GB2213446A

GB2213446A - A wind propelled craft

Info

Publication number: GB2213446A
Application number: GB8728707A
Authority: GB
Inventors: James Labouchere
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-12-09
Filing date: 1987-12-09
Publication date: 1989-08-16
Also published as: GB8728707D0

Abstract

A wind propelled craft has an aerofoil surface which may be inclined toward the wind to gain vertical lift and to reduce heeling moment. Its leading edge is constrained to a beam 6 that is pivoted and supported at a first point 8 located rigidly from the craft on a support beam 9 above the centre of pressure of the aerofoil. A second point at the base of the beam 10 is free to travel from one side of the central longitudinal axis of the craft to the other pivoting about the first point 8, also following an arc of a circle centred upon a second point 12 described by a beam 11 pivoted at the second point. <IMAGE>

Description

A WIND PROPELLED CRAFT This invention relates to a wind propelled craft.

As a craft with a sail mounted on an upright mast heels to leeward, the total aerodynamic force acting on the sail has a downward component. This component increases the downward load on the craft, and hence increases drag. Also, the force that can be applied to the sail without the craft turning over is limited by the maximium righting moment that the craft can generate. To increase the maximum force that the sail can accommodate, either the righting moment has to be increased or the heeling moment decreased.

On a sailing boat, the higher that the total aerodynamic force of the sail passes over the hydrodynamic centre of pressure of the submerged surfaces, the greater is the heeling moment. To reduce this heeling moment the sail may be angled so that the total aerodynamic force on the sail passes through or closer to the hydrodynamic centre of pressure of the craft. This reduces the heeling moment, and in inclining the sail, helps take weight of the craft off the water.

To make the craft practical, a system is needed to enable the craft to sail symetrically on either tack.

According to the present invention there is provided a wind propelled craft having as its primary aerodynamic element an aerofoil surface with its leading edge constrained to a beam that is pivoted at a first point located rigidly from the craft in a plane above the centre of pressure of the aerofoil surface, a second point on the beam in a horizontal plane below the centre of pressure of the said aerofoil being free to travel from one side of the central longitudinal axis of the craft to the other pivoting about the first point; the second point at the base of the beam constrained to a locus extending fro;n one side of the craft to the other, the locus passing aft of any structure bracing the first point.

A specific embodiment of the invention will now be described by way of an example with reference to the accompanying drawing in which Figure 1 shows in perspective, the assembled wind propelled craft.

Referring to the drawing the craft comprises a central hull 1 with an outrigger 2,3 on each side supported from the central hull by cross-beams foreward 4 and aft 5, a mast 6 at the leading edge of a sail 7 which is supported at a universal joint 8 on a mast support pole 9 with the base of the mast on a second universal joine 10 which is attached to a beam 11 pivoted about a second point 12.

The base of the mast 10 can travel from one side of the craft to the other on a locus described by arcs of circles centred upon points 8 and 12. The displacement of the base of the beam 10 from the central longitudinal axis is controlled by lengths of rope 13 which pass through pulleys 14 and are adjustably securable in jamming cleats 15. These two ropes 13 may make up a continuous loop. Two more ropes 16 are attached to the sail's trailing edge 17 and are used to control the angle of the sail about the axis that connects the base of the mast 10 to the universal joint 8. These two ropes 16 are adjustably securable in pairs of jamming cleats 17 so that the incidence of the sail and twist in the sail may be controlled.

The outriggers 2,3 are supported from a central hull such that when the craft floats unloaded and one outrigger is touching the water, the opposite one is clear of the water. The outriggers are assymetrically cambered and their longitudinal axes angled so that they lift away from the central hull of the craft when the craft is travelling parallel to its central longitudinal axis, The submerged surfaces on the outriggers toward the lower tip chords 19 are angled downward and toward the central longitudinal axis of the craft so that they provide negative lift when submerged and the craft is travelling parallel to its central longitudinal axis.

The craft may be fitted with hydrofoils 20 that provide vertical lift to provide pitching stability, or lift to enable the central hull to stabilize clear of the water.

With the windward outrigger 2 hooking in the water the hydrodynamic centre of pressure of the craft moves to the windward side. The base of the mast is let out so that it moves to the leeward side, inclining the sail further toward the wind and in so doing angling the total aerodynamic force on the sail so that it passes close to the centre of hydrodynamic pressure on the windward outrigger.

This effect reduces heeling moment to a minimum and takes weight of the craft off the water. The craft sails symetrically on both tacks; the sail base moving across to the opposite side and the opposite outrigger hooking into the water.

A rudder 21 and tiller 22 are provided for directional control with a cloth trampoline 23 to accomodate the crew.

Claims

1. A wind propelled craft having as its primary aerodynamic element an aerofoil surface with its leading edge constrained to a beam that is pivoted at a first point located rigidly from the craft in a plane above the centre of pressure of the aerofoil, a second point on the beam in a horizontal plane below the centre of pressure of the said aerofoil being free to travel from one side of the central longitudinal axis of the craft to the other pivoting about the first point; the second point at the base of the beam constrained to a locus extending from one side of the craft to the other, the locus passing aft of any structure bracing the first point.

2. A craft as claimed in Claim 1 with a control such that the distance of the second said point at the base of the said beam fra. the central longitudinal axis of the craft may be adjustably secured.

3. A craft as claimed in Claim 1 or Claim 2 wherein the said beam is supported at the first point by a pole which is in turn attached to the craft.

4. A craft as claimed in any one of the preceding claims, wherein the locus of the second point is described by the arc of a circle centred upon a third point on the structure of the craft below the centre of pressure of the sail.

5. A craft as claimed in any one of the preceding claims wherein the second point is attached to and may move along a rigid track.

6. A craft as claimed in any one of the preceding claims wherein a control system is provided to adjustably secure the angle of any part of the said . aerodynamic element about the axis connecting the first and second point.

7. A craft as claimed in any one of the preceding claims wherein there is a central hull to which is attached a body on both sides of the hull, the said bodies' bases being above the level of the base of the central hull when the craft is upright.

8. A craft as claimed in Claim 7 and any one of the preceding claims wherein there is net negative hydrodynamic lift on the lower part of the surface of a body displaced from the central longitudinal axis of the craft, when the craft is moving forward and parallel to the longitudinal axis of the craft.

9. A craft as claimed in any one of the preceding claims wherein the longitudinal axis of a body displaced from the central longitudinal axis of the craft is angled so that the it provides hydrodynamic lift pulling away from the central longitudinal axis of the craft when the craft is moving forward and parallel to its central longitudinal axis.

11. A craft as claimed in any one of the preceding claims wherein a component of the hydrodynamic lift on a pitch stabilizin surface is parallel to the yaw axis of the craft.

11. A craft as claimed in any one of the preceding claims wherein a yaw control system is provided.

12. A craft as claimed in any one of the preceding claims wherein an artificial stress maximiser limits the mean forces that can be applied to a keel and sail.

13. A craft substantially as described herein with reference to Figure 1 of the accmpanying drawing.