Plywood Canoe Concept - Birchbark Style

[MN Dave]

I understand how the darts work. It’s pretty obvious to anyone who h as ever tried to compound bend plywood.
My idea comes from sailmaking. Assume you want to tighten the leech, you could open the seams and increase the overlap. Akin to taking the gore cuts. The alternative is to split the seam in the middle and stitch it back together with less overlap. Letting the middle out rather than pulling the edges in. Some sailmakers have done shocking things with knives and sail repair tape on the way to the starting line.
I was thinking that the slots would end up being 6” or so every foot. They wouldn’t have to cross the centerline, just provide enough relief for the center of the panels to stretch enough to prevent the edges from buckling.
It should come to the same thing.
I have built more than a few tortured ply boats, I didn’t mean any offense.
SHC

Offense? I was just trying to explain why I thought it wouldn't work. I had no way of knowing that you had built any of these. I wasn't offended until I found out that you have made more than a few tortured plywood boats and I haven't seen any pictures. Yer holdin' out on us!

If you look at the picture in Link to Post #95,, you can see what the panels do when wrapped around forms with no cuts. It looks to me like there is either too much wood at the sheer or too little all across the middle. Stefan explained somewhere how he modeled the canoes on his computer then laid the surface flat to locate the cuts. He explained it a lot better than I can.

[flo-mo]

Another addition to the Gorewood design family: The Fat Gorwood Canoe


Actually this is a refined version of one of the very early stages of the design development which at the time I didn't further engage in as its midship section was too wide and too deep for my liking (scale model in the bottom right corner).



Recently I was searching for a design of mine that would have similar characteristics as Storer's Viola 14 sailing canoe. The closest one I found was this early stage design. It is more stable than most common canoes, but not quite as stable as the Viola 14.
So eventually I ended up developing a completely different sailing canoe (Flywood Two Sheet Sailing Canoe).


Still for some people this fat canoe might be what they are looking for. If you don't care much for speed but want a canoe that could also be sailed without being too tipsy and offers more capacity and more freeboard, this one might be an option.

LAO: 478 cm
Beam: 95 cm
Midship Depth: 40 cm




Comparison Flywood Two Sheet Sailing Canoe and the Fat Gorewood Canoe:



Offsets for the Fat Gorewood Canoe (click image for PDF download):

[Thestripper]

It's good to see that you are developing new Gorewoods! I like the concept idea of the Fat G and that it could serve as a good sailing canoe. Do you have some section drawings showing the approximate rocker and cross section hull shape? As always, impressive work flo-mo!

[flo-mo]

Hi Johan,

Here is a picture that somewhat gives an idea of the rocker and the cross section amidships. As it is derived from the small scale model made of paper it is really just an approximation.

To a degree the rocker can be regulated by the distance at the sheer, especially with this building method. When you start the "metamorphosis" you have excessive rocker. The further the two shears come together, the more the hull stretches out. So more flare means more rocker -- if you introduce more tumblehome you will reduce rocker.

Depending on the designated use of your canoe it is up to you to decide which shape you prefer.

[flo-mo]

Just a minor correction on the dimensions of the Fat Gorewood Canoe:

LAO: 477 cm
Beam: 95 cm
Midship depth: 39 cm

The measurements are taken from the small paper scale model and therefor not really accurate. Also the change is almost insignificant, but still I try to get the numbers right. This is why I also updated the plan for the offsets. I rearranged the layout, but aside of correcting LAO and depth by one centimeter respectively everything else is the same.

Here is the updated plan (again click the image for PDF download):

[amish rob]

I’m holding out for that sailing canoe. My duck punt is lonely.

[flo-mo]

Peter R has used the English lockdown to design and build his own Gorewood canoe.




It is based on the very first Gorewood canoe that I built, the Gorewood 14, but has a shear 3 cm higher. The exceptional craftsmanship he demonstrated in building his canoe and the ingenuity he showed in solving tricky problems are remarkable. In addition, Peter has excellently documented the entire construction process in pictures, words and video recordings.




