: Paul,

: I could only see a zebra's ass

Hmmm the picture is not supposed to be in black and white. Myabe adjust your monitor?

: Don't you fear the stations would twist in a formed sea, so that instead of a
: 90* plus 90* stations-to-stringers angles you'd get 110 + 70 or else ?

Nope, no fears here. They will be aligned, and braced, fairly substantially.

Skin boats flex, so a change of a few degrees from moment to moment is pretty common. In order for any frame to change 20 degrees, one side of the frame would have to move fore or aft maybe 3 to 5 inches (It depends on which frame, how wide it is, and where it is placed) since the frames can only move by forcing the stringers to get longer, the skin would have to "grow" that much longer -- and that is pretty unlikely. If the frames moved fore and aft by as much as 1/2 inch the boat would be more flexible than I would like, and I'd take some acton to reduce that. But, i doubt i could hold tolerances to under 1/4 inch of play over the length of the boat -- and that I can live with. so my target is 1/8th to 1/2 inch of overall play, which should be fairly easy to achieve.

: Also, considering the lack of resilience of pvc, won't the whole structure
: sweep up at ends with the paddler's weight?

With my weight, it might merit its description of being a "folding " kayak. But I hope not.

The 1 inch pvc is about as flexible as the 1/2 x 3/4 wod chines suggested for some other SOF kayaks. There are some advantages to this actually. One is the added rocker makes turning easier, but I'll still have a longer waterline length, so speed and tracking should be adequate. I don't have any serious waves near where I paddle (mostly flat lakes and smooth rivers) but I understand the lighter and more flexible bows of boats such as these helps them ride over waves, rather than punching through them.

: So not to get a banana boat, will you use stanchions? Unless you'll run a
: polypro chord along the inside of the tubes in the lower part of the
: contraption, so as to make for the upward bend?

I'm attracted to the thinking of George Putz on crossbracing for making the sides very stiff and strong. I gave somethought to using PVc for diagonal bracing along the length of the boat, but the number of joints and connectors looked like it would make the project a nightmare. I think instead I'll go with the tried and true plywood bracing such as Klepper uses.

A few holes drilled through the PVC will allow me to set in bolts (not screws) that will hold short plywood panels. I can insert one or more frames between these plywood panels, and use fairly simple connectors to hold them firmly in place -- so not all of the frames will be secured between sections of pipe, some will be by the braces. The plywood will be on the inside "edge" of the PVC pipes, so with the panel separating the two pipes the cross section will look like a "C" beam, rather than an "I" beam.

: Pvc stations also make me skeptical.

Well, skepticism can be a good thing. I share that opionion with you. Using short sections for bracing should be fine, and being skeptical of their strength, I would tend to design these fairly conservatively.

: Just a few thoughts.

Thanks for your comments.

Now if I just get some pictures going right

PGJ