Gelcoat tinting - Here I go again, hopefully i'll get it right this time.

Discussion in 'Fiberglass and Composite Boat Building' started by Dan H, Sep 9, 2009.

  1. Dan H
    Joined: Jun 2009
    Posts: 23
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    Location: United States

    Dan H Junior Member

    Ok, so I screwed up the first spraying of gelcoat on the boat. Boat was white, I sprayed dark blue gelcoat without enough pigment and you could see the original gelcoat through the dark blue. I sanded it all off. Now I'm getting ready to put new gelcoat on. I know paint is better and all that but I like gelcoat for polishing out flaws and the repair aspects of it. So here I go again.

    I'm told 1 gallon per 75 sq. ft. = 15 mils build. The boat is a 25' Catalina sailboat. 75 sq ft per topsides. So both sides 2 gallons, quart for the transom. I'm using Duratec to thin the gelcoat and provide for the cure without using wax.

    I've read articles that say to mix the Duratec 1/3 to 2/3 gelcoat for the first coat and 2/3 Duratec to 1/3 gelcoat for the final coat. OK that would give me a very shiny top coat. But what about repairs down the road? Would using Duratec 50/50 through all the coats be better in the long run or does it not really matter? Spraying the 2/3 Duratec and 1/3 gelcoat will give me a smoother shinier finish coat, maybe?

    I printed a series of colored stripes on a white piece of paper. I'm thinking I can cure a 10 mils sample of gelcoat between two pieces of glass and see if I can see the colored stripes through the cured gelcoat. That might be enough of a test. If I can shine a light through it and cannot see the stripes, I figure that ought to work.
    Any thoughts besides,..."Your crazy!" cuz I already know that.
    Thanks in advance,
    Dan
     
  2. Canracer
    Joined: Aug 2009
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    Location: Florida

    Canracer Senior Member

    Wow, sounds like a project.

    I was reading your post, all the time thinking "I would probably just paint it."

    If you get a chance, throw up some pictures.

    Soon, I will be in the same State as my boat, and I will be looking to do a similar project.
     
  3. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    As said before, Duratec is not a miracle cure all and may create other issues.

    Most won't use it on hulls because the water and UV resistance will be reduced.

    If I was going to use it, I would never go over 20%, and try to not use that much.
     
  4. Dan H
    Joined: Jun 2009
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    Location: United States

    Dan H Junior Member

    What would you use instead of Duratec? How do you thin the gelcoat to spray it on the outside of a hull for repair?
     
  5. jim lee
    Joined: Feb 2007
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    Location: Anacortes, WA

    jim lee Senior Member

    I've seen people use the Duratec high gloss up to 50% and thinning with MEK. They say MEK works better as a thinner than styrene. Now that I read ondarvr's post I worry about the amount of Duratec they are using. Oh well, too late now..]

    -jim lee
     

  6. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    There are patchaid products designed for use with gel coat, even these can create a few problems though. You can get these at most F/G supply stores.

    The products made for reducing gel coat typically use a good base resin that's also used in gel coat, this way the physial properties aren't affected as much. They may use some solvents also, but try to keep them to a minimum.

    Always add as little patchaid or thinners as possible, only enough to make it easier to spray, don't try to turn it into auto paint.

    If any of the things people add to gel coat actually helped, or improved it, they would be added to start with.
     
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