All that is covered in the plans - but I advocate securing foam floatation in either end of non-traditionally built SOF kayaks. Those areas are usually not accessible - even for float bags - after the boat is skinned (though they are, somewhat, in the Chuckanuts).
Foam in the ends is just minimal floatation, of course, but is always there and will keep the boat afloat (but awash).

Float bags are always recommended for sea kayaks without bulkheads - and, yes, I personally also use a sea sock. Of course, the Chuckanuts are recreational kayaks, meant for relaxed use in milder conditions. But, ultimately, the end user has to judge the conditions and possibilities, and decide what is appropriate or necessary.

Yes, construction foam from the big box stores works fine. No need to seal it unless you plan to soak it for days on end. White styrofoam is not so great, but will work.
Epoxy glues foam nicely. Polyester resin does not.

Dave

: Hi all, this is my first post and I'm grateful to all who make this
: forum possible.

: These are my first attempts at building a Kayak. I'm building a SoF
: kayak designed by Dave Gentry, the Chuckanut 12. I'm also
: building a Yost SeeBee 13. I want to add flotation to these
: kayaks. Here are my questions.

: 1. Will styrofoam that can be purchased at my local lumber yard
: work? If not, what might work better. I don't want to use
: flotations bags, rather, I want to permanently attach these to
: the frames in the kayaks.

: 2. Where is the best place to locate the flotation. Closer to the
: stems and sterns or near the seating areas in the center of the
: kayaks?

: I suspect that adding flotation isn't really necessary, but one of
: these will be used my by 12 yoa grandson and my wife. They need
: as much stability as possible.

: Jim Adams
: KY- USA