Building a flat bottomed canoe

[troy2000]

Interesting thread. I liked the circular saw scarfing jig, neat idea to take off the material from the bottom, it would solve the problem I had keeping 3 and 4 mm marine ply sheets flat, and much simpler than the jig I tried. Just in time for the next build I have planned!

I should mention that I have that jig screwed to the saw backwards. It would have made more sense to attach the saw to the narrow side and lay the wide side on the plywood, since both sides were run through a jointer to make them smooth and straight anyway. No big deal; it works either way.

The sheer planks look like they have straight, parallel edges: is that the case? Then the sheerline and rocker is determined by the flare angle and the plan curve. This is something I have tried and got good results with.

Yes, the planks are parallel-sided; 11 1/8" from end to end. I thought about tapering them an inch or so from stem to stern like a small sharpie, and decided I was getting carried away...

I read that ring nails are good for attaching the bottom ply to the sheer planks; you may want to try them.

Since those side planks are soft pine, and planed down to a hair less than 1/2" (1.25 cm), I'm a bit leery about nailing anything too aggressive into the edges of them--even with pre-drilling. I have some small hot-dip galvanized nails that will probably work just fine, particularly since the chine will be glued with PL Premium anyway. I'll also be gluing on a small outer chine log, to cover the plywood edge. That should add a little support also. If we start stomping the bottom out I'll dig up some epoxy, tape the outside and fillet the inside. Hopefully it won't be necessary.

Like most of the builders on the forum I am not a fan of Gorilla glue although I used it on my first effort; it worked OK for a dry docked boat but too expensive.

The cost of glue isn't really an issue for a boat this small and this simple. I bought a five-dollar bottle of Gorilla Glue, and I'll probably have half of it left when I'm done.

Also although it fills a gap, it does so by becoming a foam and expanding, which makes it much weaker, so for a strong joint it does require a fairly good joint fit. But too much pressure and it squeezes out, unlike thickened epoxy.

I hope I'm not calling the Gods down on me with my arrogance, but that's not a problem. I'm the son and grandson of carpenters and builders, and I've worked in wood all my life. My glue joints don't have gaps.

And if you have more than just the barest minimum of squeeze-out, you're using too much Gorilla Glue; it's nothing like epoxy. For proper strength, you want a close fit and a very thin layer of glue. And it needs firm clamping pressure for an hour or two. Otherwise, its tendency to foam and expand can actually push joints apart, creating the gaps it isn't good at filling....

Nothing seems to work really well on end grain, not even screws! Epoxy can be made to work however. I have tried warming the wood before applying the epoxy and letting it draw into the grain as the wood cools, adding more as required. A thick epoxy works best but not too thick, a balance has to be struck between having it all soak into the grain or not penetrating enough to match the strength of the wood. My theory is, the glue only has to penetrate about twice as deep as the average pore diameter, which is not very far at all.

You're right about end grain. I didn't really have much hope that the glue I was using between the frames would hold anything; for that I'd have needed half-lap joints instead of butt joints. But I soaked the glue in anyway before screwing the frames together, in the hopes that it would at least seal some water out of the joints. Of course, the real strength is mostly in the glued plywood gussets.

 

[troy2000]

Reality kept getting in the way again today; among other things we had to work on my son's car. We did get the frames shaped and permanently installed, though.

We laid a straight edge across the boat and marked the frame tops flush with the top of the planks, and used the mouth of a one-pint mason jar as a circle template pencil in the curves. Then we cut off the extra wood, and shaped the ends on a disc sander.

Since the planks will be expanding and shrinking, I didn't want them glued too rigidly to the oak frames. Instead we used three 1 5/8" coated deck screws to a side on each frame. We put a layer of Dap exterior caulk between the frames and the planks before sending the screws home, to seal out the weather. I forget the Dap number, but it's a sealant/adhesive that stays somewhat flexible, resists mold and mildew, and it's paintable. It also has to be cleaned up with paint thinner instead of water, though. Instead of trying to scrub up the squeeze-out, we just wiped it into the corners with a fingertip and smoothed it out.

When I get home next Tuesday, I'll see what the name and number of the stuff is.

The 3/8" plywood bottom was already scarphed together and roughed-out. For now we tacked it into place, and put some weights on it so the boat doesn't blow off the sawhorses again. Which reminds me: in broad daylight, the mouse damage didn't look as bad as it did the evening we noticed it. I don't think it merits putting in dutchmen; we'll just fill it with something.

