GB1591580A

GB1591580A - Boat hulls

Info

Publication number: GB1591580A
Application number: GB2569778A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-05-31
Filing date: 1978-05-31
Publication date: 1981-06-24

Description

(54) IMPROVEMENTS IN OR RELATING TO BOAT HULLS (71) I, DOUGLAS BEN IAN PROCTOR formerly of "Fenmead", Brook Avenue, Warsash, Hampshire, and now of Hosdown Cove, Bridge Road, Kingswear, Near Dartmouth, Devon, a British subject, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to boat hulls and is particularly concerned with such hulls as are manufactured by assembly of pre-formed components.

According to the present invention there is provided a boat hull comprising an assembly of port and starboard pre-formed hull sections, fore and outwardly extending marginal edge portions of which are joined together with overlap substantially on the centre line of the hull and wherein said marginal edge portions overlap in athwartships direction when viewed in plan, and are shaped and joined together to form a longitudinally extending spine which reinforces the hull against longitudinal bending.

Further according to the present invention there is provided a method of manufacturing a boat hull which comprises pre-forming port and starboard hull sections each of which has a fore and outwardly extending marginal edge portion which is to be located substantially along the centre line of the hull to extend athwartships thereof; assembling the hull sections together with the marginal edge portions overlapping each other in an athwartships direction when viewed in plan and joining said marginal edge portions together so that they form a longitudinally extending spine which reinforces the hull against longitudinal bending.

Still further according to the present invention there is provided a boat hull when manufactured by the method as specified in the immediately preceding paragraph. There is also provided a boat when incorporating at least one hull in accordance with the present invention.

The hull sections are preferably formed in plastics material by injection moulding or vacuum moulding techniques. It is envisaged however that the hull sections can be preformed by other techniques and in other materials, for example by laying or spraying of glass fibre reinforced plastics or by pressing from a metal sheet such as an aluminium alloy.

For boat hulls of what may be regarded as small length, say less than twenty feet, it is likely that each of the starboard and port sides of the hull will be constituted by a single pre-formed hull section so that when these two hull sections are assembled together the resultant hull has a spine extending substantially along its centre line over the stem and keel and possibly over the stern or transom. If required however a longitudinally extending array of two or more port or starboard sections can be pre-formed with such sections on the port or starboard side appropriately joined together along transversely extending split lines.

The present invention was primarily developed for small length boat hulls in which a single starboard hull section and a single port hull section are provided, such sections being formed in plastics by injection moulding and in which the port hull section and the starboard hull section substantially mirror each other at least other than in the region of their marginal edge portions; for convenience the following description will be in relation to such form of hull assembly.

The hydrodynamic force to which a boat hull is subjected in use can be considerable and such forces tend to impart longitudinal bending moments to the hull to cause sagging or hogging (the former being when the longitudinal bending moments put the hull into compression and the latter when such bending moments put the hull into tension).

By the present invention the convenience of manufacturing the hull from port and starboard sections and joining these sections together along the centre line of the hull enables the overlapping marginal edge portions of the hull sections to be utilised to provide a spine which reinforces the hull to resist the aforementioned sagging or hogging. Preferably the marginal edge portions of the hull sections are of shapes which cooperate with each other to lock the hull sections together when secured by bolt means (as hereinafter defined).For example the marginal edge portions may be of or include substantially trough formations so that the troughed marginal edge portions of the port and starboard hull sections overlap in the athwartships direction when viewed in plan to co-operate with each other by the trough portion of one section engaging with the trough portion of the other section to provide along the centre line of the hull a longitudinally extending channel on one side of the hull and a longitudinally extending ridge on the other side of the hull. Such channel and ridge can extend uniformly over the length of the hull but usually their crosssectional shape will vary to conform with the desired profile of the hull.The ridge formed by the overlapping troughed marginal edge portions preferably protrudes outwardly of the hull, particularly along the keel of the hull so that such ridge presents the appearance of a convention keel structure. The overlapping troughed portions will usually be joined together by bolts, screws, rivets or other convenient means (hereinafter referred to as "bolt" or "bolt means") disposed in a vertical plane and at positions spaced longitudinally over the length of the hull. It is desirable that the assembled marginal edge portions are sandwiched between inboard and outboard (inner and outer) pressure plates through which the bolts engage.These pressure plates may serve to provide a firm location for the bolts and are desirably profiled to form a complementary fit with the marginal edge portions, for example within the aforementioned channel and over the aforementioned ridge whereby the pressure plates can resist deformation of the marginal edge portions and provide reinforcement thereto. The pressure plates are conveniently formed as plastics or metal mouldings and in a preferred embodiment are made by pulltrusion techniques in polyester resin having an appropriate reinforcement such as continuous filament glass, carbon fibre, woven fabric or the like.

