Removing Sufacing Agent

Discussion in 'Fiberglass and Composite Boat Building' started by helluvaboater, Nov 7, 2017.

  1. helluvaboater
    Joined: Jul 2015
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    Location: Maui

    helluvaboater Junior Member

    Doing some repairs, I sprayed my hull with polyester gelcoat with surfacing agent. Afterwards, I found some minor fiberglass defects that I need to fix. This means I will need to spray gelcoat again.

    What is the best/easiest way to remove the surfacing agent/wax layer so I can spray another layer of gelcoat?

    Is acetone enough or do I have to sand or wet sand?

    I prepped the fiberglass with 280 grit before spraying the gelcoat.....
     
  2. kapnD
    Joined: Jan 2003
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    Location: hawaii, usa

    kapnD Senior Member

    Spraying gel coat as a finish is a pretty ticklish process, but sounds like you have already found an acceptable method?
    The stuff needs to go on really thick to be tough enough to protect the fiberglass under it.
    I wouldn’t think sanding to 280 would be necessary, big overkill, but it does need to be both sanded and thoroughly solvent cleaned before rrecoating, regardless of what material is used, clean is key.
     
  3. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    You need to sand 100% of the surface for a good bond, I normally use 80 grit for gel coat, it will easily hide 80Grit scratches and it yields a good surface to bond to. You can go finer, but it just takes longer and doesn't give any advantage in surface profile.
     

  4. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    Doing some repairs, I sprayed my hull with polyester gelcoat with surfacing agent. Afterwards, I found some minor fiberglass defects that I need to fix. This means I will need to spray gelcoat again.

    What is the best/easiest way to remove the surfacing agent/wax layer so I can spray another layer of gelcoat?

    Is acetone enough or do I have to sand or wet sand?

    I prepped the fiberglass with 280 grit before spraying the gelcoat.....[/QUOTE]
    Gelcoat repair is my main occupation.
    Gelcoat will barely adhere to 280 grit scratch.
    My county's EPA severely restricts my solvent use. I would wet sand with 120(the coarsest my supplier sells), then dry sand with 80and finally wash will acetone.
    If I could, I would wash with lacquer thinner, dry 80, rewash with lacquer thinner with a final wipe of acetone.

    Good luck
     
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