For small critical wood members like gunwales and chines, stringers etc. on a SOF, there should be no knots. There really isn't any extra wood to compensate for the lack of strength lost with a knot.

Knots are sometimes ok in they are tight in other types of kayak construction, not so in SOF frames.

This doesn't mean though that you have to have full length clear wood, you can definitely scarf smaller pieces to get the required length.

Bill H.