HMS Beagle wrote:
If you have the fiberglassing skills, do that. I never like plyood embedded in fiberglass, it is just a time bomb, particularly if it has any screws driven in (which is usually the reason for it). A non-embedded plywood backing pad can at least dry if given a chance.
When you say center seal, do you mean the seal between top and bottom that runs all the way around? That can be an ingress point, particularly the way they sealed them at the factory. The top overlaps the bottom, so if left that way it would never leak. But then they put a piece of trim on it, drill a million holes drive in a miilion screws (which used to be steel but they do use SS now), then seal the trim top and bottom with a fillet of silicone. The last bit is the coup de grace - usually the top fillet, being exposed to more sun and weather fails first, allowing the bottom seal to collect a pool of water behind the trim, which has no place to go but through the aforementioned million holes with rusty screws. Would have been much better to let the water run out the bottom, sealing the top (though the top seal is useless after a year or two).
I think it is practically no possible to reseal the actual overlapping seam, but also not necessary. Pull the vinyl trim strip, remove all the screws, seal the threads themselves with a good marine grade caulk as you drive in new SS screws. Clean all the failed silicone off the top and bottom of the trim and do not replace it. All the trim does is hide the screw heads, it has no sealing function at all.
This is so helpful. All I can say is thank you so much and if you ever come to Anchorage, AK you are welcome to park your rig at my place up on the hillside.