Scaling

Somewhere, sometime in the distant foggy past, I read an article on
scaling of boats. I do not mean model boats but the full-grown kind
that we build in backyards and other sundry places.

If I recall correctly it stated something along the lines that, "if you
double the length, the beam should be increase by say 40% and the
height of the shear about 15%-20%".

If someone could point me to this article, or correct me on these
percentages, I would be eternally grateful.