Float My Boat
October 10, 2019 8:53 AM   Subscribe

The little boat I've made tips me out; how do I make a boat that doesn't? I want to be

I made a little boat, a skin-on-frame canoe. It floats nicely when empty, but when I get in it tips me out. I want to make another boat that's more stable with me in it.

I wanted a small, light boat. Its plan was taken from an American Indian canoe: it's about 9 feet long, and weighs 14 lbs; that fits my needs which are to fit inside my VW camper and to be light enough for me to lug to likely lakes and creeks. My daughter can use and paddle it but I'm either too top-heavy or have very poor balance.

From my ignorance the cross-section of the boat changed during the build, becoming more circular than it should be I think. I can fix that for the next build, but I'm asking for help in deciding just what the cross section should be. I imagine a rectangular box as being a lot less tippy than a barrel shape, but how do I find or calculate the "best" shape?

Background: Some photos of the build. I had zero experience so I winged the build after reading various online articles. I think my basic mistake was making the ribs (steam-bent oak) then putting the stringers (ash) on. That allowed the ribs to change shape, making the cross section more circular than rectangular. If I'd put stringers on the forms first and attached them at the stem and stern then fitted the ribs the shape would probably have stayed as planned; if I can't find any guidance for making a more stable version then that'll be my next-best try. Or maybe an outrigger? Or perhaps just ballast?
posted by anadem to Sports, Hobbies, & Recreation (18 answers total) 10 users marked this as a favorite
 
That's a beautiful boat. You can perhaps even repair its tippability, but you seem ok with building another. You need a hard chine.
posted by at at 9:21 AM on October 10 [3 favorites]


I used to make/repair old canvas/wood canoes; the technique for those is typically to steam-bend the ribs, but connect them to the inwale (which you may have done) to keep it all fairly stable.

You might consider retrofitting a keel onto the bottom of your current canoe; even a small one may help provide a bit more resistance against the water when the boat is tipping side-to-side. (This will have the added benefit of letting you worry less about abrading the bottom of the canoe's skin when it hits the shore, too.
posted by lhputtgrass at 9:27 AM on October 10 [3 favorites]


I find a lot of canoes somewhat unstable unless they are carrying an appropriate load. Does it ride better with a few jugs of water in there? Water is great ballast because it doesn't really sink if you flip.
posted by advicepig at 10:11 AM on October 10 [1 favorite]


Can you try out other short canoes and then measure your favorite for a plan?
posted by clew at 10:20 AM on October 10


What a pretty boat. Chesapeake Light Craft has plans for many lovely wooden boats and a Builders' Forum to share information.
posted by jointhedance at 10:44 AM on October 10 [1 favorite]


If this is something you think would be fun to do again, my advice would be to build another boat. There are a surprising number of books geared for a weekend builder working with simple tools and relatively cheap plywood, but many community programs use this one. The always-reliable Kevin Kelly explains why here. With your level of (hard earned) experience, it shouldn't take you long or cost a lot of money. You thought you were going to build one boat, but to get good and also to enjoy the process, you may actually end up building more than one until you get one you like, or because you come to enjoy the process. My advisor in college did not play the guitar, but he enjoyed building them from wood. By the time I graduated, he had made about five of them. People were always happy to be gifted one of his guitars. Maybe you have found your hobby?
posted by seasparrow at 10:46 AM on October 10 [5 favorites]


I asked a somewhat similar question previously, and got several answers that I think are pertinent to yours.
posted by bricoleur at 10:51 AM on October 10


What about adding a pair of stabilizer floats? (link goes to image search)

I can picture a clip-on kind of configuration that comes off for easy travel, but still sits secure enough to give you some security while paddling.
posted by chrisamiller at 10:56 AM on October 10


It's quite lovely. I am not a boat builder, just like to sail. I'd add a long narrow strip on the keel; it would add stability and improve steering. Meanwhile, some pool noodles could be attached to help you stay upright.

Really, you did an amazing job.
posted by theora55 at 11:27 AM on October 10


Looking at the pictures, it appears that the frame is narrower after installing the skin. Is this true, is that what you meant by rounder? I agree with what other have said about adding a keel.

Maybe add internal support while installing the skin.
posted by tman99 at 11:36 AM on October 10


I've built a few boats with my wife. One in almost this exact style (a dinghy with willow for the ribs).

Getting a hard chine is tricky unless you are much better at Steam bending than I am. Adding a keel is easy, quick, and easy to undo. I'd start there.

