A CONTROL ARRANGEMENT FOR A WIND POWERED VEHICLE

Abstract

A control arrangement (1) for a kite (6) is attached to a boat (2). Without any external control or energy input the control arrangement (1) automatically tracks the movement of the kite (6) as the kite (6) moves relative to the boat (2). The control arrangement (1) ensures that the kite (6) flies so that the line of action (15) of the kite (6) always extends through the centre of lateral resistance (14) of the boat (2). This enables the kite (6) to pull the boat (2) without applying any heeling moment to the boat (2).

Description

NOTICE OF COPYRIGHTS AND TRADE DRESS

A portion of the disclosure of this patent document contains material which is subject to copyright protection. This patent document may show and/or describe matter which is or may become trade dress of the owner. The copyright and trade dress owner has no objection to the facsimile reproduction by anyone of the patent disclosure as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright and trade dress rights whatsoever.

RELATED APPLICATION INFORMATION

This patent claims priority from International PCT Patent Application No. PCT/GB2013/053232, filed Dec. 6, 2013 entitled “A CONTROL ARRANGEMENT FOR A WIND POWERED VEHICLE”, which claims priority to Great Britain Patent Application No. 1222153.7, filed Dec. 10, 2012 entitled “A CONTROL ARRANGEMENT FOR A WIND POWERED VEHICLE”, all of which are incorporated herein by reference in their entirety.

BACKGROUND

The present invention relates to a control arrangement for a wind powered vehicle and more particularly relates to a control arrangement to control an aerofoil section attached to a vehicle.

A conventional sailing boat incorporates a sail attached to a mast and a boom. The force of the wind on the sail propels the boat along the water. The force of the wind on the sail also applies a heeling moment to the boat which causes the boat to heel to one side. To resist the heeling moment sailing boats have wide hulls and/or carry significant ballast, each of which increase the water resistance against forward motion. The maximum area of the sails is limited by the capacity of the boat to resist the heeling moment.

The speed of a boat can be defined in terms of the Froude number. The Froude number Fr of any boat is calculated using the following equation:

$\begin{array}{cc}\mathrm{Fr}=\frac{v}{\sqrt{{\mathrm{gL}}_{\mathrm{WL}}}}& \left[\mathrm{equation}1\right]\end{array}$

Where v is the velocity of the boat, g is the acceleration due to gravity and L_WL is the length of the boat at the water line level.

A displacement hull moves through the water, displacing the water as it goes, with the boat being supported by hydrostatic lift (buoyancy). A planing hull, on the other hand, skims over the top of the water with the boat being supported by hydrodynamic lift. Due to hydrodynamic effects, the resistance on a displacement hull increases rapidly above a speed of around Fr=0.45. To achieve speeds in excess of around Fr=0.45, the hull must begin to plane to obtain support from hydrodynamic lift forces, instead of from the hydrostatic (buoyancy) forces which dominate at lower speeds.

The length displacement ratio of a boat can be used as a guide to the performance of a boat above a speed of Fr=0.45. The length displacement ratio DLR is calculated using the following equation:

$\begin{array}{cc}\mathrm{DLR}=\frac{L_{\mathrm{WL}}}{{\Delta }^{\frac{1}{3}}}& \left[\mathrm{equation}2\right]\end{array}$

Where L_WL is the length of the boat at the water line level and Δ is the displacement of the boat. As a guide, a sailing boat with a length displacement ratio of less than 5.7 will not plane and will therefore not exceed a speed of around Fr=0.45. As a result of the requirement for a wide hull and/or ballast to resist the heeling moment from the sails, it is very difficult to build standard yachts with a length displacement ratio larger than 5.2. Therefore most yachts are limited to a maximum speed of around Fr=0.45.

It has been proposed previously to power a boat using a kite instead of a sail in order to minimise heeling. One such conventional arrangement is disclosed in U.S. Pat. No. 6,003,457. The kite arrangement disclosed in this document is able to reduce the heeling action on a boat but the driving force from the kite must be controlled actively by an arrangement which adjusts the vertical inclination and plan alignment of an arm to which a kite is attached, this requires external control and energy input. In addition, the steering of the kite and the angle of incidence of the kite to the wind are controlled by a system mounted on the arm to which the kite is attached, this makes it difficult to manually steer the kite and to manually control the angle of incidence of the kite to the wind.

The present invention seeks to provide an improved control arrangement for a wind powered vehicle while also minimising or eliminating heeling.

According to the present invention, there is provided a control arrangement for a wind powered vehicle, the arrangement comprising: a first elongate support member, a second elongate support member which is pivotally mounted at a pivot point to the first support member, the second support member having a free end which is remote from the pivot point, a flexible elongate drive line which is attachable at one end to a wind powered drive element which, in use, applies a drive force to the drive line, wherein the drive line extends slideably through a first mounting point adjacent the free end of the second support member such that the drive force applies a first moment to the second support member about the pivot point, a biasing arrangement configured to convert the drive force into a biasing force and to apply the biasing force to the second support member at a point between the free end and the pivot point, the biasing force applying a second moment to the second support member which at least partly cancels the first moment to reduce the overall moment to the second support member in a first plane, and a base unit which is rotatably attached to the first support member, the first support member being rotatable by any number of 360° rotations or part rotations relative to the base unit and configured to rotate relative to the base unit until the second support member aligns with the drive force and no overall moment is applied in a second plane to the second support member.

Preferably, the biasing arrangement comprises a second mounting point which is provided on the second support member between the free end and the pivot point, the biasing arrangement further comprising a fixing point provided on the first support member, the drive line extending slideably through the second mounting point and being fixed to the first support member at the fixing point.

Conveniently, the drive line extends a plurality of times between the second mounting point and the fixing point.

In one embodiment, the second mounting point is positioned substantially half way between the free end and the pivot point.

Preferably, the drive line extends twice between the second mounting point and the fixing point.

In another embodiment, the second mounting point is positioned on the second support member at substantially one third of the distance between the free end and the pivot point.

Advantageously, the drive line extends three times between the second mounting point and the fixing point.

Preferably, the position of the second mounting point on the second support member between the free end and the pivot point is adjustable by a modification value which is proportional to the frictional resistance between the drive line and at least one of the mounting points.

Conveniently, the position of the fixing point on the first support member is adjustable by a modification value which is proportional to the frictional resistance between the drive line and at least one of the mounting points.

Advantageously, the arrangement further comprises a resilient element which is attached to the first and second support members, the resilient element providing a resilient bias between the first and second support members to at least partly cancel a moment applied to the second support member by the weight of the second support member.

Conveniently, the resilient element is attached to at least one extension element which is attached to one of the first and second support members.

Preferably, the drive line extends at least partly around a rotatable element which is provided at the pivot point.

Conveniently, the arrangement further comprises two flexible elongate control lines which are attachable at one end to the wind powered drive element to control the wind powered drive element.

Advantageously, the control lines extend at least partly around the rotatable element.

Preferably, the control lines and the drive lines wind onto or reel out from the rotatable element as the rotatable element rotates.

Conveniently, the base unit incorporates an aperture and the elongate axis of the first support member is at least partly aligned with the aperture in the base unit.

Advantageously, the control lines extend through the aperture in the base unit.

In one embodiment, the arrangement further comprises two crew lines which are connected respectively to the two control lines, the crew lines extending through the aperture in the base unit.

Conveniently, the control lines or the crew lines are configured to be pulled in or let out manually by a user.

In one embodiment, the control lines or the crew lines are connected to a power bar which is operable to be controlled by the hands of a user.

In another embodiment, the control lines or the crew lines are attached to a foot bar which is operable to be controlled by the user's feet.

In a further embodiment, the control lines or the crew lines are connected to a mechanical control arrangement.

Preferably, the first support member is rotatable relative to the base unit about an axis aligned with a z direction, and wherein the base unit minimises or prevents movement of the first support member relative to the base unit in x, y and z directions, the x and y directions being perpendicular to one another and perpendicular to the z direction.

Conveniently, the base unit minimises or prevents rotation of the first support member relative to the base unit about axes aligned with the x and y directions.

In one embodiment, the base unit is releasably attached to the first support member.

Advantageously, the fixing point is moveable to adjust a heeling moment applied by the control arrangement to the vehicle.

In one embodiment, the arrangement further comprises an arrangement for adjusting the position of the fixing point automatically to stabilise the vehicle if the vehicle is subjected to a rolling moment.

Preferably, each of the lines is releasably attached to a releasable attachment element and wherein the length of the lines is adjustable by winding in or letting out the lines from the releasable attachment element.

Conveniently, the releasable attachment element is a rotatable drum which is operable to rotate to wind in or let out the lines.

Advantageously, the arrangement further comprises a wind powered element which is connected to one end of each line.

Preferably, the wind powered element comprises an aerofoil section.

In one embodiment, the wind powered element is a kite.

In another embodiment, the wind powered element is a wing.

Preferably, the wing is collapsible.

Conveniently, the wind powered element incorporates a float arrangement which floats on water.

Advantageously, the base unit is mounted to a boat.

Preferably, the boat comprises a keel, centreboard or a single element comprising both a keel/centreboard and rudder to resist lateral movement of the boat.

Conveniently, the longitudinal axis of the first support member is aligned with the longitudinal axis of the keel or centreboard.

Advantageously, the length of the second support member is selected so that the direction of the force exerted by the wind powered element on the drive line extends substantially through the centre of lateral resistance of the combined hull, keel or centreboard, rudder and other appendages when there is no overall moment applied to the second support member in the first or second planes.

In a still further embodiment, the base unit is configured to be attached to a boat.

In one embodiment, the base unit is attached directly to a keel or centreboard which is configured to be attached to a boat.

In another embodiment, the base unit is attached directly to a rudder which is configured to be mounted to a boat.

In a further embodiment, the rudder is mounted to a boat which does not incorporate a keel or centreboard.

Preferably, the rudder is pivotally mounted to or near the rear of a boat.

In one embodiment, the boat is a kayak.

In another embodiment, the boat is a dinghy.

In a further embodiment, the boat is a yacht.

In a still further embodiment, the boat is a boat selected from a group consisting of a raft, surfboard, ship, canoe, monohull, multihull, displacement vessel, planing vessel or a vessel supported on hydrofoils.

In one embodiment, the control arrangement is mounted to a planing vessel at or near the rear of the planing vessel.

In another embodiment, the boat comprises at least one hydrofoil element.

Preferably, each hydrofoil element is moveably mounted to the boat and the control arrangement further comprises an adjustment arrangement which is operable, in use, to adjust the angle of incidence of each hydrofoil element relative to water on which the boat is travelling to maintain each hydrofoil at a substantially constant depth below the surface of the water.

In one embodiment, the base unit is mounted to a land based wind powered vehicle.

In a further embodiment, the base unit is mounted to a snow or ice based wind powered vehicle.

