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Thread: gel coat or no gel coat -or willing volunteer needed

  1. #1
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    gel coat or no gel coat -or willing volunteer needed

    I'm going to pull some reversals (parts) out of an ultracal 60 molds (moulds), -car bodykit- do i really need to use a gel coat layer if i'm going to give the parts a few coats of epoxy primer filler before final paint. I really hate working with fiberglass (or fibreglass) , hence the ultracal moulds, so if there is anybody in the metro detroit area who is willing to make these parts for me , i'm all ears

    thanks

  2. #2

    Re: gel coat or no gel coat -or willing volunteer needed

    Ultracal is a plaster based product, right?
    If so, unless your mould is well made and thick enough, it won't last long.

    From my experience with a similar product (FGR95) you should seal your plaster mold with at least two coats of shellac. This will keep any moisture from interfering with the gel coat. Also make sure the mold if fully cure first (no more moisture). After, I apply many coats of wax and even PVA as an extra precaution. I occasionally make "one time" plaster molds and noticed that the gel coat will wrinkle or be absorbed by the paster if too humid or not properly sealed. You'll notice that problem (absorption) if the gel coat loses his gloss in the mould. If so, you'll won't be able to de-mould the piece without damaging the piece and/or the mold. BTW, it's always a good thing to reinforce the plaster mold with fiberglass cloth.

    As for gel coat or no gel coat. It's easier to laminate fiberglass cloth if you have a gel-coated base. It will fill all small creases or sharp cuts in your design and also small imperfections and pinholes.
    It easier to sand off these imperfections from your part after than fixing them with filler or many lawers of primer.

    As for the part itself, a non gel-coated piece will tend to show the weave or fiber strands under hot exposure (hot summer days).

    just my humble opinion.. good luck


  3. #3
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    Re: gel coat or no gel coat -or willing volunteer needed

    you are correct ultracal 60 is a tooling plaster,used extensively in patternmaking when you only want one or 2 accurate parts , without the cost of a polyester or epoxy mold. its easy to work with , and most importantly does not smell!!!.
    thanks for the feed back of the no gel coat thing.

  4. #4
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    Re: gel coat or no gel coat -or willing volunteer needed


    I have seen some people use epoxy primer as a cheap alternative to gel coat with decent results as well. You just use spray the primer on in place of the gel coat, with the same 2 - 3 mil thickness.

  5. #5
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    Re: gel coat or no gel coat -or willing volunteer needed

    bpickell thats an intresting idea. If that really works, you already have your part primed!

    My question is, would the primer dry to fast on large parts to prevent the veil or cloth from sticking? I would think one would for sure want veil first before cloth if all you had was primer as the gel coat.

    Mike

  6. #6
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    Re: gel coat or no gel coat -or willing volunteer needed


    I'm trying to find the thread now where I originally saw that posted. It's been a really long time. I just found another thread discussing the same procedure, but they are saying polyester based primer (Duratek) and not epoxy primer.

  7. #7
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    Re: gel coat or no gel coat -or willing volunteer needed

    Quote Originally Posted by detroitbrit
    you are correct ultracal 60 is a tooling plaster,used extensively in patternmaking when you only want one or 2 accurate parts , without the cost of a polyester or epoxy mold. its easy to work with , and most importantly does not smell!!!.
    thanks for the feed back of the no gel coat thing.
    detroitbrit cold this be used for a full set of molds for a car body or would the sizes of the parts not be a good fit for the plaster?

    Mike

  8. #8
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    Re: gel coat or no gel coat -or willing volunteer needed

    works pretty much on anything, it works best for splash molds ,its a cost effective method for producing molds
    cheaper that polyester

  9. #9
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    Re: gel coat or no gel coat -or willing volunteer needed

    You guys mentioned using an epoxy primer as a replacement for gelcoat. That will work but there are several products designed for that purpose and they are cheap. The most common is DuraTec polyester primer. They have one that is design to be sprayed in the mold and laminated on top of, I use it a lot. I think it is only about $75/gal and includes acitivator. It can be sprayed with normal automotive type guns with a large nozzle, I use a 2.2mm.

    I hope this is helpful and I am not sticking my nose where it is not wanted.

    Bart

  10. #10
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    Re: gel coat or no gel coat -or willing volunteer needed

    Bart I don't think your nose is a problem! ;D I personally am trying to glean info to help me with a non car related project. I have a product I want to try in carbon fiber, and the process for a quick mold that detroitbrit mentioned, caught my attention.

    Mike

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