epoxy Sanding

Discussion in 'Boat and Accessory Building' started by Tobin, Dec 20, 2018.

  1. Tobin

    Tobin Paddler

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    How important is it to get every last little bit of shine off the epoxy on the hull before varnishing? Are very small spots going to show once the varnish is applied? Thanks.
     
  2. Astoriadave

    Astoriadave Paddler

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    Worse, the varnish may not stick properly to those shiny areas.

    Some questions:
    Are you wet sanding or dry sanding?
    By hand or using a power sander?
    What grit have you been using?

    If you have thoroughly sanded the boat, working your way down from 80 grit to 220 grit or perhaps even 400 grit, the surface should be plenty smooth enough to varnish. Wet sanding from 100 grit down through finer grits helps remove sanding dust. A wash with warm soapy water followed by a clean water rinse will reveal any shiny spots.

    If there are only a few, and they are not deep, you can eliminate them by gentle wet sanding with 220 grit, perhaps followed by a fine 3M pad, gently rubbed, wet. Clean each area with water and dry it until the shiny spot is gone. This method will leave small shallow depressions, and after varnishing, a careful eye will spot them. If this will bother you, then you will have to use a block hand sanding method, wet, with 220 grit, to get rid of the spots.

    Be sure there are NO pinholes through the epoxy to bare wood. These will eventually leak, even if the varnish initially covers them, and water will get under the epoxy, leading to dark spots of rot.

    Hope this helps. Post back. Lots of others here will have helpful advice.
     
    JohnAbercrombie likes this.
  3. Tobin

    Tobin Paddler

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    Thanks Dave, that is what I thought. I have been wet sanding with 120 and just have some more persistent spots of raised epoxy that I should probably use some 80 grit on to get down through. Then back to the finer grits should do it I think.
     
  4. JohnAbercrombie

    JohnAbercrombie Paddler

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    Dave's answer pretty much 'nailed it' - the same as I would have said, but better! :)

    It's the 'dips' that are difficult for me, the 'bumps' are pretty straightforward. As long as you get the 'shine' off , working with water and rinsing- even with Scotchbrite working into dips- the varnish should stick OK.
     
  5. Astoriadave

    Astoriadave Paddler

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    Tobin, what John said: those bumps should yield quickly to 120 grit, wet sanded if you are using a sanding block. Some like to go as far down the grit size to 400 grit, to get a really smooth finish on the varnish. If you stop at 120 grit you will not have a super glossy finish. I usually stop at 220 grit.
     
  6. Roy222

    Roy222 Paddler

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    Tobin,
    It is a little more complex, not much, then Dave outlined. The best answer should be based on your craftsmanship objectives.Roughing up the low spots is like putting lipstick on a pig, Compound surfaces are tricky because the surface is easily over worked. You should fair the surface quickly with heavy grit. Do not give the low spots special treatment. The danger, of coarse, is cutting thru the high spots into glass. Is you had a lot flow spots I would apply another layer of epoxy.

    Fix it as soon in the process. A finishing issue is usually only get harder in the later process. The low spots should of be sanded out in bare wood.