23/11/2006 22:52 61-3-98901337 PATENT ATTORNEY SERV PAGE 05 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT ORIGINAL Applicant(s): RV IP PTY. LTD. Actual Inventor(s): Wayne Douglas Barrett Address for Service: PATENT ATTORNEY SERVICES 26 Ellingworth Parade Box Hill Victoria 3128 Australia Title: TRAILER MANUFACTURE Associated Provisional Applications: No(s).: 2005906462 The following statement is a full description of this invention, including the best method of performing it known to me/us:- 23/11/2006 22:52 61-3-98901337 PATENT ATTORNEY SERV PAGE 06 TRAILER MANUFACTURE This application is a complete application based on Australian Patent Application No. 2005906462 and the entire contents of that application and associated specification are incorporated herein by reference. 5 Field of the invention This invention relates to the manufacture of trailers, including caravans, and relates to the manufactured trailers Background of the invention In the past the manufacture of caravans has normally entailed manufacture of 1o many structural and body parts separately with these parts then being assembled and secured together For example, a structural chassis has been separately manufactured, and to this are assembled and secured the separately manufactured components such as floor pan support framing, floor panels, wall and roof framing, and wall and roof panels and mouldings. The manufacture, assembling and fastening of the numerous components 15 together can be a slow process and the assembly operations therefore contribute a very significant component of the manufactured cost of the final trailer or caravan. The manufacture of caravans from the structural and body components can also substantially limit practical and aesthetic design features of the caravan, or at least can. lead to significant greater manufacturing costs if design features are desired that complicate the 20 manufacture and/or assembly operations. The framing is often of timber and body panels of aluminium. Structural strength of the assembled caravan often is provided by internal fittings such as benches, wardrobes, shelving, wall partitions. For this reason internal fittings and their layout must be selected with. structural considerations in mind and vice versa. 2 Vhen used throughout this specification, references to manufacture of trailers is to be understood to encompass manufacture of caravans in particular and, unless the specific meaning is clearly intended, references to manufacture of caravans is to be understood to apply inure generally to other vehicle bodies such as mobile horne bodies 5 and other trailers. It is an object of the present invention to provide a method of manufacturing a trailer body which enables efficiencies in manufacture of the final trailer It is a further and preferred object of the present invention to provide a method of manufacture of a trailer body component which can enable reduction in the number of 10 component parts to be manufactured and assembled to produce the final trailer. It is a further and preferred object of the invention to provide a method of manufacture of a trailer body which provides a strong trailer body. It is a further object of the present invention in another aspect to provide a trailer or caravan having a body which is composed of less component parts and/or which can 15 be assembled and manufactured more efficiently. Summary of the invention According to the first aspect of the invention there is provided a method of manufacturing a trailer body component, the component comprising a base component which extends substantially the entire length of the trailer and which has a floor section 20 extending the entire length and the entire width of the trailer, and has wall sections which extend upwardly from peripheral areas of the floor section, the floor section and the wall sections being of a unitary integral construction, the method including the steps of providing a mould having male and female parts which define between them a mould cavity defining the conformations of the floor and wall sections of the base component; 25 locating fibre reinforcing materials within the mould cavity and using a resin transfer moulding (RTM) process to fill the mould cavity to form a fibre reinforced, resin matrix body shape; curing of the fibre reinforced resin matrix within the mould cavity; and subsequently opening and removing of the moulded base component of the trailer from the mould, wherein the male and female parts of the mould are manufactured mould 30 bodies each of which is made of a laminate of multiple sheets of medium density fibre board ("MOF") with the sheets being adhered together to form an MDF body of 3 sufficient size to define the required mould part, and wherein the manufacture of each of the male and female mould parts composes automatic machining of the respective MDF mould body by a CNC routing operation, the detailed design of the trailer body component being perfonned using a CAD program and this design in turn being used to 5 control the operation of a CNC router so as to create the respective profiles of the male and female mould parts. By lbrrming the base of the trailer including floor and wall sections as a unitary integral component extending the entire length and width of the trailer body, the entire trailer body may be capable of being assembled and fitted out for less cost than assembly 10 from numerous separately manufactured components performing the same function. The use of resin transfer moulding technology (or RTM) can enable sufficient