Something to consider. Feathercraft doesn't spec their materials because they're expensive, but rather because they're effective. If they could make the boat cheaper and expand their profit margin without compromising safety, I'm sure they would...

Specific problems. The key to the design isn't the rib shape- any hard chine Greenland shape will give you a good place to start. What determines "success" first is safety, with performance in the water, weight, cost and ease of set up as negotiable priorities. Your choice of stringer stock is risky at best - PVC conduit is VERY flexible (which is why it's so durable), and heavy. You're likely to have a very manuverable boat, as it will bend like a bananna and give you a short waterline and tons of rocker. Manuverable until it folds in half and traps you in the middle... If you could figure a way to use the conduit's tensile strength effectively, you might have something... but of course, tensile strength goes out the window when you have slip-fittings.

I've built a skin boat, and am planning a take-apart (I hesitate to use the word 'collapsible'), and believe me, it's not a trivial process. What makes a skin boat strong is how the frame spreads and shares the load among all its parts - folding boats have relatively few parts, and concentrate stress at the weakest points of those parts. Combine that with the fact that your joints are designed to be easily disassembled... well, you get the idea.

People HAVE made cheap boats out of willow branches and tarps, PVC pipe and such... none are something I'd willingly trust my life to. Just some things to keep in mind!

Be safe,

Nathan

: Okay, take "collapsible" and "cheap" only in the best
: senses of the words.

: Play with a "what if" for a moment...

: What if I made a cheap knockoff of the Kahuna by feathercraft? I'd need
: properly sized ribs made of plywood instead of their "injection
: molded polycarbonate", and instead of the aluminum stringers, used
: PVC conduit pipe (I got some of this stuff and abused it mightily with a
: hammer with no material failure - the grey stuff not white plumbing PVC.
: No way that aluminum or wood could have withstood that attack so well).
: Then I could make a skin of the recently mentioned PVC material used on
: billboards, or scraps from a truck tarping company.

: Cheap? Yes. Light? Enough. Doable? Maybe. But what do you more knowledgeable
: folks think?

: The key to the whole thing, IMO, would be to have a really good rib design
: since that is what would determine the boat's shape. Any ideas how I could
: get tracings of the Kahuna's ribs and measurements between the ribs?

: deliriously,
: Wayne