As an alternative (or in addition) to securing the overlapping marginal edge portions together by bolt means such edge portions can be secured together by welding or fusion techniques. Such welding or fusion is preferably arranged to form a continuous seal along the length of the overlapping marginal edge portions.

On the underside of the hull the ridge which is preferably formed by the overlapping marginal edge portions of the hull sections along the centre line of the hull will usually be provided with a protective keel band such as a removably secured aluminium alloy extrusion which is conveniently secured to one of the aforementioned pressure plates. Similarly, a bow capping, for example of rubber or other resilient material, can be secured over the aforementioned ridge along the stem. At the stern or transom of the hull the overlapping portions of the hull sections can be encased within an outboard casing, formed for example in stainles steel plate, which conveniently carries appropriate rudder hangings.A protective keel band and bow capping are conventional for small hulls and the overlapping marginal edge portions of the hull sections are preferably contoured in their longitudinal extent to provide a rebated portion in the stem of the hull so that the bow capping when fitted will provide a smooth transition to the keel band.

The hull of the present invention is particularly useful in small class sailing boats and as such can be provided with a daggerboard slot. This is conveniently formed upon assembly of the port and starboard sections by previously locating appropriately elongated apertures in the marginal edge portions of those hull sections to that such apertures are in overlying relationship to define the daggerboard slot in the athwartships extent of the overlapping marginal edge portions when the hull sections are joined together.

The daggerboard slot will usually be located on the centre line of the hull and in a keel portion thereof and can be further defined by inboard and outboard (inner and outer) pressure plates, conveniently pre-formed by injection moulding or casting, which are bolted to the hull and profiled to follow the contours of the ridge or other formation that may be presented along the spine of the hull.

The bolt means by which the hull sections are joined together also conveniently serve to secure boat component or fittings with the hull, such components or fittings comprising for example stern and side benches, flooring, mast steps and a daggerboard casing all of which are conveniently pre-formed such as by injection moulding in plastics material.

The aforementioned components or fittings can be additionally secured within the hull by engagement or co-operation with appropriately located protruberances or channels formed integrally with the hull sections.

Sealing means will usually be provided between the overlapping marginal edge portions of the hull sections when such portions are not welded or fused together. Such sealing means can be integrally formed with one or both of the edge portions, for example by providing ribs which are deformed under pressure to provide a sealing effect as the marginal edge portions are bolted together.

Usuall however the sealing means will be provided by a mastic or other sealing material which is disposed between the overlapping marginal edge portions.

One embodiment of a boat having a hull constructed in accordance with the present invention will now be described, by way of example only, with reference to the accompanying illustrative drawings, in which: Figure 1 is a side elevation of the boat in longitudinal section taken along the centre line of the hull; Figures 1A, 1B and 1C respectively illustrate details indicated at 1A, 1B and 1C in Fig. 1; Figure 2 is a plan view of the boat showing the starboard side of the centre of the hull; Figure 3 is a sketch showing a perspective view of the boat in section to show the port side of the centre line; Figure 4 is a perspective view of the underside of the boat;; Figures 5 to 12 are lateral or athwartships sections through the boat on either the port or starboard sides of the hull centre line and illustrate the profile of the hull and boat fittings at stations 1 to 4, 6, 7, 11 and 12 respectively indicated in Figure 2; Figure 13 is a lateral or athwartships section of a detail of the hull illustrating the formation of a gunwale; Figure 14 is a plan view of the stem portion of the hull of the boat; Figures 15 and 1 5A are respectively a longitudinal sectional side elevation and plan of a detail of the hull of the boat and illustrate a transition region between the stem and keel portions on the centre line of the hull;; Figures 16 and 1 6A are respectively a longitudinal sectional side elevation and plan of a detail of the hull of the boat and illustrate a transition region between the bottom and transom portions on the centre line of the hull at the aft end; Figure 17 is a detail of the hull and illustrate a transverse athwartships section through a daggerboard slot provided in the keel portion and along the centre line of the hull; Figure 18 is a detail of the hull illustrates a transverse or athwartships section through the joint between port and starboard hull sections in the keel portion, and Figure 19 is a detail of the hull and illustrates a lateral or athwartships section through the joint between port and starboard hull section in the transom.

