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Thread: Epoxy / Fibreglass milky on timber canoe

  1. #1
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    Default Epoxy / Fibreglass milky on timber canoe

    Hi
    I am new to boat building and have just acquired a timber strip canoe. Renovation work was done by an antique restorer that I bought it off - he also has boat building experience. The priority is to find out why the epoxy/fibreglass skin on the hull turned increasingly milky over a period of time. The internal hull surface is completely sealed with waterproof paint (lead based unfortunately). The hull timbers were renovated and in very good and dry condition before being coated with fibreglass/clear epoxy. The result was excellent, but over a period of about 20 months, the appearance became gradually milky/opaque but the surface remains glossy and still provides excellent sealing qualities - i.e. I don't think this is amine clouding - it is not a surface problem. It only saw the water 4 times throughout and is very well sealed, with no water penetration throughout.
    I'm going to strip the external hull back to the timber and re-surface but trying to find out what caused the current problem.
    What I know:
    The timber was completely dry before application which was done in warm dry conditions.
    The clear epoxy resin was a brand new tin.
    Other areas covered by epoxy, but not with fibreglass, have not gone milky and remain in excellent condition - See photograph for comparison.
    A UV stabilised marine varnish was painted as a final coating. This is not milky - when sanded back the result underneath remains unchanged.
    It is not patchy - the entire fibreglassed section is getting increasingly milky over time.
    It looked immaculate for the first few months.
    It has been kept under cover throughout - not left in the harsh Australian sun.

    Any advice welcome.

    Thanks
    Chris
    Attached Images Attached Images
    Last edited by Christo64; 10-07-2017 at 06:17 PM.

  2. #2
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    Default Re: Epoxy / Fibreglass milky on timber canoe

    Here is the epoxy/glass hull a few weeks after it was done.IMG_1364.JPG

  3. #3
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    Default Re: Epoxy / Fibreglass milky on timber canoe

    I experienced the same tendency on a boat I built. Interesting that, in my case at least, this occurred on the sides of the hull, but not the deck. I have no answer, but if I build again, I will paint the sides and only do the deck with a clear finish.

  4. #4
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    Default Re: Epoxy / Fibreglass milky on timber canoe

    It's going to be very difficult to remove the epoxy and cloth from the hull. I wouldn't rush into that.

  5. #5
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    Default Re: Epoxy / Fibreglass milky on timber canoe

    How many coats of marine varnish were applied originally?
    - John

  6. #6
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    Default Re: Epoxy / Fibreglass milky on timber canoe

    It appears to be a strip build before epoxy was the "answer" Because the outside only was done.. moisture traveled through the wood and got behind the glass condensed and reacted with the glass and wood acids where they meet. ( just speculation on my part)
    Denise, Bristol PA, Oday30, Anchor Yacht Club, On tidal Delaware River. my current project; http://forum.woodenboat.com/showthre...0-Ducker-Resto

  7. #7
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    Default Re: Epoxy / Fibreglass milky on timber canoe

    Thanks for your response - Chris

  8. #8
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    Default Re: Epoxy / Fibreglass milky on timber canoe

    Hi Dave - I believe it will be a big task ... just not sure how big. I may try a small section and see how it lifts with cross hatching prior to heat gun. At least then if it looks like a big too far, I can just rework that section.
    Thank you for your response
    Chris

  9. #9
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    Default Re: Epoxy / Fibreglass milky on timber canoe

    Hi
    I think 2 coats of UV marine varnish applied some time after the glass/resin set but prior to being exposed to water. I'll find out from the guy I bought it from what the time lag was in between these application. Thanks
    Chris

  10. #10
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    Default Re: Epoxy / Fibreglass milky on timber canoe

    Two coats isn't enough for UV protection.
    If the epoxy us still adhering, I'd sand it back to the epoxy and paint it. If not, I'd build a new canoe.
    Last edited by JimConlin; 10-09-2017 at 05:12 PM.

  11. #11
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    Default Re: Epoxy / Fibreglass milky on timber canoe

    I don't think it is water/moisture penetration from the inside – that usually turns everything black.

    As an aside, there isn't such a thing as waterproof paint really – it may resist water as a liquid, but it won't impede the passage of water vapour as a gas. Generally it's not a specially good idea to epoxy the outside but not the inside, for this very reason - water vapour penetrates the paint but can't escape through the epoxy.

    However - it really doesn't look like that is the problem - it looks more like UV degradation. I'd go with JimConlin and sand it back and paint it.

