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Canvas Dilemma

Discussion in 'Wood and Canvas' started by NickD, Jul 24, 2017.

  1. NickD

    NickD Recreational Sander

    So… Just completed my second restoration: a 1919 16’ OT OTCA (made an appearance at this year’s Assembly) and had an issue with the canvas that comes and goes. Here’s what happened including facts that are either pertinent or potentially interesting:

    · Canvas was stretched on the hull in April, I canvas with the canoe right side up, hammock style. I tensioned the canvas without canoe to make sure everything was even then relaxed the canvas, added canoe and re-tensioned. Temperature about 60 or so.

    · Tacked canvas starting from midship moving to each end, one side at a time, leaving the ends open where tacking became difficult.

    · Removed tension, flipped canoe and hand stretched (using canvas pliers) canvas at each end, tacking and keeping as tight as I could get it. Kept high tension on the extreme ends (mid stem) and worked the stem starting from the bottom around to the top. NOTE: I do all my work solo other than putting the canoe in the canvas initially. Also NOTE: Had an issue with the canvas rippling transversally near the bow and stern on the hull due to what I thought was “pull back” from the ends. I had to work the stretched canvas considerably (I thought) to get it smooth. This involved untacking portions, re-stretching and re-tacking. Also ANOTHER NOTE: Ends tacked and completed 2 days after the rest of the canoe was canvased and tacked, ie. total canvasing occurred over three days.

    · At this point canvas is complete, smooth, ends sealed with bedding compound and tacked. I filled the canvas with OT filler and let sit for 5 weeks until it was cured. NOTE: Had the text book ripple of canvas above each tack along most of the hull. At the ends, the ripple was biased to the nearest stem side of the tack.

    · Painted the hull. I sanded the filler lightly and put multiple coats of paint to get to the finish I was looking for. Paint: Interlux Dark Blue.

    · The morning after the final coat, I decided to move the canoe out of the garage for a little while to “air out”. That day turned out to the hottest and sunniest day of the year. About 3 hours later I returned finding the canvas/filler/paint rippled on the hull on the bottom and side facing the sun. The ripples ran transversally across the hull. Hull was very hot to the touch.

    · After a “stern” conversation with myself I expedited the canoe back to the cover of the garage and covered it with cold wet towels to cool it down. Ripples receded somewhat but not completely.

    · Over the next five days (in humid weather) the canvas gradually (miraculously) flattened out.

    · The canvas behaved at Assembly. And paddled quite nicely too.

    · Now, back in the garage, one side at one end has re-rippled mildly. Canoe hasn’t seen water since Assembly.

    Did I do something wrong or is there something I should have done better? How tight is tight then canvassing? My first restoration went very well and I’m worried I was a bit sophomoric on the second go-around. If I let the paint cure longer, protected in the garage, would that have prevented the rippling which I assume was caused by the expansion of the dark, heated, not completely cured, painted surface? I'm thinking that if the canoe gets wet again or it gets really humid, it may flatten again.

    On another note, the day before we left for the Assembly, my wife made an impressive canoe bag/cover out of white bed sheets that survived the trip up to Assembly and back in glaring sun in an effort to prevent re-occurrence. It worked really well.
     
  2. MGC

    MGC Scrapmaker

    Every now and then problems can rear their ugly head...
    Your canvassing process sounds quite normal although you do not mention placing any weight in the hull during the stretching and canvasing. I normally put a few bags of sand or cement inside the canoe while it is sitting inside the lengthwise stretched canvas. I'm not sure what would happen if you don't do that? It's possible that it would make no difference if you consider the upside down method as an alternative. There the canvas tightness relies on the stretching and "pucker" without any vertical force applied.
    I also tend to cure the filler a bit longer than you did. Although I know that folks do sand and paint sooner I tend to let it sit for at least 6 weeks and possibly more. Paint is not likely to be your problem...it's (in my opinion) more likely how you stretched the canvas and the filler.

    At this point you are sort of committed to the result. What you can do is to always try to paddle with the puckering side away from the sun or more realistically you might try to re-tack the canvas. There are and have been builders that re-stretch and re-tack after the filler is dried.
     
  3. Paul Scheuer

    Paul Scheuer LOVES Wooden Canoes

    I might have missed it, but I didn't see the "wash down with hot water to slightly shrink the canvas" part. Was it done ? (For the record, I've never re-canvased, but there is one in my future).
     