The boat illustrated is of the smaller sailing class and has a hull I assembled from a port hull section 2 and a starboard hull section 3 each of which is preformed in plastics material by injection moulding. The hull sections 2 and 3 have fore and aftwardly extending marginal edge portions 4 and 5 respectively which, in assembling the hull 1, are joined together in overlapping relationship and in the athwartships direction when viewed in plan along the centre line 6 of the hull; such joint of the portions 4 and 5 extends over the length of the hull through a stem portion 7, a keel portion 8 and a transom 9.

Other than in the structure of the marginal edge portions 4 and 5 the port hull section 2 substantially mirrors the starboard hull section 3; the portions 4 and 5 however are shaped so that when engaged one with the other in overlapping relationship they form a fore and outwardly extending spine or ridge 10 which protrudes outwardly of the general profile of the hull 1 and is particularly evident along the keel portion 8. This spine 10 in addition to providing a conventional and aesthetically pleasing appearance to the hull also serves to reinforce the hull against longitudinal bending particularly when the boat is subjected to sagging or hogging.

The marginal edge portions 4 and 5 overlap horizontally in the athwartships direction when the hull is in its normal horizontal disposition and the design of these portions changes within the length of the hull. In particular in the keel portion 8 the edge portions 4 and 5 are of substantially trough formation as is best shown in Figure 18 whereby the trough portion 4 is received in substantially complementary manner within the trough portion 5. In the stem portion 7 between the keel portion and the step head 11 the edge portions 4 and 5 are of overlapping plate formations (as shown in Figure 14) and the outwardly protruding spine is maintained (but to a considerably lesser extent than that along the keel portion 8) by appropriately dog legging or joggling the shape of the outer side portion 5 to receive the inner side portion 4 in substantially complementary manner.The transition in the design of the marginal edge portions from the trough formations on the keel portion 8 to the plate formations on the stem portion 7 is effected at a dog-leg or joggle region 19 of the spine which dog leg orjoggle also forms a rebate in the stem portion of the spine 10 (see Figures 1 and 15). The edge portions 4 and 5 also pass through a transition phase between the keel portion 8 and the transom 9 (see Figures 16 and 16A) in which they progressively convert from their aforementioned trough formations in the keel portion into overlapping plate formations in the transom. As will be seen from Figure 19 the outwardly protruding spine 10 is maintained over the height of the transom 9 and the overlapping plate formations of the edge portions provide a substantially box-like appearance to the spine.

To assemble the hull 1 the two hull sections are located adjacent to each other with the edge portions 4 and 5 correctly mated in athwartships overlapping relationship. Prior to such mating of the edge portions a layer of sealing material such as mastic 12 is located between the opposed faces of these portions. The two hull sections are then secured together by a plurality of bolts 13 which are longitudinally spaced on the centre line 6 and over the whole length of the hull. The bolts 13 extend between inner (inboard) and outer (outboard) pressure plates 14 and 15 respectively which sandwich the marginal edge portions 4 and 5. These pressure plates (which, for convenience of illustration, have been omitted from several of the Figures) provide a firm location for the bolts and additionally strengthen the spine 10 against sagging and hogging.It is pre ferred that the pressure plates 14 and 15 are shaped to fit in substantially complementary manner against the marginal edge portion 4 or 5 with which they respectively engage; this is clearly shown in Figure 18 whereby the plate 14 is trough shaped to be seated within the troughed portion 4 and the plate 15 is saddle-shaped to follow the ridged profile of the troughed portion 5 on which it is seated.

By so shaping the pressure plates 14 and 15 these plates, when bolted together, reinforce the marginal edge portions against distortion so that the ridge effect of the spine 10 is maintained. The pressure plates 14 and 15 are pre-formed, such plates on the stem and keel portions conventionally being moulded in glass fibre reinforced plastics and such plates on the transom (indicated by the broken lines in Figure 19) conveniently being stainless steel plates of which the outboard plate can carry appropriate rudder hangings indicated at 16.A bow capping 17 (see Figure 1) pre-moulded in rubber or other resilient material is secured, for example by adhesive, bolts or self tapping screws, over the stem portion 7 of the spine and a replaceable keel band 18 (pre-formed, for example as an aluminium alloy extrusion) is secured (conveniently by an interlocking fit as shown in Figure 18 and screws) to the underside of the pressure plate 15 along the keel portion 8.

The rebate 19 between the stem portion 7 and the keel portion 8 provides a seating in the stem for location of the bow capping 17 so that the external surface of this capping is substantially continuous with the outer face of the keel band 18 (see Figure 1A). This maintains the aesthetic lines of the bow and 'provides a smooth transition between the bow capping 17 and the keel 18.

