: Not long ago I attempted to design and build a single chine S&G
: kayak with the bottom panels somewhere in size between those a
: Point Bennett 18 and a Chesapeake 17 and using the same type of
: geometry. I did not understand developable surfaces as well as I
: thought I did, being extremely ignorant of conical development.
: I worked out my offsets for the bottom panels assuming that they
: would "twist" from a dead rise of about 10 degrees
: amidships to nearly vertical at the bow and stern. When I went
: to stitch the bottom panels to the side panels, they did not
: match as they approached the bow and stern. I was able to cut
: off the sections that did not match, join another piece on,
: adapt the keel offsets from the Point Bennett &/or
: Chesapeake 17 which are quite similar and scribe the outer
: offsets to fit the chine. I completed the kayak and have paddled
: it for some time. I have since realized that I needed to use
: conical development in the bottom panels. Can anyone tell me
: where I need to put the apex of the cones to produce bottom
: panels like those on the Point Bennett and Chesapeake 17?

Depending on the thickness of the ply and how's it's bent, you can bend ply like you describe first, it's just not easy.

Plywood, or most sheet goods, will bend in either a circular bend, a cone shaped bend or a twist, but not two at once.
Well not without torturing it, a whole different subject.

Bill H.