Despite selecting the most knot-free board at the lumber yard, only about 3 of the narrow stringers remained in tact - the others broke at a knothole or weak spot. In this photo I'm matching up some good pieces for scarphing.
I fashioned a simple jig that allowed me to stack two stringer pieces and make one angled cut through both. Flipping one of the pieces around created two mating angles that glued together for a clean scarph.
Here the first stringer on each side is in place, loosely secured to the stations with zip-ties.
Two of the forms have notches that hold the stringers in position. The others are smooth, allowing the stringers to be moved around slightly.
After a lot of "eyeballing" and adjusting for straightness, I zip-tied all the stringers tightly to the forms.
At the bow and stern, the stringers are trimmed and shaped to transition into the stems similar to the gunwales.
After shaping, the stringers were glued to the stem. (One popped loose, so I added lashing to all of them.)
Next come the cross ribs. They have to be bent, usually by utilizing some type of steam box. After reading about several alternatives, I came up with an inexpensive and simple solution (see next section).