: I'd second that! FreeShip is still avilable on the Net and does a
: nice job of generating plank developments, and some other useful
: stuff as well.

: I don't think it's a question of locating the apex of the cone
: correctly - you probably don’t have a cone.

: When the angle of a boat plank changes along its length it can
: either behave like a cone, or like a plane’s propeller. The
: conic does not involve significant stresses within the material
: and is easily predicted; the material is not being twisted, it
: is merely being bent with the bend axis changing along the
: length. The “propeller” style is a true twist and involves
: stretching along the edges and compression along the axis. If
: the plank development is asymmetrical to begin with, the
: resultant shape is hard to predict without a computer. When
: placing such a plank one a hull it requires more force to get it
: to fit than a conical plank.

: As an example, when I adapted the lines of J. Henry Rushton’s
: lapstrake “Wee Lassie” to chine ply construction, the two
: bottom planks seemed to form a single plank. I assumed Rushton
: had problems getting wide cedar planks, not a problem with ply,
: so I merged the two planks into one, thinking to save myself
: some work. When I formed the resulting double-width plank
: several inches of extra rocker appeared from nowhere *. The
: bottom edge of the plank had stretched. It took me some time to
: figure out what had happened but when I went back to using two
: narrower planks the plank formed as expected. Rushton knew a
: thing or two!

: * FreeShip had provided such an odd plank development that I
: assumed it had a bug and smoothed out the wonky-looking bottom
: edge: big mistake!

Dear Ancient, I wonder if you are as ancient as I am. I have had Delftship for some time but have had trouble using it to design a hard chine kayak. It seems to be very easy to use for designing soft chine craft. I will follow your advice and try again with Delftship. Many years ago I built a small canoe on little more than guess work which was inspired by some 1950's sail boat designs which I now realize were based on classical conic sections theory from about 250 BC. A few days ago I went looking for the apex of the cone into which the bottom panel bent. I found it and realized that the inner offsets would be very similar to those of the Chesapeake 17 & Point Bennett 18. I think that the bottom in my current design may be part of a simple cone.