Gelcoat over Epoxy Failure

Discussion in 'Fiberglass and Composite Boat Building' started by Klink Sanford, Sep 13, 2022.

  1. Klink Sanford
    Joined: Dec 2021
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    Location: Sanford FL

    Klink Sanford Junior Member

    In my Boat Design thread Gelcoat as non-skid on Deck https://www.boatdesign.net/threads/gelcoat-as-non-skid-on-deck.66402/page-3 I detailed my experience trying to apply gelcoat over the deck of my 1968 Boston Whaler which I had glassed over with 2408 and RAKA epoxy.

    Since then, I continued trying to get it to work following the directions of a local boat builder and FGCI by using Vinylester resin as a tie coat between the epoxy deck and the gelcoat finish. I did like three trials on the deck itself and it did not work. The VE will not harden completely over the RAKA epoxy (which is 4 years since it was applied, and has been washed, dry and wet sanded innumerable times). I did the final test yesterday and the VE did harden over the area that had been previously:
    1) gelcoated over epoxy and did fully not harden and had to be removed. What remained behind of the gelcoat that did harden little spots here and there.
    2) Then the same spot was coated with a tie coat of polyester resin and later gelcoated, and again did not fully harden and was again removed with new spots remaining that did not come off.
    3) Then the same was done with a tie coat of Vinylester and then gelcoated and again did not fully harden and was again removed with new spots remaining that did not come off.
    4) and finally yesterday I again vinylestered and checking it 24 hours later it finally hardened in the area that had been coated all the times (1,2,3) above and sanded, but the vinylester that was at the very edge was gummy and could be scraped off with my nail, and drops of vinylester that fell outside of the entire area were still liquid.

    The conclusion is that if one wants to use gelcoat over epoxy, use a complete system with one supplier of the epoxy and the gelcoat (and poly and VE) that they say works, do not mix brands. FGCI says you can cover epoxy with gelcoat if you use Vinylester as a tie coat, well, that advise is wrong in my case with RAKA epoxy. It would be more accurate for FGCI to say that their epoxy/Vinylester/gelcoat "system" works with their products, but they can't guarantee the same result if other brands are used.

    My son told me to try putting FGCI epoxy over the RAKA then putting FGCI Vinylester then gelcoat. I think I've had enough and I am just going to paint the deck.
     
  2. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    I used Kiwigrip. Looks great. Requires 40-80 grit sanding prep.

    24EE95C3-0526-48E2-A212-ED6614C38FFB.jpeg

    ps...I think you did something wrong..I don't think the issue is related to epoxy...despite the fact you got cure over old gc; the air chemistry/wax has to be done right...

    @ondarvr may shed some light if he has time
     
  3. tpenfield
    Joined: Dec 2016
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    Location: Cape Cod, MA

    tpenfield Senior Member

    Poly & VE based resins (gelcoat) over epoxy is difficult because of the waxy blush that epoxy leaves behind.

    Any chance you can get/use an epoxy-based gelcoat?
     
  4. Klink Sanford
    Joined: Dec 2021
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    Location: Sanford FL

    Klink Sanford Junior Member

    ps...I think you did something wrong..I don't think the issue is related to epoxy...despite the fact you got cure over old gc; the air chemistry/wax has to be done right...
    [/QUOTE]

    Between the linked previous thread and this one, I have over 20 tests accounting for every variable, that's a lot of tests, using poly and VE resin, waxed gelcoat, laminating gelcoat, PVA, and it is over 4 year old epoxy that has been washed of amine and wet sanded innumerable times.
     
  5. Klink Sanford
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    Klink Sanford Junior Member

    The epoxy is 4 years old and has been washed and wet sanded innumerable times, amine left behind is an impossibility.
    I never heard of epoxy based gelcoat, to my knowledge all epoxy breaks down with UV and has to be coated with paint or gelcoat.
     
  6. fallguy
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    fallguy Senior Member

  7. aaronhl
    Joined: Aug 2012
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    Location: Central Connecticut

    aaronhl Senior Member

    Maybe a stupid question but did you spray PVA over the gelcoat or add wax to the gelcoat so it could harden?

    I've sprayed a bunch of Duratec over Raka 2:1 epoxy without any issues, I'm sure there were a few areas I've put gelcoat over the bare Raka epoxy without issues

    The only epoxy I had problems with was the 50/50 paste epoxies like traditionally for metal and another 50/50 from Fastco I think, gelcoat could not harden over those, Raka never an issue

    If you are still having issue try sanding everything down with 80 grit, spray Duratec over it and then the gelcoat (with curing barrier)
     
  8. Klink Sanford
    Joined: Dec 2021
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    Klink Sanford Junior Member

    I used RAKA 127/606 slow cure epoxy, and no other. For the gelcoat, I used Fiberglass Supply Depot (FSD) laminating gelcoat, no wax. On the first gelcoat layer over the epoxy, I used no wax. On the 2nd and final layer I added wax. On smaller areas and tests I brushed on PVA after the final gelcoat coat of no wax. The FSD and FGCI gelcoats did not harden at all over the RAKA 127/606 slow cure epoxy although the epoxy was 4 years old and washed and wet sanded innumerable times during those years.
     
