Need help fiberglass staying tacky

Discussion in 'Fiberglass and Composite Boat Building' started by Reefdog, Nov 27, 2019.

  1. Reefdog
    Joined: Jun 2019
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    Location: Key Largo

    Reefdog Junior Member

    I started working on my transom project and I am running into Fiberglass problems. It seems to be staying wet and tacky. The two 3/4 plywood I glass together are solid as a rock, but I can still feel that it is tacky on the edges. The first layer of cloth can still be pulled upWith a little effort at the 12 hour mark. I have been mixing the polyester resin in 8 ounce batches. The online instructions say to put 10 drops of the Hardner for 8 ounces. The first batch didn’t seem to harden. I bumped the Hardner up to 30+ drops and it still doesn’t seem too harden. I am stirring each batch for over a minute. What do I do? Is everything wasted? Does it just need more time? Pictures below of what I am using
     

    Attached Files:

  2. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    What is the prevailing temperature ?
     
  3. Reefdog
    Joined: Jun 2019
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    Location: Key Largo

    Reefdog Junior Member

    I am in Florida, currently 72, probably high 60s overnight.
     
  4. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    OK, so about low 20's centigrade down to late teens, I would say around 1.5% catalyst should have been about right, but how your drops can be measured as a % is a bit tricky.
     
  5. Reefdog
    Joined: Jun 2019
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    Location: Key Largo

    Reefdog Junior Member

    I have limited fiberglass experience, but in the past I have worked with it under the sun and in higher temperatures. The polyester resin would get super hot and harden right away. I have not noticed my current batch’s getting hot at all, but it did form a tight bond in between the two layers of marine plywood.( still tacky 48 hours later on bits that are exposed). I have bought the resin from west marine in the past but this time bought it from the hardware store. I wonder if this stuff is just crap.
     
  6. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    being sandwiched between two thicknesses of ply acts as an insulator that holds the exothermic heat. Working in direct sun does cause rapid gel times. If it is unwaxed resin, which I assume it may be, it will stay tacky to touch. Give it a little more time, and possibly put it in a heated space.
     
  7. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    Is there a date of manufactur on the container? I have witnessed old mekp drops be ineffective. Try getting some new hardener.
     
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  8. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    Is the resin waxed? Otherwise it will stay tacky.
     
  9. Reefdog
    Joined: Jun 2019
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    Location: Key Largo

    Reefdog Junior Member

    I don’t see a date anywhere. I am afraid it may be old. There is no wax but my main concern is it’s not hardening correctly
     
  10. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    isn't he supposed to avoid oxygen?

    sounds to me like the cure did not happen where O2 was present

    and I only have reading experience on poly
     
  11. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    In your pic I see part of a "lot #" contact the manufacturer. They will know its birth date.

    Try a test batch with known to be new mekp.

    Sticky is ok if un-suffocated.
    Pulling apart at 12 hours is troubling.

    I'm not worried about the ply to ply bond. It will still work in transom.
     
  12. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    I would suspect the MEKP.
    How old is it and the resin?
    Where did it come from?
    Did you have any left over in your batch?
    If so, did it kick?

    As for the transom, give it time to kick off.
    Or
    Sort out your resin/hardener issues,
    pull apart your two pieces of ply and recoat with a hot batch.
    This may be the best scenario.
     
  13. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    Counting drops is a very inaccurate way to catalyze resin.

    For eight ounces of resin you need around 4 cc of catalyst.

    It’s easier to go all metric though, so every 100 CCs of resin requires 1.5 CCs of catalyst, it makes the math simple.

    You can get small measuring containers at the hardware store and pharmacy.

    Either or both of the products could be aged, which can result in a poor cure. And if it was only one layer of cloth (which is a poor choice for any application) it will be very slow to cure.

    Direct sun can help, give it a try. But measuring the products in a more accurate way will yield more reliable results.
     
  14. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    I make it 100 drops of catalyst for every 8 ounces of resin to be 1.5% by volume.
    Even at 1.0% its 66 drops.
    You said you used 10 drops in 8 ounces.
    It would appear you were out by a factor of 10!

    MEKP is ~28 drops per ml
    8 oz of resin is ~237 ml
    237 ml x 1.5% = 3.6 ml catalyst
    3.6 ml x 28 drops per ml = 100 drops of MEKP per 8 ounces of resin

    A trick is to keep stirring until you feel the container start to warm-up, then apply.
     

  15. kapnD
    Joined: Jan 2003
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    Location: hawaii, usa

    kapnD Senior Member

    Also very important to mix the resin before you pour any out. Shake the can!
    Hardware store product may have been on the shelf for a long time, and will separate out.
    As mentioned above, it could be the catalyst as well, and that is also light sensitive.
    It’s good practice to do a small test batch when using unfamiliar material before starting layup.
    Try setting the piece out in the sun for a day or two?
     
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