Then I'd build another! It's so fun to do!
posted by Acari at 12:57 PM on October 10 [1 favorite]


www.feathercanoes.com
posted by patnok at 1:43 PM on October 10


A keel will not help unless it's made of a material denser than water. A heavy rock on the inside bottom of the boat might help if you can fasten it in place, or it might sink the boat if you capsize again.

A trip to a kayak store or perhaps a look at the Chesapeake Light Craft website may help you understand boat dimensions. Look and length and beam. A long kayak, say 17', may be only 24 inches wide but a 10 ft kayak is going to be somewhere over 30 inches wide.

If you like the idea of skin-on-frame, you might look the Geodesic Airolite boats. They are astonishingly light, and are based on proven designs. The skin is a heat-shrink canvas material.

The idea of adding floats for stability is perfectly reasonable if you want to save your first boat. I've seen plenty of examples on the internet, including here.
posted by SemiSalt at 1:46 PM on October 10 [3 favorites]


This is all really interesting and I have thought of making a boat myself — but I just have to say that this is the funniest placement of “more inside” I’ve seen.
posted by kerf at 2:09 PM on October 10 [7 favorites]


A friend of mine is a luthier and canoe builder. I sent him a link to your question; this is his answer.
The simplest way to make a canoe FEEL more stable is to make it wider in the middle and flatter on the bottom. That will cost you some performance, though.

We also have to distinguish between "initial stability" and "final" or "secondary" stability. A flat-bottomed boat will feel very stable and safe at rest, but once you reach a certain point of heeling over, nothing will stop it from going over the rest of the way. In contrast, a round-bottomed boat may feel very "tippy" and unstable and be hard to keep perfectly still/vertical. But the further over it goes, the harder and harder it gets to tip it a bit more. (That's low initial but high secondary stability.)

Here's a very basic link to canoe hull design characteristics and some of the trade-offs.

http://canoeing.com/canoes/canoe-design/

I personally prefer a canoe with low initial but high final stability. I want it to be easy to heel over, but hard to tip completely.

As you lean the boat over, the ends will come out of the water, allowing you to turn it on a dime.
Hope this helps.
posted by workerant at 3:18 PM on October 10 [4 favorites]


Here is a nice article about stability in boats.

A keel (even a small one) will help keep you from rolling because it will act like an automatic brace.

Adding ballast will help, but I see that you're already seated on the bottom of the canoe. Ballast might get in your way. Does it paddle better with a passenger?
(Adding ballast to a boat that light just seems wrong to me)

You could go so far as to do the small "keels", one just below the waterline on each side, and one at the keel. I'm talking about 1/4" to 1/2" thick strips of cedar or ash. No real need to plan a bend, either. Taper the ends of the keel soon it won't snag on anything.
posted by Acari at 3:31 PM on October 10


Stability is a function of beam and chine. Chine makes the force necessary to pass the tipping point higher (but once you get past it, you're soaked), beam helps the overall tippiness.

On a canoe sometimes a slightly softer chine helps you "bank" the boat a little more in turns. The keel may help with slowing roll, but it's going to contribute more to "tracking" (as will a relatively flat boat, whitewater boats have a lot of "rocker" so you can turn them faster).

I've built at least ten, if not tens, of ~14' long "canoe" like hard-chine two-sheet-of-⅜-plywood boats. Pics of one of those builds, the competition is "3 hours, using hand tools and battery powered drills", we've done numerous practice runs. If I remember right... 26" of beam at the middle is too much, less than 20" gets squirrely. We've been building them with 24" or so of beam, and losing, so I think this year we're gonna try to do 20", might even try one at 18" and see if we can reliably keep from capsizing it while paddling like mad, but...

Given your materials, and that you can probably knock one of these out fairly quickly to feel how it paddles, I'd try at least two feet of beam, and, say, a 4-6" radius chine. That should be paddle-able, and give you an idea of what direction you want to go. More or less stable, smoother or more "cuspy" around the capsize point...
posted by straw at 5:04 PM on October 11


Looking at your build pics: My recommendations above, but make the bottom flatter, and, yeah, harder chine. Now that you've done one, you kinda know how the ribs will bend. Also, if you can apply all the longitudinal strips before removing it from the frame, they might help holding it out a bit. Just the gunwale strips will definitely try to compress it...

Edit: Or put the gunwales in before adding the rest of the strips.
posted by straw at 5:09 PM on October 11


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