FOLDING MULTI-HULL BOAT Field of the Invention This invention relates to a folding multi-hull boat. In particular, the invention relates to a folding catamaran, but it is also applicable to various other floating platforms having more than one hull or float.

Background of the Invention Many multi-hull boats exist, but catamarans, i. e. boats having two hulls, are by far the most common. Whilst catamarans have been adapted for many different uses, some of the most successful designs are sailing catamarans able to carry one or two people and used for recreational sailing on lakes or inshore waters, such as a Hobie Cat for example. In this document, these sailing catamarans are referred to as beach catamarans as they are generally designed to be launched and recovered straightforwardly from a beach or slipway.

One problem with beach catamarans is that they are relatively large in comparison to monohull sailing dinghies intended for similar use. In particular, beach catamarans are generally significantly wider than comparable monohull sailing dinghies. Consequently, transportation and storage of beach catamarans is relatively awkward. For example, they must be transported on trailers of similar or greater width than an average family car and they take up a greater amount of space in a boat park than comparable monohull sailing dinghies.

These disadvantages deter a large number of people who may enjoy sailing beach catamarans from owning and keeping such craft.

Another problem with all types of multi-hull boats is that they can be more difficult to manoeuvre in the water than comparable monohull boats.

Multi-hull boats generally have long slender hulls with higher directional stability when travelling through water than the hull of a typical monohull boat.

Greater force is therefore required to turn a multi-hull boat than a comparable monohull boat. Sharp turns can be particularly difficult as the different hulls of

a multi-hull boat may have to turn through a different circumference, which significantly increases drag.

Another widely recognised problem in the design of multi-hull sailing boats is pitch-poling. This occurs when a boat's bow becomes submerged and slows the boat down sharply. Pressure in the sails can then cause the stern of the boat to lift and the boat consequently to somersault forward over its bow.

Multi-hull sailing boats are particularly susceptible to this problem, as their hulls tend to have little buoyancy at the bow. Some multi-hull sailing boats therefore have raised bows to reduce the risk of submerging. Other multi-hull sailing boats have hulls with sharply pointed bows, i. e. having a so-called "wave piercing"design, that do not slow the boat significantly when submerged. However, both of these solutions require hull shapes that have more drag and that create less lift than possible with comparable ideal hull shapes.

The present invention seeks to overcome these problems.

Summary of the Invention According to a first aspect of the present invention, there is provided a folding boat comprising two or more hulls and a folding frame mounted on the hulls such that, to fold the boat between an operable configuration in which the boat is intended to be used and a folded configuration in which the boat is intended to be stored, respective hulls can be rotated about a first axis by which the frame folds and about a second axis substantially perpendicular to that axis.

According to a second aspect of the present invention, there is provided a method of folding a boat between an operable configuration in which the boat is intended to be used and a folded configuration in which the boat is intended to be stored, the boat comprising two or more hulls and a folding frame mounted on the hulls and the method comprising rotating respective hulls about a first axis by folding the frame and a second axis substantially perpendicular to that axis.

In other words, the boat's frame folds to reduce the size of the boat for transportation or storage. In addition, the hulls can be rotated in a direction at right angles to the direction in which the frame folds. This allows the hulls to be turned such that, when the frame is folded, the hulls can be positioned very close together. The folded boat can therefore to be compact in comparison to the unfolded boat and transportation and storage are made much more convenient than for previous beach catamarans for example.

The boat can be any vessel having more than one hull, i. e. any multi- hull vessel. The boat may even just be a floating platform or pontoon rather than a vessel intended to move and the hulls may be floats rather than bodies designed to move through water. However, it is preferred that the boat is a catamaran. In other words, the boat may have two parallel hulls like a conventional catamaran. It is particularly preferred that the boat has four hulls.

More specifically, the boat may have two pairs of hulls. When the boat if configured for use, the hulls of each pair can be arranged in line with one another and the pairs of hulls can be parallel with one another. This is useful as the boat can have similar characteristics in use to a conventional catamaran, yet be more compact when folded for storage or transportation.

According to a third aspect of the present invention, there is provided a boat having four hulls, two of which hulls are mounted to the rear of the other hulls in the direction the boat is usually intended to travel such that they can be rotated to cause the boat to turn.

According to a fourth aspect of the present invention there is provided a method of steering a boat, the boat having four hulls, two of which hulls are mounted to the rear of the other hulls in the direction the boat is usually intended to travel, and the method comprising rotating the two hulls to cause the boat to turn.

