Edmond's Power & Sail

I put this over in wooden baot building. Perhaps that was the wrong place. Here's my question:

I've been reading Edmonds' Power and Sail.

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

 

Edmonds is saying that there can be either transverse frames only or a combination of longitudinal stringers and transverse frames but not longitudinal stringers only. His discussion is related to aluminum skinned boats where the thin panels must be supported in short spans in order to get the needed stiffness. In a 14 foot boat this might be a moot argument anyway since a combination of gunwhale, keel and seating furniture plus a few stiffness ribs here and there should be sufficient. If your boat is plywood, additional stiffners beyond gunwhale and furniture are likely superfluous.

Or maybe I don't understand the question.