: The reason I asked this question is I was sceptical about the practicality of
: it and still am.

You are ot the only one. Again, I repeat that this is still in the "experimental" stage. It is something to play with. If it works out in any manner, then maybe someone will want to try to go further.

: As a design proposal what you put forth is so long and
: complex and so full of unaswered questions that getting a boat out of it
: looks like a life's work.

hehehe. That could be why I haven't gotten a boat built from it yet!

: . . .One thing is certain. Jumping thru' all the hoops that PVC construction would
: require is the best argument for not bothering with it.

Until Pi was known with some accuracy there wasn't much use for math formulae related to circles--but that didn't keep people from using circles. They just didn't bother with the math, and stumbled thru. The Sci-Fi author Robert Heinlein used to make cracks about Indiana still not accepting the real value of pi. They had at one time legislated that it be calculated as 3, which he thought was absurd. I'm not sure of the whole story with Indiana, but next door, in Illinois, there was a time when round barns were the craze. The state taxed the barns based on their volume, and for round barns they were instructed to use the diameter times 3 to get the taxable area. Well farmers knew that with that kind of math, with round barns they would have more area than they were being taxed for. I suspect Indiana did something similar and just let the law linger long enough to become a joke.

I mention this because the complexity of a subject does not always make it a difficult project. There are almost no areas on a canoe which have square joints. But we make the parts and components on tools which are set up to cut square edges. The discoverers of calculus (Newton and Descarte) would look at strip building and hold it in awe. The compound curves of the hull are approximated with numerous thin strips. It is the same as breaking up the area under a curve into a large number of thin rectangles. It is easy to calculate the area of those rectangles, and average out the discrepancies. We use sandpaper to eliminate OUR discrepancies. If we used thinner strips we would need to do less sanding later on. If we used a very large number of very thin strips we'd never finish gluing them. Eventually we found the happy balance of 3/4-inch-wide strips--and that seems to be the standard size, though people will go with larger or smaller widths. I suspect that when more of the kinks are worked out that PVC tubes --if they are found to be practical-- will be a fairly simple material to use and the construction process will be less complicated than Stitch and Glue, or mortised and lashed wood frames for SOF kayaks.

: Just because something can be done is not a good rational for doing it. There
: has to be a payoff. What would a PVC boat give you that you couldn't get
: using the common materials we already use?

Good question. Don't have an answer for that yet. That may actually end up being more than one question -- and I'd want to have answers for all of them. Gotta build a few boats from these materials and try them out. The first one or two could take a long time, but once it gets rolling, I'm hoping that the primary benefits will be in the areas of lower cost, faster construction, easy joints for "folding" (or collapsible) kayaks, and plentiful availability of materials. The last part is already existing, and stimulates to drive to make use of these resources.

Long lengths of clear wood are getting harder to produce each year, so the cost is slowly rising. People who have the tools and knowledge to produce scarf joints spend time to make long lengths of wood out of shorter ones. Whiole the price of tools is coming down a bit, so is the quality of those tools. People who want to build a boat should not need to invest in a table saw in order to build their boat. Replacing the long wood components on a kayak with aluminum has been a viable method for several years. Aluminum is more expensive than wood. PVC would be about the same price as wood, and might be a bit cheaper, as it doesn't need to be sanded or painted, and it won't rot.

I think that when plans come out for a PVC framed boat, such a boat will be fast to construct and inexpensive. Ideally you could build such a boat in a weekend, and with some experience, maybe make one in a single day for under $100. if such a design could be made in a manner which would allow it to be disassembled easily for storage--and then reassembled easily for use--then you would solve a couple more problems which potential kayak owners face.

So those are the targets. One nice thing I've found about playing with this stuff is that it leads me to think about ways in which aluminum, or wood could replace the PVC parts--and that leads into new realms of design possibilities.

Thanks for asking

PGJ.