DESCRIPTION OF THE DRAWINGS

In order that the invention may be more readily understood, and so that further features thereof may be appreciated, embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which:

FIG. 1 is a schematic diagram showing a control arrangement of one embodiment of the invention mounted to a boat,

FIG. 2 is a view corresponding to FIG. 1 showing the control arrangement tracking a kite as the kite moves up and down,

FIG. 3 is a plan view of the embodiment shown in FIG. 1 with the control arrangement tracking a kite as the kite rotates about a vertical axis,

FIG. 4 is a schematic diagram showing the control arrangement of FIG. 1 for an embodiment of the invention in which portions of the drive lines and portions of the control lines are incorporated into the biasing arrangement,

FIG. 5 is a schematic diagram illustrating the geometric terminology adopted in the analysis of the control arrangement in an embodiment of the invention,

FIGS. 6 and 7 summarise how the moment applied to the arm 4 varies as the inclination of the kite lines varies,

FIG. 8 is a schematic diagram illustrating the force in the lines for the arrangement shown in FIG. 4, taking account of the resistance at the pulley blocks,

FIG. 9 illustrates the effect of the resistance at the pulley blocks on the arm raising moment,

FIG. 10 illustrates how the kite drive force F required to maintain the arm in equilibrium against the self weight of the arm varies with the inclination of the arm and the kite lines,

FIG. 11 illustrates the eccentricity of the kite drive force F from the centre of lateral resistance due to the self weight of the arm, and the consequential heeling moment applied to the boat,

FIG. 12 shows how a spring may be located below the arm, above the arm or behind the mast to mitigate the self weight moment of the arm,

FIG. 13 illustrates an arrangement in which a spring is located behind the mast to mitigate the self weight moment of the arm,

FIG. 14 illustrates the raising moment applied to the arm shown in FIG. 13 when the kite drive force F=0,

FIG. 15 illustrates how the spring shown in FIG. 13 affects the kite drive force F required to maintain the arm 4 in equilibrium, and the resulting heeling moment applied to the boat,

FIG. 16 is a schematic diagram of a further embodiment of the invention which incorporates a biasing arrangement with drive lines and control lines attached to a midpoint of a support arm,

FIG. 17 is a schematic diagram showing the control arrangement of FIG. 1 for an embodiment of the invention in which portions of the drive lines only are incorporated into the biasing arrangement, with the drive lines terminating at the foot of the mast,

FIG. 18 is a schematic diagram showing the control arrangement of FIG. 1 for an embodiment of the invention in which portions of the drive lines only are incorporated into the biasing arrangement, with the drive lines terminating at the third point of the boom,

FIG. 19 is a schematic diagram for an embodiment of the invention in which portions of the drive lines only are incorporated into the biasing arrangement, with the drive lines connected to a midpoint of the support arm and terminating at the foot of the mast,

FIG. 20 is a schematic diagram for an embodiment of the invention in which portions of the drive lines only are incorporated into the biasing arrangement, with the drive lines connected to a midpoint of the support arm and terminating at the mid point of the support arm,

FIG. 21 is a schematic diagram of the control arrangement shown in FIG. 19,

FIG. 22 is a schematic perspective view of the control arrangement shown in FIG. 21,

FIG. 23 is a close-up schematic perspective view of part of the control arrangement shown in FIG. 22,

FIG. 24 is a schematic view showing the control arrangement of FIG. 23 attached to part of a vehicle,

FIGS. 25a-25d show diagrammatic sectional views of a first support member of an embodiment of the invention mounted rotatably to a base unit with the support member rotated at different angles,

FIG. 26 is a schematic diagram of a control arrangement for use with an embodiment of the invention to enable a user to control the arrangement using their feet and legs,

FIG. 27 is a diagrammatic view of a further control arrangement for use with an embodiment of the invention for a user to control the arrangement with their feet and legs,

FIG. 28 is a schematic diagram of a manual control arrangement for use with an embodiment of the invention,

FIG. 29 is a schematic diagram of a manual control arrangement using a power bar for use with an embodiment of the invention,

FIG. 30 is a schematic view of part of an embodiment of the invention illustrating an adjustable fixing point,

FIG. 31 is a schematic diagram showing a tuning line attached to the drive line of an embodiment of the invention,

FIG. 32 is a schematic diagram of a control arrangement for use with an embodiment of the invention which incorporates heel tuning,

FIG. 33 is a schematic diagram of part of an embodiment of the invention which incorporates a winding drum to wind in and let out the drive lines,

FIG. 34 is a schematic diagram of a collapsible wing attached to a control arrangement positioned on a boat,

FIG. 35 is a schematic diagram of the collapsible wing shown in FIG. 34,

FIG. 36 is a schematic perspective view of the collapsible wing shown in FIG. 34,

FIG. 37 is a schematic diagram of a float for use with a wind powered element of an embodiment of the invention,

FIGS. 38a-38c show the collapsible wing of FIG. 34 at different stages as the wing opens,

FIG. 39 is a schematic diagram showing the collapsible wing as it is ready to be launched from a boat.

FIG. 40 is a schematic diagram of a boat with a set of orthogonal axes: axis x which is aligned along the length of the boat 2, axis y which is aligned across the width of boat 2, and axis z which is normal to axes x and y,

FIG. 41 is a schematic diagram showing an analysis of a planing motor boat,

FIG. 42 is a schematic diagram showing an analysis of a planing boat using the control arrangement,

FIG. 43 refers to the arrangement shown in FIG. 42 and illustrates the relationship between the lift required from a the hydrofoil and the angle of inclination of the kite lines,

FIG. 44 refers to a boat without any hydrofoils using the control arrangement, the figure illustrates the relationship between the angle of inclination of the kite lines and the trim angle of the boat,

FIG. 45 illustrates how a pair of hydrofoils or a dihedral hydrofoil may be arranged to offset rolling of the boat,

FIG. 46 illustrates a boat with the control arrangement located forward of the centre of mass of the boat and two hydrofoils also located forward of the centre of mass of the boat,

FIG. 47 illustrates a boat with the control arrangement located at the stern of the boat and one hydrofoil located at the bow of the boat,

FIG. 48 illustrates a boat with control arrangement located forward of the centre of mass of the boat and the boat fully supported by hydrofoils at the bow and stern,

FIG. 49 illustrates a boat with control arrangement located at the stern of the boat and the boat fully supported by hydrofoils at the bow and stern,

FIG. 50 is a schematic diagram of a still further embodiment of the invention in which a control arrangement is attached to a centreboard which may be removably attached to a displacement boat such as a kayak,

FIGS. 51 to 54 show an embodiment of the control arrangement mounted on a boat which is designed to plane, the arrangement incorporates a quick release system to separate the control arrangement from the boat,

FIGS. 55 and 56 relate to the embodiment shown in FIGS. 51 to 54 and show details of the system for controlling the hydrofoil to maintain the hydrofoil at approximately constant depth below the water surface, and

FIG. 57 shows a base unit and a mounting bracket which are used to connect the control arrangement of an embodiment of the invention to the boat.

DETAILED DESCRIPTION

Automatic Tracking

Referring initially to FIG. 1 of the accompanying drawings, a control arrangement 1 is attached to a watercraft such as a boat 2. The operating principles of the control arrangement 1 will now be described before the control arrangement 1 is described in detail.

The control arrangement 1 incorporates a first support member in the form of a mast 3 and a second support member in the form of an arm 4. One end of the arm 4 is pivotally attached to the mast 3 at a pivot point 5. The lower end of the mast 3 is rotatably attached to a base unit (not shown).

In the arrangement shown in FIG. 1, the base unit is attached to the boat 2. In other embodiments, the base unit is configured to be removably attached to a boat or another vehicle by an attachment means, such as a push connector, bolt or clamping arrangement.

The control arrangement 1 is for use with a wind powered element which, in this embodiment, is a kite 6. The kite 6 is preferably a kite of the type typically used for kite surfing. In other embodiments, the control arrangement 1 is for use with another wind powered element, such as an aerofoil section. In further embodiments, the wind powered element is either a fixed wing or a collapsible wing.

The kite 6 is connected to the control arrangement 1 by at least one flexible elongate drive line which may also be known as a drive line. Embodiments of the invention may incorporate any number of drive lines. However, in this embodiment, there are two flexible elongate drive lines 7, 8. The drive lines 7, 8 are attached to the kite 6 and attached slideably to a free end 9 of the arm 4, for instance by a pulley. The drive lines 7, 8 transfer the majority of a drive force F exerted by wind on the kite 6 to the control arrangement 1.

In this embodiment, two flexible elongate control lines 10, 11 are attached at either end of the kite 6. In other embodiments there may be a greater or fewer number of control lines.

The control lines 10, 11 extend from the kite 6 to the free end 9 of the arm 4. The control lines 10, 11 are used to steer the kite 6 and to control the angle of incidence of the kite 6 to the wind. It is to be appreciated that the control lines 10, 11 are not loaded with a significant portion of the drive force F.

The control arrangement 1 incorporates a biasing arrangement 12 which applies a biasing moment to the arm 4 about the pivot point 5. The biasing arrangement 12 comprises portions of the drive lines 7, 8. In other embodiments the biasing arrangement 12 comprises portions of the drive lines 7, 8 and portions of the control lines 10,11. The configuration of the biasing arrangement 12 will be discussed in detail below.

In the arrangement shown in FIG. 1, the boat 2 is a yacht which incorporates a keel 13. The keel 13 provides a lateral resistance in the water which resists lateral movement of the boat through the water. The centre of lateral resistance 14 is defined notionally at the midpoint of the keel 13.

The effect of the control arrangement 1 of embodiments of the invention is to track the movement of the kite 6 so that a line of action 15 which is aligned with the drive force F exerted by the kite 6 on the control arrangement 1 passes through the centre of lateral resistance 14, as shown in FIG. 1.

Without any external control or energy input the control arrangement 1 automatically tracks the movement of the kite 6 in a first plane as the kite 6 moves up and down and ensures that the line of action 15 always passes through the centre of lateral resistance 14. This principle is illustrated in FIG. 2 with the kite 6 moving from a lower position to a higher position, with the line of action 15 always passing through the centre of lateral resistance 14.

The mast 3 is rotatably attached to the base unit to allow the mast 3 to rotate freely around the longitudinal axis of the mast 3 by any number of 360° rotations or part rotations. The control arrangement 1 can therefore rotate freely relative to the boat 2. This enables the control unit 1 to track the movement of the kite 6 in a second plane as the kite 6 rotates around the boat 2, as shown in FIG. 3.

The optimum plan orientation and vertical alignment of the control arrangement 1 to minimise or eliminate heeling is freely found as a natural outcome of the geometry and rotational releases of the control arrangement 1. The control arrangement 1 freely tracks the kite 6 vertically and on plan without any external control or energy input.

Biasing Arrangement

The control arrangement 1 of an embodiment of the invention will now be described in more detail with reference to FIG. 4. In this embodiment, the drive lines 7, 8 (only one of which is visible in FIG. 4) and the control lines 10, 11 (not shown in FIG. 4) extend slideably through a first mounting point 16 which is provided at or adjacent to the free end 9 of the arm 4. In other embodiments, the drive lines 7, 8 are joined together before reaching the arm 4 and a single drive line extends through the first mounting point 16.

The drive lines 7, 8 and the control lines 10, 11 extend slideably through a mounting point 18 provided on the arm 4 at a position substantially one third of the way along the length of the arm 4 between the pivot point 5 and the free end 9. In this embodiment, the drive lines 7, 8 and the control lines 10, 11 extend from the second mounting point 18 and extend slideably through a third mounting point 19 positioned at the base of the mast 3. The drive lines 7, 8 and the control lines 10, 11 extend from the third mounting point 19 back up to the arm 4 and extend slideably through a fourth mounting point 20 provided on the arm 4 at approximately the same location as the second mounting point 18. The drive lines 7, 8 and the control lines 10, 11 extend from the fourth mounting point 20 to a fixing point 21 at the base of the mast 3. In this embodiment, all of the mounting points are pulleys.

At each mounting point 16, 18, 19 and 20 a separate pulley is provided for the drive lines 7, 8 and for each of the control lines 10, 11. This allows the control lines to run through the pulleys independently of the drive lines.

It is to be appreciated that portions of the drive lines 7, 8, the control lines 10, 11 the second, third and fourth mounting points 18-20 and the fixing points 21 all constitute components of the biasing arrangement 12. In this embodiment, the drive lines 7, 8 and the control lines 10, 11 are looped three times between the mast 3 and the arm 4. The triple looping of the drive lines 7, 8 and the control lines 10, 11 is selected to match the one-third distance position of the second mounting point 18 along the length of the arm 4. The triple loop of the biasing arrangement 1 exerts a control force between the mast 3 and the arm 4 which is three times the drive force F.

The operation of the control arrangement 1 will now be described in more detail with reference to FIG. 5. The control arrangement 1 tracks the kite 6 automatically and the control arrangement 1 operates in an equilibrium state in which there is no overall moment applied to the arm 4 in a first plane or a second plane which is perpendicular to the first plane. The biasing arrangement 12 exerts a biasing force which is derived from the drive force F. The biasing control force applies a biasing moment to the arm 4 to cancel the moment applied to the arm 4 by the kite 6 in a first plane.

