AU664324B2 - An adjustable foil shaped keel for sailing vessels - Google Patents

Description

r 664324 COMMONWEALTH OF AUSTRALIA PATENTS ACT 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT to 0 0 o e o o oo 0 o 00 0 0 0 4>40 a 0 ro u0 0 Q 0 0

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G oo e0o o0 ea 00 0 o o An Adjustable Foil Shaped Keel for Sailing Vessels 0004 The following statement is a full description of this invention, including the best method of performing it known to me:- 4 P cBF~/O49F.

1A AN ADJUSTABLE FOIL SHAPED KEEL FOR SAILING VESSELS Field of the Invention This invention relates to a keel for sailing vessels, and particularly to a foil shaped keel that is dynamically adjustable to provide control over the performance of the keel through the water.

Description of the Prior Art The primary function of a keel is to counteract the sideways component of the forces applied to a sailing vessel which cause sideways slipping of the vessel through the water when sailing in any direction other than directly before the wind. There is also a secondary but important effect, in that a keel serves to counteract 000 *000o 0 0 00 0 0 0 0 0 O a o o0 D ooI 0 00 ,0 a oa DO o 0.00 0 0 00 00 0 0t0 0 0 00 a *0 oo a O 00 00 0 0400 0010 001 I0 forces acting on the sails which over, and so prevents or lessens The performance of a keel i and lift. Drag is approximately keel (but is also dependent to a the surface finish of the keel).

provided by the keel as it moves the keel shape or profile. This 20 Designers of keels seek to amount of drag, however even:the would tend to cause the vessel to heel the chance of capsize.

s typically characterized by its drag proportional to the wetted area of the lesser extent on other factors such as Lift is the hydrodynamic force through the water and is determined by is analogous to an aircraft wing.

gain maximum lift for the minimum best designed keels cannot generate sufficient lift to fully counteract the sidewards drift component, in which case a vessel will always drift away from its intended heading.

Thus for example, if a yacht is tacking towards a mark, the yacht does 25 not point as high as would be the case if more lift could be generated.

An example in the prior art of a variable foil keel is disclosed in U.S. Patent No. 4,074,646.

The present invention is directed to a keel that can provide 30, increased lift over conventional keel designs for minimri drag. In this regard a keel constructed in accordance with the preferred embodiment of the present invention can provide a 20% greater lift than that of a conventional keel whilst also providing a 30-40% reduction in wetted area.

Summary of the Invention The invention contemplates an adjustable foil shaped keel that allows control over lift both in the positive and negative sense to, w 1) c' 2 respectively, stay closer to the apparent heading or to promote drift away from the apparent heading.

According to one aspect of the present invention there is disclosed a foil shaped keel for a sailing vessel, comprising: an internal structure having a pivotably controllable element; a pivoting nose section carried by the internal structure forming the leading edge of the keel; and an outer skin forming two flexible side walls of the keel, the outer skin extending from said leading edge through to the trailing edge of the keel on both sides of the keel, and the forward edge of the side walls each having an edge margin that is slidably received into the nose section and the rearward edges of the side walls being fixed to said trailing edge, the keel being adjustable in shape by pivoting of the controllable element such that one side wall increases in length by sliding outwardly from the nose section thereby reducing the respective edge margin, and the other side wall decreases in length by the outer skin sliding inwardly into the nose section thereby S increasing the respective edge margin, and the nose section pivoting in sympathy with movement of the side walls.

Brief Description of the Drawings Embodiments of the invention now will be described with reference S4tto the accompanying drawings, in which: Fig. 1 shows a side elevation of a yacht incorporating a keel constructed in accordance with the invention; 25 Fig. 2 shows a top view of a sailing vessel and keel adjusted for improved lift performance; 0*00 0 0 Figs. 3a and 3b show cross-sectional views of a keel embodying 0 the invention; and o 0 0 Fig. 4 shows another keel embodying the invention also in a cross-sectional view.

Detailed Description of Preferred Embodiments Nhile the embodiments will be described with reference to a yacht, the invention also finds application in any other form of sailing vessels, including sailboards or sail powered canoes.

Furthermore, it is possible for the invention to be applied to powered marine vessels that otherwise may drift from their course through the interaction of wind with the vessel's superstructure.

rF -7 -3- Fig. 1 shows the typical outline of a medium sized yacht of the type having a fixed keel. The yacht basically comprises a hull having a mast step 12 located near the foredeck area. The keel 14 of the preferred embodiment is fixed to the hull 10, typically extending to a depth some metres below the yacht's water line. A lead ballast 16 is connected to the lower end of, and extends sternwardly from, the keel 14. The ballast 16 serves the purpose of providing additional counteracting force acting against the tendency of the yacht to heel over when reaching or beating. The yacht's mast and rigrjing is not shown.

