Mdf and plaster fibreglass mold

Discussion in 'Fiberglass and Composite Boat Building' started by arekisir, Dec 2, 2015.

  1. arekisir
    Joined: Jul 2010
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    arekisir Junior Member

    I have made a mold using mdf and faired it up with plaster.
    Sanded with 40 grit it looks ok. Bits of mdf and plaster are exposed.

    Can I roll a coat of tooling gel coat over this direct?
    Or do I need to glass/fair & gelcoat.

    Thanks in advance
    Alex
     
  2. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    Sounds like you need something like an epoxy primer/undercoat, not gel coat of any kind.
     
  3. waikikin
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    waikikin Senior Member

    Or try some Duratec after resin coat
    http://www.ccpcomposites.com.au/duratec-products

    not sure if you can get it anywhere else, years back I used to get it from Adtech

    check out Innovation composites FB page, some nice MDF tooling there at times

    Always seems exxy but so is time.

    Jeff.
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    I was thinking of that, but could not remember the name, I thought duralac, nope thats a jointing compound, duralex, nope !
     
  5. SukiSolo
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    SukiSolo Senior Member

    Personally, I'd coat it with resin at least 2 coats maybe 3, cut wet and spray gloss black 2k. It will show any flaws.... and give you a perfect surface for release wax, or other release agent.

    A quick way to get a semi porous substrate (ie wood) to fill is to use a 2k polyester paint primer. A couple of coats of this sanded and coated with gloss black is almost as good as pure resin coating
     
  6. arekisir
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    arekisir Junior Member

    Thanks Guys.

    I have some leftover laminating epoxy so will add a coat of this direct to the mold to seal.

    After a quick sand hopefully it's good enough to prime and paint if not will add another coat.
     
  7. gonzo
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    gonzo Senior Member

    If you use epoxy, make sure to wash all the amine wax off before using the mold. Amine wax is a cure inhibitor for polyester and vinylester resins.
     

  8. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    I think you should just wax it up and go for it, if 40 grit is "okay". If not, you have plenty more fairing and smoothing to do, at which point you'll have a few different options, but paint is quick, uniform and cheap.
     
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