The moments applied to the arm 4 and the equilibrium state are calculated as follows with reference to FIG. 5:

i) The height of the mast 3 is selected so that A is located at the centre of lateral resistance 14.

ii) Triangle ACE and triangle BCD are similar triangles: AE is always parallel to BD.

iii) When the lines pass around the mounting points the drive lines 7, 8 and the control lines 10, 11 run round a notionally frictionless pulley block, therefore the axial load in the drive lines 7, 8 and the control lines 10, 11 remains constant.

iv) The pivot point 5 is located at C. The arm 4 is able to rotate in the vertical plane relative to the mast 3.

v) Positive value moments cause the arm to rise. Now, taking moments about C:

Moment applied to the arm, M_a:

$\begin{array}{cc}{M}_a=\mathrm{LF}\sin \left(\theta +\mu -\phi \right)-\frac{L}{N}\mathrm{NF}\sin \left(\theta -\phi \right)\frac{M_a}{\mathrm{LF}}=\sin \left(\theta +\mu -\phi \right)-\sin \left(\theta -\phi \right)& \left[\mathrm{equation}3\right]\end{array}$

If μ=0 then F is aligned along AE and the line of action 15 of the kite drive force F passes through A, the centre of lateral resistance 14. The moment applied to the arm 4 is:

M _a =LF{sin(θ+0−φ)−sin(θ−φ)}=0

This zero moment means that the arm 4 is in equilibrium. The arm 4 will remain in this position and the line of action 15 of the kite 6 will continue to pass through the centre of lateral resistance 14 until the kite 6 is flown to a different position.

If the kite 6 is flown higher or lower then μ≠0. Since (θ+μ−Φ)≠(θ−Φ), then sin(θ+μ−Φ)≠ sin(θ−Φ) and so M_a #0. The arm 4 therefore rises or falls, causing θ to increase or decrease and μ to vary. FIGS. 6 and 7 show how the moment applied to the arm 4 varies with μ. In summary:

If the kite 6 is flown lower then μ<0. Since (θ+μ−Φ)<(θ−Φ), then sin(θ+μ−Φ)<sin(θ−Φ) and so M_a<0. The arm 4 therefore falls, causing θ to decrease and μ to increase until μ=0 and M=0. Equilibrium is regained.

If the kite 6 is flown higher and 0<μ<π−2(θ−φ) then M_a>0. The arm 4 therefore rises, causing θ to increase and μ to decrease until μ=0 and M_a=0. Equilibrium is once again regained.

If the kite 6 is flown so high that μ>π−2(θ−φ) then M_a<0. The arm 4 therefore falls, causing θ to decrease and μ to increase which results in a further decrease in M_a. This is an unstable state in which the arm 4 continues to lower, the state should therefore be avoided. Referring to FIG. 5 it is seen that:

$\begin{array}{cc}\tan \theta =\frac{H+L\sin \phi }{L\cos \phi }\tan \theta =\frac{H}{L\cos \phi }+\tan \phi & \left[\mathrm{equation}4\right]\end{array}$

To avoid the unstable condition in which μ>π−2(θ−φ):

$\begin{array}{cc}\mu <\pi +2\phi -2{\tan }^{-1}\left[\frac{H}{L\cos \phi }+\tan \phi \right]\frac{H}{L}<\cos \mathrm{\phi tan}\left[\frac{\pi +2\phi -\mu }{2}\right]-\sin \phi & \left[\mathrm{equation}5\right]\end{array}$

For practical situations this relationship is generally satisfied if H/L≦0.8 and the unstable condition in which μ>π−2(θ−φ) is thus avoided.

The discussion above neglects resistance on the lines running round pulley blocks, the resistance of bearings at the pivot point 5, and the self weight of the arm 4. The effect of resistance at the pulley blocks and bearings, and the effect of self weight are discussed below.

Where a line passes round a pulley block friction causes a change in the axial force in the line so that the ratio of the line force before and after passing round the pulley block is (1+χ).

FIG. 8 illustrates the values of the force in the lines for the arrangement shown in FIG. 4, taking account of the resistance at the pulley blocks. The position D at which the biasing arrangement 12 is connected to the arm 4 is adjusted by a modification factor λ so that D is a distance L/{N (1+λ)} from the pivot point 5. The position B at which the biasing arrangement 12 is connected to the mast 3 is similarly adjusted so that B is a distance H/{N (1+λ)} from the pivot point 5, this maintains triangle BCD and triangle ACE as similar triangles.

The total force in the lines between points B and D is:

T _BD=(1+α)NF  [equation 6]

The value of a varies with the arrangement of the lines and pulley blocks, the type of line, the diameter of the line, the type and diameter of pulley (roller bearing, plain sheave etc.) and the age and wear of the pulley blocks. The variation in T_BD due to resistance at the pulley blocks reduces the arm raising moment M_a. FIG. 9 illustrates the effect of the variation in T_BD on the arm raising moment M_a when λ=0. In the case illustrated the resistance at the pulley blocks prevents the arm from raising for some values of φ.

Referring again to FIG. 8, in addition to the variation in T_BD the figure also indicates the moment M_b due to resistance at the bearing at pivot 5.

Continuing to neglect self weight of the arm 4, the net raising moment on arm 4 is:

$\begin{array}{cc}{M}_a=\mathrm{LF}\sin \left(\theta +\mu -\phi \right)-\frac{L}{N\left(1+\lambda \right)}\left\{\mathrm{NF}\left(1+\alpha \right)\right\}\sin \left(\theta -\phi \right)-M_b& \left[\mathrm{equation}7\right]\end{array}$

If suitable bearings are used at pivot point 5 M_b is small and resistance due to the bearing at pivot 5 may be neglected in which case, if

$\begin{array}{cc}1+\lambda =1+\alpha \mathrm{then}\text{:}\frac{M_a}{\mathrm{LF}}\approx \sin \left(\theta +\mu -\phi \right)-\sin \left(\theta -\phi \right)& \left[\mathrm{equation}8\right]\end{array}$

In conclusion, by moving the point D along the arm so that D is a distance L/{N(1+α)} from the pivot 5 the reduction in the arm raising moment M_a due to the resistance at the pulley blocks can be effectively eliminated. If suitable bearings are used at the pivot point 5 then M_b is small and may be neglected, in which case equation 7 reduces to equation 3.

The position of the mounting points at D may be adjustable so that the mounting points can be moved along the arm to allow for λ as pulley blocks and lines wear or are replaced causing α to vary. If the position of the mounting points at D are adjusted without also adjusting mounting points at B triangle BCD and triangle ACE are no longer similar and the line of action 15 of the kite drive force F does not pass directly through the centre of lateral resistance 14. The position of the mounting points at B may also be adjustable so that triangles BCD and ACE may be maintained as similar triangles, or a small misalignment of the line of action 15 of the kite drive force F from the centre of lateral resistance 14 may be accepted; in this case the small consequential rolling moment will result in a slight heel of the boat 2.

Now considering the effect of the self weight of arm 4 on the arm raising moment M_a. Modifying equation 3 to include the self weight moment:

$\begin{array}{cc}\frac{M_a}{\mathrm{LF}}=\sin \left(\theta +\mu -\phi \right)-\sin \left(\theta -\phi \right)-\frac{\mathrm{mgr}\cos \phi }{\mathrm{LF}}& \left[\mathrm{equation}9\right]\end{array}$

where

• • m is the mass of the arm 4
  • g is the acceleration due to gravity
  • r is the distance from the pivot point 5 to the centre of mass of the arm 4For equilibrium of the arm M_a=0:

$\begin{array}{cc}F=\frac{\mathrm{mgr}\cos \phi }{L\left\{\sin \left(\theta +\mu -\phi \right)-\sin \left(\theta -\phi \right)\right\}}& \left[\mathrm{equation}10\right]\end{array}$

FIG. 10 illustrates how the kite drive force F required to maintain the arm in equilibrium varies with φ and μ. FIG. 11 illustrates the corresponding eccentricity of the kite drive force F from the centre of lateral resistance 14, and the consequential heeling moment M_b applied to the boat 2.

If a lightweight construction is adopted for the arm 4 for most combinations of φ and μ the heeling moment is small, however it may be desirable to reduce it further. In light wind the kite drive force F is insufficient to raise the arm 4.

A resilient element in the form of a spring 80 can be added to control arrangement 1 to offset the self weight moment of the arm. If desired the spring can be arranged so that when the arm 4 is low a small arm raising moment is applied, and when the arm 4 is high a small arm lowering moment is applied. This results in an at rest angle φ_eq which the arm 4 will adopt when no load is applied. It may be advantageous for the arm 4 to adopt a specified at rest angle so that the arm is kept clear of the sea, deck and adjacent pontoons when the kite is not in use.

FIG. 12 shows how such a spring 80 may be located below arm 4, above arm 4, or behind the mast 3. FIG. 13 illustrates an arrangement in which the spring 80 is located behind the mast 3. The raising moment M_s applied to the arm 4 by a spring 80 located behind the mast 3 is:

M _s =S(p+c)sin ω+S(b−q)cos ω  [equation 11]

where:

• • p=a cos φ−e sin φ−c
  • q=b−a sin φ−e cos φ
  • d=(p²+q²)^0.5
  • S=(d−d_s)k+S₀
  • k=spring stiffness
  • d_s=value of d when the spring is first loaded
  • S₀=the maximum spring load at zero extension

The force required to maintain the arm 4 in equilibrium is:

$\begin{array}{cc}F=\frac{\mathrm{mgr}\cos \phi -M_s}{L\left\{\sin \left(\theta +\mu -\phi \right)-\sin \left(\theta -\phi \right)\right\}}& \left[\mathrm{equation}11\right]\end{array}$

This is a development of the principles for a spring balanced cantilever. FIG. 14 illustrates the raising moment M_s applied to the arm 4 by the spring 80, the self weight moment on the arm 4, and the net raising moment M_a applied to the arm 4 when the kite drive force F=0.

FIG. 15 illustrates how the spring 80 affects the kite drive force F required to maintain the arm 4 in equilibrium, and the resulting heeling moment M_h applied to the boat 2.

When c=0, e=0, d₀=0 and S₀=0 equation 11 reduces so that:

M _s =kab cos φ  [equation 13]

The raising moment on the arm 4 due to the action of the spring 80 and the self weight of the arm 4 is:

M _a =kab cos φ−mgr cos φ  [equation 14]

If k=mgr/ab then M_a=0 for all φ and the arm 4 is a spring balanced cantilever in equilibrium at all values of φ when no kite drive force F is applied. In this case if the arm is in equilibrium the line of action 15 of the kite drive force F passes through the centre of a lateral resistance 14 for all values of φ and so no heeling moment is applied to the boat.

As an alternative to a spring 80, a counterweight may be used to offset the self weight moment of the arm 4. However a counterweighted system is generally undesirable since a counterweight introduces additional mass at high level which reduces the stability of the boat 2, the counterweight also increases the moment of inertia of the arm 4 which slows the response of the arm 4 in tracking the kite 6 as the kite 6 is flown higher or lower.

The theory described above illustrates how the control arrangement 1 operates to maintain the arm 4 in equilibrium in a first plane as the kite 6 moves up and down. The biasing arrangement 12 biases the mast 3 so that the line of action 15 always passes through the centre of lateral resistance 14 as the kite 6 moves up and down in the first plane.

The mast 3 is free to rotate about the base unit which allows the control unit 1 to track the kite 6 as the kite 6 moves on plan relative to the boat 2. The control arrangement 1 tracks the movement of the kite 6 freely in the first and second planes without any external control or energy input. The control arrangement 1 therefore tracks the kite 6 automatically and maintains the arm 4 in equilibrium with the line of action 15 always extending through the centre of lateral resistance 14.

Since the control arrangement 1 ensures that the line of action 15 always aligns with and passes through the centre of lateral resistance 14, the kite 6 pulls the boat 2 forward without applying a heeling moment to the boat. Since there is no heeling moment applied to the boat, by comparison with a traditional sailing boat a narrower hull can be used and the ballast in the boat can be significantly reduced or omitted altogether. Nevertheless, some ballast may still be required for other reasons, for instance to make a boat self-righting from capsize.

The narrow hull and the reduction or total omission of ballast makes it possible to increase the length displacement ratio of a boat above 5.7. This allows the boat to travel at speeds corresponding to a Froude number greater than 0.45. A boat powered by a kite attached to the control arrangement 1 can therefore travel at much higher speeds than an equivalent boat using a sail.

