KEY POINTS:
One of the teams in the America's Cup may have engineered a breakthrough that would give them a huge advantage on the rest of the field.
Public documents indicate a design team may have found a loophole in the rules that could potentially hand them a match-winning edge,
reminiscent of Australia II's revolutionary winged keel which helped them lift the cup from defender Liberty in 1983 off Newport, Rhode Island.
One or maybe more of the teams have created a legal version of a swinging keel, which could provide them with a speed edge.
Syndicates can ask the measurement committee for interpretations of the design rules. The submissions and interpretations are often confidential but are made public six months later.
Although the submission and the interpretations are public, the syndicate that asked the question is not.
The movement of the 19-tonne keel bulb just one degree could result in a speed gain. The yachts in the last round-the-world race showed phenomenal speed using canting keels, which move the keel bulb from side to side.
A swinging keel would be more subtle, moving the keel bulb only slightly. Under the America's Cup class rules, the yachts are allowed only two moving appendages under the water - the rudder and the trim tab attached to the keel.
The interpretation appears to approve the swinging keel. If that is so the major issue for the syndicate will be how it proves it complies with the rules.
All the teams, including defender Alinghi, dropped the skirts on their boats on April 1. There was a slight bulge on the sides of the keel fin on one of Alinghi's boats near where the keel joined the hull which could indicate the keel might have a mechanism that allows it to move independently of the hull.
"The America's Cup is littered with fine ideas that have fallen at the compliance hurdle," yachting commentator Peter Lester said.
"In the last cup in Auckland it was Team New Zealand's hula [hull appendage] which worked well in practice but struggled when it came to complying with the demands of the measurement committee.
"Previous campaigns have fallen victim to the pressure of trying to implement contentious changes such as Team New Zealand's bowsprit in 1992 and the Plastic Fantastic fibreglass Kiwi 12-metre in 1987."
Lester says this could be another planted story as the America's Cup is littered with such moves.
But it might not be the case.
The Swiss have been fiercely protective of parts of their boat over the past two years, especially the bottom section of the mast.
One of New Zealand's top yacht designers, Greg Elliott, was surprised there might be a syndicate with a swinging keel because of the cup rules.
Elliott, who has designed many yachts with canting and swinging keels such as the giant 30m supermaxi Maximus, said: "If someone has a swinging keel it's all over. It's like putting a V8 motor in a Mini.