GB2468839A

GB2468839A - Keel with deployable hydrofoil surfaces

Info

Publication number: GB2468839A
Application number: GB0904294A
Authority: GB
Inventors: Michael Dickinson
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-03-13
Filing date: 2009-03-13
Publication date: 2010-09-29
Also published as: GB0904294D0

Abstract

A keel for sailing boats is made up of three main elements, a central skeletal fin 1, a left foil 3 and a right foil. The foils which have a curved hydrofoil type section are deployed and controlled in different ways depending on the construction of the craft and the use to which it is put. The foils when deployed lie along the side surfaces of the central skeletal fin and act, due to the water flowing over them, to provide a force at right angles to the direction of movement of the boat, to counter-act the heeling effect provided by the load on the sails of the boat. Control may be manual, automated, or partly automated. A standard ballast bulb 2 may be provided at the lower end of the central skeletal fin. The foils may be deployed in a sliding motion (Figs 2 and 5), may be mounted on a belt arrangement (Fig 3), or may be deployed in a pivoting motion (Figs 4 and 7).

Description

This invention relates to a design of sailing boat keel gaining part of its function from the dynamic effect of water flowing over aerof oil sections.

The keel is an essential part of a sailing boat. The conventional keel works in three ways. Firstly, the mass of the keel, which may or may not have a bulb at its base, acts as a counterweight to the heeling effect of the wind on the sails.

Secondly, the fin, by means of the sideways-facing area it presents resists sudden heeling moments caused by the sails and helps to prevent the boat being blown downwind.

Thirdly, by lowering the centre of gravity, the weight of the keel helps to reduce capsizing and will act to right the boat in the event of capsize.

The effectiveness of the boat's keel is one factor in determining to what extent the energy in the wind can be harnessed by the sails and converted into forward motion.

There have been attempts to utilise the effect of the water flow to generate counter-heeling forces. Generally these have been attempted by the use of trim tabs at the rear of the keel but these have proved unsuccessful due to the ruddering effect these produce, and their high drag. (W02004098987) The present invention proposes the facility to alter the aerofoil section of the keel in such a way as to produce a flat lift' i.e. with no ruddering effect and low drag.

In effect the keel then acts like the wing of an aeroplane, with the lift' acting against the heeling moment produced by the boat's sails.

The alteration of the aerofoil section of the keel is achieved by the deployment of shaped foils on either side of a central skeletal fin. The combination of central fin and one or other foil forms an aerofoil section with either a Ieftwards or rightwards effect. The yachtsman will select in which direction he needs the effect to act, depending in which direction the boat is tending to heel. By progressively deploying more or less of the foil alongside the central fin, the degree of lifting force can be altered to match the heeling effect of the sails.

Control can be automated but it is likely that most yachtsmen will choose to fine-tune the degree of force themselves to optimise performance.

The mass of a conventional keel is retained in order to confer the normal stability effect.

The object of this keel is to allow for improved high-speed performance by increasing the counter-heeling effect and allowing for a greater utilisation of the wind by the sails.

There are a number of different embodiments of the concept. These are necessary to allow incorporation in a variety of boat types and sizes.

The keel is generally made up of a central skeletal fin with or without a ballast bulb at its base. Foils can be deployed on either side of the fin as appropriate, Figure 1.

Foil deployment can be either total or partial allowing the yachtsman to match the counter-heeling effect to the sail effect and conditions.

There are four embodiments envisaged at present for larger boats. The principle is the same, namely to introduce a foil section on either side of the fin.

Embodiment 1, rigid foils, (3) sliding along the length of the fin, (1) Figure 2 Embodiment 2, belted foil segments, (5) sliding along the fin, Figure 3 Embodiment 3, rigid foils, (6) swinging about a pivot, (7) Figure 4 Embodiment 4, rigid foils, (8) sliding along curved track, (9) Figure 5.

There are two further embodiments suitable for smaller boats, one with a single foil which is withdrawn and reversed to alter the force from left to right, one in which two mirror image foils are used, either of which is deployed to give a force in the desired direction.

EmbodimentS, rigid reversible foil, (10) Figure 6, Embodiment 6, a pair of mirror image foils, (11,12) which may be deployed singly to give a left or right effect or jointly to give a neutral effect, Figure 7.

Figure 1 shows a generalised view of the concept.

Claims

Claims 1. A keel for sailing boats which exploits the hydrodynamic forces available under a moving boat to counter the heeling effects of the wind's force on the sails, consisting of a central fin which may be fixed or canting, and deployable foils, the section of the foils being similar to that of an aerofoil, such that the force they produce is at right angles to the mid line of the craft without tending to have a steering effect on the boat.
2. A keel for sailing boats which exploits the hydrodynamic forces available under a moving boat to counter the heeling effects of the wind's force on the sails, consisting of a fin, having a section similar to that of an aerofoil, which produces a force at right angles to the mid line of the craft without tending to have a steering effect on the boat, the fin being withdrawn and reversed to alter the counter-heeling effect from left to right.
3. A keel for sailing boats which exploits the hydrodynamic forces available under a moving boat to counter the heeling effects of the wind's force on the sails, consisting of two foils, left and right, being similar in section to that of an aerofoil, which produce forces at right angles to the mid line of the craft without tending to have a steering effect on the boat, the foils being mirror images of each other and withdrawn and deployed to alter the counter-heeling effect from left to right.
4. A keel for sailing boats according to claim 1, in which the foils can be deployed and withdrawn along the axis of the keel.
5. A keel for sailing boats according to claim 1, in which the foils can be deployed and withdrawn by means of segmentation and attachment to a flexible belt.
6. A keel for sailing boats according to claim 1, in which the foils can be deployed and withdrawn by means of a pivot around which they rotate.
7. A keel for sailing boats according to claim 1, in which the foils can be deployed and withdrawn along a curved track.
8. A keel for sailing boats according to claim 2, in which there is no central fin and one single sided foil which is withdrawn and reversed in order to switch the force from left to right.
9. A keel for sailing boats according to claim 3, which consist of two mirror image foils, one of which will produce a leftward force, the other a rightward force, being deployed and withdrawn by means of rotation about a common pivot.