Modeling Clay for a Radius?

Discussion in 'Fiberglass and Composite Boat Building' started by Capt. Chris, Nov 17, 2007.

  1. Capt. Chris
    Joined: Feb 2005
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    Capt. Chris Junior Member

    Has anyone used microcrystalline wax to form a radius in a temporary mold? I have to radius an inside corner of a mold, it will be almost a 2" radius. Can I spray PVA right on the wax? I will start with durotec fairing primer as my first coat in the mold and then the glass lay-up behind it, as I will be awlgripping the final product. Any imperfections are very easy to sand out this way. Will the wax be too soft for this big of a radius?

    Thanks in Advance,
  2. wet feet
    Joined: Nov 2004
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    wet feet Senior Member

    Modelling clay will be fine.A good coating of PVA will be useful.I have never encountered microcrystalline wax and can offer no guidance about its suitability.
  3. mongo75
    Joined: Aug 2007
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    mongo75 Senior Member

    I read a great forum on another site where the guy used plain old non-hardening modeling clay for corner radii and re-used a bunch of times.
  4. Capt. Chris
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    Capt. Chris Junior Member

    I just tried some sculpty II polymer clay from the kids craft box, it was hard to mold in the corner but once I did it seemed nice and firm. Sprayed on PVA, did my lay-up and then popped out the part. Looked great once I scraped all the clay off the part. I really thought it might stay in the mold since I have 3 more parts to make. This time I'll try some crayola self-hardening clay...we'll see!

  5. Petros
    Joined: Oct 2007
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    Petros Senior Member

    I once met a guy that made custom fiberglass fairings for light aircraft and he almost exclusively used Sculpty clay. He would put it around an antenna base or landing gear strut where it meets the body, and get it the shape he wanted. Then he would make a fiberglass mold right over the clay, and then make the actual fairing from this mold. he would even reuse the clay since he would not need to heat it. If I recall he put something over the Sculpty to get the fiberglass to come off clean.

    If you warm the Sculpty in your hands it will form easier, and you simply chill it to make it firm up. Of course you could make it more permanent by baking it if your mold will take the heat.

  6. ratrace2
    Joined: Dec 2007
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    ratrace2 Senior Member

    How to model a radius

    Hey Capt: You could use Bondo (automotive stuff). I use it all the time for detail that is hard to capture in a layup. Or, like the others said, you can use modeling clay, Chavante is the best, warm it to room temp and fashion it with a couple of kitchen utensils.......apply a little pvc and off you go.:)
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