This allows a greater turning force to be exerted in comparison to conventional rudders and the boat may therefore be steered more effectively.

According to a fifth aspect of the invention, there is provided a sailing boat having at least one hull mounted forward of another hull in the direction

the boat is usually intended to travel, wherein the forward hull is mounted such that it is able react to changes in the distribution of buoyancy exerted on it to change its pitch in comparison to the other hull.

This reduces the chance of the front of the forward hull becoming submerged and causing the boat to pitch-pole.

Examples of the invention will now be described with reference to the accompanying drawings.

Brief Description of the Drawings Figure 1 is a perspective view of a boat according to the invention configured for use; Figure 2 is a close up perspective view of a central portion of a frame of the boat of figure 1; Figure 3 is a perspective view of the hulls and frame of the boat of figure 1; Figure 4 is a perspective view the hulls and frame of the boat of figure 1 ready for folding; Figure 5 is a perspective view of the hulls and frame of the boat of figure 1 in which the hulls have been rotated to prepare the frame for folding; Figure 6 is a perspective view of the hulls and frame of the boat of figure 1 in which the frame has been folded; Figure 7 is a perspective view of the hulls and frame of the boat of figure 1 in a fully folded configuration; Figure 8 is an illustration of the steering mechanism of the boat of figure 1; Figure 9 is an illustration of the boat of figure 1 in rough water; Figure 10 is a close up view of the front of the boat of figure 1; Figure 11 is a perspective view of the hulls and frame of another boat according to the invention in a fully folded configuration; Figure 12 is a perspective view of another boat according to the invention substantially configured for use;

Figure 13 is a perspective view of the hulls and frame of the boat of figure 12 in a partially folded configuration; Figure 14 is a perspective view of the hulls and frame of another boat according to the invention in a partially folded configuration; and Figure 15 is a perspective view of the hulls and frame of another boat according to the invention in an unfolded configuration.

Detailed Description Referring to figure 1, a sailing boat 1 has four hulls 2 attached to a frame 3. The frame 3 comprises four arms 4 that extend radially from a central spine 5 to the corners of an imaginary rectangle. Indeed, in this example, the central spine 5 is actually a cruciform and the arms 4 extend from the ends of the cruciform, i. e. substantially at right angles from one another, to the corners of an imaginary square. Left and right side braces 6 extend between (and slightly beyond) the outer ends of the arms 4 from the front to the rear of the boat 1 on the left and right sides of the boat 1 respectively. Front and rear cross braces 7 extend between the ends of the side braces 6 from one side of the boat 1 to the other. The arms 4, spine 5, side braces 6 and cross braces 7 thus together form a rectangular frame. A trampoline 8 is secured to the braces 6,7 and extends over the arms 4 and spine 5 to provide a platform for the boat's crew. In another example, the trampoline 8 is secured at its corners to the ends of the arms 4, but still extends over the arms 4 and spine 5 to provide a platform for the boat's crew.

Each of the fours hulls 2 is attached to the underside of the outer end of a respective arm 4. In this example, the hulls 2 each have an upright 9 that extends from the hull 2 to the respective arm 4. Bearing carriers 10 mounted on the ends of each arm 4 house bearings that retain the ends of the uprights 9 so that the uprights 9 and consequently the hulls 2 can be rotated in a plane substantially parallel to the arms 4. The lengths (i. e. major axes) of the uprights 9 thus effectively define axes about which the hulls 2 can rotate.

Conventional sprung locking pins (not shown) housed in the uprights 9 are able to protrude into holes in the bearing carriers 10 to lock the hulls in orientation to the lengths of the arms 4. In particular, the forward hulls 2 can be locked such that they are parallel to one another (and substantially parallel to the left and right side braces 6), i. e. such that they extend from the front to the rear of the boat 1. When the rearward hulls 2 are rotated to be parallel with the forward hulls 2, the boat 1 has the basic characteristics of a catamaran, as the hulls 2 of each pair effectively behave as a single hull. The locking pins can (also) lock the hulls 2 such that they are each substantially parallel to the arm 4 to which they are attached, as shown in figure 5. This allows the boat 1 to be folded, as described in more detail with reference to figures 4 to 7 below.

The bearing carriers 10 also house bearings that retain them on the ends of the arms 4 such that they can rotate around the arm 4, i. e. in a plane normal to the length of the arm 4 to which they are attached. This allows the hulls 2 to be rotated around the arms 4 as described in more detail below, with reference to figure 7.

