GB2152441A - Inflatable vessels and sails - Google Patents

Abstract

A vessel comprises a plurality of elongate inflatable hulls (b), each of which has a lower keel like formation defined by one or more internal dividers (f), (f'), extending from side to side between lower portions of the skin of the hull. A vessel is described with attachment means for a sail which extends longitudinally fore and aft to enable a variable point of attachment of a sail. A decking arranged to bridge a plurality of elongate inflatable hulls may be folded to form a portable container for the deflated hulls. A sail for the vessel comprises an inflatable envelope with a separately inflatable stiffening part. <IMAGE>

Description

SPECIFICATION Inflatable vessels and sails This invention relates to vessels and sails. it is an object of the invention to provide a method of manufacturing inflatable vessels and sails which cost less, weigh less and/or are more efficient hydrodynamically or aerodynamically.

It is also an object of this invention to provide a method of assembling and dismantling the vessels so that in the dismantled and packaged state the vessels are easily transportable.

At present it is possible to transport inflatable multihulls on a roofrack, but a further object of this invention is to be able not only to transport the vessels on a roofrack or in the boot of a car, but also to transport them by air at either no cost or at minimum extra cost.

It is a further object of this invention to be able to include within the package all sailing equipment, but also to manufacture the carrying case in such a way that it forms part of the structure of the vessel and yet enables the sailor to carry his/her personal clothing within it (i.e. it forms a valise).

It is a further object of this invention to provide a way of storing and transferring helium from the inflated hull whilst still retaining its shape.

A further object of this invention is to enable the sailor or boardsailor to operate the vessel without a rudder or centreboard and yet still achieve an upwind capability.

Accordingly, the invention provides a vessel comprising a twin hulled inflatable craft in the form of a double ended catamaran (or equal length proa) which is manufactured from a laminated fabric with the base material being one which has little or no stretch such as nylon and the inner material a heat sealable one such as polyurethane/ saran with possibly an outer coating of polyurethane on which to weld outer attachments.

The method of manufacture could be achieved either by high frequency welding conventional heat sealing or less expensively by the method described in my patent application No. 8309118 which enables me to heat seal in one operation whatever lengths of weld are required whether on a single, 2 dimensional or even 3 dimensional curve. Internal ribs can be welded by this method in as many numbers and with as much curvature as is required to create an efficient hydrodynamic shape.

However if the internal ribs are cut out from an elastic material such as polyurethane which is compatable with the hull material it is possible to heat seal a rib of equal width throughout parallel to the top of the hull and yet still obtain an efficient hydrodynamic shape merely by shaping the bottom of the hull correctly.

This efficiency is created because of the curved shape of the bottom of the inflated hull (which is relatively non elastic) and the distance of the rib from the bottom edge of the inflated hull at the centre compared to the distance of the rib at each end. The central section of the hull therefore expands more than at each end.

Surprisingly it has been found in both a 3.5 metre and 5.0 metre double ended catamaran or proa 2 ribs are so efficient that no centreboard is required making it possible to beach the craft without having to raise centreboards.

This also helps to reduce costs, weight and the normal restraints of design in an inflatable craft where the question of whether to use centreboards or daggerboards has long been a matter of discussion. The ribs can be heat sealed in position in one operation per side even if the length of weld is greater than 5.0 metres using the method described in my patent application No. 8309118, as can the two outer skins of the hull.

Correct tooling would enable each hull to be manufactured in 3 operations taking less than 10 minutes in total other than the insertion of inflation valve and grab handles, etc.

Both the elevated sail and the wing sail can be manufactured by the same method as described above although more ribs are required and it may be necessary in some cases to have both vertical and horizontal ribs to create the correct shape and/ or rigidity.

Surprisingly it has also been found that by altering the point of attachment (and therefore the centre of effort) of the wing sail or the elevated sail it is unnecessary to affix a rudder, again reducing cost, weight and particularly in inflated craft the problems of affixing a transom onto which the rudder must be attached.

