GB2120192A - Sailing boat with twin rudders - Google Patents

Abstract

A sailing boat has a hull 1 of conventional construction but is of exceptional width at the stern or after end. Beneath the stern twin rudders 3 and 4 are mounted, respectively equidistant on the port and starboard sides from the hull centre-line. The rudders 3 and 4 are coupled together so that they steer the boat in unison, and the hull has single fixed keel 5. The keel 5 is ballast weighted at the bottom at 6, and the twin rudders 3 and 4 which also carry bottom ballast weights 7 and 8 are disposed in an "inverted V" arrangement. <IMAGE>

Description

SPECIFICATION Sailing boats This invention relates to sailing boats, and although of general application in this field it is of particular application to sailing boats such as are generally referred to as yachts.

The inherent necessity for yachts to have a keel in order to provide lateral resistance and optimum stability by weighting of the keel gives rise to a number of problems, such as the ability of a boat to dry out upright if fitted with the conventional single central keel. As the need to minimise wetted area became apparent the traditional so-called "long" keel with a steering rudder attached to the after end has tended to give way to a fin keel with a skeg arrangement, which is quite separate from the fin keel, to provide steering.

To solve the drying out problem twin keels can be used, on which the yacht can rest upright when out of the water, but this usually involves some loss of performance; an alternative solution is to use a retractable or lifting keel and rudder, but this is usually limited to the smaller sizes of yachts. With the latter alternative a relatively wide hull is required to provide stability in place of the ballast weights normally attached to a fixed keel but which cannot be used with a retractable keel; however, especially at larger angles of heel the centre-line of the yacht is necessarily raised which tends to lift the centrallymounted rudder partially out of the water. This reduces the effectiveness of the rudder.

With modern yachts a further problem is that when off the wind the centre of effort of the sail area is insufficiently far forward to obviate a tendency for the yacht to yaw, and indeed sometimes the yacht will be out of control and will broach-to. This problem is readily solved by a lifting or retractable keel (centreboard), but such an arrangement is often impracticable for larger yachts.

There is also the problem of making maximum use of the ballast available to enable the yacht to stand up to her sail area, and this ballast is often of the order of 50% of the total displacement weight. As the yacht, generally speaking, has to be able to sail equally well on either tack, that is to say with the wind from either side, the ballast weights must be arranged to take account of this and they are accordingly commonly disposed along the centre line. These weights often form the bottom of the keel, which complicates or limits the use of a retractable keel.

Because of the need to obtain positive steering at large angles of heel the stern or after end of a displacement yacht is necessarily brought well in from the maximum width or beam of the hull so that the rudder, at large heel angles, cannot be elevated above the water line. This results in a loss of buoyancy and has two main disadvantages. Firstly, the internal capacity available is necessarily reduced relative to the overall length of the hull, and secondly the possibility of planing over the surface of the water, in the manner of a light displacement yacht or dinghy, is effectively precluded.

The object of the invention is to provide a sailing boat or yacht with a novel rudder arrangement which enables the foregoing problems and disadvantages to be overcome, or at least materially reduced.

According to the invention a sailing boat has two spaced separate rudders mounted adjacent the stern end of the boat, these rudders being coupled so that they operate in unison to steer the boat.

Preferably the two rudders are inclined and disposed in a symmetrical "inverted V" arrangement beneath the stern end of the boat, and the boat desirably has a fixed single keel the depth of which is such that, for drying out purposes, the boat can rest upright supported on the keel and the two rudders.

A twin rudder/single central keel arrangement in accordance with the invention combines the virtues of a twin-keeled yacht without any loss of performance such as is normally associated with the latter.

There is provided the advantage of being able to use a wider stern to maximise the available accommodation for the length of the hull. The greater width of the hull at the after end results in a better potential to plane or surf, such as is normally only associated with lighter displacement dinghy type of yachts. Off the wind both the rudders will be fully submerged in water-flow which is undisturbed by any keel ahead of them, thus increasing the steering ability by effectively bringing the centre of lateral resistance further to the rear.

When a yacht in accordance with the invention is well heeled going to windward, there is the advantage that one rudder may be out of the water thus reducing the wetted area. In this condition that rudder, if weighted, will have considerable leverage to provide a substantial righting moment while the other will be near to vertical below the C.G. (centre of gravity). Thus ballast weights are preferably fixed to the bottom of the rudders. Additional righting moments are available as a result of the whole centreline of the yacht also being raised, so that the stability resulting from buoyancy will be enhanced.

The invention will now be further described with reference to the accompanying drawings which illustrate, by way of example, the hull of a yacht embodying the invention. In the drawings: Figure lisa stern view of the hull; and Figures 2 and 3 are, respectively, side elevation and plan views to a reduced scale.

