> Does it matter? I read a book on engineering called something like
> "Why Things Don't Fall Down". It explained that a joint or patch
> which is stronger than the surrounding material not only doesn't increase
> strength (what good is one-extra strong link in a chain) but in certain
> applications can cause concentrations of stress that actually weaken the
> overall structure.

An overstrong joint like a buttjoint is most likely to fail right beside the edge of the joint. Of course, you don't have to make a buttjoint overstrong, you can make it just strong enough. And you can taper the ends of the butt piece reducing the localization of stresses.

> In the case of kayak building, if the scarf joint is stronger than the
> rest of the wood, what point is there in making it stronger?

> The main issue, for me, is appearance. When I was a kid I would look at
> wooden boats and be very impressed, but I couln't understand for the life
> of me why someone would go to all that work and expense and then have
> these ugly bulges in the hull. Half the beauty of a boat is the long clean
> lines. The bulges caused by butt joints really detract from that.

Depends. My MillCreek was done with butt joints, and they are not visible on the hull. Yes, in an unsupported bend they are slightly stiffer then a scarf joint, becoming more visible as the bending radius decreases. But since my boat does not have particularly tight bends along its hull length, and is in fact supported in those bends by the pieces above and below it, it becomes a wash as the butt jointed area follows the same bend as the rest of the wood does. It is visible on the inside of course, but that doesn't concern me. In fact, they are incorporated into other functions like anchor points and such.

A large portion of the reason I went butt was worries about my ability to make a good scarf. Which, if you knew how badly I did in woodshop as a student, you'd understand. Between trying to get the bevels to match, and getting the two pieces to lay flush, I didn't want to do it. I did in fact try a bit with some scrap, it didn't go well. With a butt joint, you're not going to get one piece rising in relationship to the other, which is an unfixable problem. Oh, you can fill an area up with putty and grind it down so that the mistake isn't too visible, but it will stay a mistake. By going butt joint, I didn't have that problem to worry about, and could instead focus on the problem of alignment in two dimensions only, instead of three.

> The Pygmy seems to have some real advantages, but the use of butt joints,
> as far as I can see, might make construction a tad easier but have no
> other advantage.

Grin, for some of us it's more then just a tad.