An embodiment of the present invention minimises or eliminates the heeling moment for a wind powered vehicle and therefore allows a narrower hull with less ballast to be used. When an embodiment of the invention is applied to a yacht this allows a length displacement ratio of greater than 5.7 to be achieved and the yacht is therefore able to exceed a speed of Fr=0.45.

An additional benefit is derived from the vertical pull that the kite 6 exerts on the boat 2. The vertical pull exerts an upward lifting component on the boat 2 which further reduces the displacement of the hull in the water. This increases the length displacement ratio and enables the boat to travel faster in the water.

The reduction in the heel of the boat by the control arrangement 1 minimises or eliminates the losses associated with travel in the water while heeling. The forward force on the boat 2 from the kite 6 is therefore maximised which further maximises the speed of travel in the water.

Further benefits derived from a narrow hull include minimising pitching due to waves and minimising the slamming impact of the water on the hull at speed. This makes travelling in the boat more comfortable.

A narrow hull allows a high angle of vanishing stability and a small or zero negative area on the static stability curve. This improves the sea worthiness of the hull and improves safety.

A narrow hull also results in less roll due to waves which makes the boat more sea-worthy and comfortable. Less damping is required which results in less resistance and an increase in the speed of the boat.

The automatic tracking to achieve automatic equilibrium of the control arrangement 1 allows a very large kite to be fitted to a boat. The maximum size of the kite is limited by:

i) The general requirement to avoid lifting the boat bodily out of the water.

ii) If the control arrangement is located towards the stern of the boat the maximum kite size is limited by the requirement to avoid causing the boat to “pitchpole” when a boat is thrown stern over bows into an inverted position.

Despite these constraints, a much larger kite area can be used than the maximum sail area for a sailing boat of equivalent size. This contributes to enabling the boat to achieve a significantly greater speed than a sailing boat of equivalent size.

Embodiments of the invention allow a boat to achieve a speed which is significantly higher than the maximum speed of a typical sailing boat of equivalent size.

Referring now to FIG. 16 of the accompanying drawings, a control arrangement 1 of a further embodiment of the invention incorporates the same mast 3 and arm 4 as the embodiment described above. However, in this further embodiment, the biasing arrangement 12 is formed by the drive lines 7, 8 and the control lines 10, 11 which extend between a third mounting point 19, a fourth mounting point 18 and a fixed point 21, with the third mounting point 19 and the fixed point 21 are at the base of the mast and the fourth mounting point 18 is positioned substantially halfway along the length of the arm 4 between the pivot point 5 and the free end 9.

In this embodiment, the drive lines 7, 8 (only one of which is visible in FIG. 16) and the control lines 10, 11 (not shown in FIG. 16) extend slideably through a first mounting point 16 which is provided at or adjacent to the free end 9 of the arm 4. In other embodiments, the drive lines 7, 8 are joined together before reaching the arm 4 and a single drive line extends through the first mounting point 16.

The drive lines 7, 8 and the control lines 10, 11 extend slideably through a second mounting point 20 adjacent to the pivot 5. The drive lines 7, 8 and the control lines 10,11 extend downwardly from the second mounting point 20 to extend slideably through a third mounting point 19 positioned at the base of the mast 3 before extending to the fourth mounting point 18 positioned halfway along the length of the arm 4. The drive lines 7, 8 and the control lines 10, 11 extend slideably through the fourth mounting point 18 then double back from the fourth mounting point 18 to the fixing point 21 at the base of the mast 3.

In this further embodiment, the biasing arrangement 12 incorporates two loops of the drive lines 7, 8 and the control lines 10, 11 in order to match the midpoint mounting of the mounting point 18. This is in contrast with the embodiment described above where there are three loops of the drive lines 7, 8 and the control lines 10, 11 in the biasing arrangement 12 to match the one-third mounting point position of the mounting point 18. It is, however, to be appreciated that the control arrangement 1 operates in the same manner as the control arrangement 1 of the embodiments described above. The biasing arrangement 12 still biases the arm 4 to achieve equilibrium.

In this embodiment at each mounting point 16, 18, 19, and 20 a separate pulley is provided for the drive lines 7, 8 and for each of the control lines 10, 11. This allows the control lines to run through the pulleys independently of the drive lines.

The control arrangement 1 of a further embodiment of the invention will now be described in more detail with reference to FIG. 17. In this embodiment, the drive lines 7, 8 (only one of which is visible in FIG. 17) extend slideably through a first mounting point 16 which is provided at or adjacent to the free end 9 of the arm 4. In other embodiments, the drive lines 7, 8 are joined together before reaching the arm 4 and a single drive line extends through the first mounting point 16.

The drive lines 7, 8 extend along the length of the arm 4 and around a rotatable element 17 which is provided at the pivot point 5. The rotatable element 17 is rotatably attached to either the arm 4 or the mast 3 or to the pivotal connection between the arm 4 and the mast 3. The drive lines 7, 8 are at least partly wound around the rotatable element 17. Friction between the rotatable element 17 and the drive lines 7, 8 ensures that the rotatable element 17 rotates as the drive lines 7, 8 move relative to the arm 4.

The drive lines 7, 8 extend around the rotatable element 17 and extend slideably through a second mounting point 18 provided on the arm 4 at a position substantially one-third of the way along the length of the arm 4 between the pivot point 5 and the free end 9. In this embodiment, the drive lines 7, 8 extend from the second mounting point 18 and extend slideably through a third mounting point 19 positioned at the base of the mast 3. The drive lines 7, 8 extend from the third mounting point 19 back up to the arm 4 and extend slideably through a fourth mounting point 20 provided on the arm 4 at approximately the same location as the second mounting point 18. The drive lines 7, 8 extend from the fourth mounting point 20 to a fixing point 21 at the base of the mast 3. In this embodiment, all of the mounting points are pulleys.

It is to be appreciated that portions of the drive lines 7, 8, the second, third and fourth mounting points 18-20 and the fixing points 21 all constitute components of the biasing arrangement 12. In this embodiment, the drive lines 7, 8 are looped three times between the mast 3 and the arm 4. The triple looping of the drive lines 7, 8 is selected to match the one-third distance position of the second mounting point 18 along the length of the arm 4. The triple loop of the biasing arrangement 1 exerts a control force between the mast 3 and the arm 4 which is three times the drive force F.

The control arrangement 1 of a further embodiment of the invention will now be described in more detail with reference to FIG. 18. In this embodiment, the drive lines 7, 8 (only one of which is visible in FIG. 18) extend slideably through a first mounting point 16 which is provided at or adjacent to the free end 9 of the arm 4. In other embodiments, the drive lines 7, 8 are joined together before reaching the arm 4 and a single drive line extends through the first mounting point 16.

The drive lines 7, 8 extend along the length of the arm 4 and around a rotatable element 17 which is provided at the pivot point 5. The rotatable element 17 is rotatably attached to either the arm 4 or the mast 3 or to the pivotal connection between the arm 4 and the mast 3. The drive lines 7, 8 are at least partly wound around the rotatable element 17. Friction between the rotatable element 17 and the drive lines 7, 8 ensures that the rotatable element 17 rotates as the drive lines 7, 8 move relative to the arm 4.

The drive lines 7, 8 extend around the rotatable element 17 and extend downwardly from the rotatable element 17. The drive lines 7,8 extend slideably through the second mounting point 22 at the base of the mast 3 before extending to the third mounting point 18 positioned substantially one third of the way along the length of the arm 4. The drive lines 7, 8 extend slidably through the third mounting point 18 before doubling back from the third mounting point 18 to a fourth mounting point 21 at the base of the mast 3. The drive lines extend slidably through the fourth mounting point 21 then return to the fixing point 20 adjacent to mounting point 18 on the arm 4. In this embodiment, all of the mounting points are pulleys.

It is to be appreciated that portions of the drive lines 7, 8, the second, third and fourth mounting points 18, 21, 22 and the fixing points 20 all constitute components of the biasing arrangement 12. In this embodiment, the drive lines 7, 8 are looped three times between the mast 3 and the arm 4. The triple looping of the drive lines 7, 8 is selected to match the one-third distance position of the second mounting point 18 along the length of the arm 4. The triple loop of the biasing arrangement 1 exerts a control force between the mast 3 and the arm 4 which is three times the drive force F.

Referring now to FIG. 19 of the accompanying drawings, a control arrangement 1 of a further embodiment of the invention incorporates the same mast 3 and arm 4 as the embodiment described above. However, in this further embodiment, the biasing arrangement 12 is formed by the drive lines 7, 8 which extend between a second mounting point 19, a third mounting point 18 and a fixed point 21, with the second mounting point 19 and the fixing point 21 located at the base of the mast and the third mounting point 18 positioned substantially halfway along the length of the arm 4 between the free end 9 and the pivot point 5.

In this further embodiment, the drive lines 7, 8 extend downwardly from the rotatable element 17 to a mounting point 19 positioned at the base of the mast 3 the drive lines 7, 8 extend slideably past the second mounting point 19 before extending to the third mounting point 18 positioned substantially halfway along the length of the arm 4. The drive lines 7, 8 extend slidably through the third mounting point 18 then double back to the fixing point 21 at the base of the mast 3.

In this further embodiment, the biasing arrangement 12 incorporates two loops of the drive lines 7, 8 in order to match the midpoint mounting of the mounting point 18. This is in contrast with the embodiment described above where there are three loops of the drive lines 7, 8 in the biasing arrangement 12 to match the one-third mounting point position of the mounting point 18. It is, however, to be appreciated that the control arrangement 1 operates in the same manner as the control arrangement 1 of the embodiments described above. The biasing arrangement 12 still biases the arm 4 to achieve equilibrium.

Referring now to FIG. 20 of the accompanying drawings, a control arrangement 1 of a further embodiment of the invention incorporates the same mast 3 and arm 4 as the embodiment described above. However, in this further embodiment, the biasing arrangement 12 is formed by the drive lines 7, 8 which extend between a second mounting point 18 positioned substantially halfway along the length of the arm 4 between the free end 9 and the pivot point 5, a third mounting point 19 positioned at the base of the mast and a fixed point 20 adjacent to the second mounting point 18.

In this further embodiment, the drive lines 7, 8 extend from the rotatable element 17 along the arm 4 to extend slideably through the second mounting point 18 before extending to extend slideably through the third mounting point 19. The drive lines 7, 8 double back from the third mounting point 19 to the fixing point 20 substantially halfway along the arm 4.

In this further embodiment, the biasing arrangement 12 incorporates two loops of the drive lines 7, 8 in order to match the midpoint mounting of the second mounting point 18. It is to be appreciated that the control arrangement 1 operates in the same manner as the control arrangement 1 of the embodiments described above. The biasing arrangement 12 still biases the arm 4 to achieve equilibrium.

In other embodiments of the invention the biasing arrangement 12 is configured with a different position ratio to the one-third and one-half ratios described above. For instance, in one embodiment, the second mounting point 18 is positioned substantially one-fifth of the way along the arm 4 and the drive lines 7, 8 are looped five times between the fixing point 21 and the arm 4. The biasing arrangement 12 may be organised so that the lines terminate at the foot of the mast or at the boom. Embodiments are possible for any case wherein the second mounting point is positioned on the second support member at substantially L/{N(1−λ)} of the distance between the free end and the pivot point, where L is the length of the second support member, N is a positive integer, and λ, is a modification factor to allow for resistance where lines pass round pulley blocks.

Referring again to FIG. 13 which shows an embodiment of the invention in which a spring 80 is provided to assist in balancing the self weight of the arm 4. Bracket 78 is connected to mounting point 77 at the base of the mast 3 on the opposite side of the mast from the arm 4. Spring 80 is connected to end 79 of bracket 78. Line 81 is connected to the free end of spring 80. Bracket 82 is connected to the mast 3 on the opposite side from the arm 4. Bracket 82 supports mounting points 84 and 83 which are above pivot point 5. Mounting point 84 is on the opposite side of the mast from the arm 4, mounting point 83 is on the same side of the mast as the arm 4.