I had to knock off early, so I could drive back to work. When we got ready to tack on the bottom, clean up the scrap and put tools away, Dwaine did what most redblooded teenage boys do when faced with cleanup work: he tried to escape.

Fortunately I spotted him before he made it over the horizon, and gave chase:

I came alongside and hailed him, but he refused to heave-to.

So I intercepted him, and prepared a boarding party...

The crew was successfully recaptured and pressed into service, leaving the vessel unmanned and adrift until it could be recovered.

 

[ancient kayaker]

Judging from the look of the landscape you haven't had a lot of rain lately. Are you going to be able to find enough water to float it in when the time comes? Or will you use the same solution as Dwaine?

The wood is likely about as dry and stable as it is likely to get right now, so the tendency will be to expand. Since - per your first post - you don't plan to leave the boat in the water and excessive rain does not appear to be a problem in your region :!: I doubt cracking will be a problem. You can always lash the sheer planks to the frames at the gunnels; this worked for the Vikings ...

I use marine ply for both sheer planks and bottoms so I don't have to worry about cracking, but 3 mm and 4 mm ply doesn't accept edge fasteners for the chine joint, so I use chine logs. For a small lightweight canoe the ply and the chine logs are so light and floppy that it hard to get a tight joint between them using the ply-on-frame building technique. instead, I glue the chine logs to the sheer planks flat, which allows me to use lots of clamps, and it stiffens the planks making them easier to handle. At a later stage the chine logs provide a place for the fasteners that hold the bottom on while the glue (epoxy) sets. I use staples for really light craft (15-22 lb) which I remove once the glue has set. I use screws for sailboats which I leave in for reinforcement to handle sailing stresses.

How much rocker does the canoe have? I am thinking about the turbulence that the bottom edge of the transom will create; if it is under the surface more than a fraction of an inch when the boat is loaded it will be a source of drag - and noise- been there, done that!

 

[troy2000]

Judging from the look of the landscape you haven't had a lot of rain lately. Are you going to be able to find enough water to float it in when the time comes? Or will you use the same solution as Dwaine?

The wood is likely about as dry and stable as it is likely to get right now, so the tendency will be to expand. Since - per your first post - you don't plan to leave the boat in the water and excessive rain does not appear to be a problem in your region :!: I doubt cracking will be a problem. You can always lash the sheer planks to the frames at the gunnels; this worked for the Vikings ...

I use marine ply for both sheer planks and bottoms so I don't have to worry about cracking, but 3 mm and 4 mm ply doesn't accept edge fasteners for the chine joint, so I use chine logs. For a small lightweight canoe the ply and the chine logs are so light and floppy that it hard to get a tight joint between them using the ply-on-frame building technique. instead, I glue the chine logs to the sheer planks flat, which allows me to use lots of clamps, and it stiffens the planks making them easier to handle. At a later stage the chine logs provide a place for the fasteners that hold the bottom on while the glue (epoxy) sets. I use staples for really light craft (15-22 lb) which I remove once the glue has set. I use screws for sailboats which I leave in for reinforcement to handle sailing stresses.

How much rocker does the canoe have? I am thinking about the turbulence that the bottom edge of the transom will create; if it is under the surface more than a fraction of an inch when the boat is loaded it will be a source of drag - and noise- been there, done that!

Well, last question first. I haven't really measured the rocker; your guess looking at the pictures is probably as good as mine. I'll get busy with a tape measure and provide all the particulars once the boat is done. But judging by those I've built in the past, the stem and transom both should be just about at the waterline with a normal load: i.e., two people daycruising, or one person plus a weekend's worth of camping and fishing gear.

Two people plus camping and fishing gear might put the transom under a bit. On the other hand, we'll have two paddles instead of one to move it....I doubt the drag will even be noticeable.

The last flat-bottomed canoe I built was a quick-and-dirty job. I built it so I could use it for fishing while I was working on a housing tract up in the Sacramento Delta. All the wood was salvaged from dumpsters. I pre-shaped the sides of 3/8" ply, and clench-nailed outer gunwales and inner chine logs of 1 x 2 (3/4" x 1 1/2") Douglas fir. I bent them to the stem and transom, around a single midships mold of 3/4" ply. Then I cut the center mold down to a one-piece frame at 1 1/2".

It was originally intended as a double-ender. but after I nailed the sides to the forward stem and started bending them around the center mold, it became obvious that something was going to give if I insisted on a stem at the other end too. So I put a transom in, instead.

