This is a familiar topic. The body or shell of most (or all) molded
fiberglass trailers is made by coating a mold with gelcoat and then using a chopper gun to spray in a layer of chopped
fiberglass strands. The shell pieces are then assembled, insulated and stiffened from inside using floor-to-ceiling cabinets, panels, posts, etc. Chopped
fiberglass strands form a layer that is not extremely strong, and eventually sags, bulges, and so on.
The
Boler 17 (I have looked at photos of many of them), after 40 years develops a sagging roof in the center only, between the forward and aft roof vents. The roof vents sag down noticeably toward each other. My
Boler 17 has this common sagging roof trait.
There is some good news. On my rear gaucho model, the road side roof area is held up by the floor to ceiling cabinets and bathroom. The curb side roof area is held up by two wrought iron kitchen cabinet supports. These areas of the roof are fine. Also the roof areas in front of the forward roof vent and behind the rear roof vent are fine. So only the center of the roof is sagging.
I have been considering the following options to correct the sagging roof. All of these methods require first jacking up the sagging roof area to its original form, then applying new material to the sagging area as well as the stable, supported side areas.
- Add a sturdy aluminum or steel roof rack with carefully located, spaced attached points. I'm not sure exactly how to execute this. It would increase wind resistance.
- Add wood or metal support, e.g., ribs below the roof. I have seen examples of this method. It would reduce ceiling clearance.
- Grind down existing gelcoat, then apply deck core material followed by fiberglass layers and finally gelcoat. Strong material such as biaxial fiberglass cloth could be used.
- Grind down existing gelcoat, then apply fiberglass layers, then gelcoat, i.e., skip the deck core material layer.
I like the last two options best, that is, beefing up the fiberglass shell. Its not clear whether a deck core material would be needed, or if that's overkill. Strong material such as biaxial fiberglass cloth could be used, and that would be far stronger and stiffer than the original chopped strand material.
Here's an example on youtube where two layers of biaxial fiberglass cloth were added to stiffen a too soft and bouncy boat deck that had been originally built using a chopper gun. This fixed the problem.
So what do you think? What would you do?