It was the day Oracle Team USA opened the door to their greatest secret - the performance of their two AC72 catamarans.
But even though Oracle made available all the electronic data previously denied to the challengers, there were few definitive conclusions reached yesterday.
"I've got no idea," said Emirates Team NZ boss Grant Dalton last night. "It's too early to tell; we just started feeding the info in two seconds ago - and we have to get the programmers to check it out."
The likelihood is that little will be gained, even after Oracle's surprise - but welcome - gesture allowing telemetry data to be picked up by the challengers. The issue had been traversed with the jury and Oracle's win there (effectively maintaining that their two-boat racing on the course was just training rather than racing) was a significant victory.
Oracle were allowed access to the data beamed back from the challengers' boats. But when Oracle's two boats trained on the race course, they did not have to send the same telemetry to the challengers. That meant Oracle was the only competitor to know the relative speeds, strengths and weaknesses of all the competing boats.
With it, they could tell just how fast Emirates Team New Zealand are going and what they have to do to beat them.
Until yesterday - although comparatively light airs may have thwarted the watchers from picking up much. Both Oracle yachts seemed quick but the relatively light winds meant foiling was not easy and, without that, comparisons may be muted.
Some preliminary observations were possible: Boat 1 (skippered by Sir Ben Ainslie) may be slower downwind but might be a touch faster upwind. However, it still has non-compliant rudders, suggesting that the change to compliant rudders may affect its speed.
Boat 2 (skippered by Jimmy Spithill) won the start and looked to have a faster package overall though it is still difficult to tell without foiling. It has compliant rudders and is expected to be the yacht Oracle field in the Cup match.
"It was a difficult day," said Ainslie. "It was a bit puffy and that sort of wind produces the hardest conditions for foiling. These boats are actually easier to sail if they are going quicker."
Spithill said he felt the New Zealand team were still ahead when it came to foiling.
"I think they are still ahead in that department," he said. "You know, we are not hiding from our weaknesses - we still have work to do in that area."