  4. Howie

    Howie Wooden Canoe Maniac

    For what it's worth... I had a wrinkle problem a while back that sounds a little like yours - except that mine showed up a few days after I mudded it. Only time I ever had a problem. I ended up ripping it off & doing it again. At first I could only think I got a batch of bad filler, or maybe the weather was too extreme (we went from 70 deg to 30 deg in a few days), but in retrospect that seems unlikely and I've always wondered what went wrong. I started to wonder if when I folded the canvas I didn't have the sides the same length. After thinking about it I changed my procedure a bit. Here's a few things I do now:

    1) DO NOT assume the ends of the canvas were cut at 90 degrees to the length. I now fold the canvas in half along where the keel would lie, line up the long sides together, then clamp both ends. This will cause both sides of the canvas to be the same length and thus stretch the same. But be careful not to cause a sharp crease when you fold otherwise you'll have trouble causing the crease to lie flat against the canoe when stretched.
    2) When you place the canoe in the folded canvas take pains to center the canoe as well as you can to the canvas. Again, you want both sides to be equal length so they stretch the same.
    3) I canvas with the canoe keel-side-down and the canvas tensioned with a come-along. I start with 40# weights at both ends of the canoe and just a little tension. I then use a canvas puller to get rid of side wrinkles. But I don't staple yet - I use clamps to hold the canvas in place.
    4) After that I place more weight at the ends to a total of 120# and increase the tension. The canvas should 'ring like a drum' when thrummed. I let it hang under tension for at least an hour.
    5) After it has hung for a bit I REDUCE THE TENSION a bit just enough so that I can pull the canvas at the tips and cause the canvas to lie flat to the canoe's sides in this area - on some canoes with nice compound curves at the tips you'll never get the canvas to lie against the canoe in this area if the tension is too tight.
    6) Then before I start tacking the canvas down I reduce the tension again. Add a few tacks/staples in the stem area right where the canvas stops conforming to the stem shape. This will help prevent the canvas from 'bouncing back' when the tension is removed.

    Anyway... just FYI I guess.
     
  5. OP
    OP
    NickD

    NickD Recreational Sander

    Thanks for the replies! MGC, I do put weights in the canoe as well as use braces from the ceiling to keep the canoe seated in the canvas. Howie, thanks for your canvasing steps. Going to have to look into that the next time around. I'm beginning to think this is a case of not the right tension on the canvas and filler that may have wanted to cure longer. Sun definitely played a part since as of today, the side that got the sun is much worse than the other side. Either way, a good learning experience for the future when I recanvas... In the mean time, since it had smoothed itself once, I'm going to wet the inside of the canoe/canvas to see if any swelling/shrinking will temporarily solve the problem again. Maybe I have a rainy day - humid loving canoe!

    Plus, glass half full, since I know I have a redue in the future, time to go see for myself how durable canvas/filler/paint really is!
     
  6. Canoe T

    Canoe T New Member

    After recent recanvas job I experienced the same type wrinkles on the side facing the sun. I had applied the filler only so will wait a few more months to cure before painting.
    The stretching process and nailing was properly executed. It was carried out in 50 degree weather and that may have been my downfall! Warmer weather would have allowed the canvas to stretch more and become more pliable. I used a pre-shrunk canvas that would have negated further stretching by applying very hot water and a filler that temp needs to be above 70 degrees before curing occurs! lessons learned!
     
  7. Dave Osborn

    Dave Osborn LIFE MEMBER

    I’ve recanvassed a couple hundred or more canoes and know others that canvas many canoes. I don’t, nor do I know anybody that washed the canvas down with hot water.
    I have had a couple issues similar to Nick’s several years ago. Both involved canvassing with high humidity. In both cases the canvas was filled but not trimmed and I was able to re-stretch it a bit to remove the slack.
    I canvas upside down on horses, using a come-a-long and a flat jawed vise grip. Lengthwise I think it stretches about an inch per foot. Seems like a lot, but I usually crank it about 16” when stretching a 16’ canoe.
     

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  8. MGC

    MGC Scrapmaker

    Soo...since this post I too have become an active participant in the pucker pity parade. I have no idea what caused the puckers but there is no fix for it other than a re-canvas. The hull was fine right up until right before I was getting ready to paint (filled, primed etc.). Suddenly there were slight puckers along the rails. Then I noticed puckering on each end. I pulled the canvas loose from the stems and tightened it up. It looked fine. I took the boat down into my cellar shop to work on it and immediately noticed the puckers were back and really no better than before my attempts to remove them. The canvas is nice and tight rail to rail and on the bottom....baffling.
     
