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T wo extreme AC72 foiling catamarans with wing sails went head-to-head at over 40 knots in San Francisco

Bay, California. The teams were competing in the 2013 Americas

Cup Challenge which took place from

September 7-21, 2013.

Anyone watching the fi rst few days of Americas Cup sailing will know that it looked like Emirates Team New Zea- land had a seemingly untouchable lead – then out of the blue Oracle Team USA completed one of the greatest come- backs in sport to win the 34th America’s

Cup. For anyone who has watched the rising speeds of sailing records plus the development of hydrofoil technology, this event was also bound to be a game changer for ‘power versus sail.’ Another race was on in San Francisco Bay as

Chase Boats and Umpire Boats utilized gasoline and diesel engine horsepower versus the AC72 boats utilizing wind energy, aerodynamics and hydrodynam- ics.

The AC72 is a state-of-the-art design wind powered craft. Overall length is 86 ft. (26 m), waterline length is 72 ft. (22 m) and it has an extraordinary beam of 46 ft. (14 m). The boat only weighs 13,000 pounds (5900 kg), it has a maxi- mum draught of 14 feet (4.4 m) and is handled by a crew of eleven.

The AC72 rises out of the water on foils and designers always expected it to sail faster than the wind. Predictions were upwind at 1.2 times the speed of the true wind and downwind at 1.6 times the speed of the true wind. But the

AC72 has proved to be faster, averaging about 1.8 times the speed of the wind, with peaks slightly over 2.0 times the speed of the wind. The extreme foiling catamaran design means that AC72 rac- ing takes place on the edge of control.

There is potential for crews to fall overboard or to require immediate at- tention in case of injury. Each team is allowed a Chase Boat and to provide a margin of safety these high speed craft need to not only match the race boat speeds, but to be able to exceed them.

With the wing mast / sail set up if a crew breaks something, they can’t just turn and go home, because the wing stays loaded up.

The support boat has to be able to tow an AC72 home faster than the wind speed, which can mean towing at 25 knots. The boat also needs the puling power to be able to right an AC72 after a capsize – fast.

The crews try to avoid the dangers of a capsize but it is a possibility that sup- port teams must plan for.

Tragically in May 2013, British

Olympic sailing champion Andrew ‘Bart’ Simpson died after the Swedish

America’s Cup craft he was sailing cap- sized and broke apart in San Francisco

Bay. Simpson, a 36-year-old two-time

Olympic medallist, suffered multiple blows to his head and body in the acci- dent involving the 72-ft. Artemis Racing catamaran. The San Francisco medical examiner’s report said, ‘In the moments before it capsized, the yacht was turn- ing downwind in a so called bear-away manoeuvre while travelling at about 30 knots, with wind of about 20 knots. The front of the vessel then dipped beneath the surface, the port hull broke and in- verted on top of the wing.’

With an Interceptor, a RHIB and a Cat

Chasing America’s Cup BoatsCup Boats

By John Haynes

MR #3 (32-41).indd 41 3/5/2014 11:36:37 AM

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