Gel-coat and ultraviolet

Here is my question: Given a long period of time (say 25 years), how would a fiberglass canoe made of cloth and polyester resin with a polyester gel-coat in white handle being stored outside (assuming it is upside down on racks)?

I understand gel to get a bit “chalky” at first. Is this the extent of the problem, or would the sun eventually weaken it structurally?


Don’t know much about gelcoat, but
it seems resistant to UV. We have a '73 Moore that has been in partial sunlight and it does not seem the worse for it.

The structural layers are protected from UV by the gelcoat. There should be no problem if the inside of the canoe (with the structural layers) is protected by inversion from UV.

Another possible source of damage, for polyester canoes, is inappropriate use of a tarp. I had a MR canoe develop hydrolysis blisters all over the gelcoat, and I suspect the cause was having a tarp directly in contact with the gelcoat. Any tarp should be kept off the hull.

Vinylester is probably superior to epoxy in UV resistance. Vinylester and epoxy are virtually immune from hydrolysis.

use some car wax occassionally
and it will last even longer.

Chalky gel coat
I have a boat that has that but also some of the gel is starting to crumble. The boat has been outside some twenty years and has had the seats and thwarts replaced.

What I do not know is how much gel will further crumble if I hit a good rock. Its a kevlar flatwater boat.

We have been able to alleviate some of the chalking by buffing with rubbing compound… and removing the oxidation.

If it’s outside, keep it shaded
Suspend a tarp over it or something similar.Just keep direct sunlight off of it and it will last almost indefinitely. Gelcoat repair over an entire hull is a major pain (or expense if you don’t DIY), so save yourself some grief by protecting the boat.