Volvo Ocean Race - Saturday Ten Zulu Report
by Mark Chisnell on 25 Oct 2008
The sled runners have been polished, the whips are cracking, the huskies are barking themselves hoarse - the race south is on. And it looks worryingly like a re-run of Scott verses Amundsen for the British contingent on the Green Dragon, as the Scandinavian inspired Ericsson 4 starts to haul the mail.
A sail change aboard Ericsson 3 during Leg 1 of the Volvo Ocean Race 2008-09. Gustav Morin/Ericsson 3/
Volvo Ocean Race© http://www.volvooceanrace.com
At 10:10 ZULU (in accordance with the standing instructions for the weekends), the fleet had all stayed on the same tack (port) and pointed in the same direction (south) for the last 24 hours - to make things straightforward for your narrator on this beautiful Saturday morning at Volvo Ocean Race Towers.
The top four boats are still running as a pack (working that metaphor to death), with sixteen miles between them north to south, and half that distance east to west. And everyone was still going at right angles to the course to Cape Town, as discussed in yesterday’s TEN ZULU, and covered from various perspectives in this week’s Volvo Sailing Podcast.
What has changed is the wind (I guess asking that to stay the same for 24 hours would be an error of Canutian proportions). I’ve brought up a Data Centre graph of True Wind Direction (TWD) and True Wind Angle (TWA) for Green Dragon at the front of the fleet, Telefonica Blue in the middle and Team Russia at the back.
Two things jump out – the first is that as we expected in yesterday’s TEN ZULU, the wind is slowly rotating anti-clockwise, from south-east to east, as they sail south. Check out how much further to the east it is for Green Dragon (the most southerly boat) compared to Team Russia (the most northerly). And through the same period, the True Wind Speed (TWS) has eased back from the high to mid-teens.
The second thing is that no matter where they are in the fleet, the skippers have held their course south, allowing the wind to move aft, changing trim and sails to the widening True Wind Angle (TWA), rather than altering course and sailing towards the finish.
Gain southerly latitude - no matter what
We dealt with the big picture reasons for this strategy in yesterday’s TEN ZULU, and we’ll look at it again in more detail in a moment, but it’s worth stressing that in the race south, it’s not about the Distance to Leader (DTL in the Data Centre). We’ve had 24 hours in which the leaderboard tells you almost nothing about who’s winning and losing.
I’ve pulled up a second graph from the Data Centre that helps to make the point – but carries a technical content warning. Boat speed does what it says on the tin, and it’s in the low to high teens for the three boats that I’ve picked – again, Green Dragon at the front of the fleet, Telefonica Blue in the middle and Team Russia at the back.
But VMC is the Velocity Made to the Course – the speed that the boats are travelling towards Cape Town (it’s calculated using trigonometry: cosine of the boat speed and the angle the boat is sailing to the desired course). And VMC is dribbling along between three and six knots. If any of the skippers wanted to improve their VMC and shoot up the leaderboard they could, simply by pulling in the sails and narrowing the angle between their Heading (HDG) and the course to the finish (BRG_WPT in the Data Centre) - but if anything, they’ve done the opposite.
Yesterday afternoon, Green Dragon put her bow down. The Dragon got across in front of Ericsson 4, to protect the route south. By 16:00 she was both the most southerly and the most westerly boat. But like Captain Scott’s men, versus the sleds and huskies of Roald Amundsen, the Dragon hadn’t got the pace.
At 10:00 ZULU this morning, while Green Dragon was still the most westerly boat in the top group, Ericsson had overhauled her and was further south. All the boats in the leading pack have been running at close quarters and will have a surveillance operation going that the CIA would be proud of – radar lock, night vision binoculars – checking how their speeds compare for the wind angle, their trim and their sail selection.
Kenny Read made it clear in this morning’s email that they are all learning plenty about how their boats and sail inventories stack up against the opposition. ‘They [Telefonica Black] were quick jib reaching so we got another chance to go to school on our trim and learned a ton.’ But Ian Walker and his team aboard the Green Dragon are less happy about what they’ve seen.
It’s all about having the right sail for the True Wind Angle that they want to sail, in the True Wind Speed that they have got. And right now, Ericsson 4 clearly has the better of it.
So much for the boat speed battle - time to get down to the harsh realties of the race south. Race forecaster, Jennifer Lilly, explains the situation in this morning’s forecast. Essentially, the South Atlantic High is centred south of Cape Town, with a huge ridge of light air extending towards Rio de Janeiro. The fleet has to cross this ridge of light air, probably tomorrow, and that means another compression of the squeeze box.
Looking for the low
What’s going to uncompress them is a low pressure system that will come spinning off the Brazilian coast in a couple of days time – it’s headed for Africa, and it’s a Collect £200 and Pass Go card for anyone that catches a ride on it.
There’s plenty coming off the boats about the situation. Aboard Ericsson 4, Media Man, Guy Salter speculated, ‘All of us are headed in an almost south-west direction down the coast of Brazil and await lighter winds before we turn hard left and head to Cape Town, riding a low pressure to get us there very quickly. It probably won’t be long until some of the teams play their StealthPlay – to try and hide the time they break for Africa.’
The Predicted Routes in the Race Viewer show that the fleet have some way to go before they can do the handbrake turn east. And the effect of the low pressure can be clearly seen in the isochrones (click on a boat name in the leaderboard). I’ve switched them on for the leader and the last boat, and the image is here).
And (with enormous relief, I can finally type…) we now have the numbers to go with the Predicted Routes. If you look in the Data Centre Tables, you’ll find a whole new Predicted Table, based on the same weather routing calculations we’re doing to calculate the Predicted Routes (there is a full explanation of how all this works in the FAQs on the Welcome Tab in the Data Centre).
The numbers make for scary reading for Team Russia. Nothing much changes for the next 24 hours (compare the DTL at 10:00 ZULU today, with the +1 Day Predicted DTL (+1DPDTL)), then as the leaders hit the light air of the ridge later tomorrow, the fleet starts to compress. Team Russia could get to within 37 miles of the lead in three days time (that’s the number for the +3 Day Predicted DTL (+3DPDTL)). But in five days time (the +5 Day Predicted DTL (+5DPDTL)), the mileage blows out to 464. The weather routing reckons that Team Russia will miss the low pressure, and the ride east.
No wonder the navigator aboard Team Russia, Wouter Verbraak, is focused on it, writing yesterday, ‘I can guarantee you right now all the navigators are homing in on a low pressure system developing off the coast of Rio in three days. This low has the potential to give us a great ride towards Cape Town, but careful positioning will be crucial. Too far east, and you run the risk of getting caught in the High with the light winds. Too far west and you might fall off the train early.’ Let’s hope Wouter threads the needle and doesn’t miss the bus.
Meanwhile, for the leading pack there’s nothing in it. The Predictions give a slight advantage in five days time to the boats that are currently the furthest south – but no more than the handful of miles that are currently separating them. Sails and horsepower are going to make a bigger difference, and as the race south and onto Cape Town now includes every wind angle from close reaching to broad running, and
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