wrote:
Looking for experienced boat builders here. I am building an okume kit
kayak and am wondering if I can save weight by not placing a full glass
layer inside the hull.

My thinking is that I can get away with only glassing the butt joints
and edges on the inside along with a thin coat of resin for
waterproofing. Yes its going to be weaker (no fiberglass to take the
compressive forces) but has anyone done any tests to see how much
weaker?

It's a lot weaker. Someone on the Kayak Building Forum
(www.kayakforum.com) did a bunch of torture tests on a variety of
layups. The differences in strength were pretty stiking.