In this example, a mast 11 rests on the central spine 5 and is held in place by mainstays 12 and a forestay 13 in a conventional manner. Referring to figure 2, the spine 5 is therefore provided with a mast cup 14 for receiving the base of the mast 11. The mast 11 supports a mainsail 15 as shown in figure 1.

A foresail (not shown) can be supported on the forestay 13 if desired. A tiller crossbar 16 extends between pivots mounted toward the rear of the rearward hulls 2 and a tiller extension 17 extends from the tiller crossbar 16 such that the tiller can be operated from the trampoline 8.

Referring to figure 2, the arms 4 are each joined to the central spine 5 by a hinge 18 such that the arms 4 can be folded upwardly toward one another. In other words, the hulls 2 can each rotate about an axis defined by the hinge 18 of the arm 4 to which it is attached. When the arms 4 are in their unfolded configuration, they are held in place by conventional sprung locking pins 19 housed in the arms 4 that extend through appropriately located holes in the central spine 5.

Referring to figure 3, in this example the central spine 5 also has a strut 20 that extends downwardly from the centre of the central spine 5 to support four frame stays 21. The frame stays 21 can be attached to the arms 4 to brace them when they are in the unfolded configuration. In other examples, either or both of the strut 20 and stays 21 or the side and cross braces 6,7 are omitted to save weight. However, this is only appropriate for boats that experience light loading of the platform 3. Otherwise, the additional support of the strut 20 and stays 21 and/or the side and cross braces 6,7 is required.

Referring to figures 4 to 7, when it is desired to fold the boat 1 for transportation or storage, the mast 11, trampoline 8, strut 20, strays 21 and braces 6,7 are removed, such that the boat 1 is configured as shown in figure 4.

The hulls 2 are then rotated by around 45° in a plane parallel to that defined by the frame 3 in the unfolded configuration shown in figure 4, i. e. about the axes defined by the uprights 9. In other words, the hulls 2 are rotated in the directions of arrows A shown in figure 4 from a position in which the hulls are parallel with one another to a position in which each hull 2 is in line with the arm 4 to which it is attached, as shown in figure 5. In this position, the locking pins housed in the uprights 9 protrude into holes in the bearing carriers 10 to lock the hulls 2 in place. The arms 4 can then be folded at hinges 18 in the direction of arrows B shown in figure 5. In other words, the hulls 2 are rotated about axes defined by the hinges 18 (perpendicular to the axes defined by the uprights 9) upwardly and toward one another on the arms 4. More specifically, the arms 4 and hulls 2 are rotated through approximately right angles (i. e. about 90°) until they are substantially parallel with one another, as shown in figure 6.

In relation to the boat 1 as configured for use, the hulls 2 are now substantially vertical, although the orientation of the boat 1 may, of course, be altered for storage or transportation. Finally, the hulls 2 are rotated about the lengths (or major axis) of the arms 4, i. e. in the direction of arrows C shown in figure 6.

More specifically, the two forward hulls 2 are rotated toward one another and the two rearward hulls 2 are rotated toward one another (in this example by around 45°).

The boat 1 is then in its fully folded configuration, as shown in figure 7.

In this configuration, the forward hulls 2 are positioned side by side and preferably actually or very nearly touching one another so that they occupy as little space as possible. Likewise the rearward hulls 2 are positioned side by side and preferably actually or very nearly touching one another for the same reason. The folded boat 1 is therefore relatively flat in comparison to the partially folded configuration, shown in figure 6, in which the hulls 2 are all aligned with their depths substantially at right angles from one another.

Referring to figure 8, when the boat is configured for use, the rearward hulls 2 can be manipulated by a person located on the trampoline 8 using the tiller crossbar 16 and tiller extension 17. More specifically, the rearward hulls 2 can be rotated to and fro in the direction of arrows D shown in figure 8 to steer the boat 1. In another example, the rearward hulls 2 can be locked in alignment with the forward hulls 2 using the sprung locking pins and the tiller crossbar 16 and tiller extension 17 can be arranged to allow manipulation of conventional rudders. However, arranging the boat 1 to be steered by rotating the rearward hulls 2 means that the boat 1 can have less drag and a greater turning force may be exerted by rotating the hulls 2 in comparison to manipulating conventional rudders.

