Edmonds Calcs

[JEM]

Reading Edmonds' Power and Sail and wonder about his formulas.

Let's say we're developing a small power/planing fishing boat (14' range) with bench seats. Design proposed no more than 20" between frames or hull sides (that's going to outside dimensions).

I've read his book over and over and one point is not clear to me. He says frame spacing can be longitudinal or lateral. In doing the calculations, does that mean you could have longitudinal stringers 20" apart running the length of the boat and not need lateral stringers except for where your seat frames
fall? Or should it be thought of as 20" squares?

Thanks