that is given below by way of nonlimiting example with reference to the accompanying drawings, in which:

• Figure 1 is a schematical view of a sailboard in a static condition;
• Figure 2 is schematical cross-sectional view of a mast for the sailboard shown in Figure 1, according to a first embodiment of the present invention;
• Figure 3 is schematical cross-sectional view of a mast for the sailboard shown in Figure 1, according to a second embodiment of the present invention;
• Figure 4 is schematical cross-sectional view of a mould used to produce a mast for sailboards according to the present invention.

[0016] As Figure 1 can be noticed to illustrate, a sailboard is largely known to be substantially comprised of a hull or board 1 and a sail 2. The latter is sustained by and attached to a mast 3, which is mounted on said hull via an articulated joint enabling the mast to pivotally move about the point at which it is attached to the hull. Also shown schematically in Figure 1 are the plane A of the sail and the plane B, which is orthogonal to said sail plane.

[0017] The mast 3 is usually made out of one or more tubular elements having a progressively variable diameter; the mast section having the largest diameter is the one that lies closer to the point at which the mast connects with the hull, whereas the mast section having the smallest diameter is the one corresponding to the upper end portion of the mast. The structure of the mast is generally produced by winding one or more sheets of fibres impregnated with synthetic resins on a mandrel. This may then be followed by a variety of finishing operations aimed at imparting special properties to the surface of the mast.

[0018] According to the present invention, the mast 3 is characterized in that the cross-section thereof has two sectors, opposing the plane of the sail and symmetrical relative thereto, which are reinforced so as to impart a degree of flexural rigidity to the mast that is greater in the plane B perpendicular to the sail plane than the degree of flexural rigidity in the sail plane A. This feature may be obtained in a variety of manners.

[0019] A first solution (Figure 2) calls for the thickness of two sectors of an arc, which are diametrically opposed relative to the plane of the sail, to be increased through the insertion of reinforcement layers 4 between the sheets of fibres forming the structure of the mast as these sheets are being wound round the mandrel. The number, the sizing and the material of these reinforcement layers 4 must be determined in accordance with the required rigidity, which depends on the dimensional and performance characteristics of the mast.

[0020] A second solution (Figure 3) calls for the structure of the mast to be made with the use of impregnated fibre sheets having differentiated mechanical properties, in particular having a different modulus of elasticity (i.e. Young's modulus) for different, determined lengths or sections along the full extension thereof. In particular, these cloths will not be constituted by a homogeneous fabric, but will rather feature zones 5 having a higher modulus of elasticity in correspondence to those sectors requiring a greater rigidity.

[0021] A further solution is represented by a modification in the cross-sectional geometry of the mast 3. This practically calls for a structure to be provided, which has a cross-section featuring a differentiated thickness pattern, wherein this thickness is the largest one, i.e. reaches its peak 6 in the two sectors that are diametrically opposed relative to the plane A of the sail. As illustrated schematically in Figure 4, this solution may be embodied by introducing a simple variation in the geometry of the mould through the removal of part of the material thereof so as to enable correspondingly larger wall thicknesses of the mast 3 to be obtained. In this manner, the body portion of the mast turns out as having an ellipsoidal profile internally.

[0022] It will be appreciated that still further solutions may well be devised by those skilled in the art from the teachings of the present invention, without departing from the scope thereof.

[0023] It will also be readily appreciated that the above-described technical solutions may also be variously combined with each other in order to obtain a mast featuring ideal properties in view of the desired performance level to be reached.

[0024] The increase in the side flexural rigidity of the mast 3, therefore, has the ultimate result of both limiting the deformation of the mast, so as to constantly keep the sail in a condition of top efficiency, and increasing the afore-cited "reflex" property, thereby improving the response of the mast under variable loads such as wind blasts or stresses imparted by the athlete. All this translates into a quicker recovery of the mast to its optimum trim and form and a lesser extent of oscillations as the accidental load comes to an end.

[0025] Finally, it has been found experimentally that the above-described solution is effective in maintaining or even improving the rigidity characteristics that are required in the plane of the sail, i.e. the aforementioned IMCS property.

Claims

1. Mast with an improved structure, in particular for sailboards or the like, comprising one or more tubular elements having a progressively variable diameter, the body portion of said elements being made by winding fibre sheets impregnated with synthetic resins on a mandrel, characterized in that each such tubular element (3) of the mast has two sectors (4) arranged in opposition and symmetrically relative to the plane of the sail (2), which are provided with reinforcements imparting a degree of flexural rigidity to the mast that is greater in the plane (B) perpendicular to the sail plane than the degree of flexural rigidity in the sail plane (A).

2. Mast according to claim 1, characterized in that said sectors (4) are constituted by at least a reinforcement layer that is inserted longitudinally between the impregnated fibre sheets of the tubular element (3).

3. Mast according to claim 1, characterized in that said sectors (4) are obtained through the use of non-homogeneous cloths or sheets, having in particular zones (5) with different properties, such as zones with a higher modulus of elasticity.

4. Mast according to claim 1, characterized in that said sectors (4) are obtained by varying the cross-section of the mould at the side sectors (6) of the tubular element.

5. Mast according to any of the preceding claims, characterized in that said sectors (4) are obtained by combining with each other the features of at least two of the embodiments and constructive solutions cited in said claims.

Drawing