GB2063806A - Improvements in and relating to sailing craft - Google Patents

Abstract

In a sailing craft, particularly a yacht, having a hull (2) and a rig which includes a mast (8), a boom (18) and a sail (24), a permanent or sustained bend is induced into the portion (10) of the mast (8) above the hull by a pair of ties (20, 22), while the lower extent (12) of the mast is pivotally mounted in a bearing arrangement (14, 16) in the hull (2) such that the centreline of said arrangement, about which the mast (8) pivots, when extended above the hull, passes substantially through the centre of gravity (G) of the rig. The ties (20, 22) are such as to retain the mast (8) in a rigid bent condition, thus obviating the need for supplementary rigging, while the angled nature of the pivotal mounting of the rig provides a degree of mechanical and dynamic balance thereto which reduces the forces necessary to control movement of the craft. <IMAGE>

Description

SPECIFICATION Improvements in or relating to sailing craft This invention relates to sailing craft such as yachts, dinghies and the like provided with sails.

The sail of a modern yacht is generally of triangular shape the leading edge of which is supported along its length by a mast while the lower aft corner of the sail is attached at or adjacent the rear end of a horizontal boom the front end of which boom is pivotally attached adjacent the bottom end of the mast.

The amount by which the boom and sail are allowed to move angularly to either side of the fore and aft centreline of the hull of the yacht is controlled by an adjustable tie extending between the rear end of the boom and an attachment point on the deck, the angle of the boom being set by the crew and being dependent upon the direction in which the yacht is required to sail and upon the direction of the wind.

Because the pressure of the wind on the sail tends to lift the boom a further adjustable tie is usually attached between the boom and a point on the mast below the pivot attachment of the boom to restrain this action and thereby to ensure that the maximum amount of sail area is presented to the wind.

To counterbalance the heeling effect of the wind on the sail and to keep the yacht as near upright as possible one of two methods can be used. Either ballast is positioned as low as possible beneath the hull, conveniently at the bottom of a keel, or the crew concentrate their body-weight on the side of the yacht being raised due to the heeling effect of the wind.

A keel or centreboard is provided below the yacht's hull to give lateral resistance to the water and to reduce the amount of sideways movement or leeway when the yacht is sideways on to the wind.

The masts of most current yachts are either of the supported or the unsupported type.

A supported mast is held perpendicular to the horizontal centreline of the yacht by rigging wires attached between points on the mast and extremities of the yacht's hull, while further rigging wires are used to prevent the mast from bending. The sail for this type of mast is cut to shape on the assumption that the mast will remain rigid under varying wind forces.

A yacht with such a mast has the advantage that the design of the sail is simplified by assuming that the mast will remain in a predetermined shape under varying wind forces, while it is reasonably easy for the crew to adjust the flow in the sail to suit any particular wind strength.

However, in keeping the mast rigid relative to the hull, downward forces are created by the mast in the centre of the hull and upward forces are created by the rigging wires on the extremities of the hull which require the provision of considerable reinforcement to the hull thus adding weight to the yacht. Further the provision of the rigging wires adds to the cost of the yacht, while said wires result in additional wind resistance or drag.

An unsupported mast has no rigging wires, the mast being held perpendicular to the centerline of the yacht by its lower end being received within bearings set in the hull. The mast may be rigidly held in said bearings, the boom pivoting in a horizontal plane about its point of attachment to the mast, or the mast may pivot in said bearings in which case the boom may be rigid with the mast for movement therewith in said horizontal plane. The sail for an unsupported mast is designed to provide an optimum performance on the assumption that the mast will bend, within its limits of elasticity, under varying wind forces.

A yacht with an unsupported mast has the advantage that the only hull reinforcement required is that necessary to support the deadweight of the rig-i.e. the mast, boom and sail-and the leverage created by the pressure of the wind on the sail, while the elimination of rigging wires and fittings for their attachment reduces the cost, weight and maintenance as well as the wind resistance of the yacht.

However, because the mast does not remain in a rigid state under varying wind forces, the sail can only be designed for an average wind force-to cater for other wind forces, various types of devices have to be used by the crew to apply forces to the mast, boom and/or sail to provide best flow in the sail. This clearly requires the crew to make frequent adjustments to the shape of the sail.

