I started to epoxy (with glass) first and apply a second 2K PU (marine grade) varnish coat. The varnish is more scratch resistant and adds UV protection to the epoxy.
thinking going resin research epoxy, Kiki kick .slightly thinned,no cloth,2 coats. Should hold up fine for my needs and look shiny. Don’t think the spar with lay up thick enough to get a good coat
Marine Spar Varnish. Going to be hard to find a good one in California. They have all been reformulated. The good one used to be McCloskey Spar Marine. Some of the ones that are better are made outside of California. I think you can still buy McCloskey, but you’ll have to order it and I don’t know if they will ship it to Calif. System Three makes one. You can order Sikens. I think they are out of Sweden. Their products are the best for exterior wood that I have ever used. Sikens Cetol in Natural Cedar is what I would use on it, if I could find it. It is a Varnish Stain that has an Amber color to it. The old varnishes were not clear and had an amber color to them. If you wanted to look authentic; the Cetol made by Sikens will make it look great. Two coats, sanded between with 220. Let the first coat dry several days before sanding. Wipe the sanded coat down with a painters tack cloth, then apply the finish coat.
i lived in a residence in front of ocean. All resident must use red sikens paint for roof strip, i did it, expensive product. I paint wooden shutter with an other product ( no rules for shutter) and i was surprise how well sikens resist compare to other product even if it was not a cheap one’s and shutter are far less exposed. Now i only use sikens product for exposed wood, never be disappointed.
on this board i would go with some layers of one of those new water diluated epoxy product that soak deep in wood (resoltech 1010 in europe) then finish with a marine grade varnish (sikens if they make one).
Interesting how contemporary the outline is on that paddle board. Alot of the racing paddle boards used today have similar outlines. Just checked online; Sikkens makes a “Cetol Marine Varnish”. Described as having a natural amber color, about $40 per quart.
Given the threaded bung, you could likely job up a simple rig to (gently) pressure test it after a coat or two of (whatever you use). That would prove the coating and offer an assessment where/whether you should do another.
if you go with epoxy you should use one’s dedicate to wood sealing. Water base marine epoxy primer can be diluted to a realy fluid mix for first layers that go deep in wood and have no recoating adherence problems. A big improvement for use of wood in boat building. Since i use one for sealing my compsand deck i have no more water sucking in wood skin.