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Thread: To coat or not to coat with epoxy!!! Help!

  1. #1
    Join Date
    Jul 2017
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    Lostine, Oregon
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    Default To coat or not to coat with epoxy!!! Help!

    Ok, we need some expert advise. Building a whitewater dory. Finished with our final fairing on the deck and coated with a final coat of epoxy. Had a lot of air bubble and grapefruit texture. Such a bummer since our final fairing was great. Ten hours of sanding later the epoxy looks somewhat smooth and the paint looks pretty good. But not looking forward to having the same experience on the nicely faired hull. So....., can we bypass the final coat of epoxy? Thoughts? Painting with Kirby's Marine paint.

    Thanks,
    Nicole

  2. #2
    Join Date
    Jun 2000
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    Madison Wisconsin
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    Default Re: To coat or not to coat with epoxy!!! Help!

    Epoxy resin is not paint or varnish and no matter how you apply it, it does not leave a perfectly smooth surface like paint or varnish can. You will probably get some orange-peel texture (often with rather big bumps). It will nearly always need to be sanded smooth after it cures for a good looking surface that will paint or varnish nicely. Your "final fairing" actually takes place after all the resin coating is done, not before.

    Air bubbles can be "made" by using too much roller pressure, the wrong type of roller cover, rolling too quickly, or from air coming out of the wood after the resin was rolled or brushed on and getting trapped in the resin. One way to help prevent this outgassing is to do your epoxy work when the outside temperature is dropping, rather than going to rise as the day progresses. You can also help "grain-fill" some woods with big pores by applying a very thin coat of resin which is basically scraped into the grain (and off of the surface) with a piece of plastic, like an old credit card. This will help fill pores which might be prone to outgassing. If your wood's grain is likely to raise when the resin hits it, this scrape-coat will also solidify it, allowing a light sanding to cut it down to smooth again. Once hardened enough that you won't disturb the scraped-on coat, the following resin coats can begin. Obviously, if it's a really big area, this may be more trouble than it is worth.

    This isn't a boat (well duhhhh) but the top of this mandolin body was covered with veneer set in epoxy and then epoxy scrape-coated and then top-coated, three layers thick. You can clearly see the orange peel texture in the resin after coating in the top photo. The usual treatment for resin coating that will later need to be faired and finish sanded is to apply three thin coats - two coats to do the actual sealing, and a third to allow you to sand it smooth without reducing your coating thickness and sealing capability too much. After sanding the resin smooth and varnishing, the final result is in the bottom photo.



    edited to add: Whether or not you can skip the resin coating on the hull is pretty much a matter of what materials and construction you are using. Some boats do just fine with nothing more than paint. Others don't.

  3. #3
    Join Date
    Jan 2004
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    Newport News, VA
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    Default Re: To coat or not to coat with epoxy!!! Help!

    I would not put on more epoxy, that your just going to sand smooth and lose as dust in the wind.

    How about build up layers of sandable primer coats, sand that smooth, then paint.
    I used this in the spray version, and was easy to sand smooth and filled in surface defects.

    If the defects are too deep, use some sandable filler.


    http://www.homedepot.com/p/Rust-Oleu...B&gclsrc=aw.ds

  4. #4
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    South Devon UK
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    Default Re: To coat or not to coat with epoxy!!! Help!

    I am not an expert on marine painting but it doesnt seem necessary to apply a coat of pure epoxy resin over smooth finished filler (presumably epoxy filler). I have used Pengaurd hi-build primer over epoxy filler, then a topcoat of two pack polyurethane. I found that two coats of Pengaurd hi-build sanded down would completely fill the weave in a sheathing of woven glass cloth. I only needed a small amount of epoxy filler where there were more major irregularities than the weave of the cloth.

    I briefly worked in the large yacht industry and we only used Awlgrip products for painting. The boss had the idea, right or wrong, that epoxy filler needs to be sandwiched each side by a waterproof layer so we would generally apply the special very low viscosity Awlgrip primer over the substrate which was usually carbon fibre/epoxy laminate, then we would fill and fair with epoxy filler, then apply several more coats of the Awlgrip primer followed by very light sanding before the Awlgrip top coat. I suspect that the primer between the laminate and the filler was unnecessary.

  5. #5
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    Default Re: To coat or not to coat with epoxy!!! Help!

    If you are 10 hours sanding the deck of a dory , you need more than help with epoxy opinions. You need a better sander as well.
    Combining epoxy with Kirbys is a bit daft.Two extremes .Kirbys straight on epoxy resin may not dry for weeks.
    Anyway , I would recommend a two part epoxy "barrier" coat, (interlux 404/414),between the epoxy resin and whatever you top coat with.
    bruce

  6. #6
    Join Date
    Jul 2017
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    Lostine, Oregon
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    Default Re: To coat or not to coat with epoxy!!! Help!

    Gosh Bruce, way to make a girl feel belittled. I was looking for advice and I understand everyone has an option....., but really!

  7. #7
    Join Date
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    Default Re: To coat or not to coat with epoxy!!! Help!

    Oh I am a nice fellow in real life, just have a habit of getting to the point.
    Ten hours of sanding... just trying to help.
    The 404/414 IS epoxy. It behaves like paint. It will not drip, run ,bubble or blush like resin.

  8. #8
    Join Date
    Jan 2017
    Location
    Rat Beach, CA, USA
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    Default Re: To coat or not to coat with epoxy!!! Help!

    Quote Originally Posted by sdowney717 View Post
    I would not put on more epoxy, that your just going to sand smooth and lose as dust in the wind.

    How about build up layers of sandable primer coats, sand that smooth, then paint.
    I used this in the spray version, and was easy to sand smooth and filled in surface defects.

    If the defects are too deep, use some sandable filler.
    What he said...just apply the KISS principle and move on to the next stepl

    Thanks for posting this question, helps me too!

    PS, not an expert, just looking for ways to fix epoxy finishes.
    Last edited by FishoutaFlorida; 07-20-2017 at 12:44 AM. Reason: clarification of qualifications.
    Please don't dominate the rap Jack, if you've got nothing new to say.

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