Protecting Epoxy from UV: Spar vs Clearcoat


LOVES Wooden Canoes
A PPG paint rep is sending me a quart of 2-part urethane auto clearcoat (DCU2042) to spray onto my next stripper rather than brushing on the usual five coats of spar varnish. A couple questions for paint gurus out there:

1. With my HVLP spray gun, I'll get about 4-5 mils dry film thickness with three sprayed coats of the urethane clearcoat. How does this compare to the dry film thickness obtained by brushing on 5 coats of a high-solids spar varnish like Epiphanes or Captains?

2. Is there some industry-standard scale for a product's UV-protective qualities? PPG tech support can give me no numerical value for the UV protection offered by 5 mils of their product. Likewise, spar varnish manufacturers seem to have no rating scale for UV protection obtained from actual testing of their products. If there's no standard, how do I know if I have enough thickness of the urethane clearcoat to fully protect the epoxy underneath?

Allo Gary. I am not an expert in painting but I would like to express an opinion concerning the spar varnish. I use Interlux Schooner varnish. It's for boats and it is the one with the most UV protection available made by Interlux. They do have regular spar varnish of course. Normally, the guys apply around 8 coats of Schnooner. I think we can rely on that. Well, I am quite sure there are guys on line who know a lot more. But anyway, I'll come back to you with some more info. So, have a nice day
Thanks Sandpiper

I checked out the Interlux website you quoted. Several of the Interlux varnish products for marine use are described as having UV inhibitors, but there doesn't seem to be any kind of rating scale for degrees of UV protection.

I'm leaning towards leaving my varnish brushes in their cases, discontinuing use of spar varnish, and spraying urethane clearcoat on my next cedarstrip canoe.

Good morning Gary. Just read your reply. Myself, I lean towards Interlux because they have been there a good period of time and they have a good reputation. Keep us updated on the results of urethane clearcoat not only on short terms but also long terms. It is always a good feeling to see the final result. I am sure you will enjoy. Talk to you later...................................Sandpiper