Line 81 extends from the free end of spring 80 to mounting point 84. Line 81 extends slideably past mounting point 84 towards mounting point 83. Line 81 extends slideably past mounting point 83 towards mounting point 85. Line 81 is fixed to mounting point 85 which is on the end of bracket 86 which is connected to arm 4 at mounting point 87. Mounting point 83 is distance b above the pivot point 5, and distance c forward of pivot point 5. Mounting point 87 is distance a along arm 4 from pivot point 5. Mounting point 85 is distance e from mounting point 87 in a direction perpendicular to and above arm 4. The distance between mounting points 83 and 85 is d at an inclination ω below horizontal, the horizontal distance between mounting points 83 and 85 is p, the vertical distance between mounting points 83 and 85 is q.

The arm 4 has a mass m which is taken to act at the centre of gravity of the arm 4 which is a distance r from pivot point 5 along arm 4. The control arrangement 1 is otherwise as illustrated in FIG. 4 and described above. As the arm 4 lowers the spring 80 extends, this causes a tensile load in line 81 which results in a raising moment on arm 4.

Kite Control

Referring now to FIGS. 21 to 24 of the accompanying drawings, the control lines 10, 11 extend slideably through the first mounting point 16 at the free end 9 of the arm 4 and along the length of the arm 4 to the rotatable element 17. The control lines 10, 11 are wound around respective ends of the rotatable element 17. In use, as the drive lines 7, 8 rotate the rotatable element 17 as the arm 4 moves up and down, the control lines 10, 11 extend and shorten by the same amount as the drive lines 7, 8 since the control lines 10, 11 are wound around the same rotatable element 17. The load in the control lines 10, 11 terminates on the rotatable element 17. The load in the control lines is delivered into the rotatable element 17 and from the rotatable element 17 by friction into the drive lines 7, 8 which are wound at least partly around the rotatable element 17.

After leaving the rotatable element 17, each control line 10, 11 is slideably connected respectively to the end of a flexible elongate crew line 23, 24. The crew lines 23, 24 can be pulled in or eased out by a user to vary the length of the control lines 10, 11 to control the kite 6.

The crew lines 23, 24 extend slideably through apertures 25, 26 provided in a lower section of the mast 3. The lower section of the mast 3 is rotatably mounted in a base unit 27. The crew lines 23, 24 pass through an aperture 28 in the base unit 27 to a crew member who may be positioned in a cockpit of the boat which is remote from the control arrangement 1.

The crew lines 23, 24 extend out from the base of the control unit 1 in substantial alignment with the longitudinal axis of the mast 3. This ensures that the crew lines 23, 24 are kept close to one another which allows the crew lines 23, 24 to be uncrossed easily if the control arrangement 1 rotates such that the crew lines become crossed.

When the kite 6 is dead ahead of the boat 2, the crew lines 23, 24 are untwisted, as shown in FIG. 25a. When the kite 6 moves to 60° off the bow of the boat 2, the control lines 23, 24 rotate with the mast 3 but remain untwisted, as shown in FIG. 25b. If the kite 6 moves to 130° off the bow of the boat 2 and no action is taken regarding the control lines 23, 24 then the control lines 23, 24 cross with one another as shown in FIG. 25c. In order to undo this twisting of the control lines 23, 24 a user uncrosses the control lines 23, 24, for instance by swapping the control lines 23, 24 between each hand. This uncrosses the control lines 23, 24 as shown in FIG. 25d.

In a further embodiment, the control arrangement is as described above but with the control lines 10, 11 taking the place of the crew lines 23, 24. After passing through the biasing arrangement 12, the control lines 10, 11 extend slideably through the mounting point at the base of the mast and extend slideably through apertures 25, 26 provided in a lower section of the mast 3.

Referring now to FIG. 26 of the accompanying drawings, a steering control arrangement 29 is connected to the crew lines 23, 24. In this embodiment, the steering control arrangement 29 incorporates a foot bar 30. The crew lines 23, 24 are connected to respective ends of the foot bar 30 after looping around pulleys 31, 32 which are fixed to the boat. The foot bar 30 incorporates a central aperture in an enlarged portion 33 through which the crew lines 23, 24 extend. A crew member 34 steers the kite 6 by moving the foot bar 30 with their feet. The foot bar 30 pulls the crew lines 23, 24 as it is pushed at each end by the feet of the crew member 34. The foot bar 30 is configured to rotate about the longitudinal length of the crew lines 23, 24 as shown by arrows 35 so that the crew member 34 can uncross the crew lines 23, 24.

Referring now to FIG. 27 of the accompanying drawings, in a further embodiment of the invention a foot bar 36 is attached to the crew lines 23, 24 so that a crew member 34 can control the crew lines 23, 24 with their feet. However, in this embodiment an anchor line 37 is attached to the centre of the foot bar 36 and to a mounting point 38 provided on the boat. In this embodiment, the anchor line 37 takes up the majority of the load in the crew lines 23, 24 so that the crew member 34 only has to exert a minimal effort on the foot bar 36 in order to steer the kite 6. In this embodiment the angle of incidence of the kite 6 to the wind is controlled by drawing the anchor line 37 through the cleat 38.

Referring to FIG. 28 of the accompanying drawings, the crew lines 23, 24 extend in one embodiment of the invention from a control arrangement 1 mounted at the stern of a boat. The crew lines 23, 24 loop around respective pulleys 53, 54. The pulleys 53, 54 are mounted on elongate swivel bar 56, as shown in FIG. 28. The swivel bar 56 is pivotally mounted to the boat to pivot about a central pivot point 57. In use, an occupant 55 of the boat holds one crew line 23, 24 in each hand and controls the kite 6 by pulling and releasing each crew line 23, 24. The crew lines 23, 24 and the swivel bar 56 are configured to rotate about the longitudinal length of the crew lines 23, 24 as shown by arrows 35 so that the crew member 55 can uncross the crew lines 23, 24.

In a further embodiment of the invention, the crew lines 23, 24 are attached to an elongate power bar 56, as shown in FIG. 29. The power bar 56 is pivotally mounted to the boat to pivot about a central pivot point 57. In this embodiment, the pivot point 57 is an attachment to an adjustable tension line 58. The tension line 58 extends from the power bar 56, to pass slideably around one or more junction points 59, 60 to an adjustable cleat 61. In this embodiment, to adjust the angle of incidence of the kite to the wind the position of the power bar 56 may be altered by adjusting the attachment position of the tension line 58 on the cleat 61. In use, a user 55 holds further crew lines 62, 63 attached to each end of the power bar 56. In this embodiment, the length and orientation of the power bar 56 may be selected to increase or decrease the sensitivity of the steering arrangement. For instance, the length of the power bar 56 may be increased to enable a user 55 to steer the kite by only applying minimal movement to the further crew lines 62, 63. The crew lines 23, 24 and the power bar 56 and the further crew lines 62, 63 are configured to rotate about the longitudinal length of the crew lines 23, 24 as shown by arrows 35 so that the crew member 55 can uncross the crew lines 23, 24.

In a further embodiment, the power bar 56 is positioned to allow the user 55 to move the power bar 56 with their feet and legs. In this further embodiment, the user 55 can steer the kite using their feet and legs whilst keeping their hands free for other purposes. To adjust the angle of incidence of the kite to the wind the position of the foot operated power bar 56 can be adjusted by adjusting the length of the tension line 58.

In other embodiments, the arrangement does not incorporate a foot bar. In these arrangements, the crew lines 23, 24 may be pulled and released by a crew member holding onto the crew lines 23, 24. In further embodiments, the crew lines 23, 24 are connected to a hand bar which may be held by a crew member and moved to control the kite 6. The hand bar may be of a type usually used for kite surfing.

Where the control lines continue through the base of the mast, the control lines 10, 11 may be pulled and released by a crew member holding onto the control lines 10, 11. In further embodiments, the control lines 10, 11 are connected to a hand bar or a foot bar which may be moved by a crew member to control the kite 6. The hand bar may be of a type usually used for kite surfing.

For all the arrangements described above the crew lines 23, 24 or the control lines 10, 11 may be controlled by a mechanical, electronic or hydraulic system in place of the foot or hand arrangements described above. This will allow any mechanical, electronic or hydraulic system to be located in a location where safe and easy access is available for maintenance.

Mounting Control Arrangement 1 on a Vehicle

FIG. 40 shows a set of orthogonal axes: axis x which is aligned along the length of the boat 2, axis y which is aligned across the width of boat 2, and axis z which is normal to axes x and y. These axes are referred to in the description which follows. The kite force F is considered to act as three vectors, F_x, F_y and F_z acting parallel to the x, y and z axes respectively.

Referring now to FIGS. 51 and 57 of the accompanying drawings which show a control arrangement 1 of an embodiment of the invention mounted on a boat 2.

In this embodiment, the control arrangement 1 is mounted in base unit 27 which at least partly surrounds the mast 3, below the point where biasing arrangement 12 is connected to mast 3. Base unit 27 restrains the base of control arrangement 1 in the x, y and z directions and prevents rotation of control arrangement 1 about the x and y axes. The control arrangement 1 is free to rotate about the z axis.

In this embodiment, the base unit 27 is mounted on mounting bracket 100 which is fixed to the boat 2.

The base unit 27 is held against mounting bracket 100 by restraint lines 101 and 102. Quick release fixings 103 and 104 enable restraint lines 101 and 102 to be released from the cockpit 133 by a crew member 34. If the quick release fixings 103 and 104 are released the base unit 27, together with control arrangement 1, detaches from and becomes independent of the boat 2.

Each end of restraint line 101 is anchored to mounting bracket 100. Between these anchor points, the restraint line 101 passes around the upper part of base unit 27. Restraint line 101 is preferably tensioned so that restraint line 101 holds the top of base unit 27 tight against mounting bracket 100.

Each end of restraint line 102 is anchored to mounting bracket 100. Between these anchor points, the restraint line 102 passes around the lower part of base unit 27. Restraint line 102 is preferably tensioned so restraint line 102 holds the bottom of base unit 27 tight against mounting bracket 100.

Bearings 105 and 106 allow control arrangement 1 to rotate about the z axis relative to base unit 27. Bearings 105 and 106 each deliver loads in the xy plane from control arrangement 1 to base unit 27. Bearing 105 is located in the upper part of base unit 27, bearing 106 is located in the lower part of base unit 27, the bearings 105 and 106 are therefore separated from one another in the z direction. The base unit 27 and bearings 105 and 106 together restrain control arrangement 1 in directions parallel to the x and y axes and also against rotation about the x and y axes.

A first vertical restraint plate 107 minimises or prevents the control arrangement 1 from moving in the positive z direction relative to base unit 27. The first vertical restraint plate 107 is preferably removable so that control arrangement 1 may be detached from base unit 27. A low friction washer 109 between the first vertical restraint plate 107 and the base of the mast 3 minimises resistance against rotation of control arrangement 1 about the z axis.

A second vertical restraint plate 108 minimises or prevents the control arrangement 1 from moving in the negative z direction relative to base unit 27. A low friction washer 110 between the second vertical restraint plate 108 and the base of the mast 3 minimises resistance against rotation of control arrangement 1 about the z axis.

While base unit 27 is held against mounting bracket 100 by restraint lines 101 and 102 fin 98 on base unit 27 interlocks with fin 99 on mounting bracket 100 to minimise or prevent base unit 27 from moving in the z direction relative to mounting bracket 100. The interlock is profiled such that when quick release fixings 103 and 104 are released base unit 27 is free to rotate about the y axis, this prevents base unit 27 from becoming jammed on mounting bracket 100.

Base unit 27 and mounting bracket 100 are preferably arranged so that the crew lines 23 and 24 exit base unit 27 free from obstruction.

Fine Tuning Heeling Moments

Referring now to FIG. 30 of the accompanying drawings, in one embodiment of the invention the fixing point 21 is moveable vertically from the base of the mast 3 by a distance +/−Q. In this embodiment, the second mounting point 18 is positioned halfway along the length of the arm 4 and so movement of the fixing point 21 by a distance Q results in the line of action 15 moving in the same direction by a distance 2Q.

