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Thread: Repairing wavy hull epoxy

  1. #1
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    Default Repairing wavy hull epoxy

    I have a cedar strip canoe with epoxy and glass that I built a few years ago. I do quite a bit of wood working- so It's really a stunning canoe.

    Heres the problem though- this was my first time working with epoxy and glass. It turned out fine but I feel the just okay epoxy job is holding the rest of the canoe back. I saw an ultra smooth canoe in a store the other day and it got my ire up...I have a lot more epoxy experience At this point and know I could do a much better job if I did again

    Im thinking of sanding down the hull and re- applying a light finish coat of epoxy to get a perfect smooth surface.

    Heres my challenge. The epoxy hull is slightly wavy in a vertical way- not the hull itself, just the epoxy. It's very faint but definitely noticble in the right light. Maybe 1/32 or so at the most spread out every 12 inches across the length of the hull (which is probably the width of a sanding pass). I know what I did and that was to too aggressively sand originally.

    Does anyone have any good techniques for getting out the waves? Scrapings not really an option as it's not a defined small wave here and there but rather an entire hull. I Have a feeling a new coat of epoxy without removing the waves would just repeat the pattern- though diminish it some.

    Thank you for your expertise in advance.

  2. #2
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    Default Re: Repairing wavy hull epoxy

    Trick is , sanding the waves out without removing any of the glass.
    An RO is a smoothing tool , not really a fairing tool.
    Hand sanding them with a torture board may be what is needed in your quest for perfection.

  3. #3
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    Default Re: Repairing wavy hull epoxy

    Guessing the cloth wasn't set well and floated off. Why squeegees are used,
    Did you varnish? Sanding varnish will give you yellowish dust, epoxy dust is whiteish and you have to sand until you have all tge varnish off, it's a miserable job! Live with it, would be my suggestion. Or buuld a stunning canoe 3 of ours were super smooth wet sanded shiny boats, but then we stsrted using them. Good luck
    Denise, Bristol PA, Oday30, Anchor Yacht Club, On tidal Delaware River. my current project; http://forum.woodenboat.com/showthre...0-Ducker-Resto

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    Default Re: Repairing wavy hull epoxy

    The only way to get fair shape is a longboard.
    If you can get a fair surface before you hit the glass, that's fine. This is less than probable.
    Best to just build another canoe.

    I have two strip canoes. The first one has the 'character' you describe, more filler between stripst han I hoped for and assorted dings. It gets used.
    The second boat is closer to perfect. It's hung indoors and collects dust.
    Different boats for different purposes.

  5. #5
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    Default Re: Repairing wavy hull epoxy

    Quote Originally Posted by DeniseO30 View Post
    Guessing the cloth wasn't set well and floated off. Why squeegees are used,
    Did you varnish? Sanding varnish will give you yellowish dust, epoxy dust is whiteish and you have to sand until you have all tge varnish off, it's a miserable job! Live with it, would be my suggestion. Or buuld a stunning canoe 3 of ours were super smooth wet sanded shiny boats, but then we stsrted using them. Good luck
    Cloth was well set, and adhered well. Few bubbles if any. Squeegeed well. I did a pretty good job with the base coat surprisingly for my first time. I think the waves are the result of trying to over sand the runs to smooth them out with the RO. I should have scraped more and sanded less.

    Sounds like consensu is going to town with a long torture board is probably my best bet. Hopefully that will even out The waves.

  6. #6
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    Default Re: Repairing wavy hull epoxy

    trouble with using clear epoxy to "fill" in low spots is the hardness. Gad that stuff is hard to sand! I've had good luck with the "ceramic" type paper. Trouble is the high spots will sand through to the cloth. not a good thing.

    Jim I'm with yah. Got my first strip canoe and my last wood canvas in the basement. all the boats in between are gone sold or given away. My prospector that I loved, was given to one daughter and it's sitting outside unused and covered in mold and mildew The redbird was sold off by my son for dubious reasons.. The Wood canvas form I gave to Phila boat factory, a private outfit that "teaches" kids about boats and building. I still want to get back on the water.. but..eh, "maybe tomorrow"
    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: Repairing wavy hull epoxy

    The thickness of a single epoxy filler coat is very minimal. In fact, two layers of six ounce cloth when resin saturated and with the weave filled is literally very similar to the wall thickness of a plastic milk jug. If you don't believe it, make a sample on a sheet of waxed paper or polyethylene of two properly saturated and squeegeed layers of cloth and enough filler coats to hide the weave and see for yourself. If your glass is down tight to the wood and the ripples are actually in the filler coats, not the wood, then they would be pretty shallow ripples. I don't know why you couldn't add two or three more thin, rolled-on filler coats and than give sanding it fair and smooth another shot - either long-boarding or with a random orbit. I'll normally roll on five or six thin coats when filling glass weave or barrier coating, so don't freak out about the number of coats. Thin coats are less likely to sag and drip.

