GB2240072A - Connecting hulls of multi-hulled boats - Google Patents

Abstract

A multi-hulled boat, for example a catamaran, has a pair of hulls (12a, 12b) between which extend fore and aft crossbeams (10a, 10b). The ends of each crossbeam are received within respective sockets 33 in the hull, a key 30 and keyway arrangement 34 ensuring rigidity. The hulls are held together by means of a trampoline (28) stretched across the space between the hulls and the fore and aft crossbeams. <IMAGE>

Description

BOATS The present invention relates to multi-hulled boats, particularly sailing craft, and including catamarans and trimarans.

A typical catamaran comprises a pair of parallel hulls connected together by means of first and second crossbeams. The beams are generally removable from the hulls so that the boat can be dismantled for transport and put together on site.

Known mechanisms for securing the crossbeams to the hulls will now be described with reference to Figures 1 and 2 of the accompanying drawings, in which: Figure 1 shows a first securing mechanism of the prior art; and Figure 2 shows a second securing mechanism of the prior art.

Figure 1 shows one way in which crossbeams have been conventionally secured to hulls of multi-hulled boats, for example catamarans. One end of a crossbeam 10 is secured to its corresponding hull 12 by means of screws or bolts 14 which pass through the beam into an underlying bulkhead 16. To assist in location of the beam and to prevent at least to some extent pivotal movement between the beam 10 and the hull 12 the hull is provided with a transverse recess 18 in its upper surface 20 within which the beam is located. The beam is a flattened oval in section.

The other hull (not shown) is attached to the other end (not shown) of the beam 10 in a like manner.

Similarly, a further beam (also not shown) extends between the hulls and is again attached in a like manner.

Catamarans which have crossbeams which are secured in this way have a number of disadvantages, not least that the use of separate fixing screws or bolts 14 means that the user has to carry around a screwdriver or other tool in order to assemble the boat. There is also a tendency for the screws or bolts 14 accidentally to be dropped or to be mislaid. Even once the boat has been assembled, it is not ideal because there is not absolute rigidity between the hull 12 and the crossbeam 10, particularly against twisting forces. A lack of rigidity against twisting forces means that in use there is a tendency for one hull to move slightly with respect to the other, this both reducing sailing efficiency and also making the boat feel somewhat limp or 'floppy' to the user.A further problem is that the flattened oval cross-section of the beam 10 does not give a particularly good strength to weight ratio. The horizontal flattening means that the beam has greatest strength against bending in the horizontal plane; this is clearly inefficient as in use most of the bending forces applied to the beam are likely to be vertical, arising from people standing on it.

The mechanism shown in Figure 2 represents an attempt to overcome at least some of the disadvantages of the arrangement of Figure 1. Here, the end of the beam 10 is secured to the hull 12 by being received in a correspondingly-shaped hole 22 passing through the thickness of the hull. Both the beam 10 and the hole 22 are generally of aerofoil cross-section so preventing rotation of the beam once it is in position.

Longitudinal movement of the beam is prevented by means of a stop 24 which abuts the inner side of the hull and a releasable latch 26 which clips onto the outside of the hull.

Because of the non-circular cross-sectional shape of the beam 10 it is difficult to make the fit within the hole 22 particularly close: as will be appreciated manufacturing tolerances on such a complex non-circular shape are likely to be high, at least without making use of very expensive carefully controlled manufacturing techniques. The loose fit results, as before, in a very limp or 'floppy' boat which may be considered by some as not very pleasing to use. A further result of the looseness of fit is likely to be that the boat will creak as it moves through the water, the creaking resulting from slight relative movement between the end of the beam 10 and the hull 12.

Furthermore, the flattened or partially-aerofoil section of the beam does not give a good strength to weight ratio.

It is an object of the present invention to provide a multi-hulled boat which alleviates at least some of the disadvantages of the prior art.

It is a further object to provide a multi-hulled boat which is easy to assemble and dismantle while at the same time being relatively rigid in use.

According to the present invention there is provided a boat having at least two hulls, the hulls having respective sockets keyed to which are the respective ends of a crossbeam connecting the hulls.

A boat constructed in this fashion may be easily dismantled and reassembled, and when assembled is relatively rigid particularly against twisting forces.