The movement of the fixing point 21 moves the line of action 15 so that the line of action 15 does not pass through the centre of lateral resistance 14 and so the control arrangement 1 exerts a heeling moment on the boat 2 when the control arrangement 1 is in equilibrium. The heeling of the boat can therefore be tuned by moving the fixing point 21. This may be necessary to finely tune the control arrangement 1 to take into account slight variations in the position of the centre of lateral resistance 14 when the boat 2 is travelling at different speeds or in different sea conditions. The movement at fixing point 21 may be made manually, or by mechanical, electronic or hydraulic means.

In further embodiments of the invention movement of the fixing point 21 by a distance Q results in the line of action 15 moving in the same direction by a distance NQ where N is a positive integer and corresponds to the number of loops in the biasing arrangement 12.

Referring now to FIG. 31 of the accompanying drawings, in a further embodiment the drive lines 6, 7 are fixed to fixing point 21 which is free to travel vertically on the mast 3. The fixing point 21 is connected to a tuning line 39. The tuning line 39 extends slideably through the aperture in the base unit to an adjustable cleat 40 which is fixed to the boat. The length of the tuning line may be adjusted by fixing the tuning line 39 at different positions in the cleat in order to tune the heeling moment applied by the control arrangement 1 to the boat 2. In this embodiment, the crew lines 23, 24 are positioned on either side of the tuning line 39 and arranged to rotate around the tuning line 39. The tuning line 39 may be adjusted manually, or by mechanical, electronic or hydraulic means.

Referring now to FIG. 32 of the accompanying drawings, the embodiment shown in FIG. 31 may be modified to a yet further embodiment which incorporates a foot bar 41 which is connected to the crew lines 23, 24. In this embodiment, the tuning line 39 extends through an aperture in the centre of the foot bar 41 to the cleat 40. This embodiment combines the foot control features of the foot bar 41 with the tuning line 39. The tuning line 39 may be adjusted manually, or by mechanical, electronic or hydraulic means.

Roll Stabilization

In further embodiments of the invention, the control arrangement 1 incorporates a motor which controls the fine tuning of the heeling moment. The motor is configured to automatically adjust the heeling moment applied by the control arrangement 1 to the boat 2 in order to counteract any roll of the boat 2. The motor can therefore be used to actively stabilise the boat 2.

The motor may be mounted at the foot of the mast or on the hull of the boat to control a tuning line 39. Alternatively the motor may be mounted on the arm 4 to adjust the location of the mounting points of the biasing arrangement 12 on the arm 4, this has the same effect as adjusting the height of the mounting points at the foot of the mast.

Adjusting the Line Lengths, Launching and Retrieving the Kite or Aerofoil

In an arrangement similar to that shown in FIG. 31 of the accompanying drawings in one embodiment of the invention the drive lines 7, 8 extend through the base of the mast

The drive lines 7, 8 extend through the aperture in the base unit to an adjustable cleat 40 which is fixed to the boat. The length of the drive lines 7, 8 may be adjusted by fixing the drive lines 7, 8 at different positions in the cleat in order to move the kite 6 closer to or further from the boat 2. In this embodiment, the crew lines 23, 24 are positioned on either side of the drive lines 7, 8 and arranged to rotate around the drive lines 7, 8. The drive lines 7, 8 may be adjusted manually, or by mechanical, electronic or hydraulic means.

In this embodiment, the control lines 10, 11 are wrapped around the rotatable element 17 as the drive lines 7, 8 are wound onto the drum 42. All of the lines may therefore be wound in together to bring in the kite 6.

In a further embodiment of the invention the drive lines 7, 8 extend through the base of the mast

The drive lines 7, 8 extend through the aperture in the base unit to an adjustable cleat 40 which is fixed to the boat. The length of the drive lines 7, 8 may be adjusted by fixing the drive lines 7, 8 at different positions in the cleat in order to move the kite 6 closer to or further from the boat 2. In this embodiment, the control lines 10, 11 are positioned on either side of the drive lines 7, 8 and arranged to rotate around the drive lines 7, 8. The drive lines 7, 8 may be adjusted manually, or by mechanical, electronic or hydraulic means.

In this embodiment, the length of the control lines 10, 11 must be adjusted as the length of the drive lines 7, 8 are adjusted.

Referring now to FIG. 33 of the accompanying drawings, in one embodiment of the invention the drive lines 7, 8 are wound around a drum 42. The drum 42 winds in the drive lines 7, 8 to bring in the kite 6. In this embodiment, the control lines 10, 11 are wrapped around the rotatable element 17 as the drive lines 7, 8 are wound onto the drum 42. All of the lines may therefore be wound in together to bring in the kite 6.

In a further embodiment, the drum 42 is positioned on the arm 4. This embodiment operates as described above, but with the drum 42 located on the arm 4 for use when the drive lines 7, 8 terminate on the arm 4.

Referring to FIG. 34 of the accompanying drawings, a further embodiment of the invention incorporates a wind powered drive element in the form of a collapsible wing 64. The collapsible wing 64 is attached to a control arrangement 1 of the type described above by drive lines 7, 8 and control lines 10, 11.

The wing in this embodiment is collapsible but it is to be appreciated that further embodiments of the invention incorporate a wing or another wind powered element with an aerofoil section which is either fixed or collapsible.

Referring to FIGS. 35 and 36 of the accompanying drawings, the wing 64 may be similar to the type typically used for hang-gliding. The wing 64 incorporates two elongate leading edge struts 65, 66 which are attached to struts 72, 73. The struts are pivotally connected to one another at one end 75 by a pivotal connection. In this embodiment a flexible elongate element 67 is used to draw the ends of the leading edge struts 65, 66 together and thus open the wing. A flexible elongate element 74 connects the outer ends of the leading edge struts 65, 66. The struts 65, 66 are held in sleeves 68, 69 which are sewn in a substantially triangular sheet of flexible material 70. The flexible material 70 extends between the struts 65, 66 and the flexile elongate cable element 74 to define a typical wing shape. When the wing is opened the fabric material 70 is drawn taut between the leading edge struts 65, 66 and the elongate cable element 74.

The wing 64 incorporates a float element 71 which is generally fin-shaped to reduce air resistance when the wing is in flight. The float element 71 is attached to one of the leading edge struts 65 and to support struts 72, 73 which extend from the float element 71 to a connection with a respective one of the leading struts 65, 66.

The float element 71 is configured to float on water, as shown in FIG. 37. The float element 71 is positioned near the front of the wing 64 so that the front of the wing 64 floats out of the water, as shown in FIG. 37. This ensures that the wing 64 floats with the flexible sheet 70 held at an angle of incidence to the wind which makes it possible to re-launch the wing 64 if the wing 64 lands on water. The top and bottom surfaces of the wing and float may have identical geometry so that it makes no difference which way up the wing is flown, nor does the way up affect the relaunch capacity.

Referring now to FIGS. 38a-38c, the wing 64 is assembled on the deck of a boat by:

i) Drawing the fabric sleeves 68, 69 over the leading edge struts 65, 66 and fixing the corners of the sleeves to the ends of the leading edge struts 65, 66 and to one another (on the back edge of the wing) as shown in FIG. 38b.

ii) Connecting the drive lines and the control lines to the wing.

iii) If necessary moving the closed wing forward along the deck so that the wing is forward of the end of the arm 4 as shown in FIG. 38c.

iv) Pivoting the struts 65, 66 about their pivotal connection 75 to open the flexible sheet 70 as shown in FIG. 39.

v) The wing 34 can then be launched from the deck of the boat with the drive lines 7, 8 and the control lines 10, 11 connecting the wing 64 to the control arrangement 1. Once in the air, it is to be appreciated that the wing 64 flies in a similar manner to the kite 6 described above. The control arrangement 1 automatically tracks the movement of the wing 64 without the need for any external control or energy input.

Throughout the launching process the boat is orientated so that the wind is directed on the stern of the boat. This places the wind on the leading edge of the wing. Alternatively, if control arrangement 1 is located towards the front of the boat, then the arrangement of the wing on the boat is reflected and so throughout the launching process the boat is orientated so that the wind is directed on the bow of the boat, once again placing the wind on the leading edge of the wing.

The process is reversed for retrieving the wing to the boat.

A similar process to the one described above may be adopted for launching and retrieving a kite, rigid wing or other wind power device.

Location of the Control Arrangement on the Boat, and the Arrangement of Hydrofoils or Trim Tabs

At speeds corresponding to a Froude number of up to around 0.45 a hull operates in the displacement mode.

For hulls operating in the displacement mode the control arrangement 1 can be located at any point along the length of the hull. It may be most practical to locate the control arrangement 1 on the bow of the boat 2, this will provide the maximum deck area free from rigging and minimise the risk of the arm 4 sweeping across the deck.

A keel or centreboard will be required below control arrangement 1 to resist lateral loads.

At speeds corresponding to Froude numbers above about 0.45 a hull starts gain some support from hydrodynamic lift and the hull begins to plane.

The location of the control arrangement 1 on a boat 2 and the corresponding arrangement of any hydrofoils or trim tabs is important if the boat 2 is to plane. If the control arrangement 1 and any hydrofoils/trim tabs are located correctly, resistance is minimised and the hull is able to plane. If the control arrangement 1 or any hydrofoils/trim tabs are located incorrectly resistance is high and it is very difficult to provide sufficient power for the hull to plane.

i) Theory of Planing Hulls

As a boat travels through water, water is moved to make way for the hull. In order to be moved, the water is accelerated to have a velocity and momentum. A force is applied by the hull to accelerate the water and an equal and opposite force is applied by the water on the hull. At high speed and with suitable hull geometry this hydrodynamic force can be sufficient to support the boat. When this happens the boat is planing.

The component of the hydrodynamic force acting parallel to the z axis is referred to as the hydrodynamic lift, the component of the force acting parallel to the x axis is referred to as the hydrodynamic resistance or hydrodynamic drag. The hydrodynamic lift P can be represented as a vector passing through a point on the hull, the position of this point varies in the x direction as the boat speed and trim angle vary. Similarly the hydrodynamic resistance can be represented by a vector R passing through a point on the hull, the position of this point varies in the z direction as the boat speed and trim angle vary.

As the trim angle increases the hydrodynamic lift increases, the hydrodynamic resistance increases, and the frictional resistance of water on the hull becomes less significant since the wetted area reduces. At low trim angles frictional resistance dominates, at high trim angles hydrodynamic resistance dominates. There is a trim angle where the total resistance is a minimum, for a boat without hydrofoils this generally this occurs at a trim angle of around 4 degrees.

ii) Analysis of Planing Motorboats

It is usual to take moments about the point where the vectors representing the propeller thrust and the hydrodynamic lift P intersect 90. To establish the trim angle and power required the moments due to water resistance on the hull and appendages must be balanced by the moments due to the self weight of the vessel. This principle is illustrated in FIG. 41.

iii) Analysis of a Planing Hull with an Embodiment of the Invention

The same theory is suitable for analysis of a planing boat using an embodiment of the invention. In this case, the kite force F is considered to act as three vectors F_x, F_y and F_z acting parallel to the x, y and z axes respectively and all passing through the centre of lateral resistance 14. Moments are taken about the point where the vector F_x and the hydrodynamic lift P intersect 90. The position of the intersection 90 varies in the x direction as the position of the hydrodynamic lift P varies. The position of the intersection 90 is constant in the y and z directions.

To establish the trim angle τ, the kite force F_z and the kite force inclination 8 required, the moments due to water resistance R on the hull and appendages, the moments due to lift K generated by any hydrofoils or trim tabs and the moments due to the vertical component F_z of the kite force F must be balanced by the moments due to the self weight G of the vessel. This principle is illustrated in FIG. 42. Taking moments about the intersection 90 to calculate the pitching

M _p =F _z(t−r)+K(f−r)cos τ+Rj−G(s−r)cos τ  [equation 15]

When equilibrium is attained M_p=0 and, since F_z=F sin θ:

$\begin{array}{cc}K=\left[G\left(s-r\right)-\frac{\mathrm{Rj}+F\left(t-r\right)\sin \theta }{\cos \tau }\right]\frac{1}{\left(f-r\right)}& \left[\mathrm{equation}16\right]\end{array}$

The relationship between K and θ is illustrated in FIG. 43.

