GB2098137A - A sailing craft - Google Patents

Abstract

A sailing craft is supported by at least three spaced disc-shaped floats 1, 2, 3 mounted in fixed relation to a superstructure and has a sail or aerofoil which in use remains in fixed relation to the superstructure. A pair of combined rudder and keel elements are disposed at either side of a line representing the resultant wind force, each of the rudder and keel elements being independently turnable around a vertical axis. A telescopic aerofoil is described. <IMAGE>

Description

SPECIFICATION A sailing craft This invention relates to a sailing craft and more particularly to sailing craft comprising a superstructure mounted on and interconnecting a plurality of floats the centres of which form corners of a polygon, wind actuated propulsion means rigidly mounted on the superstructure in fixed relation thereto, and steering and stabilizing means.

USA Patent No. 1303839 describes a sailing craft comprising a plurality, for example three, torpedoor boat-shaped hulls connected together by a skeleton framework carrying a sail supporting structure which is fixed in relation to the framework. The hulls of this craft are independently pivotable about a vertical axis. Thus, the hulls serve as floats to support the craft, as keels for stabilizing course and counteracting leeway, and as rudders for steering the craft. The sails of this known craft are mounted in the sail supporting structure without adjustable sheets so that any adjustment of the sails to obtain a required angle to the wind is performed by turning the hulls in relation to the framework and steering the craft on a desired course, using the hull nearest to a line through the centre of the craft as a turnable rudder.

This known craft has some substantial disadvantages. For example the steering system is rather complicated because three different hulls are selectively used as rudder depending on the position of the craft in relation to the course, i.e. the angle between the centre-line of the craft and the course.

So, it is necessary to provide for changing from one hull (rudder) to another, but it is also difficult to foretell the steering action, as the hull operating as rudder sometimes is the foremost and sometimes the hindmost hull.

The most serious problem is, however, to obtain a satisfactory connection between the framework and the turnable hulls. As the hulls must have a considerable length/width ratio for proper performance the hulls act as levers, and in a heavy sea the waves apply considerable forces which will strain the supporting connections and impede turning of the hulls or even break the turning mechanism.

It is also to be mentioned that a multiple hulled craft of the class described is similar to other multi-hulled craft like catamarans and to traditional mono-hulled sailing vessels in that it has to tack during normal manoeuvring, so that the wind sometimes strikes the starboard side of the sails and sometimes the port.

According to this invention there is provided a sailing craft including a superstructure mounted on and interconnecting three or more floats the centres of which define corners of a polygon, wind actuated propulsion means rigidly mounted on the superstructure in fixed relation thereto, each of said floats comprising a disc mounted in fixed relation to the superstructure and having low resistance against movement at a water surface in horizontal direction, said resistance being substantially independent of the direction of horizontal movement, and steering and stabilizing means comprising at least one elongate profiled member extending down into the water and pivotally and/or displaceably mounted beneath the superstructure so that the torque exerted thereby with respect to the centre of said polygon, and created by the water resistance on the member or members, can be adjusted in magnitude and direction.

As the floats are discs, i.e. symmetrical or substantially symmetrical bodies having relatively small areas in any vertical cross section in comparison with the horizontal cross sectional area, there is no need for turning the discs, because they have almost the same low resistance against movement at a water surface in any horizontal direction. Therefore, the floats can be simply and strongly mounted in fixed relation to the superstructure.

The discs are preferably solids of revolution having a vertical axis. A preferred float comprises a pair of domed shells defining a cavity containing air under pressure or a porous buoyancy material and stiffening ribs or sheets.

Instead of a circular horizontal cross section the discs can have an alternative form, for example a hexagonal or quadratic section with rounded corners.

The preferred number of discs is three, positioned in the corners of an isosceles or equilateral triangle.

Another possibility is four discs defining a rectangle, trapezoid or rhombus.

The wind actuated propulsion means can be a fixed mounted sail, for example a rectangular sail extended between two vertical masts. Preferably an aerofoil is used, however, as this gives the highest obtainable wind force per square metre.

Aerofoils have to some extent been used in mono-hulled sailing vessels and in catamarans. As the wind comes alternately from either side, such aerofoils must be symmetrical with respect to the chord line, which is rather inefficient. In the present craft however the wind during normal manoeuvring comes from one and the same side of the sail or aerofoil. For this reason a very efficient profiled aerofoil can be used having a convex leeward or front side and a plane or concave windward side or rear side. A profile of this type has an optimal angle of attack, i.e. inclination between the chord line and the relative wind direction, of 10-20q but angles as low as 0 are still possible, enabling a course to be sailed very close to the wind.

When the steering means comprises a pair of combined rudder and keel elements they are mounted so as to be independently turnable around a vertical axis disposed at either side of a vertical plane defined by the resultant wind force on the wind propulsion means, so that a positive or negative torque with respect to the centre of the craft can be obtained by turning one of the rudder and keel elements while the other element is kept stationary, or the two elements can be turned in opposite directions.

The craft can also be steered and held on a desired course with one rudder or keel profiled member only, in which case the profile is adjusted to a desired angle with respect to the resultant wind force, and the turning effect is obtained by moving the profile across a vertical plane through the resultant wind force from one side to the other to obtain a positive (counter clockwise) or negative (clockwise) torque.