If you are interested in this special construction method, I recommend you to have a look at his blog in the Song of the Paddle Forum: https://www.songofthepaddle.co.uk/fl...re-t58748.html
You will hardly find a better building instruction.


p.s.: I envy Peter for being able to use exactly the plywood I always wished I had used to build my canoes.

[Nathanael]

such a nice build to watch.

[Lee.007]

How the heck does Peter keep his shop so freaking clean while he is working? Are there little elves that come out between video frames to sweep up?

That was a nice video. Lots for a beginner like me to learn from it. I like how he has all of his tools and clamps laid out on the very large work table before he starts needing them. I also like his method of bending the gunwales into shape with the zip straps. Was he using a steam iron only? I thought I saw him painting something in the hull while he was bending and steaming?

[Woxbox]

How the heck does Peter keep his shop so freaking clean while he is working? Are there little elves that come out between video frames to sweep up?

Right. Shops like that drive me nuts. He's built a lot of boats, but the floor is immaculate.

[flo-mo]

Since the shape of the canoes I have made using the Gorewood construction method is influenced by a variety of factors (cutting pattern for the panels; thickness and type of plywood; wood type, thickness and grain pattern of the wood veneer of the plywood, or generally speaking, the bending behavior of the plywood), it is very likely that each canoe is unique and can hardly be replicated a second time in exactly the same shape.

Nevertheless, it is of course interesting to get an idea of how the Gorewood canoes actually built look and what the significant characteristics are.

In order to present this in a comprehensible way, it has always been my intention to take the lines off the hulls of these canoes and subsequently create 3D models that provide the basis for hydrostatic calculations.

However, this process is quite time-consuming and for the longest time I lacked the motivation to deal with it. Only when I realized what amazing possibilities photogrammetry offers even to the interested layman, I decided to document my 4 canoes with the help of this technology.

More info on photogrammetry: http://forum.woodenboat.com/showthre...photogrammetry

Here are the results:

[Thestripper]

It's been a while since I posted here last time. Since that time, many beautiful Gorewood style canoes have seen the light of day. There has also been some less successful, but equally faithful attempts at the build. Even the attempts that came to a cracking halt seem to have brought some joy to the builder. That's how it was for me. It was a thrill! Things are in high tension and you don't know if this is going to work...

I used two sheets of three-ply popplar plywood. I think it measured 3.7 mm thick, under 4 anyway. At the hardware store I took the top most sheet in the stack. After a quick inspection I was impressed and put it aside. Then I went through the whole bunch, maybe 35 sheets of plywood but there wasn't another good sheet. Looked like they either had some poorly laid out core layers, or the face layer had some tiny but long cracks. There were even some with eyes almost 2" big. I Picked out the one I thought was best. It had good flat core land face layers, no really big eyes but some some thin short cracks. It turned out the first plywood, the nice one, stood up to the test. The other one didn't.

I used five days to slowly close up the canoe. I went real slow towards the end. Almost inaudible sounds caught my attention on the fifth night. I had added a little tension to the straps earlier that night. I just stood there trying to hear where the tiny and sporadic sound came from. Just as I thought I had localized the sound as coming from the bow area a loud and sharp crack shook the room. My eyes were on the gunwale when it happened and I just picked up that something indeed moved quite a bit. It turned out that the hull had cracked in two places at the same time. These were totalt cracks through all the ply-layers. Below the bilge near the keel, about one foot from the bow and stern. Each crack about 1.5 foot long or so and they were both on what I had previously judged to be the bad sheet. I let it rest for a few days and then closed up the hull without any more bad cracks happening.

The tension released by the two cracks had caused the hull to bend. Midships the shape looked quite intact but the bow and stern looked like great fishtails pointing in opposite directions. The panels wanted to flip inwards creating a convex area on the front right, and back left ends of the canoe. I stuck a piece of wood inside the bow and stern to visually fix this as I contemplated the over all shape of the canoe over a few days. The hull came so close that even though I didn't want to spend glass and epoxy on it, gave me confidence that this method will work. I was thinking that revising something in the plans or using hot steam or such would do the trick. It has later been established that the right plywood will accept becoming a beautiful Gorewood canoe. Anyways, I hope you will enjoy this little flash from the past.

