Classic harder mistake

Discussion in 'Fiberglass and Composite Boat Building' started by hardguy007, Aug 20, 2016.

  1. hardguy007
    Joined: Jul 2012
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    hardguy007 Junior Member

    Rite, straight to the point...I didn't add enough harder to the gelcoat. Don't ask me why or how but for some dopey reason I only added harder to the gelcoat at approx 0.5%. I mixed 5kg of clear gel with 0.5kg of pigment and split it into 2 containers but I only added 10ml of harder to each.

    So what to do now? Will it go off? Could I risk a first layer of glass?

    Btw it's polyester based and it was on a mould I was laying up.

    Please don't laugh at
  2. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    There are lots of threads asking about improperly mixed hardener - mostly epoxy here, but still, you shouldn't feel worse than you already do.

    Someone will know something - not me, but chin up.

    You're not a real boatbuilder until you can cope with problems. :D
  3. lake pirate rrr
    Joined: Aug 2016
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    Location: nashville

    lake pirate rrr Junior Member

    i would think it would probably not go off at .5

    though you'll know soon enough .. if it fingerprints or dings with a fingernail then it's probably not going to get hard enough ..

    i would put a 'hot coat' over it and see if it'll cure .. if it's not too big a mix .. just boost it to 2% if you have time ..

    i go up and down but always hit 1% just because nothing's worse then perma goop or soft material ..

    i'm new to gelcoat .. but also resin for instance .. i'm no pro just sayin' ... also i got a new digital scale for 5bucks yesterday at northern tool .. i already gooped up my other digi scales .. but i do really like a little chart i made up and dropping it right into disposable drinking cups off the scales ..

    good luck .. hope it hardens up
  4. ondarvr
    Joined: Dec 2005
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    ondarvr Senior Member

    Becoming somewhat hard and curing correctly are two very different things. It can appear cured, but the physical properties may be poor, this includes UV and water resistance, so it's a gamble. It may also wrinkle up when resin is applied.
  5. CDK
    Joined: Aug 2007
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    CDK retired engineer

    That was a decimal error; you should have used 100ml to obtain a 2% mix, now it is 0.2%.
    Only bright sunlight and high temperature can help you.
  6. AusShipwright
    Joined: Aug 2016
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    AusShipwright Junior Member

    I would suggest you need to start again. The gelcoat will pickle once resin has been added.

    As mentioned earlier, common practice for mixing gelcoat/flowcoat is for a minimum of 2% catalyst(depending on conditions). 5kg @ 2% is 100mL. You will also need to reapply release agents used on the mold once you've peeled the uncured gel off.

  7. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    With the exposure to the atmosphere, it is likely the uncured gelcoat absorbed a lot of moisture. The best is to remove it and re-do it.
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