GB2171959A

GB2171959A - Sailing vessel keel

Info

Publication number: GB2171959A
Application number: GB08508080A
Authority: GB
Inventors: Peter James Windibank
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-02-14
Filing date: 1985-03-28
Publication date: 1986-09-10
Also published as: GB8503747D0; GB2171959B; GB8508080D0

Abstract

A keel 8 of a sailing boat, comprising a fixed part and a moveable apart 9 or additional foil which is moveable to produce a righting moment which resists a heeling moment due to the wind in the boat's sails. <IMAGE>

Description

SPECIFICATION Sailing vessel keel The present invention provides a keel, or an addition to a keel, for a sailing boat.

When a sailing boat with its sails filled with wind is moving through the water, the boat is generally at an angle to the direction of approach of the wind. The horizontal force of the wind on the sail can be resolved into two components; a component in the direction of travel of the boat and a component perpendicular to this. This force perpendicular to the direction in which the boat is moving causes the boat to tilt over to one side, known as "heeling". For greater speed, however, the boat should be in an upright position.

A common way to reduce "heeling", particularly in small boats, is for crew members to lean back over the windward side of the boat thus producing a moment in the opposite direction from the heeling moment.

The present invention provides a sailing boat having at least part of the keel or an additional foil to the keel moveable to generate a controllable lateral force on the keel to influence the angle of heel of the boat when it is in motion.

The present invention further provides a keel for a sailing boat, comprising a fixed keel part and a moveable keel part or additional foil moveable relative to the fixed keel part and capable of generating a controllable lateral force on the keel as it moves through the water.

Preferably the moveable part or additional foil of the keel is attached beneath the part of the keel fixed to the hull. This moveable part can be moved so that, as the boat moves through the water the moveable part causes the passing water to follow an asymmet rica I path past the keel. As the water flows past the moveable part it produces a side force across the part. The moveable part is positioned such that the side force produced results in a moment in the opposite direction to the heeling moment. This encourages the boat to sail upright or at a reduced angle of heel.

The invention will now be further described with the help of the accompanying drawings.

Figure 1 shows a perspective view, from below, of the bottom of a boat with a keel equipped with a moveable part; Figure 2 shows a perspective view, from below, of the bottom of a boat with a keel equipped with an additional foil; Figure 3 shows a view of the heeling boat of Figure 1 from the front; Figure 4 shows a section through the keel taken along the longitudinal centre line of the boat of figure 1; Figure 5 shows a section along AA of figure 4; and Figure 6 shows a perspective view from below, of the bottom of a boat with a keel with a moveable part with wing lets.

In Figure 1 the moveable part (9) of a keel is rotatably mounted on the bottom of the fixed part of a keel (8) by a vertical shaft (10) running through the fixed part of the keel. Preferably the moveable part is of such a shape that it may be rotated to be flush with the fixed part of the keel or rotated to be at an angle as shown in the figure. However any shape which can be positioned to present an asymmetric shape for the water to flow past will suffice.

Although the moveable part is preferably attached beneath the keel to produce the maximum moment for a given force since the perpendicular distance from the axis of heel is greatest, it would also be possible to attach the moveable section at some other point down the keel or at the back or front Figure 2 shows another embodiment of the invention in which the keel comprises an additional vertical foil (11) which is mounted so that when aligned fore and aft it can be retracted upwards to be housed in a cavity (12) formed within the fixed part of the keel.

The moveable part of the keel (Figure 1 ) and the additional foil (Figure 2) are each rotatably mounted on a shaft whose axis of rotation is at a suitable point along the chord of the foil but other moveable mountings such as hinges could also be envisaged for allowing the generation of a lateral force substantially without any yawing moment.

When the moveable part of the keel or the additional foil is at an angle as in figure 3 the flow of water past it produces a sideways force, R, normal to the vertical axis of the keel. This generates a righting moment, Rd, which acts in the opposite direction from the heeling moment, Wh. This encourages the boat to move in an upright position.

A convenient method of attaching the moveable part of the keel or the additional foil to the fixed part of the keel is shown in figure 4. A shaft (10) through the fixed part of the keel (8) connects the moveable part of the keel (9) (or the additional foil) with the inside of the boat. Generally there is a means (13) for rotating the shaft to alter the angle between the moveable keel part or additional foil and the fixed part of the keel.This rotating means may be either manually or automatically operated. Preferably there is also means to ensure that the moveable part or additional foil is held in the desired position in relation to the fixed part of the keel, eg means for fixing the shaft in a particular position.

A further embodiment is shown in Figure 6 in which the moveable part of the keel is attached beneath the fixed part of the keel, as in Figure 1, and there arewinglets (14, 15) extending laterally from the base of the fixed part of the keel and the base of the moveable part of the keel. This preferred feature limits spanwise flow and increases the effective aspect ratio. Further, it reduces the interference between the flow round the fixed keel and the moving part. These winglets could, of course, be used on the boat shown in Figure 2 with the additional foil.

