Perhaps you should consider building a double paddle canoe. Woodenboat had an article on one about five years ago about one that was about 15 feet by 26 inches. I see a lot of people using sea kayaks in situations where a double paddle canoe would be just as good and often much more utilitarian. Because they have no deck they take considerably less effort to build, an important consideration for a novice builder. The weight of the extra freeboard is essentially the same as the deck on a kayak, so there is no difference in weight. It is a lot easier to camp, fish, and photograph out of a double paddle canoe and for folks like me with bad knees and fused vertebrae much easier to enter and exit and the extra squirm room--actually sprall room--- vastly increases the comfort. Obviously, an open boat is not ultimatly as seaworthy as a decked one in breaking seas, but that is the only advantage kayaks have over double paddle canoes.