Referring to figures 9 and 10, the forward hulls 2 are mounted to their uprights 9 by rockers 22. The rockers 22 allow the hulls 2 to rock forwards and backwards in relation to the frame 3 in the direction of arrow E shown in figures 9 and 10. More specifically, the forward hulls 2 can pivot in relation to the frame 3 to change their pitch. As seen in figure 9, when the boat 1 encounters waves or swell, this allows the forward hulls 2 to react to variations in the distribution of the buoyancy exerted on them to rotate and remain more tangential to the surface S of the water than would be possible with a fixed mounting. Consequently, the risk of the bow (i. e. forward part) of forward hulls 2 becoming submerged and causing the boat 1 to pitch-pole is reduced.

In another example, a spring and damper arrangement is provided between the frame 3 and the forward hulls 2. The springs are set up to bias the

forward hulls to neutral pitch, i. e. parallel to the rearward hulls 2. The dampers are arranged to slow changes in pitch.

Referring to figure 11, in another example, the hulls 2 are mounted so that they can slide on the arms 4. More specifically, the arms 4 comprise tubes of substantially uniform cross section along their length. The bearing carriers 10 comprise bushes adapted to cooperate with the arms 4 so that they can slide along the arms 4 in the direction of arrows F shown in figure 11. Sprung locking pins 23 housed in the outer ends of the arms 4 can protrude into suitably located holes in the bearing carriers 10 to lock the bearing carriers 10 in position along the length of the arms 4. Thus, in the partially folded configuration shown in figure 6, the arms 4 can be retracted to a position that does not extend outwardly from the space between the hulls 2. In another example, the arms 4 comprise cylindrical tubes and the bushes of the bearing carriers 10 are adapted to rotate around the arms 4 as well as slide along them.

The bearings provided to rotate the bearing carriers 10 around the arms 4 to achieve the fully folded configuration shown in figure 7 can then be omitted.

Referring to figure 12, in another example, a sailing boat 24 has four hulls 25 attached to a frame 26. n this example, the frame 26 comprises four arms 27 that extend radially from a central spine 28 to the corners of an imaginary square. Left and right side braces 29 extend between and beyond the outer ends of the arms 27 in the direction of the front to the rear of the boat 24 as intended for use. A rear brace 30 extends between the rearward ends of the left and right side braces 29. A trampoline (not shown) is secured to the side braces 29 and extends over the central spine 28 and arms 27 to form a platform for the boat's crew.

Each of the four hulls 25 is attached to the underside of the outer end of a respective arm 27. More specifically, each of the hulls 25 has a forward upright 31 and rearward upright 32 that extend upwardly from the hulls 25.

The two forward hulls 25 are attached to the ends of respective arms 27 by their rearward uprights 32. The two rearward hulls 25 are attached to respective arms 27 by their forward uprights 31.

Each of the uprights 31,32 comprises a cylindrical tube. Bushes 33 are mounted on the ends of each of the arms 27. Respective forward and rearward uprights 31,32 of the hulls 25 are housed in respective bushes 33 to attach the hulls 25 to the arms 27. Consequently, the forward hulls 25 are able to rotate about their rearward upright 32 and the rearward hulls 25 are able to rotate about their forward upright 31. Sprung locking pins (not shown) housed in the uprights 31,32 can protrude into holes in the bushes 33 to lock the hulls in orientation with the arms 27, as described in more detail below.

Likewise, the side braces 29 are each provided with bushes 34 located to attach the braces 29 to the forward and rearward uprights 31,32 of the hulls 25* Each hull 25 is therefore attached to one or other of the side braces 29 by both its forward and rearward uprights 31,32. The side braces 29 can be rigidly attached to the forward uprights 31 of the forward hulls 25 and the rearward uprights 32 of the rearward hulls 25. However, the bushes 34 of the side braces 29 can rotate about the rearward uprights 32 of the forward hulls 25 and the forward uprights 31 of the rearward hulls 25. Again, sprung locking pins (not shown) housed in the uprights 31,32 can protrude into holes in the bushes 34 to lock the hulls 25 in orientation with the side braces 29, as described in more detail below.

In this example, two (flexible) masts 35 are mounted on the side braces 9. The tops of the masts 35 are secured to one another and the masts 25 are held up by forward and rearward stays 36. The masts 25 each support sails 37 and wishbone booms 38. A rudder 39 is mounted at the rear of each rearward hull 25 to allow the boat 24 to be steered. The rudders 39 can be manipulated using a conventional tiller assembly (not shown).