However the advantages of this system of operating a wing sail or elevated sail apply to conventional monohulls as well as multihulls particularly when applied as an elevated jury rig.

It has been found that the type of material used for manufacturing the wing sail, elevated sails and hulls are crucial to the success of the above invention.

Weight of fabric as well as the correlation between peel and tear strength have to be taken into account as well as gas permeability, particularly where CO2 or helium are used.

It is important particularly in the hull and the wing mast section to have a high peel strength and fabrics have been laminated for me which have a peel strength of over 45 Ibs per inch to enable this invention to become feasable.

Although an example has been given of a polyurethane/nylon laminate being welded to a polyurethane rib any heat sealable material with similar characteristics could be used instead, but if a nonstretch material is used for the internal rib, it would have to be shaped to suit the hydrodynamic or aerodynamic requirements of that structure.

Secondly if the rib is non-stretch a greater indentation will occur along the structure at the weld point which could be detrimental to the laminar flow of air or water.

It has been found, however that an elevated sail constructed of polyurethane with polyurethane ribs running across the span (i.e. across the air flow) is remarkably stable and yet has a high lift to drag indicating that there may be small vortices created in the indentations which shed at the outer edge of the structure, but which create a smooth surface barrier over which the air can pass, much as the ground effect caused by 'skirts' in racing cars.

It has also been found that provided the outer material and the stretch material used in the rib has the elasticity of polyurethane and provided that the thickness of stretch material does not have to be such that the elasticity is negated without over pressurising the structure it is possible to obtain a comparatively smooth outer surface with only very slight indentations at the weld point The invention does not have to be manufactured by conventional gluing and taping methods and therefore is comparatively inexpensive and quick to manufacture. It is also efficient as to upwind capability without a centreboard or daggerboards and does not need a rudder to tack (or gybe in the case of an elevated sail system) and is easily transportable.

The method of propelling the vessel can be by means of an elevated sail as described above and in my patent applications Nos. 8031834 and 8309118 or by means of a wing sail as described above, or a combination of the two which is used as a conventional sail as well as an elevated sail.

One of the main advantages of an inflated wing sail as opposed to a rigid wing sail is its ability to be warped which makes it possible by way of example to attach the sail to the leeward hull and obtain an upward lifting force much as is achieved by a board sailor or elevated sail system.

The invention will be described further by way of example with reference to the accompanying drawings wherein: Figure 1 is a sketch showing in plan view an inflated hulled proa of equal length tubes whereon a sailboarder stands, sits or lies whilst operating an elevated sail.

Figure 2 is section A-A from Figure 1 showing the method of incorporating ribs within the inflated tube to create an efficient hydrodynamic section. It also shows the platform and the method of affixing the platform to the hulls.

Figure 3 is a cut away view of the folded platform which forms a valise in which hulls, sails, ancilliary equipment and personal clothing can be transported.

Figure 4 is a side view of the valise when transported.

Figure 5 is a plan view of a double ended catamaran or proa whereon 2 or more people can sail.

Figure 6 is a plan view of the preferred method of operating an elevated sail from the double ended catamaran (or proa) and a method of affixing the trampoline to the fibreglass half decks of each inflated hull.

Figure 7 is a sketch of the packaged catamaran or proa as well as a more detailed sketch of the steering mechanism for the elevated sail and the method of clamping the trampoline to the fibreglass half decks.

Figure 8 is a rigid inflated 'wing' sail shown on the inflated sailboard attached to an aluminium tube or track so that it can be positioned anywhere on that track (or tube) and angled to give an upward lifting force.

Figure 9 is a semi rigid inflated sail on the inflated catamaran and attached to the leeward hull on a track or aluminium tube in order to warp the 'wing' to give a controllable upward lifting force.

Figure 10 consists of a number of sketches of different constructions of wing sails to achieve different rigidity and/or aerodynamic characteristics.

