Material for molds

Discussion in 'Materials' started by Bigmccc, Jun 25, 2020.

  1. Bigmccc
    Joined: Jan 2017
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    Location: Florida

    Bigmccc Junior Member

    Hi guys - I've looked at the study plans long enough! Time to order plans for Waller 880 and start.

    One first of question is ..what to build the molds out of ? Plywood 1/2 or 3/4 - I am sure will work well (most expensive. , MDF 1/2 or 3/4 nice and straight bit cheaper, OSB- by fare the cheapest - only available in 1/2, cheap chip board?

    I think I need to get a material that will be/stay straight and hold a staple. Money is an OBJECT, but I don't want to save a few hundred and be disappointed in a many thousands project.

    I will be using a CNC machine to cut inside, but constructing outside under a tent in the Florida heat.

    Thanks
     
  2. DCockey
    Joined: Oct 2009
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    Location: Midcoast Maine

    DCockey Senior Member

    I've heard of folks using Advantech sheathing for molds but don't have any personal experience.

    I am assuming you are talking about flat molds which will be set up transversley, and then planks/strips/etc bent around the molds; not a mold for laying up fiberglass or other composites.
     
  3. Bigmccc
    Joined: Jan 2017
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    Location: Florida

    Bigmccc Junior Member

    Yes - the molds for attaching bead and cove ceder strips.
     
  4. Bigmccc
    Joined: Jan 2017
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    Location: Florida

    Bigmccc Junior Member

    Thanks - Just checked out the Advantech sheathing, Looks real good. sturdy, stiff moisture resistant..of course it is the most expensive material I could use. But looks to be the best.
     
  5. Rumars
    Joined: Mar 2013
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    Location: Germany

    Rumars Senior Member

    It does not matter what you do, it's going to cost you either way. Your options:
    1. Make sure nothing moves. This begins with the strongback wich I presume you will make out of some sort of wood. Then there are the molds and lastly the cedar strips themselfs. So you need to coat every piece of wood of the strongback and the molds with 3 layers of epoxy plus paint. Every strip must also get 3 coats after glueing in place, wich means every time you restart glueing strips you need to wash the amine blush from the last installed strip.
    2. Work faster then the wood moves. Give the molds and strongback a coat of cheap oil paint then change the stripping method from wet bead and cove to dry square strip. Strip fast, glue in one shot, fair with a polisher, have the fiberglass on bot sides in a week.
    3. Change the working environment. Make a full tent, isolate all openings with expanding foam from a can, install cheap air conditioning (self contained or window unit) keep the humidity low enough that the wood does not move.

    So pick your poison of choice. Spend the money on epoxy or on air conditioning, but the actual mold material is not really relevant. It's edge just needs to hold the screws or staples you use for stripping.
     
    fallguy and Dejay like this.
  6. Bigmccc
    Joined: Jan 2017
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    Location: Florida

    Bigmccc Junior Member

    Thanks
    1) "make sure nothing moves"
    2)" Work faster than the wood moves"
    3) "Change the work environment"

    Thanks - This helps me understand how I was going to build in a open air environment (my backyard - (tent covered to keep the direct rain off) and the humidity of Florida.
     

  7. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Wood loves to move in humidity.

    Some more than others. If you must build outside; all your materials will gain moisture.

    The strongback could be made from metal i beams or wood i joists. The station jigs need to be made from something that behaves well in moisture. Something like 3/4" plywood would move less as the glues and criss cross grains would hold each other truer. A good 10 ply cabinet birch would be pretty stable.
     
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