Box Skin, and trim 

Once the camper's frame was constructed, it was time to cover it.  The desired material needed to be lightweight but structural, hopefully with some insulating properties.  We eventually settled on a product from Crane CorTec called the "Encor" panel.  Encor is a fiberglass-reinforced structural foam available in various thicknesses and most any length and width combination imaginable (so long as it can be sent by common carrier.)

The steel camper frame was stripped of grease and primed on the outside edge of all tubing with a PPG epoxy primer.  The panels were then adhesively bonded into place and temporarily clamped with scrap wood.  The adhesive is a SEM product used in the construction and repair of today's automobiles.  When gluing two pieces of sheet metal together, mechanical separation results in base material failure before bond failure, so once it's glued, it's not coming off with an air chisel! 

The following two photos depict the installation of the skin...

After the box was completely skinned, holes were cut for windows, skylights, and storage compartments.  These openings were then prepped for primer and paint, as well as the remaining unpainted steel surfaces inside.  Everything was primed with epoxy and all exposed surfaces were covered in white PPG Concept single stage top coat.

With the paintwork complete, aluminum angle was cut and installed to protect all external corners and seams.  The trim was screwed in place using stainless steel fasteners, and also completely sealed with GeoCel tri-polymer transportation sealant.

To finish the general box construction, the entire structure was insulated with 2" closed-cell foam insulation, yielding a total value of R-20 when combined with the outer fiberglass-reinforced structural foam skin.