In order for equilibrium to be achieved without the use of hydrofoils or trim tabs, K=0 and:

$\begin{array}{cc}\cos \tau =\frac{\mathrm{Rj}+F\left(t-r\right)\sin \theta }{G\left(s-r\right)}& \left[\mathrm{equation}17\right]\end{array}$

The relationship between τ and θ is illustrated in FIG. 44.

FIG. 44 demonstrates that without the use of hydrofoils or trim tabs, the trim angle τ must vary widely to maintain equilibrium as the kite is flown higher or lower and θ varies. FIG. 44 also illustrates that for many values of θ the trim angle τ falls outside the range in which it is typically possible for a hull to plane. As θ varies the trim angle τ alters so much that the resistance increases sufficient to cause the hull to slow down and return to displacement action. Without the use of hydrofoil(s) or trim tabs it is not possible to plane consistently as θ varies.

Therefore one embodiment of the invention is most sensibly combined with an arrangement of hydrofoils or trim tabs which maintain the trim angle as θ varies.

Generation of lift is more efficient by hydrofoil action than by trim tabs, less resistance is generated by a foil system than is generated by trim tabs generating an equal load. Therefore the stabilising force K is more sensibly provided by a hydrofoil or hydrofoils than by the use of trim tabs.

The value of the hydrodynamic lift force P must be positive, otherwise the boat will pitch forwards until the bow comes into contact with the water, which may lead the boat 2 to pitchpole. For P to be positive the hydrofoil(s) must be forward of the centre of gravity. To minimise resistance the hydrofoil(s) should be located close to the centre of mass, but sufficiently far forward of the centre of mass to maintain a positive value of P under the varying actions of the waves and wind.

A centreboard(s) or keel(s) is (are) required below the control arrangement 1 to resist the lateral load F_y. Sensibly dimension t should equal dimension f so that the control arrangement 1 is located above the hydrofoil(s) which allows the elements connecting the foils to the hull to act as the centreboard(s) or keel(s) resisting the lateral load F_y.

At times when the boat is moving through the water at very low speed there is insufficient load generated by the keel(s)/centreboard(s) to resist the lateral load F_y. If the control arrangement 1 is located forward of the centre of mass the boat rotates about the z axis so that the bow follows the kite and the boat starts to move forwards. If instead the control arrangement 1 is located behind the centre of mass the boat rotates so that the stern follows the aerofoil and the boat starts to move backwards. It is therefore preferable to locate control arrangement 1 forward of the centre of mass of the boat.

A consequence of placing the control arrangement 1 forwards of the centre of mass is that as the boat planes with a trim angle τ, at the point where the control arrangement 1 is located the hull lifts clear of the water by a distance h. The hydrofoil(s) should track the level of the water surface to maintain the centre of lateral resistance 14 at approximately constant depth and so constantly at approximately a distance H below the pivot point 5.

Many alternative arrangements may be used to maintain a hydrofoil at approximately constant depth below the water surface. The following methods have a successful record of passively tracking the water surface without external control or energy input:

• • Ladder foils
  • V foils with a dihedral angle
  • V foils with an anhedral angle
  • Variable incidence foils with feeler arms
  • Wand and flap control as used on foiling moth sailing dinghies.

Alternatively the hydrofoil arrangement illustrated in FIGS. 53 to 56 of the associated drawings and described below may be used to maintain a hydrofoil or hydrofoils at approximately constant depth below the water surface without any external controls or energy input.

It is also possible to use active systems to electronically monitor the water surface and adjust the flaps on the foil, or the angle of incidence of the foil accordingly so that the foil maintains an approximately constant depth below the water surface.

The control arrangement 1 is proportioned so that the kite force F acts through the centre of lateral resistance while the boat 2 is planing, with the hull locally lifted clear of the water by an amount h.

While the boat 2 is travelling fast enough for the hydrofoil(s) to keep the hull lifted the lateral load F_y acts through the centre of lateral resistance 14, therefore no rolling moment is applied to the hull. At slower speeds when the hydrofoil(s) do not lift the hull clear of the water the submerged length of the centreboard(s)/keel(s) 15 is greater and the centre of lateral resistance 14 is therefore raised. This causes a small misalignment of the lateral load F_y and the centre of lateral resistance, which results in a small rolling moment on the boat 2 when it is travelling at low speed in the displacement mode, the boat 2 heels slightly to resist this rolling moment.

If two hydrofoils 95 are used arranged one on each side of the boat, when the hull is lifted clear of the water the surface tracking behaviour of the hydrofoils resists rolling motions of the boat. This is illustrated in FIG. 45.

Similarly a dihedral hydrofoil 95 may be arranged so that when the hull is lifted clear of the water the hydrofoils resists rolling motions of the boat. This is also illustrated in FIG. 45.

FIG. 46 illustrates a boat with control arrangement 1 and two hydrofoils 95 arranged as described above. Control arrangement 1 is located forward of the centre of mass of the boat, two hydrofoils 95 are located one on each side of the boat and at the same distance forward of the stern as control arrangement 1 (t=f). A passive system is used by the hydrofoils 95 to track the water surface and automatically maintain the hydrofoils 95 at approximately constant depth below the water surface. The elements 96 which connect the hydrofoils to the hull also act as centreboards to resist the lateral load F_y which acts through the centre of lateral resistance 14 when the hull is locally lifted clear of the water by the hydrofoils 95.

FIG. 47 illustrates another boat with control arrangement 1 and hydrofoils 95. Control arrangement 1 is located at the stern of the boat, one hydrofoil 95 is located at the bow. A passive system is used by the hydrofoil 95 to track the water surface and automatically maintain the hydrofoil 95 at approximately constant depth below the water surface. Since the control arrangement 1 is near the stern the rudder and centreboard/keel can be combined in a single element, this has the following benefits:

• • Total resistance is lower due to a single rudder-keel than for two separate elements.
  • Since the rudder-keel is near the stern of the vessel it is not lifted out of the water as the trim angle increases. The distance of the centre of lateral resistance 14 below the pivot point 5 is therefore nearly constant. Therefore the performance of the control arrangement 1 in minimising heeling moments will not be compromised as the trim of the boat varies.
  • The rudder-keel can be rotated, this allows the angle of incidence of the rudder-keel to be adjusted so that the lateral load from the kite is balanced by the rudder-keel, and there is no requirement for leeway of the entire vessel to generate lateral loads on a fixed centreboard or keel: Leeway can be eliminated.
  • Since leeway is avoided the hull will travel through the water along the axis of the hull, this further reduces resistance.
  • Since leeway is avoided a deep V hull form can be adopted without increasing resistance due to vortex shedding as water flows across the hull. The deep V hull form improves course keeping in heavy seas, and also reduces pounding in waves

iv) A Boat Fully Supported on Hydrofoils with an Embodiment of the Invention

The control arrangement 1 may be fitted to a boat which is fitted with hydrofoils which lift the hull clear of the water along the full length of the boat. Typically 2 or more hydrofoils are used to support the boat.

A centreboard(s) or keel(s) is (are) required to resist the lateral load F_y. The elements which connect the hydrofoils to the hull may also act as keels to resist the lateral load F_y. One or more of the elements may also act as a rudder. Sensibly the control arrangement 1 is located above the centre of lateral resistance 14 of the combined set of centreboards/keels.

At times when the boat is moving through the water at very low speed there is insufficient load generated by the keel(s)/centreboard(s) to resist the lateral load F_y. If the control arrangement 1 is located forward of the centre of mass the boat rotates so that the bow follows the kite and the boat starts to move forwards. If instead the control arrangement 1 is located behind the centre of mass the boat rotates so that the stern follows the aerofoil and the boat starts to move backwards. It is therefore preferable to locate control arrangement 1 forward of the centre of mass of the boat.

A consequence of placing the control arrangement 1 on a boat supported by hydrofoils is that at the point where the control arrangement 1 is located the hull lifts clear of the water by a distance h. The hydrofoil(s) should track the level of the water surface to maintain the centre of lateral resistance at approximately constant depth and so consistently at approximately a distance H below the pivot point 5.

As described above many alternative arrangements may be used to maintain hydrofoils at approximately constant depth below the water surface.

The control arrangement 1 is proportioned so that the kite force F acts through the centre of lateral resistance while the boat is foiling, with the hull locally lifted clear of the water by a distance h.

While the boat is travelling fast enough for the hydrofoil(s) to keep the hull lifted the lateral load F_y acts through the centre of lateral resistance, therefore no rolling moment is applied to the hull. At slower speeds when the hydrofoil(s) do not lift the hull clear of the water the submerged length of the centreboard(s)/keel(s) is greater and the centre of lateral resistance is therefore raised. This causes a small misalignment of the lateral load F_y and the centre of lateral resistance, which results in a small rolling moment on the boat when it is travelling at low speed in the displacement mode, the boat heels slightly to resist this rolling moment.

FIG. 48 illustrates a boat with control arrangement 1 and hydrofoils 94 and 95 arranged as described above. Control arrangement 1 is located forward of the centre of mass of the boat, and above the centre of lateral resistance of the combined keels. A passive system is used by the hydrofoils 94 and 95 to track the water surface and automatically maintain the hydrofoils 94 and 95 at approximately constant depth below the water surface and so consistently at approximately a distance H below the pivot point 5. The elements 96 and 97 which connect the hydrofoils 94 and 95 to the hull also act as keels to resist the lateral load F_y which acts through the centre of lateral resistance when the hull is lifted clear of the water by the hydrofoils 94 and 95.

FIG. 49 illustrates another boat with control arrangement 1 and hydrofoils 94 and 95. Control arrangement 1 is located near the stern of the boat, and above the rear hydrofoil 94. A passive system is used by the hydrofoils 94 and 95 to track the water surface and automatically maintain the hydrofoils 94 and 95 at approximately constant depth below the water surface. The element 97 which connects the rear hydrofoil 94 to the hull also act as a keel to resist the lateral load F_y which acts through the centre of lateral resistance when the hull is lifted clear of the water by the hydrofoils 94 and 95. As the boat 2 moves through waves the bow tends to rise and fall relative to the water surface, the stern maintains a more constant height above the water surface, therefore locating the control arrangement 1 above the rear hydrofoil 94 minimises variation in the distance between the pivot point 5 and the centre of lateral resistance 14, this reduces the rolling moment applied to the boat 2.

Mounting the Control Arrangement on a Displacement Hull

Referring to FIG. 50 of the accompanying drawings, in one embodiment the base unit of the control unit 1 is mounted to a centreboard 43 which is configured to be attached to a boat. The centreboard 43 is also known as a keel. The centreboard 43 incorporates a planar top section 44 with two centreboard sections 45, 46 projecting downwardly from each end. The centreboard 43 is mounted to a displacement boat such as a kayak 47 by placing the centreboard 43 over the boat 47 with the centreboard sections 45, 46 extending downwardly on each side of the kayak 47. A boat which does not normally have a centreboard can thus be adapted to incorporate a centreboard along with a control arrangement 1 of an embodiment of the invention so that the boat can be powered by a wind powered element such as a kite.

Mounting the Control Arrangement on a Planing Hull

Referring now to FIGS. 51 to 56 of the accompanying drawings which show an embodiment of the control arrangement 1 mounted on a boat 2 which is designed to plane.

Two centreboards 111 and 112 are located one on each side of the boat. The centreboards 111 and 112 are located the same distance forward of the stern 134 as the mast 3. The centreboards resist the component of the kite force F in the y direction, F_y.

A hydrofoil 113 spans between the two centreboards 111 and 112. Pins 115 at each end of the hydrofoil pass through low friction sleeves 116 to position the hydrofoil 113 between the centreboards 111 and 112. Fixings 128 prevent the pins 115 from pulling out through the centreboards 111 and 112.

The mean camber line of the hydrofoil 113 is the locus of points midway between the upper and lower surfaces. The chord line of the hydrofoil 113 is a straight line connecting the leading and trailing edges of the airfoil. If the mean camber line is coincident with the chord line a foil is symmetric. If the mean camber line is not coincident with the chord line a foil is cambered.

