America's Cup anniversary

The international sailing community celebrates 162 years of yachting in the America's Cup on this day. In 1851 yachting was a pastime rooted in the success of a vast and deep maritime tradition, reserved for a wealthy elite. Today it has grown out into a competitive youth sport with dinghies whilst its superyacht industry remains attractive to private fortunes. The 1851 schooner America's innovations are hardly comparable with that which are developed for today's eponymous cup and the AC72 catamarans. Nevertheless we can draw the following:
  • The 1851 schooner America, whose lines were those of a New Englang pilot boat with a very fine entry and run, differed with most 19th century American yachts in that she did away with the centerboard, and in turn most 20th century racing yachts did not feature centerboards. For the 2013 America's Cup, the boards are back, but the vessel type has changed from a seaworthy pilot boat to a bleeding-edge catamaran with daggerboards. For upwind legs, the new boards serve as a conventional lateral resistance plane; For the reaching and downwind legs, a loophole in the AC72 class rule allows the boards to be exploited as hydrofoils that provide vertical lift and enable the catamarans to exit displacement mode. The hull lines are developed for hydrodynamic performance in upwind legs and very light weather conditions only; with the whole package developing as little aerodynamic drag as possible when foiling speeds are achieved.
  • The 1851 schooner America's cotton sails differed with those of the British fleet, which used a flaxed linen fabric. For the 2013 America's Cup, "soft" sails are replaced by solid wingsails with a very high aspect ratio, generating horizontal lift controlled at different rig heights by flaps on the trailing edge. The drag is negligeable and the thrust so significant on reaching legs that the speeds which can be achieved generate in excess of 7 tonnes of vertical lift on the daggerboards when their rake is adjusted properly, enabling the catamarans to exit displacement mode (fully loaded and crewed displacement is circa 7 tonnes for this boat class) and fly above water. Yachtsman Ken Read attended a trial on Team New Zealand during which he observed a top speed of 46.5 knots on the speedo.

Above are the lines plans of the American challenger America in 1851 and American defender Oracle in 2013, carefully drafted by yacht designer Fran├žois Chevalier. For the lines and plans of all the other candidates, challengers and defenders between 1851 and 2013, read Fran├žois Chevalier & Jacques Taglang's books America's Cup Yacht Designs (printed 1987) and The Louis Vuitton Cup (printed 2013). Read all about the schooner America on their own blog here.
Finally, watch yacht designer Ian Burns' explanations on how the AC72 wingsails and hydrofoils work here:

A wink to the past by photographer Guilain Grenier

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