Today a cold front is headed towards San Francisco, It certainly looked this morning that is was moving faster than forecast. I do not believe that any races will be sailed today. The following is an interesting explanation as to why the wind limits are in place.
Today
UPDATE: 1130 hours
Races 13 and 14 are on the slate today, scheduled to start at 1315 and 1415 respectively. With a cold front approaching the Northern California region today’s weather is a bit unstable. The front was forecast to increase winds tonight, but that build has started earlier than expected.
The original forecast called for winds of 10 to 15 knots with clouds increasing throughout the afternoon. But Regatta Director Iain Murray says the wind is already building.
“It’s getting windier than that on racecourse. Already it’s blowing 15-18 knots at Anita Rock, in the sheltered part of San Francisco Bay, and more than that on Treasure Island,” said Murray.
High tide in San Francisco is scheduled for 1249, which means there’ll be a slight increase in the base 23-knot wind limit for Race 13 (23.3 knots) and then a decrease for Race 14 (21.3 knots).
“Were expecting the breeze to build all day and be very windy tonight,” Murray said. “We were confident of getting some races in on the earlier forecast, but the reality of what we see out there on the racecourse, it is windier – and this is pre-frontal as front comes through – we’ll have to play it by ear.”
As for the teams, ORACLE TEAM USA was issued another certificate again this morning, its 13th in 13 races. A new certificate has to be issued for the slightest of changes, such as moving the rudderhead 10 millimeters, so it’s not surprising that the defender has constantly changed its boat in the search for the perfect setup. Today, the most notable change was the addition of the bowsprit, perhaps due to the original light-wind forecast.
Emirates Team New Zealand will have port tack in the Race 13 pre-start and ORACLE TEAM USA will be on port in Race 14.
FROM SAILING ANARCHY:
I cracked the books a bit and ran some numbers yesterday. I think I have a good reason for the wind speed limit being set where it is. Wow was I wrong. The boats ended up being faster than they predicted, i.e. the designs were too good. 
This put them dangerously close to putting the foils into cavitation speeds (~50+) that could have lead to real control problems.
Basically they want to limit boat speed to under 50 knots to stay safely out of foil cavitation speeds. The boats can sail over 2x wind speed and in some ranges are close to or at 3x wind speed the TWS needed to keep them below 50 knots is in the 22-24 knot range.
The wind limit for safety was not a reaction to the Artemis disaster as I assumed incorrectly. I had assumed the limit was for structural concerns not an unforeseen design challenge.
If they want higher wind speed limits they have to lose the foiling to remove the “50 knot barrier” or they can lose the wing to reduce the top speed of the boats to under 3x wind speed.
If they want to keep the full foiling and hard wings they are stuck with a low wind speed limit until they solve the cavitation issue. Sort of ironic that the faster the boat is relative to wind speed the lower the safe wind speed becomes. If indeed the wind limit was lowered due to concerns about foil cavitation then they got it right and the engineering math supports it.
It is not about being pansies, or poor design, or reaction to the Artemis disaster. It is about unforeseen design success.
Stop bitching about the boats being to fragile to sail in 30+
Start celebrating that they are too fast to sail in over 25.
I’m surprised that none of the SA techies from AC33 had done the figures to reach this conclusion.
Cheers,