Figure 11 is a side and frontal view of a wing sail embodying a number of features from Figure 10.

A preferred vessel of the invention has a rigid platform (a) affixed to two inflatable hulls (b) by means of a Qhalf deck' (c) which is affixed by means of a strip of material (e) which has been welded or glued to the outer skin of the hull (b), the affixing material has eyelets through which button clips (d) affixed to the half decks (c) by means of rivets, protrude and twist to lock in position. The platform is hinged in two places at (i) and is made firm by means of two struts (g) which are fixed transversely across the board by means of wing bolts (h) which are bolted to a threaded insert (j) in the platform (a).

The platform (a) struts (g) and half decks (c) can be manufactured from glass fibre or some similar material and the half decks (c) can be bonded or moulded to the platform (a).

On top of the platform (a) is affixed a track or tube (k) on which a traveller or ring (p) moves fore and aft as required to change the centre of effort.

To the ring or traveller (p) is attached a line (1) as shown in Figure 1 which terminates in a block (m) through which a running line (n) is connected to 2 bridle points on the elevated sail (not shown). The running line (n) has two handles (o) attached at a convenient height to enable the board sailor to control the elevated sail as to direction.

The inflated hulls (b) are sealed on the curved bottom and have 2 ribs (f) and (f&num;) welded on the inside parallel to the top of the inflated hull (b).

The ribs (f) and (f&num;) are of equal width along their length, but rib (f) is wider than (f&num;).

When the inflatable sailboard is dismantled the struts (g) are removed, hulls (b) are deflated as is the elevated sail (not shown) and the platform (a) is folded about its hinges (i) to form a valise with 2 compartments (q) and (r) into which all gear and personal clothing etc. can fit.

As shown in Figure 4 the valise so formed can be sealed with a cover (s) which extends over the 2 uncovered ends and along the top leaving a gap for the aluminium tube (k) which forms a handle with which to carry the valise. The cover (s) is kept in place by means of 4 button clips (t).

It has been found that such a valise made from glass fibre can weigh approx. 28 Ibs including all gear such as hulls, elevated sail, lines, handles and struts.

Alternatively as shown in Figure 8 it is possible to have the same configuration of platform (a) and hulls (b) with the same method of attaching the hulls (b) to the half decks (c) by means of a strip of material (e) welded to that hull (b) clipped to the half deck (c) with button clips (d) but the craft is propelled by an inflated wing sail (B).

The wing sail (B) however can be of a number of different shapes and profiles but the particular example given has an eliptic curve trailing edge, a slightly curved leading edge and a NACA profile of 00.

The wing sail (B) has a number of struts (D) within it and in this particular example the wing sail (B) is almost rigid thereby allowing the use of grab handles (G) which are welded or glued to the outside on both sides of the wing sail (B), thereby obviating the necessity for having a wishbone.

There is an extruded or manufactured mast heel (E) which is welded or glued to the wing sail (B) which allows the latter to pivot at the connection (F) to the '0' ring, swivel clip or traveller (p) on the tube or track (k).

The wing sail (B) apart from its improved aerodynamics compared to a conventional sail, has a number of other advantages in that it is easier to control, and to start with the rig in the water, as a soft sail creates considerable drag both aerodynamically and from surface skin tension initially when being lifted by the strap (H) whereas the profile of the rigid inflatable wing sail (B) has very little twist at the top of the sail and in any case causes considerably less drag than a floppy sail. It also weighs less than a conventional rig.

The wing sail (B) can be moved anywhere along the traveller or aluminium tube (k) and therefore to change tack (or shunt in this particular case) one slides the sail to the opposite end of the traveller (k) and holds the grab handles (G) on the opposite side. Any position along the track (k) can be sustained if a foot operated release trigger is used, and therefore the angle of the inflatable sail board to the wind can be changed at will.

Because the wing sail is comparatively rigid it should be possible to increase the sail area compared to a conventional sail because it is possible to reduce the angle of incidence if necessary thereby reducing the force, whereas in a soft sail by reducing the angle of incidence one creates a drag penalty from luffing.