Thanks to flo-mo!

[Abmy]

Brilliant last photo - a glorious ending to what sounds like a valiant effort. I am about to start a 14 footer using slo-mo’s plans. I’ve built several cedar strip canoes and skin on frame kayaks, but have no experience with plywood construction. The most promising locally available plywood I can find is 3mm Baltic birch. A little heavy, and will require an extra scarf to get the sheet length I need, but it is very sound and strong, and seems pretty flexible along it’s length. Anyone had any success with Baltic Birch? Is it worth a shot or is it doomed to failure from the start? Just trying to figure out if I have a fighting chance with this wood. Of course I will be checking my local backyard fire regulations regardless, ‘cause I guess you never know. Thanks all.

[Thestripper]

Brilliant last photo - a glorious ending to what sounds like a valiant effort. I am about to start a 14 footer using slo-mo’s plans. I’ve built several cedar strip canoes and skin on frame kayaks, but have no experience with plywood construction. The most promising locally available plywood I can find is 3mm Baltic birch. A little heavy, and will require an extra scarf to get the sheet length I need, but it is very sound and strong, and seems pretty flexible along it’s length. Anyone had any success with Baltic Birch? Is it worth a shot or is it doomed to failure from the start? Just trying to figure out if I have a fighting chance with this wood. Of course I will be checking my local backyard fire regulations regardless, ‘cause I guess you never know. Thanks all.

I think birch plywood could work. They are usually of good quality but I would pay attention to how the layers are laid out, how many layers and in what direction they run. What works best is, I think, somewhat of a guesswork but reading up on what people have used will probably give you a good int. As you say, birch is a little heavier than most other woods but since it's so thin you will not end up with a heavy boat, especially since you are building the 14' version. I would advice against the extra scarf joint though. It will have different flex characteristics in the scarf area. Take a drive or phone another hardware store and check if you can get full length sheets. Poplar 3.6 mm has served some successful builds. I think Flo-mo did an extra scarf joint on one of his canoes and made it work, but he is Flo-mo.

It's always good to know what the canoe burning regulations in your area are just in case.

Good luck.

[flo-mo]

Brilliant last photo - a glorious ending to what sounds like a valiant effort. I am about to start a 14 footer using slo-mo’s plans. I’ve built several cedar strip canoes and skin on frame kayaks, but have no experience with plywood construction. The most promising locally available plywood I can find is 3mm Baltic birch. A little heavy, and will require an extra scarf to get the sheet length I need, but it is very sound and strong, and seems pretty flexible along it’s length. Anyone had any success with Baltic Birch? Is it worth a shot or is it doomed to failure from the start? Just trying to figure out if I have a fighting chance with this wood. Of course I will be checking my local backyard fire regulations regardless, ‘cause I guess you never know. Thanks all.

Considering the time that passes before I reply, slo-mo would probably be a more appropriate name.

I must apologize in particular to Johan AKA "The Stripper" for once again responding so late. Thank you Johan for sharing the story of your unfortunately failed project here on the forum. At least it ended in a spectacular final act.


Now to Abmy's questions.

If the extra weight of birch plywood is not an issue, it is not a bad choice. It sounds like in your region the 3 mm Baltic birch plywood is only available in square sheets (about 150 x150 cm), which in any case requires two scarf joints. However, apart from the additional effort, this should not be a problem as long as the scarf joint is not in the area of the gores.
With three-ply plywood, all plies should have the same thickness. In no case should the outer layers be thinner than the middle layer. As long as this is ensured, the chances of success in the build are quite high. If in doubt, it is advisable to thoroughly soak the plywood before bending.


You have probably already looked at the blog from the excellent build of Peter's Flyply: https://www.songofthepaddle.co.uk/fl...re-t58748.html
This also started a lively discussion about the construction method in general in this forum: https://www.songofthepaddle.co.uk/go...16-t53911.html

It will be helpful if you look at this blog and ask any questions there, as there are several people (including me) with experience on the subject. I have also posted offsets for a 14 foot Gorewood canoe with 3 cm more freeboard, which may be of interest to you.

