WO1992022396A2

WO1992022396A2 - Wind powered or assisted hydrofoil craft

Info

Publication number: WO1992022396A2
Application number: PCT/EP1992/001342
Authority: WO
Inventors: Ian James Duncan
Original assignee: Ian James Duncan
Priority date: 1991-06-11
Filing date: 1992-06-11
Publication date: 1992-12-23
Also published as: CA2111239A1; WO1992022396A3; GB9112508D0; JPH06510498A; AU663320B2; ZA924269B; EP0587677A1; AU1901492A

Abstract

The present invention relates to wind powered or assisted craft, particularly hydrofoil craft, which are capable of travelling considerably faster than wind speed over a wide range of wind speeds and directions. The invention has application from single person leisure and sports craft through to large commercial cargo and passenger vessels, although certain aspects of the invention will find application to wind powered or assisted craft or vehicles for use on land and to hydrofoil supported craft in general. Whilst in the case of smaller craft, wind power may provide the sole means of propulsion, in the case of larger craft the provision of auxiliary power sources is likely, as an aid to low-speed man÷uvring and operation in unfavourable wind conditions. Heavier craft may well require the assistance of such power sources to get through the ''resistance hump'' which is characteristic of hydrofoil craft.

Description

WIND POWERED OR ASSISTED HYDROFOIL CRAFT

Field of the invention

The present invention relates to wind powered or assi ted craft, particularly hydrofoil craft, which are c pable of travelling considerably faster than wind spe over a wide range of wind speeds and directions. T invention has application from single person leisu and sports craft through to large commercial cargo a passenger vessels, although certain aspects of the i vention will find application to wind powered or assi ted craft or vehicles for use on land and to hydrofo supported craft in general.

Whilst in the case of smaller craft, wind power m provide the sole means of propulsion, in the case larger craft the provision of auxiliary power sourc is likely, as an aid to low-speed manoeuvring and op ration in unfavourable wind conditions. Heavier cra may well require the assistance of such power sourc to get through the 'resistance hump' which is charact ristic of hydrofoil craft. Description of the Prior Art

Wind powered craft of current art have not found favo other than for leisure or sporting purposes due to l mited performance and the complexity of controlling t large number and area of sails required, the proble of heeling and of going to windward, and the requir ment for relatively high wind speeds to achieve a real performance. Aerofoil sails have been fitted to very limited number of commercial craft as auxilia propulsion devices to reduce fuel consumption and i prove roll damping.

A small number of racing and cruising craft have utili sed aerofoil wings in the past but invariably thes have been designed for use on conventional hulls an effort has been concentrated either on attaining hig lift coefficient or on easy handling. Neither case re suits in the high ratio of lift to drag required to sail at high ratios of boat speed to wind speed. Also the majority of designs have required manual setting in the same way as a conventional sail but as an aerofoil section is generally much less tolerant to changes in incidence constant attention is required if adequate performance is to be achieved. A small number of de¬ signs have appeared using self-trimming wing sets but these also have generally been adapted for conventional hulls rather than being optimised for the higher speeds attainable by the use of well designed hydro¬ foils.

Whilst a number of hydrofoil supported wind-driven craft have appeared in recent years few, if any, have fulfilled the expectations of their designers. There are a number of reasons for this situation. The majority of designs have employed a triangular foil plan with two surface piercing or fully submerged foils situated approximately amidships and spaced either side of the longitudinal axis of the craft and a third in¬ verted 'T' foil at the rear of the craft. This arrange¬ ment results in a short foil-base relative to the loges of the craft which results in excessive variation of foil loading with differing wind and speed conditions. Also because the rear foil has to provide lift in ei¬ ther sense but requires a change in craft attitude to change its angle of attack it has to be long, resulting in a large wetted area and excessive flexure when sub¬ jected to steering loads. In many cases surface piercing foils have been used which suffer from high drag, cannot be reliably used to provide the negative lift required at speed on the windward foil, and are subject to considerable changes in angle of attack due to wave orbital motion and chan- ges in craft attitude which renders them erratic. In cases where fully submerged foils have been applie generally these have been designed to provide upward lift only, or, at best only limited amount of downward lift due to the difficulty in arranging for sensor sys terns to cope with the moment reversal involved. In cer tain cases such foils have been designed for downward only lift which limits their use to a specified tack Also, previous designs using mechanical surface senso systems have used relatively high loads on the planin or buoyant body used to sense the water surface to re duce the chance of moment reversal with a consequenc that these bodies have been relatively large dimensio ned and as they operate at a low ratio of lift to dra the performance of the foil system as a whole has bee poor. Whilst attempts have made to improve the perfor mance of a foil in isolation in wave and chop condi tions these have not resulted in the overall drag re duction expected due to this effect. Another major problem with virtually all foil craft ha been the difficulty of retracting them satisfactoril for launching, mooring and road transport and this fac tor is difficult to resolve due to the high impose loads. Also virtually all hydrofoil craft have bee excessively wide and as hydrofoils or their associate sensors have tended to extend beyond the contours o the craft there is considerable risk of snagging o other craft, buoys, etc, ...

Prior art foil supported sailing craft have generall been based on conventional hull designs such that hy drofoil pivots and attachments have been placed muc higher than ideal above the water line which has resul ted in unnecessarily high deflections seriously impai ring hydrofoil performance. Additionally such hul forms generally perform poorly under the considerabl attitude changes which occur at around lift-off spee due to either fore or aft hydrofoils lifting before th other due to changes in foil loading, and this has mad lifting off erratic.

When travelling at high speeds, and in particular a high ratios of boat speed to wing speed very high for ces are generated and prior art designs have require external rigging to support these loads and this has considerably added to windage.

Summary and objectives of the present invention The present invention overcomes many of these limita¬ tions and permits craft to be designed to operate at speeds hitherto unachievable, except for very high powered racing craft operating on calm water, and to maintain such high speeds under a wide range of wind and sea-state conditions. To achieve such performance requires exceptional aerodynamic and hydrodynamic cleanness for which this present invention provides. In particular, the use of fully submerged lift hydrofoils of high aspect ratio rather than surface piercing or planing hulls to provide the required lift reduces the hydrodynamic drag to the point where the lift^' coeffi¬ cient required of the drive producing aerofoil wing is relatively modest such that it is able to operate at a very much higher ratio of lift to drag than has hither- to been possible.

The power required to drive even efficiently designed hydrofoil or planing powered craft at such speeds is very high indeed and would imply unacceptable levels of fuel consumption and pollution for any practical appli- cation. Furthermore, considerable losses can be expec¬ ted in transmitting such high powers at high speeds. The present invention allows such power to be derived, or largely derived from wind energy with a consequent reduction in pollution, operating costs, and maintenan- ce. The efficient aerofoil wing of the present inventio can generate large amounts of lift even at moderat angles of attack, and, furthermore, the lift generate is proportional to the square of velocity which is als the rate at which drag increases. Thus a craft of thi type can generate a fairly constant accelerating forc over a wide speed range relative to wind speed and because the rolling of pitching moments is counteracte by aerodynamic or hydrodynamic forces the performanc is limited by structural considerations rather than b the maximum righting moment which is limited by weigh and geometry for form or moving ballast stabilised sai ling craft. Additionally the self-trimming wings of th invention allow the wings to be placed to the rear o the craft allowing the crew an unhampered forward vie and also allow the use of more generally used control than is possible in other wind powered craft. Thus, according to a first independent aspect of th present invention a wind powered or assisted hydrofoi craft comprises a hull or fuselage with an upwards ex tending wing which may be pivoted about a generall vertical axis to maintain a controlled angle of attac relative to the apparent wind to produce forward o rearward drive. The surface swept by the lower end o the upward extending wing as it sweeps around its gene rally vertical axis may be a plane surface normal t the wing pivotal axis and in this case the lower end o the wing can rotate at a small vertical distance abov this plane which, as a consequence acts as an effectiv end plate which, in conjunction with its preferre close proximity to the water surface, serves to greatl increase the effective aspect ratio of the wing. Tw generally vertical downward extending surface-piercin hydrofoils which are spaced laterally one from anothe about the craft's longitudinal axis may act as end plates for an aerodynamically shaped hull and act as keels. These hydrofoils are preferably placed towards the rear of the craft. A downward extending surface- piercing hydrofoil pivoted about a generally vertical axis or provided with a generally vertically pivoted flap and spaced at a distance along the craft's longi¬ tudinal axis from the laterally spaced hydrofoils may be provided for steering means and may preferably be positioned towards the front of the craft. At normal operating speeds the hull or fuselage is maintained at a height above the water surface by the hydrodynamic lift produced by the generally horizontal hydrofoils. A generally horizontal hydrofoil, which may be surface- piercing or fully submerged, may be mounted at the lo- wer end of the vertically pivoted hydrofoil to provide vertical lift to support the required proportion of the weight of the craft and offset the pitching moment, etc. Further horizontal or horizontally inclined hydro¬ foils mounted to the lower ends of the laterally spaced vertical hydrofoils and which are preferably provided with means for controlling their angle of attack pro¬ vide the vertical lift to overcome the proportion of the weight of the craft not provided by the first hori¬ zontal hydrofoil and to offset any roll moment etc. The hydrofoils together with any mechanism to control them should preferably be contained within the plan contour of the craft. The hydrofoils are preferably retractable for launching and for operation in shallow water and may remain sufficiently immersed for the craft to operate at restricted performance in the retracted sta¬ te. Landing wheels may be attached to the hydrofoils or their mechanisms for launching such that they are auto¬ matically lowered when the hydrofoils are retracted. Larger, detachable wheels may be fitted for use on land which may be interchangeable with skids for use on ice and the wing control system may be adapted to preven capsize in this case.

