More signs have emerged that Emirates Team New Zealand's America's Cup strategy is the right one with the temporary disappearance of fellow challenger Artemis from San Francisco waters.
Trial racing with Cup holders Oracle proved that a slower Artemis have erred in going down the non-foiling path. ETNZ, Oracle and Luna Rossa have all embraced the design strategy that sees the giant 72-foot catamarans hoisting themselves off the water, reducing drag by lifting their hulls clear with only the foils connecting boat to sea.
Team New Zealand have been undisputed leaders in foiling, though recent pictures from the US suggest Oracle is fast coming up the scale. Luna Rossa also have good foiling ability, courtesy of their design-sharing arrangement with Team NZ.
But Artemis' design team won the foiling or no foiling debate, arguing the drag created by the design needed to foil would be more of a penalty than the extra lift and speed generated.
They are thinking differently now. In an interview published on the website Scuttlebutt, Artemis team boss Paul Cayard said: "... it is fair to say we got it wrong. So now we are reacting. Our team has come together and is fully committed to tackling this issue full on."
They are doing that by building foiling capability into their second AC72. The new yacht is being built in Sweden and will be ready for sailing by the end of May (the challengers' regatta begins in July).
"Some of the aspects of the L boards [the foils Team NZ and Oracle are using] that we will need to discover is their impact on manoeuvreability and downspeed acceleration," said Cayard. "This had been a concern of ours, but our experience training with Oracle Team USA is that their L boards didn't seem to be much of a hindrance, if any. This factored in our decision to make the modifications to our boats."
Artemis will modify their boat in the next 3-4 weeks after pulling it off the water but it will only have a part-foiling capability. The new boat will be able to foil fully - but the Swedish syndicate still face problems.
Time off the water is one. They seem liable to be the syndicate with the least number of hours on the water by the time the regatta starts and, though they are kitting out a 45-foot AC45 catamaran for the crew to train on, that is nowhere near as useful as time on board an AC72.
Cayard said: "Our second boat will now have a fully foiling package. The boat was already designed with greater foiling lift, and was very close to having full foiling ability. We called it skimming, wherein it was expected to lift roughly 80 per cent of the hull's displacement, meaning the hull is barely touching the water. But now that boat will have full foiling ability though we will retain both full foil and skimming options to test."
However, with the build already under way, it depends just how much Artemis's Boat 2 had embraced the foiling strategy. The whole yacht has to be designed around foiling, including factors like hull shape and the platform of the boat plus the complex mechanisms and structures which go into lifting tonnes of yacht off the water at 30-40 knots or more.
Changing direction could mean further delays and less time testing on the water. It's the latest reverse for a syndicate which has had some bad luck and internal ructions - a damaged wingsail set their launch back months. Then the platform was damaged during load testing.
Former skipper Terry Hutchinson was "let go" in December, with the team bringing in French multi-hull expert Loick Peyron and Australia's hotshot 2012 Olympics sailor, Nathan Outteridge.
But one of Hutchinson's final quotes - words to the effect that it would be a long summer for Artemis if foiling was going to work - might yet be proved right.