    Last edited: Sep 15, 2022
  9. fallguy
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    fallguy Senior Member

    Based on Jamestown's article; you needed a barrier coat, not a tie coat.
     
  10. aaronhl
    Joined: Aug 2012
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    Location: Central Connecticut

    aaronhl Senior Member

    Maybe I didn't catch it in the threads, did you have a same exact tests with a different epoxy like west systems under the gelcoat?

    Would you describe the "unhardened" gelcoat as flimsy or stick or mostly uncured, essentially how messy is it? Is it more of an issue like there is a wax layer so the gelcoat just peels off? How stick is the outside?

    Have you left any of the test pieces in the sun to see if they harden any differently?

    I am wondering how you applied the gelcoat and how many layers. Brushing and rolling gelcoat is very hard because each stroke effects the one you just put down so you might be messing with the cure as you brush/roll...

    I am puzzled because I have used the same Raka under gelcoat without issues on my boats, I will do some other tests again
     
  11. Klink Sanford
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    Klink Sanford Junior Member

    I didn't know that the terms were different. I was told by FGCI to apply laminating Vinylester resin over the epoxy, let it dry, then apply the gelcoat within 24 hours. If that is called a tie coat or a barrier coat, I do not know.
     
  12. Klink Sanford
    Joined: Dec 2021
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    Klink Sanford Junior Member

    I fiberglassed the deck about 4 years ago with 2408 biaxial and RAKA 127/606 slow cure epoxy. The glass was laid as one piece 5'X 15' +- , so I needed a slow cure. All of my actual on boat deck tests have been on the same deck, which was laid with RAKA epoxy. IAs far as the gelcoat I used FSD lamianting gelcoat, except for one test I did with some FGCI gelcoat someone gave me. Both did not harden over the boat deck epoxy in all the tests.
     
  13. aaronhl
    Joined: Aug 2012
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    aaronhl Senior Member

    Make up a panel with west system epoxy and put gelcoat over that to see if you have issues, put the gelcoat on the same way to put it on the raka
     
  14. Klink Sanford
    Joined: Dec 2021
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    Location: Sanford FL

    Klink Sanford Junior Member

    I fiberglassed the deck about 4 years ago with 2408 biaxial and RAKA 127/606 slow cure epoxy. The glass was laid as one piece 5'X 15' +- , so I needed a slow cure. All of my actual on boat deck tests have been on the same deck, which was laid with RAKA epoxy. IAs far as the gelcoat I used FSD lamianting gelcoat, except for one test I did with some FGCI gelcoat someone gave me. Both did not harden over the boat deck epoxy in all the tests.

    In my Boat Design thread titled Gelcoat as non-skid on Deck Gelcoat as non-skid on Deck https://www.boatdesign.net/threads/gelcoat-as-non-skid-on-deck.66402/ on page 2 & 3 I have pictures of the gelcoat just peeling off the epoxy, like if it was on wax paper. It was easy to just peel and scrape it off with a spatula, then clean the haze left with a stainless steel wool pad and acetone.

    I applied the gelcoat with a chip brush. The first coat over epoxy just peels off. I am applying it at like 14 mils at most.

    You use RAKA 127/606 slow cure?
    My deck epoxy was layed 4 years ago, maybe in time it exudes something that repels the gelcoat?
    I did the deck 4 years ago, then I turned the boat over and did the bottom, all using epoxy products. Last November I began the work on the deck and bought the gelcoat and it has been one fail after another, the gelcoat just will not harden directly over the epoxy deck. So far, the only way it has hardened is after I have scraped off and sanded the uncured gelcoat like once or twice, so likely what gelcoat sticks/stays behind allows the new gelcoat to stick. You can see the picture of what is left behind in the other three at the end of page 2.
     

  15. Klink Sanford
    Joined: Dec 2021
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    Location: Sanford FL

    Klink Sanford Junior Member

    Like I said before, I am certain that it'll work if I put FGCI epoxy over my RAKA, then the FGCI vinylester, then the FGCI gelcoat, but I'd have to buy the FGCI epoxy, and I have spent enough time on this issue and I am just going to paint the deck with non-skid paint. The reason I made this thread is to warn others that it is no piece of cake to put gelcoat over epoxy for large areas like a deck. I small spot repair OK.

    My conclusion (if I had to do it all over again) is to stick with one company's system, all one brand of every step, in this case FGCI epoxy, FGCI Vinyester, FGCI gelcoat. That way there are no variables. I was never too keen about roll applied gelcoat for a deck as I think it can be a dirt magnet.
     
    fallguy likes this.
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