GB2356603A

GB2356603A - Hull having a buoyant keel

Info

Publication number: GB2356603A
Application number: GB0028636A
Authority: GB
Inventors: Michael John Wingeatt
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-11-25
Filing date: 2000-11-24
Publication date: 2001-05-30
Anticipated expiration: 2020-11-24
Also published as: GB2356603B; GB0028636D0; EP1232090A1; WO2001038166A1; AU1535501A; GB9927730D0

Description

2356603 Title: Hull and Keel

DESCRIPTION

The invention relates to a hull and keel design for boats of the type that displace the water they pass through rather than skim or place across the surface.

Traditionally boats have relied upon ballast inside the boat or a heavy external keel, combined with the breadth of the hull, to resist overturning forces and provide a self righting capability. The added weight means that, to move, the hull of the boat must displace the water, upon which it floats, around the hull. This displacement of water creates a bow wave at the front of the boat, a stern wave at the back of the boat and a trough between the two waves. The interaction of these two waves restricts the maximum speed of the boat through the water since as the speed of the hull increases the size of the bow and stern waves also increases and the boat settles deeper into the trough created and cannot escape. As a general rule the maximum speed, in knots, of a displacement hull, of this type, is a coefficient of the square root of its waterline length in feet.

There have, to date, been two methods of overcoming this restriction on hull speed. The first method is to design long narrow hulls since the general rule does not apply to hulls that have a waterline length exceeding five times the waterline breadth as these narrow hulls cut through the water without creating 2 bow and stern waves that can interact. However, individually these hulls do not provide much resistance to overturning forces so two or three hulls are used together and generally do not use ballast (catamarans and trimarans). The disadvantages of this arrangement are excessive width and lack of ability to return to the upright position following capsize. The'second method is by designing hulls with flat surfaces and no fixed ballast, boats can cease to be displacement types by having the ability to climb out of the trough onto the bow wave and skim or plane across the surface of the water. The disadvantages of this arrangement are that size is restricted by the reliance on no fixed ballast with lightweight construction and again lack of ability to return to the upright position following capsize.

An object of this invention is to provide a hull and keel design that solves the problem of fixed ballast displacement boats creating bow and stern waves that interact to restrict the maximum speed of the hull through the water as describe above. It is an aim to do this without excessive width, with no restriction on size and with the ability to return to the upright position following capsize.

Accordingly, the present invention provides a hull and keel in which the keel has enough buoyancy to support any ballast"and enough additional buoyancy to support the weight of the hull to which it is attached so that the hull rests on or near the surface of the water.

The buoyancy may be such that the hull is disposed just above or just below the surface of the water. However, it is preferred that it rests on or just 3 above the surface of the water rather than in it.

The length of the keel exceeds five times the width of the keel to prevent the creation on bow and stern waves that can interact to restrict maximum speed. That is to say the overall length of the keel is five times greater than the width of the keel at its widest part. (The rate of change of the keel width along its length can follow conventional practice). Preferably, where the hull and the keel meet, the hull, on either side of the keel, should be as near a horizontal flat plane as possible on or near the surface of the water. The effect of this is to flatten any waves the keel may create and allow the hull to provide immediate resistance to overturning forces. The width wise extent of these surfaces will vary according to the particular design. Alternatively, in some designs, these surfaces may exhibit some curvature or inclination which departs from a flat horizontal plane.

Preferably the hull and keel should be made of the lightest boat building materials available, such as plastics reinforced with carbon or glass fibres, or wood or steel or a combination of these or other materials.

The invention also extends to a boat when provided with a hull and keel according to the invention. It will be understood that the buoyancy of the keel will be sufficient to support the weight of the boat and any pay load.

The present invention will now be described further hereinafter, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows a section through a keel, Figure 2 shows a section through a hull and keel, 4 Figure 3 is a perspective view of a boat embodying the hull and keel according to the invention.

As shown in Figure 1, the keel 3 is hollow in section with enough buoyancy to support its own weight and that of the fixed ballast 2 so that it floats well above the surface of the water 1.

As shown in Figure 2, the keel also has enough additional buoyancy to support the weight of a hull 7 to which it is attached so that the hull 7 rests on the surface of the water I rather than in it. The length of the keel 3 must always be greater than five times the width of the keel. The width of the keel is represented by the arrow referenced 5. It will be understood that the width of the keel will vary along its length. The variation in width of the keel with respect to length will follow conventional practice. The hull can have any desired configuration as concerns its length and width. However, where the keel 3 meets the hull 7 there are flat surfaces, shown at 4 and 6 extending outwardly from the keel. These are shown resting on the surface of the water 1 in the illustrated embodiment. These flatten any wave formed by the keel 3 as it moves through the water and gives the hull a shape that will provide immediate resistance to any over turning forces. The distance that these surfaces extend from the keel will vary from one design to another.

A boat embodying the hull 7 and keel 3 is shown in Figure 3.

The above example of the invention is given for description purposes. The hull 7 and keel 3 can be of any size. The width of the hull 7 in relation to the keel 3 can vary and the shapes of the hull 7 and keel 3 can vary.

Claims

A hull and keel and characterised in that the keel 3 has enough buoyancy to support its own weight, including any ballast, and enough additional buoyancy to support the weight of the hull 7 to which it is attached so that, in use, the hull rests on or near the surface of the water.
2. A hull and keel as claimed in claim 1, in which at the position where the hull and keel meet, the hull has surfaces to each side of the keel that are disposed in a substantially horizontal flat plane.
3. A hull and keel as claimed in claim 1, in which surfaces of the hull adjacent each side of the keel exhibit a measure of upward inclination which depart from a horizontal plane.
4. A hull and keel as claimed in claim 2 or 3, in which said surfaces lie on or near the surface of the water.
5. A hull and keel as claimed in claim 4, in which said surfaces lie above the surface of the water.

6. A hull and keel as claimed in any one of claims 1 to 4, in which the length of the keel exceeds five times the width of the keel.
6
7. A hull and keel as claimed in any proceeding claim when made from plastics reinforced with carbon or glass fibres, or wood or steel, or a combination of these or other materials.
8. A hull and keel substantially as herein described with reference to and as illustrated in the accompanying drawings.
9. A boat when provided with a hull and keel as claimed in any one of the preceding claims.