Mihail

I think I understand what you are thinking of doing. Is it possible? Yes. Several recent posts here have shown completed ply frame canoes or rowboats, so it is possible.
If your real concern is reducing the plywood used, I would like to tell you that I used less than a half sheet of ply in making the frames for two Sea Fleas and my 17ft ply frame "Iggy". Ply was also use for some of the stems and other little bits.... So for plywood savings alone, I would not suggest doing as you are thinking.
By adding in 'traditional' deckbeams, you will have to cut compound angles, which is more work. The deck beams would be mainly for supporting the deck stringers. With the rather thin 'gunwhales' on the Yost-style frames, I am not sure whether I would trust the thinner deckbeam and gunwhale joints to really support my weight on the rear of the coaming when getting in and out...
Anyway, just a couple of thoughts for you.

kelly t

: Toying in my mind with some ideas on how to most easily and cheaply do my
: first SOF. I'm tempted by the Yost plywood/wood frames (no bent ribs). But
: this design would use a lot of plywood. So, can't one instead use open
: plywood sections? Each shaped like the original, but instead of like a
: closed curve, leave the top open like a "U"? This way they can
: fit into each other pretty close when drawn on the plywood - there will be
: very little wood wasted for the opening since each next section will
: follow the contour of the previous reasonably well.

: The open top of the sections will be closed by cross-members b/w the side
: boards just like in a bend-ribbed design.

: Thoughts? I have not seen plans done this way but it seems fast to do (only
: cutting, no bending) and uses considetably less plywood...

: May be the last couple on each end of the fram don't need to be that
: complicated and can just be cut the "traditional" way with a
: hole cut out for weight savings...