Sanding Epoxy

Hello all and Happy New Year,

As a first time builder, I'd be grateful for any advice on sanding the epoxy in preparation for varnish (interior) and primer (exterior). How aggressive should I be in sanding the epoxy and what grit sand papers are best ?

Many thanks !

 


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RE: Sanding Epoxy

Goal of sanding: Make a flat even surface while taking off the minimum amount of epoxy. You just want to bring the high spots down to the very top of the low spots.

The most important thing - most important - Epoxy dust is very dangerous. It gets in your lungs and does all manner of deadly things. A dust mask won’t cut it, a fine particulate respirator is what I use and it comes in handy for all kinds of things. A friend spent big bucks on a positive pressure filtered mask. To keep the stuff out of my house I take the boat out of the basement and sand outdoors. Then I drop my clothes in the washing machine, wait, that’s not the right order.

I start with 80 in a random orbit sander unless I’ve made a hash of the epoxy, then 60 but with much anxiety and gnashing of teeth and by hand.
At this point I make it a point to avoid sanding Any corners or edges. You can grind through 3 layers at an edge in less than a second. Keep your sander flat on the panels.

This is also a good time to break out your Carbide edged paint scraper. I have 3, one with a 2” flat blade one with a curved 2” blade and a detail scraper at 3/4”. The curved one is most useful as it lets you focus force on blobs and big runs while avoiding the surrounding epoxy.

Next to 120 and maybe 180 depending on how detail oriented or patient you are. Use these grits until the previous grit scratches disappear.

Still avoid the edges and corners.

Finish up with 220 and get the corners now. If you feel the need, go back to 120 for blobs at the corners but I almost never have to do that. Use the 220 until the scratches from 120-180 are gone. It’s a good idea to go over everything with folder paper under your fingers. You can feel irregularities better than see them.

You’re looking for a dull even gray with no bright bits. Those bits are low spots and will show under paint and varnish. Until you’ve made three trips, then they’ll disappear. Check your primer recommendations for final grit.

Saving the second most important thing for last: Compared to the rest of your boat sandpaper is Cheap! Change it often, worn out paper will cause you to make mistakes.

Have fun and congratulations!

RE: Sanding Epoxy

   Oh yeah, if you see the fiberglass weave Stop!

RE: Sanding Epoxy

Check the CLC Tips for Boatbuilders (tab at top of this page). This section (http://www.clcboats.com/shoptips/finishing-tips/varnished_kayak.html) is about prepping for varnish and applying the varnish.

Have fun,

Laszlo

 

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