In Figures 5, 6 and 7 an alternative type of inflated double ended catamaran or proa is shown with a similar type of hull (b&num;) and half deck (c&num;) but the platform (a&num;) is in the form of a trampoline and therefore the half deck (c&num;) fittings and method of fixing the trampoline (a#) are different. However, the method of affixing the inflated hulls (b&num;) to the half deck (c&num;) are similar in that a strip of material (e&num;) is glued or welded to the outer skin of the inflated hull (b&num;) through which button clips (d&num;) (which are riveted to the half deck (c#)) protrude and are turned to lock into position.

The trampoline (a&num;) slides over 2 aluminium tubes (u) which in turn slide into a moulded or fabricated section (v) which is clamped to the half deck (c&num;) over another moulding (w#) by means of two fasteners (w). This locks the aluminium tube (u) and trampoline (a#) in position.

If necessary an end stop (not shown) can be screwed into each aluminium tube (u) at each end on the inside of each moulded section (v) to stop the 2 half decks moving towards each other under compression.

The trampoline (a&num;) is then clipped over a ledge (d5) of one fibre glass half deck (c&num;) by means of button clips (d2) and tensioned and secured at the other side by means of a rope that is laced (d4) through another ledge (d3) moulded into the other half section (c&num;).

On the leeward side of the catamaran the moulded or fabricated sections (v) have an opening so that 2 further aluminium tubes (u#) can slide through to be affixed in a clamp (v#) which is moulded in the half deck (c&num;).

These 2 tubes (u&num;) are used to affix the necessary blocks (2) through which the line (1) runs to alter the centre of effort from an elevated sail (not shown) which propels the vessel.

The line (1) is a continuous line running through 4 mainsheet blocks (2 and 3) back to 2 jam cleats (4) which are secured to the top of the fabricated section (v).

In between the 2 main blocks (3) is a double block (m#) through which the 2 elevated sail tether lines (g#) and (f2) run.

A 2 line winch (y) is secured to a platform (x) which is moulded to the half deck (c#) on the leeward side of the vessel by means of 4 wing bolts (11) through 4 holes (10) to tapped inserts which have been let into the platform (x) during fabrication.

The winch (y) operates the yaw of the elevated sail in the following manner: The 2 tether lines (e# & t2)) from the elevated sail having passed through the double block (m&num;) then each pass through a single block on each side of the winch (y) which are set at a height which is the mid point of each drum.

As an example the left hand block (5) is set at the mid point height of the top drum and the right hand block (6) is set at the mid point height of the lower drum. The tether line is initially secured to each drum with approx. 10 turns of the drum in different directions so that when the steering wheel (z) is turned to the left the elevated sail will turn to the left and vice versa.

After having wound on approx. 10 turns in different directions a pin (7) is inserted into the top drum as close as possible to the line and the steering wheel is wound clockwise to reel in both lines together.

It would normally be necessary with this method of controlling the elevated sail to be able to lay out the tether lines onto a beach or some hard surface before attaching the elevated sail unless the elevated sail was particularly buoyant because the lines would not necessarily be of the same length at all times and therefore the elevated sail would tend to dive to one side or the other. However, to compensate for this tendency the blocks (5 & 6) are affixed to the winch by means of wing bolts (15) which can be detached and the blocks (5 & 6) are attached by a line (12) to a handle (13) which is clipped (14) to the winch (y).

While reeling out it is therefore possible to unclip one or both handles (13) and operate the ele vated sail until the pin (7) can be withdrawn to operate it with the steering wheel (z).

This method of control of the elevated sail can also be used in very light winds or to launch the elevated sail from the water where it may in both cases be necessary to be able to give a sharp tug of the line(s) (t# and t2) to achieve the desired re suit.

An alternative method of control of elevated sail is to utilise a sophisticated winch as in my patent application No. 8313952 which allows the elevated sail to be reeled in and out whilst operating the yaw control.