I'm not worried about cracking the sides on this one, since I'm starting with dry wood to begin with and don't expect any measurable shrinking. But I am worried about the pine sides expanding in wet weather. If the frames were a softer wood, they would probably just bend and allow the side planks to cup. But they're oak. I guarantee that if I glued pine planks to those oak frames, they would break any solid glue joints as they expanded and contracted. That's why I used the caulk, instead. It has pretty good adhesive properties, but it's also flexible.

Southern California is pretty dry. But that means it needs reservoirs, to provide water for a burgeoning population. Lake Hemet, Perris Lake and the new Diamond Valley Reservoir are all within easy reach for my son--along with Lake Elsinore, which is a natural lake.

And I work beside the lower Colorado River. It has miles of backwaters and lagoons, which this canoe should be perfect for.

 

[hoytedow]

It looks like the scuppers are a bit large. Seriously looks like it will be a great little boat though.

 

[ancient kayaker]

Aw kumon Hoyte, you never seen a self-draining cockpit before?

 

[hoytedow]

He could always hang it from suspenders and call it a land yacht.

 

[troy2000]

I just found a 14 minute film titled "The Pirogue Maker." It shows the making of an old-fashioned dugout pirogue in 1949--one that wound up light enough for a guy to tuck under his arm and carry down to the water.

Very impressive. They went after the wood with saws, axes, adzes, a broadaxe, planes, spokeshaves, draw knives, scrapers and any other edged tools you can think of. I don't remember seeing a jack knife, but I wouldn't be surprised if they used one of those, too.

Here's the link. It isn't narrated, but doesn't really need to be; the soundtrack is a gal singing some very pretty traditional folk songs. It was filmed the year I was born, by the way. Talk about making a guy feel old....

http://www.folkstreams.net/film,188

 

[ancient kayaker]

Remarkable workmanship, surely that's as good as it gets for that style of boat. I had forgotten that the word "Pirogue" once described a dugout, as these days it is generally used to describe a larger, flat-bottomed canoe build from planks or plywood.

The sophisticated shape of the boat with its hollow entry reminded me of the lovely lines of canoes made in the Peterborough area of Ontario, Canada, and builders like J. Henry Rushton of New York at the end of the 19th century. A book I have describes the evolution of the modern canoe from the dugout: it tells of how the earliest board-built canoes were made using a dugout as a building form.

 

[troy2000]

Remarkable workmanship, surely that's as good as it gets for that style of boat. I had forgotten that the word "Pirogue" once described a dugout, as these days it is generally used to describe a larger, flat-bottomed canoe build from planks or plywood.

The sophisticated shape of the boat with its hollow entry reminded me of the lovely lines of canoes made in the Peterborough area of Ontario, Canada, and builders like J. Henry Rushton of New York at the end of the 19th century. A book I have describes the evolution of the modern canoe from the dugout: it tells of how the earliest board-built canoes were made using a dugout as a building form.

I agree that it was a very sophisticated hull for a 'primitive' dugout; the old boy definitely knew what he was doing. Of course, it also occurred to me while watching the film that if the tree they felled had been ripped into planks, it would've made a dozen pirogues.

I think the pirogue in the film was kind of at the pivot point of technology. There was no sawmill handy to cut the log into planks, and they used no portable power tools. But they were definitely equipped with high quality, mass-produced hand tools.

I've been googling pirogues, and I found that quite practical, mass-produced ones in fiberglass or aluminum are surprisingly affordable. I'm the sort who'd rather build and own a wooden one anyway, but I have to admit that any savings are contingent on my labor being free.

Don't get me wrong; that's OK. I enjoy woodworking for its own sake. And it's time that otherwise would be spent being a couch potato, playing video games, arguing with the old lady, or whatever.

 

[ancient kayaker]

Yes, it was a bit wasteful, more so considering that it didn't employ the trick used for large dugouts, of carving the hull narrower and using hot water to widen it by around 50%. If you wished to build a pirogue using ply, you can buy the plans and frames already made; kind of halfway home-made I guess. Personally, the design process is part of the excitement, my first few canoes were built simply to find out what different hull shapes did to the their qualities in the water. I'm not much for book learning ...