    You will need to sand the varnish off first, which as noted is a pain in the ass. I did that on my big fur trade canoe before painting it and honestly, I'd rather sand epoxy than varnish if I had the choice. I used 80 grit disks on the random orbit machine, changing them frequently as they plugged up and it probably took about 3 hours of actual sanding time on my 22' canoe. Compared to the suggestions to just build another boat, some sanding, re-filling and fairing is a lot less work if that's all it needs.


    The yellow boat on the bottom is a normal 16' Old Town. The big boat on top is the one where I sanded off all the old varnish. It wasn't the most fun I've ever had while boatbuilding, but it wasn't all that awful.


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    Default Re: Repairing wavy hull epoxy

    "Did you varnish?"

    Painted or clear finish? Sorry if I missed this. / Jim

  9. #9
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    Default Re: Repairing wavy hull epoxy

    Quote Originally Posted by chas View Post
    "Did you varnish?"

    Painted or clear finish? Sorry if I missed this. / Jim
    yes. That will of course have to be sanded off

  10. #10
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    Default Re: Repairing wavy hull epoxy

    I did ask because there are people that will not varnish clear epoxy even though everybody knows the ultraviolet will destroy it in short order good luck!
    Denise, Bristol PA, Oday30, Anchor Yacht Club, On tidal Delaware River. my current project; http://forum.woodenboat.com/showthre...0-Ducker-Resto

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    Default Re: Repairing wavy hull epoxy



    15'2" X 32; solo Ribs are one color. it's the bad lighting. Really need to do the canvas "someday"



    18ft HW old town. I'm sure the guys here are tired of seeing my pics LOL



    Prospector, (canoe craft)



    Redbird (canoe craft
    Denise, Bristol PA, Oday30, Anchor Yacht Club, On tidal Delaware River. my current project; http://forum.woodenboat.com/showthre...0-Ducker-Resto

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    Default Re: Repairing wavy hull epoxy

    There are also a surprising number of folks who don't ever sand their filler coats smooth before varnishing. It really looks awful because no matter what they do, epoxy is not going to go on smoothly like paint or varnish. I remember back about 1980 or so when Old Town decided they were going to sell kits for strippers, along with all their standard canoes. We saw the two samples they had been advertising the program with at their booth at the National Sporting Goods Show. The wood work was OK, but they were nicely covered with sags, drips, waves and little lumps of epoxy because nobody bothered to sand them smooth. We had a good chuckle and unfortunately, I still occasionally see "professionally" built strippers like that for sale at shows.

  13. #13
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    Default Re: Repairing wavy hull epoxy

    Welcome to the forum, Griz. I think you've got the answer to your problem in the posts by Todd and Denise. It's a situation, not an emergency, and not a reason to have a viking funeral bonfire. "It" is, almost always, just Another Learning Opportunity. I look forward to pics of the canoe as you progress toward that mirror smooth final finish!

  14. #14
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    Default Re: Repairing wavy hull epoxy

    Making a hull really fair, and having a perfectly clear finish are contradictory goals. You can add epoxy to the low spots and progressively, by hours of sanding make surface mirror smooth and fair. The problem will be that the different thicknesses of epoxy with refract differently, and you may notice it. That is before anything bad happens, like one layer gets contaminated or milky for some reason. In which case you enter the Icarus state ruining something that was pretty good trying to make it perfect. Usually the wood grain does a pretty good job of hiding any pesky unfair bits. If the problem is just in the epoxy flow coat, wet sanding with a long board and re coating is all you can do. Often after you have done everything and feel it is perfect, the sun comes out and it all moves again. The Germans say "The tree isn't dead until it burns."

