Epoxy sand through problems

Getting ready to paint and varnish my PMD and I have lost count of how many times this has happened to me. 

The instructions say to sand the epoxy until all the shiny spots are gone, but before I can get even close to  having all of the shiny spots gone, I have sanded completely through the epoxy in areas.

Meanwhile, immediately adjacent to the spots I sanded through are glaring shiny spots. Beyond frustrating.

Any suggestions?



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RE: Epoxy sand through problems

   Larger pic, may show the details better:

RE: Epoxy sand through problems

   So I'm not one the highly experienced builders that generally respond so take my thoughts with that context.  I'm finishing my second build, and I generally took a less stringent approach with the second build.  I started using a cabinet scraper this time which I found worked well to get drips or other high areas closer to the surface.  Then I could take a sander to get it smooth without working so hard at it that I cleaned off all the epoxy as you experienced.  For low areas, there are lots of techniques on fairing that you will have to wait for the others to respond.  However, I did have a pretty deep scratch that was due to a sawhorse failure.  I ended up taping around the area and every night after I had finished working, I would put some epoxy on the scratch.  I found after a few nights that it had evened up to the surrounding area and just sanded smooth.  Also, I found that the "errors" I had in my first build, really sort of just faded into background compared to the overall beauty of the boat.  So with this one, I've let some of those areas just be, and I chalk it up to my own personal warts that show the boat was handmade.  I'm trying in general to just enjoy the experience of this build whereas I stressed too much with my first build.


RE: Epoxy sand through problems

Thanks for the advice Scott, 

I have enjoyed the build so far, but I think I do need to step back and de-stress a bit. 

I'll try again tomorrow...hopefully I can get some good thickneses of epoxy on there and maybe not sand through this time. 



RE: Epoxy sand through problems

   "Meanwhile, immediately adjacent to the spots I sanded through are glaring shiny spots. Beyond frustrating."

It sounds like you simply dont have enough epoxy on there yet.

How are you applying the epoxy?

This is my technique:

  1. Fully wet out FG with spreader, squeegee off so there are no shiny spots and FG texture can be felt & seen
  2. Do your first fill coat WITH A BRUSH, within the recoat window. Lay it on as thick as can without it ending up on the floor. There will be some runs and sags. I do several laps around the brushing them out until its too sticky to be effective. You can feel the brush dragging, time to stop.  There should be no FG weave texture felt or visible.
  3. Let cure overnight at minimum.
  4. The next day visually inspect with light at different angles, and use your hand to find all the sags and runs. You may even find a little weave texture that you missed.
  5. Take a scraper to all the runs. Scrape each one until it widens enough to blend in to the adjacent area.
  6. Orbital sander, 80 grit. Go around the whole boat with the sander REMAINING FLAT on the surface. This is just a leveling passing to show you the low spots. Dont tilt it on edge to get the low spots or you will be chasing your tail forever.  Keep the sander off curves, edges, concave areas.  Keep an eye on where you are sanding. If you see ANY weave STOP. You should only hit in very few places, and it should look like 8 little dots, not a big white spot.
  7. You now have a map of your highs (dull white) and lows (glossy). You should be able to get the surface about 90% flat on the first fill coat, and it should be mostly solid white with shiny mottled speckles. Larger concavities and curves and edges should be QUICKLY scuffed by hand just for adhesion, not trying to remove material.
  8. Second fill coat, lay it heavy WITH A BRUSH. The surface should have a thick glossy layer (like a new guitar).
  9. If you had it 90% flat, let this coat cure and sand then sand again until totally flat. If you had significant glossy areas after the first sanding, do another coat within the recoat window to avoid an extra round of sanding.
  10. Scraping runs and sags before sanding is important because if you try to take them down with a sander, you will hit the glass in the adjacent areas first. The thickness difference is too great. If you had no runs and sags to begin with, you probably never had enough epoxy on.
  11. Spot filling a few stubborn areas may be necessary .

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