A further alternative method of elevated sail control is by remote control as per example in my patent application No. 8300742, whereby it would only be necessary to have a simple single line winch.

A further alternative method of control of the complete system is by means of powered winches for both the vessel and kite tether line whereby the kite winch could be powered by an electric motor, and an electrically powered winch could be coupled to the line (1) which changes the point of effort. If those winches were remotely controlled, and if the elevated sail had positive buoyancy it would be feasable to operate the vessel for example without being on board which could have both military and commercial applications.

In Figure 7 the diagram shows how it is possible on dismantling the inflated proa to form a tube by clamping the 2 half decks (c#) together by means of fasteners (9).

The tube so formed can form a package into which all sailing gear is placed including the winch (y) mouldings (V), elevated sail, control gear, trampoline (a), aluminium tubes (u and ui) which are designed to be the exact length of the tube, etc.

When all gear is placed inside the tube, including if required personal clothing etc., the end caps (17) are clamped in position with fasteners and if required a waterproof cloth covering (16) can be positioned with the same button clips (d&num;) as are used to clamp the tubes (b#) to the half deck (c&num;). The packed tube is carried by 2 handles (18) which are spring loaded to hug the half deck (c&num;) when not in use.

An alternative sailing system is shown in Figure 9 whereby an inflated semi-rigid wing sail (B) with struts (D) is attached through a glued or welded mast heel (E) to a swivel pin on a traveller (J) which can be positioned in any position along a track (K) which is attached to the half deck (c&num;).

From a fixing point (L) on the wing sail (B) a line (M) runs through a block and jam cleat (N) to another jam cleat and block (M#) carries on as (M&num;) to the opposite side of the wing sail (B) to be terminated at the point (L) again.

From a further glued or welded moulding (Q) at the top of the wing sail (B) at the mast head position plus another continuous line (R# and R) through further block and jam cleats (T and T&num;).

A third line (V and V#) runs from the trailing edge of the wing sail (B) at another welded or glued moulding 9u) through two blocks and jam cleats (Y and Y#).

By tensioning and relaxing the lines (M and M&num;) (R and R#) it is possible to form the wing sail (B) into any curvature required and to sheet in or out with lines (V and V&num;).

As the position of the attachment (E) of the wing sail (B) can be changed at will it is possible to alter both the centre of effort and the upward thrust at will to achieve the maximum reduction in drag with the highest coefficient of lift to suit both light and strong winds, and not only should better windward ability be achievable but by definition this should give higher speeds.

In Figure 10 a number of different construction methods are shown to achieve different characteristics in the inflated wing sails, although no NACA profiles are shown specifically.

Drawing A consists of an outer skin a of laminated non stretch material which can be heat welded on both sides and a tube c formed by welding a similar non stretch laminated material to the outer skin a at the points d and e before terminating at f. This forms a profiled frontal area and the tube c can have various other purposes in the military fieid if coated on the inside with for instance with an aluminium surface.

Valves can be either welded or glued to the outer skin a at the points e giving three separated compartments which could be inflated at different pressures to form either a very rigid or semi-rigid wing sail. The shape of the aft end of the wing sail is achieved with struts b.

In drawing B a semi-rigid inflatable wing sail (such as is shown in drawing A) is shown with the type of curve one could expect when used in the context of a normal sailing craft.

Drawing C shows a simplified inflatable wing sail which has vertical struts b only and one inflation point e. Depending upon the materials used this can again be either a rigid or semi-rigid wing sail, although one can not pressurise the leading edge differently from the rear section, as can be achieved in drawing A.

Drawing D shows a method of constructing a wing sail with both vertical and horizontal struts, as this particular configuration can achieve great rigidity in both the mast section and lower sail section comparable to a boom whilst allowing a smooth airflow and possible warping of the central rear section.