Fig. 2 shows a top view of the sailing vessel 10, showing the cross-sectional shape of the foil shaped keel 14 in phantom. The vessel's heading is indicated with respect to the wind direction, which is from the starboard aft quarter. Here a conventional keel utilised in the same situation, the vessel 10 would tend to slip away from its heading in the direction of the wind. The keel 14 has been adjusted so that the starboard side wall 18 is extended in length with respect to the port side wall 19, thereby inducing lift in a direction that generally counteracts the sideways slip, hence maintaining the vessel on its true heading. The degree of lift is adjustable by manipulation 4 of the foil shape of the keel 14. Therefore, the yachtsman sailing the o ship can continuously adjust the lift with respect to the wind direction and strength to have complete control over the desired heading. Indeed, if the keel was adjusted in the opposite sense, then the lift induced would compound the slip due to the wind, hence the rate of slip of the vessel would increase, as may be desirable in some circumstances.

Figs 3a and 3b show the configuration and operation of the keel 14 in more detail. The keel 14 comprises a number of internal structural members 22 about which is formed a flexible outer skin. The structural members 22 typically are made from a complex steel material, such as Saff 2205 steel. Such a composite material exhibits a and corrosion.

BFD/152K r -I 1 4- The outer skin is made from two sheets of polycarbonate material or stainless steel, with each sheet constituting one of the side walls 18,19 of the keel. The side walls 18,19 extend between a rigid nose section 20 and the tail or trailing edge of the keel. The side walls 18,19 are fixed to each other by screws 24, for example. The side walls 18,19 are not fixed to the tail member 28, since they must move with respect to the tail member in adjustment of the keel 14, as will be described. It is equally the case that the outer skin of the keel can be formed of a single sheet.

Fig. 3a shows four slider members 30-33 that are fixed to a respective inner surface of the side walls 18,19. The slider members 30-33 stand the side walls 18,19 away from the structural members 22.

The bevelled surfaces of the slider members 30-33 engage and are free to slide upon similarly bevelled surfaces 24-27 of ones of the structural members 22.

The leading edge of the side walls 18,19 are received inside of the nose section 20, as best seen in Fig. 3b. The rigidity of the side walls 18,19 ensures a water-type fit between the leading edges thereof and the rear edges of the nose section 20. The nose section 20 also is pivotably mounted, and hence can pivot in sympathy with movement of the side walls 18,19.

The side walls 18,19 can be deformed under control of the controlling actuator 23 connected with the tail member 28. The controlling actuator 23 is caused to rotate by means of a mechanical linkage, connected with a controlling lever in the cockpit of the vessel, thus deflecting the tail member 28 into the position shown in Fig. 3a.

Deflection of the tail member 28 causes the side wall 18 to be extended in length by being drawn out from the underside of the nose section 20, as best seen in Fig. 3b. At the same time, the side wall 19 is shortened in length by retraction withir the space to the underside of the nose section 20, again as best seen from Fig. 3b.

This means that the effective length of the starboard side wall 18 is longer than that of the port side wall 19, hence generating lift directed to the starboard side of the foil shaped keel 14.

BFD/152K r 7

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Also as can be noted from Fig. 3b, the port sliders 30,33 have moved upwardly on the bevelled surfaces 24,25, whilst the sliders 31,32 have moved downwardly on the respective bevelled surfaces 26,27.

Interaction of the side walls 18,19 with the nose section causes a net starboardly directed force to be applied to the nose section 20, thus causing it to pivot in an anticlockwise sense, as indicated by the shadowed arrowheads. Pivoting of the nose section is advantageous, in that it improves the hydrodynamic foil-like performance of the keel 14, particularly with respect to drag. It further ensures that no gaps open between the leading edges of the side walls 18,19 and the rear edges of the nose section 20 that otherwise would degrade performance of the keel.

As noted above, it is possible to create lift to counteract the tendency to drift downwind, and so allow the yacht to be pointed higher into the wind. It is equally possible for negative lift to be implemented to promote drift. One instance where it would be desirable to increase negative lift is where the yacht is being sailing directly downwind, and that heading is not directly to a mark, in which case it would be possible to gain the benefit of maximum boat speed whilst running before the wind and still slipping towards the mark during the run.

Fig. 4 shows another embodiment of the keel. Like-integers have been identified by the same reference numerals as is the case in Figs.

3a and 3b.

This embodiment differs primarily in the means by which the sides 18,19 are stood-away from the structural members 22. The slider O:4, arrangement of the previously described embodiment has been replaced by four sets of simple linkages. The linkages each comprise a bracket :0 35-38 fixed to the inner surface of a respective side wall and a link member 40-43 pivotably fixed at one end to a respective bracket, and at the other end thereof fixed to a point on the structural members 22.

