Need help. Have to cut rectangle in skin. Slide in Furnace

[groundhogy]

Oh, due to the airstream body tapering in as it goes down, I had to shim up the back (part of furnace most inside the rv) of the furnace to bring in the bottom front edge to match the outside skin.

[tbashin]

[Should I spray construction foam between the inner and outer skins? Would this seal and prevent water from falling in there?[/QUOTE]

Nope. Foam is not water proof protection. It's a gap filler and insulator maybe but still needs to be sealed over. I do wish Airstreams were insulated with foam like the old Avions were.