    SHC

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    Default Re: Repairing wavy hull epoxy

    Quote Originally Posted by SHClark View Post
    Making a hull really fair, and having a perfectly clear finish are contradictory goals. You can add epoxy to the low spots and progressively, by hours of sanding make surface mirror smooth and fair. The problem will be that the different thicknesses of epoxy with refract differently, and you may notice it. That is before anything bad happens, like one layer gets contaminated or milky for some reason. In which case you enter the Icarus state ruining something that was pretty good trying to make it perfect. Usually the wood grain does a pretty good job of hiding any pesky unfair bits. If the problem is just in the epoxy flow coat, wet sanding with a long board and re coating is all you can do. Often after you have done everything and feel it is perfect, the sun comes out and it all moves again. The Germans say "The tree isn't dead until it burns."

    SHC
    thanks good points.

    I'm not planning on spot filling low spots- the waviness is too minute for that anyways. I think I have enough room with the existing epoxy coat that if I use a long enough (20"+) board I can remove the high spots of epoxy with only barely even getting into the low spots. It's elbow grease... but This is the best case scenario I believe. If that works I can simply revarnish.

    If if I have to sand a little more, then I'll probably rough sand for max adhesion and need a very light skim coat of epoxy or two which I'll roll on then sand fair again and then varnish.

    What at do you guys think?

    Ill see see if I can upload a photo of the waves in the right light so you can see what I'm dealing with.

  16. #16
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    Default Re: Repairing wavy hull epoxy

    Most of us use a photo hosting site I use Photobucket and direct link it to the insert photo icon on the page I've not had good luck trying to fair epoxy like you would drywall compound
    Denise, Bristol PA, Oday30, Anchor Yacht Club, On tidal Delaware River. my current project; http://forum.woodenboat.com/showthre...0-Ducker-Resto

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    Default Re: Repairing wavy hull epoxy

    Reading all the comments here makes me not feel so bad about my own difficulties in getting a perfectly fair epoxy surface.

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    Default Re: Repairing wavy hull epoxy

    So I started on this last night and wow I knew this was no picnic, but this is a tough job. That varnish was the worst part by far. I spent about 4 hrs with a torture board going to town last night. It's funny how now I think the unevenness of the hull was actually worse than I thought. It's quite apparent once you hit it with a fairing board where the high spots are. The waves are even more minute than I thought but there are a lot more of them. Here's a couple observations

    - I started with sandpaper sheets - 40 grit but kept cloggining it due to the varnish. I switched to a 40 grit belt. IMO this is the ONlY way to do it. It doesn't clog near as often. I've done the entire thing with ONE belt.

    - i used a wire welding brush to brush out the varnish when clogged.

    - the epoxy sands well just like I thought it would.

    -I originally was hoping to just sand down the epoxy to smooth without getting into the weave. Unfortunately there are a few spots where this isn't going to work and I'm down to the weave. This means I'll have to skim coat a few light epoxy coats with a roller before finishing.

    - 40 grit should be best for mechanical adhesion of new coat.

    - I'm going to Do a spar urethane instead of varnish.

    -cloth is down nice and tight to hull EXCEPT right near the gunwales where it must have pulled away slightly due to gravity and the tumblehome- makes sense. . This is where it's really tough to sand. This is the hardest part to get ultra fair.

    I can't upload pictures - too large. Bummer.





    Ill keep everyone posted.
    Last edited by Grizzly man; 06-17-2017 at 08:16 AM.

  19. #19
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    Default Re: Repairing wavy hull epoxy

    Oh geeze.
    Denise, Bristol PA, Oday30, Anchor Yacht Club, On tidal Delaware River. my current project; http://forum.woodenboat.com/showthre...0-Ducker-Resto

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    Default Re: Repairing wavy hull epoxy

    40 grit is much coarser than you really need for the new stuff to bond. As long as it is clean and free of contamination, 80 grit or so should be fine. Wash it down with a sponge and clean water when you are done sanding. It will give you a brief preview of how it will look for fairness and color, as well as help to point out any spots which might be contaminated and repel the water (and possibly later, the topcoats). I kind of cringe when I hear epoxy surfaces and wire brushes being used in the same sentence, as they strike me as a potential contamination source, but that might just be in my imagination.

  21. #21
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    Default Re: Repairing wavy hull epoxy

    I've, and I'm sure many others have learned that; "help" is usually taken badly by the person they are trying to help.

