Mist before epoxy cured

Discussion in 'Fiberglass and Composite Boat Building' started by tuantom, May 1, 2009.

  1. tuantom
    Joined: Jan 2005
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    Location: Chicago

    tuantom Senior Member

    I was doing some fairing work on my fiberglass hull with epoxy mixed with a fairing compound (I think it's a mix of microballoons, q-cells and cabosil) when, wouldn't you know it, a mist moved in. I checked the weather for rain; but not mist. Now it's been two fairly cool (highs in mid 50's F and lows in low 40's) and damp days since I did this and I'm a bit worried about the state of things. I can still dig a fingernail into the fairing compound and it has an oddly light color to it. I compared this to some of the muck left on the spreader which made it out of the rain and into a bucket in the garage (no heat); and it's definitely softer - but the compound on the spreader was still a bit soft too.
    I know I mixed the proper ratios - 3 pumps to 1 pump; so that's not the problem.
    Do I just have to be more patient? Will this ever harden after getting wet before it cured?
     
  2. mydauphin
    Joined: Apr 2007
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    Location: Florida

    mydauphin Senior Member

    Be a little more patient but at the end if it does not harden properly you will have to scrap it, wire brush it and ultimately sand it off. A power wire brush with a little soap or oil seems the best to remove gummy epoxy.
     
  3. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    What type of pumps are you using? Most pumps are arranged (pre-set ratio) so you give each the same number of strokes.

    If the mixture is correct, you'll likely have some cloudiness, but it will cure once the temperature comes up and stays there long enough. If the mixture isn't correct, then you can't save it and the whole of the bad fairing mix will have to be removed.
     
  4. AndrewK
    Joined: Mar 2007
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    Location: Australia

    AndrewK Senior Member

    Heat the bit on your scraper for 8hrs at 140+'F if it goes hard then you know the mix was OK and you can do the same for the job.
     
  5. Guest625101138

    Guest625101138 Previous Member

    It needs to be dried out by good air flow and some even heating over the work.

    I have done this with some sheeting and a fan heater. If you can get it nice and dry it should lose any milky appearance on the surface and set hard. It will take a few days to cure properly unless you hold the heat. A good dose of sun will help.

    The amine blush seems worse when curing is slowed by low temperature and high humidity but I do not know the chemistry. This means it could end up being sticky but this can be washed off before recoating.

    Rick W
     
  6. tuantom
    Joined: Jan 2005
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    Location: Chicago

    tuantom Senior Member

    Thanks for the replies. I put the spreader and a small chunk I broke off from the boat over low heat overnight. Both of them hardened up nicely - good news, cause I was really starting to question my ability to count to three ( I have equal volume pumps). It's supposed to be in the mid sixties and dry here for the next couple of days; hopefully this will do the trick.

    If not; and my patience wears out, I have some tarps and propane heaters I've used for similar jobs in the past.

    I was hoping to at least get a coat of primer on this weekend - probably not not going to happen now.
     
  7. AroMarine
    Joined: Jul 2005
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    Location: Atlantic City NJ

    AroMarine Junior Member

    Many epoxies almost stop curing @ 40 so your 40 to 50 up there in Chicago is right on the limit of curing temp. I am in New Jersey and have similar temps to you. The other thing to watch for is when the resin is cold the pumps on any resin system I have used don't like to work well. When working in cold temps I also warm up the resin while I am mixing it to insure better mix and reduce the (thixtropicness ?) to a normal state.
     
  8. AroMarine
    Joined: Jul 2005
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    Location: Atlantic City NJ

    AroMarine Junior Member

    Tuantom, you should also try to heat up your patch to help insure a full cure. Even though it feels hard it is probably still curing and will continue to put out amines. Good luck
     
  9. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    Funny, in Miami Florida... I have to put my epoxy in fridge to get some working time.... I wonder does epoxy loose its strength if allowed to get really cold like 40F then let warn up again before mixing?
     
  10. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    No, if epoxy is re-warmed it's fine, though it can lose a substantial amount of strength if forced to cure in very cold temperatures.
     
  11. apex1

    apex1 Guest

    And for exactly that reason I would recommend to hurry and heat up the whole junk to get properly cured!!!!!!!!!!!!!!!!!

    Regards
    Richard
     
  12. tuantom
    Joined: Jan 2005
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    Location: Chicago

    tuantom Senior Member

    I got impatient last night when the epoxy still gummed up my sandpaper; and broke out the tarps and my propane heater. I left the heat on for several hours overnight and it seems to have done the trick.

    I didn't have time to thoroughly sand it; but the little bit that I did sand seemed fully cured.

    It went took six days and additional heat to get it to cure - and four of those days reached the mid sixties (but in the 40's at night).
     

  13. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    For what it's worth, it would have cured in spite of the temperatures, but it might not have been as strong as you'd like it. I know guys that build boats in Maine and other God forsaken cold *** places. They'll epoxy the crap out of things, wait until a good day in the spring (read June) then roll it out side for a good "post cure" in the sun. Damn, that's some determined boatbuilding.
     
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