structural rigidity to be provided in the manufactured base component without the need for separate trailer framework components. To achieve this the materials used for the reinforcing fibres and the resin matrix can be selected accordingly, and the required thicknesses and 15 conformation of the various areas of the base component can be determined and then provided in the design and construction of the mould. The floor and wall sections of the base component may be composed, either wholly or in selected areas thereof, of layers of different materials, at least one of which is a layer of the resin matrix. By thus forming areas of the base component to have a 20 sandwich construction, the desired structural and other physical properties (such as shape and weight) of the various areas of the base component can be predetermined and achieved. For example, areas can be provided having a sandwich construction with outer layers of resin matrix and a core layer of a foam material, such as a. polyurethane, urethane, PVC or other plastics material core. The core can have a honeycomb 25 construction. Alternatively or in addition core materials or inserts can include metal elements such as metal mesh., ribs, grids. The use of a sandwich construction can enable the base component to have sufficient structural strength and rigidity to avoid the need for internal components of the caravan fit out to contribute to structural strength. The 4 23/11/2006 22:52 61-3-98901337 PATENT ATTORNEY SERV PAGE 09 sandwich construction using RTM technology can enable the provision of radiused sections e.g. between the floor section and the wall sections, which provide substantial structural strength to the base component and to the completed trailer. In a preferred embodiment, the process includes providing in the mould cavity 5 predetermined conformations to define chassis sections of the moulded base component. For example, the chassis sections can comprise longitudinal chassis members extending substantially the entire length of the floor section of the base component. These longitudinal members may comprise continuous linear beams extending lengthwise of the floor section whereby the RTM process creates fibre reinforced resin matrix beams 10 providing longitudinal structural strength to the base component. This enables elimination of prior known separate longitudinal chassis structural beams. Likewise, the chassis sections of the moulded base component may include transverse members providing lateral structural strength and rigidity to the base component enabling elimination of such separate lateral, chassis elements used in the 15 past. The longitudinal members and lateral members together form the chassis sections of the base component and are integrally formed simultaneously with the remainder of the floor section and wall sections of the base component. In one possible and preferred embodiment, the base component includes moulded 20 integrally therewith a forwardly projecting towing section by means of which the finished trailer will he towed by a prime mover vehicle. The integral formed towing section may comprise for example towing members projecting forwardly of the floor section of the base component beyond a front wall section extending upwardly from a front edge area of the floor section, the towing members reaching a forward most towing 25 point where, in use, attachment of the final assembled trailer to the prime mover vehicle 5 23/11/2006 22:52 61-3-98901337 PATENT ATTORNEY SERV PAGE 10 will be made. The forwardly projecting towing members may define for example a generally conventional looking A-frame in top plan view, although these forwardly projecting towing members are formed integrally with and at the same time as the remainder of the base component. If desired, the forwardly projecting towing members 5 may comprise integral forwardly extending continuations of the longitudinal members of the chassis sections of the base component. In use of the base component manufactured according to the method of the present invention, a conventional wheel bogie assembly can be mounted to the chassis sections beneath the base component. For example, the longitudinal members of the 10 chassis sections may project downwardly below the general plane of the floor section enabling attachment of the wheel bogie, e.g. in conventional fashion analogous to prior arrangements for attachment of a wheel bogie to a separately manufactured structural chassis of a trailer. Extending around the top edges of the wall sections, preferably around the entire 15 perimeter of the wall sections which are continuous around the front wall, two side walls, and back wall of the base component, there may be provided a conformation for fitting with a complementary lower peripheral edge of an upper body component of the trailer body. That is, the base component may be manufactured as a unitary integral component for a caravan including floor and four walls with a particular conformation at their top 20 edges, and an upper body component of the trailer body can then be fitted thereon. The upper peripheral edges of the wall sections of the base component may have for example a moulded rebate formed integrally by an appropriate conformation of the mould cavity so as to closely fit with the complementary lower edge of the upper body component. The upper body component may be manufactured according to a method 25 substantially the same as the base component of the present invention. In particular, the 6 present invention in a second aspect may therefore