The keying of the crossbeam to the sockets results in a secure fit with little relative movement between the crossbeam and the hulls, so, in addition, reducing or eliminating the creaking noises associated with conventional boats in use.

The sockets to which the ends of the crossbeam are keyed may comprise blind bores in the respective hulls, with the ends of the crossbeam abutting the respective ends of the bores. Biassing means for example a trampoline extending between the hulls, may be provided to bias the hulls towards each other. Where the sockets comprise blind bores, this enables the crossbeams to be securely retained within the bores, with the ends of the beams securely pressed against the respective end faces of the bores. The trampoline or biassing means may comprise the sole means by which the crossbeam is retained within the sockets; thus, no additional latching mechanism is required to prevent the beam from coming out of the socket.

In one convenient arrangement, the crossbeam is circular in cross-section, this providing the maximum possible strength for a given weight of beam.

The necessary keying between the beam and the socket may be effected either by means of a key on the beam and a keyway in the scoket, or vice versa. It would even be possible for both to have a key and also a keyway. Preferably, the key extends longitudinally of the crossbeam and/or socket, and is also preferably of rectangular cross-section. The key is desirably integral with the beam or socket, but it could instead be separate from but secured to it, for example by screwing or bolting.

While the key and the keyway in the preferred embodiment are at the uppermost parts thereof (that is, at the twelve o'clock position when seen in crosssection), it would also be possible for the key and keyway to be positioned elsewhere. One could also make use of several keys and keyways within the same socket.

The sockets may be positioned within or formed by the respective hulls. Typically, the hulls may be moulded of a suitable composite material, and the sockets may comprise blind bores integrally moulded with the main bodies of the respective hulls.

Alternatively, the sockets could be of a different material which is bonded or otherwise secured into appropriately sized mounting bores of the hulls. In a preferred arrangement, the sockets are manufactured separately, but of the same material as the main body of the hulls themselves. Thus, when the sockets are secured, for example by bonding, into the appropriate mounting bores, one effectively ends up with a unitary hull and socket. This is both aesthetically pleasing and also advantageous from a strength point of view.

Where the socket is initially manufactured separately and then secured within a mounting bore of the hull, the socket itself is conveniently moulded in at least two separate parts. The parts may then be bonded or otherwise secured together to form the final socket before the socket is mounted to the hull.

The sockets are conveniently located at least partially within upwardly-extending protuberances on the upper surfaces of the respective hulls.

In a sailing craft such as a catamaran, having two hulls, each hull may have fore and aft sockets on the inboard side respectively for receiving fore and aft crossbeams.

The invention also extends to a single feature or compatible combination of features herein disclosed or described (other than with reference to Figures 1 and 2 which represent prior art).

The invention may be carried into practice in a number of ways and one specific catamaran embodying the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 3 is a perspective view of a catamaran embodying the present invention; and Figure 4 shows a detail, corresponding to figures 1 and 2, indicating how the crossbeam is secured to the hull.

The catamaran embodying the present invention is shown schematically in Figure 3. It comprises a pair of hulls indicated generally at 12a and 12b secured together by forward and rear crossbeams, respectively 10a, 10b. Extending across the generally square aperture defined by the crossbeams and the hulls there is a stretched trampoline 28.

Both ends of each of the beams 10a, lOb are secured to the respective hulls 12a, 12b in a similar manner. This securing mechanism is shown in more detail in Figure 4, to which reference will now be made.

In this embodiment, the crossbeam 10 is of circular cross-section and has attached to it or integral with it an outwardly-extending elongate key 30. The end of the crossbeam fits within a corresponding circular blind bore 32 defined by a socket 33 in the hull 12, with the key 30 being received in a corresonding keyway 34. The key and keyway arrangement prevents rotational movement of the beam 10 about its own axis, as well as pivotal movement between the beam and the hull. Longitudinal movement in one direction is prevented by the fact that the end of the beam abuts the blind end 36 of the bore 32.

