Sanded into FG on deck (spots) - add epoxy or varnish?

I've almost finished sanding my wood duckling (I think I've been saying this for weeks now!) but managed to sand through the epoxy in a couple of spots near the chines on the sapele deck.  I did this once before and added another layer of epoxy to cover it up (and sanded back again).

It's pretty obvious that it would be unwise to add another layer of epoxy of comparable thickness and risk sanding through again (fool me twice...), so I think my options are as follows:

A. Before varnishing, add 1-2 THICK layers of epoxy (by NOT using a squeegee, which has been my habit but has obviously led to extremely thin coats) to cover up the spots where I sanded through and reduce the odds that they'll be visible through the varnish.  My duckling weighs 20 lbs, and CLC specifies a curb weight of 22 lbs, so maybe I went too light on the epoxy in general due to using the squeegee for nearly every application (with 6-7 coats on the deck, amazingly).

B. Go ahead with varnishing and live with a few blemishes.

I can't see the spots unless I get within 1-2 feet and look carefully.  I *just* sanded into the fiberglass (enough to see it; maybe 5 passes too many with 120 grit).  Will it be more obvious when I add varnish?  I guess this would be counterintuitive since I'd think the varnish would be a better match optically (refractive index) for both epoxy and fiberglass than air.  I'm torn because I'm out of patience but also don't want to get lazy with the finish line in sight.

Guy who's only gonna squeegee when wetting out the glass from now on

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RE: Sanded into FG on deck (spots) - add epoxy or varnish?

I guess option C might be adding a few epoxy "patches" only in the spots where I sanded too deep (and using a squeegee to keep them thin) and then sanding lightly, enabling a quick transition to varnishing.  The only thing that makes me nervous about this idea is that I ended up with a few dark runs of epoxy on the hull (presumably due to batch-to-batch mix mismatches in the epoxy/hardener).  I think spots of different colors on the deck would be worse than just leaving it as is.  I've been pretty careful about my ratios since then, though (using a measuring cup since my pumps are not reliably metered at this point), so I think this is unlikely.

Apologies for the essay - brevity in boatbuilding posts is not my strong suit!

RE: Sanded into FG on deck (spots) - add epoxy or varnish?

First, there's nothing wrong with your epoxying skills, it's the sanding you need to work on. Applying lots of thin coats with a squeegee instead of a couple of thick ones some other way is the best way to avoid runs, drips, excess weight and wasting epoxy. Don't change what worked. Work on what didn't.

Next, if you want to see what a glassed, epoxied and sanded surface will look like after varnishing, wipe it with a rag soaked in denatured alcohol. Whatever it looks like before the alcohol evaporates is what it will look like when it's varnished.

As to what to do:

1. If the alcohol test shows no visible glass, you're fine. You haven't really sanded into the glass. What you have is an optical illusion caused by a very very thin layer of epoxy over saturated glass. Proceed to varnish.

2. If the alcohol test shows whitish weave then you got into the glass. Cosmetically, that is what it will look like under the varnish, no matter what you do with additional epoxy layers. You are never going to be able to eliminate that without removing and replacing the abraded glass. You need to decide if you're willing to live with that or if you need to do some reconstructive work. Structurally it's sound and just needs a sealing layer of epoxy.

What I did with my boats when that happened is basically your option C - spot repairs with a thin layer of epoxy. A disposable foam brush is perfect for that. Then once it cures, be very very careful with the sanding. You may want to grab some scraps of wood and glass and make some corners to practice your sanding on. Keep monitoring your progress with alcohol tests.

The good news is that as long as you didn't sand through to the wood your boat's function and strength will be unaffected. This is all a purely cosmetic issue.

Good luck,




RE: Sanded into FG on deck (spots) - add epoxy or varnish?


Thanks very much.  I can't see the weave once I've put denatured alcohol on it (even under sunlight), so I'll stop sanding/coating the deck (phew!).

The only thing between me and varnishing/painting at this point is sanding down the border between the deck glass that I extended about 2" onto the hull (and the rest of the hull).  I didn't feather it enough initially and ended up with a really nasty transition (cliff, you might say) on those edges that was made worse by the fact that I added epoxy mostly to the tape (and not to the rest of the hull below).  I'm most of the way through sanding the epoxy back down into the tape (and maybe doing one last fill and light sand) to even thins out.  I'm sure it's stronger this way, but I'm kind of wishing I'd just trimmed the deck glass at the deck/hull intersection since it's been so much work (for me, at least) to clean it up.

RE: Sanded into FG on deck (spots) - add epoxy or varnish?

Glad to have helped head off a lot of useless sanding. As for your other problem, you are so much better off with the 2" overlap. Without it you would be chancing a leak right where you have a seam and two exposed edge grains. As it is, the seam is sealed and the deck glass is protected against peeling off.


RE: Sanded into FG on deck (spots) - add epoxy or varnish?

Yeah - I'm very glad to not have to go through the tedium of sanding the deck again - believe me!

I think I'll stop sweating small surface imperfections where the deck cloth overlap meets the hull.  On my latest (3rd) lengthy attempt at sanding the cloth edge (or at least the epoxy on top of it) down to feather into the hull, I sanded until the whole surface (across the glass cloth edge and rest of the hull) turned a uniform dull gray, so it's very nearly flat.  I can see the transition due to a small thickness difference in places (with denatured alcohol on top), but only if the light hits it just right, and in the real world the sunlight will hit the hull just right (to bounce back to the eye) approximately never.  Anyway...that's a purely subtractive process, so it's not that big a deal either way.  Maybe I'll have more patience in 12 days when I return to it.

Thanks again.  I added the bottom fillet (and another layer of epoxy) to the coaming today.  2-3 more hours of sanding the coaming and bits of the deck and hatch rim, and I will have emerged from my arduous journey through the Valley of Sand.

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