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Help With Gelcoat In Fish Mold

Discussion in 'Molding and Casting' started by 1stturkey, Jun 9, 2021.

  1. 1stturkey

    1stturkey Member

    I'm trying to follow Gary Bruch's "Molding & Casting Fish" article in Breakthrough issue 85 but am not certain I'm using the gelcoat right. The stuff I bought (Marine Evercoat) is pretty thin. I added about 12 drops of catalyst for the few ozs of gelcoat and poured it into the mold but it never completely hardened, even overnight. Also, I'm not sure if this is supposed be set up before proceeding with adding the fiberglass chop and resin to strengthen the body. The article mentions gelcoat can be made thickening resin with cabosil. This sounds cheaper than gelcoat itself.

    Did I just not add enough catalyst to the gelcoat or is the Marine Evercoat the wrong stuff. Was almost $70 a qt thru O'Reilly's.

    Any help is appreciated.
  2. Frank E. Kotula

    Frank E. Kotula master, judge, instructor

    There could be a lot of factors in this
    Not enough catalyst
    Age of gel coat
    You might get it to set up by mixing a hot batch and going over the semi set one but it may not work depending on what’s going on between the fish and the gel coat.
    I always seal them first with lacquer before I do a gel coat to seal in moisture.
    You might have to scratch it off and start over if the fish is ok or try your luck on another one. Sometimes things get omitted when we write things down for publication

  3. 3bears

    3bears Well-Known Member

    I'm no expert here but you are trying to make a cast from an already poured mold, right? Here's my experience with gel coat and it's somewhat limited in casting. If you do not get it mixed up properly it can take forever to set, it almost seems like gel coat without hardener with set quicker. Also not enough hardener, which this sounds more like your issue, will cause this. I'n one of my previous career, auto body, when using chop it got embedded in a wet coat of gel and then smoothed over with more gel. When it comes to strengthening a cast I would think you want the outer layer, detail layer to set up and then spread another tack layer of gel to that and then embed the chop into that.
  4. 1stturkey

    1stturkey Member

    Thanks for the help guys! Yes, I'm pouring into a bondo/resin mold sealed with PVA. The gelcoat was just purchased so I probably just didn't add enough catalyst/hardener.

    I removed the cast bullhead that didn't completely harden and will reseal the mold and try again with a "hotter" gelcoat mixture.

    Appreciate the feedback!
    Frank E. Kotula likes this.
  5. Mudbat

    Mudbat Well-Known Member

    I don’t use gel coat just bondo/resin. Gel coat costs to damn much these days!
    1stturkey, Terry Bennett and 3bears like this.
  6. 1stturkey

    1stturkey Member

    Thanks, Mudbat! It really is crazy expensive. The article even states you can "make" gelcoat with resin and cabosil. I'm gonna try that too.
  7. crablover

    crablover Well-Known Member

    Turkey, resin and cab o sil mixed is not gel coat! True gel coat contains titanium dioxide. The heat people talk about is not going to happen when your gel coat or resin is spread so thin. Only in bulk will heat be created. Your gel coat needs to be wax free and the MEKP that comes with resins is usually bad because it is photo chemically reactive and sold in clear tubes. Get some good MEKP like High Point 90 and keep it in the refrigerator. If you still have the fish coated, take it out and put it in the sun or under UV light. There is so much misleading information posted about fiberglass resins, like adding both hardener's to a bondo resin mix, and that resin and bondo is gel coat. NOT! Get some good quality MEKP, coat your part and set it in the sun. If you do not see a color change when adding your hardener, you have not added enough
    1stturkey likes this.
  8. 1stturkey

    1stturkey Member

    Thanks, crablover! Appreciate the excellent information!!
  9. 13 point

    13 point Well-Known Member

    Crab lover knows what he is talking about he does a lot of glass work. I would follow what he tells you for a superb product.
    1stturkey likes this.