ppettit said:
Hello All,
I just signed up to your forum today. I've been reading the post for awhile, and enjoy watching all these boats get fixed up.
So you guys would recommend Spar Urethane on Marine Grade plywood as well? This won't leach into the carpet or cause any problems against foam? I'm replacing a bass tracker floor and redoing the carpet.
Spar Varnish has been around for a long time and works pretty well. Some Spar Varnishes, but not all, have UV inhibitors; many will need to be sanded and reapplied, or re-coated, every few years. Using a paint over spar varnish has best results as almost all outdoor paints have good UV inhibitors. This way you can use a less expensive "porch paint" but still have good weather proofing and elasticity with the spar varnish. Carpet will also block UV degradation of the Spar varnish.
Spar Varnish is a very good choice for protecting wood that you want to leave brite finish on, IOW see the wood grain/pattern.
Spar varnish, or any other weatherproofing product, should not leech into the carpet once applied; just let it cure the right amount of time. It will also not react with the foam, again, just let everything cure before placing the different products into contact with each other.
I don't know if I would necessarily recommend it for your application, but it will work. Like all things concerning boats; weatherproofing is a compromise and, largely, a personal decision based on the final look you want on the hull and how much you are budgeting.
Good Epoxy will never allow water intrusion, put you need to be careful of penetrations (Screws, staples etc), it needs to be painted or pigmented for UV inhibition, it is more expensive but durable and has a nice finish.
Poly and Vinyl-ester resins are cheaper but allow water intrusion but otherwise are similar to Epoxy resin, best over composites not wood.
Thompson's-like water proofing is cheap and works well, but doesn't last as long as epoxy resin and you still need to be careful with penetrations and eventually it will need to be reapplied. How long? Maybe 10 years if taken care of I guess.
Outdoor paint, porch paint, will protect wood to a good degree; it is cheap, easily applied and easily found. It's not very durable and will need to be touched up, repaired or reapplied yearly. Many homebuilt row boats only have this as a protectant.
Topside coatings, like paint, steelflex or durabak, are designed to go over the sealant coating and are not very good as a stand alone sealant on wood; but are very good over metal and composites. They are durable, expensive and have a nice finish.