A bolt rope track 38 is provided along the inner side of the hull 12, with a further track 40 along the beam 10. Both of these tracks are shown only schematically in the drawing. In order to assemble the boat, all the user has to do is to push the ends of the beams 10a, 10b into the corresponding bores in the hulls 12a, 12b and then thread the bolt ropes at the edges of the trampoline 28 into the respective bolt rope tracks. Once in position, the trampoline is tightened by means of tension lacing (not shown) at one side and at the rear, and all that remains is for the mast, rigging and sails to be erected in the usual manner. The two hulls are pulled towards each other by the tension in the trampoline 28, so ensuring that the beams 10a, 10b are always securely positioned within their corresponding bores.More specifically, as will be seen from the detailed drawing of Figure 4, the tension in the trampoline 28 will keep the beam 10 biassed into engagement with the end wall 36 of the blind bore 32.

The hull 12 is desirably moulded of a suitable composite material, such as a glass fibre, carbon fibre, or Kevlar (trade mark) composite. While it could be moulded in a single piece, this is likely to be rather difficult because of the internal shape of the keyway 34, and a more practical arrangement is to mould the main body of the hull 12 and the socket 33 separately. This is done by initially moulding the hull with a circular blind bore in it which is slightly larger than that of the blind bore 32. A separate socket or sleeve is then moulded to fit within this blind bore, this sleeve conveniently itself being moulded in two parts so that the keyway 34 can be manufactured to the required tolerances.The two halves are then bonded together and the resultant sleeve, the inner surface of which defines the bore 32 and the keyway 34, is bonded into the circular blind bore originally formed in the hull. The sleeve may, but need not, be formed of the same material as the hull, so that when it is bonded into position the resultant completed hull is effectively unitary.

Alternatively, for greater strength or improved tolerances a sleeve of a different material (for example metal) could be used.

The crossbeam 10 may be of any convenient material, for example of aluminium alloy or a suitable composite. Alternatively, it could even be wooden.

The key 30 may either be a separate member which is screwed or otherwise secured to the beam or alternatively it could be manufactured as an integral part of the beam. The beam could, for example, be moulded or extruded using a die which incorporates the shape of the key.

In alternative arrangements (not shown) the key and keyway could be located elsewhere than at the twelve o'clock position: it will be appreciated that the exact position and number of the keys and keyways is not critical to the operation of the invention. It would also be possible to make use of a reverse arrangement, that is a key extending from the inside surface of the bore 32 which is shaped to cooperate with a corresponding keyway in the crossbeam 10. Both arrangements might even be used in the same boat and/or in the same socket.

It is not essential for the socket to be located within a protuberance 42 of the hull, as is shown in Figure 4: it could instead be located within the main body of the hull.

Claims (15)

CLAINS:

1. A boat having at least two hulls, the hulls having respective sockets keyed to which are the respective ends of a crossbeam connecting the hulls.

2. A boat as claimed in claim 1 in which the sockets comprise blind bores in the respective hulls.

3. A boat as claimed in claim 1 or claim 2 including biassing means to bias the hulls towards each other.

4. A boat as claimed in claim 3 in which the biasing means comprises a trampoline.

5. A boat as claimed in any one of the preceding claims in which the crossbeam is of circular section.

6. A boat as claimed in any one of the preceding claims in which the keying between the crossbeam a said respective socket is effected by a key on the crossbeam engaging a keyway in the socket.

7. A boat as claimed in any one of claim 1 to 5 in which the keying between the crossbeam and a said respective socket is effected by a key on the socket engaging a keyway in the crossbeam.

8. A boat as claimed in claim 6 in which the key is integral with the crossbeam.

9. A boat as claimed in claim 7 in which the key is integral with the socket.

10. A boat as claimed in any one of the preceding claims in which the respective sockets are defined by sleeves received within mounting bores of the respective hulls.

11. A boat as claimed in claim 10 in which the sleeves are of the same material as the hulls.

12. A boat as claimed in claim 11 in which the sleeves are of a different material from the hulls.

13. A boat as claimed in any one of claims 10 to 12 in which the sleeves are moulded in two parts, the parts being then joined together.

14. A boat as claimed in any one of the preceding claims in which each socket is located at least partially within an upwardly-extending protuberance of the respective hull.

15. A boat substantially as specifically described with reference to figure 3 or to figure 4.