An American journalist claims to have uncovered evidence that Oracle Team USA broke the rules in their famous comeback win over Team New Zealand in the 2013 America's Cup.
Oracle's incredible 9-8 win in the San Francisco regatta after trailing Emirates Team New Zealand 8-1 is widely regarded as the greatest comeback of all time. But former Wall Street Journal reporter G. Bruce Knecht has cast doubt on Oracle's methods.
In his newly released book, The Comeback, Knecht alleges Oracle used a sailing technique that was prohibited under the rules - an assertion America's Cup officials deny.
Knecht claims Oracle used a technique known as "pumping", whereby the crew repeatedly reeled in the wing to the optimum position, then let it out again.
Given the pressure of the wind against the enormous 40m wingsail, the technique provided added propulsion.
But the rules of sailing specify propulsion is only supposed to come from the boat's normal interaction with the wind and water - not man-made energy. The crew can adjust the trim of the wing, sails, rudders, daggerboards and hulls, and perform other acts of seamanship, but pumping the sails is prohibited.
Knecht made the discovery after speaking to key personnel in Oracle's Cup defence, and said they didn't necessarily know what they were doing was against the rules.
"[Oracle wing-trimmer] Kyle Langford, who managed the pumping of the wingsail, told me extensively exactly how he did it. He told me he'd let the wing out and then reel it in three feet and release it again - he was very proud of the technique," said Knecht.
However an America's Cup spokesman said the conclusion Knecht drew was incorrect, with the wording of the America's Cup racing rules containing a crucial variation of world sailing's official rules.
"The guy who wrote the book either didn't know there were different rules, or didn't understand what it meant," he said.
"To think that ETNZ wouldn't have noticed its opposition doing something like this, were it against the rules, is beyond belief. The umpires would also be in position to assess a penalty under this rule."
Team New Zealand were not prepared to comment on Knecht's revelations. A spokesman for the syndicate said he was yet to read the book, and the team were "looking ahead rather than backwards".
The book acknowledges the questionable technique is not the only reason Oracle won, outlining "a perilous re-engineering of the boat", a crucial crew change and the "superhuman" efforts of the crew and management when faced with a seemingly insurmountable deficit.
World Sailing rules
42.1 Basic Rule
A boat shall compete by using only the wind and water to increase, maintain or decrease her speed. Her crew may adjust the trim of sails and hull, and perform other acts of seamanship, but shall not otherwise move their bodies to propel the boat.
America's Cup rules
Propulsion: A yacht shall compete only by using the wind and water to increase, maintain or decrease her speed. Her crew may adjust the trim of the wing, sails, rudders, daggerboards and hulls, and perform other acts of seamanship.