The wing may alternatively be fixed to a planar or do med disk pivoted about a generally vertical axis. Suc a configuration eliminates the gap between the wing an the hull resulting in increased aerodynamic efficiency, and usually increases the structural strength an stiffness of the assembly. The upwards extending wing may beneficially be placed towards the rear of the craft. This configuration allows the cockpit to be placed towards the front of the craft giving the crew unhampered visibility whilst also permitting the wing to be positioned as close as possible to the water surface minimizing the rolling moment and maximizing the increase in effective aspect ratio resulting from the mirror-image effect. Whereas mention is made above of a single vertical wing, the principle will equally apply to craft provi¬ ded with multiple vertical or upwards extending wings, the provision of which may be desirable to diminish the moments about the roll and pitch axis of the craft, or to reduce the size of any individual wing. In the case wherein multiple wings are provided each may be pivoted about its own generally vertical axis, all the wings may be pivoted about a single axis, or groups of wings may be pivoted about generally vertical axes. Whilst the wings will normally be rigid or semi-rigid the use of fabric wings with conventional or wing-type masts is perfectly envisageable for lower speeds. Since a craft of this nature will normally operate at speeds well below those at which compressibility effects become significant the wings may have a relati¬ vely thick section which will normally enable the wing to be self-supporting without the requirement for stays or rigging, the provision of which would add considera¬ bly to drag.

The angle of attack of any upwards extending pivoted wing may conveniently be adjusted by adjusting the angle of attack of a small control aerofoil pivoted about an arm or arms extending rearwards from the wing such that the control aerofoil provides a moment about the pivot axis of the wing which overcomes the moment due to the lift generated by the wing, the whole being free to weathercock about the pivot axis of the wing. Where more than one drive producing pivoted wing is provided each wing or group of wings arranged to pivot about a single axis is preferably provided with a control aerofoil to control its angle of attack. The hull provides the buoyancy and stability required to support the craft before it lifts onto its hydro¬ foils and generally links the other elements of the craft and transmits or absorbs the forces they generate and to this end it is preferably made up of aerodynamic sections which provide stiffness and reduce drag. The lower surface of the hull is preferably configured to present three slender hydrodynamic lifting surfaces the centres of lift of which correspond approximately to the centres of lift of the three generally horizontal hydrofoils and which are of higher aspect ratio than would normally be possible for a planing sailcraft. Their angles of attack can be broadly optimised to operate at maximum efficiency within the range craft attitudes anticipated prior to lift-off. The forward lifting surface is preferably split into two portions allowing a central tunnel into which the forward hydro¬ foil can be retracted and rotated for steering. This arrangement can be arranged to be extremely efficicent for the limited range of speeds prior to lift-off. Al- ternatively the three lifting surfaces may be merged into a single surface of moderate aspect ratio. With the preferred hydrofoil and wing configuration the hull may be generally delta shaped with the front of the delta broadened to protect the forward hydrofoil and to provide the forward hydrodynamic lifting surface and with the rear extended laterally to support the rear hydrofoils and to provide the two rear hydrodynamic lifting surfaces which beneficially may be extended by hydrofoil members and may serve to protect the rear hydrofoils and their control mechanisms and in this case the downward extending hydrofoil members serve as end plates further enhancing the aerodynamic perfor¬ mance of the hull and wings. The hull may also be shaped such that the two lateral hull extensions can be hinge mounted to the main hull such that they can be folded inwards together with their affixed hydrofoils for transport or storage allowing the width to be ap¬ proximately halved and allowing simple assembly. The above delta shape also provides an effective end-plate for the wings and a smooth transition between the hull and wings. The preferred rigid wings of the invention are relatively voluminous and the broad rear width of the delta shape permits the provision of a hatch or opening such that the wings can be inserted into the hull for transport or storage.

The rolling moment produced by a hydrofoil of the high aspect ratio required for efficient operation is consi¬ derable and this would normally require that the moment resisting hydrofoils should be placed at a large lateral distance one to the other. This would require a very wide craft and a support structure which would add considerable weight and windage. Additionally the con¬ trol aerofoil described herein above is conventionally placed behind the main drive producing wing or wings and operates in their wake resulting in excessive dra and erratic results.

Thus according to a second independent aspect of the present invention, a wind powered or assisted craft comprises at least one upwardly extending wing arranged to have the high effective aspect ratio required for efficiency but such that the centre of effort is rela¬ tively low ; thus limiting the rolling and pitching moments created. The wing arrangement envisaged can be designed for both a high ratio of lift to drag and an advantageous distribution of lift in the various condi¬ tions of wind shear which may be encountered. In its basic form a wing according to this invention is generally tapered along its length such that the chord at its root is greater than the chord at the wingtip such that the fractional chord of the flap at its base is greater than the fractional chord at its tip and which has at least one trailing edge flap which is ta¬ pered to a greater extent than the wing such that the fractional chord of the flap at its base is greater than the fractional chord at its tip. This arrangement not only provides a centre of area which is below the mid span of the wing but also depending on the relative extent of flap deflection and wind shear can allow the local lift coefficient to be higher at the base of the wing than at its tip, and is particularly effective in the case that the wing is sealed closely to the hull and to the water-plane at its lower end. This variation in local lift coefficient further depresses the height of the centre of effort. The wing may additionally have a tip member pivoted such that it can operate at a ge¬ nerally different angle of attack to the main wing ; the addition of such a tip is particularly advantageous for operation in conditions where the apparent wind is considerably sheared such as occurs when broad reaching. In the case that the wing is pivoted about a generally vertical axis or is a member of a group of wings so pivoted, the pivoted tip may be advantageously swept forwards or rearwards such that its centre of effort is at a distance from the pivot axis for rota¬ tion of the wings such that it stabilises the wing about its pivot axis and such that by changing its angle of attack the angle of attack of the wing or group of wings is also changed. This arrangement is much more efficient than the provision of a control aerofoil arranged generally behind the main wing or wings as it tends to decrease rather than increase induced drag and operates in better airflow conditions rendering it more sensitive. The main wing may be generally boomerang shaped such that the lower part of the wing is generally swept forwards whilst the upper part of the wing is generally swept backwards or vice- versa. This arrangement is particularly efficient in the case where the pivoted tip section is used to control a wing or group of freely pivoted wings as it tends to increase the restoring moment generated by the wing for any change in the angle of attack. The efficiency of the wing may be further increased by twisting it along its length such that it adopts the same angle of attack as the tip section at its upper end. A similar effect may also be achieved by dividing the wing into sections along its length and rotating each section to differing extents. In an arrangement with two or more wings each wing will tend to produce different amounts of lift due to vorti- city and this may be countered by deflecting the flaps and/or the pivoted tips of different wings to differing extents. This is particularly the case where two or a leeward wing stalls before a windward wing the wingset could become unstable. In any arrangement where two wings are arranged to pi¬ vot about a common generally vertical axis they may preferably be arranged such that they splay outwards one to another such that their lower ends are more clo- sely spaced than their upper ends. This arrangement results in a particularly favorable aerodynamic perfor¬ mance and reduces the inertia of the entity which improves dynamic performance. Additionally the pivoted wing tips of the wings of this arrangement may be splayed inwards at their upper ends which further reduces the inertia and reduces the inscribed radius. In the case where the wing control foil constitutes an upward extension to the main wing, the control moment required to rotate the wing tip may conveniently be arranged to partially or completely balance the control moment required to deflect the flap or flaps. The flaps of two or more wings may be arranged to be deflected by a single actuator whilst the tips may be deflected by a linkage situated at the upper end of the wings such that a given flap deflection of any wing results in a corresponding rotation of the tip. In a favoured arran¬ gement, the ratio between the deflection of the flap of any wing and the rotation of its tip may be varied by the provision of an actuator which varies said linkage. A wing may be configurated with two or more flaps in which case said flaps may be arranged to be actuated differentially to further modify the lift distribution along the wing.