As is conventional for sailing boats, the hull 1 is provided with a daggerboard slot 20 for location of an adjustable daggerboard 21.

The slot 20 (see Figure 17) extends longitudinally on the centre line 6 of the hull in the keel portion 8 and is formed by overlying apertures 22 and 23 which are respectively provided in the athwartships extent of the overlapping marginal edge portions 4 and 5.

The apertures 22 and 23 can either be moulded integrally with the hull sections 2 and 3 or cut into such sections subsequent to their formation. The provision of the daggerboard slot 20 will cause a local variation in the profiles of the edge portions 4 and 5 as compared with the profiles of the adjacent part lengths of those edge portions in the keel portion 8; consequently the inner (inboard) and outer (outboard) pressure plates are shaped in accordance with the profile of the spine 10 in the region of the daggerboard slot as indicated at 14a and 15a in Figure 17. The pressure plates 14a and 15a can be discrete mouldings which provide a smooth transition with the adjacent pressure plates 14 and 15 and are secured together by bolts 13a.These plates 14a and 15a have appropriately located apertures for the daggerboard slot 20 and the outer pressure plate 15a is provided on its underside face with a protective plate 24; this latter plate is conveniently formed by an aluminium alloy casting and is secured by self tapping screws 25 to the plate 15a to provide a smooth transition to the adjacent ends of the keel band 18 which is interrupted by the daggerboard slot (see Figure 4).

The bolts 13 and 13a additionally serve as a convenient means for securing inboard (inner) boat components to the hull 1 such components comprising, by way of example, a first floor portion 26 with integral side benches 27 and a mast, pillar or tabernacle 34 (Figure 1); a second floor portion 28 with integral side benches 29 and daggerboard casing 35 (Figure 10); a third floor portion 30 with integral side benches 31 and optionally an aft hatch 32 (as shown in Figures 1, 2 and 11) or a stern bench 33 (as shown in Figure 3), and mast steps 36 and 37 (the former being intended for setting a cruising mast and the latter for setting a racing mast) as shown in Figure 1. From Figures 9 and 10 it will be seen that auxilliary bolts 38 can be used to secure the floor portions 26 and 28 to the hull at positions spaced laterally from the centre line 6. Advantageously the aforementioned inboard (inner) components together with such other components as may be required such as hatch covers, bulk head and compartment walls, thwarts and the like are pre-formed by moulding in plastics material for subsequent assembly of the hull, The fittings can be secured, or additionally secured, to the hull by attachment to protruberances such as channels or ribs which are moulded integrally with the hull sections 2 and 3, examples of such ribs or channels are indicated at 39 in Figures 5 to 10; the fittings can be secured to the ribs or channels 39 by, for example, an interlocking fit therewith, by welding, fusion, rivets, adhesive or screw means.

In moulding the port and starboard hill sections 2 and 3 the peripheral edges remote from the edges 4 and 5 are formed as channel-like sections 40 to provide gunwales; the mouths of the gunwale channels open outwardly of the hull and are closed by protective rubbing strips or buffers 41 which are conveniently formed as plastics or aluminium alloy extrusions and each is secured as an interlocking fit and by screws with its respective hull section (see Figure 13). The gunwale channels are reinforced against vertical loading by vertical webs 42 which are longitudinally spaced within such channels.

As shown in Figure 10 the inboard underside face of the gunwale channel 40 provides a convenient location on which to secure a thwart 45; to resist deformation of the gunwale channels by such loading as may be applied thereto from the thwart, webs 46 (see Figure 13) are provided at longitudinally spaced positions over the hull sections.

To complete the hull structure a transom cap 43 is fitted to the upper edge of the transom and a capping 44 is fitted to the stem head.

It will be realised that the present invention can be applied to the manufacture of hulls or hull-like parts for boats having multi-hull structures as for example, a catamaran, a trimaran or a cathedral hull structure; with this in mind the centre lines of the respective hulls will not necessarily coincide with the fore and aftwardly extending centre lines of the boats or of the multi-hull structures or of the multi-hull-like parts structures and consequently the term "boat hull" as used throughout this specification is to be interpreted accordingly.

WHAT I CLAIM IS:- 1. A boat hull comprising an assembly of port and starboard pre-formed hull sections, fore and outwardly extending marginal edge portions of which are joined together with overlap substantially on the centre line of the hull and wherein said marginal edge portions overlap in an athwartships direction when viewed in plan and are shaped and joined together to form a longitudinally extending spine which reinforces the hull against longitudinal bending.

