: i would think that increasing the length of a narrow yak will make it more
: unstable unless rocker is added. as you increase the length, the vol goes
: up lessening the w/l beam making it narrow while at the same time the cg
: goes up.

Lengthening the boat can increase stability. Increasing the volume may make the boat float higher which will raise the CG thus decreasing the stability, but it does other stuff as well.

Initial stability is due to area on either side of the centerline. If you look at a plan view of the waterline while hold the width the same, and increase the length, you will see that the waterplane area increases. The result is generally higher initial stability.