As herein above described hydrofoil supported craft of prior art have been designed for vertical lift compo¬ nents in one sense only whereas hydrofoils for high speed wind powered craft require that the windward foil provide a downwards lift component which needs to be provided by the lee hydrofoil the craft weight normally having only a marginal effect. For a craft designed to navigate on either tack any laterally disposed hydr foil will consequently need to be arranged such that can provide similar amounts of vertical lift in eith sense. Thus according to a third independent aspect of t present invention a wind powered or assisted hydrofo craft has at least one hydrofoil comprising a general vertical surface-piercing section, a general horizontal normally submerged section and a general horizontal pivot axis arranged such that the angle attack of the generally horizontal section may be a justed to a similar extent in both positive and nega tive senses wherein the generally horizontal sectio may be adjusted to a similar extent in both positi and negative senses wherein the generally horizonta section is pivotally attached to the lower end of th generally vertical section and wherein the hydrofoil i mounted such as to prevent any reversal in the sense o the moment resulting from the lift and drag force created by said hydrofoil about said pivot axis fro being transmitted to any actuator or surface sensin means which control its motion.

In theory for this case if the hydrofoil were to be pi voted about its centre of lift and assuming this to b coincident with the centre of drag no disturbing momen would be created by the hydrofoil section about sai pivot. However in practice the lift centre is not sta tic and manufacturing tolerances in positioning th axis and manufacturing the foil sections are finite s that some moment will be created which will vary ap proximately linearly with the angle of attack and qua dratically with speed. Thus a simple spring bias is no appropriate and some provision must be made to ensur that the moment created acts always in the same sense For the case in question the generally horizontal hydrofoil may be pivoted about an axis arranged sligh tly in front of its centre of lift and may further com prise at least one downwards projecting fin of suc dimension that for forward motion the sum of the momen created by the vertical lift component generated b said hydrofoil section together with the drag momen created by the fin about the pivot axis of said hydro¬ foil section always acts in the same sense whether said vertical lift component acts in an upwards or downwards sense. The generally horizontal foil section may bene¬ ficially be arranged with dihedral.

The herein above described arrangement suffers from some of the disadvantages of most prior art design in that undesirable flow characteristics around the arti- culation of the generally horizontal hydrofoil section are difficult to mitigate. Furthermore, the hydrofoil sections will normally be small in section and very thin and will consequently need to be thick walled or even solid to prevent excessive deflections. As a re- suit there will be little room to accommodate hydraulic lines, control rods, actuators, and the like within the hydrofoil section.

Thus in an alternative arrangement the generally hori¬ zontal axis is arranged such that it is above the water level for normal foil-borne operation. In this arrange¬ ment the generally horizontal section may be fixed to the generally vertical section which considerably redu¬ ces the problem of assuring a smooth flow pattern and furthermore no pivots, actuators, control lines or the like need to be contained within the hydrofoil itself but instead can be incorporated within the body of the craft. A hydrofoil produced in this manner is simple, lightweight and strong as well as being hydrodynamical- ly efficient. The disadvantage of this arrangement is that the moment of the lift and drag forces about the pivot axis vary considerably with the angle of attac and the immersion depth etc. and furthermore it is nor mally impossible to prevent a reversal of the momen except for small reversals of the design sense of lift. Thus according to a fourth independent aspect of the present invention a wind powered or assisted hydrofoil craft has at least one hydrofoil comprising a generally vertical surface-piercing section a generally horizon¬ tal normally submerged section and a generally horizon- tal pivot axis arranged such that the angle of attack of the generally horizontal section may be adjusted to a similar extent in both positive and negative senses wherein the generally horizontal pivot axis is arranged such that it is above the water surface for normal foil-borne operation such that both the generally ver¬ tical and the generally horizontal hydrofoil sections rotate about the pivot axis as a unity and wherein the hydrofoil is mounted such as to prevent any reversal in the sense of the moment resulting from the lift and drag forces created by the hydrofoil about said pivot axis from being transmitted to any actuator or surface sensing means which control its motion. The mounting arrangement may preferably also include means whereby the variations in said moment are reduced. The hydrofoil mounting may be arranged such that the generally horizontal pivot axis is largely uncons¬ trained for translational movement in a generally ver¬ tical sense and such that the vertical lift component generated by said hydrofoil is largely resisted by part of the craft which is translationally mobile in a gene¬ rally horizontal fore and aft sense relative to said pivot axis such as to prevent said moment reversal and limit variations in such moment. A major difficulty in pivoting any hydrofoil other than generally along its axis is that the forces which need to be restrained tend to be very high and it is diff cult to avoid stress concentrations. Additionally, f any such hydrofoil which is controlled by mechanic surface sensing means in particular it is essential reduce friction torque to a minimum to help avoid e cessive sensor loading.

Thus according to a fifth independent aspect of t present invention any hydrofoil craft comprises least one hydrofoil pivoted about a generally horizo tal axis close to the static water line of the cra which comprises a generally horizontal section arrang such that it provides additional lift during hull-bor operation and such that it is above the water level f normal foil-borne operation and which is arranged su that said pivot axis extends generally along its lengt and a downwards extending generally vertical hydrofoi section and a further generally vertical hydrofoil sec tion and a further generally horizontal section whic is fully submerged for normal operation, wherein th herein above hydrofoil may be generally 'C shaped.

Further aspects of the invention relate to the retrac tion of hydrofoils for docking which has hitherto bee a problem. A hydrofoil described in the independen aspects four and five described above may be retracte by forwards or rearwards rotation about its pivota axis and in the case where the angle of attack is con trolled by an actuator said actuator may preferably b used also for retraction. Alternatively a cable may b used for retraction. This type of hydrofoil is prefera bly retracted such that the normally generally horizon tal section is well clear of the water surface to pre vent excessive drag or alternativaly a second pivo axis may be introduced close to the junction betwee the generally horizontal and the generally vertica sections and which is locked for normal foil-borne ope ration but which allows additional pivotal action fo retraction such that the angle of attack of the gene rally horizontal section remains sensibly constant. hydrofoil as described in the third independent aspec may have an additional pivot arranged close to the wa ter line which is locked for normal operation but abou which the hydrofoil may be pivoted for retraction. If cable is used for retraction in this case it may als serve to lock and release pivotal motion about sai additional pivot axis.

One hazard for hydrofoil craft of this nature is th potential for hign speed impact with floating debris such as logs. Whilst the relatively slender leadin edge of the hydrofoil will cut through minor debris provision of compliance in a direction parallel to the longitudinal axis of the craft is necessary to prevent, or minimise, structural damage to the craft and exces¬ sive accelerations which could result in injury to crew or passengers. Thus by incorporating some compliance into the actuator or any linkage connecting it to the hydrofoil, the hydrofoil will rotate about its pivot axis if the force acting on the actuator or the linkage as a result of such an impact is sufficiently great. Such compliance may be provided by such means as a spring -sr a pressure relief valve or accumulator.