provide a method of manufacturing a trailer body component, the component comprising an upper body component which extends substantially the entire length of the trailer and which has a roof section extending the entire length and the entire width of the trailer, and has wall sections which 5 extend downwardly fi-om peripheral areas of the roof section, the floor section and the wall sections being of a unitary integral construction, the method including the steps of providing a mould having male and female parts which define between them a mould cavity defining the confonnations of the roof and wall sections of the upper body component; locating fibre reinforcing materials within the mould cavity and using a resin 10 transfer moulding (RTM) process to fill the mould cavity to form a fibre reinforced, resin matrix body shape; curing of the fibre reinforced resin matrix within the mould cavity; and subsequently opening and removing of the moulded upper body component of the trailer from the mould, wherein the ma 1 e and female parts of the mould are manufactured mould bodies each of which is made of a laminate of multiple sheets of medium density 15 fibre board ("MDF") with the sheets being adhered together to form an MDF body of sufficient size to define the required mould part, and wherein the manufacture of each of the rnale and female mould parts comprises automatic machining of the respective MDF mould body by a CNC routing operation, the detailed design of the trailer body component being performed using a CAD program and this design in turn being used to 20 control the operation of a CNC router so as to create the respective profiles of the male and female mould parts. For manufacturing of the large scale base component and/or upper body component according to either aspect of the invention, the mould bodies (from which the male and female mould parts are made) are made of medium density fibre board 25 ("MDF"). The mould bodies are made of a laminate of many sheets of MDF, e.g. MDF panels 7 23/11/2006 22:52 61-3-98901337 PATENT ATTORNEY SERV PAGE 12 16mm thick, with the panels being adhered together to form a body of sufficient size to define the required mould part. The MDF body is then machined by the CNC router to create the respective male or female mould profile according to the design criteria established using the CAD program. 5 If desired, the machined surfaces of the MDF body can be coated to provide a more durable surface for repeated use of the mould part. in the RTM operations and/or to achieve a desired surface finish of the moulded component. For example, a fibre glass reinforced resin coating may be applied to the machined MDF surfaces. The references in the specification to the resin transfer moulding or RTM process 10 arc to be understood to include variations of that process including, for example, the "Light Resin Transfer Moulding" or LRTM process. The RTM process in general comprises the placement in the mould cavity of a reinforcing material, usually in the nature of a fibre material preform having the general shape of the mould cavity, followed by closing the mould, followed by injecting the resin matrix into the cavity through 15 multiple inlet sprues until the cavity, including interstices between the reinforcing material, is completely filled and resin matrix is seen emerging from exit sprues. Injection is then stopped and the resin matrix is allowed to fully cure in the mould cavity, or at least cure sufficiently to allow the mould to be opened and the moulded component safely removed without damage or deformation or distortion of the component. 20 The injection of the resin matrix into the mould cavity in the RTM process is carried out at relatively low pressure and/or a vacuum can be applied to the outlet sprues to achieve or facilitate filling of the mould cavity. The resin matrix injected is mixed with a curing agent or hardener or initiator shortly before injection. The curing can be effected by operation of the curing agent or 23/11/2006 22:52 61-3-98901337 PATENT ATTORNEY SERV PAGE 13 can be accelerated for example by application of heat (or by UV radiation if one of the mould components is translucent to UV). The fibre reinforcing material located in the mould cavity can be of any suitable material (glass or other ceramic fibres, polymer fibres, aramid fibres, carbon fibres, etc.) 5 and can comprise continuous strands or filaments, or reinforcing material in the form. of fabrics or cloth or roving or mats, or reinforcing material in the form of individual long fibres or short strands. Choices amongst these known alternatives depend on the structural requirements, physical and chemical properties, as is known in relation to RTM technology. Likewise, suitable resins for the matrix can be chosen for chemical and Io physical properties desired, cost and availability, etc. Resins known to be useable in RTM processes include polyester, epoxy, phenolic, and acrylic resins. As is also known in the moulding technology field, other fillers can be incorporated to meet chemical, physical, aesthetic, cost criteria. As described above, the processes of the present invention may also include 15 forming at least parts of the base and/or upper body components to have a sandwich construction. The core materials of such sandwich construction areas can be foam or honeycomb or grid or mesh elements located in the desired positions within the mould cavity before injection of the matrix so that the matrix encloses the core materials. For example, areas of the final manufactured body components may have a foam material 20 core sandwiched between inner and outer layers of fibre glass. According to a third aspect of the present invention, there is also provided a trailer, particularly a caravan, which is manufactured according to a method according to either the, first or second aspect of the present invention so as to have a base component and/or an upper body component of a unitary integral construction including respectively 25 a floor or roof section and wall sections extending integrally therefrom. 