America's Cup: Ebb flow sees tide turn for Oracle

In Race 8, Team NZ had changed to bigger rudders and different daggerboards to help with stability in the bigger winds. Photo / Getty Images

The tide has turned.

No, no, no ... not that. That is to say, the actual tide has turned in San Francisco Bay this week and the racing in what the Americans call an "ebb" tide (an outgoing tide) has helped change the face of the Cup match over the last three races.

There are other considerations. Oracle have found something to help their boat speed. What, no one seems to know. Certainly it's nothing visible or structural.

What we are also seeing is a crack crew sailing their boat better, finding wind shifts better and making the right decisions over currents and tide.

In fact, Emirates Team NZ made changes to appendages.

In Race 8, they had changed to bigger rudders and different daggerboards to help with stability in the bigger winds. That change appeared to make them slower. They still had the bigger rudders on but changed their boards back yesterday.

They sailed flawlessly, the boat looked slick and stable and especially so in the winds and outgoing tide.

Their tacking, formerly a weak point, is much better now.

The ebb tide also means the start becomes the real point of pressure. Get in front and there are fewer passing lanes on an outgoing tide in San Francisco Bay than on an incoming tide.

In Race 9, the current was also running at a strong 2.2 knots; it was 1.6 knots in Race 10, which the Kiwis won.

That may help explain Oracle's improved performances.

Their boat just seems to handle going upwind at 30 knots-plus on a tide going in the same direction as their hulls.

The bad news is that the ebb tides will continue for the next few days.

The good news is that the effect of the ebb tide will lessen with each day. Also, the long range forecast for tomorrow is for winds which might exceed the limits - good for Team New Zealand.

After Friday, if the racing is still going, the Bay reverts to an incoming tide at race time - also suiting Team NZ better.

It means that the starts will become a particular focus for both teams and for Team NZ in particular if they are to stop Oracle from closing the gap more.

Once in front, it is harder for the trailing boat to pass - although you wouldn't have known that from Race 10 yesterday.

Win a couple more and not only the tide will be flowing out of San Francisco Bay.

So will the America's Cup.