Cheers, Stefan

[Abmy]

Thestripper, Stefan - thanks for this. I will move ahead with the Baltic Birch - it is indeed three equal plies thickness, and 150 cm on all four sides. Finished cutting the two scarfs this morning and it is now epoxied up and drying on my basement floor. I sketched out on paper where the gores fall and it looks like they will avoid the scarfs. I will soak the plywood before bending, following Peter’s approach in his blog, to get maybe a little extra security.

I was very tempted by your 14 FB design Flo mo, but I am building this in my basement as a winter project and the only way to get the finished boat out in the spring will be through a window which is just over 18 inches (46 cm) high. This is not quite enough for the bow height on the 14 FB, but the original 14 canoe should work with a small cushion for error. A quick question though - if I wanted to lengthen the canoe a small bit without changing the sheer, say 10 cm or so, could this be accomplished by just proportionately extending the length to the bow and stern ends after the gores, without the need to recalculate their positions, or add new ones? Not sure if this would unduly complicate the bending into final shape…

thanks again for your advice on the Baltic Birch, and I will check out the songofthepaddle site for more information.

[flo-mo]

I understand your concerns about not being able to get the finished canoe out of the basement through the window, so I don't want to talk you into anything you might regret.

Purely in terms of dimensions, the Gorewood 14 FB+, which measures about 38 cm at its highest point, should also fit through the window opening, which I have tried to illustrate in this sketch showing both canoes in profile.







In case you decide to build the canoe with the larger freeboard, I have already redesigned the plans for a 10 cm longer canoe.

For PDF-download of the plans click at the image.

[John Gearing]

Back in the mid-90's I bought some plans for a tortured ply solo (double paddle) "Swamp Yankee" canoe that takes a different approach. Instead of copying birchbark, you end up with two 12 foot pieces that have integral "planks" cut into them (1 per piece). When you cinch the edges together you get a single-chine hull. I modified the plans a bit to suit my taste, taking the bow and stern profiles from Walt Simmons' and Pete Cullers' lapstrake canoes, and decided to borrow the idea of keeping the sheet (2mm doorskin in my case) intact down the centerline. This gave me a bottom much like a traditional canoe (yes, there were small humps at the point of the vees where you pulled the sheet edges together to form the forward and after ends of the hull) but it worked well. I also built one the "standard" Swamp Yankee way, which gives you a Vee hull. Each boat had exactly two metal fastenings: to secure the thwart in addition to the epoxy, and each was completely coated with epoxy. Glass tape on the seams inside and out, with epoxy putty in the joints. I meant it to be a quick and dirty build, and it was. No sanding, simple hand tools, hardware store paint following Culler's color suggestions. The flat bottom rode higher in the water, but I feel like the V has good stability and tracks very well. The whale boat bow rides up and over big powerboat wakes on my home waters (a river) with aplomb. This might scale up to a bigger size, if you use thicker ply, and might entail scarfing some extra with unless you got 5-foot wide sheets. Don't know if the guy behind Swamp Yankee is still around or in biz, but found this article on the Duckworks website. It shows the build better than my words can do. https://www.duckworksmagazine.com/01...nkee/index.htm

[Abmy]

Flo mo, all of this is greatly appreciated. It looks like I misinterpreted the bow/stern height specs for the 14 FB+. Based on your illustration it seems it will indeed fit through my basement window. And the inclusion of a tweaked set of plans tailored to the Baltic Birch panels, and with the extra length, is very generous of you - many thanks. This is the build I will do, starting tomorrow now that my scarf joints have cured sufficiently. Once again, many thanks.

John, that is a very neat build that looks like will get you out and on the water quickly. I like your description of the variations you have done with the hull. Good information and links.

All the best

[flo-mo]

PDF of the offsets for Abmy: https://drive.google.com/file/d/15d1...ew?usp=sharing


PDF bow/stern curve: https://drive.google.com/file/d/1fTu...ew?usp=sharing


PDF gauge for the width of the gores: https://drive.google.com/file/d/1dg7...ew?usp=sharing