12:36 PM Wed 17 Dec 2008 GMT
In the Volvo Ocean Race, it's all about the leverage this morning, almost 100 miles in the ultimate north-south divide between the leader, Telefonica Blue, and the chasing pack.
The tracks on the Race Viewer look more like the windward leg of an Olympic medal event, than a long-distance, blue water passage race - each team tacking with every shift of the wind that might give them an advantage. But aboard Telefonica Blue, skipper, Bouwe Bekking seems to be interpreting 'advantage' a little differently to everyone else.
By 10:00 ZULU this morning, the fleet had seriously shuffled the deck through 24 hours of beating upwind into a shifty breeze that has blown from a True Wind Direction (TWD in the Data Centre) varying from north to east, with a True Wind Speed (TWS) that has generally built from the eight to 11 knots we had yesterday morning, to a more variable velocity that has got up into the high-teens.
Staking their claim in the south, but more than a little nervous about it, was Telefonica Blue (remember, they got there by dodging out of the current). They had finally tacked to starboard to head north-east in a great easterly slant of breeze just after 05:00 ZULU this morning. At 10:00 ZULU most of the fleet were on starboard tack with them, and next up along the north-south line were Ericsson 3 (who have done a great job of getting into the front row), then Green Dragon, Telefonica Black, Ericsson 4 and finally PUMA on the northern outpost. The second row constituted Team Russia and Delta Lloyd, both slightly north of the middle of the main pack.
The current situation started to play out after the 16:00 ZULU Position Report yesterday afternoon. Until then, the whole fleet had been enjoying a pleasant north-easterly TWD, which on port tack, was allowing them to point pretty much at the scoring gate (a line running south to north from Pulau We, marked on the Race Viewer and due east of the fleet).
How are the wind shifts going to affect the rest of the leg?
Another technical content warning here, sorry. but we need to look at how the wind shifts are going to affect the rest of this leg, as it's the whole winning and losing thing...
So, if we assume that the north-easterly monsoon wind direction is the average wind that the fleet will see between here and the scoring gate, then with the boats sailing upwind at a True Wind Angle (TWA in the Data Centre) of something like 40-45 degrees, they can sail directly towards the scoring gate on port tack.
Now, if the wind shifts and blows from a TWD of east, they will no longer be able to sail at the scoring gate on port tack, sailing south-east instead. That's a good moment to tack onto starboard, and sail north-east. That's despite the fact that whether you're sailing south-east or north-east, you are going east at the same speed (the VMC - see below) towards the gate. The reason to tack is that going north-east is taking you into the stronger wind that lies to the north.
(Check out the variable VMC (Velocity Made to Course) in the Data Centre. An average calculation of Boat Speed (BS) multiplied by the cosine of the angle between the course to the waypoint (BRG_WPT) and the boat's actual heading (HDG). It's a measure of the speed at which the boat has travelled in the direction of the next waypoint - measured in knots. The next waypoint in this instance is on the island of Pulau We.)
In contrast, if the wind shifts and blows from the north, then everyone can simply let the sails out a little bit on port tack, and keep sailing east towards the scoring gate at a wider, and faster TWA.
So, the situation yesterday morning was that the fleet was looking for any veering wind shift - taking the TWD clockwise from the north-east towards the east - as an opportunity to tack to starboard and get north. Of the boats that we've heard from, both Jules Salter, on Ericsson 4, had renewed his commitment to playing the north in this clip, as did Fernando Echavarri, skipper of Telefonica Black, in yesterday's audio with Amanda Blackley.
But the devil, as always, is in the details - how badly do you want to go north? Because if the wind only shifts about half-way from north-east to the east (to a TWD of 70, for instance), you can tack to starboard and get north, but your VMC will be lower than someone who stays on port, and continues to sail at the scoring gate.
(And yes, I know, it's simpler when they are reaching. believe me, I've got a bad case of man flu and I didn't need it to be this complicated either.).
Last night, we found out how badly they all wanted to go north. The wind started to veer, shifting clock-wise from north-east towards the east, and slowly, one by one, everyone decided that it was time to get onto starboard tack and head into the stronger breeze.
For the leading pack, Ken Read and PUMA were the first to go at about 17:30 ZULU, followed half an hour later by Ericsson 4. Then, 15 minutes later, Echavarri was as good as his word and Telefonica Black tacked to starboard, while - already the most southerly boat - Ian Walker and Green Dragon waited until almost 20:00 ZULU before they tacked. Most of them tacked on a TWD of around 80 degrees - giving up a little to get north, but not much. The reason that Ian Walker waited so long was that he never really got that wind shift, and eventually tacked on about 60 TWD.
And, as we've already seen, Bouwe Bekking held out even longer. They never saw the early shift to the east either, and tried to tack a couple of times with a TWD of around 60 - 70 - but each time they went back to port to wait for the big one. And each time they did so, the leverage opened a little more between them and the boats to the north . time to be afraid, very afraid.
All of this can be seen in today's graph, which shows how Telefonica Blue's lead grew overnight, as they stayed on the VMC-favoured port tack. but check out how much lower their TWS has been on average - that's the pain, to be paid for the gain.
It was about now that Bekking sent this email, offering his castle for a checkmate position, while doing calming breathing exercises, as well he might. (there's a good yoga one here, although you do end up with snotty fingers - and let's hope it's not a bloody nose as well). They finally got the wind shift they needed just after 05:00 ZULU this morning, when they tacked to starboard in a wind direction of due east, with everyone to leeward and miles behind - for now.
So how is this going to play out? No surprises that it all depends on how much easterly breeze we get before the scoring gate, in contrast to how much north-easterly. Telefonica Blue are going to look great every time the wind is blowing from the east, and terrible every time it blows from north of north-east - prepare yourselves for a rollercoaster ride on the Leaderboard.
The latest analysis from Race Forecaster, Jennifer Lilly, predicted the period of easterly breeze that the fleet now have - but she wasn't expecting it to last long. And it will be followed by a period of north-easterly TWD - at that point we can expect everyone to tack back, and head towards the scoring gate on port. The advantage will then be held by everyone in the north who should be in more wind, and able to sail a wider, faster TWA to the Straits. Will that new advantage be enough to overcome the lead that Telefonica Blue have already built up?
Looking at the Race Viewer image, once again showing the Predicted Routes (the faint wiggly lines running west to east from the yacht's current position), the Isochrones (the curved vertical lines) and the weather through to 07:00 tomorrow morning, we can see that Telefonica Blue (blue line) is holding her lead, despite the predicted wind shift to the north-east.
But . remember how flaky the weather forecast has been in this area, and don't forget the increasing number of clouds and squalls that the fleet are about to sail into - the green and yellow splodges on the weather map that is shown with Jennifer's analysis. There's a long way to go, and a lot of it is still in the hands of the weather and the thunder gods (nothing if not eclectic - yesterday M.C. Escher, today Marvel comics.)
by Mark Chisnell
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