Dynarawr/Dynasoar: Fiberglass PVC Foamie Truck Expedition Camper

You are on the right track. Subframe for the fiberglass structure, bolt the subframe to the metal chassis and insulate the subframe to the chassis by rubber or springs. Hard points can be coosa board but use anti compression bushings and fender washers. If floor is not too thick, you can use marine plywood as hard points. Others use solid fiberglass as an alternative and fender washers instead of regular washers.

Once you have the subframe dimensions posted, I can make some estimate on thickness and lam sched.

 

More on the roof.

I have not used 50mm core. I have to believe the crown would be at the mercy of the rigidity of the core some at that thickness.

As for the walls, you also need hardpoints for the lifting on the corners. And this may lend itself toward matching lumber and the core thickness. The 20mm corecell or 20mm dried lumber would work well. This lends itself to using a 20mm core for the walls. If you buy 20mm wall core; doubling it would make the crown work better for the roof at 41mm with glue bond.

And you need to consider what forklifts may do to your rig; they can be so destructive. This may mean making the bottom from a higher density core all around is wiser for a camper you expect to be tossed about on a ship.

 

Insulation and structure are two different things. Price out 50mm PVC foam, then you understand. It's much simpler to build the structure with the minimum amount of materials, then use PU or PS foam to achieve the desired insulation value.
The grid on the roof I would make as top hat stringers, laminated over PU formers, with high density inserts for the solar panel mounting points. The space between the stringers you can fill with insulation foam. Solar panels should be ventilated anyway for performance, you get the air gap for free.

Your box halfs alo need lips all around, they perform several functions, stiffening of the open perimeter, sealing the two halfs, indexing in the open and closed position.
You also need several captive linear bearing sets so the box halfs can slide without canting. Depending on overall design, they and/or the lips prevent the top half from rattling on the lower half and destroying it while you drive.
All of the above, including the locking hardware positions needs to be planned in advance so you don't decore half the panels to make mounting points.

As for fabrication, I maintain my point. You are going into a country with low labour cost, where boats are buildt. Rushing to do something now is not necessary, they have resin, fiberglass and laminators. All you need is foam, anything wich is special (high strenght bolts for example), high grade tools and consumables.