    Cheers -- George
    To be truly free to live, one must be free to think and speak.

    A C Grayling

  12. #12
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    Default Re: Epoxy / Fibreglass milky on timber canoe

    The only visual reference/test I have seen online of epoxy UV damage is here: http://www.oneoceankayaks.com/Epoxyhtm/epox12m.htm
    Some epoxies have accelerated UV damage over others. With only 2 coats of varnish, I think UV damage is the culprit as stated from the pervious posts.
    - John

  13. #13
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    Default Re: Epoxy / Fibreglass milky on timber canoe

    Certainly looks like moisture - blushing on the bottom of the epoxy - I've seen similar on epoxy resealed pebble stone decks.
    Suspect you used a blushing epoxy (even non blushing epoxies can do this - they all blush to some degree or another). Perhaps made worse (or caused) by being slightly off mix ratio so have some uncured excess hardener (why you never use a 5:1 mix ratio epoxy!)

    nothing wrong with the varnish (and two coats is enough for uv protection) and if the issue was on the top of the epoxy you would have sanded it off. - moisture turns not fully cured epoxy white.

    paul oman
    progressive epoxy polymers inc
    epoxyproducts.com

  14. #14
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    Default Re: Epoxy / Fibreglass milky on timber canoe

    looks like uv damage to me. sand and paint.

  15. #15
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    Default Re: Epoxy / Fibreglass milky on timber canoe

    Quote Originally Posted by paul oman View Post
    Certainly looks like moisture - blushing on the bottom of the epoxy - I've seen similar on epoxy resealed pebble stone decks.
    Suspect you used a blushing epoxy (even non blushing epoxies can do this - they all blush to some degree or another). Perhaps made worse (or caused) by being slightly off mix ratio so have some uncured excess hardener (why you never use a 5:1 mix ratio epoxy!)

    nothing wrong with the varnish (and two coats is enough for uv protection) and if the issue was on the top of the epoxy you would have sanded it off. - moisture turns not fully cured epoxy white.

    paul oman
    progressive epoxy polymers inc
    epoxyproducts.com
    But Paul - the funny thing is that the hull looks OK in the second picture. Milkyness from moisture is sometimes blush, sometimes over-aeration of the epoxy and sometimes moisture while applying it, but don't all of those things tend to show early? Other than chalking from UV, I've not seen moisture affect the resins post-cure, much.

    People also tend to forget that even UV filtering varnish doesn't last forever - you need to re-apply it over time after the components in the varnish that protect from the UV start to "give up the ghost".
    "The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails."
    -William A. Ward



  16. #16
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    Default Re: Epoxy / Fibreglass milky on timber canoe

    (why you never use a 5:1 mix ratio epoxy!)
    That statement is total B.S. from a guy selling a product which has nowhere near the track record or industry acceptance of the brand(s) he is dissing. Ignore it! If his product is good, he should be trying to sell it on its merits, not by making meaningless and false statements about his competitors. Some of them have done vastly more research, testing and customer education than he has by a very, very long shot.

    If we can assume that the epoxy (all coats of it through the process) was measured and mixed properly, then once it hardened it should be pretty impervious to serious moisture damage from both inside and out. On canoes glassed only on their outsides, you may increase the chances of wood rot next to the glass from trapped moisture (though even this is debatable. It is possible to make the case that that wood next to the epoxy and glass is the least likely to rot on the entire boat) If the epoxy work was good from the start, UV damage would seem to be the most likely cause for what we appear to be looking at. Not actually knowing anything about the application, mixing, resin type and brand, etc. it's hard to say what the problem is. It's also pretty common for folks to do dumb stuff to their epoxy projects in a misguided effort to "clean" the surface before resin application with solvents, or dilute it for theoretically deeper penetration with something that seriously compromises its ability to work properly. If you buy a boat where somebody else did the resin work, you are unfortunately taking a chance that they may or may not actually know what they are doing. We also occasionally see people using the term "epoxy" for any resin application, including polyester resin, which is much more prone to problems when used on wood.

    I would suspect that if it was a moisture problem and that widely spread over the hull, you might notice the hull gaining weight and/or the paint lifting and bubbling on the interior. Its bond is likely weaker than that of the resin. Moisture under the glass will also tend to weather the wood to a grey or blackish color, which happened a lot on the early polyester strippers, though it was generally concentrated in specific areas, rather than uniformly. UV filters, as mentioned don't last forever and get used up as they do their job. The boat being "under cover" can have a lot of different meanings. Some covers and covering materials pass greater amounts of UV through them than others, some tarp materials, for example, pass quite a bit.

