Damp between GRP skins in coachroof sidesdoghouse

[Babylon]

Undetected hole in GRP coachroof (poor-fitting sprayhood-frame feet screws) has resulted in an unknown quantity of rainwater entering over time between the two skins - first evidence was headlining down inside of doghouse peeling away with moisture. Two questions:

1. How to first dry this area out? (I don't want to cover the holes yet as it surely needs to breath to dry, but its still letting in more rainwater!)

2. How to then reinforce the internal void with something a little more solid (say to 25mm below the surface) so that I can more securely screw or bolt the sprayhood-frame feet in place?

 

[Swinranger]

Babylon,
you need to determine the extent of the water penetration. If it is localised, you may be able to dry it out by drilling a series of holes in the inner skin and use a wet and dry vacuum cleaner to extract most of the moisture, then inject epoxy and patch the holes when it has fully dried out. If the sandwich has delaminated over a wide area, then you will probably have to remove the inner skin entirely and rebuild it.
I had this problem with my balsa cored coachroof, where the balsa had rotted away. I removed the inner skin and rotted balsa and epoxied 12mm hardwood strips to the outer skin which were then varnished, giving a very nice finish in the saloon and providing a solid base to bolt the fittings to.

 

[highandry]

Buy a length of clear small bore plastic tube, B&Q sell it in various sizes. Take the screws out and enlarge the hole if necessary, then replace with a short length of tube (say 3 inches?)and seal it in with a non permanent mastic. That will allow air in as in as in an air duct, but keep rainwater out.