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Thread: Order of epoxy, fairing, paint and what is required?

  1. #1
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    Default Order of epoxy, fairing, paint and what is required?

    After a year and a half away from what was already very slow progress, I'm getting back to it. I'm at the "considering paint" stage of my ilur build and looking for advice. I think I want to paint the bilge area now, the rest of the inside once i've done some more work, and i'll be flipping back upside down at a later date for the exterior.

    I think i probably want to use 2 pack paint, and will be incompetently painting by hand.

    Boat won't be stored in the water.

    My question is - should I have a coat of epoxy first? or is the 2 pack primer/paint designed/enough? I suppose i'm asking about the exterior primarily, as i would guess that's the most at risk.

    Exterior is still bare plywood and not faired - for that, should I apply a full epoxy coat first anyway, then fair from that? (which would likely result in a few spots back to the wood anyway..) if so this is probably a moot point anyway. I'm not planning on a particularly fine finish for the area under the floorboards, so there an epoxy coat wouldn't be too much hardship anyway, if beneficial.
    If it's not the done thing, do you normally apply a neat epoxy coat before fairing mix for a specific spot, like I have been before a fillet?

    I know from experience that my ability to apply a smooth full coat of epoxy with no drips or blobs or chip brush bristles to clear up later is pretty limited, so if i can avoid that. all the better!

  2. #2
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    Default Re: Order of epoxy, fairing, paint and what is required?

    There is really no one way to do it, ten people will find ten ways.They may all be right.
    The difficulty of applying epoxy resin compared to a formulated epoxy barrier coat is real. One drips , sags and blushes and one does not .
    Then throw a CPES primer in there, you have even more options.

  3. #3
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    Default Re: Order of epoxy, fairing, paint and what is required?

    Quote Originally Posted by wizbang 13 View Post
    There is really no one way to do it, ten people will find ten ways.They may all be right.
    The difficulty of applying epoxy resin compared to a formulated epoxy barrier coat is real. One drips , sags and blushes and one does not .
    Then throw a CPES primer in there, you have even more options.
    of course! I just need one of you to sound convincing, really

    When you say formulated epoxy barrier coat, do you mean a paint primer, or is this another product i'm not aware of?

  4. #4
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    Default Re: Order of epoxy, fairing, paint and what is required?

    A product like Interlux 2000

  5. #5
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    Default Re: Order of epoxy, fairing, paint and what is required?

    Quote Originally Posted by jeffcapeshop View Post

    Exterior is still bare plywood and not faired - for that, should I apply a full epoxy coat first anyway, then fair from that?
    If you are using an epoxy based fairing you should first coat the surface with neat epoxy. The fairing coat will adhere much better than on bare wood, especially if the neat coat is still a bit green. After fairing be sure to re-coat the sanded fairing coat with neat epoxy. Fairing compounds have a micro texture that will telegraph through the paint coat if left unsealed. DAMHIKT.

  6. #6
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    Default Re: Order of epoxy, fairing, paint and what is required?

    The deal there is that one of the most common "powders" mixed into resin to thicken it and make fairing compounds are phenolic microballoons, which are actually tiny hollow tan-colored spheres of phenolic resin. They make a lightweight, easily sanded paste-like compound. Once dry and sanded smooth though there is one small problem. The sanding tends to cut open some of the tiny spheres at the surface. These cut open spheres are full of air. They are so small, that paint won't flow into them, it just bridges over the cut open part. This normally looks fine to start with. Eventually though, the sun heats up the boat, the air expands in these tiny craters and it pops the film over their open tops. This leaves lots of tiny (ugly) pinholes in your paint job.

    To prevent this you need to overcoat the sanded and faired area with a thin coat of epoxy, which is strong enough to bridge the craters and not allow them to later pop open. Unfortunately, this then involves one more round of light sanding to smooth the final epoxy layer, followed by paint for color and to protect the epoxy from UV. So your first coat on bare wood should be a plain epoxy/hardener mixture for maximum bond to the wood, followed by your fairing filler, then a last coat of epoxy, light sanding and then finally the paint system of your choice. I even saw one boat that was dark green over white paints without the final epoxy layer over the fairing compound. The white had a few pinholes, but the green was very evenly covered with them - so dark colors which heat up more in the sun would seem to be more of a potential problem.

  7. #7
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    Pittwater, NSW, Oz
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    Default Re: Order of epoxy, fairing, paint and what is required?

    A slightly simpler sequence, which works well is: neat epoxy coat; fairing compound (epoxy + microballoons); epoxy paint (Interprotect, etc); 2-pack urethane paint. Sanding between each step.
    For a yacht finish, mulitiple coats of Interprotect with rigorous sanding (+guide coats) inbetween (plus maybe a few fairing steps!) till the required fairness and smoothness is reached.
    The TDS of your chosen 2-pack PU paint should give you all the detail you need.

  8. #8
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    Default Re: Order of epoxy, fairing, paint and what is required?

    Thanks guys - hard graft it is! going to be far from a "yacht finish" but I want to avoid too many avoidable flaws, obviously. Will skip the fairing compound under the floor, don't tell anyone.

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