: Hi, PGJ. Thanks, for the reply.

: I am quite lucky here, I have great sources for both Aluminum and
: wood. My neighbor has a lumber yard and my fathers fishing buddy
: buys & sells all kinds of metals. I chose aluminum to cut
: down on pack size and the button-clip joins are quicker to
: assemble on site than a wood/wingnut configuration.

Check out www.klepper.com and get a look at the grand daddy of folding kayaks. Klepper has been making these things from wood for about a century. There are a lot of 'em around which are 25 to 50 years old, and that is the projected lifespan of current models. I've seen friends put together their Klepper in 15 minutes. As her dad did, and his dad did :) And as for pack size--well, Klepper will happily display the compact pack size, just check around on their site. and yes, you can easily repack the boat to fit into those bags. It is not like Christmas presents which won't go back into the original box.

I like aluminum, but this is a forum for wood boats, so I had to get a plug in for forest-grown materials.

Build carefully and with consideration. The modern materials you are using will give you a boat that has the potential of outlasting the venerable Klepper design. You really are building something that can last a long, long time. Get a good design before you commit to cutting, and you will be happy with your creation, and proud of your accomplishment. I promise.

: I have
: priced the Aluminum for £40 (or around $65 USD) which isn't too
: bad.

Actually, that is Very good. About 1/3rd of what I paid for aluminum for a Yost folder. Apparently I've got to find a cheaper supplier than Texas Towers.

: The birchbark canoes really are a thing of beauty. A British
: survivalist and a bit of a hero of mine, Ray Mears, builds a
: birchbark canoe with the help of an Algonquin canoe maker in one
: of his TV shows. I have been smitten with them ever since.
: (..think I might watch that episode again later :D)

You would also enjoy the book "The Survival of the Birch Bark Canoe", by John McPhee. www.johnmcphee.com/survival.htm

He writes about a canoe builder named Henri Vaillancourt who builds these boats. Vaillancourt's web page is www.birchbarkcanoe.net, and the photo below is from the homepage.

: An envelope is a great analogy. So gunwale length will affect the
: hull-rise and rocker too (when thwarts/cross sections are
: added). I was concerned that while trying to create hull-rise
: the tension of both gunwale ends trying to push back down would
: bend the keel and I would be left with negative rocker :s ...You
: have successfully quelled those fears! Haha!

Looking at the picture below you can see how 5 thin thwarts are used to keep open an 18 foot canoe. Another picture at Vaillancourt's website shows a 14 foor abnaki style canoe where the rise of the bow is easily observed. This one also uses 5 thwarts. If you compare it with the longer boat you'll see the center thwart defines the width of the boat, while the two shortest thwarts, near the ends, act more to pull in the gunwales and define the end profile, rather than press outward to resist water pressure. The intermediate thwarts are used as seats and backrests--and in my opinion could be structurally replaced with seats--and they also serve as structural support, tying the gunwales together, defining the lines of the boat.

: This is a good idea, quite a few manufacturers use aluminum ribs
: but I never thought It would be as simple as screwing the HDPE
: to it. I may have trouble bending the narrower ribs towards the
: stem and stern but the wider center ribs could certainly all be
: done like this.

A propane torch will heat up your aluminum tubing to a point where it can be easily bent into very tight curves. Unlike steel, which nicely changes color as it gets warmer, and is soft enough to bend when it is orange or red, Aluminum has no color change to help you. And it gobbles up heat. So keep the flame moving over a wide area, and keep testing it as you heat the tubing. When it feels like it can be moved with slight pressure, move it quickly to your pipe bender, or bending jig. To get very accurate curves, you can make a template from plywood or particle board and bend your tubing around that. For one or two ribs this will hold up very well, although the wood might smoke a bit from the heat. But it shouldn't get hot enough to catch fire. Even so, a bucket of water is good to have around. If your design is symmetrical you'll need 2 identical ribs from each form. four forms give 7 ribs. Find a canoe plan and cut your forms small enough to allow for the thickness of the tubing and the chines over it.

I have a puddle duck canoe, which at 14 1/2 feet is a little longer than your 4 m plan, but it does hold the weight you are considering. The plans for the building forms are in Gil Gilpatrick's book "Building a Strip Canoe". I just checked for this at Amazon.com and they show that he has a new edition coming out which will have full sized plans. The older edition I have has reduced-size plans which were just fine. If you can get the old edition at a close-out price, go for it. As I recall there were 7 building forms made from 4 plans, a center one and then two copies were made for each form moving from the center to the ends. These were spaced 18 inches apart. That would put them in just the right place to support lightweight chines. You might want to look at that design.

PGJ

Below, a birchbark canoe by Henri Vaillaincourt, from his website, www.birchbarkcanoe.net