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Thread: Ply stich and glue canoe refurb

  1. #1

    Default Ply stich and glue canoe refurb

    Hi, been on here a while but just lurking really looking for a cheap boat and I recently picked up a second hand ply boat needing some tlc.

    I have stripped the old peeling epoxy to let the thing dry out and found the base has some green staining from being wet for some time but is completely solid, how should I treat this, if at all?

    Appreciate any advice you can offer

    Thanks
    Ben

  2. #2
    Join Date
    May 2010
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    I'm assuming the resin that was peeling off was a coating (probably not epoxy as it shouldn't peel), and what you have is algae on the bare plywood. There are various remedies and products for getting algae off wood, traditional ones like water with bleach and soap (Google them) and modern products designed for decking, etc. I've used a product called 'wet & forget" which works well and is probably less damaging to the wood than bleach.

  3. #3

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    Thanks Chris B, yeh I assumed it was degraded epoxy but more likley varnish I guess. I'll check out the 'wet and forget'

    Cheers

  4. #4

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    Another question... I have areas of varnish that are sound, if well keyed will epoxy adhere OK to the varnish?

    Thanks

  5. #5
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    May 2010
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    I've never tried epoxy over varnish so I can't say for sure, but my instinct is against it. Whether they will react may depend on what kind of varnish it is, but I think of epoxy as penetrating deeper into the wood and having more through-thickness strength, so I don't think the result will be as effective, even if they don't react. But I could be wrong.

  6. #6
    Join Date
    Nov 2007
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    very soon to be norfolk
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    why put epoxy over varnish?

  7. #7

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    I'm glassing the boat to add strength, it was glass taped on the joints and the rest of the panels just varnished some of which is sound but the majority has failed

  8. #8
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    aaah. That explains it. Don't forget to varnish on top of the epoxy for UV protection.
    Sam.

  9. #9
    Join Date
    Jun 2007
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    Hi Blender
    Long time ply boat operator here (ours is 15+ years old and had many refurbs)
    Is the non-epoxied wood on the inside or the outside of the hull?

    If it's on the outside and you try and glass over the taping, you may find you need a lot of epoxy (and thereby adding weight) to eliminate all the bubbles.
    If you sand the tape off you risk the hull's integrity a bit. Check it's taped securely on the inside!
    If it's on the inside, i would be sorely tempted to rub back to sound wood and varnish/paint according to preference. If well maintained, kept indoors / in the garage/ boat-shed /coach-house in a dry place it should last for years with the odd touch up here and there.

    As to adding epoxy over sound varnish - I don't tend to do this, but where a patch is needed on the bottom, for example I just rub back the varnish to the epoxy level, patch the epoxy, rub smooth and varnish over the top.

    One approach to save some work and weight is to just glass-cloth below the "waterline". That's the bit that usually takes the most punishment.

    As ever, a few pictures of what you're working on would help a great deal!
    Last edited by Willpower; 7th-July-2019 at 11:26 PM.

  10. #10
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    Jun 2007
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    One other thought:
    If I were to be contemplating glassing the bottom of a previously varnished boat, I would definitely want to sand the whole area to be glassed and a margin back to the bare wood.
    For this I would be using one of these:
    https://www.amazon.co.uk/Makita-BO60...569787&sr=1-20
    which strikes a good balance between aggressiveness and control (well it does for me anyway). Obviously you don't want to end up taking too much off!

    If I were to be contemplating glassing the inside of a previously varnished boat, I would go and have a long chat with myself as to if it were really necessary or if building a fresh boat and turning the one I had into a bookcase was the easier task.

  11. #11
    Join Date
    Oct 2011
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    I glassed the bottom of my stictch&glue - kinda to prevent gravel rash - sanded the whole of the bottom and the bottom seams. Added to the overall weight, but it's lasted a good few years. The rest of the seams are glass taped, and both inside & outside epoxied. I would see glassing the inside after the event would be a challenge, as getting the current glas tape/epoxy off would be almost impossible. Original build blog - 3 days Birchcanoes course.

  12. #12

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    Hi, thanks for the replies. I glassed the bottom today (outside only), it's pretty much the area below the waterline although I've taken it up the bow and stern joint. The inside I'll just rub back and revarnish. I have three bubbles on the bottom chine joint, should I cut these out now and patch them? Other than some tidying required to the bow and stern I'm quite happy with the finis, it was bloody hard work in the heat. Lesson number one: mix hardeners to slow the cure... Doh!

  13. #13
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    Jun 2007
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    Quote Originally Posted by Blender81 View Post
    I have three bubbles on the bottom chine joint, should I cut these out now and patch them?
    I would.
    Make sure you rub down the area around the cut out and overlap the patch. You'll probably be hard pushed to notice the patch once it's all varnished and whatnot.

  14. #14

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    Thanks Willpower I'll do that, when it's all finished I'll post a pic for entertainment purposes!

  15. #15
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    Jun 2007
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    The other thing I did on mine slightly belatedly was to add an additional layer of glass on the keel line - just 1-2 inches wide - at the stem/stern as this can take bit more of a beating on beaches/river bottoms/rocks depending on the types of paddling you do. If you have enough glass over, cutting this on the bias will make it easier to go round the sharp edge.

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