 

[troy2000]

OK. I never made it home Tuesday morning. I stopped by the compressor station to grab my laundry and toilet kit out of the locker room, and got snagged to work a 12-hour overtime shift. So I got home Wednesday morning instead, and we started on the canoe. Miserably hot and sticky weather, but we got something done anyway.

We started by flipping the boat upside down and planing the side planks flat to take the bottom plywood. I used an old 9" Dunlap smooth plane--which would be a #4, I think. It's shorter than a jack plane, anyway... I suppose I could have used a power planer, but a hand plane gives a better feel--and an unexpected bobble isn't a disaster.

Then we did the frames across, to trim the plywood gussets flat and bevel the floor frames. I switched to a block plane for the edges of the gussets, then finished the frames with the smooth plane again.

We had left the bottom rough-cut and tacked onto the boat last week. So I ran a pencil around it and detached it, then cut to the line with a Skilsaw. Of course I set the blade just barely deep enough to cut, so it wouldn't bind on the curves. No pictures; the kid was off doing his weekly PT with the Army recruiter. I had it tacked back into position by the time he got back and showered. Then we marked the plywood to match the outside of the planks, using a notched stick and a pencil.

After that I cut the thickness of the planks off the lower half of the notched stick, and ran a mark that lined up with the inside of the planks. The inner and outer lines made it a little easier to find wood when we started nailing (and the outer line gave us something to aim for while beveling the edge later). Finally, we marked every 2" for the nails.

There aren't any pictures of the actual gluing; we were both too busy to grab a camera--with the temperature up over a 100 degrees (Fahrenheit), even the PL Premium we used wanted to go off in a hurry.

We spread a good thick layer of the PL all the way around on the planks and the frame bottoms, except for a gap in the middle of the boat where we laid a 2 x 4 board. The board was to hold the center of the bottom off the glue, while we positioned the ends by using the old nail holes where we had tacked them. After I started a nail at the bow and Dwaine had the stern lined up, I pulled the 2 x 4 and smeared glue where it had been. Then he dropped the plywood into place and drove his tack home, and I started nailing like a madman.

It didn't help that I was using a cheap hammer with a cheesy rubber grip, instead of a decent wood handled finish hammer.

After the nailing was done (almost a pound of the little buggers) and the PL squeeze-out was getting rubbery, we turned the boat right-up. I took my folding knife and sliced the PL loose from the wood on the inside. But instead of making a mess by trying to gather it, we just let it set there overnight until it was cured. End of day one this week......

 

[troy2000]

Day two of this week: we cleaned up the squeeze-out from gluing the plywood bottom on. We also knocked out and replaced a few nails that had missed their mark enough for the ends to come out the side of the plank.

I used a 4" side wheel grinder with a rubber sanding disc and a piece of 40 grit paper to rough-shape the bevel on the chines. Like cutting to the lines with a Skilsaw, it takes a little skill and experience but saves a lot of time.

Then we finished the job with block planes, and cleaned it up with sanding blocks. We left a crisp edge, because the edge will be covered with a thin strip of wood to protect the plywood.

Next we cut a strip of oak for the outer stem, temporarily screwed it into place, and cut it off with a flush-cut handsaw. I scribed the lines for the leading edges, and used the side wheel grinder again to get the rough shape. A couple of minutes with the smooth plane finished that out. We put plenty of PL Premium on it, and screwed it into place.

We came in to cool off; we were dripping wet even when we weren't moving around. I checked weather.com, and it said it was 104 degrees (40 degrees Celsius), with a chance of rain. Sure enough, the clouds that had been hanging at the edge of the hills around us suddenly slammed shut, the wind picked up, and we ran to get the boat and tools under cover.

We finished just as the first drops were hitting the ground, and got treated to some pretty spectacular thunder and lightning. Not much rain, but it definitely put an end to our work day.

 

[lewisboats]

Everything excellent except...for shame!!!...no guard on that grinder! 13000 rpm that rubber or even the sanding paper makes like a bullet. DON'T ask me how I know...I just DO!

 

[troy2000]

Everything excellent except...for shame!!!...no guard on that grinder! 13000 rpm that rubber or even the sanding paper makes like a bullet. DON'T ask me how I know...I just DO!

I'm a big fan of guards on power tools, but in this case it isn't practical.

I use the guard anytime I'm grinding or cutting. But on a rubber sanding disc, the paper curls back over the disc to begin with. When I add some sanding pressure the disc curls too, and the paper starts cutting into the guard and shredding itself. Not to mention the guard itself getting in the way, when I'm free-handing like that.