    "So I started on this last night and wow I knew this was no picnic, but this is a tough job. That varnish was the worst part by far. I spent about 4 hrs with a torture board going to town last night. It's funny how now I think the unevenness of the hull was actually worse than I thought. It's quite apparent once you hit it with a fairing board where the high spots are. The waves are even more minute than I thought but there are a lot more of them. Here's a couple observations

    - I started with sandpaper sheets - 40 grit but kept cloggining it due to the varnish. I switched to a 40 grit belt. IMO this is the ONlY way to do it. It doesn't clog near as often. I've done the entire thing with ONE belt. "


    I've known about these for years but most likely never will get one.

    -" i used a wire welding brush to brush out the varnish when clogged. "
    A rubber block will clean sandpaper also.

    "- the epoxy sands well just like I thought it would. "
    yes and no. but only when mixed with cabosil it's like stone

    "-I originally was hoping to just sand down the epoxy to smooth without getting into the weave. Unfortunately there are a few spots where this isn't going to work and I'm down to the weave. This means I'll have to skim coat a few light epoxy coats with a roller before finishing. "
    No way to avoid sanding the cloth, Maybe a heat gun and scraper to remove the mess and start over would have been a more practical approach

    "- 40 grit should be best for mechanical adhesion of new coat. "
    Epoxy doesn't need mechanical adhesion it bonds chemically, but sanding is a good thing if it's shiny or still have residue on it.

    - I'm going to Do a spar urethane instead of varnish.
    seek the highest UV protection you can find.

    -cloth is down nice and tight to hull EXCEPT right near the gunwales where it must have pulled away slightly due to gravity and the tumblehome- makes sense. . This is where it's really tough to sand. This is the hardest part to get ultra fair.

    Yeah.. heat gun and scraper.. start over. stinky and messy but lots less muscle

    I can't upload pictures - too large. Bummer.

    upload from URL this site doesn't work well for attachments. Maybe it's an old version of forum software.
    From you choice of photo hosting site. direct copy the URL and paste, REMEMBER TO UNCLICK "
    Retrieve remote file and reference locally" which seems to be the cause of "too large" good luck!
    Last edited by DeniseO30; 06-17-2017 at 01:02 PM.
    Denise, Bristol PA, Oday30, Anchor Yacht Club, On tidal Delaware River. my current project; http://forum.woodenboat.com/showthre...0-Ducker-Resto

  22. #22
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    Default Re: Repairing wavy hull epoxy

    Well after a lot of sanding I'm on my way to the finish i was looking for. 1 layer of epoxy is on already and I'll add another 2-3 thin coats today- just enough to be able to sand down smooth and perfectly fair. Right now it's somewhat tacky so ready for another coat after typing this and when checking the high shine by angling a spoltlight I hardly see any perceptible waves. I'll then sand perfectly fair with 120 on a board and 220 on the ROS after all the coats have cured.

    A couple of additional thoughts. The biggest challenge with this whole project was getting ALL the old varnish off. Even after fairing and with no percetiplble difference in smoothness of hull, there was still many micro spots and valleys with varnish left in them. Sand as I might it was darn near impossible to get these out without gouging a small depression- which would defeat the purpose. I couldn't even see the spots until I'd hit it with the hose and the color difference would show up in the sun. i went and got some varnish stripper and applied to the hull. I Let sit for 30 min and then went back over with a ROS. This got the majority but there weere still quite a few spots. The good things is the stripper caused the tiny spots to develop a different consistency which was easy to find in the sun and I went through and hand sanded them all out with folded over sandpaper always in the longitudinal dieection.

    Sorry but I don't have a photo sharing account like photobucket and am not going to go through the trouble of setting one up- otherwise I'd show pics.

  23. #23
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    Default Re: Repairing wavy hull epoxy

    How do you apply the epoxy coats, to the low areas only, or evenly over the entire hull? / Jim

  24. #24
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    Default Re: Repairing wavy hull epoxy

    Quote Originally Posted by chas View Post
    How do you apply the epoxy coats, to the low areas only, or evenly over the entire hull? / Jim

    I've got most of the low spots worked out before epoxy coat except for the faintest bit- so I'm just going evenly over the entir hull and I can fair those spots after it curesbefore finish. I'm not sure there's a better way on a cedar strip since everything needs to be even or you'll see the difference in the clear coat.

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