Two rudder profiled members disposed at either side of the vertical plane defined by the resultant wind force can also have both vertical and horizontal axes, in which case the members are adjusted parallel to each other at an angle to the wind force determined by the desired course. The steering effect is obtained by turning one or both of the profiled members about their horizontal axes.

One embodiment of the invention will now be described by way of example with reference to the diagrammatic drawings, in which Figure 1 is an elevation of a craft according to the invention, shown on a water surface.

Figure 2 is a plane view of the craft shown in Figure 1, Figure 3 is a side elevation of the craft shown in Figure 1, Figure 4 illustrates one form of propulsion means comprising telescopical sections, having an aerofoil profile and seen in side elevation, and FigureS is a front view of the aerofoil shown in Figure 4.

The craft illustrated in Figures 1 to 3 comprises a superstructure consisting of an elongate main frame 4 connected to a front arm 5. To opposite ends of the main frame 4 are firmly connected disc floats 1, 2 respectively via supporting rods 13, 13a and 14, 14a.

To the forward end of the front arm 5 a similar disc float 3 is firmly connected by supporting rods 15, 16.

The centres A, B, C of the disc floats form corners of an equilateral triangle, the three sides of which are illustrated by the dotted lines AB, BC, CA and having the centre of gravity at point L on the centre-line m.

Two profiled members 6, 7 are pivotally mounted about respective vertical axes 10, 11 in bearings 8, 9 connected to the front side of the main frame 4. The member 6 is offset to the left of the centre-line m and the member 7 is offset a similar distance to the right of the centre-line m. Each of the members 6,7 is provided with turning means (not shown), such as tillers or cables connected to wheels. In a preferred embodiment the two members are both coupled to a single wheel, so that the profiled members are turned simultaneously and are always parallel dur ing turning of the wheel. The profiled members are swivellable about respective horizontal axes 18, 19 and means (not shown) is provided for swivelling the members independently around these axes.

The aerofoil 12 has a convex front side 20 and a concave rear side 21 and is mounted in a vertical position and in fixed relation to the main frame 4, the chord line c lying at right angles to the centre-line m and at a predetermined distance from the centre L.

In a sailing position the craft should always have the wind w directed against the concave rear face 21, i.e. the wind angle v relative to the chord line c should have a value between 0" and 180 . The range 10-20" and the range 160-170" are preferred during tacking as the resultant wind force p will be optimal.

The wind w acts on the aerofoil 12 with a number of pressure and frictional forces giving a resultant forcep passingthrough the centre of pressure F in direction of the line k. By suitable positioning of the aerofoil 12 the line k will always pass through or near the centre L independently of the angle v. If the angle v is 90 the line k lies exactly on the line m. At small angles, i.e. v = 10-20 , the centre F will be displaced to the right but the line k will assume an inclination x, so that the two lines k and m will intersect each other approximately in the point L.Provided that the three disc floats are identical and have same water resistance the torque around the point L, produced by the force p, will be very small or zero. Atorque of a controlled direction and magnitudeforturning is produced by means of the profiled members 6, 7.

Each profiled member produces a torque around the point L in opposite direction and normally of the same magnitude, i.e. when the profiles are parallel to each other and have equal areas immersed in the sea, so that the two torques equal one another.

The force p is resolved into the two forces a and b, the force a being parallel to the line I containing the chord of the profile 7, and the force 12 at right angles to the first mentioned force a. The force a pulls the craft on a steered course /without introducing significant torques, since the water resistance of the profiled members 6,7 is small in the direction of 1.

The force h is in equilibrium with the two drag forces each acting from the water on the two respective members 6 and 7 at right angles to the chords of the members, and producing opposite directed torques around the point L. One of the other torques can easily be changed with respect to the other, either by turning for example the member 7 around the vertical axis 9 or around the horizontal axis 19. In the first instance the moment arm is changed, and in the other instance the magnitude of the force is changed as the effective area of the immersed profile changes.

It will be realised that both forces a and 12 depend on the angle y. If the angle y is 90 the force a will be zero while the force b will be equal top, and the craft can be kept head to the wind, slowly drifting in a controlled position to the wind. Any tendency to turning can easily be corrected with slight adjust ments of either of the profiled members about their axes 8,9 or 18, 19. Any decrease of the angle y will produce a force a to the right with respect to the line k, and any increase of the angle y (above 90") will produce a similar force directed to the left of line k.

The force b will always lie on the opposite side of line k. It will be understood that this steering system provides for very simple and easy manoeuvring, as the steering forces are independent of the speed of the craft. The craft can be brought to a stop almost instantaneously and the course can be changed and reversed with small and fast movements of the profiled members.

In order to avoid excessive braking effects which would strain the profiled members 6,7 or other parts of the structure and be hazardous or inconvenient for the crew, shock absorbers can be inserted at the horizontal axes 18, 19, do that the members yield and turn around these axes when predetermined maximum forces on the profiles are exceeded. Such shock absorbers may be in the form of bellows or springs.