Established rigs incorporating both supported and unsupported masts both suffer from the added disadvantages that they are totally unbalanced, both mechanically and dynamically, when subjected to wind pressure because all the sail pivots horizontally about its vertical leading edge. Thus the load required to hold the sail at any desired angle relative to both the wind direction and the centreline of the yacht is substantial. Further, with the wind in the same direction as that in which the yacht is sailing, the sail extends substantially transversely of, to one side of, the centreline of the yacht so that the wind forces acting on the sail from aft to fore of the yacht are out of line with-i.e. laterally displaced relative to-the forces created by the resistance of the water on the hull, which forces act from fore to aft on the yacht.Thus a fairly substantial force has often to be applied to the rudder to hold the yacht on course.

Clearly it would be desirable to provide a yacht with rig which incorporated the advantages of both the supported and unsupported masts whist at the same time dispensed with the disadvantages of both said arrangements.

According to the present invention there is provided a sailing craft comprising a hull and a rig, the rig including a mast of a flexible material the portion thereof above the hull extending, in its undistorted condition, upwardly from the hull substantially perpendicular to the fore-aft centreline of the hull, a boom the fore end of which is attached adjacent the lower end of said portion of the mast to extend rearwardly of the hull from said mast, a pair of ties one connecting the upper end of the mast with the rear end of the boom and the other connecting the rear end of the boom with the mast at a point below the region of attachment of the boom to the mast, said ties being tensioned to induce a sustained bend into the mast with the upper end of the mast positioned aft of the lower end of said mast, and a sail the leading edge of which is attached along its length to, and conforms in shape with, the bent mast, the mast including a lower extent pivotally mounted in, to be supported by, a bearing arrangement within the hull, the rig being of such a construction and the bearing arrangement being so positioned that the centreline of said arrangement, about which the lower extent of the mast pivots, when extended above the hull, passes substantially through the centre of gravity of the rig.

It will be appreciated that, by inducing a sustained bend into the mast-i.e. one that cannot be overcome by wind force-by said ties, the mast is held rigid relative to the sail along the leading edge of the sail, thereby dispensing with the need for any rigging between the mast and the hull to hold the mast rigid and the need for any reinforcement of the hull other than that required to support the deadweight of the rig and the leverage created by the wind on the sail.

Further, by providing a rig mounted in a bearing arrangement the centreline of which, when extended, passes substantially through the centre of gravity of the rig, said rig is substantially mechanically balanced which reduces, compared with conventional unbalanced rigs, the force required to hold the sail against the force of the wind.

Further, the above-mentioned pivot centreline passes closer to the centre of effort of the sail than in conventional straight-masted rigs, thereby imparting a degree of dynamic balance to the rig by providing an area of sail on each side of the craft fore and aft centreline with the boom displaced from its fore and aft position. Thus the amount of rolling of the craft is reduced, compared with established arrangements, when the craft is sailing in the same general direction as the wind.

Preferably of the order of 25% of the sail area is located forward of said extended centreline of the bearing arrangement.

In a preferred craft, the ties are adjustable in length to enable the degree of bend in the mast to be varied and thereby to enable the crew to set flow into the sail to provide optimum performance under any particular wind strength.

In one embodiment of the invention the lower extent of the mast lies at an angle to the portion thereof above the hull, the bearing arrangement comprising upper and lower cylindrical bearings within the hull which receive therein the upper and lower regions of the lower extent of the mast.

In an alternative embodiment of the invention, the lower extent of the mast is a linear continuation of the portion of the mast above the hull, the bearing arrangement comprising an upper spherical bearing receiving therein the upper region of the lower extent of the mast and a lower cylindrical bearing receiving therein a pin member fixed to, but radially offset from the central axis of, the mast, the central axis of said pin member conforming with the centreline of the bearing arrangement.

By way of example only, embodiments of the invention will now be described in greater detail with reference to the accompanying drawings of which: Figure 1 is a side view of a yacht according to the invention with the boom positioned fore-aft of the yacht; Figures 2 and 3 are front views of the yacht of Fig. 1 with the boom at 45 and 90 respectively to the fore-aft centreline of the yacht; Figure 4 is a side view of the yacht of Fig.