2. A boat hull as claimed in claim 1 in which each of the starboard and port sides is substantially constituted by a single preformed hull section.

3. A boat hull as claimed in either claim I or claim 2 in which the hull has stem and keel portions and a transom and the longitudinal extending spine extends substantially along the centre line of the hull over the said stem and keel portions and the transom.

4. A boat hull as claimed in any one of the preceding claims in which the longitudinally extending spine protrudes outwardly from the general profile of the hull.

5. A boat hull as claimed in any one of the preceding claims in which sealing means is provided between the overlapping marginal edge portions.

6. A boat hull as claimed in claim 5 in which the sealing means comprises a layer of sealing material located between the overlapping marginal edge portions.

7. A boat hull as claimed in any one of the preceding claims in which the marginal edge portions are joined together by welding or fusion techniques.

8. A boat hull as claimed in any one of the preceding claims in which at least part of the marginal edge portions are of substantially trough formation whereby the troughed marginal edge portion of one section engages within the troughed marginal edge portion of the other section.

9. A boat hull as claimed in claim 8 in which the troughed portions are received one within the other in substantially complementary manner.

10. A boat hull as claimed in either claim 8 or claim 9 when appendant to claim 3 in which the marginal edge portions in the keel portion are of troughed formation.

11. A boat hull as claimed in any one of the preceding claims in which at least part length of the marginal edge portions are of substantially plate formation.

13. A boat hull as claimed in claim 11 when appendant to claim 3 in which the marginal edge portions in the stem and transom portions are of substantially plate formation.

13. A boat hull as claimed in any one of the preceding claims in which the overlapping marginal edge portions are joined together by bolt means disposed substantially along the centre line of the hull and at longitudinally spaced positions.

14. A boat hull as claimed in claim 13 in which the bolts engage between inboard and outboard (inner and outer) pressure plates which sandwich the spine.

15. A boat hull as claimed in claim 14 in which the inboard and outboard pressure plates are substantially complementary to the portion of the spine with which they respectively engage.

16. A boat hull as claimed in either claim 14 or claim 15 when appendant to claim 8 in which the inboard pressure plate is seated in substantially complementary manner with a channel formed by the troughed marginal edge portions and the outboard pressure plate is seated in the form of a saddle on a ridge formed by the troughed marginal edge portions.

17. A baot hull as claimed in any one of the preceding claims and having a daggerboard slot located substantially along the centre line of the hull and in the athwartships extent of the overlapping marginal edge portions.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. channel-like sections 40 to provide gunwales; the mouths of the gunwale channels open outwardly of the hull and are closed by protective rubbing strips or buffers 41 which are conveniently formed as plastics or aluminium alloy extrusions and each is secured as an interlocking fit and by screws with its respective hull section (see Figure 13). The gunwale channels are reinforced against vertical loading by vertical webs 42 which are longitudinally spaced within such channels. As shown in Figure 10 the inboard underside face of the gunwale channel 40 provides a convenient location on which to secure a thwart 45; to resist deformation of the gunwale channels by such loading as may be applied thereto from the thwart, webs 46 (see Figure 13) are provided at longitudinally spaced positions over the hull sections. To complete the hull structure a transom cap 43 is fitted to the upper edge of the transom and a capping 44 is fitted to the stem head. It will be realised that the present invention can be applied to the manufacture of hulls or hull-like parts for boats having multi-hull structures as for example, a catamaran, a trimaran or a cathedral hull structure; with this in mind the centre lines of the respective hulls will not necessarily coincide with the fore and aftwardly extending centre lines of the boats or of the multi-hull structures or of the multi-hull-like parts structures and consequently the term "boat hull" as used throughout this specification is to be interpreted accordingly. WHAT I CLAIM IS:-

1. A boat hull comprising an assembly of port and starboard pre-formed hull sections, fore and outwardly extending marginal edge portions of which are joined together with overlap substantially on the centre line of the hull and wherein said marginal edge portions overlap in an athwartships direction when viewed in plan and are shaped and joined together to form a longitudinally extending spine which reinforces the hull against longitudinal bending.

18. A boat hull as claimed in claim 17 in

which the daggerboard slot is partly defined by inboard and outboard pressure plates joined together by bolt means extending through the hull sections.

