How to fix slow-curing fiberglass resin: MEKP diluted with?

Discussion in 'Materials' started by kayakingsteve, Aug 27, 2021.

  1. kayakingsteve
    Joined: Aug 2021
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    kayakingsteve Junior Member

    I will definitely do those things next time, except won't it start to gel/catalyze if I wait 10 minutes? The resin started to gel within about 10 minutes and became unusable by 15.
     
  2. kayakingsteve
    Joined: Aug 2021
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    Location: Florida, United States

    kayakingsteve Junior Member

    I will check it out. Bondo is the thing rednecks (like myself) historically use for one-step repairs, so I HOPE it has a wax... that said, now that I understand a little about finishing versus laminating resin, let's say for sake of argument this resin is still tacky because it's a laminating resin...

    What next to get rid of the tackiness?
     
  3. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    Spotty curing can be caused by:

    Thick-thin layer
    Uneven mixing of resin and catalyst
    Uneven mixing of wax
    Old mekp
    Uneven application of suficant
    Acid contamination
     
  4. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    Tacky laminating can be hardened with a layer of finishing.

    Old school way is to use laminating for all preliminary layers. And finishing for the final.

    No prep needed between layers of laminating. Sanding required between layers of finishing
     
  5. kayakingsteve
    Joined: Aug 2021
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    kayakingsteve Junior Member

    Gotcha. I'll see how this thing pans out. Bondo is not listing any ingredients on the can, so apparently it's proprietary. Next time I use a marine finishing resin...

    My texture is awful right now, bad first go... so if I put finishing resin over it, it may all harden enough to sand down?

    (This glass is where my bum will go in a surf-ski, so I don't want to sit on spikey bits)
     
  6. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    Try

    Another layer of what you have
    A bit more mekp
    Smooth a plastic garbage bad onto the wet surface. Try very hard to not have wrinkles
     
  7. BlueBell
    Joined: May 2017
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    BlueBell "Whatever..."

    Not if it's taking over 8 hours to kick once applied.
    5 minutes may be all that is necessary.
    You seem to have a lot of variables going on here.
    Hard to say what's happening.
    Good luck!
     
  8. Kayakmarathon
    Joined: Sep 2014
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    Kayakmarathon Junior Member

    It may be a little late to make this suggestion, but may help others with future repairs. I've seen 2-part epoxy (West Systems) used successfully to fill / repair racing kayak hulls laminated with ester-based resin. Light sanding (>200 grit) prep helps make a good mechanical bond. Pumps consistently meter out the correct amounts of resin and hardener. Use a thickener and cover with wax paper to prevent runs because epoxy is fairly viscous.
     
  9. ondarvr
    Joined: Dec 2005
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    ondarvr Senior Member

    There is no need to let polyesters sit for 5-10 minutes, that's an epoxy thing. Letting it sit will result in a hard and smoking chunk of wasted resin.

    Typical resins have a gel time of around 15-20 minutes in a 100 gram mass, the larger the mass the shorter the gel time.

    Bondo brand resin typically has a very short gel time, so it may be hard quicker.

    If the laminate portion of what you put down is hard but the thin resin layer around it isn't, there's not much to worry about. It will cure far slower and be more affected by ambient temperature and humidity than the thicker areas.
     
  10. kayakingsteve
    Joined: Aug 2021
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    kayakingsteve Junior Member

    What you're saying makes sense and coincides with what I"m seeing. The thinner areas are slower, thicker is faster curing.

    I learned a lot by making a lot of mistakes this time: Was trying to repair cracks in the bucket/seat of an old surf-ski... I learned: 1. I need smaller rollers to flatten the glass out in curved sections 2. I had better luck overlapping small sections of sturdier weave glass for curves and bolloxed up the bigger pieces of mat glass I used... Not a fan of mat for small repairs at this point. 3. Don't try to use your resin once it shows signs of gelling (that's gonna be an extra 30 minutes of power-sanding to get rid of chunks in the weave 4. Work small. 5. make sure to differentiate between laminating and finishing resin.

    I'm sure there will be a lot more mistakes upcoming.

    Is it okay to overlap multiple thin sections of weave glass in one-go?

    What is safe to dilute MEKP with?
     
  11. ondarvr
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    ondarvr Senior Member

    Never dilute MEKP with anything, only someone with little knowledge would tell to do that.

    When using polyester it's not a good idea to use multiple layers of woven or stitched fabrics without CSM between them. And never use cloth with polyester.
     
  12. kayakingsteve
    Joined: Aug 2021
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    kayakingsteve Junior Member

    Thanks for the knowledge, and sorry to sound ignorant, but what is CSM? What kind of resin should I use with cloth?
     
  13. ondarvr
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    ondarvr Senior Member

    CSM=chopped strand mat.

    Cloth works better with epoxy.

    CSM works well for repairing small cracks, larger cracks benefit from woven or stitched fabrics.

    Since cloth comes in very light weights, and CSM needs to be used between each layer, you end up with more CSM and less structural glass in the laminate.

    Also, cloth tends to de-laminate easier than other fabrics when using polyester.
     
  14. kayakingsteve
    Joined: Aug 2021
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    kayakingsteve Junior Member

    Very good to know. Is working in small sections with small patches the way most novices develop their skill? I tried larger pieces of CSM and it did not conform the way I'd hoped, even with time and rolling.
     

  15. ondarvr
    Joined: Dec 2005
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    ondarvr Senior Member

    Yes, start small and work up in size as you become more comfortable.
     
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