sailing upwind; lift ratios; sail-to-keel ratio

In writing up a description of some of my physics-of-sailing results, I realized some things about sailboat design. For deep reasons you want the ratio of the area of the sail to the area of the keel to be roughly the ratio of the density of water to the density of air, or 700. That flows from the point that the sail and the keel have symmetric roles in sailing. But if you set this ratio to 700, you can only sail upwind if the sail lift ratio (the ratio of useful sail force to drag force) is very high. Since it is hard to make this lift ratio high on a commercial boat, the alternative is to make the sail smaller (relative to the keel). Looking at the data I can find on real sailboats, most have okay lift ratios but small sail-to-keel ratios (smaller than 700 anyway), so that they can sail quickly upwind. The cost of these design choices is that you can't go downwind faster than the wind. If you want to be able to sail both downwind faster than the wind—and also upwind—you have to have amazing sail and keel lift ratios.