9 23/11/2006 22:52 61-3-98901337 PATENT ATTORNEY SERV PAGE 14 Description of drawings Possible and preferred features of the present invention will now be described with particular reference to the accompanying drawings. However it is to be understood that the features illustrated in and described with reference to the drawings are not to be 5 construed as limiting on the scope of the invention. In the drawings: Fig. I is a side view of a caravan according to an aspect of the present invention, Figs- 2 and 3 show side views of base and upper components of a caravan similar to Fig. i, Fig. 4 is a transverse section through the base component of Fig. 2 along the line 10 IV-IV, Fig. 5 is a perspective view of a base component manufactured according to an aspect of the present invention, Fig. I is a side view of a caravan according to an aspect of the present invention, Fig 6 is a plan view of a base component of a caravan, 15 Fig. 7 is a transverse section along the line 7 - 7 in Fig.6, Fig. 8 is a section of the towing section with steel support member, Fig. 1 is a side view of a caravan according to an aspect of the present invention, Fig. 9 is a section at line 9 - 9 1 Fig. 8 Fig. 10 is a plan view of part of a towing section of Fig. 8, 20 Fig. I I is a section along line 10 -10 in Fig, 10 Fig. 1 is a side view of a caravan according to an aspect of the present invention, Fig 12 is a section through a join line of uper and lower trailer sections, Fig. 13 is a section through the upper component at a window site as moulded, Fig. 14 is a section like Fig 13 through the upper component with a window 25 installed, i0 23/11/2006 22:52 61-3-98901337 PATENT ATTORNEY SERV PAGE 15 Figs. 15 and 16 show a door mounting in one of the trailer components. Description of preferred embodiments The illustrated trailer body has a base component 11 which extends substantially the entire length of the trailer and which has a floor section18 extending the entire length 5 and the entire width of the trailer, and has wall sections 17 which extend upwardly from peripheral areas of the floor section, the floor section and the wall sections being of a unitary integral construction. The manufacturing method includes the steps of: providing a mould having a mould cavity defining the conformations of the floor and wall sections of the base component; locating fibre reinforcing materials within the mould cavity and 1o using a resin transfer moulding (RTM) process to fill the mould cavity to form a fibre reinforced, resin matrix body shape; curing of the fibre reinforced resin matrix within the mould cavity; and subsequently opening and removing of the moulded base component of the trailer from the mould. By forming the base of the trailer including floor and wall sections as a unitary 15 integral 'component extending the entire length and width of the trailer body, the entire trailer body may be capable of being assembled and fitted out for less cost than assembly from numerous separately manufactured components performing the same function, The use of resin transfer moulding technology (or RTM) can enable sufficient structural rigidity to be provided in the manufactured base component without the need for separate 20 trailer framework components. To achieve this the materials used for the reinforcing fibres and the resin matrix can be selected accordingly, and the required thicknesses and conformation of the various areas of the base component can be determined and then provided in the design and construction of the mould. The floor and wall sections of the base component may be composed, either 25 wholly or in selected areas thereof, of layers of different materials, at least one of which 23/11/2006 22:52 61-3-98901337 PATENT ATTORNEY SERV PAGE 16 is a layer of the resin matrix. By thus forming areas of the base component to have a sandwich construction, the desired structural and other physical properties (such as shape and weight) of the various areas of the base component can be predetermined and achieved. For example, areas can be provided having a sandwich construction with outer 5 layers of resin matrix and a core layer of a foam material, such as a polyurethane, urethane, PVC or other plastics material core. The core can have a honeycomb construction. Alternatively or in addition core materials or inserts can include metal elements such as metal mesh, ribs, grids. The use of a sandwich construction can enable the base component to have sufficient structural strength and rigidity to avoid the need 10 for internal components of the caravan fit out to contribute to structural strength. The sandwich construction using RTM technology can enable the provision of radiused sections e.g. between the floor section and the wall sections, which provide substantial structural strength to the base component and to the completed trailer. In a preferred embodiment, the process includes providing in the mould cavity 15 predetermined conformations to define chassis sections 41 of the moulded base component. For