: Now some questions: 1. How to secure the longerons (right word?) to the ribs?
: I've thought about cutting a larger piece of PVC in half lengthwise (so
: far I'm using 1/2" pvc, so let's say here I'd use 1". Then take
: a 1" piece of this and gluing it horizontally to the outside of my
: vertical rib. This would provide a place for the longeron to nestle, and
: support the joint. Then I could drill through the longeron and the rib to
: have a hole into which to place a clevis pin. Thoughts on this? A better,
: stronger way come to mind?

Rather than cutting the 1" piece in half, just notch it where it intersects the rib - should be stronger.

: 2. Is there a better way to construct my PVC pipe/plywood "I-beam"?
: I want it strong first and then secondarily easier to build. I haven't yet
: glued my prototype. Any recommendations of a glue to use to join PVC and
: wood (the PVC solvent did nothing but give me a mess to clean up).

I like the method of slitting the pipe. Rather than the drill saw, use a table saw, and clamp the pipe to a piece of wood to keep it straight. As for glue, you might try epoxy. It will definitely stick to the wood, don't know about the PVC - but it may not need to. If you can get a bead of epoxy on the top of the plywood - inside the slot in the pipe - it will keep the plywood from coming out.

: 3. My thought is to get Putz' book and create real size plans on paper, then
: place them on a piece of plywood and use nails around the perimeter about
: every 1.5" as a guide for making my ribs. Anything more elegant come
: to mind?

That would work - and is similar to how Dyson forms his aluminum ribs. The problem is that Putz does not have a form everywhere you need ribs. He uses 5 plywood forms spaced about 30 inches apart (depending on which model you choose), inserts the stringers, attaches the end forms, and then installs the frames. It is the frames (12-15" apart) - not the plywood - that are located where you want your ribs - and there are no plans for the frames. The frames are cut to fit the stringers. The plywood forms give the boat it's initial shape, but are removed once the frames and trusses are installed. You could probably use the forms for ribs, and then place an additional set of ribs half way between each of those forms - but you will have to determine the shape on your own - not difficult with a CAD program.

: 4. I want the kayak to be able to carry about 250 lbs. (Me + an easy week's
: worth of food and gear). Could I reasonably expect the Putz boat to do
: this?

Putz's book has two designs - a 17' and 18.5'. The larger boat looks like it could easily meet your needs.

: 5. Are there other designs I should consider?

Any high-volume strip-built design could be considered. The offset tables could be used to set up that piece of plywood to bend your pipe around to form your ribs.

: Could a reasonably sturdy and cheap folder really be possible?

Probably - but will your sanity still be intact when you finish designing it?

Good luck,

Ken