    I would think it would be pretty rare (especially when so extensive and relatively uniform) but fiberglass can be "stretched" when wooden hulls heat up and the wood expands a bit. It may not be seriously compromised, strength-wise, but it can get lots of tiny white-ish micro fractures deep down inside the yarns. These are permanent, and suddenly you begin to see the cloth which had previously been very transparent. Usually though, the weave pattern becomes pretty obvious and you may even get some telegraphing, where a slight woven texture starts showing up on surfaces which had originally been perfectly smooth. A problem caused by just the resin and UV wouldn't normally do that until the deterioration got extreme.

    I think I'll join the camp saying if the stuff is still hard and sound, I'd paint it a nice color and go paddling. Removal is possible, but it's going to be an awful lot of hard work.

  17. #17
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    Default

    Quote Originally Posted by Todd Bradshaw View Post
    That statement is total B.S. from a guy selling a product which has nowhere near the track record or industry acceptance of the brand(s) he is dissing. Ignore it! If his product is good, he should be trying to sell it on its merits, not by making meaningless and false statements about his competitors. Some of them have done vastly more research, testing and customer education than he has by a very, very long shot.

    If we can assume that the epoxy (all coats of it through the process) was measured and mixed properly, then once it hardened it should be pretty impervious to serious moisture damage from both inside and out. On canoes glassed only on their outsides, you may increase the chances of wood rot next to the glass from trapped moisture (though even this is debatable. It is possible to make the case that that wood next to the epoxy and glass is the least likely to rot on the entire boat) If the epoxy work was good from the start, UV damage would seem to be the most likely cause for what we appear to be looking at. Not actually knowing anything about the application, mixing, resin type and brand, etc. it's hard to say what the problem is. It's also pretty common for folks to do dumb stuff to their epoxy projects in a misguided effort to "clean" the surface before resin application with solvents, or dilute it for theoretically deeper penetration with something that seriously compromises its ability to work properly. If you buy a boat where somebody else did the resin work, you are unfortunately taking a chance that they may or may not actually know what they are doing. We also occasionally see people using the term "epoxy" for any resin application, including polyester resin, which is much more prone to problems when used on wood.

    I would suspect that if it was a moisture problem and that widely spread over the hull, you might notice the hull gaining weight and/or the paint lifting and bubbling on the interior. Its bond is likely weaker than that of the resin. Moisture under the glass will also tend to weather the wood to a grey or blackish color, which happened a lot on the early polyester strippers, though it was generally concentrated in specific areas, rather than uniformly. UV filters, as mentioned don't last forever and get used up as they do their job. The boat being "under cover" can have a lot of different meanings. Some covers and covering materials pass greater amounts of UV through them than others, some tarp materials, for example, pass quite a bit.

    I would think it would be pretty rare (especially when so extensive and relatively uniform) but fiberglass can be "stretched" when wooden hulls heat up and the wood expands a bit. It may not be seriously compromised, strength-wise, but it can get lots of tiny white-ish micro fractures deep down inside the yarns. These are permanent, and suddenly you begin to see the cloth which had previously been very transparent. Usually though, the weave pattern becomes pretty obvious and you may even get some telegraphing, where a slight woven texture starts showing up on surfaces which had originally been perfectly smooth. A problem caused by just the resin and UV wouldn't normally do that until the deterioration got extreme.

    I think I'll join the camp saying if the stuff is still hard and sound, I'd paint it a nice color and go paddling. Removal is possible, but it's going to be an awful lot of hard work.
    I'm with Todd, paint or live with it. I'm almost willing to bet the person that restored it, actually left it out in the sun way longer then the current owner was led to believe!

    Sent from my LG-M430 using Tapatalk
    Denise, Bristol PA, Oday30, Anchor Yacht Club, On tidal Delaware River. my current project; http://forum.woodenboat.com/showthre...0-Ducker-Resto

  18. #18
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    Default Re: Epoxy / Fibreglass milky on timber canoe

    Quote Originally Posted by DeniseO30 View Post
    I'm with Todd, paint or live with it. I'm almost willing to bet the person that restored it, actually left it out in the sun way longer then the current owner was led to believe!

    Sent from my LG-M430 using Tapatalk
    Likely.

    Nick Schade has a good video about using a heat gun to strip old fiberglass from a canoe. If you've got the right equipment, good ventilation and patience, you can do that. It's probably less work to start from scratch, however.
    "The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails."
    -William A. Ward



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