A plan view is shown whereby the outer skin a has within it a number of vertical struts b which form a mast section sealed and inflated separately to the rear wing section formed from 2 skins a&num; which have horizontal struts g with a lay fiat polyurethane curved section i of a thicker and less elastic nature welded to the strut which is in turn welded to the outer skin a&num;. The lower wing section therefore has more rigidity than the upper section.

An alternative method of constructing this type of wing sail is shown in Figure 11 which uses almost the same technique, but has as well the rigid central tube c as shown in drawing A, therefore having three inflation points e as opposed to drawing D which has only two inflation points e.

In Figure 11 the mast heel (E) and mast head (Q) mouldings are shown as is the attachment point (L). An alternative attachment point (h) is also shown which enables the mast section to be kept more vertical with less bend if this characteristic is necessary as in conventional vessels.

In Figure 10 drawing E an alternative wing sail with a very much more flexible rear section is shown. While retaining the rigidity of the mast section with vertical struts b the rear section has no struts at all, and is formed from 2 separate outer skins a&num; which need not be of the same laminated material as is the skin a of the mast section provided that it is capable of being glued or welded to the outer skin a of the mast section.

This configuration can be lighter and more use possibly to conventional yachts that wish to substitute the wing sail for their present sail, but wish to retain their present fittings and methods of controlling the sail. The invention is not necessarily limited to the above and could be combinations of the above hydrodynamic and/or aerodynamic characteristics.

As a further example the inflated hulls could possibly be composed of a number of independent chambers which have a flexible diaphragm within each chamber with one inflation valve on each side of the diaphragm.

This characteristic would make it possible to inflate initially with as an example a lighter than air gas such as helium which could then be tapped off to inflate the elevated sail, and be simultaneously filled with air or CO2 from the opposite valve to keep the integral shape of the chamber and hull.

If the hull was constructed of a meterial with a high peel strength possibly over 3 atmospheres of pressure could be maintained in each chamber and particularly in larger vessels the size of elevated sail or combination wing sail and elevated sail could be topped up as necessary during ocean going passages.

A further example of an alternative method for ocean going vessels would be to construct the central section of each hull of aluminium or some other similar material which could be pressurised to 200 (to give a larger capacity of lighter than air gas) and the forward and aft sections to be an inflated structure to still retain a better transportability characteristic as well as lightness.

With either of the two examples given above it would be possible for instance to attach a wing sail in harbour to negotiate the usual obstructions, and if required either to inflate the wing sail with a lighter than air gas such as helium from either of the above systems then to deploy the wing sail as an elevated sail, or, indeed to deflate and remove that wing sail and inflate a different elevated sail to deploy.

This could be particularly useful when encountering either very light or strong winds, as an elevated sail has no overturning moment as well as being able to seek higher winds at altitude and possibly to utilise the wind sheer encountered at different altitudes to apparently go directly into wind.

These methods would have a further advantage of increasing the safety factor should an inflated hull be holed for any reason.

Claims (34)

1. A vessel having a plurality of inflated hulls, each hull having on its underside a keel-like formation defined by one or more internal dividers extending lengthwise of the skin of the hull and secured thereto.

2. A vessel as claimed in claim 1, wherein the or each divider is in lateral tension and draws the skin inwards.

3. A vessel as claimed in claim 1 or 2, wherein the or each divider has a convex skin portion above and below it.

4. A vessel as claimed in claim 1, 2 or 3, wherein the dividers are parallel and are two in number.

5. A vessel as claimed in any preceding claim, wherein the or each divider is of flexible material welded or otherwise secured to the sheet material of the skin.

6. A vessel as claimed in claim 5 wherein the divider or dividers define one or more compartments inflatable separately from a body of the hull.

7. A vessel as claimed in any preceding claim wherein the or each divider lies parallel to the waterline when the vessel is afloat.

8. A vessel as claimed in any preceding claim, wherein each hull has an amidships portion of constant cross- section, the or each divider therein being of constant width over such admidships portion.

