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Thread: is a Gel coat ideal or no?

  1. #1
    Senior Member ncrazyballa's Avatar
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    is a Gel coat ideal or no?

    i think ive read before that gel coats on a finish product are not ideal for kit cars, because paint or bondo does not adhere to it?

    is gel coat necessary? i know gelcoat makes fiberglassing easier but is it doable without gel coat?

  2. #2
    Senior Member Don's Avatar
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    You don't have to use gel coat in your molds and you can just pull raw pieces out but it ends up being a bit harder to get the really smooth sanded finish afterward. Gel coat sands and finishes nicer than raw Fibreglass. You also inevitably end up with small air bubbles in Fibreglass when laying the layers down so gel coat helps cover those up when used.

    Certainly can be done but experience is to use it if you can. Paint etc. all stick to it fine. You need to wash off the ,old release and any waxes and then spray on epoxy primer to the Fiberglas or gel coated pieces for a nice seal.

    Good luck
    Don
    308 Ferrari replica
    Prova Countach 5000QV

  3. #3
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    i personally prefer to not use gelcoat, because in more than one occasion, the surface started showing cracks. it probably has to do with me not using it correctly, but i still prefer not using it. also i always like to check layerthickness of the final piece. i do this using a light to shine through the fiberglass and where the colour is lighter, there is less fiberglass. this cant be done or is much harder to do with gelcoat. that being said, i almost only made small parts, wich are less work to sand, fill and finish. on a big piece like bonnet roof or door, i probably would use it just for making it easy on myself.

  4. #4
    I'm no expert when it comes to this however I did parts with and without gel coat. One thing I can tell you is that the parts without gel had tendency of having lots of pin holes int hem and to have them fixed was a major pain in the a*$. With my latest project I decided to use gel on actual body panels for number of reasons, couple of them was the fact that I'm using sandable gel makes it nice and easy to block sand, I did not noticed any holes in surfaces yet. I did brush it on the mold though so that should had eliminated any air bubbles. One problem I did run into was large quarter panels, but most likely it was the fact that I put too much activator into it and couple corners the fibre glass peeled off in 1/2inch radious. Easy fix though. grind it down from surface and reapply gel and sand down flat.
    As to cracking, well I have probably 30 different panels made for my project and they are being put on frame and removed at least 10 times per day when I was making up the frame and are still getting thrown around garage and I do not see any cracks yet (knock on wood) and hopefully it will stay like that. Other added bonus is that you will not see any fibre weave in the sun with gel on the panels

  5. #5
    Senior Member brada's Avatar
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    Gel coats are a prefered method for finishing surfaces in fibreglass because they give the end user the ability for correction.
    A propper layer of finishing Gel should be about .020" - .025" so that you have some mass for blocksanding. Gelcoat is by its nature of application very poros due to the fact that it is sprayed into a mold and air is introduced into the product.
    This makes it ideat for applying on a high build polyester based surfacer/primer which gives excellent fairing mass and paint adheasion!.
    Products like finishing gelcoat typically fail when not applied properly.. appying with a brush is the most common mistakes, .. because it creates highs and lows of product!.. too low (anything .005" - .007") will cause lifting or wrinkling (hammer finish) when resin is applied to it .. anything too thicK ( .030" and above ) lends itself to cracking .. not to mention that this method allows for very poor surface bonding!.
    Tooling gel is yet a differernt matter.
    In some of the production mold we have made we have gone thicker on the gel surface !,.. this is to allow us to wetsand and polish the molds several times over the production run of the molds to ensure a smooth finish on final parts.
    Keep in mind that my molds are 7 layers thick and fully braced and post cured!.. they have absolutly no movement and therefore we dont worry about surface cracking.
    Here are some pics of a mold and finished piece we just did.
    Note the frame for stiffening and the thickness of the end flanges (about 3/8" thick). the entire front clip finisged weighs 22 lbs!.Name:  IMG_1717.jpg
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    Last edited by brada; 02-24-2013 at 09:49 AM.

  6. #6
    Senior Member ncrazyballa's Avatar
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    nice guys, thanks for the help. i just ordered some gel coat, cant wait to create some parts.

  7. #7
    Senior Member brada's Avatar
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    Quote Originally Posted by ncrazyballa View Post
    nice guys, thanks for the help. i just ordered some gel coat, cant wait to create some parts.
    good luck on your new quest buddy.. keep us posted.
    give me a shout if you have any questions on fiberglass..

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