It has been suggested Alinghi may be doing something with their keel to give them a speed edge in June.

One of the teams asked the measurer questions in relation to stiffening or supporting the keel fin.

While the measurer answered "no" to a lot of the questions, BMW Oracle Racing designer Bruce Farr BMW worries that one of his rivals has found a way around the wording of the design rules and used the example of Team New Zealand's hull appendage in the last cup as something the rule never intended to allow.

"In the past the rule has been pretty liberally interpreted in some areas and not really kept true to its extent," said Farr, who helped create the America's Cup Class Rule in the early 1990s. "One worries that someone has found a way around the wording in the rules that allows them to do something that clearly the rules didn't intended to allow."

When asked if he'd spotted anything on the Alinghi boats to suggest they had conquered the problem of the keel fin deflecting, Farr pointed to a slight bulge near the top of the fin.

"I see something on those boats. There is a shape-change line about 30cm down from the hull on the keel, where you can see a change in the surface shape of the keel fin, which looks a little strange to me and indicates that there is something happening there".

"It may just be some change in the structural design of the keel at that point that requires taper and widening above there. It could be a sign there is something going on."

When asked what, Farr said: "There is two things you might try to do to get an advantage with some kind of a controlled structural defamation or linkage of forces. One would be to have the keel drop vertically to become deeper to increase the stability of the boat. The other would be to try to offset the rotation of the keel so instead of deflecting to leeward and losing stability when the boat heels over, it is somehow made to turn in the opposite direction, like a canting keel, to increase the stability of the boat."

Would either of those concepts hand a team a huge advantage?

"If it is a significant amount [of change], yes," Farr said. But the first question is, is someone doing it? The second is, would it survive a serious protest?

"Certainly there seems to be a lot of hope around it and given the interpretations that have been done, someone has been thinking about trying to do something to make keels work in a better way than the objectives of the rule would have anticipated."