As herein above described, mechanical surface sensor means of prior art have had forward projecting mecha¬ nisms which have extended the overall dimensions of the craft and have been liable to snag on other craft etc... Also, because they have extended a considerable way in front of the foil which they have controlled the longitudinal foil-base as a fraction of craft length has been smaller than is desirable. They have also pre¬ sented large surface areas which have tended to result in high drag, particularly in chop conditions. Thus according to a sixth independent aspect of the present invention any hydrofoil supported craft which comprises at least one hydrofoil which has a variable angle of attack and is preferably configurated to pro- vide similar amounts of vertical lift component in ei¬ ther the upwards or the downwards sense has an associa¬ ted surface sensing means comprising two leading arms which are pivotally attached to some fixed or mobile part of the craft towards their rear ends and which further comprises a trailing arm forming a downward ex¬ tension to said forward link. The lower end of said trailing link may form a surface-piercing hydrofoil or may be pivotally attached to such a foil in which latter case said surface-piercing foil will be pivotal- ly attached to the lower end of a second trailing arm which is pivotally attached to the lower leading arm at its upper end. The said surface-piercing hydrofoil is configured to ride along the water surface such as to alter the angle of attack of its associated hydrofoil as it changes its attitude relative to the craft. The surface sensing means so comprised is preferably contained within the contours of the craft in plan pro¬ jection for protection and the gain of the sub-system comprising the surface sensor means and its associated hydrofoil is preferably readily adjustable and may be adjusted by altering the length of said joining link. Said hydrofoil together with said surface sensing means is preferably configured for low combined drag and said surface-piercing hydrofoil of the surface sensing means is preferably of small area and the first trailing arm may be designed to cut through chop with low drag. The herein above described surface sensing means may be linked to a hydrofoil as described in the fourth inde¬ pendent aspect of this invention in which case a link may be pivotally attached to one of said leading arms at its upper end and to said generally horizontall pivoted hydrofoil at its lower end such that upwar motion of said leading arm or arms causes an increas in the angle of attack of said hydrofoil and vice-ver sa. In this case the rearward pivot of the leading ar to which said hydrofoil link is attached may be colli near with the pivotal axis for retraction of said hy drofoil such that the angle of attack of said hydrofoi is not materially changed on retraction. The herein above surface sensor means may also be cou pled to a hydrofoil as herein above described in th fifth independent aspect of this invention in whic case the lower leading arm will form a forward exten sion of a generally vertical hydrofoil section and th upper leading arm may include a generally downwards ex tending arm which locates in a track generally verti¬ cally disposed above or below the pivot axis of sai hydrofoil such as to support the vertical component of lift generated by said foil in either an upwards or downwards sense and said surface sensor means is arran ged such that the included angle between the forwar end of the upper leading arm and the joining link bet ween the forward ends of the two leading arms is suc that the combined effect of the moment generated by th hydrofoil about its pivotal axis and the vertical com ponent of lift it generates always produces a downwar thrust on said surface-piercing hydrofoil of the sur face sensing means. The said upper leading arm may b pivoted about a member which is pivoted about the gene- rally horizontal pivotal axis for retraction of the associated hydrofoil such that said member is locked i position for normal operation and is released for re¬ traction such that said hydrofoil retracts pivotall with its associated surface sensing means. A wind powered or assisted hydrofoil craft with t herein above described attributes will require a syst to control the various hydrofoils and wings. Larg craft will most probably require a fully automatic co trol system similar in functionality to that of a lar civil airliner.

Thus a control system for such a craft shall preferab provide continuous control of the craft, both prior lift-off and in the foil-borne mode, by sensing m tions, combining the motion signals with the manu pilot commands, and converting these into appropria control surface deflections such that the craft travel smoothly in the desired direction and at the desire speed and the craft is not at any time in danger o pitch-poling or rolling over or of being over-stresse due to excessive forces being generated by the wing o wings. In the foil-borne mode the control system shal also prevent the generally horizontal fully submerge foils from emerging from the water surface or the hul being impacted by waves.

A simpler control system for small leisure craft o other less demanding applications may be split suc that water surface sensing means mechanically linked t the generally hozirontal pivoted hydrofoil section such as to control their angle of attack are provide as heretofore described to control craft ride height, pitch, and roll, whilst an electronic system may pro vide foil immersion protection direction of motion, tack selection, speed control , and stress control. Th wing flap and wing tip rotation functions may be combi ned to minimise control forces and to enable a singl actuator to be used for this purpose, and a secondar actuator may be provided to control the ratio betwee flap deflection and wing tip rotation. According to a seventh independent aspect of the pre¬ sent invention any wind powered or assisted craft o vehicle comprising at least one upwards extending win pivoted about a generally vertical axis and means to control the angle of attack of said wing or wings and further comprising steering means in which the angle of attack of the wing or wings is controlled by a pedal similar to an accelerator pedal of a motor vehicle and where the steering means includes a steering wheel si- milar to that of a motor vehicle and which may further comprise a control similar to a gear lever of a motor vehicle to select the direction of motion in the fore and aft sense or may comprise a switch to select port of starboard tack and may comprise an electronic wing controller which processes any input signals from said accelerator pedal or from said direction control lever or from said tack control switch and which converts said signals into suitable outputs for any wing actua¬ tors, and which may comprise additional control means which .in the case of a hydrofoil water craft senses potential lift-out of the windward lift producing hy¬ drofoil and in the case of water craft not being hydro¬ foil craft or in the case of land or ice craft or vehi¬ cles senses possible capsize and which applies a signal to the electronic wing controller such that the lift generated by any controlled vertically extending wing is reduced and which may comprise stress control means such that if any transducer positioned at any part of the craft indicates that that part of the craft or ve- hide has reached or is about to reach a pre-determined level of stress or strain or deflection a signal is applied to the electronic wing controller such that the lift of any controlled vertically extending wing is reduced. The objects, attributes and features of all aspects o the invention will be more readily apparent from evaluation of the following detail discussion of a embodiment taken in conjunction with the accompanyin drawings which illustrate by way of example the princi¬ ples of the invention, in which :

- figure 1 is an isometric view of the craft with its hydrofoils lowered in the normal operational position ;

- figure 2 is a front view of the craft with its hydro- foils lowered in the normal operational position ;

- figure 3 is an isometric view of the craft with its hydrofoils lowered for normal operation ;

- figure 4 is a side view of the craft with its hydro¬ foils lowered ; - figure 5 is a front view of the craft with its hydro¬ foils raised for docking ;

- figure 6 is an isometric view of the craft with its laterall hull extensions and their attached hydrofoils folded inwards and the wings stowed in the hull for transport ;

- figure 7 is a side view of the front hydrofoil and its attached surface sensor ;

- figure 8 is a view of the front hydrofoil retracted for docking or transport ; - figure 9 is a side view of an alternative layout of the front hydrofoil ;

- figure 10 is a side view of the alternative front hydrofoil layout with the hydrofoil retracted for doc¬ king or transport ; - figure 11 is a side view of a rear hydrofoil and its associated surface sensor ;

- figure 12 is a partial view of a rear hydrofoil and its associated surface sensor ;

- figure 13 is a block diagram of the wing control sys- tern ; and - figure 14 is a diagram of the wing flap and wing ti actuator mechanism.

A craft K comprises a body L on top of which is mounte wind powered aerofoil propulsion means M and on th bottom of which is mounted hydrofoil means H. The craf K has a transverse (pitch) axis ZZ, a longitudina (roll) axis XX, and a vertical (yaw) axis YY. The body L comprises a hull 1 and a cockpit 2. The hul is in the form of a slender delta lateral which ha extensions 101, 102 at its aft end to support the rea hydrofoil means H and to provide buoyancy to stabilis the craft K at low speeds. The lower surface 104 of th lateral extensions 101, 102 form slender hydrodynami lifting surfaces. The forward end of the hull 1 i broadened to provide protection for the forward hydro foil means H and also to provide a suitable hydrodyna¬ mic surface 103 when the craft is hull-borne and pit¬ ched forward and a tunnel 105. The underside of the rear of the hull 1 has a hinged panel 106 arrange above the static water line SWL. The lateral extensio 101, 102 are mounted on hinges 107 and are retained i the operating position by a clamp 108. The cockpit is enveloped by a windscreen 201 and is equipped with a steering wheel 202, an accelerator pedal 203, and a direction controller 204a, tack selector 204b and wing variator 204c which are combined into a single control 204.

The aerofoil means M comprises two upwards extending wings 3 mounted to a domed disk 31. Each of the wings has an upper and a lower trailing edge flap 4a, 4b, and a detachable tip 5 rotatable about an axis GG. The aerofoil means is freely pivoted about the vertically inclined axis Y'Y'. The wings 3 are detachable from the domed disk 31 at 301. The hydrofoil means H comprises a starboard hydrofoil 19 projecting down from beneath the starboard blank of the hull 1, a port hydrofoil 20 projecting down from beneath the port flank of the hull 1 and a forward hy- drofoil 21 projecting down from the front of the hull 1.

