Leg 8 Strategic Review Part 1 – Going north

It came as the fleet approached the Exclusion Zone set off Cabo Frio, where the leaders took a more easterly position that paid out like a royal flush. It’s a long way to the finish line in Newport, Rhode Island though, and with almost 5,000nm still to run and lots of weather hazards to negotiate there is plenty of time for the rest of the fleet to come back into the mix.

South to north
I’m sure regular readers are weary of this explanation of climate zones, but just in case this is your first Strategic Review... then this analysis relies on the idea that the earth’s oceanic climate features distinct bands, lying horizontally and looping the globe, running out from the Equator to the Poles in a mirror image.

When the fleet races from south to north (or vice versa) as they are right now, then they will cross through several of these climate zones and the transitions from one type of weather or climate zone to the next becomes a critical feature of the strategic game.

On Leg 8 (full preview here), the fleet will be going from autumn in the southern hemisphere to spring in the north, and on the way passing by the St Helena High, through the trade winds, across the Doldrums, back into the trade winds, around the Bermuda (or Azores) High and finally into the Westerly Storm Track to finish in Newport. 

So the first hurdle right out of the blocks was the St Helena High (one of the Subtropical High Pressure Zones, a stable, semi-static area of High Pressure lying between 30 and 38 degrees) – complicated by the fact that a large part of Brazil pokes out into the route north ahead of the fleet from Itajai.

The set-up
In Image 1 we can see the situation just after the start on Sunday, at 23:00UTC on the 22nd April. An area of high pressure is situated to the south-east of Itajai, creating a north-easterly wind for the start – making it upwind all the way to the first corner at Cabo Frio.

There was a strong consensus on taking the port tack to head east / offshore, and if we move on to Image 2 from 19:00UTC on the 23rd April we can see why.

The breeze was fading fast along the coast of Brazil, and as the accounts of the first night at sea related, the fleet struggled to clear the coast into more stable breeze. At this point it was the two overall leaders, Dongfeng Race Team and MAPFRE that were making the running, but the pack were close behind with only six miles from first to seventh.

Opening move
It was Team Sun Hung Kai/Scallywag that was first to tack to starboard about 17:00UTC on the 23rd (just before Image 2) and the rest of the fleet followed soon after. This was the opening salvo in the strategic and tactical battle to be first around the corner at Cabo Frio, just to the east of Rio. The race officials have also set an exclusion zone (EZ) to keep the fleet out of the Campus Oil Field offshore from Cabo Frio.

Once they get past the Exclusion Zone the course frees up a little to make it more straight-line sailing north. So no one wanted to sail further offshore to get past the EZ than they had to – or at least, not without a really good reason.

The elements in play at this point included the south-running Brazil Current, which runs all the way down the coast from Recife to Buenos Aires. It swirls and eddies like the Gulf Stream and can present some nice opportunities for gains to those who are alert to it.

A balanced strategy
The teams also had to be wary of the movement of the high pressure, which was forecast to head east (as we can see in Image 1 and 2); driven that way by a storm in the Southern Ocean (out of picture).

The high also created a geographical wind shift – it was blowing from the north-east where they were, but from a more easterly direction to the east and north of the fleet. This easterly direction was better for starboard tack, and worse for port. All this created a set of competing benefits that had to be balanced in the final strategy.

Starting out by sailing east on port tack would guarantee that the boat was well-positioned to spend time on starboard in the profitable, more easterly breeze when it was reached. However, too much time on port tack would mean the boat sailing extra miles, and being further offshore than necessary to clear the EZ.

It was possible that being further offshore might also mean more wind and less current, both beneficial... but I suspect that everyone would chose less miles if they could. It seemed that any boat that could sail on port, then pick exactly the right moment to tack, set up on starboard and just skim past the EZ without any more maneuvers would probably come out ahead. Anyone spending too much time on port tack near the EZ was likely to lose.

The problem was picking the moment to tack to starboard without perfect foreknowledge of the wind direction and speed when they got to the EZ – but calls like this is the reason why the navigators get paid the big bucks.

Consensus breaks down
The consensus held until about 14:00UTC on the 24th April, as we can see in Image 3 from that time. The Scallywags had taken a hitch to the east to close the leverage (separation between the boats measured perpendicular to the course) with the group and they had all then tacked back to port more or less together. And there was still just six miles from the front to the back of the fleet, still led by Dongfeng Race Team and MAPFRE.

Just three hours later, as we can see in Image 4 from 17:00UTC on the 24th April the consensus had blown apart in the face of some serious cloud activity, as reported by the crews at the time. 

