All sorts of interesting things happened back in 1983. McDonald’s introduced the Chicken McNugget, Microsoft Word was released, and Swatch watches were all the rage. For sailors, however, the biggest news of 1983 was when the 12-Meter Australia II defeated Dennis Conner’s Liberty off Newport, RI, taking the prestigious America’s Cup from the United States for the first time in 132 years. But how did the Aussies do it? A radical new winged keel design was largely credited for Australia II’s win, and it changed the face of sailing yacht design for the next three decades.

A photo of Australia II's winged keel.

People crowd around Australia II's revolutionary winged keel on the evening of her 1983 America's Cup win. Photo courtesy of Wikimedia Commons

Literally from the minute the Ben Lexcen-designed Australia II arrived in Newport for the America's Cup, the New York Yacht Club began challenging its keel design, stating that it didn’t meet 12 Meter design requirements. They went so far as to say that the keel was by a group of Dutch naval architects, not by Lexcen himself. In the end, the New York Yacht Club lost these challenges and Australia II was allowed to compete, beating Dennis Conner’s Liberty four races to three. On the evening of the win, Australia II was hauled out of the water in full view, allowing the first-ever public glimpse of her revolutionary keel.

A photo of Australia II's winged keel.

A closeup of Australia II's winged keel design. The boat is now on display at the Western Australian Maritime Museum. Photo courtesy of Wikimedia Commons

To truly understand the brilliance of the design, you need to imagine the keel in action when a sailboat is heeled over; that’s when those two wings take on a more vertical position in the water. This reduces the leeway (the wind pushing the boat sideways), allowing it to sail upwind more efficiently.

The wings were also angled downward, so they acted as a dihedral. In layman’s terms, this downward angle provided more stability, much like upward angled wings on an aircraft do. Lastly, the wings added additional ballast to the bottom of the keel, which lowered the boat’s center of gravity.

A downside of the design was extra wetted surface, which negatively affected downwind performance.

Over the coming two decades, winged keels started showing up everywhere, both on cruising and racing boats. While the design element fell out of fashion on most racing boats in favor of long-finned bulb keels or keels that cantilever, you can still find more than a few modern racers with some sort of wing or horizontal foil element on their keels. You can thank some Aussie ingenuity dating back almost 30 years for that.