Each of the port and starboard hydrofoils 19, 20 com¬ prises a horizontally extending section 193, 203 pivo¬ ted to the lateral hull extensions 101, 102 to which a vertically extending, water-piercing section 191, 201 is connected and a submerged horizontally inclined sec¬ tion 192, 202 connected to the bottom of the vertical section. The hydrofoils 19, 20 are pivotally mounted on the body L about collinear pitch axes E,E. The rear hydrofoils 19, 20 may be rotated through approximately one hundred and eighty degrees rearwards about the pitch axis EE such that the normally horizontal sec¬ tions 192, 202 are lifted clear of the water for opera¬ tion in shallow water. The forward hydrofoil 21 comprises a vertical water- piercing section 211 and a submerged horizontal section 212. The top of the water-piercing section 211 is pivo¬ tally mounted in a trunnion 22 about pitch axis DD. The trunnion 22 is pivotally mounted to the forward end of the hull 1 such as to permit rotation about a vertical¬ ly inclined axis CC. The forward hydrofoil may be rota¬ ted through approximately ninety degrees rearwards about pitch axis DD for operation in shallow water, whereby the leading edge of the normally vertical sec- tion remains partially submerged to retain steerage.

Figure 7 shows a layout of the front hydrofoil 21 with its associated surface sensor 40. A downwards extending fin 213 is attached to the lift hydrofoil 212 which is pivoted at F to the vertical surface-piercing hydrofoil 211 which is pivotally attached at D to a yoke 22 which is pivoted to the hull 1 about axis CC. The hydrofoi 211 is maintained in its lowered position by tension i cable 215 which is attached to the vertical hydrofoi

211 in front of its pivot D such that a forwards an upwards extension of foil 211 abuts the front face o the yoke 22 at H. The other end of the tension cabl 215 is operated by a lever (not shown) via a compres sion spring (not shown) . A small surface-piercing hy drofoil 401 is pivotally attached to the lower end of trailing arm 402, the upper end of which is pivotall attached to a leading arm 404 the after end of which i also pivoted at D. A link 216 is articulated at P an is pivotally attached to a rearward and upward exten¬ sion of leading arm 404 at its upper end and is pivo- tally attached to the lift hydrofoil 212 at its lower end. The upper portion 216a of link 216 runs in a guide 217 fixed to the vertical foil 211. Link 216 is free to move in a passage 211' within the vertical foil 211. A 'T' member 405 is attached to a slot in an upwards ex- tension 402a of trailing arm 402 and is pivotally atta¬ ched to the front end of a second leading arm 406. The rear end of the leading arm 406 is pivotally attached to the yoke 22 above the pivot D. A second trailing arm 403 is pivotally attached at its upper end to the lea- ding arm 404 and at its lower end to the surface-pier¬ cing hydrofoil 401.

The above described mechanism is arranged such that generally upward motion of the surface-piercing hydro¬ foil 401 causes a downwards thrust in the link 216 such that the angle of attack of the lift hydrofoil 212 is increased such as to tend to lift the front of the craft. The relation between the movement of the sur¬ face-piercing foil 401 and the rotation of hydrofoil

212 can be adjusted by movement of the T member 405 in the slot in the extension 402a of the trailing arm 402. A landing wheel 218 is pivotally attached to the verti¬ cal hydrofoil 211 such that it is maintained above the upper extent DWL' of the dynamic water line DWL. Figure 8 shows the hydrofoil 21 in the raised position wherein cable 215 has been slackened and cable 214 which is attached to hydrofoil 211 behind the pivot at D has been tensioned by means of a lever (not shown) such that the sloping rear upper face of the hydrofoil 211 abuts the rearward face of the yoke 22 at H'. The vertical hydrofoil 211 is maintained generally below the static water line SWL and may be rotated about axis CC for steering. The hydrofoil 21 is arranged such that it lifts into the tunnel 105 of the hull 1. In an alternative version shown in figure 9 the lowe- ring cable 215 has an outer sheath 215a which abuts the leading arm 404 locking it to the vertical hydrofoil 211 in the lowered position and the lift hydrofoil 212 is pivoted to the lower end of the vertical hydrofoil

211 at P. The cable 215 is extended downwards and fixed to the lift hydrofoil 212 such that it abuts the lower face of the vertical hydrofoil 211. The leading arm 404, the vertical hydrofoil 211 and the lift hydrofoil

212 thus pivot about D as a unity in this case. As pre¬ viously the cable 215 is slackened and the cable 214 is tensioned for retraction. To provide the necessary reaction to prevent reversal of the control moment a downwards extension 406a of the leading arm 406 has a cam follower 407 at its lower end which locates in a track 219 in the vertical hydrofoil 211 above pivot D. The included angle between the leading arm 406 and the upward extension 402a of the trailing arm 402 is arran¬ ged such that a downward thrust is maintained on the surface-piercing hydrofoil 401 whether the angle of attack of hydrofoil 212 is positive or negative. Figure 11 et 12 show a layout of one of the rear hy¬ drofoils 20 with its associated surface sensor 50. The hydrofoil 20 is pivoted about axis EE and has bearings El, E2 located in the hull extension 102. The bearing El adjacent to the hydrofoil is located fore and aft but is unrestrained vertically. E2 is a spherical bea¬ ring. When the hydrofoil 20 is in its lowered position a tension cable 225 maintains a pivoted member 508 which is separately pivoted about axis EE against a stop S2 fixed to the lateral hull extension 102. The other end of the tension cable 225 is operated by a lever (not shown) via a compression spring (not shown) . A small surface-piercing hydrofoil 501 is pivotally attached to the lower end of a trailing arm 502, the upper end of which is pivotally attached to the inboard section of the laterally extending upper hydrofoil 203a of hydrofoil 20 at some distance in front of the axis EE. A 'T' member 505 is adjustably attached to a slot in an upwards extension 502a of trailing arm 502 and is pivotally attached to the front end of a second leading arm 506. The rear end of the leading arm 506 is pivo¬ tally attached to the pivoted member 508 above the pi¬ vot axis EE. To provide the necessary reaction to pre¬ vent reversal of the control moment a downwards exten- sion 506a of the leading arm 506 has a cam follower 507 at its lower end which locates in a track 229 in the hydrofoil 20 above the pivot axis EE. The included an¬ gle between the leading arm 506 and the upward exten¬ sion 502a of the trailing arm 502 is arranged such that a downward thrust is maintained on the surface-piercing hydrofoil 501 whether the angle of attack of hydrofoil 202 is positive or negative. A landing wheel 238 is pivotally attached to the hydrofoil 20 and this toge¬ ther with the pivoted member 508 acts as a keel when the hydrofoil 20 is retracted. A tension cable 224 which is attached to the pivoted member 508 is provided for retraction and is operated by a lever (not shown) . The hydrofoil 20 is retracted by slackening the tension cable 225 and tensioning the cable 224. The pivoted member acts against the limit stop S3 fixed to the hy¬ drofoil 20 such that the hydrofoil 20 and the pivoted member 508 are rotated rearwards together. To lower the hydrofoil cable 224 is slackened and cable 225 is ten¬ sioned such that it abuts the limit stop S4 fixed to the hydrofoil 20 such that both rotate forwards toge¬ ther.

Figure 14 shows the mechanisms for actuating the wing flaps and tips. An actuator 14 is pivotally attached at one end to the disk 31 which is pivotally attached to the hull 1 at Y' and to which the wings 3 are attached and is pivotally attached at its other end to a lever 60 fixed to the lower end of one of the flaps 4b. Ano¬ ther lever 61 is fixed to the lower end of the other flap 4b and the two levers 60, 61 are pivotally connec- ted by a rod 62 and are angled relative to flaps 4b to which they are respectively attached such that rotation of either flap about its pivot FP results in a desired differential rotation of the other flap. Both flaps 4a, 4b are arranged to be deflected by the same amount and a torque transmitting coupling is arranged between them and both flaps are torsionally stiff such that any ro¬ tation of the bottom of one of the lower flaps 4b re¬ sults in a similar rotation at the top of the upper flap 4b fitted to the same wing. Forward projecting slotted levers 63a, 63b are connected to the top of the upper flaps 4a and are aligned with their chordwise axes.

Further slotted levers 64a, 64b are fixed to the pivot axes GG of the two wing tips and are directed rearwards along the chordise axes of the wing tips 5. Actuators 15a, 15b are pivotally attached to the forward facing levers 63a, 63b at the flap pivot axis FP and pins 65a, 65b fixed to the other end of these actuators engage in the slots in the levers 63a, 63b and 64a, 64b such that by extending and retracting the actuators 15a and 15b the ratio between the flap deflection of a wing 3 and the rotation of the tip 5 of the same wing is varied. The basic control system for the craft K is shown in the form of a simplified schematic circuit diagram in figure 13 in which signals from the direction control 204a situated in the cockpit 2 are applied to the wing incidence and flap controller 39, to control the direc¬ tion and amount of deflection of the flaps 4, 4a and the rotation for the wing tips 5. The direction control 204a has forward, neutral and reverse positions.