A lift force is generated on a foil section, such as an hydrofoil, moving through a fluid, such as water. The lift on the foil section is a distributed force that can be said to act at a point called the centre of pressure. Many foils have a cambered profile, so that the mean camber line is not coincident with the chord line. As the angle of incidence changes on a cambered foil, there is movement of the centre of pressure forward or aft, resulting in a pitching moment about the centre of pressure. In the case of a symmetric foil, the lift force acts through one point for all angles of attack, and the centre of pressure does not move. Consequently on a symmetric foil there is no pitching moment about the centre of pressure as the angle of incidence changes.

The hydrofoil 113 is a symmetric foil, therefore there is no pitching moment on the hydrofoil 113 as the angle of incidence varies.

At each end hydrofoil 113 pins 120 extends into slots 121 in the centreboard 111 or 112. Pins 120 are aft of pins 115. A resilient element in the form of an elastic chord 122 is connected to the end of pin 120 which is distant from hydrofoil 113. Chord 122 passes through the vertical sleeve 131 in the centreboard 111 or 112 to anchor point 127 in the head unit 136 of the centreboard 111 or 112. Chord 122 is stretched so that the chord 122 is under tension, this tends to cause the trailing edge of the hydrofoil 113 to rise which reduces the angle of incidence. of the hydrofoil 113.

At each end hydrofoil 113 pins 117 extend into slots 118 in the centreboard 111 or 112. Pins 117 are forward of pin 115. A notionally inextensible chord 119 is connected to the end of pin 117 which is distant from hydrofoil 113. Chord 119 passes through the vertical sleeve 132 in the centreboard 111 or 112, through the centreboard head unit 136 to mounting point 125 on arm 126. Pin 123 passes though arm 126 and a low friction sleeve in the bowsprit 129 to connect the arm to the bowsprit and allow the arm 126 to rotate about a vector parallel to the y axis. Surface flap 114 is mounted on arm 126. The trailing edge of surface flap 114 rests on the water surface, as the boat 2 lowers in the water pressure on surface flap 114 causes arm 126 to rotate which acts through chord 119 to cause the angle of incidence of the hydrofoil 113 to increase. Conversely as the boat 2 rises out of the water arm 126 rotates as the tension in chords 122 causes the angle of incidence of hydrofoil 113 to reduce.

The arrangement of hydrofoil 113, surface flap 114, arm 126, chords 119 and 122 and the associated pins, sleeves, slots and openings cause the hydrofoil 113 to remain at approximately constant depth below the water surface without any external control or energy input.

The length of the arm 126 may be altered to adjust the response of the hydrofoil 113 to variations in the water surface. A longer arm 126 will result in a smaller change in the angle of incidence of the hydrofoil for a given change in the depth of water above the hydrofoil 113: Increasing the length of the arm 126 reduces the responsiveness of the hydrofoil 113 to changes in the water surface. Conversely reducing the length of the arm 126 increases the responsiveness of the hydrofoil 113 to changes in the water surface.

It is to be appreciated that a control arrangement 1 of an embodiment of the invention may be used with any type of boat or watercraft including, but not limited to: a surfboard, raft, kayak, canoe, dinghy, yacht or ship, whether monohull or multihull, displacement, planing or hydrofoil.

Whilst embodiments described above have been for use on a boat, it is to be appreciated that embodiments of the invention may be installed on a land snow or ice based wind powered vehicle. A typical land, snow or ice based wind powered vehicle sits on wheels, skis or a sledge. In these land, snow or ice based embodiments, the centre of lateral resistance is where the wheels, skis or sledge contact the surface on which they are resting. It is to be appreciated that control arrangements of embodiments of the invention used on land, snow or ice based wind powered vehicles operate in the same manner as described above to enable the control arrangement 1 to automatically track a wind powered element without the need for any external energy input to control the arrangement.

When used in this specification and claims, the terms “comprises” and “comprising” and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

Claims

1. A control arrangement for a wind powered vehicle, the arrangement comprising: a first elongate support member,a second elongate support member which is pivotally mounted at a pivot point to the first support member, the second support member having a free end which is remote from the pivot point,a flexible elongate drive line which is attachable at one end to a wind powered drive element which, in use, applies a drive force to the drive line, wherein the drive line extends slideably through a first mounting point adjacent the free end of the second support member such that the drive force applies a first moment to the second support member about the pivot point,a biasing arrangement comprising: at least one additional mounting point which is provided on the second support member between the free end and the pivot point,at least one further mounting point which is provided on the first support member,a fixing point which is provided on one of the second support member and the first support member, anda portion of the drive line which extends slideably through each additional mounting point on the second support member and each further mounting point on the first support member, wherein the portion of the drive line extends a plurality of times between the additional mounting points on the second support member and the further mounting points on the first support member, the drive line being fixed to the fixing point so that the biasing arrangement is configured to convert the drive force into a biasing force and to apply the biasing force to the second support member at the additional mounting points to at least partly cancels the first moment applied to reduce the overall moment to the second support member about the pivot point in a first plane,wherein the control arrangement further comprises:a base unit rotatably attached to the first support member, the first support member being rotatable about an axis by any number of 360° rotations or part rotations relative to the base unit and configured to rotate relative to the base unit until the second support member is aligned such that no overall moment is applied in a second plane to the second support member.

2. A control arrangement according to claim 1, wherein the number of times the drive line extends between the additional mounting points and the further mounting points is N and each additional mounting point is positioned on the second support member at substantially 1/N of the distance between the pivot point and the free end.

3. A control arrangement according to claim 1, wherein the number of times the drive line extends between the additional mounting points and the further mounting points is N and each further mounting point is positioned on the first support member at substantially 1/N of the distance between the pivot point and the centre of resistance to lateral movement.

4. (canceled)

5. (canceled)

6. (canceled)

7. (canceled)

8. A control arrangement according to claim 2, wherein the position of each additional mounting point on the second support member between the free end and the pivot point is adjustable by a modification value which is proportional to the frictional resistance between the drive line and at least one of the mounting points.

9. A control arrangement according to claim 3, wherein the position of each further mounting point on the first support member is adjustable by a modification value which is proportional to the frictional resistance between the drive line and at least one of the mounting points.

10. A control arrangement according to claim 1, wherein the arrangement further comprises a resilient element which is attached to the first and second support members, the resilient element providing a resilient bias between the first and second support members to at least partly cancel a moment applied to the second support member by the weight of the second support member.

11. A control arrangement according to claim 6, wherein the resilient element is attached to at least one extension element which is attached to one of the first and second support members.

12. (canceled)

13. A control arrangement according to claim 1, wherein the arrangement further comprises two flexible elongate control lines which are attachable at one end to the wind powered drive element to control the wind powered drive element, wherein the control lines extend slideably through the first mounting point adjacent to the free end of the second support member.

14. A control arrangement according to claim 8, wherein a portion of each control line is incorporated into the biasing arrangement and as such extends slideably a plurality of times between the additional mounting points and the further mounting points.

15. A control arrangement according to claim 8, wherein the drive line extends at least partly around a rotatable element which is provided at the pivot point, the control lines extend at least partly around the rotatable element and the control lines and the drive line wind onto or reel out from the rotatable element as the rotatable element rotates.

16. A control arrangement according to claim 1, wherein the base unit incorporates an aperture and the elongate axis of the first support member is at least partly aligned with the aperture in the base unit.

17. A control arrangement according to claim 11, wherein the arrangement further comprises two flexible elongate control lines which are attachable at one end to the wind powered drive element to control the wind powered drive element, and wherein the control lines extend through the aperture in the base unit.

18. A control arrangement according to claim 11, wherein the arrangement further comprises two flexible elongate control lines which are attachable at one end to the wind powered drive element to control the wind powered drive element, and wherein the arrangement further comprises two crew lines which are connected respectively to the two control lines, the crew lines extending through the aperture in the base unit.

19. (canceled)

20. A control arrangement according to claim 12, wherein the control lines are connected to mechanical control arrangement.

21. (canceled)

22. A control arrangement according to claim 13, wherein the crew lines are connected to a mechanical control arrangement.

23. A control arrangement according to claim 1, wherein the first support member is rotatable relative to the base unit about an axis aligned with a z direction, and wherein the base unit minimises or prevents movement of the first support member relative to the base unit in x, y and z directions, the x and y directions being perpendicular to one another and perpendicular to the z direction, and wherein the base unit minimises or prevents rotation of the first support member relative to the base unit about axes aligned with the x and y directions.

24. (canceled)

25. A control arrangement according to claim 1, wherein the base unit is releasably attached to the first support member.

26. A control arrangement according to claim 1, wherein the each further mounting point on the first support member is moveable to adjust a heeling moment applied by the control arrangement to the vehicle.

27. A control arrangement according to claim 18, wherein the arrangement further comprises an arrangement for adjusting the position of each further mounting point automatically to stabilise the vehicle if the vehicle is subjected to a rolling moment.

28. A control arrangement according to claim 1, wherein each of the lines is releasably attached to a releasable attachment element and wherein the length of the lines is adjustable by winding in or letting out the lines from the releasable attachment element.

29. (canceled)

30. A control arrangement according to claim 1, wherein the arrangement further comprises a wind powered drive element which is connected to one end of the drive line.

31. A control arrangement according to claim 21, wherein the wind powered element is one of an aerofoil section, a kite and a wing.

32. A control arrangement according to claim 1, wherein the control arrangement further comprises one or more additional drive lines.

33. A vehicle comprising a control arrangement according to claim 12, wherein the control arrangement is mounted to the vehicle and the control lines are configured to be pulled in or let out manually by a user.

34. (canceled)

35. (canceled)

36. A vehicle comprising a control arrangement according to claim 13, wherein the control arrangement is mounted to the vehicle and the crew lines are configured to be pulled in or let out manually by a user.

37. (canceled)

38. A vehicle according to claim 33, wherein the control lines are connected to one of a power bar which is mounted to the vehicle and which is operable to be controlled by the hands of a user and a foot bar which is mounted to the vehicle and which is operable to be controlled by the user's feet.

39. A vehicle comprising a control arrangement according to claim 1, wherein the length of the second support member is selected so that the direction of the force exerted by the wind powered element on the drive line extends substantially through the centre of lateral resistance of the vehicle when there is no overall moment applied to the second support member about the pivot point or about the axis of rotation of the first support member.

40. A boat comprising a control arrangement according to claim 1, wherein the base unit is attached to the boat.

41. A boat comprising a control arrangement according to claim 40, wherein the base unit is attached directly to a keel, centreboard or single element comprising both a keel/centreboard and rudder which is configured to be attached to the boat.

42. A boat according to claim 40, wherein the base unit is attached directly to a rudder which is configured to be mounted to the boat.

43. A boat according to claim 42, wherein the rudder is mounted to the boat and the boat does not incorporate a keel or centerboard which is distinct from the rudder.

44. A boat according to claim 42, wherein the rudder is pivotally mounted to or near the rear of the boat.

45. (canceled)

46. (canceled)

47. (canceled)

48. A boat according claim 40, wherein the boat is a boat selected from a group including a raft, surfboard, ship, canoe, kayak, dinghy, yacht, monohull, multihull, displacement vessel, planing vessel and a vessel supported on hydrofoils.

49. A boat according claim 40, wherein the boat comprises at least one hydrofoil element.

50. A boat according to claim 49, wherein each hydrofoil element is moveably mounted to the boat and the control arrangement further comprises an adjustment arrangement which is operable, in use, to adjust the angle of incidence of each hydrofoil element relative to water on which the boat is travelling to maintain each hydrofoil at a substantially constant depth below the surface of the water.

51. A land based wind powered vehicle comprising a control arrangement according to claim 1.

52. A snow or ice based wind powered vehicle comprising a control arrangement according to claim 1.

53. A vehicle according to claim 36, wherein the crew lines are connected to one of a power bar which is mounted to the vehicle and which is operable to be controlled by the hands of a user and a foot bar which is mounted to the vehicle and which is operable to be controlled by the user's feet.

54. A boat according to claim 40, wherein the boat comprises one of a keel, centreboard and a single element comprising both a keel/centreboard and rudder to resist lateral movement of the boat.

55. A boat according to claim 54, wherein the longitudinal axis of the first support member is aligned with the longitudinal axis of the keel or centreboard or single element comprising both a keel/centreboard and rudder.