example, the chassis sections can comprise longitudinal chassis members 42 and 42a extending substantially the entire length of the floor section 18 of the base component. These longitudinal members may comprise continuous linear beams extending lengthwise of the floor section whereby the RTM process creates fibre 20 reinforced resin matrix beams providing longitudinal structural strength to the base component. This enables elimination of prior known separate longitudinal chassis structural beams. Likewise, the chassis sections of the moulded base component may include transverse members 43, 43a providing lateral structural strength and rigidity to the base 12 23/11/2006 22:52 61-3-98901337 PATENT ATTORNEY SERV PAGE 17 component enabling elimination of such separate lateral chassis elements used in the past. The longitudinal members and lateral members together form the chassis sections of the base component and are integrally formed simultaneously with the remainder of 5 the floor section and wall sections of the base component. In one possible and preferred embodiment, the base component includes moulded integrally therewith a forwardly projecting towing section 31 by means of which the finished trailer will be towed by a prime mover vehicle. The integral formed towing section may comprise for example towing members 45 projecting forwardly of the floor 10 section of the base component beyond a front wall section 19 extending upwardly from a front edge area of the floor section, the towing members reaching a forward most towing point 55. where, in use, attachment of the final assembled trailer to the prime mover vehicle will be made. The forwardly projecting towing members may define for example a generally conventional looking A-frame in top plan view, although these forwardly 15 projecting towing members are formed integrally with and at the 'same time as the remainder of the base component. If desired, the forwardly projecting towing members 45 may comprise integral forwardly extending continuations of the longitudinal members 42 of the chassis sections of the base component. In use of the base component manufactured according to the method of the 20 present invention, a conventional wheel bogie assembly 13 can be mounted to the chassis sections beneath the base component. For example, the longitudinal members of the chassis sections may project downwardly below the general plane of the floor section enabling attachment of the wheel bogie, e.g. in conventional fashion analogous to prior arrangements for attachment of a wheel bogie to a separately manufactured structural 25 chassis of a trailer. 13 23/11/2006 22:52 . 61-3-98901337 PATENT ATTORNEY SERV PAGE 18 Extending around the top edges of the wall sections, preferably around the entire perimeter of the wall sections which are continuous around the front wall 19, two side walls 18, and back wall 15 of the base component, there may be provided a conformation 16 for fitting with a complementary lower peripheral edge 20 of an upper body 5 component 21 of the trailer body. That is, the base component may be manufactured as a unitary integral component for a caravan including floor and four walls with a particular conformation at their top edges, and an upper body component of the trailer body can then be fitted thereon. The upper peripheral edges of the wall sections of the base component may have for example a moulded rebate formed integrally by an appropriate 10 conformation of the mould cavity so as to closely fit with the complementary lower edge of the upper body component. The upper body component 21 may be manufactured according to a method substantially the same as the base component of the present invention. In particular, the present invention in a second aspect may therefore provide a method of manufacturing a 15 trailer body component, the component comprising an upper body component which extends substantially the entire length of the trailer and which has a roof section 22 extending the entire length and the entire width of the trailer, and has wall sections which extend downwardly from peripheral areas of the roof section, the roof section and the wall sections being of a unitary integral construction, the method including the steps of 20 providing a mould having a mould cavity defining the conformations of the roof and wall sections of the upper body component; using a resin transfer moulding process to fill the mould cavity to form a fibre reinforced, resin matrix body shape; curing of the fibre reinforced resin matrix within the mould cavity; and subsequently opening and removing of the moulded upper body component of the trailer from the mould, 25 14 23/11/2006 22:52 61-3-98901337 PATENT ATTORNEY SERV PAGE 19 In the drawings it will be seen that the wheel arches 13 or receiving therein the ground engaging wheels of the trailer bogic are formed in the same moulding process. The wheel arches are integrally formed of fibre reinforced resin matrix material so as to form part of the unitary construction of the base component. Likewise the recessed step 5 14 formed at the caravan doorway is part of the same integral unitary construction. It will be appreciated therefore that many other areas or profiles or sections of the base component and/or upper body component can be likewise formed in the moulding operation, e.g. the recess 12 in the back wall for receiving a spare wheel for the caravan. However the windows shown in the upper body component can be separately 10 manufactured and can be fitted into the appropriately shaped