Best UV protectant ...

What is the best UV protectant for Carbon hulls? I have a cover and it is stored in the garage, or as my wife calls it the “boat house”. However there are times out in the sun, so what is the best UV protectant to apply to the hull.

Don’t know of comparison data.
On my composite boats, I’ve switched to a 3M paste wax, designed for boats, and claiming UV protection. 3M also claims the stuff has unusual bonding properties.

Previously I used 303 or McNett, but I don’t think they stay on the hull as well as wax.

Note that there is controversy as to whether wax, or 303, will make the boat faster or slow it.

Does your carbon boat have a gelcoat outer layer? If so, the gelcoat absorbs UV damage before it can get to the structure.

If the carbon cloth shows through (no gelcoat or some kind of clear resin toplayer), don’t worry about the carbon itself. Sun will not damage it. It is the vinylester or epoxy resin that is susceptible to UV damage. That’s what you’re trying to protect with some kind of UV sunscreen.

I thought the carbon fibers were susceptible to UV.

No, they’re inert. Of course that black
will absorb heat, but I don’t know any case where a carbon boat has delaminated because it sat in the sun.

but epoxy isn’t
it’s highly susceptible to uv degradation. unless it’s a specific formulation with an inhibitor, but even these can’t last long, as far as i know. needs a uv sacrificial layer

3M stuff is the best. Starbrite is pretty decent too. But 3M stuff does bond to it chemically and stays on longer as well. I have used it for 10 years and zero need for restorer products so far. If you have NO gel coat or any other protection whatsoever then make sure you keep it protected at all times and out of sun whenever not necessary

Paint is the best
Wax doesn’t hold a candle to paint. Most Carbon Sailboats are painted for just this reason.

I’m wondering why you need it though. If your storing it inside and the rest of the time it has a cover. How many years is it going to take to get even 2000 hours of sun exposure?

I think you might be able to skip the wax too. 303 is a lot faster to apply.