9. A vessel as claimed in claim 4 or any claim appendent thereto wherein the hull in cross-section has a generally circular or oval upper main portion, and said keel like formation is delimited by, on each side of a lower part of the hull, a pair of cusplike inwardly extending formations.

10. A vessel having attachment means for a sail which extends longitudinally from fore to aft to enable a point of attachment of a sail to be varied longitudinally of the vessel.

11. A vessel as claimed in claim 10 wherein the means is in the form of a rod or spar secured at its fore and aft ends and unsupported therebetween.

12. A vessel as claimed in claim 10 wherein the means is in the form of a rail having a base portion secured to the body of the vessel and presenting an upper part for securement to the sail.

13. A vessel as claimed in claim 10, 11 or 12, wherein a runner, slider or clamp is connected to the means and securable thereto at various positions therealong.

14. A vessel as claimed in claim 10, 11 or 12 wherein the means includes a pair of longitudinally spaced anchorages and a pair of tension elements of variable length, each element having one end secured to one said anchorage and its other end secured to the other end of the other element, the junction of the two elements being attached to the sail and being longitudinally movable by varying the lengths of the two elements.

15. A vessel as claimed in any of claims 10 to 14 wherein the sail is an elevated, kite-like, sail.

16. A vessel as claimed in claim 14 or 15 wherein an actuator is provided for simultaneously varying the lengths of said elements.

17. A vessel as claimed in claim 16, wherein the actuator is a wheel attached to a winch drum.

18. A vessel as claimed in any of claims 10 to 13, wherein a pedal is provided for effecting release of a slider from clamping relationship with said means.

19. A vessel as claimed in any of claims 10 to 13 or in claim 18, wherein the means is disposed adjacent one side of the vessel and means is provided adjacent the other side of the vessel for additional sail attachment.

20. A vessel comprising a plurality of elongate inflatable hulls and decking capable of being arranged to bridge the hulls and be attached thereto to locate the hulls and provide a working platform, the decking being capable of folding to form a portable container for the hulls, when deflated, and other parts.

21. A vessel as claimed in claim 20, wherein the decking includes at least two inverted channel structures extending fore-and-aft and adapted for securement each to an upper part of a respective one of the hulls.

22. A vessel as claimed in claim 20 or 21 wherein the decking is in the form of a rigid planar sheet member hinged about two or more axes to vender it foldable to form said container.

23. A vessel as claimed in claim 20 or 21 wherein the decking includes a flexible sheet member and at least two struts capable of attachment to the hulls to space them apart, the sheets being securable to the hulls and/or struts in stretched condition to form a support, and after release, being foldable to form said container.

24. A vessel as claimed in any of claims 20 to 23 wherein a handle of the container is formed by a dedicated member attached to the decking or by a part of the vessel structure arranged to be conveniently usuable as a handle.

25. A vessel as claimed in claim 24 wherein said part of the vessel is a fore-to-aft extending sail attachment bar.

26. A vessel as claimed in claim 21 wherein the or two of the channel structures can be brought together in the folded condition to define one chamber in the container and to close a second chamber in the container.

27. A vessel as claimed in any of claims 20 to 26, wherein fasteners are provided for maintaining the container closed.

28. A sail for a vessel, in the form of an inflatable envelope having a separately inflatable part defining a mast or similar sail stiffening structure.

29. A sail as claimed in claim 28 wherein said structure includes one or more elongate inflatable compartments.

30. A sail as claimed in claim 28 or 29 wherein said structure lies adjacent a generally upright edge of the sail.

31. A sail as claimed in claim 28, 29 or 30 wherein the sail is sufficiently stiff to maintain its shape and aerofoil configuration without additional rigidifying members or stays.

32. A sail as claimed in claim 31, wherein an envelope of the sail has a plurality of apertures extending from face to face of the sail providing manual engagement points obviating the need for a wishbone for a surf-sailboat.

33. A vessel substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

34. A sail substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.