1 with the boom in the position as in Fig. 3; Figures 5 and 6 show the yacht of Fig. 1 and a conventional yacht respectively heeled at the same angle, and Figure 7 shows an alternative bearing arrangement for a yacht according to the invention.

Referring to Fig. 1, the illustrated yacht comprises a conventional hull 2 provided with a keel 4 and a rudder 6. The rig of the yacht includes a mast 8 of the unsupported type - and of a flexible material for reasons which will become apparent.

More particularly, the mast 8 comprises a main portion 10 above the hull 2 and initially extending vertically upwardly perpendicular to the fore and aft centreline of the hull as shown at 10' in Fig. 1. Said mast is completed by a lower portion 1 2 within the hull and set at an angle to the portion 10 again as best seen in Fig. 1. The portion 1 2 is pivotally mounted in a bearing arrangement comprising upper and lower cylindrical bearings 14, 16 respectively housed within the hull 2.

The fore and of a boom 1 8 is secured to the mast at a point adjacent the lower end of the portion 10 thereof, the boom 18 extending rearwardly from, and being movable with, said mast 8.

A first tie 20 extends between the top end of the mast 8 and the aft end of the boom 18, while a further tie 22 extends between the aft end of the boom 1 8 and a point on the mast 8 just below the point of attachment of the boom to the mast. The ties 20 and 22 are tensioned to induce a bend into the flexible mast so that the upper end of the portion 10 of the mast is positioned aft of the lower end of said portion 10. The forces applied to the mast by the ties are greater than can be overcome by the wind under even extreme conditions and said forces therefore impart what can be considered a permanent distortion into the mast.

The rig is completed by a generally triangular sail 24 the leading edge of which is shaped to conform with, and is attached along its length to, the bent portion 10 of the mast 8. The lower edge of the sail is, in conventional fashion, secured to the boom 1 8.

The angle of the lower portion 1 2 of the mast relative to the portion 10 of the mast is chosen such that, with said portion 1 2 pivotally mounted in the bearings 14, 1 6 to locate the rig on the hull 2, the axial centreline of the portion 12, shown in dotted lines at 26 and which conforms with the pivot centreline of the bearing arrangement, when extended upwardly above the hull 2, passes close to or through the centre of gravity G of the rig as well as the centre of effort E of the sail.

The described yacht has many advantages over conventional yachts. In particular, by inducing a bend into the mast 8, the portion 10 thereof is held rigid relative to the sail 24 along the leading edge of said sail, thereby obviating the need for standing rigging to prevent bending and removing the requirement for extra hull reinforcement. If the ties 20, 22 are made adjustable, the crew is able to set flow into the sail to provide the best performance under any particular strength of wind.

By pivoting the rig in bearings located such that the pivot centreline passes through or near to the centre of gravity of the rig, said rig is mechanically balanced in its pivot mounting, while said centreline passing close to the centre of effort of the sail results in a degree of dynamic balance in the rig. In a preferred rig, there is approximately 25% of the sail area forward of the mast pivot centreline, experiments having shown that the forward part of a sail contributes proportionately far more than the aft part of the sail, a 25/75% ratio resulting in minimum effort to sheet in the sail.

Thus the force required to hold the sail against the wind is reduced compared with conventional arrangements, while the provision of an area of sail on each side of the yacht's fore and aft centreline when the boom is set at an angle to said centreline and the yacht is sailing in the same general direction as the wind reduces the amount of rolling of the yacht that would otherwise occur.

As can be seen in Figs. 2 and 3, pivoting of the mast in the bearings 14, 1 6 results in the boom 1 8 lifting as it moves away from the fore and aft centreline of the yacht thereby reducing the possibility of the boom 18 and sail 24 striking the water when the yacht heels. This is further illustrated in Figs. 5 and 6 which show, respectively, a heeled yacht with the above-described rig, the boom being clear of the water, and a conventional yacht heeled at the same angle, the boom (and sail) being partially submerged.

Fig. 4 shows that, as the boom swings outwardly from the fore and aft centreline of the yacht, the mast and sail move angularly aft, thereby reducing the downward forces on the bow of the yacht.

