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Thread: New to gel coat methods. alittle help please.

  1. #1
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    New to gel coat methods. alittle help please.

    can gel coat be applied by brush? I have a 26g compressor with a spray gun that came with it and a set of hvlp sprayers, can I spray gel coat with them? or do I need to buy a special gun? thank you.

    26g should be fine for panel molds, I am sure. I hope.
    -Rob

  2. #2
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    Re: New to gel coat methods. alittle help please.

    Epic due to the viscosity of the gel coat I'm pretty sure you have to have a special gun for the app. I know there are several online fiberglass companies and those that sell gel coat most of the time offer a gun for it as well. I have no idea whether you can brush it on or not, but if I were doing it, spray is the way I would go. If you need a link for the gun let me know. I'll have to look it up but I can find it.

    Mike

  3. #3

    Re: New to gel coat methods. alittle help please.

    Gelcoat guns are usually different than regular spray guns. Here's a pic:

    http://www.esska.de/esska_eng_s/air_powered_gelcoat_gun,pd2860!10,,5-G-200.html


    There are also cheaper guns. (I'm not sure about quality as I've never sprayed Gelcoat but I'm sure others will chime in). You can also try to contact WraithInovations on the forum. He really seems to know his stuff in that area.

    There are others on the forum as well but "wraith" just came to mind because he recently answered some of my fiberglass questions.

    Cheaper Gun:
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    Re: New to gel coat methods. alittle help please.

    thank you but the first link you provided brings up another question;

    can you just buy a seperate nozzle that can be adapted to any spray gun? http://www.esska.de/esska_eng_s/pain...y_nozzles.html
    -Rob

  5. #5

    Re: New to gel coat methods. alittle help please.

    in general, it's recommended that you brush on gel coat because spraying can cause bubbles and air pockets. gel coat is the first line of defense against the elements on a panel, and it's also the thing you see (and fix before paint) so bubbles will either cause cracks in the future, or appear as holes you need to fill manually making body prep 5x more time consuming. professional FG shops rarely need to do anything to new panels before the paint process.
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  6. #6
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    Re: New to gel coat methods. alittle help please.

    thank you autoMX
    -Rob

  7. #7

    Re: New to gel coat methods. alittle help please.

    For making parts (not molds) ,there are usually 2 types of gel coat, for brushing or spray and with air-dry (wax additive) or not. Air dry is usually used if you spray gel coat as a final coat rather than for lamination. The air-dry additive will make the gel coated surface non-tacky once fully cured.

    As for brush or spray, the viscosity is different.
    At worse you can brush both.
    Beware, If you don't apply an even coat, especially in corners, too much gel coat will pull away from your mold while curing (especially if you use the more liquid one, formulated for spray gun). not enough may cause some blisters (the resin may disolve it).

    for larger parts I would also recommend to use a gel coat gun. The one with the disposable paper cup. It's easy to clean and operate. It's also cheap to buy. The tip on this type of gun may vary but it's about 1/16-1/8". Unlike standard spry guns, it doesn't have any needle.
    It's best for big surfaces but you'll loose too much gel coat if you use it for a small part. I wouldn't recommend investing and using a gun on a single small mold. On the other hand, keep in mind that the brush may leave some see through "marks" if it's not fully coated. It's sometime hard to apply an even coat if your mold is over waxed.

    Another thing to consider is to laminate your piece before the gelcoat is fully cured. It should be tacky at the touch without leaving some on your fingers. The pulling of the gelcoat may occur if has too much time to dry. This will rarely happen when using a spray gun unless it's over catalized.

    With all respect to automx (bubbles and air pockets),
    I make fiberglass parts every day and these are either caused by not properly rolled-out Fiberglass mat/ fabric or the pulling of gel coat and blisters (thin layer of under catalized gel coat).
    good luck

  8. #8
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    Re: New to gel coat methods. alittle help please.

    this is very useful. thank you very much for posting.
    -Rob

  9. #9

    Re: New to gel coat methods. alittle help please.

    i was talking about pinhole/fisheyes caused by air bubbles in the gelcoat (maybe 2mm wide). a proper gun and procedure will bypass that problem, of course. bad layup and air pockets between the gelcoat and glass/resin will make much bigger problems.
    Professional 3D, web, graphic, architectural, interior, and CAM design at affoardable prices.<br />Any questions: voicemail/fax (323)281-0583<br />sales @ rt-network.com

  10. #10
    Senior Member Kstix's Avatar
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    Re: New to gel coat methods. alittle help please.

    I used an old primer gun

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