How long can you go without UV protection on fiberglass?

[jnb]

I'm building a GV 11 outside, I've got the outside of the hull glassed but not primed and painted yet. I usually leave the tarp off so moisture doesn't build up inside (inside isn't fully coated yet). I had some things come up at work, so it may be a few more weeks before I get time to apply primer.

I know that UV will eventually degrade unprimed fiberglass on ply, but don't have any sense of how long that will take. Is a few weeks of sun ok? Or should I put a tarp over it and take moisture as the lesser of two evils?

[fallguy1000]

Epoxy starts to degrade at about 3-6 months. You can sand off the chalk.

Tarp it with some standoffs. Like pool noodles.

[OneWayTraffic]

I’m currently building outside and have gone through the same thing. Epoxy degrades at a rate proportional to the UV it gets. You really don’t want any if you can help it. A shelter or a tarp with a uv stabilised plastic (acts like sunscreen) helps a lot. Aside from that some other things that would make a difference:

Pigment in the epoxy. WEST Aluminum powder would work as would graphite. This provides some up resistance. Al powder also increases hardness. Not good for fairing but fairing filler has colour itself. If nothing else the damage is kept to the surface of the glass.

UV resistant epoxy. For a small project this might be affordable. The resistance is limited but should be enough to build a boat much bigger than yours.

In your situation I’d rather put a frame over the boat to let air through. Or leave the tarp on if the boat is in direct sun. Take it off for an hour a day to air.

[jnb]

Thanks, guys. Got it under a tarp for now during the day and airing out at night.