holes cut in the desired positions to suit the aesthetic and functional criteria depending for example on the fit out arrangement within the caravan as described later in relation to Figs.13 andl4. As illustrated in Fig. 4, the floor section of the base component can have longitudinal structural members formed by integrally formed ribs projecting downwardly is from the plane of the main area of the floor section. These longitudinal members can constitute longitudinal structural members contributing rigidity to the floor section, thereby defining integral chassis sections. Suitable means may be used for mounting of the wheel bogie thereto- The integral longitudinal members (and lateral members as seen in Fig. 5) forming chassis sections enable elimination from the caravan construction of a 20 separate manufactured chassis assembly. The longitudinal members and/or lateral members can be solid reinforced beams moulded integrally (e.g. with reinforcing fibre preforns or reinforcing rods or bars laid in the relevant elongated mould cavity channels) and extending below the plane of the floor section. In Fig. 1, the forwardly projecting towing section 31 can be seen. This is formed 25 integrally with the base component, e.g. by extending the longitudinal members 42 below 15 23/11/2006 22:52 61-3-98901337 PATENT ATTORNEY SERV PAGE 20 the floor section beyond the front wall 19 so as to extend to the forwardmost point where a conventional coupling for connecting the caravan to a vehicle can be provided. Referring to Fig. 6 there is shown a workable design of base component and its integrally formed chassis sections comprising longitudinal beams 42, 42a and transverse 5 beams 43, 43a. The overall length of the base component may be about 7 metres. The stouter chassis beams 42 may be formed integrally with the floor section 18 by locating within linear channels of the female mould part which defining the beam chassis (i) fibre reinforcing webs, mats, strands, or the like and (ii) a formed core whereby the resin matrix permeates through the fibre reinforcing in the RTM process and encapsulates the 10 core. For example, multiple layers of suitable fibreglass reinforcing can be provided, selected from "double bias" fibreglass mats (DB mats) which have alternating fibre strand directions in successive layers forming the mat, unidirectional glass fibre mats (e.g. BE or UNT fibreglass mats of, say, 900g per square metre weight), chopped strand fibreglass mats ("CSM" mats), or preferably combinations of these types- to form the 15 multiple layers. The core may comprise for example PVC foam (e.g. "H80" PVC foam of 80kg per cubic metre density). The smaller dimensioned longitudinal and transverse beams 42a, 43a may be of similar constitution but have less layers of reinforcing mats as well as a smaller foam core. The floor section may be formed (integrally with the beams in the RTM process) of a laminate comprising surface or skin reinforcing mats formed of 20 layers of CSM, BE, and DB mats, a H80 core, and further DB and BE mats at the opposite surface so that the resin matrix penetrates through the fibre reinforcing and forms an integral laminate of glass fibre reinforced outer layers or skins and PVC core. The two main longitudinal beams 42 project beyond the front wall of the base section at 45 and taper towards each other to join at a point in the general vicinity where 25 the coupling to a prime mover will be provided together with a jockey wheel mounting 16 23/11/2006 22:52 61-3-98901337 PATENT ATTORNEY SERV PAGE 21 56, thus forming the towing section. The core and fibre reinforcing materials of the main longitudinal beams continue beyond the front wall up to and including the front coupling point so that the towing section at the front is anension structurally of the chassis. As shown in Fig.7 the top surface of each longitudinal chassis beam 45 has on the 5 outside and inside of the front wall 19 additional thickness fonned by wedge shaped inserts 46, 47. These inserts can be located within the female "A" mould or the male "B" mould, or a combination of both, so that these inserts are incorporated into the integral construction. These inserts can be formed of H80 foam core material and can also have reinforcing fibre materials layered along the surfaces so as to be incorporated in the resin 10 matrix forming surface layers or skin fon-ning surface layers or skin. The resulting thickened areas provide additional strength in this area where the towing frame meets and continues integrally with the chassis beneath the floor, e.g. so that the front wall is braced externally and internally in these areas. The thickened areas also are more aesthetically satisfactory. is Figs. 8 to 11 show a further possible configuration of and integral towing frame and with a coupling for the prime mover and jockey wheel mounting 56. In this alternative arrangement, there is provided a generally V-shaped steel reinforcing member 50 fixed to the undersurface of the integral projecting beams 45 forming the towing frame. Although not believed necessary for required strength of the towing frame, the 20 steel plate may nevertheless be necessary to comply with some obligatory standards for trailers, in particular some regulations which require safety chains used when coupling a trailer to a vehicle to be welded to a steel plate of the trailer's towing frame. To enable fixing of the V-shaped reinforcing member to the underside of the towing frame by the bolts 51 as illustrated, there may be moulded in each of the two main towing frame 