thickening resin with wood flour

Discussion in 'Boat Yard Basics' started by jcoody, Apr 29, 2011.

  1. jcoody

    jcoody I Love microskiff.com!

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    When I thicken my resin with wood flour for doing filets, does thickened resin take longer to harden then just normal resin?
     
  2. WhiteDog70810

    WhiteDog70810 Mostly Harmless

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    Not in my experience.  You have to handle it more up front while you mix the fillers in, so most guys actually experience shorter pot life.  Once you lay the fillets, you have more epoxy in one place, so the fillet cooks off quicker than neat epoxy or saturated cloth.  If you leave any epoxy sitting still in the pot, with or without filler, it will cook off real quick.

    I suppose you could make the argument that the filler acts like an insulator and slows down curing, but this has minimal real world effect because epoxy generates an overwhelming amount of heat once hardener is added.  You just have to keep stirring and work fast.

    Nate
     

  3. firecat1981

    firecat1981 BBA Counselor

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    It seems to cure faster for me. When wetting out cloth on a normal day I'm at 5-6 hours, when doing fillets it cures about an hour faster.
     
  4. jcoody

    jcoody I Love microskiff.com!

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    Ok. Thanks guys that answered my question!
     
  5. Brett

    Brett > PRO STAFF <

    2 part epoxy, when mixed together, produces an exothermic reaction,
    that is, it produces heat as a byproduct of the chemical process taking place.
    The higher the temperature of the mix, the faster the reaction takes place.
    In small amounts, or thin layers, the heat is radiated away or transferred
    to the surrounding air or nearby surfaces. But in quantities of sufficient thickness or volume,
    the surface area of the mix, isn't great enough to allow the heat to transfer out.
    As a result the heat stays in the mix, increasing the rate of reaction,
    which increases the temperature of the mix. It can actually become a fire hazard.
    To make epoxy cure slower, cool the components before mixing
    or apply the mixed epoxy to cool surfaces, or under low temperature conditions.
    Like early morning before the sun warms things up, and work in the shade.
     
  6. jms

    jms don't let common sense get in your way

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    cold epoxy is tough to work with...it's best to use large containers when mixing - using a small cup,it confines the mix-heats up quicker...

    never throw mixed epoxy into trahs cans - it will start a fire - i keep a 5g bucket half full of water - i throw my containers in that...

    if you're working in hot climates - and you're using west system - use the tropical kicker,or,if temps allow,use the "slow" kicker...
     
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