Fig. 7 shows an alternative bearing arrangement to that of the yacht of Figs. 1 to 5 but which results in the same advantage as those achieved with the bearing arrangement shown in Figs. 1 to 5. Referring to Fig. 7, the lower extent 1 2 of the mast 8 forms a linear continuation of the portion 10 thereof above the hull 2. A bracket 28 is fixedly secured to the lower end of the portion 12, said bracket carrying thereon a pin member 30 laterally displaced from the central axis of the mast 8 and set at an angle to said axis. Said pin member 30 is received within, to be rotatable in a cylindrical lower being 16, while the upper bearing 14, through which extends the upper region of the portion 1 2 of the mast, is of spherical form. The pivot centreline of the bearing arrangement is referenced 26' and, when extended above the hull 2, it passes close to or through the centre of gravity of the rig. Thus it will be appreciated that the nature of the pivoting movement of the rig in the bearings 14, 1 6 of Fig. 7 is the same as that detailed with reference to Figs. 1 to 5.

Claims (1)

1. A sailing craft comprising a hull and a rig, the rig including a mast of a flexible material the portion thereof above the hull extending, in its undistorted condition, upwardly from the hull substantially perpendicular to the fore-aft centreline of the hull, a boom the fore end of which is attached adjacent the lower end of said portion of the mast to extend rearwardly of the hull from said mast, a pair of ties, one connecting the upper end of the mast with the rear end of the boom and the other connecting the rear end of the boom with the mast at a point below the region of attachment of the boom to the mast, said ties being tensioned to induce a sustained bend into the mast with the upper end of the mast positioned aft of the lower end of said mast, and a sail the leading edge of which is attached along its length to, and conforms in shape with, the bent mast, the mast including a lower extent pivotally mounted in, to be supported by, a bearing arrangement within the hull, the rig being of such a construction and the bearing arrangement being so positioned that the centreline of said arrangement, about which the lower extent of the mast pivots, when extended above the hull, passes substantially through the centre of gravity of the rig.

2. A sailing craft as claimed in claim 1 in which of the order of 25% of the area of the sail is located forward of the extended centreline of the bearing arrangement.

3. A sailing craft as claimed in claim 1 or claim 2 in which the lengths of the two ties are adjustable.

4. A sailing craft as claimed in any one of claims 1 to 3 in which the lower extent of the mast lies at an angle to the portion thereof above the hull, the bearing arrangement comprising upper and lower cylindrical bearings within the hull which receive therein the upper and lower regions of the lower extent of the mast.

5. A sailing craft as claimed in any one of claims 1 to 3 in which the lower extent of the mast is a linear continuation of the portion of the mast above the hull, the bearing arrangement comprising an upper spherical bearing receiving therein the upper region of the lower extent of the mast and a lower cylindrical bearing receiving therein a pin member fixed to, but radially offset from the central axis of, the mast, the central axis of said pin member conforming with the pivot centreline of the bearing arrangement.

6. A sailing craft substantially as described with reference to and as illustrated by Figs. 1 to 5 and Fig. 7 of the accompanying drawings.

CLAIMS (10 Feb 1981)

1. A sailing craft comprising a hull and a rig, the rig including a mast of a flexible material the portion thereof above the hull extending, in its undistorted condition, upwardly from the hull substantially perpendicular to the fore-aft centreline of the hull, a boom the fore end of which is attached adjacent the lower end of said portion of the mast to extend rearwardly of the hull from said mast, a pair of ties, one connecting the upper end of the mast with the rear end of the boom and the other connecting a point on the mast below the region of attachment of the boom to the mast with a point on the boom remote from the mast, said ties being tensioned to induce a sustained bend into the mast with the upper end of the mast positioned aft of the lower end of said mast, and a sail the leading edge of which is attached along its length to, and conforms in shape with, the bent mast, the mast including a lower extent pivotally mounted in, to be supported by, a bearing arrangement within the hull, the rig being of such a construction and the bearing arrangement being so positioned that the centreline of said arrangement, about which the lower extent of the mast pivots, when extended above the hull, passes substantially through the centre of gravity of the rig.