Interesting Obsevation: Water content of GRP

[Nigel-in-Oxford]

3 Years ago I did a complete refit of a mobo, a 1965 Seamaster, from sunk for 2 years condition.
I put on a new gel-coat by using white topcoat (gel-coat with wax in).
Now The boat is bone dry inside, loose dust in the bilge dry.
It has been in the water 2years.
The new owner (2 years ago) had a survey last week, the surveyor detected very low moisture levels so much so that he checked his meter on an adjacent boat.
He kept saying "I cant believe this, its nearly 50 years old"

So what are we seeing?
Is topcoat even better than epoxy for keeping water out?
is the wax fooling the meter?
is the very dry interior allowing the water to evaporate?

I may try topcoat instead of epoxy next time it needs redoing.

 

[oldsaltoz]

Hi
Nigel-in-Oxford, The wax added to the flow coat makes it's way to the surface and enables the curing process to complete, I very much doubt any would still be there after 2 years in the water.

If the inside of hell has no treatment than it may be that's the rout the original moisture took to get out.

Then again, just how long was it out of the water being repaired, was the original outer layer removed? Was it undercover and well ventilated? Was it inverted?

Any or all of the above would contribute to improved drying prior to relaunching.

All very interesting though.

Good luck and fair winds.

 

[Nigel-in-Oxford]

Only out of the water for two years, and the original gel-coat just sanded smooth and keyed, not inverted. It was outside and only covered with a tarp.
I'd love to find out what happened as my current boat has raised moisture levels but no problems yet.

 

[jwilson]

The fact that it was 50 years old probably helped it dry out, older orthopthalic resins absorb water more readily than modern iso and vinyl ones, but equally well let it dry out faster, including from the inside. Or it could have been well dried prior to being sunk, either through long periods ashore or an "osmosis treatment"