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Tortured Ply canoe

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I've seen that build before on the Youtube.

A very interesting build with beautiful results.
 
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Yeah, I came across this link a while ago and it does seem to result in a very nice canoe, although at the time I didn’t really give it much thought. But now, given the way this pandemic is going I‘m in need yet again of a dust-free, generally low-mess project to do in my basement over the winter (it’s now too cold to work on my latest strip build or anything else in the garage, so otherwise the only highlights in my immediate future will be things like steam-cleaning tile grout lines, painting baseboards, and other “useful” things inside the house, all totally uninspiring).

I already have 2 skin on frame kayaks, built in the lock-down winters of 2020 and 2021, respectively, so that’s out. I also have a few paddle builds to work on but those move along pretty quickly, and I don’t really need that many more paddles. So I am going to give this canoe a shot, if only as an interesting experiment - bought the plywood yesterday and will start setting things up today.

If it turns out ok I will post some stuff on it. If it becomes a hot mess (like so many of my “great ideas”), I will probably never speak of it again 😁
 
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I would be interested in seeing how it goes regardless. I picture that hull imploding if I gave it a whirl.

Bob
 
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If it turns out ok I will post some stuff on it. If it becomes a hot mess (like so many of my “great ideas”), I will probably never speak of it again 😁
Hope this experiment turns out well cause I would really like to see some photos.
 
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Very interesting. I haven't heard of that method of construction. Build a canoe from sheet goods! I'd follow along with interest.
 

Glenn MacGrady

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If it turns out ok I will post some stuff on it. If it becomes a hot mess (like so many of my “great ideas”), I will probably never speak of it again

Good for you and good luck. Buuuuuut . . . c'mon, us canoe pervs would all like to see a hot mess as well as a great idea.
 
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Hot messes often have more entertainment value. Too many on the internet are "all that & a bag of chips"... I like real world, "wow, I screwed the pooch on that one, wonder if I can save it" kind of deals.
 
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There is more information here:

 
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Mike, it was a posting oops - accidentally hit “post” instead of saving a draft and since I couldn’t figure out how to delete it so I just edited it down.

Ok, so on this build - Glenn and Gamma1214 and others make a good point, and I do like me some shadenfreude as much as the next guy. So here we go with some details to date. Not a hot mess yet, but I came close a couple of times and the most risky part is still ahead.

I have tried to take relevant photos as I go. There are several more detailed, better-written and better-photographed tours of this type of construction already available, including through the link noted at the beginning of the thread. I used plans from Flo-mo, who has a website (http://flo-mo.weebly.com/), and he also led-off a number of detailed threads on woodenboat.com and songofthepaddle.com (there are 3 or 4 build threads by other people on that site, plus a few standalone blogs here and there). Flo-mo’s plans are posted free of charge. This build is a slightly modified version of one of his 14 foot solos (14 FB+) in order to lengthen it by 6 inches or so (he did the tweaking of his original plan for me after I asked how I could go about lengthening it - great guy).

I started with 3 sheets of 3 mm (1/8 inch) thick Baltic Birch. Probably the best material would have been a couple of 4x8 sheets of 3 mm Okoume marine plywood, but that was not available to me locally. Baltic Birch is very strong and well-made but it is not a marine plywood, and is susceptible to water damage and delamination if left wet for an extended period of time - if it comes out ok this boat will be fully fibreglassed and inside-stored so that won’t be an issue.

The Baltic Birch comes in 5x5 sheets, so the first job was to trim them down to 4 foot widths, which I did on my garage floor.

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Next I had to scarf the 3 sheets at a 12-1 ratio to make a single 4x15 sheet. While scarfing chunky pieces of wood for gunnels etc is not that difficult, cutting a 12-1 scarf across a four foot span of 1/8 thick material was a bit of a challenge for me, and not a good time in a freezing cold garage. I tried a variety of approaches, including building a circular saw jig, all of which either took way too much elbow grease with my limited hand tools or just obliterated the thin plywood layers. After almost 2 days of experimenting with scrap pieces (and confirming that insanity really does involve doing the same thing over and over but somehow expecting a different result) I was seriously thinking about declaring a hot mess without even getting to first base. But after some more fiddling and tool sharpening I was eventually able to pull off acceptable scarfs with a combination of careful power planing, some hand planing with a small apron plane, and 40 grit sandpaper. The photo shows two sheets of the 3 layered plywood, one on top of and set back from the other.

