We went for a demo sail once on a Witness catamaran (light cruiser-racer-type cat, that I think was 35 feet long). It had what the designer referred to as a shoe keel, instead of boards. It's like a rail along the bottom of the hull, and I think it was shaped like an upside down "T" in cross-section. The "rail" was only a few inches deep from top to bottom.

Rick and I were very dubious about whether the boat would be able to point with this "shoe." But we were amazed at how well it pointed, with what appeared to be little or no leeway.

Is anybody familiar with this concept?