    Last edited: Mar 9, 2021
  9. Rob Stevens

    Rob Stevens Wooden Canoes are in the Blood

    I wonder if canvas pucker results from degradation of the quality of canvas production?
    Of course, this is speculative. I have no evidence that canvas quality has fallen off.
     
  10. samb

    samb LOVES Wooden Canoes

    I don't know the answer to the original question about canvassing, but regarding the 'upside down' method, to get things tight I find you need quite a bit of vertical force. After pulling it as tight as I dare lengthwise, I grab the canvas in canvas pliers at each rib and lever off the inwhale to make sure the canvas is tight vertically. I reckon it's tight enough when I can see the detailed shape of the rib (including any chips along the top edge which I should have repaired).

    Sam
     
  11. Todd Bradshaw

    Todd Bradshaw Sailmaker

    I kind of think humidity held in the canvas at the time of canvasing might be a fairly important factor. The best canoe canvasers may live in places like Arizona and Nevada. :D
    Interesting test: This is a chunk cut from a roll of canoe canvas which I bought from Old Town many moons ago. It's been sitting amidst a pile of sailcloth rolls in my house in my dehumidified basement. From the chunk I cut a square 18" x 18". I dunked it in the sink to get it wet. It took some doing as it may have had some sort of treatment on it, but eventually it got wet. Since cotton yarns swell when damp or wet, tightening the weave and shrinking the fabric, you can see in the first photo here how much the piece shrank in a few minutes just from getting wet. The factory selvedge edge is at the left side. Bow and stern would be top and bottom as it comes off of the roll.

    Wet.jpg dried.jpg

    Next, I stuck the wet piece outside in the sun to see how much of that would come back as it dried and the fibers relaxed a bit. Some progress was made, though it did not come all the way back to its original size. It is, however, fairly stretchy on a bias once dry and most of the shrinkage can be pulled out if kept under tension. What this all hints at to me is that stretching canvas when the humidity (both in the air and in the canvas) is as low as possible is preferred. If you can get it stretched and tacked down when it's as dry as possible, then changes in humidity are far more likely to make it tighter than to loosen it up.
     
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  12. Rollin Thurlow

    Rollin Thurlow member since 1980

    I have canvased quite a few canoes myself and have have supervised quite a few students that canvas there own canoes. I've done it in hot weather, cold weather, high humidity and low. I've done it with a hot wood stone pumping out heat in the room and I've done it with fog rolling into the shop. I've encountered many problems of my own making and seen just as many problems that other have made. Maybe I haven't heard all the different stories of loose canvas but I've heard and seen enough that I'm convinced there is only one problem that is the cause for loose or wrinkled canvas and that is "not puling it tight enough, either from side to side or lengthwise."
    Almost any time I tell someone that is the problem, they will report that they pulled it oh so tight and they had done canoes before and never had this problem, they blame the filler, the weather, the fastenings and everything else, BUT after much discussion and they repull the canvas, with more due diligence, it solves the problem.
    Just pulling the canvas where it looks tight is not good enough, using a pair of artist canvas pliers that depends upon you own hand strength is not good enough, using just a few hundred lbs of weight in the canoe is not good enough. With a stronger grip, pulling the canvas that last 1/8" or even and extra 1/16" makes a huge difference. If your not afraid that your going to rip the canvas, and then pull a bit more, your not pulling enough!
    Popeye would of been a good canoe canvaser!
     

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  13. MGC

    MGC Scrapmaker

    Ouch, I've been outed. But it is as Rollin says, I know that is at the heart of the problems I had. This was the first hull I did that had really had turned back stems and my suspicion has been that is what kept me from getting things as tight as I should have. When I recanvas I'm going to need to figure put how to pull tighter than I did.
    I just had some spinach for dinner...hopefully that's the game changer.
     
  14. Dan Miller

    Dan Miller cranky canoeist Staff Member

    Spinach might help, but I expect you might also need Popeye's forearms and an anchor tattoo...
     
