Fiberglass molds....

Discussion in 'Boat Yard Basics' started by flyfisheraa573, Aug 12, 2009.

  1. flyfisheraa573

    flyfisheraa573 Well-Known Member

    So, I'm still tinkering with the ideas of my refurb, and what exactly I want to put in my boat. I have a few ideas, depending on the answers to the following...

    1) how hard is it, and how do you go about creating a fiberglass mold? There was a post on here by a guy that used a cooler to make his mold...why did the fiberglass not stick? Also, I have heard of people using "blue foam", like they do in houses. Could you create a "box" out of this foam and then fiberglass it?

    2) On Jan's Native, he has a "flared" bow...obviously it was like this from the mold. My question is, has anyone else tried to flare a bow that wasn't previously? How would you go about doing it?

    As always, thank you for any and all advice and input?
  2. Brett

    Brett > PRO STAFF <

    Any basic shape can be molded.
    Surface has to be clean, grease free, then polished.
    Multiple layers of mold release wax are applied and buffed.
    Then some will spray a release agent to ensure separation.
    I made a simple mold from a PVC pipe on my build.

    link to procedure here:

  3. Gramps

    Gramps Living &amp; Dying in 3/4 Time

  4. jasonrl23

    jasonrl23 Plays with Glass...

    Most glues will not adhere to plastic without serious abrasion or help from a chemical.  Chances are he waxed the surface before applying the glass/resin.  Which in that case nothing will stick to it.

    You can use the blue insulation foam at hardware stores.  Epoxy is a must as styrene based resins will eat the foam.  You can create pretty much any shape you want with it and then glass over it.  Its also good for "lost foam" molding.  Once your resin is hardened you can eat the foam away with mineral spirits leaving you with a cool hollow glass part.

    Heres a replacement carbon top I made for my trolling motor using the lost foam method: 


    And here is an example of shaping the blue foam and glassing it in.  The bottom part has been glassed and primed the top half is still a work in progress: 



    You could use foam for this depending on your carving skill.  Then either glass around the foam or eat away after the fact with mineral spirits.

    Hope this helps.
  5. Un-shore

    Un-shore Well-Known Member

    If you want to use polyester resin over blue, or any other stytene foam, coat the foam with elmers glue.
  6. kuzus

    kuzus 800-272-7890

    You could also use 2# polyurethane foam and styrene won't melt it. It is a little more expensive than insulation foam, but the cost of epoxy would waste any savings on the foam.

    PVA is a great release to use when doing one-off molds. It's easier than applying a bunch of wax layers.