IMG 1724PaulK

To expand on the difference between long and short keels and lift…

To develop the most lift possible for the wetted surface, naval architects tend to make keels short from front to back. An aeronautical example of this would be a glider. Its wings are long, but narrow. The curve of the wings develops lift that helps keep them in the air, especially at low speeds. Boats move at similarly low speeds, so boats that are fast upwind have deep fin keels that are fairly short on their chord, front to back. Developing lift in a long, shallow keel is more difficult. Water flows from the high-pressure side, under the keel, to the low-pressure side since the length of the keel (and it’s relative short depth) provide more opportunity for this than a long, narrow foil. The hull also interferes with flow on the keel surface. As an example, supersonic planes have long, backswept, “delta-shaped” wings. This design helps them cut the sound barrier and provides sufficient lift at high speed to keep them in the air. Your long keel is like the supersonic plane’s – but there is no way your boat can move fast enough to make it provide much lift. In fact, imagine a Concorde with wings 100 feet long but only 20 feet wide. It would not get off the ground. That is sort of what you’re dealing with, at 6 knots instead of 600.