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Thread: Concrete VMC

  1. #73
    Activation process peteeng's Avatar
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    Default Re: Concrete VMC

    You would be very disappointed with polyester. It shrinks 8% by volume. Over time your parts would warp and move ask any boat builder about their boat panels shrinking.... Epoxy or PMMA is the best for this application. Are you using PVA for the release? Not PVA glue which should be properly called PVAc Peter



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    Default Re: Concrete VMC

    Today is started fabricating the mold, steel strips are now aligned and bolted to the bottom plate of the mold. Tomorrow i want to place the rest of the inserts.
    Yesterday the silimix arrived next week the epoxy will arrive so next weekend i can hopefully start casting.

    stef







  3. #75
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    Default Re: Concrete VMC

    Sihts about to get real!



  4. #76
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    Default Re: Concrete VMC

    1) Make sure table is stout enough for the weight.
    2) Brace the long sides so they don't bow outward from the pressure
    3) Clay or caulking to radius the joints to help keep epoxy contained within and ease of release.



  5. #77
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    Angry Re: Concrete VMC

    Quote Originally Posted by peteeng View Post
    You would be very disappointed with polyester. It shrinks 8% by volume. Over time your parts would warp and move ask any boat builder about their boat panels shrinking.... Epoxy or PMMA is the best for this application. Are you using PVA for the release? Not PVA glue which should be properly called PVAc Peter
    Peter, you are completely full of it. You seem to be purposely posting misleading information to suit your negative agenda. Someone reading your post would likely assume that polyester composites would shrink by 8% which is obviously complete BS. Maybe resin by itself in a cup, but laminates are half fibre. For polyester laminates, which are for the most part made in a mold or on a surface table, the mold holds the part during cure and laminate shrinkage is toward the mold surface (i.e minor shrinkage of the laminate thickness) and not on the overall dimensions of the part. Polyester parts can be very dimensionally accurate (if allowed to reach significant cure before demolding). Conversely, polyester laminates not constrained in a mold will exhibit shrinkage to some degree. But considering polyester as a concrete binder is very different due to fibre in a laminate being like pushing on the ends of a piece of string (i.e. the fibre is inherently unable to resist shrinkage) whereas aggregate (rock) is uncompressable and therefore very able to resist shrinkage. You need to open you mind a bit, and stop posting your bs..

    PS you say "ask a boat builder".... well that would be me. Marine - transport - industrial. We use polyester / vinylester by the ton(s) every day.

    PPS Low / zero shinkage modified polyester products are available.

    Last edited by jono5axe; 04-19-2019 at 11:52 PM.
    Jonathon Clarke
    www.solpont.com


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