ceiling repairs
aj,
this is the second time I had to write this. The page bombed out when I submitted it last. So, here we go again.
If it is a 1976 camper then the ceiling beams are made out of wood, usually 2X3 studs so you can nail the ceiling back up. If the studs are dry rotted but still stirdy get some liquid nails for sub floors and glue the ceiling up first. Like the other poster stated, you can get the rib pieces to cover the seams. Again nail or use the liquid nails, it bonds like concrete. I use pine lattice that I found at Home Depot. It is 1/4" thick X 1" or 11/4" wide by 8' long. I used a brad nailer to hold it up and painted it with mildew resistant bathroom paint.
If the ceiling is stained pick up some Zinser Bin, the one with the red label. It is a white shelac that covers any kind of stain. Then paint the whole thing with mildew resistant bathroom paint or the like.
If the whole ceiling is too far gone, tear it out and replace with white tile board. A 4'X 8'sheet at HD is 10 bucks. It cuts easy with a circular saw with a laminate blade. Check to see it the studs are still good. If not, sister some new ones to the old so you have someting good to nail to. Use the same lattice as stated above to cover the seams and use quarter round for the edges. It will cover where the ceiling meets the wall plus it will help hold up the ceiling in the corners where you can't reach a stud.
Check out my little picture site if you want to see before and after pictures.
sp