  15. MGC

    MGC Scrapmaker

    "Blow me down. That's all I can stands, 'cause I can't stands no more! I yam what I yam an' tha's all I yam"
     
  16. Howie

    Howie Wooden Canoe Maniac

    Hope you haven't jinxed me Mike. I just canvased an Otca yesterday in 68deg weather & mudded it today in 75deg, but we'll get as low as 17deg in the next week. If wrinkles appear you can be sure I'll be a blaming the temperature changes!
     
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  17. David Satter

    David Satter LOVES Wooden Canoes

    I use the right side up method like Rollin, I learned from Jerry. My shop is a barn, cold , hot, humid, every kind of weather. I pull it tight till my hands hurt or the canoe is going to break. Don't know if my hands and arms will be strong enough when I'm 85 , I'll probably still be working. If i have some loose canvas even after filler , It's usually nothing I can't fix by pulling it a little with pliers.
     
  18. Blott

    Blott LOVES Wooden Canoes

    When I did my Old Town I stretched the canvas using the tow hitches of two SUV's for anchor points but the wrong way up. I cranked it in with ratchets with everything creaking to the point that I thought the canvas may tear. I then pulled down from the centre with wide pliers rolling inwards to add tension before firing staples in. This was repeated each side along the whole length of the canoe.

    I couldn't hold my beer glass for the next 3 days as my hands and wrists ached so much. We will see how it stays as temperature in the garage where I store the canoes varies considerably over the seasons.
    EFCBB9EF-0556-4FD8-B397-BCB3B79646E7.jpeg
    F3B60C5E-CC3E-4FA9-B322-FF6D6174A22B_1_201_a.jpeg
    Nick
     
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  19. Howie

    Howie Wooden Canoe Maniac

    Ok.... so while we're on the subject of canvas stretching, let me ask a question about tension. This comes to mind now because just a few days ago I canvassed an Otca. The sides of the Otca's decks curve inward somewhat. This creates what I call a 'cheek' area, and it helps create the wonderful curves in the hull shape. But this area poses a canvassing problem: Pulling the canvas 'up' from the rails will cause the canvas to contact the side planking - which is what you want. But pulling the canvas taut from the stems will cause the canvas in this area to pull away from the side planking. So the question is: how tight do you want the canvas to be when you start tacking in the flaps at the stems?

    I certainly agree that the canvas needs to be pulled really tight (with the canoe suitably weighted). But obviously at some point you're going to cut the canoe free from the ends of the canvas - and there goes your tension. I'm thinking this may be one of the causes for wrinkle problems: Tacking the canvas sides in place under tension but removing that tension to tack the stems might seem confusing to the canvas and cause wrinkles!

    So here's what I do:
    * First I put 40# in both ends of the canoe and apply modest tension to the canvas just enough to cause it to lift off the ground. I believe that since the canoe isn't heavily weighted it's easier for canvas stretchers to pull the sides taut. Also I use large sized paper binder clips to clamp the canvas to the rails to allow the canvas to move a bit when I stretch the canvas later.
    * Then I add an additional 80# to each end (120# each end total - 3 bags solar salt and or cinder blocks) and I stretch the canvas until it's drum tight (it emits a high pitched 'thunk' when flicked with a finger). I use a 2-hinged-board V-shaped thingie to clamp the canvas sides together at the stems and let the canvas conform to the hull for several hours.
    * Then I use canvas stretchers to stretch the sides again and tack/staple the canvas in place. I do this until I get to the 'cheek' area where I can no longer pull the canvas 'up' and have it contact the hull.
    * I then reduce the stretching tension until the 'cheek' can be pulled upward to contact the sides, then I finish tacking the sides.
    * I then add 3 or 4 staples to temporarily staple the canvas to the outer sides of the stems so that the canvas remains under tension, then I cut the canoe free of the canvas ends.
    * Then starting at the deck area and working down I staple the flaps to the end of the stems, removing the staples from the sides of the stem as I reach them. This means I don't have to apply much tension with doing the flaps since the canvas is already under tension due to the temporary staples. And by doing so I find I don't have to muss with the staples/tacks on the sides to get or wrinkles that can pop up there after the stem area has been done.

    Anyway, that's what I do.
     
    Last edited: Mar 12, 2021
  20. Dave Wermuth

    Dave Wermuth Who hid my paddle?

    I leave about three feet at the rails unfastened and do the stems first. Then I finish the last three feet, pulling the canvas into the hollow. So far I've not had issues.
     

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