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Next came the glue-up of the three pieces of plywood on my basement floor, which went ok I think, but far from perfect. I am nervous about whether the scarfs will take the bending that’s ahead.

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Next came the markup of the 4x15 sheet to prep for cut-out. Seemed to go fine, and then I remembered I had a laser level and decided to double-check things with it before beginning the cuts. This revealed that marking the centre line relative to the edge of inexpertly scarfed plywood sheets was not a smart move - one sheet was slightly out of line and resulted in quite a bit of variation from centre once the laser reached the far end. Flipped it over, redrew the lines following the laser level and it came out much better - hot mess avoided (barely).

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The canoe is fully symmetrical, so the layout is the same across each of the four quadrants once the lengthwise and cross center lines are accurately marked out. To save time and ensure symmetry all round I used the plan offsets to make a quarter hull template to mark out the cut lines, and simply flipped it around for each quarter and the gore (dart) end points as I went.

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Cutting the lines and gores was pretty straightforward. Bought a new fret saw to reach the cut lines from the plywood edge, but for most of it I found a small razor saw followed by sanding to the line worked better (but I added to my tool collection - bonus!!!). I used cheap utility knives and a straightedge to cut the 20 gores - even thin and floppy 3 mm birch plywood is pretty tough, and after running through 3 utility knives my wrist and hand are still aching.

Just FYI for weight weenies like me, before scarfing I weighed the three 4x5 sheets and they came to about 23 pounds total. All the material cut off to this stage came to 5 pounds, leaving around 18 pounds for the wooden core of this canoe. That is about the same as the wood-only weight for a strip build using 3/16 cedar, for a boat the same size (about 47 square feet of surface area)

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The next step is closing the gores. I put together a simple mechanism of clamps to draw them together at the edges, and then went though a half day of trying to glue them closed with cyanoacrylate glue as some other builders of this boat have used (Starbond brand, but as far as I know it is the same as Krazy glue). This was frustrating, as the glue is very brittle and the pressure from releasing the clamps once dry just popped the joint almost every time. Eventually I gave up on the glue and just drilled some tiny holes and lashed the gore ends together using waxed sinew left over from my SOF builds. Hard to get the ones near the center completely closed, but they are very very close, strongly held together, and the sinew gives enough flex to avoid distorting the joint once the clamps are removed (whereas the glue just locked them into a sharp-angled position, when it actually stuck at all). I will cut out the sinew once the inwale is attached to support the edges and gores, and fill any remaining gaps with thickened epoxy once the plywood is bent into shape.

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Once all the gores were closed I got this weirdly cupped, free-standing banana shape as a result of the tension along the outside of the sheet.

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That is where it sits as of today. I just finished cutting and scarfing some 7/16 x 3/4 inwales out of cherry, and will epoxy them in tomorrow. After that I will be bending the sheet lengthwise into its final shape (with about a 40 percent chance of some level of wood splitting disaster if I am not careful, as far as I can tell from reading the limited number of other build threads I can find). Oh the suspense!!!
 

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That is awesome! I was hoping you'd attempt this and post it!

I am very intrigued by this whole project and (regardless of your results) I am planning to try it as well. (In fairness, I'll also post a thread when that process begins).
 
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Oh man this looks like a hot mess in the making! Especially if I were attempting it!
 
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I've seen this method before, but only just now studied it in detail...I like it!!

But, I don't think I would use plywood.
Maybe some other, low density sheet good, hmmm
 
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It seems very doable on the face of it, but I have no experience working with divinycell so don’t really have a feel for how it would react to all the bending and twisting involved. I imagine 1/8 or 1/4 divinycell has a fair bit of flex, and heat would give it more I assume. I know Corecell goes floppy as a noodle in a steamer, as I made a keyhole kayak coaming from it last year, so maybe hot water/steam is something to explore if you need to get it to bend beyond its “natural” limits.
 
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I've been toying with some left over 1/8" H80 on and off for a while.
I have been mildly successful wrapping half way around a tennis ball...that's a pretty severe compound curve, but it took much heat from a heat gun. I tried quartz lamps, not so good. Full immersion in a hot fluid would work well. Maybe steam too.
The challenge is that the foam has so little thermal mass and poor thermal conductivity, it's difficult to soak the heat into large pieces without spending lots of money.

After seeing the way that the 3mm plywood produces such smooth results, I'm pretty sure the Divinycell would do just fine for most of a hull, with heat forming needed for only the areas near the stem/keel interface.
Divinycell is surprising malleable and forgiving...up to a point...then--SNAP! Brittle failure, no warning.
 
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