An accelerator 203 situated in the cockpit 2 allows the pilot to control the speed of the craft K by altering the angle of attack of the wings 3 and consequently the driving force generated. Signals from the accelerator 203, and the combined control 204 are applied to the wing incidence and flap controller 39 which processes the input signals including feed-back signals from the actuators 14 and wing tip ratio actuators 15a, 15b such that the craft responds in the required manner. The force transducer 45 measures the bending strain at the root of one of the wings 3 and applies a signal to the wing flap and incidence controller 39 such that if the gauged wing reaches its maximum level of drive the angle of attack of the wings 3 is limited by changing the angle of attack of the wing tips 5 and, if necessary, the deflection of flaps 4a, 4b. Signals from position transducers 43, 44 connected to the starboard and port surface-piercing foil means 50 enable the wing incidence and flap controller 39 to determine whether the horizontal sections 192, 202 of the rear hydrofoils 19, 20 are about to lift out of the water and in which case to limit the angle of attack of the wing 3 as above.

Whilst a particular form of the invention has been illustrated and described, it will be clear to those skilled in the art that modifications can be made wi¬ thout departing from the generality of the invention and it is accordingly not intended that the scope of the invention be limited except as by the following claims.

Claims

CLAIMS 1. A wind powered or assisted hydrofoil craf ^* comprising aerofoil means, hydrofoil means, hull mean and control means in which : - the aerofoil means provides a driving force to prope the craft,

- the hydrofoil means provides vertical lifting forces both to support the weight of the craft and any verti¬ cal component of lift created by the aerofoil means and the hull means and to provide stabilizing moments to balance the craft about its roll and pitch axes and to provide horizontal forces both to balance components of the lift and drag forces in a direction parallel to the transverse axis of the craft created by the aerofoil means and the hull means and to provide a stabilizing moment to balance the craft about its yaw axis and steering means,

- the hull means provides the balancing vertical lif¬ ting forces and moments about the craft's pitch and roll axes which the hydrofoil means is unable to pro¬ vide due to an insufficiency of speed of the craft through the water and provides a cockpit for the crew, and

- the control means provides means for steering the craft, means for controlling the motion of the craft about its roll and pitch axes, and for controlling the height of the craft above the water surface and means for controlling the aerofoil means, and in which :

- the aerofoil means comprises at least one upwards extending wing of rigid or flexible construction

- the hydrofoil means comprises at least three hydro¬ foils arranged to provide both horizontal and vertical lift forces of which at least two are spaced about the longitudinal axis of the craft and of which at least one is spaced along the longitudinal axis of the craft relative to at least one other hydrofoil and which has means of adjusting its horizontal lift, and in which : - the hull means comprises one or more hulls or floats arranged along and about the pitch and roll axes of the craft such as to provide the necessary lift forces and righting moments about these axes and which further comprises means for connecting the hulls and floats, if more than one is provided, the hydrofoil means and the aerofoil means and for absorbing the forces generated by these means and controlling their deflections.

2. A craft as in claim 1 in which any hydrofoil is provided with means for adjusting its vertical lift by pivotal motion about a horizontal or horizontally inclined axis.

3. A craft as in claim 1 in which any hydrofoil having means to adjust its horizontal lift is pivoted about a vertical or vertically inclined axis.

4. A craft as in claim 1 in which :

- any hydrofoil is pivoted about a substantially verti- cal axis capable of providing both vertical and hori¬ zontal lift components situated close to the forward extremity of the craft and in which :

- a hydrofoil is pivoted about a substantially horizon¬ tal axis having a substantially vertical member and a substantially horizontal member orientable for positive or negative lift close to each of the lateral extremi¬ ties and the rear of the craft.

5. A craft as in claim 1 in which the hydrofoils disposed either side of the craft's longitudinal axis form a smooth downward-projecting extension to the hull means such as to form an end-plate thereby reducing aerodynamic drag.

6. A craft as in claim 1 in which the hydrofoil means are readily retractable for launching and opera- tion in shallow water.

7. A craft as in claims 1 and 6 in which the hydrofoil means remain sufficiently immersed when re¬ tracted to provide steering means and stabilisation about the craft's yaw axis.

8. A craft as in claims 1 and 6 which is equip¬ ped with wheels which lower when the hydrofoil means are retracted such as to facilitate launching.

9. A craft as in claims 1 and 8 in which the wheels are dimensioned such as to enable the craft to be operated on land and are detachable and may be re¬ placed by skids for operation on land or on ice.

10. A craft as in claim 1 in which the hull means is arranged such that in plan projection any hydrofoil or any associated surface sensor or control means is contained within the contours of the hull means and is thereby afforded protection.

11. A craft as in claim 1 in which the aerofoil means is positioned towards the rear of the craft.

12. A craft as in claim 11 in which the aerofoil means are rigid and pivoting wings to improve aerodyna¬ mic and structural efficiency, having smooth external surfaces with an absence of external bracing.

13. A craft as in claim l which has a cockpit placed towards the front of the craft giving the crew unhampered forward visibility.

14. A craft as in claim 1 in which the aerofoil means are abutted to the hull means in a manner as to provide a smooth transition between the two means such as to increase efficiency and reduce aerodynamic drag.

15. A craft as in claim 4 in which the hull pre¬ sents three slender hydrodynamic lifting surfaces of moderate aspect ratio the centres of lift of which cor¬ respond approximately to the centres of lift of the three generally horizontal hydrofoils and which are presented at an angle to the water surface such as to create a minimum of drag at all attitudes of the craft prior to it becoming fully foil-borne.

16. A craft as in any claims 1 to 15 in which the hull means is extended in its width such that the late- rally spaced hydrofoils are directly attached to it.

17. A craft as in any claims 1 to 16 in which in plan view the hull means forms a slender delta in which the apex of the delta being at the front of the craft is extended in its width.

18. A craft as in claim 15 in which the forward hydrodynamic lift surface is divided into two surfaces situated either side of the longitudinal axis of the craft such as to create a central tunnel into which the forward hydrofoil can be retracted and permitting rota- tion of said hydrofoil about its generally vertical axis for steerage in the retracted state.

19. A craft as in claims 15 or 18 in which the three lifting surfaces are merged into a single surface of moderate aspect ratio the lift centre of which moves along both the longitudinal and transverse axes of the craft as required to balance the forces acting on the craft or generated by it.

20. A craft as in any claims 1 to 19 in which the longitudinal sections are aerodynamically shaped to reduce drag and are generally thick to give sufficient structural stiffness to withstand the imposed aerodyna¬ mic and hydrodynamic loads without external bracing.

21. A craft as in any claims 1 to 20 in which any sidewards extending hull extension is hinged about an axis generally parallel to the craft's longitudinal axis such that it can be folded, together with any hy¬ drofoil fitted to it, for transport or storage.

22. A craft as in any claims 1 to 21 in which the wings are demountable and can be stowed in the hull for transport or storage.

23. Any wind powered or assisted craft or vehicl with aerofoil means in which the aerofoil means compri ses at least one upwardly extending wing which is gene rally tapered along its length such that the chord a its root is greater than the chord at its tip and i which any such wing is arranged with at least one trai ling edge flap which is also tapered along its lengt having a fractional chord at its root greater than th fractional chord at its tip.

24. A craft as in claim 23 in which any upwardl extending wing is generally boomerang shaped.

25. A craft as in claims 23 or 24 in which an upwardly extending wing has an additional pivoted ti section which can be rotated such as to operate at a generally different angle of incidence to the main wing section.

26. A craft as in claims 23 or 24 and claim 25 in which any wing can be twisted along its length such that its upper end is twisted relative to its lower end by the amount by which the tip section is rotated.

27. A craft as in any claims 1 to 26 in which any upwards extending wing is pivoted about a vertical or vertically inclined axis in which means is provided to adjust the angle of attack of the wing by rotating it about said pivot axis such that the lift generated by the wing is also adjusted.

28. A craft as in any claims 1 to 27 in which any upwards extending wing is pivoted about an axis exten¬ ding along its length.

29. A craft as in any claims 1 to 27 having a multiplcity of upwards extending wings which are all pivoted about a single vertical or vertically inclined axis as a group.

