A round bottom will have low stability and a flat bottom will have maximum stability. Minimal dead rise will get you a more stable kayak. If your using ribs you'll need a tight bend from good bendable wood to achieve this.

: Ok, so I have two kayaks in Ontario that I built from Yostwerks
: plans (one glued and the other lashed) and was happy very happy
: with the way they paddled. Then I did three in Newfoundland, 1st
: with Instructables plans and by the forth no plans. Both were
: beautiful works of art. Unfortunately they where both very
: unstable (my own design better but still...) and didn't get used
: much at all. I did a fith one aswell, also my own design which I
: was very proud of. It was designed for someone for fishing. It
: was extremely stable (at 24" wide you could stand up in it)
: but I managed to preserve the very sleak, sporty profile (not
: boxxy) and somehow still maintained great secondary stability.
: It was to be outfitted with adjustable foot braces and
: comfortable seat so anyone could jump in and go. This design is
: not what I want for myself as I spend alot of time rolling. I am
: now in BC and very excited to start working on another but am
: desperately seeking the secret ingredient. I am not expecting to
: go on weekend trips, just something for day trips and rolling
: practice. I love building and don't mind doing a few but I spent
: more time building than paddling last year and am anxtious to
: get back on the water. Especially being on Salt Spring Island.
: All five boats are so very different and not with me so I can't
: give specs on all of them. I will say though that the ribs on my
: instructables boat ended up too rounded and the depth ended up
: two inches deeper than planed and so i fixed it by lowering the
: knee brace two inches (it was raised Two inches so I brought it
: flush) and I realize that was a mistake and should have redid
: the ribs. For the next one I opted for 1 1/2" ribs and less
: of them so I could focus on shaping them better (the wood there
: was terrible) but it was still hard to keep upright unless you
: where really moving. And yes I was looking at the shear depth
: and it seemed like it was going to be great...
: I am hoping someone else has encountered this problem and found a
: fix and can help me out. It is really embarassing to have
: everyone ohh and ahh your boat but never see you in the water.