Referring to figure 13, each of the side braces 29 is formed of two elongate members hinged at a brace hinge 40 at the midpoint between the rearward upright 32 of the respective forward hull 25 and the forward upright 31 of the respective rearward hull 25 to which the brace 29 is attached.

The brace hinges 40 allow the side braces to fold outwardly from the boat 24 about axes that are substantially vertical when the boat 24 is oriented as

intended for use. In addition, each of the arms 27 is attached to the central spine 28 by a hinge 41, similar to the boat 1 described above with reference to figures 1 to 11. The distances between the hinges 40,41 and the bushes 33 are arranged such that the frame 26 can fold simultaneously at hinges 40,41 as shown in figure 13. More specifically, the hinges 40 fold to rotate the forwards hulls 25 by around 45° about their rearward uprights 32 and the rearward hulls 25 by 45° about their forward uprights 32 in the opposite direction. At the same time, the hinges 41 fold to rotate each of the hulls through approximately right angles (i. e. about 90°) upwardly towards one another. When the frame 26 is fully folded, the boat 24 is therefore in a configuration resembling that shown in figure 7 for the boat 1 described above.

Referring to figure 14, in another example, a boat 42 has four partial hulls 43. The partial hulls 43 are shaped such that in an unfolded configuration, pairs of partial hulls 43 form single composite hulls. The partial hulls 43 can fold on arms 44 about hinges 45 that join the arms 44 to a central spine 46 and about hinges 47 between the partial hulls 43 in a similar way to the boat 24 described above with reference to figures 12 and 13. However, this boat 42 has the advantage that the composite hull shape corresponds more closely with that of a conventional catamaran.

Referring to figure 15, in another example a boat 47 has four hulls 48 arranged effectively to form a trimaran. More specifically, two of the hulls 48 are aligned one in front of another along their lengths effectively to form a central hull. The other two hulls 48 are arranged parallel to the centrally positioned hulls 48, one on either side of the centrally positioned hulls 48.

Each hull 48 has a forward upright 49 and rearward upright 50, similar to those of the hulls 25 described above with reference to figures 12 and 13.

The hulls 48 are attached to a frame 51 that again comprises four arms 52 extending radially from a central spine 53. However, in this example, the arm 52 that extends forward in the direction the boat 47 is usually intended to travel is longer than the other arms 52 (although the rearward extending arm 52 could be the longer arm 52 if desired). Rearward uprights 50 of each hull 48

are attached to a respective arm 52 by rearward bushes 54 mounted along the length of the forward arm 52 and on the outer ends of the other arms 52. The forward uprights 49 of the centrally positioned hulls 48 are also attached to their respective arms 52 by forward bushes 55 mounted on the outer end of the forward arm 52 and along the length of the rearward arm 52. A brace is mounted on the rearward bush 54 of the forward arm 52 and, in the operable configuration shown in figure 15, the brace 56 extends between the forward uprights 49 of the hulls 48 on either side of the centrally positioned hulls 48.

Thus, all of the hulls 48 are secured by both their forward and rearward uprights 49,50 to provide the boat 47 with sufficient rigidity.

The rearward uprights 50 of the hulls 48 on either side of the centrally positioned hulls 48 are housed by the rearward bushes 54 such that the hulls 48 can rotate about the rearward uprights 50. Sprung locking pins (not shown) housed in the rearward uprights 50 can protrude into holes in the bushes 54 to lock the hulls 48 parallel with the centrally positioned hulls 48 or substantially at right angles to the centrally positioned hulls (i. e. parallel to the arms 52).

When it is desired to fold the boat 47, the brace 56 can be removed.

However, in this example, the brace 56 is detached from the forward uprights 49 of the hulls 48 on either side of the centrally positioned hulls 48 and can be rotated about its mounting on the forward arm 52 so that it is parallel with the forward arm 52. The hulls 48 on either side of the centrally positioned hulls 48 can then be rotated about their rearward uprights 50 by approximately right angles (i. e. about 90°) such that they are perpendicular to the centrally positioned hulls 48, The frame 51 can then be folded by rotating the arms 52 upwardly by substantially right angles (90°) about hinges 57 by which the arms are attached to the central spine 53. The boat 47 can therefore be folded to a configuration similar to that described above with reference to figure 6, although the hulls 48 do not all point in the same direction as shown in that illustration.