The hull 1 is of conventional construction but, for its displacement size, is of exceptional width at the stern or after end 2. As can be seen from the plan view of Figure 2, it approximates more to the stern shape which one would associate with a small dinghy-type yacht. Beneath the stern end 2 two rudders 3 and 4 are mounted, respectively equidistant on the port and starboard sides of the hull centre-line C/L. These two separately mounted rudders 3 and 4 are coupled together so that they steer the boat in unison, being illustrated in the straightahead positions.

The hull 1 has a single fixed keel 5, ballast weighted at the bottom at 6. The twin rudders 3 and 4 also carry bottom ballast weights 7 and 8, respectively, and as shown in Figure 1 are disposed in an inverted V arrangement, Figure 1 illustrates how the described arrangement enables the hull to dry out upright out of the water, the ground level being indicated at G. It can be seen that the hull stands upright, with the twin rudders 3,4 and the central single keel 5 resting on the ground.

The optimum orientation and disposition of the rudders 3 and 4 will vary with different hulls, but in the typical example illustrated the rudders are inclined at an angle of about 45" to each other. They are positioned so that they are normally both just submerged below the water-line, and one or other of the rudders 3,4 will be raised out of the water at a heeling angle of 30 or more. A maximum heel angle of 45" is available, with the other rudderfully operative, and the rudder out of the water has a considerable leverage which, due to the weights 7, 8, applies an appreciable righting moment to the hull.

CLAIMS (Filed on 17.5.83) 1. A sailing boat having two spaced separate rudders mounted adjacent the stern of the boat, said two rudders being symmetrically disposed and coupled so that they operate in unison to steer the boat.

2. A sailing boat according to claim 1, wherein the two rudders are inclined to the vertical and disposed in a symmetrical "inverted V" arrangement beneath the stern of the boat.

3. A sailing boat according to claim 2, wherein the rudders are mutually inclined at an angle of about 45".

4. A sailing boat according to claim 2 or claim 3, wherein the arrangement is such that both of said rudders are normally just submerged below the water-line, whereas one or other of them will be raised out of the water at a heeling angle of about 30 or more.

5. A sailing boat according to any one of the preceding claims, wherein the boat has a fixed single keel the depth of which is such that, for drying out purposes, the boat can rest upright supported on the keel and the two rudders.

6. A sailing boat according to any one of the preceding claims, wherein ballast weights are fixed to the rudders adjacent the bottom edges thereof.

7. A sailing boat according to any one of the preceding claims, wherein in side view the rudders are parallel sided with generally horizontal bottom edges.

8. A sailing boat according to any one of the preceding claims, wherein a (or the) keel of the boat is ballast weighted at the bottom.

9. A sailing boat according to any one of the preceding claims, wherein the hull is of conventional construction but is of exceptional width at the stern or after end, and approximates to the stern shape which would be associated with a small dinghy-type yacht.

10. A sailing boat constructed and arranged substantially as herein particularly described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. inverted V arrangement, Figure 1 illustrates how the described arrangement enables the hull to dry out upright out of the water, the ground level being indicated at G. It can be seen that the hull stands upright, with the twin rudders 3,4 and the central single keel 5 resting on the ground. The optimum orientation and disposition of the rudders 3 and 4 will vary with different hulls, but in the typical example illustrated the rudders are inclined at an angle of about 45" to each other. They are positioned so that they are normally both just submerged below the water-line, and one or other of the rudders 3,4 will be raised out of the water at a heeling angle of 30 or more. A maximum heel angle of 45" is available, with the other rudderfully operative, and the rudder out of the water has a considerable leverage which, due to the weights 7, 8, applies an appreciable righting moment to the hull. CLAIMS (Filed on 17.5.83)

1. A sailing boat having two spaced separate rudders mounted adjacent the stern of the boat, said two rudders being symmetrically disposed and coupled so that they operate in unison to steer the boat.

2. A sailing boat according to claim 1, wherein the two rudders are inclined to the vertical and disposed in a symmetrical "inverted V" arrangement beneath the stern of the boat.

3. A sailing boat according to claim 2, wherein the rudders are mutually inclined at an angle of about 45".

4. A sailing boat according to claim 2 or claim 3, wherein the arrangement is such that both of said rudders are normally just submerged below the water-line, whereas one or other of them will be raised out of the water at a heeling angle of about 30 or more.

5. A sailing boat according to any one of the preceding claims, wherein the boat has a fixed single keel the depth of which is such that, for drying out purposes, the boat can rest upright supported on the keel and the two rudders.

6. A sailing boat according to any one of the preceding claims, wherein ballast weights are fixed to the rudders adjacent the bottom edges thereof.

7. A sailing boat according to any one of the preceding claims, wherein in side view the rudders are parallel sided with generally horizontal bottom edges.

8. A sailing boat according to any one of the preceding claims, wherein a (or the) keel of the boat is ballast weighted at the bottom.

9. A sailing boat according to any one of the preceding claims, wherein the hull is of conventional construction but is of exceptional width at the stern or after end, and approximates to the stern shape which would be associated with a small dinghy-type yacht.

10. A sailing boat constructed and arranged substantially as herein particularly described with reference to the accompanying drawings.