I did a major floor repair on my Fiber Stream
As I look at your system, I am assuming the following:
- the fiberglass body rests on the frame member
- your floor sat on the frame member and butted up to the fiberglass body
unknown: how was your floor attached to the frame member (screws/bolts)
Cut a solid wood piece (not plywood) to slightly less than the thickness of the frame member.
Put fiberglass cloth and resin on that wooden filler piece, bringing it up in thickness to that of the fiberglass body.
Tape this finished piece to the frame member with masking tape (temporary only)
Cut a new plywood floor to fit on this extra piece and inside your fiberglass body
Coat the bottom of the floor with fiberglass cloth and resin
Place the floor in the trailer on the new support and inside the fiberglass body.
Attach the floor as before. I would screw the floor to the new filler piece as well, if standard flor attachments do not go to the frame member.
Fiberglass the inside joint between the body and the floor.
In my case, the floor was quite thin and flexed as I walked on it, so I fiberglassed the entire floor.
Undercoat the trailer floor with standard auto undercoat products.
Simple, isn't it!!