BUYERS GUIDE - MOTORHOMES
If you’ve priced a built-up motorhome recently, you’re possibly still recovering from the shock. We’re not suggesting for a moment that the pricing isn’t justified in producing a skill and labour intensive end result, but there are quite a few of us capable of a DIY job.
The traditional method for producing a box-shaped motorhome or caravan body is using a wooden or metal frame, to which metal or fibreglass (fibre-reinforced plastic or FRP) sheeting is fixed externally and an inner liner of wood or FRP is fitted to the interior. That remans the process for many caravan makers today, but the road transport industry got away form that old-fashioned construction method many years ago.
All the refrigerated trucks and semi-trailers you see on Australian roads have employed inner and outer FRP sheets bonded to internal, closed-cell plastic foam since the 1970s. Originally, those composite foam-sandwich side and roof panels were bolted or rivetted to aluminium-extrusion vertical and longitudinal beams, but in recent years, modern adhesives have made the aluminium beams redundant.
There’s no need for any framing, because the sandwich panels have more than enough strength for automotive purposes. They’re simply edge-glued together.
Parallel with the development of modern adhesives that now stick boats, aeroplanes and spacecraft together, has been the implementation of computerised numerical control (CNC) cutting machines. These precision tools have the ability to cut almost any shape, including window, hatch and door cut-outs, in FRP sandwich sheets.
Once the plan has been completed in a computer-aided design / computer aided manufacturing program (CAD/CAM) the machine cuts it out of blank sheets with absolute precision.
Floor panels are also CNC cut, but are made of load-bearing composite material.
All the panels needed to male a camper trailer, caravan or motorhome body can be produced to plan in matter of minutes. Mind you, it’ll take more than a couple of minutes to put the resulting flat pack together and the put in pre-cut interior furniture and fittings, but that’s where the fun and the savings are!
There are several companies capable of producing such pre-cut panels, but the most active we’ve come across in aiding DIY people is Queensland-based StyroMAX.
This company has a planning process, to help guide your design to real-world practicality, including pre-fitted wiring and plumbing conduits. StyroMAX has also filmed many videos that show how the assembly process should be carried out, as well as detailed videos covering fit out, window, hatch and door installation.
StyroMAX use top-quality Dow Styrofoam (rigid extruded polystyrene) as a core and lightweight European FRP sheeting. This combination offers industry leading strength to weight ratios, the company says.
Dow’s Styrofoam is closed-cell, so it resists water and moisture penetration. It’s also a high-performance insulator, as its use in fridge truck bodies proves.
The StryoMAX panels are also UV stable, thanks to a top layer gelcoat that improves UV light and weathering resistance and they’re also easy to clean. Car wash and household cleaners can be used.
Curved roof panelling can be done by a special ‘routing’ process that lays successive grooves on the inner face of the panel that need to be curved. It can then be bent to the required radius before assembly, when the grooving is covered by an impermeable plastic sheet.
In addition, caravan-type entry doors, service doors, hatches and windows are available. Kits come with the required amount of Henkel Terostat MS939 adhesive for the build and there’s full back-up and support. Also, accident repair gel coat is always available.