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I've just launched into that project. Last done about 8 years ago, the varnish had essentially disintegrated anywhere these were stepped on. The thwarts, which were done 6 years ago (and also get stepped on a bit) instead look like new.

The little "feet" (cross-ties) had partially separated, and some of the nails/screws were beginning to stick up. This is true mainly for the aft set of them. The forward set, where shaded by the cuddy, has retained much of the varnish, and the feet are more firmly attached.

So far, I've taken apart the floor boards and sanded them to bare wood (on the top) and almost to bare wood on the bottom; the boards are extensively cracked on the bottom, and they are cupped, making it difficult to get existing varnish off, I'm hoping what I have is good enough to support what I want to put on.

I used a hot air gun and a scraper, that worked really well on the top to get most of the remaining varnish (PU) off. Then sanded with 60 and 80 grit. Alternatively, sanding with 40 grit also cuts through the varnish.

I discovered that the individual slats do not all sand to the same color wood and that they seem to have weathered differently. To even out the color, I'm using a stain on them. That seems to have been done before, because in places where there was original varnish still left, the bottom most layer had a distinctive hue. I chose "maple" as the stain color that seemed most likely to result in a more uniform color without being too dark.

The plan is to let that sit and cure well, then coat with SystemThree ClearCoat (3-4 coats) and then their Waterbased LPU (4 coats). The LPU should have enough UV protection and, if the thwarts are an indication, this should give me a reasonably long life-time.

I'm planning to epoxy coat the little feet separately and even put a layer of glass on the bottom, to prevent the coating from rubbing through. Not sure I want to glue them on. While permanent, it's too permanent, and would interfere with disassembly for recoating. Probably screw them back on, after reinforcing the holes with epoxy. For the extra fasteners that were added over time as the original locations failed to hold, may just glue in their heads, for optics.

Here are some pictures of the "before state":


Some graying due to weathering, some cracking, assorted collection of fasteners.

The original varnish seems to either have had a reddish brown tint, or it weathered that way; a later layer is more amber, and the top layer was almost clear. Where the original layer is intact, all the other layers continued to stick, with perhaps a little peeling around scratches, otherwise, despite treating the bare wood, none of the additional layers stuck to the wood.

Fasterners stick out:


Forward section, in the shade of the cuddy and not stepped on:


Underside: all coatings in perfect condition. No UV degradation and no scraping. But the wood was never fully planed/sanded, so it looks rough.

Here's an interim view. Boards are sanded to bare wood and treated with a stain ("maple"). The result almost looks like teak, but it does a good job of evening out the color differences -- however, even then, the individual slats are not perfectly matched, and curiously, their weights are very different. All had weeks of drying in the furnace room, so it's probably not different moisture content.


Note how despite the stain there's some variation in color among slats, but how the stain helps blend in discoloration from weathering near the fasteners.

I may have been a bit rash, or not, in using the stain. Oil stains are not the preferred stain under epoxy.

However, the story seems to not entirely be black and white. So, I've been doing some reading.

WEST SYSTEM has published a note on "Epoxy Adhesion over Stains", in which they report on some testing. This follows on an article in Epoxyworks 18, titled: "Varnish over Epoxy" which treats the entire concept of first treating wood with epoxy. A similar document from SystemThree is called "Clear Finishing of Outdoor Wood".

So, anyway, it seems that at least some of the oil stains tested were compatible with the epoxy, more so after extended drying. I don't think I can repeat their test, lacking both a sample of the same wood as well as some of the things they used. I did poke my nose into the materials safety data sheet for the one that failed their test and compared it to the one I am using. At least the formulations are different -- let's hope the difference goes in the right direction.

Also encouraging is the video from yet another epoxy manufacturer that describes techniques how to coat over oil-based stain; apparently the first coat is difficult to get even.

I checked, and it looks like I will be able to do some light scuff sanding without sanding right through the stain, so that's another thing I am planning.

Anyway, while I'm giving the slats a few more days to dry, the next step will be to do the little "feet", or cross ties. They are not big, but there are 22 of them. My plan is to add a layer of glass cloth to the underside, to deter rubbing through the finish. I found a small circular impression in the bottom surface of one of them, which makes me wonder whether these originally had small rubber pads. Most of them had been sitting directly, wood on fiberglass, on the bottom of the hull and are a bit worn away; so this one would have been one that didn't make contact and preserved that impression. Or, could be, it was the fact that it didn't make contact so that somebody at one point glued something underneath.

I thought about this problem when I first started working on my boat. I have all of the floorboards nicely sanded and stacked in a lumber pile… for the last six years. I guess my conclusion was to ignore the situation.

But really, the problem with epoxy encapsulation and the floorboards is all of the joints that are not glued together that work against each other every time you step on them to abrade the finish. Then of course they are subject to dirt and grit and heavy objects being dropped on them which could also make holes in the envelope. Add using an oil stain, which looks right for the job, but has questionable adhesion to epoxy and I really wonder if it's worth doing. I think I might just opt for old-fashioned spar varnish and except the yearly maintenance. It's not like you have to sand them down to wood every year you just have to scrape off where the varnish has lost adhesion, scuff sand the rest and put some more coats on.

I do think it's worth doing the epoxy for thwarts and coamings.

K.C.,

as the wood around the fasteners has deteriorated, I had to dissemble the floor boards completely. Therefore, the one problem I won't have is the issue with imperfectly sealed joints. My current plan starts with the cross ties. My plan is to give their bottom faces a layer of glass cloth (as they have been wearing away) and to fill all existing screw and nail holes with epoxy; then finish by sealing them. I'll apply a PU coat for UV protection, but they are generally in the shade anyway, so even if that rubs off where they contact the hull, the epoxy will be fine. The way I deal with the wear on the hull at the contact points is to use transparent gel coat from a repair kit. That stuff is easy to apply, cures in air and will take a few years to wear down.

For the slats, I'm still on the fence. I've not had good success with touching up varnish, and, once assembled, the spaces between the slats are difficult to get to. That said, I may not have used the correct varnish for the application on bare wood, you can see how earlier touch-up efforts were only successful where I hadn't taken the original varnish off to bare wood before.