The winning keels in the America’s Cup in 1992, and all subsequent Cup races up to 2007 – that is, as long as IACC boats were used in the Cup – were designed according to a patent filed by Gabriel Heyman in 1991.
The patent concerns a very simple but, perhaps you could say “quitely revolutionary” concept whereby a keel with a flap at its trailing edge is designed to act as an asymmetric wing. The concept was so powerful in increasing lift and reducing drag that the elapsed time difference around an America’s Cup course could amount to up to 3 minutes, or more. Still, there was no technical complication involved – just a difference in shape.
The enclosed article was written for Seahorse (UK) magazine in 1992 and has since been published in a number of other magazines. Read article (pdf opens in separate window)
A study was made at the university of Budapest in 2009 by Tamás Korenchy, in Hungarian here
with an abbreviated summary in English here
From the Cup races in the light winds off San Diego in 1992:
The concept has not been used widely for yachts other than IACCs, because for most cruising yachts it is not desirable to add the complication of a trim tab, and for most racing yachts it is prohibited under the racing rules. However, the concept is still as viable today as it was in 1992 and has since been used in for example the design of wing sails.