With my designs at least, the keel shape is indeed a Bezier curve. The CAD system I use creates NURBS and they are a special form of Bezier curve.

While this would precisely define the shape of the keel, it is not really practical. Finding the parameters of the Bezier curve for non-computer designed boats would be a pain. And the parameters are not exactly something you can interpret by inspection. They would let you reproduce the curve on a computer, but what people want is a simple number they can look at and immediately say, "that boat has a lot/little rocker." The Bezier curve parameters don't do that.

: That seems like a good way to describe the rocker in very basic terms, but it
: doesn't allow for any of the complex curves the keel can describe that
: might occur for any given coefficient. Fore/Aft variations in rocker
: wouldn't be described well at all. It would work best for symmetric
: circular curves.

: Mike's bezier fuction would give that information exactly but who the hell
: wants to go back to re-learn their college math? Not me.

: I guess that's why rocker has defied easy description into the 21st Century.