Although the drawings show a single-keeled sailing craft, it will be appreciated that the invention may be applied to a multi-keeled craft such as a bilge keel cruiser. In that case the two keels may each be fitted with a moveable part, or a separate foil which is preferably vertical. However, a generally horizontal foil rotatable about a horizontal axis transverse to thefore-and-aft axis of the hull may be provided.

I am aware of the use of stabilising foils on large motorised ships, such as flat-bottomed ferries, but there is no suggestion of their being used to correct a substantially constant heeling moment due to wind effect. Their purpose is to correct transient rolling moments due to water movement such as wave motion.

Claims

1. A sailing boat having at least part of the keel or an additional foil to the keel moveable to generate a controllable lateral force on the keel to influence the angle of heel of the boatwhen it is in motion.

2. Asailing boat as claimed in claim 1, in which the moveable part of the keel or the additional foil has an axis of rotation perpendicular to the axis of heel of the boat.

3. A sailing boat according to claim 2,wherein the axis of rotation is vertical when the boat is upright.

4. A sailing boat according to claim 1, 2 or 3, wherein the moveable part or foil is positioned and mounted so as to generate the controllable lateral force substantially without any yawing moment

5. A sailing boat as claimed in any one of claims 1-to 4, in which the moveable part of the keel is attached beneath the rest of the keel which is fixed to the hull of the boat.

6. A sailing boat as claimed in claim 5, in which the moveable part of the keel may be aligned to be flush with the base of the part of the keel fixed to the hull.

7. Asailing boat as claimed in any one of claims 1 to 6;in which the additional foil is mounted beneath the fixed part of the keel.

8. A sailing boat as claimed in claim 1,2,3,4 or 7, in which the additional foil may be retracted to be housed in a cavity within the fixed part of the keel.

9. A sailing boat as claimed in claim 8 in which the moveable part of the keel or the additional foil is rotated by means of a shaft passing through the part of the keel fixed to the hull.

10. A sailing boat as claimed in claim 9 which comprises means for holding the moveable part of the keel or the additional foil in the desired position relative to the part of the keel fixed to the hull.

17. A sailing boat as claimed in any one of claims 1 to 10 in which the base of the keel has winglets extending laterally to serve as flow fences.

12. A keel for a sailing boat as claimed in any one of claims 1 to 10.

12. A sailing boat as claimed in any one of claims 1 to 11 in which the base of the moveable part of the keel or the base of the additional foil has laterally extending winglets serving as flow fences.

13. A sailing boat according to any one of claims 1 to 12, having at least two keels each equipped with a said movable part or additional foil.

14. A sailing boat substantially as hereinbefore described with reference to the accompanying draw ings.

15. A keel for a sailing boat, comprising a fixed keel part and a moveable keel part or an additional foil moveable relative to the fixed keel part and capable of generating a controllable lateral force on the keel as it moves through water.

16. A keel for a sailing boat as claimed in any one of claims 1 to 14.

Amendments to the claims have been filed, and have the following effect: (b) New or textually amended claims have been filed as follows: 1. A sailing boat having a keel, and an additional foil at the bottom of the keel moveable about an axis of rotation perpendicular to and intersecting the axis of heel of the boat and positioned at a given point along the chord of the foil such that when the boat is in motion the foil generates a controllable lateral force on the keel to influence the angle of heel substantially without any yawing moment.

2. A sailing boat according to claim 1, wherein the axis of rotation of the foil is vertical when the boat is upright.

3. A sailing boat according to claim 1 or 2, wherein the moveable part of the keel may be aligned to be flush with the base of the part of the keel fixed to the hull.

4. A sailing boat as claimed in claim 1,2 or 3, in which the additional foil may be retracted to be housed in a cavity within the fixed part of the keel.

5. A sailing boat as claimed in claim 4, in which the additional foil is rotated by means of a shaft passing through the part of the keel fixed to the hull.

6. A sailing boat as claimed in claim 5, which comprises means for holding the additional foil in the desired position relative to the part of the keel fixed to the hull.

7. * A sailing boat as claimed in any one of claims 1 to 6 in which the base of the keel has winglets extending laterally to serve as flow fences.

8. A sailing boat as claimed in any one of claims 1 to 7, in which the base of the additional foil has laterally extending winglets serving as flow fences.

9. A sailing boat according to any one of claims 1 to 8, having at least rwo keels each equipped with a said additional foil.

10. A sailing boat substantially as hereinbefore described with reference to the accompanying draw ings.

11. A keel for a saiiing boat, comprising a fixed keel part and an additional foil which is moveable relative to the fixed keel part about an axis of rotation which will be perpendicular to and will intersect the axis of heel of a sailing boat fitted with the keel, the additional foil having its axis of rotation so positioned relative to its chord that the foil can be rotated to generate a controllable lateral force on the keel substantially without any yawing moment as it moves through water.