Has anybody gone the green route, ditched the resins and glass, and sealed up a board with linseed oil, danish oil, or tung oil? I know some people have done it with other boards, but I didn't know if anyone had given it a shot. I would think you'd want to go thicker on the deck for stiffness and make sure your seams are dead on (and maybe foam it up inside), but yeah, anyone tried it with a Timeless board?
Not as familiar with some of the other oils you mentioned, but I would be concerned of using tung oil. Ive finished a few other wood projects and overall it is great.....but nothing that would remotely take the abuse that a SUP would. The concern is that tung oil, once cured is prone to having those thin cracks (like spider webs) showing up in time. Im sure that would be prone to leaks. Second, if you are taking the "green route" you would need to watch it with tung oil anyway. Most of the tung oil that you purchase in any of the big stores is actually a synthetic, petroleum based blend.
I would also be concerned without glassing. I think that gives A LOT of support. There is actually a thread somewhere on this forum that states the same thing.You may consider an alternative with the chemicals, but don't cheat on the glass.
Lastly, if you use an alternate sealer, i would consider NOT using foam - venting instead. If water were to penetrate the sealer this would give you an opportunity to dry it out vs. the foam which would just rot and Im going to assume stink to high hell.
I asked myself the same questions before starting my build. I had some ideas ( shellac, lap joints, thicker wood...) on how to do It but I decided to go the "easy" way, glassing as everyone else.
You could look up epoxies made from plants, don't know If they really are that green but the companies claim they are ex : ecopoxy.com/ For my project, I chose a regular epoxy that is made locally, in some way, that's a bit greener choice too.
There's the matter of the $$ too, I am definitly not happy with the fact that the finising of the board cost more than the board Itself... +1 on not using foam, wouldn't be green anyway...