19. A boat hull as claimed in claim 18 in which the outboard pressure plate which partly defines the daggerboard slot is profiled to engage in substantially complementary manner with the outboard profile of the overlapping marginal edge portions in the local vicinity of the daggerboard slot.

20. A baot hull as claimed in any one of claims 17 to 19 when appendant to claim 3 in which the daggerboard slot is located in the keel portion.

21. A boat hull as claimed in any one of claims 14 to 16 when appendant to claim 3 in which the transom has an outboard pressure plate on which is located rudder hangings.

22. A boat hull as claimed in claim 3 or in any one of claims 4 to 21 when appendant to claim 3 in which a protective keel band is carried by the keel portion of the spine.

23. A boat hull as claimed in claim 3 or in any one of claims 4 to 23 when appendant to claim 3 wherein a protective bow capping is carried by the spine over the step portion.

24. A boat hull as claimed in claim 23 in which the stem portion of the spine is rebated from the keel portion and the bow capping is located within the rebate to provide a substantially smooth transition from said capping to the keel portion or to a keel band carried by the keel portion.

25. A boat hull as claimed in claim. 2 or in any one of claims 3 to 24 when appendant to claim 2 in which the port hull section and starboard hull section substantially mirror each other at least other than in the region of the overlapping marginal edge portions.

26. A boat hull as claimed in claim 2 or in any one of claims 3 to 25 when appendant to claim 2 in which the port and starboard hull sections have integrally formed gunwale channels along their marginal edges remote from the overlapping edge portions and which channels open outwardly of the hull.

27. A boat hull as claimed in claim 26 in which the gunwale channels are internally reinforced against vertical loading by longitudinally spaced arrays of webs integrally formed with the hull sections.

28. A boat hull as claimed in either claim 26 or claim 27 in which the gunwale channels are closed by pre-formed strips secured to the hull sections.

29. A boat hull as claimed in any one of the preceding claims in which the hull sections have integrally formed therewith inboard (inner) protruberances or channels for the location of inboard components.

30. A boat hull as claimed in any one of the preceding claims in which the hull sections are pre-formed in plastics by injection moulding.

31. A boat hull as claimed in claim 1 and substantially as herein described with reference to the accompanying illustrative drawings.

32. A boat having at least one hull as claimed in any one of the preceding claims.

33. A boat as claimed in claim 32 when appendant to claim 13 wherein inboard (inner) components are secured to the hull by said bolt means.

34. A boat as claimed in either claim 32 or claim 33 when appendant to claim 29 in which inboard (inner) components are secured to the hull sections in engagement with the protruberances or channels on those sections.

35. A boat as claimed in any one of claims 32 to 34 in which inboard components secured to the boat hull are pre-formed plastics mouldings.

36. A sailing boat as claimed in claim 32 and substantially as herein described with reference to the accompanying illustrative drawings.

37. A method of manufacturing a boat hull which comprises pre-forming port and starboard hull sections each of which has a fore and aftwardly extending marginal edge portion which is to be located substantially along the centre line of the hull to extend athwartships thereof; assembling the hull sections together with the marginal edge portions overlapping each other in an athwartships direction when viewed in plan, and joining said marginal edge portions together so that they form a longitudinally extending spine which reinforce the hull against longitudinally bending.

38. A method as claimed in claim 37 which comprises pre-forming the port and hull sections so that said sections substantially mirror each other at least other than in the region of the marginal edge portions.

39. A method as claimed in either claim 37 or claim 38 which comprises locating sealing means between said overlapping marginal edge portions prior to joining said portions together.

40. A method as claimed in any one of claim 37 to 39 which comprises joining the overlapping marginal edge portions together by bolting between inboard and outboard (inner and outer) pressure plates.

41. A method as claimed in any one of claims 37 to 40 which comprises joining the overlapping marginal edge portions together by welding or fusing by the application of heat thereto.

42. A method as claimed in any one of claims 37 to 41 which comprises pre-forming the port and starboard hull sections with, at least in part, trough shaped marginal edge portions and assembling the hull sections together so that the troughed marginal edge portion of one section is located with the troughed marginal edge portion of the other section and the spine protrudes outwardly from the general profile of the hull.

43. A method as claimed in any one of claims 37 to 42 which comprises pre-forming the hull sections by injection moulding in plastics.

44. A method as claimed in any one of claims 37 to 43 which comprises pre-forming a single port hull section and a single starboard hull section and assembling both said sections together to constitute the hull.

45. A method of manufacturing a boat hull as claimed in claim 37 > and substantially as herein described.

46. A boat hull when manufactured by the method specified in any one of claims 37 to 45.