There are methods for figuring out center of buoyancy, etc, from drawings, but they are too complicated to outline here and involve the use of a planimeter. Maybe you could build a model for testing in your bathtub. It sounds to me like 9 feet is a bit off-center unless your hull form is very different at one end than at the other. If you would like, e-mail me your scantlings and I will run them through my hull design program. This would give at least a ballpark figure for centers of buoyancy and flotation.

: Hello all

: I am building a s&g. it is 15ft3"1/2in long over all and
: 14ft3"1/2in at the waterline. I want it to be a swede form.the max
: bottom beam is going to be 24-25 inches wide the max top beam will be
: 26-28 inches wide.the deadrise will be 2 inches I figure the placement of
: my seat will be around 9ft.Does anyone know how to figure the center of
: balance (or where to place the seat is my main question) for a swede style
: kayak.it is going top be a sit on top (I hope)any one out there ever buit
: one?I weigh 230. I want high initial stability (used for fishing) can
: anyone help out ,advise or forsee any problems, thanks for any input.