How to make a hollow fiberglass object.

Discussion in 'Fiberglass and Composite Boat Building' started by CDK, Jun 17, 2010.

  1. CDK
    Joined: Aug 2007
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    CDK retired engineer

    Make a styrofoam core and paint it with pva.
    Apply the first glass layers on a warm day so the resin cures fast.
    The polyester fumes will ignore the pva barrier and dissolve (nearly) all styrofoam and maybe react with it too, because the sliver left is hard as stone.

    This was an object I cut open because it was too long: I had no idea this had happened.

    Applications? Making fiberglass tanks perhaps. The remaining bits of polystyrene cling to the inner walls as snowflakes and can be easily washed away with acetone.
     

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  2. daiquiri
    Joined: May 2004
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    I love these great casual discoveries! :D

    Thanks for sharing it with us.
     
  3. apex1

    apex1 Guest

    "TRIAL and ERROR"​


    ..the unwritten book, and still the best tutorial.:D

    Thanks Cornelis for sharing.
     
  4. SamSam
    Joined: Feb 2005
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    SamSam Senior Member

    30+ years ago I made a banjo case using polyester and Styrofoam. I wrapped the foam in duct tape and pva thinking that would work but it didn't. The foam melted as the glass cured so the case ended up usable but deformed. All that was left of the foam was a ball the size of a golfball.

    What you're proposing is basically the lost wax process in a different medium, maybe it's already obscurely used in areas of manufacture. Maybe the lost wax process would work for fiberglass.

    As you suggest, it seems it could be useful making seamless tanks and things. If epoxy was used, there would be no danger of the mold deforming and you could still dissolve the foam with styrene fumes and acetone.
     
  5. CDK
    Joined: Aug 2007
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    CDK retired engineer

    SamSam, my object turned out well, probably because the resin cured very fast when I made it and it wasn't that large.

    I was surprised to find the core gone and briefly thought about possible use for this procedure. But you are 100% correct: using epoxy and washing out the core with acetone is a less risky operation.
     
  6. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    Yes, the core gone in my banjo mold got me to wondering about my job building boats. A small operation with no protections.
     
  7. Stumble
    Joined: Oct 2008
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    Stumble Senior Member

    There is actually a very nice article on West Systems web page about this process.

    Their recommendations are to use any type of cheap foam that is disolvable in actetone / solvent of your choice, shape the foam, add the glass/epoxy, then throught a weep hole add the solvent. I have used it a few times for one off parts, and it really does work well.
     
  8. AndrewK
    Joined: Mar 2007
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    AndrewK Senior Member

    This is a common practice for making custom FRP exhaust components like water locks.
     
  9. LarryMcI
    Joined: Mar 2010
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    Location: Florida

    LarryMcI Junior Member


  10. tunnels

    tunnels Previous Member

    Now thats what i call using you noodle !! :idea: very clever !!
     
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