As illustrated in Figure 3 the resultant wind forcep creates a torque around the point M which is counter-balanced by the oppositely directed torque from the force buoyancy of the disc 3) acting in the point C. Due to the very long arm CM this torque can be very large, and hence the stability of the craft is extremely high. The aerofoil 12 has a number of telescopically mounted sections 32-36 so that the height of the structure can be reduced as shown in Figures 4 and 5.

The upper section 32 of the aerofoil 12 is connected to a firmly horizontal mounted bottom section 31 via a hinge 37 having a horizontal axis parallel to a chord of the aerofoil profile and cables 40 fastened to connecting means 39 at the rear side of the aerofoil 12 and extending through dumb sheaves or blocks 38. The cables 40 are connected to springs 41 so that the section 32 is pressed against supports 42. The tension in the springs 41 is adjusted to counter-balance a predetermined maximum tor qua swithin the stability range caused by the wind force p so that the aerofoil 12 will yield and turn about the hinge 37 during abrupt e cessive gust of wind.

The area of the aerofoil 12 is adjusted in accordance with the average wind force by means for contracting the sections 32-36 telescopically. The contracting means may be in the form of hydraulic cylinders or a scissors structure (not shown), mounted inside the hollow sections.

The steering members 6,7 are shown in Figure 2 as having plane front side and convex rear side in order to reduce leeway to a minimum.

The sailing course of the craft is adjustable within any angle up to and greater than 45-30 to the wind, or even closer if limited speed is accepted. When the propulsion means is an aerofoil having a plane or concave rear side the wind must always strike this side, and hence all turnings shall take place as veering, the angle v changing in the range 0-180".

This is no disadvantage, however, as a turning is performed very quickly and almost without losing height.

With reference to Figure 2 the angle u represents the course in relation to the wind direction. This angle is determined by the formula: u = v+z wherein v is the angle from the chord to the wind direction, and z is the angle from the chord to the course line.

If the angle z is O" (or rather equal to the small angle x) the steering members 6,7 are positioned at right angles to the driving wind force and the speed is zero (or equal to the drifting speed which is small as the steering members act as keels). In order to obtain a reasonable speed the angle z should for practical reasons differ from x by at least about 20 .

The possible range for z is therefore 20-160 , and the preferred range is 30-150". As the angle v can differ from 0 to 180 , preferably 10-170 , the possible range for the course angle u will be 20-340 , and preferably 40-320 . It will be understood that the angle u is the steered course which normally will differ more or less from the course made good (course in relation to the water) due to drift.

The illustrated craft has excellent sailing qualities with easy handling and simplified steering, and has a high degree of stability and resistance to capsizing.

The construction is strong and seaworthy even in heavy seas.

Claims (11)

1. A sailing craft including a superstructure mounted on and interconnecting three or more floats the centres of which define corners of a polygon, wind actuated propulsion means rigidly mounted on the superstructure in fixed relation thereto, each of said floats comprising a disc mounted in fixed relation to the superstructure and having low resistance against movement at a water surface in horizontal direction, said resistance being substantially independent of the direction of horizontal movement, and steering and stabilizing means comprising at least one elongate profiled member extending down into the water and pivotally and/or displaceably mounted beneath the superstructure so that the torque exerted thereby with respect to the centre of said polygon, and created by the water resistance on the member or members, can be adjusted in magnitude and direction.

2. A craft according to claim 1, wherein the steering and stabilizing means comprises a pair of combined rudder and keel elements disposed at either side of a vertical plane defined by the resultant wind force on the wind actuated propulsion means, each of the rudder and keep elements being independently turnable around a vertical axis.

3. A craft according to claim 1, wherein the steering and stabilizing means comprises one profiled member swivel la ble about a vertical axis and movable from one side to the other of a vertical plane defined by the resultant wind force on the wind actuated propulsion means.

4. A craft according to claim 1, wherein the steering and stabilizing means comprises two profiled members disposed at either side of a vertical plane defined by the resultant wind force on the wind actuated propulsion means, said members being simultaneously adjustable at any desired angle to the wind force and independently turnable around a horizontal axis or movable in a vertical direction to have different areas of the profiles immersed in the water.

5. A craft according to any one of claims 1 to 4, wherein the wind actuated propulsion means comprises at least one vertically elongate aerofoil comprising an inflatable tubular body of a bendable, airtight material closed at both ends and filled with compressed air.

6. A craft according to claim 5, wherein the aerofoil has a convex front side and a plane or concave rear side.

7. A craft according to any one of claims 1 to 4, wherein the wind actuated propulsion means comprises a plurality of telescopically interconnected sections and means for relative displacement of said segments in the vertical direction.

8. A craft according to any one of claims 1 to 7, wherein the disc floats each comprise a pair of domed shells defining a cavity containing compressed air or a porous buoyancy material and stiffening ribs or sheets.

9. A craft according to claim 8, wherein the disc floats are connected to the superstructure through bellows in order to moderate movement of the superstructure due to the action of waves on the disc floats.

10. A craft according to claim 8. wherein the disc floats have hydrofoils mounted under them.

11. Asailing craft substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.