30. A craft as in any claims l to 27 having a multiplicity of upwards extending wings in which groups of said wings are pivoted about vertical, or verticall inclined axes.

31. A craft as in any claims 1 to 30 in which the base of any upwards extending wing is positioned at a small distance from the water surface in relation to its length such that its effective ratio is substan¬ tially increased due to the mirror plane provided by the water surface.

32. A craft as in any claims 1 to 28 in which the surface of the hull means which abuts any upwards ex¬ tending wing is extended to act as an end plate for the wing in order to increase its effective aspect ratio.

33. A craft as in any claims 1 to 28 in which the surface of the hull means about which any upwards ex- tending wing sweeps as it rotates about its pivotal axis is a plane surface normal to said axis.

34. A craft as in any claims 1 to 31 in which the base of any wing is fixed to a planar or domed disk pivoted about a generally vertical axis.

35. A craft as in any claims 1 to 34 in which at least one upwards extending wing is positioned such that it is generally vertical.

36. A craft as in claims 25 or 26 and claims 27 or 28 in which the pivoted tip section of any wing is swept forwards or rearwards such that the angle of at¬ tack of the wing is controlled by rotation of the tip section by altering the balance about the pivotal axis of the wing.

37. A craft as in any claims l to 28 in which the angle of attack of any pivoted wing is controlled by the angle of attack of at least one control aerofoil which is pivotally attached to one or more arms exten¬ ding rearwards from said wing such that said wing toge¬ ther with its associated arm or arms and control aero- foil or aerofoils is free to rotate as an entity about its pivotal axis.

38. A craft as in any claims 1 to 27 and claims 29 or 30 in which the angle of attack of any group of pivoted wings is controlled by the angle of attack of at least one control aerofoil which is pivotally atta¬ ched to one or more arms extending rearwards from the group of wings being free to rotate together with its associated arm or arms and control aerofoil or aerofoils as an entity about the pivotal axis of the group of wings.

39. A craft as in claim 36 and claims 29 or 30 in which the angle of attack of any group of pivoted wings is controlled by the angle of attack of at least one rotatable wing tip by altering the balance about the pivotal axis of the group of wings which is arranged to rotate freely as an entity.

40. A craft according to any one of the preceding claims 36 to 39 in which the angular position of any wing or group of wings is set by an actuator, the ba¬ lancing moment created by actuation of any wing tip or control aerofoil effectively reducing the control mo¬ ment supplied by the said actuator.

41. A craft as in claim 26 in which any upwards extending wing which is twisted about its lengthwise axis is divided into at least two sections along its length and has means to rotate each section about the lengthwise axis of the wing such that by rotating each section to differing extents the wing is effectively twisted though each section may remain untwisted.

42. A craft as in claims 23 or 24 having two or more upwardly extending wings wherein the trailing edge flaps of any one wing are actuated differentially with respect to the trailing edge flaps of any other wing.

43. A craft as in claims 25 or 26 having two or more upwardly extending wings wherein the pivoted tip section of any wing is rotated differentially with res¬ pect to the tip section of any other wing.

44. A craft as in claims 1 to 43 in which any wing is buoyant and in which the centres of buoyancy of the wing means and any other immersed part of the craft in the capsized state are such as to provide sufficient righting moment to right the craft automatically.

45. A craft as in claims 1 to 43 in which any wing is buoyant and in which means is provided to ro¬ tate any wing or group of wings such that a capsized craft may be easily righted.

46. A craft as in claims 1 to 45 having at least two wings in which any pair of wings are arranged such that they splay outwards one to another being pitched more closely together at their lower than at their up¬ per ends.

47. A craft as in claims l to 22 or in claims 25 or 26 having at least two wings in which the tips of any pair of wings are arranged such that they splay inwards one to another being pitched more closely toge¬ ther at their upper than their lower ends.

48. A craft as in claim 23 in which any upwardly extending wing has more than one flap and in which at least one flap can be deflected differentially with respect to another flap on the same wing.

49. Any wind powered or assisted hydrofoil craft with at least one hydrofoil in which any hydrofoil com- prising a vertical or vertically inclined water-pier¬ cing section and a horizontal or horizontally inclined normally submerged section has a horizontal or horizon¬ tally inclined pivotal axis substantially parallel to the transverse axis of the craft arranged such that the angle of attack of the horizontal or horizontally in- clined section and consequently its lift may be adjus¬ ted by rotating the hydrofoil about its pivotal axis in a manner which enables the hydrofoil to develop similar values of lift in the upwards and the downwards sense.

50. A craft as in claim 49 in which the horizon¬ tal or horizontally inclined section of any hydrofoil having a vertical or vertically inclined section and a horizontal or horizontally inclined section is pivotal¬ ly attached to the lower end of the vertical or verti- cally inclined section.

51. A craft as in claim 49 in which the horizon¬ tal or horizontally inclined pivotal axis is arranged such that it is above the water surface for normal foil-borne operation such that both the horizontal or horizontally inclined section and the vertical or ver¬ tically inclined section rotate about the pivot axis as a unity.

52. Any hydrofoil supported craft which comprises a hydrofoil pivoted about a horizontal or horizontally inclined axis close to the static water line of the craft and in which the hydrofoil comprises a horizontal or horizontally inclined section arranged such that it provides additional lift during hull-borne operation and such that it is above the water surface for normal foil-borne operation and a downwards extending vertical or vertically inclined section and a further horizontal or horizontally inclined section which is fully submer¬ ged for normal operation.

53. A craft as in claim 52 in which the two hori- zontal or horizontally inclined sections and the verti¬ cal or vertically inclined section form a generally 'C shaped entity.

54. Any hydrofoil supported craft in which any hydrofoil includes a horizontal or horizontally incli- ned hydrofoil section pivotally attached to the lower end of any vertical or vertically inclined hydrofoi section in which its pivotal axis is arranged slightl behind its centre of lift and to which is attached downward projecting fin and is arranged such that fo forward motion the sum of the moment created by th vertical lift component generated by said hydrofoi section together with the moment created by the dra generated by said fin about the pivot axis of said hy drofoil section always acts in the same sense whethe the said vertical lift component be in an upward or downward sense.

55. Any hydrofoil supported craft in which - any hydrofoil comprising a vertical or vertically inclined water-piercing section and a normally submer- ged horizontal or horizontally inclined section can be rotated about a horizontal or horizontally inclined pivotal axis situated above the normal water level for foil-borne operation such as to vary the vertical lift component it generates and - in which such pivotal axis is largely unconstrained for translational movement in a generally vertical sense and

- in which the vertical lift component generated by said hydrofoil is largely resisted by part of the craft which is translationally mobile in a generally horizon¬ tal sense relative to said pivotal axis such that the moment required by any actuator or control mechanism to rotate said hydrofoil about said pivot axis or to main¬ tain it in position is substantially reduced.

56. A craft as in claims 49, 51, 52, 53 or 55 in which any hydrofoil having a horizontal or horizontally inclined pivotal axis may be pivotally retracted for¬ wards or rearwards about its axis such that the draft is substantially reduced for docking or operation in shallow water.

57. A craft as in claims 49, 50 or 51 which is arranged with an additional pivot axis close to or above the static water-line and which is locked during normal foil-borne operation such that the hydrofoil may be pivoted forwards or rearwards about this additional pivot axis enabling a substantial reduction in draft for docking or operation in shallow water.

58. A craft as in claims 52, 53, 54 or 55 which is arranged with an additional pivot axis close to the intersection of the horizontal or horizontally inclined and the vertical or vertically inclined foil sections and which is locked during normal foil-borne operation such that the hydrofoil may be pivoted forwards or rearwards about its horizontal or horizontally inclined pivot axis enabling a substantial reduction in draft for docking or operation in shallow water whilst the horizontal or horizontally inclined foil section is pivoted about the herein above described additional pivot axis such that its angle of incidence remains largely unchanged.

59. A craft as in claim 58 in which the angle of attack of the horizontal or horizontally inclined sec¬ tion is largely unchanged during rotational retraction of the hydrofoil about its additional pivotal axis.

60. A craft as in claims 52, 53, 54 or 55 in which any hydrofoil may be retracted about its pivotal axis such that the hydrofoil is substantially clear of the water.

61. A craft as in claims 49 to 60 in which cable means are provided to retract about its pivotal or its additional pivotal axis.

62. A craft as in claims 49 to 60 in which cable means are provided to lower any hydrofoil about its pivotal or its additional pivotal axis and to lock said hydrofoil about such additional pivotal axis if saidhy- drofoil is so equipped.

