Body Construction

There are four main ways to build a demountable camper. The traditional way is the coachbuilt method of timber frame assembled with mechanical fasteners.  The frame is generally covered on the inside with thin plywood and with an alloy or GRP skin on the outside. Insulation material is placed between the skins but as the frame itself creates multiple thermal bridges condensation is pretty much inevitable.  At one time nearly all coaches, caravans and motorhomes were built this way but these days you’ll only really find it used in demountable campers.

The modernised version of this is the pressure ‘sandwich’ panel. There is still a timber frame but as the inner ply skin is now a stressed/structural part the frame can be lighter. 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 the timber frame altogether and typically uses GRP for both inner and outer skins, both of which are structural.  The panels are created entirely within a vacuum press before being  bonded to each other to create the finished body. There are variations on the theme using carbon fibre of aluminium alloy in place of GRP skins, but the principle and core advantages are the same.

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.

Before we move on to the pros & cons of the various methods above, perhaps we should have a quick look at the Chinese manufactured 4×4 and demountable campers recently appearing in the US and (to a lesser extent) here in Europe. They masquerade under various different brand names and as you might expect are aimed primarily at low cost/low quality markets.  Various manufacturing methods are employed including timber framed, alloy framed and GRP moulding, but all are focussed on rapid low cost production rather than meeting the demands of the end user they have no place in this discussion.

Returning to the main methods. Each has it’s pros and it’s cons.


Traditional coachbuilt with timber frame (popular with US, UK & Scandinavian manufacturers)


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 with timber frame (popular with large scale continental manufacturers)


Pros:

Relatively easy &  cheap to build

Reasonably light

Reasonably strong

Well suited to mass production

Cons:

Poor insulation (frame creates thermal bridges)

Structure susceptible to rot in the event of damage or leakage


Fully bonded composite sandwich panel (As Herman & Dutch Campers. Popular with high end expedition camper manufacturers)


Pros:

Light weight

Strong and durable

Very long life expectancy

Excellent insulation without thermal bridges

Not prone to leakage

No timber frame to rot.

Relatively easy to repair

Easy to make custom sized/shaped cabins

Cons:

Expensive to manufacture

Not well suited to mass production


GRP moulded (Example: Gazell)


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

Well suited to 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