25 beams a longitudinal metal bar 52, as shown in cross-section in Figs. 9 and 11. These 17 23/11/2006 22:52 61-3-98901337 PATENT ATTORNEY SERV PAGE 22 steel bars can be incorporated by locating them in the female "A" mould so that they became encased in the reinforced resin matrix beneath the foam core in the moulding operation. The fixing bolts can then be attached by passing upwardly through the V shaped reinforcing member through the bottom surfaces of the moulded towing beams 5 into the steel bars extending longitudinally within the beams. Fig. 12 shows a possible joining system for the joining of the base component of the trailer to the complementary upper body component which is different to the rebate configuration shown in Figs. 2 to 5. In this figure 12, the base component has an upwardly tapering profile 60 in cross-section formed around the peripheral edges of the 10 walls 12. The upwardly tapering edge is shown to have a complementary shape to a lower peripheral edge 61 of the walls 21 of the upper body component which has a downwardly concave shape in cross-section. The illustrated configuration with a V shaped concavity or notch 61 is preferred in the lower edge of the walls of the upper body component, and the inverted V-shaped tapered edge 60 in the edge of the walls of 15 lower body component because these complementary shapes can be moulded effectively, because the complementary shapes will facilitate alignment and, during securing of the components together, maintenance of alignment of the upper and lower body components, and, because, although believed unnecessary, the shape will promote fluid drainage or inhibit moisture penetration. In assembling the upper and lower body 20 components, a suitable bonding adhesive will be placed between the complementary profiles, such as an adhesive known as "Plexus" (trade mark). An additional bonding strip 62, such as fibreglass reinforced web, can be located and adhered over the join on the inside of the trailer body and a decorative cover strip 63 can likewise be located and adhered over the join line externally. i8 23/11/2006 22:52 61-3-98901337 PATENT ATTORNEY SERV PAGE 23 Fig. 13 shows a cross-section through a portion of a wall of the upper body component where a window is to be located. The inner and outer skins 72, 71 of the moulded body wall 21 sandwiching the foam. core meet and are joined together at the ternination of the core so as to pass around a removable plug 70 which is provided 5 within the mould (on the surface of the male or "B" part of the mould at the location where the window is to be provided. After moulding, and removal of the upper body component from the mould, the plug 70 is removed and the panel formed within the boundary of the plug will be cut and separated from the main wall leaving the edge profile 75 shown in Fig. 14 The removable plug can be reusable and preferably is 10 therefore precisely constructed and finished, e.g. being made of laminated ply, glass coated, painted and polished. Fig. 14 shows a window mounted at the concavity formed by the removable plug, the window comprising a glass panel 76 and a nylon piano hinge 77 fixed to the edge of the glass panel and to the inside surface of the concavity 74 formed around the removable plug 70 in the moulding process. A seal 79 is provided for 15 excluding rain, insects, etc. Figs. 15 and 16 show a section of wall of the trailer body (either upper or lower body component) having a contoured profile 80 surrounding a door opening, the profile being formed by inner and outer skins of the wall meeting at an end edge of the core and forming an inwardly stepped profile for receiving the door 81. The door is shown as 20 having a complementary profile to form together with seal members 82, a scaling engagement with the door opening. The door is shown as having several components (but not all these are necessary), these components comprising inside and outside skins 83, 84, a glass panel 83, a security panel or mesh 86 making forced entrance difficult, and a sliding or rolling blind 87. Th.e door is mounted to the wall by hinge pins 93 extending 25 through the integrally moulded lugs 91 formed on the outside skin of the door and 19 23/11/2006 22:52 61-3-98901337 PATENT ATTORNEY SERV PAGE 24 complementary lugs 92 forced on the outside skin of the wall. These lugs can be formed in the process of moulding the upper or lower body component with reinforcing material, such as the glass fibres within the inside and outside skins, being shaped before the RT'M process to continuously extend outwardly from the skin into the hinge lugs 5 This kind of door mounting -can enable strong and aesthetically pleasing hinged door mounting to the trailer. From the foregoing description and drawings it will be seen that the methods of the present invention enable the construction of a trailer, particularly a caravan, from a greatly reduced number of components compared to conventional trailer manufacturing 10 processes using separate structural frameworks, chassis, floor, wall and roof components and panels. The trailer construction can have its structural strength provided by the body component(s). The processes also can enable a great variety of aesthetic, aerodynamic, and other shape related functional effects or features to be provided, It may be possible to achieve substantial manufacturing, and particularly assembly cost savings compared to 15 conventional caravan manufacturing processes leading to enhanced profitability for manufacturers and/or cost reductions for customers. 20