AU628096B2

AU628096B2 - Improvements in the performance of yachts and dinghies

Info

Publication number: AU628096B2
Application number: AU43973/89A
Authority: AU
Inventors: Ernest Thomas Ashman
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-12-15
Filing date: 1989-12-07
Publication date: 1992-09-10
Anticipated expiration: 2009-11-02
Also published as: AU4397389A; GB8927657D0; FR2655609B1; GB2238766A; DE3940703A1; GB2238766B; FR2655609A1

Description

MO I ftm" P/00/Oil farm PATENTS ACT 1052 COMPLETE SPECIFICATION

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FOR OFICE U 2809 Short Title: Int. *Application Numb.r: Lodgedt 4Complete Spolficatfont-Lodg&Ji: Acceptod:.

Lapsed: Publishie'; Priority: Related Art: *Name of Applicant: Address of Applicant., Actual Inventor: TO BE COMPLETED BY APPLICANT Erne5+ Thomacs t4 w A) Cis c0v9woa St.

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Complete Specification for the Invention entitled: 4 +11e p 1 o4- -ycCh+S cgr'd dtq l The following statement Is a full description of this Invention, Including the best method of performing It known to Mo.-" Note., The description It to be typed In double spacing, plea type face, in an area not exceeding 250 mim In depth and 160 mm In width, an tough white paper of good quality and It io to be Inserted Inside this form.

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*5 This invention relates to sailing vessels such as yachts and dinghies and provides improvements therein, which will substantially-reduce leeward drift when under sail and will improve their performance and manoeuvrability.

The usual method of preventing the wind from blowing a yacht to leeward and causing drift, is to use a large keel and often in additioni, a keelson. in thO; case of a dinghy a contre board is used.

For keels and centre boards to reduce leeward drift, they must be set at an angle of incidence by the action of a rudder.

This means that the hull is also turned at this angle and the boat will travel crab-fashion through the water.

Leeward drift produces water pressure on the leeward side of the keel and the pressure is increased by reaction from 15 the rudder, which is set in the opposite direction to maintain the angle of incidence in the orthodox operation. The result is turbulence and the creation of additional overturning moment, because the force on the keel is acting below water level and below the centre of buoyancy of the hull.

20 Drift, means that the vessel has to sail additional distance in progressing from one point to another. The distance actually sailed is the hypotenuse of a right angle triangle, the other two sides of which represent the straight line distance from the starting point to the required finishing point and the drift of the vessel during its journey.

It is the object of the invention to eliminate the above disadvantages which are associated with vessels having conventional keels or centre boards.

Broadly, the invention provides a sailing vessel including a hull and two articulated keels, extending downwardly.

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from the underside and on,the centre line of the hull and disposed respectively forward and aft of the hull. The keels suspend a ballast weight and a flap is associated with each keel.

More specifically, there is provided a hull with two articulated keels which are attached to the hull on the centre line. The keels are generally of aerofoil section and each has an associated flap. The keels may have a ballast weight mutually supported or a separate ballast weight supported by each of the keels. The keels can be pivoted at the attachment to the ballast and each articulated keel withdrawn into the hull into a casing or sleeve provided in the hull, The withdrawal of the articulated keels makes the vessel easier to transport on land and facilitate sailing the vessel in shallow water. Like- :15 wise, if the ballast weight comes into contact with the ground during sailing they can be raised to free the vessel.

A better understanding may be obtained by reference 99 to the accompanying drawings in which: Fig.l shows two keels each with a flap and supporting a single ballast weight.

Fig.2 shows two keels each with a flap; and ballast weight.

Fig.3 shows two keels each with a flap but without ballast weight.

Fig.4 is a plot of the paths that would be followed by an orthodox and a twin-articulated keel equipped vessel, according to the invention, in travelling from point A to point B.

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S. S *5 0SeO 0 Fig.l shows a vessel hull provided with two keels 1, each with an associated flap 2. The articulated keels 1 2 can be raisedup into the hull with casings 5. Any suitable means can be provided to raise the articulated keels 1 9 2.

The flaps 2 can be controlled by any convenient method so as to be operated together or independently, as required.

The ballast means 3 or 4, associated with the keels can be any shape. The preferred shape is aerofoil section so that a vertical lift is given to the vessel when it is under way.

Fig.2 shows two ballast weights 4 respectively associated with keelt.l. This arrangement is adopted when the articulated keels are to be widely spaced.

Fig.3 applies to vessels such as dinghies or skiffs, 15 which use human mass to provide the retaining moment against the overturning moment, produced by the action of the wind on the sails of the vessel.

Fig.4 is a diagram of two vessels sailing between point A and point B.

In explanation, it is best to imagine reaching, i.e.

sailing cross-wind away from the viewer with the wind blowing from left to right, as shown in Fig.4 and indicated by the arrow W.

The orthodox vessel 0, after setting out from the point A in an attempt to finish at Point B, must aim at the point C. This is because it is not travelling through a solid medium and external forces such as the wind, will move it sideways and it will drift through the water. The total drift over the journey AC is CB.

3 L -L To resist.the wind forces, the keel or centre board must be turned at an angle of incidence so that the horizontal lift created in the water, opposes the wind thrust. With present practice, this is done by moving the stern of the vessel to leeward, with the action of a rudder placed astern. Although the hull assists the action of the keel or centre board, it is very inefficient in so doing and because it is now travelling with an angle of yaw, the vessel is being pushed through the water partially sideways, in a manner for which boats are not designed and which is very inefficient due to the increase in drag.

The keel of vessel 0 has lift to windward LI, while the rudder has lift to leeward L2. Lift L1 must therefore be great,:: enough to equal W L2, showing that the rudder joins the wind in loading up the work done by the keel or centre board, 15 which consequently must be larger than necessary.

The use of two keels 1 and the associated flaps 2 as proposed by this invention, means that L need only equal W.

The hull is free to travel in a true direction without the severe increase in drag and the vessel travels the direct route 20 AB and not the increased distance AC.

The effect is similarly beneficial, if water current 1. is flowing from left to right in the application shown in Fig.4.

Steering and manoeuvrability are also improved by the invention.

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