Body Construction

There are four main ways to build a demountable camper, by far the most popular being the traditional timber frame/coach built method, which by pure coincidence also happens to be the cheapest and quickest. The frame is generally stapled, nailed  or screwed together then covered on the inside with thin plywood. Alloy or GRP panels are used to cover the outside with insulation material placed between them.  Unfortunately the frame itself creates multiple thermal bridges so condensation is pretty much inevitable no matter how good the insulation material is.  At one time nearly all coaches, caravans and motorhomes were built this way but these days you’ll only really find it used in budget built demountables.

To be fair this method still has it’s place and is especially popular in the US where campers are sold very cheaply and in vast numbers. You can walk into a dealer in the US and find a huge choice of new campers for as little as £10,000.  Naturally for that sort of money you wouldn’t expect much in the way of quality or longevity so with only modest expectations everybody is happy. Unfortunately by the time those campers arrive in the UK with shipping, import duty, VAT, technical upgrades to meet UK standards, importer’s margin etc the price (and therefore your expectations) might easily have doubled, and for that money you can have a nicely made European model.

The modernised version of this is the pressure ‘sandwich’ panel. There is usually still a timber frame but as the inner ply skin is now a stressed/structural part the frame can be smaller and lighter, perhaps only around the perimeter. Rather than  being stapled, screwed or nailed together, the inner skin, frame and insulation material for each panel is now assembled and glued together in a pressure press.  The completed panels are then screwed together to create the body.

The fully composite vacuum sandwich panel does away with timber altogether and typically uses GRP or Carbon Fibre for both inner and outer skins.  The panels are created entirely within a vacuum press or (in the case of carbon Fibre) an autoclave before being further bonded to each other to create the finished body.  As the structure and it’s component parts are all impervious to water even severely damaged panels can be repaired at leisure without fear of long term repercussions from water ingress.

The final method is GRP moulding. This method will be familiar to anybody involved in boating or yachting and is perhaps the most proven of the lot.  It requires by far the biggest initial investment but has a number of very real advantages and not being restricted to flat panels gives much greater freedom of design.

Each method has it’s pros and it’s cons.


Traditional coachbuilt with timber frame


Pros:

Easy & Cheap to build

Easy to make custom sized/shaped cabins

Cons:

Heavy

Poor strength to weight ratio

Poor insulation (frame creates thermal bridges)

Susceptible to leaks & rot


Sandwich Panel (ply inner wall/ with or without timber frame)


Pros:

Relatively easy &  cheap to build

Reasonably light

Reasonably strong

Well suited to mass production

Cons:

Poor insulation (frame creates thermal bridges)

Susceptible to rot in the event of damage or leakage


Fully bonded all composite panel (Carbon or GRP)


Pros:

Very light

Strong and durable

Very long life expectancy

Excellent insulation without thermal bridges

Not prone to leakage

No timber to rot.

Easy to repair & impervious to water in the mean time

Easy to make custom size cabins

Cons:

Expensive to manufacture


GRP moulded 


Pros:

Relatively light

Extremely strong and durable

Exceptional long life expectancy

Good insulation without thermal bridges

No possibility of leakage

No timber frame to rot.

Easy to repair & impervious to water in the mean time

Ideal for series production

Cons:

Expensive tooling and setup costs

Not possible to produce custom sized/shaped cabins


Vacuum infused GRP moulded (no current manufacturers):

Pros:

Incredibly lightweight

Potentially the strongest and most durable construction

Exceptional long life expectancy

Good insulation without thermal bridges

No possibility of leakage

No timber frame to rot.

Easy to repair

Well suited to series production

Cons:

Highly technical process requiring great skill for successful results

Low strength and poor integrity unless perfectly executed

Very expensive tooling and setup costs

Not possible to produce custom sized/shaped cabins