Operation of the keel 14 shown in Fig. 4 is the same as for the embodiment shown in Figs. 3a and 3b. As the actuating controller 24 pivots, the side walls 18,19 assume the desired shape, whilst the linkages similarly pivot in sympathy with movement of the side walls.

The slider mechanisms and linkages shown in Figs. 3a, 3b and 4 can either extend the full depth of the keel, else be placed at discreet intervals throughout the depth of the keel.

BFD/152K 1 -6- The embodiments described show a single actuator 23, however the number of actuators that typically are required to configure the outer skin to a desired shape at any given time can be greater than this number, particu'arly if the keel is very large. Therefore, it is possible for the mechanisms or linkages to be powered to assist in displacing the outer skin inwardly or outwardly, thereby to push or pull the outer skin into the desired shape.

Control of the actuator 23 (and optionally the linkages also) can be by pneumatic or hydraulic control, with the control lines being computer controlled in accordance with a series of preferred keel profiles built up by trial and experimentation. The crew of the yacht can therefore select any one of a number of profiles dependent on the lift required, being in a range from maximum lift to promote the highest pointing, through to full negative lift, in which case maximum drift would be achieved.

Indeed, control over the shape of the foil keel can operate on the basis of less conventional control techniques, including constructing the outer skin from a metalisized plastics layer which can function as a bimetallic strip, in which case movement is obtainable by electrical control. This provides a weight saving in the yacht by dispensing with hydraulic or pneumatic supply and regulating equipment.

It will be appreciated that numerous alterations and modifications, as would be apparent to those skilled in the sailing arts, can be made without departiing from the basic inventive concept.

All such alterations and modifications are to be considered within the scope of the present invention. For example, a vessel can be provided with twin keels, the profile of each of which can be altered.

SD a i BFD/152K

Claims (8)

1. A foil shaped keel for a sailing vessel, comprising: an internal structure having a pivotably controllable element; a pivoting nose section carried by the internal structure forming the leading edge of the keel; and an outer skin forming two flexible side walls of the keel, the outer skin extending from said leading edge through to the trailing edge of the keel on both sides of the keel, and the forward edge of the side walls each having an edge margin that is slidably received into the nose section and the rearward edges of the side walls being fixed to said trailing edge, the keel being adjustable in shape by pivoting of the controllable element such that one side wall increases in length by sliding outwardly from the nose section thereby reducing the respective edge margin, and the other side wall decreases in length by the outer skin sliding inwardly into the nose section thereby increasing the respective edge margin, and the nose section pivoting in sympathy with movement of the side walls.

2. A keel as claimed in claim 1, wherein the outer skin is formed of two parts, each part forming one of the side walls.

3. A keel as claimed in either one of claims 1 or 2, wherein the outer skin is spaced away from the internal structure by a plurality of adjusting support means, and whereby each support means allows movement of a respective side wall with respect to the internal structure.

4. A keel as defined in claim 3, wherein each support means comprises a slider member fixed to the outer skin and having a bevelled o0 surface that slidably interacts with a surface of the internal Sd structure. Q0 0 Sdo

5. A keel as claimed in claim 3, wherein each support means comprises a ivotable linkage.

6. A keel substantially as herein described and as shown in Figs. 3a and 3b of the accompanying drawings.

7. A keel substantially as herein described and as shown in Fig. 4 of the accompanying drawings.

8- 8. A sailing vessel having a keel as claimed in any one of claims 1 to DATED this TWENTY SECOND day of AUGUST 1995 Anthony John Dickson Patent Attorneys for the Applicant SPRUSON FERGUSON 444~ 00~ 0e .4 4' 40 4 o 0 4 o St 0 44 0 4 0 4 SO o 0 004 1 0 0 *04 4 0000 0 0 4 00 0 0 04 0 o 0 00 B FD /1:52K AN ADJUSTABLE FOIL SHAPED KEEL FOR SAILING VESSELS Abstract An adjustable foil shaped keel for sailing vessels is disclosed. The keel (14) has an internal structure including a pivotable tail member The tail member (28) pivots under control of an actuator (23) to adjust the shape of the outer skin of the keel (14) formed by two side walls (18,19). The leading edges of the side walls (18,19) are slidingly received underneath the rear edge of a nose section The nose section (20) is pivotable by adjustment of the tail section (28) the length of the starboard side wall (18) increases by extending outwardly from the nose section whilst the port side wall (19) decreases in length by withdrawing into the nose section thus generating increased lift essentially in the starboard direction. 3i (Fig. 3a) I4 0 Ii e a 0 *i a o o BFD/152K