Another Sanding Question...

Just got started with the sanding process on my Skua build. I'm planning to paint the hull and varnish the deck. I'm currently sanding the hull, and as expected there are a lot of tiny low spots that I haven't quite reached.

Before I continue I'd love a little advice from the group: am I sanding away all of the protection the epoxy gives? I'm starting to see the fiberglass n a few places, am I sanding away the glass? 

Any tips will be a big help. Thanks--


6 replies:

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RE: Another Sanding Question...

   There are more experts on this forum than myself with epoxies - but I had the same issues. To overcome them I did the following.

1. Stpooed sanding where glass showing - Applied another this layer of resin

2. Used a 220 / 320 WET sanding with good quality paper. 

3. Removed as little surface as possible to reduce the flaws

4. Added another thin layer of resin.

5. Wet sanded again.

This eventuntally gave me a smooth surface - but took time.

Wet sanding and good quality paper was the key for myself. 

Again - this is my first and others are more expert on this forumn.

RE: Another Sanding Question...

   Thanks! I've just given the rest of the hull a good going over, and I'm going to do another coat of epoxy this evening once it (hopefully) cools off a bit--

RE: Another Sanding Question...

Hi Bill,

I looked at your pictures.  Where you are starting to see the weave you should stop sanding.

If you continue to sand, you will sand further into the weave and eventually through the weave and you will then not have the strength benefit that glass brings to the construction process.

It is very typical that at this phase you will continue to have little dimples/low spots.  They can be filled by a final coat or two of epoxy and continued sanding to smooth out the additional coats.   But even with that, unless you are willing to make a large time investment, you will probably continue to find little imperfections like that and at some point you just move on as these are minor and will not be noticed.  For my final sanding I use 220 grit dry and just try to be careful.  I save wet sanding for paint or varnish.

When I apply those final coats of epoxy, I use a spreader which helps direct the epoxy into these low spots.  Overall, my assessment, based on your pictures, is that you are doing a good job with the sanding….just don’t overdo it.



RE: Another Sanding Question...

Thanks! I'm going to try to be more directed with my next coat of epoxy. I also picked up a scotch-bright yesterday and that helps with the tiny dimples.   

RE: Another Sanding Question...

I really recommend that for the painted part you use epoxy/microballoon mix instead of straight epoxy. It's lighter and much easier to sand than cured epoxy. If you use a long board to sand it by hand you can combine filling the weave and fairing the boat into a single step. Microballoons sand like a soft wood so I was recently able to take an 18-foot hull from unfilled glass to filled, faired and ready to paint in 6 hours of easy hand sanding with a single thick coat of microballoons.

They don't work for a varnished surface because of the strong color, so for the deck I used Duncan's general procedure but dry sanding with 220 the way Howard says. If you have big drips, you can use more aggressive paper. If you have enough experience sanding, you can use 80 grit for the drips, 120 for most of the rest of the smoothing and then 220 to get it ready for varnish.

Finally, wetting the epoxy with denatured alcohol will show you exactly what it will look like varnished. It will alo show you where you've sanded into the glass. If visible weave disappears after an alcohol wipe you're fine, still in the epoxy. If the weave stays visible, you're in the glass and should immediatelt stop sanding there. Adding another layer of epoxy  will seal the glass again, but that weave will always be visible unless you paint it or completely sand that spot to bare wood and apply a feathered patch (usually not worth the trouble). The spots in your pictures look as if you were just getting to the glass but not quite or barely into it.

Good luck,



RE: Another Sanding Question...

   For epoxy drips I've found that a detail hand scraper like the one from Lee Valley makes short work of them - much quicker than sanding.

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