Steps to prep green glass for paint?

Discussion in 'Fiberglass and Composite Boat Building' started by shizlenut, Apr 3, 2011.

  1. shizlenut
    Joined: Aug 2010
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    Location: Seattle

    shizlenut Junior Member

    I am building a cab on my 17 foot whaler and have been going back and forth about gel-coat or paint.

    I am wondering what your ideas are on this, taking into consideration that I have the original gel-coat in the boat and will have fresh green glass on the cab.

    If I were to paint, what steps are taken for preping the glass to paint (besides the obvious fairing and finishing steps), do I need to put a wax in my final lamination to seal it? or do I just spray a primer right on faired and finished glass.

    What steps are taken to topcoat the old gel-coat with paint?

    I'm still a ways from paint, at least 2 or 3 months, but I would like to get my plan together.

    Thanks again.
     
  2. War Whoop
    Joined: Jun 2003
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    War Whoop Senior Member

    Do not put any wax in the last layup,we generally use thickened gelcoat to get off the glass and start sanding in prep for Gelcoat or Painting.
     
  3. shizlenut
    Joined: Aug 2010
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    shizlenut Junior Member

    So I will want to use a layer of gelcoat as a primer?
     
  4. War Whoop
    Joined: Jun 2003
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    War Whoop Senior Member

    Gelcoat is cheap and gets you up on a fair surface,Then you can go anyway you want,If you are going for gelcoat finish, a little gelcoat mixed with the resin on final layup will help if the finish sanding gets close to avoid shadows,With gelcoat 10-12 mills are still semi transparent,on production we go 20-22 Mills for proper coverage.
     
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  5. michael pierzga
    Joined: Dec 2008
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    michael pierzga Senior Member

    War Whoops method is widely used . I have a friend who builds boat components off a mold. The components are typically delivered with an awlgrip white finish. To speed production he gel coats white ...then 545 primes...surface fills..then finish coats. The white is a background primer and protects against sand thru shadows for the white topcoat.
     
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  6. shizlenut
    Joined: Aug 2010
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    Location: Seattle

    shizlenut Junior Member

    Thanks guys.
    I have some experience with spraying paint with an hvlp gun, but non with gelcoat or really fiberglass in general. I want to understand the process of prep for paint because i am more comfortable with my painting skills then gel coating.

    So when I have my cab glassed and green, what are my next steps?
    Fair with putty and sand?
    Spray a layer of gel coat then sand down to then prime and paint with a topside paint?

    I am looking for a general overview of the process to take me from green glass to finished paint, and any tricks or tips along the way.

    Thanks for your time.
     
  7. mastcolin
    Joined: Jun 2005
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    Location: The Netherlands

    mastcolin Senior Member

    Use a primer on the sanded gel. You'll almost definitely have pinholes in the gelcoat and you will see these more in the primer. If you try to just put topcoat on the sanded gel you'll probably have no technical problems but if it is pinholey you"ll have to fill and sand. Primer is cheaper than topcoat.

    This goes for the new gel as well as old. In fact the old gel will probably be even more pinholey than the new.

    Leave the new gelcoat for as long as you can before priming. You can get problems if you do it too quick (interaction with styrene and peroxides with epoxy system in primer).

    We normally use p180 3m gold to sand the gel before priming. This is rough/quick enough for key but not too rough for scratch marks to shine through.

    75microns primer (dry) is enough. (1 spray session, 2-3 brush/roller). This will leave you 50microns after sanding.
     
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  8. War Whoop
    Joined: Jun 2003
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    Location: Sunny Ft Lauderdale Fla

    War Whoop Senior Member

    Spray? You can Brush the first coat of inhibited gelcoat on, then hit it with a 8" DA.
     
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