63. A craft as in any of the claims 49, 51, 52, 53, 55, 56, 58 and 60 in which any hydrofoil with a vertical or a vertically inclined section and a hori¬ zontal or horizontally inclined section and which is pivoted about a horizontal or horizontally inclined axis has an actuator for adjusting the angle of attack and uses the same actuator to retract said hydrofoil.

64. A craft as in claims 56, 57, 58, 59 and 60 in which any hydraulic or pneumatic actuator used to re¬ tract any hydrofoil has at least one pressure relief valve or accumulator in its control circuit for the purpose of providing compliance such that any such hy- drofoil when impacted by a body may rotate rearwards against the compliant force provided by the control circuit to relieve the impact.

65. A craft as in claims 49 to 63 in which any hydrofoil additionally comprises spring means such that if impacted by a body it may rotate rearwards about its axis for retraction in a compliant manner.

66. Any hydrofoil supported craft which comprises at least one hydrofoil which comprises a horizontal or horizontally inclined section and further comprises a horizontal or horizontally inclined pivot axis and which is connected to surface sensing means comprising a mechanism which determines the height of some point of the craft relative to the water surface and provides a controlling force to adjust the upward or downward lift component generated by said hydrofoil such as to tend to maintain any part of the craft at a controlled height relative to the water surface and in which : - said surface sensing means includes two leading arms each of which is pivotally attached towards its rear end to some fixed or mobile part of the craft and is further pivotally attached to a joining link toward its forward end so as to form a parallelogram and i which : a downwards extension to said joining link forms a trailing arm.

67. A craft as in claims 1 to 66 in which any hy¬ drofoil together with the surface sensing means to which it is connected is arranged such that it can pro¬ vide similar amounts of lift in both an upwards and a downwards sense.

68. A craft as in claims 1 to 67 in which any surface sensing means is a compact arrangement and in plan projection is contained within the contours of the craft such that it is thereby afforded protection.

69. A craft as in claims 1 to 67 which incorpora¬ tes means in which the gain of any system comprising a hydrofoil and its associated surface sensor means can be readily adjusted such as to adapt the dynamic beha¬ viour of the craft to local wind and sea-state condi- tions.

70. A craft as in claims 49, 50 or 51 and claim 66 comprising at least one hydrofoil linked to surface sensor means which includes a pair of leading arms and in which one of the leading arms is linked to said ho- rizontal or horizontally inclined hydrofoil section such that upwards rotational movement of the forward ends of said leading arm causes an increase in the an¬ gle of attack (which may be a decrease in the negative angle of attack) of said hydrofoil section, and such that upwards rotation of said leading arm has the re¬ verse effect.

71. A craft as in claim 70 in which the rear pi¬ votal axis of the trailing arm to which said horizontal or horizontally inclined hydrofoil section is linked is susbstantially collinear with the pivotal axis for re- traction of the hydrofoil such that if said hydrofoi is retracted the angle of attack of said horizontal o horizontally inclined hydrofoil section is not substan tially altered.

72. A craft as in claims 52, 53, 54 or 55 an claim 66 comprising at least one hydrofoil linked t surface sensor means which includes a pair of leadin arms such that the lower leading arm is formed by a forward extension of a vertical or vertically inclined hydrofoil section.

73 A craft as in claim 66 and claims 70 or 72 in which said trailing arm comprises a small surface pier¬ cing hydrofoil at its lower end such that a movement of said trailing arm caused by a change in the lift gene- rated by said surface piercing hydrofoil as it rides along the surface of the water as a result of some change in the craft's attitude of wave motion, causes rotational motion of the lower leading arm thereby al¬ tering the angle of attack of the horizontal or hori- zontally inclined foil section to which it is connec¬ ted.

74. A craft as in claim 73 in which said trailing arm is shaped to provide limited hydrodynamic and buoyant lift and to generate low drag when immersed.

75. A craft generally as in claim 73 in which said trailing arm is pivotally attached to a small sur¬ face piercing hydrofoil at its lower end and in which a second trailing arm is pivotally attached to the lower leading arm at its upper end and to said surface-pier- cing hydrofoil at its lower end such that the two trai¬ ling arms generally form a parallelogram and such that the angle of attack of said surface piercing hydrofoil remains sensibly constant or is controlled to vary in a desirable manner.

76. A craft as in claim 75 in which said trailin arms are shaped to provide limited buoyant lift and t generate low drag when immersed.

77. A craft as in claims 66 and 69 in which th gain is altered by variation of the length of the joi ning link connecting the forward ends of the leadin arms.

78. A craft as in claim 55 and any of claims 73, 74, 75, 76and 77 in which a generally vertical exten sion of the upper leading arm locates in a track atta ched to the hydrofoil generally above or below its ho rizontal or horizontally pivotal axis such that sai extension supports the generally vertical lift compo¬ nent generated by the hydrofoil in either an upwards or a downwards sense and is arranged such that the inclu¬ ded angle between the forward end of the upper leading arm and the link between the forward ends of the two leading arms is such that the combined effect of the moment generated by the hydrofoil about its pivotal axis and the vertical component of lift it generates always produces a downward thrust on said surface-pier¬ cing hydrofoil of said surface sensor means.

79. A craft as in claim 78 in which said upper leading arm is pivotally attached to a member which is pivoted about the horizontal or horizontally inclined pivotal axis of the associated hydrofoil such that for normal operation said member is locked in position and is released for retraction such that said hydrofoil retracts pivotally with its associated surface sensing means.

80. Any wind powered or assisted craft or vehicle comprising at least one upwards extending wing pivoted about a vertical or vertically inclined axis and means to control the angle of attack of said wing or wings and further comprising steering means in which the an- gle of attack of the wing or wings is controlled by a pedal similar to an accelerator pedal of a motor vehi¬ cle and the steering means includes a steering wheel similar to that of a motor wehicle.

81. A craft as in claim 80 in which the means for controlling the direction of motion of the craft in the fore and aft sense includes a control similar to the gear selector of a motor vehicle.

82. A craft as in claims 80 and 81 which compri- ses at least one hydrofoil which has means to control its lift and which has additional control means such that if the horizontal or horizontally inclined section of any hydrofoil approaches the surface of the water too closely such that it is in danger of emerging from the water the angle of attack of any upwards extending wing is adjusted such as to reduce the downwards lift component required to be produced by that hydrofoil section.

83. A craft as in claim 80 or 81 which has addi- tional control means such that when being used on land or ice and any wheel or skid is in danger of lifting more than a specified amount from the surface or alter¬ natively the craft is in danger of exceeding a pre-de- termined roll or pitch angle the angle of attack of any upwards extending wing is adjusted such as to reduce the lift produced by any upwards wing such as to stabi¬ lise the craft.

84. A craft as in any of the preceding claims 80 to 83 which has additional control means such that if any transducer positioned at any part of the craft pro¬ duces a signal which indicates that the level of stress or strain or the load being carried by that part of the craft is above a pre-determined value the angle of at¬ tack of any upwards extending wing is adjusted such as to restore the value of the stress, strain, or load in that part of the craft to the pre-determined level as maximum.

85. A craft as in any of the preceding claims 8 to 84 which comprises a switch to select port or star board tack.

86. A craft as in any of the preceding claims to 85 which as at least one upwards extending wing an of which comprises at least one trailing edge flap an a pivoted tip section as a single actuator to contro both the deflection of said trailing edge flap or flap and the rotation of said tip or tips.

87. A craft as in claim 86 in which the rati between flap deflection and the rotation of the pivote tip section of any wing is variable and is controlle by an actuator.

88. A craft as in claims 86 or 87 in which fo any wing or group of wings, the control moments requi red to control the deflection of at least one flap an the control moment required to control at least on pivoted wing tip are combined in a manner as to reduc the overall control moment required.

89. A craft as in any of the preceding claims to 88 which has an electronic control system to control the sense and the amount of lift produced by any verti- cally inclined wing.

90. A craft as in any of the claims 1 to 65 or i any of the claims 80 to 89 which has an automatic con¬ trol system providing continuous control of the craft both prior to lift-off and in the foil-borne mode by sensing motions and combining the motion signals with the manual pilot commands and converting these into appropriate control surface deflections such that the craft travels smoothly in the desired direction and the desired speed and such that it is not at any time in danger of rolling over or pitch-poling or of being over-stressed due to excessive forces being generate by the aerofoil propulsion means and such that the wa ter surface in the foil-borne mode is prevented fro slamming against the hull means.