Gelcoat with aerosil

Discussion in 'Materials' started by mrdebian, Jan 16, 2022.

  1. mrdebian
    Joined: Apr 2021
    Posts: 98
    Likes: 11, Points: 8
    Location: Greece

    mrdebian Junior Member

    Hi all,

    I would like to ask please if there is any ‘danger’ using gelcoat with aerosil.
    For example I want to make gelcoat a little bit thicker to go in difficult parts of a kayak mold and to get more thickness. Same when using it to create the seam of a kayak.

  2. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    I use it for building up thickness on repairs with no problems. However, it is difficult to sand. Leave it a bit low and then fill the last thin layer with gelcoat only.
    mrdebian likes this.
  3. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    I have combined fumed silica with paint for a hard surface and it is a nightmare to sand.

    I think the risks outweigh benefits for you. The surface will become irregular and probably a greater demould risk. I'd be more inclined to want consistent mechanical key for follow on layers versus no key in low spots. But no experience here. I understand Gonzo's point, but he is not pulling on the surfaces of repairs unless he means moulds.
    mrdebian likes this.
  4. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    I mean to fill repairs like in gouges and small holes. I leave the repair low and then finish with straight gelcoat.
    ondarvr and fallguy like this.
  5. Youssef Hamdy
    Joined: Jan 2019
    Posts: 9
    Likes: 4, Points: 3
    Location: Egypt

    Youssef Hamdy Junior Member

    If you want to create a gelcoat putty that you can sand easily as well, I would recommend mixing the gelcoat with Fumed Silica and Microballoons together. ratio is around :
    for 1kg gelcoat, use 20-30gm max fumed silica and 70gm microballoons. you can test and tweak it a bit to reach the viscosity you want.. the microballons are also called microspheres or glass bubbles. check out the 3M Glass Bubbles 1k for example for that. the purpose of the glass bubbles is to make the putty easier to sand. only downside is that it causes it to be slightly weaker against indentations from impact, but in your application it should be fine...

  6. redreuben
    Joined: Jan 2009
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    Location: South Lake Western Australia

    redreuben redreuben

    In this part of the world gelcoat can be ordered as brushing or spraying.
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