The outcome was a significant split, with MAPFRE (white), Team Brunel (yellow), Team AkzoNobel (purple) and the Scallywags (grey) favouring going north on starboard tack, and Turn the Tide on Plastic (light blue) and Vestas 11th Hour Racing (orange) favouring going east on port tack, with Dongfeng Race Team in the middle.

The wind flow arrows in the image show a nice uniform wind field that was not reflected by reality on the water. The table below the image shows the true picture, with directions from 38degrees to 72degrees and wind speeds from 7.8knots to 18.8knots... playing those clouds effectively, and getting the right role of the dice was going to be critical to the outcome.

It quickly started to go bad for the north-western group. They got a series of big wind shifts (called ‘headers’) that forced them to tack, only to get another header, forcing them to tack back. We can see their painful tracks in Image 5 from 20:30UTC on the 24th April, as they closed out the leverage with Dongfeng Race Team, the latter now leading that bunch by four miles.

The reckoning
Vestas 11th Hour Racing and Turn the Tide on Plastic were still out on the eastern wing of the main pack though, as everyone settled on starboard, headed for the EZ. No one was clearing the Zone though, and the reckoning was not long in coming as we can see in Image 6 from 03:00UTC this morning, 25th April. By this point the wind had stabilized a little, with the direction varying across the fleet from 72-96degrees, and the wind speed from 8.5 to 11.3knots.

If we compare these wind directions to those in Image 4 – the period when the eastern boats spent the extra time on port tack – we can see that back then, the wind direction range was 38-72degrees. This was a much better direction for port tack (taking the boat closer to the destination) than the 72-96degrees they had as they approached the EZ. So it made sense that the boats who stayed on port tack back then (ie were now approaching the EZ from further east) would make a gain.

Leverage closes out
This was exactly how it turned out. If we look at Image 7 from 05:00UTC on the 25th April, we can see that the north-western group had tacked, and the two easterly boats, Turn the Tide on Plastic and Vestas 11th Hour Racing had crossed comfortably in front of them.

If we bring it almost up to date at 09:00UTC this morning, 25th April in Image 8, everyone was more or less in a line on starboard tack. Now that the leverage had closed out, we can see that the gains for the two easterly boats were significant. Turn the Tide on Plastic and Vestas 11th Hour Racing were leading Dongfeng Race Team (at the front of the chasing pack) by 17 miles. A very nice job by the leaders, they picked the line into the EZ beautifully.

Next up
The benefits to being offshore might not be quite over. If we examine Image 8 closely, it doesn’t look as though the fleet are quite going to clear the north-east tip of the EZ, so more time on port may well be necessary. It might also be advisable, as the wind on that chart looks significantly lighter inshore, near to the EZ.

And coming right up to date (at the time of writing), let’s look at Image 9 with the Predicted Optimum Route calculated on the tracker from 13:00UTC on the 25th. It’s telling the fleet that they need to get a bit more east now, to benefit later. And as we see on this latest update, Turn the Tide on Plastic and maybe Dongfeng Race Team have already tacked to port. I think that we will see the rest of the fleet follow them soon.

The problem is very similar to the one that they have just dealt with – check out Image 10, also from 13:00UTC today, showing the Predicted Optimum Route north past the next corner at Recife. Once again there is less wind on the coast, and the wind will shift as they go north to free up their sailing angle. Picking the right moment to settle on starboard tack is once again critical.

If they go too far east now they will sail extra miles and lose. If they don’t go far enough east now they will end up doing time on port in a much less optimal wind speed and direction later on.

Recife
It’s going to take just over three days for this to play out at Recife. When they get there the “ancient book of race lore and wisdom” says to stay within 10 miles of the coast, or stand further off than 100 miles. Two things have to be balanced – the further offshore they sail, the stronger and steadier the breeze ought to be, but the more miles they have to travel.

A couple of times in recent races, boats have successfully rounded right on the beach and one of them was led by Bouwe Bekking in 2005-06 – so we might see a move here from Team Brunel.

Doldrums
The other aspect of this problem – distance offshore at Recife – is that it sets you up for the final Doldrums crossing in this race. If we look at Image 11, we can see the fleet’s projected position at 22:00UTC on the 28th April, in just over three days time. The fleet have just rounded Recife, and should be enjoying the south-east trade winds.

The Doldrums are a lot narrower to the west, and look non-existent on the coast of South America. If this forecast holds up it will pay to hug the coast around Recife and onwards to the north, making for a very quick Doldrums crossing through the weekend and early next week. I’ll be back then to review how that went for everyone, and see what the options are as they return to the northern hemisphere.