QUOTE (John Williams @ Sep 4 2009, 04:29 PM)

All fiberglass laminates are semipermeable, that is why boats get blisters (delaminate)
I don't think this is a real likely scenario for our eggs.
Yes, fiberglass sitting
in water can be semi-permeable, and "soak up" water after a time, and this can be a cause of blisters. But I can't see how that would apply to a typical fiberglass camper that sits in air, with only the occasional water casually on the surface.
Okay, this is probably boring and basically applies to boats and not campers, but here is my understanding of it:
Essentially, when there is a lot of hydrostatic pressure on a boat's hull (i.e. it is floating in the water), then water molecules can permeate the 'glass. Not all the way into the boat though (that would have to be an incredibly extreme case; I have not see one). What happens is the water molecules seep in through the gelcoat to the first layer or so of glass (or sometimes deeper in more serious cases), and then they combine with some chemical parts of the resin to make a new liquid, and this liquid has larger molecules than the water did. So it can't pass out through the same microscopic holes that it came in through. Hence the new fluid builds up inside in the outer layers of the boat's layup and that is your blister. In the many many blistered boats I have seen or read about, I have not heard of one sinking because of it, although I suppose it is possible in isolated, extreme cases. This does not cause boats to take on water into the inside of the boat; it's a problem in the outer laminae.
On some (typically older) boats, the gelcoat is more permeable, so those boats don't tend to get blisters. The water still seeps in, and still combines with resins, but the new, larger-moleculed liquid can get back out, so no blister. Now theoretically this could cause a starved, weak layup, but that would take a long time, and again, the boat would have to have the hydrostatic pressure of being submerged in water (which a camper is not).
But back to the camper issue, if someone does have an area of thin or permeable or damaged fiberglass, the way to fix it, in my opinion, would be to laminate a new layer or two of epoxy or Vinylester resin impregnated fiberglass cloth on the inside. That would be a "permanent" fix, and would strengthen the camper shell (which, if it's weak enough to let water in, might need some beefing up anyway). In fact, this would almost certainly result in a repair that was stronger than the original (and either of these resins are superior to the polyester our campers were built with).
Likewise a crack could be repaired with new cloth and resin. It wouldn't have to be from the inside, but cosmetically that would be much easier.
In summary, I would still think that 99% of people's leaks would be through fittings and hardware, and for those few that have fiberglass problems, fixing them with new fiberglass would be the way to go.
I'm sure everyone is

by this point!
Raya