GB2238766A - Reducing leeward drift in sailing vessels - Google Patents

Abstract

A sailing vessel of the yacht type having two struts (1) firmly attached to the underside and centre line of the hull, one forward and the other aft, each supporting a rudder (2). Each strut may suspend the forward and aft end of a ballast weight (3). The vessel may have sleeves or cases enabling the struts and their associated rudders to be telescoped into the hull either singly or in unison. <IMAGE>

Description

0.9 t I Improvements in the performance. of.Yachts and dinghies' This

inven:ion relates to Sailling vessels such as yachts and dinghies and provides improvements therein, which will substantially reduce leeward drift when under sail and will otherwise improve their performance and, maneuverability.

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 addition, a keelson. Tn the case of a dinghy a centre board is used.

For keels and centre boards-to reduce leeward drift, they must be set at an ang."Le of i.n.cialence by the action of a rudder. This means that the huli is dA.so Lurned at this angia and the boat will travel crab-fashion throuah the water.

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

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 1-ine 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 saiiing vessel including a hull and two elongated struts, a,,,zending downwardly 4 is 1 p 1 from the under side and on the.1 i,lie ()F the-, I-jul-j. ariti disposed respectively fc.)i-wai.-(] ai-jel apt- (.,I- tile 111,11. Irlle. sti.ilts suspend a ballast weight and a rudde.l. is assc)ciaLedi With eaCII strut.

More spec if!.call y, there is provIded a hull with two vane shaped struts which are attached to the on ti.ie centre line. The struts are gerierally of aerofoi I section and each has an associated rudder. The struts way have a ballast weight mutually supported or a separate ballast weight supported by each of the struts. The strilts, can be pivoted at the. attachment to the bal-last and each Stú1.11: Ilitly I.M WILIAL.11-Clwn i.itLO the hull.

into a casing or sle-eve provided in the liti-i'l. The withdrawal of the struts makes 1ht. vessel. (-.asic-i: to 1.i.-aiisliorL 011 land and facilitate sail illg in shallow Watec. Likewise, i f the ballast weight.s come into contact wIth Lhe ground during sailing they can be rai.sed Ic freethe vessel..

A better understanding inay be obtai.ried by reference to the accompanying drawings in which..

Fig.1 shows two struts each with a rudder and supporting a single ballast weight.

Fig.2 shows two struts (--a(--.]i wiLli a rudder and ballast weight Fig.3 shows two struts each with a rudder buL without 1)allast-. vj(:!icjtit-.

Fig.4 is a plot (jlj the paths that. wotild be followed by an orthodox anti a equipped vessel., according to the:invention in trave.I.I.ing from 1:)oint A to is.

1 T k Fig.1 shows a vessel huLl. provided with two struts 1, each with an associated rudder 2. The struts and the rudders 2 can be raised up into the hull. within casiligs 5. Any suitabl.e means can be provided to raise the struts 1.

The rudders 2 can be controll.ed by any convenient method so as to be operated together or independently, as required.

The ball.ast means 3 c)j.. 4, associated with the struts can be of any shape, the preferred shape is aerofoil. section so that a vertical. 1ift is given to the vesse.i. when:it is undel: way.

Fig.2 sho..s two ball.ast weights 4 respectively associated w.i Lli uach s Lrut 1. lllli.is arrangement- Js adopted when the struts are to be wide. 1y spaced.

Fig.3 applies to vesse-l.s tstjcli as dinghies or skiffs, which use human mass to provide the retaining moment against the overturning moment, produced by the actlon of the wind on the sail.s of the vesse.I.

Fig.4 is a diagram of two vesse1.s sailAng between point A and point B. In explanation it is best Lo Awagine reaching, ie. sailing cross-wind, away from the vic-vic-.r with the wind blowing from I.eft 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 firi.isli at. point B, inust aim at the point C. This is because it. is not travelling through a solid medium and external. forces such as the wind, wil.l. illo7e it sideways and it will drift tlirough the water. ']"lie drift over the journey AC is CB 1 a C 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 sLerji 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 riot designed and which is very inefficient elue to the increase in drag.

The keel of vessel 0 has lift to windward]A, while the rudder has lift to leeward L2. Lift 1,1 must therefore be great enough to equal. W + 1.2, showing that the rudder joins the wind in loading up the work done by the keel or centre board, which consequently must be larger than necessary.

The use of -two strilts -1. and the associated rudders 2 as proposed by this invention, means that 1, need only equal W.

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

The effect is slittilarly beneficial, if water current is flowing from left to right in the aPplication shown in Fig.4. Steering and manoeuvrability are also improved by the invention.

- 4 h A - C 6 The claims defining the invention are as follows:

1. A sailing vessel of the yacht type having two struts firmly attached to the underside and centre line of the hull, one forward and the other aft, each supporting a rudder and suspending the forward and aft end of a ballast weight.

2. A sailing vessel of the yacht type having two struts firmly attached to the underside and centre line of the hull, one forward and the other aft, each supporting a rudder and suspending part of the ballast weight.

3. A sailing vessel of the dinghy type having two struts firmly attached to the underside and centre line of the hull, one forward and the other aft, each supporting a rudder.

4. A sailing vessel having two struts firmly attached to the underside and centre line of the hull, one forward and the other aft, each supporting a rudder; the vess,7-,! being provided with sleeves or cases to enable the struts and their associated rudders to be telescoped up into the hull, singularly or in unison.

published 1991 at The Patent Office. State HOuse.66/71 High Holborn. LondonWCIR47P. Further copies may be obtained from Sales Branch, Untt6, Nine Mile point, Cwmklinfach, Cross Keys. Newport. NPI 7HZ. Printed by Multiplex techniques ltd. St Mary Cray. Kent.