Leg 7 Strategic Review Part 2 - Playing the shifts

It’s been a big week for the Volvo Ocean Race fleet, racing through Point Nemo and tested by some proper Southern Ocean conditions

March 26, 2018 15:25 UTC

Text by Mark Chisnell

It’s been a big week for the Volvo Ocean Race fleet, racing through Point Nemo and tested by some proper Southern Ocean conditions. We’ve seen lead changes, breakdowns and crashes – but it’s reassuring to know that the current leader is where they are because of something as core to sailboat racing as getting a wind shift right.

Climate Zone-ology
It’s time for my standard intro to the idea of racing through climate zones; the notion 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.

Leg 7 (click here for the full preview) travels west to east, so we only have to worry about two climates zones; the start and finish which are both in the stable, semi-static areas of Subtropical High Pressure, and between them the Westerly Storm Track. This is where storms and low pressure systems swirl west-to-east around the globe, circulating the Antarctic with nothing but a handful of tiny islands to slow them down.

If you’ve been reading any of the recent reports from the boats then you won’t be surprised to learn that the fleet are in the thick of the storm track right now; and they will be there until they’ve turned north and escaped Cape Horn by a few hundred miles.

Round the high
We left the fleet at the end of the previous Strategic Review on Tuesday 20th March, dropping south like a stone from the East Cape of New Zealand as we see in Image 1 from 12:30UTC on that date. The dominant feature in the racing was the big and quite powerful high pressure ahead and just to the east of the fleet’s track.

©Geovoile - Image 1 (Click for larger image)

The straight line of their course was already becoming a curve as they shifted their position relative to the centre of the high pressure. The easterly wind had become a north-easterly, and we predicted that it would steadily shift to a northerly direction as they continued south.

The goal was to track around the bottom of the high pressure system; far enough north to stay above the ice exclusion zone (marked by a faint red area on the tracker), but far enough south to avoid the light winds in the centre of the high pressure (marked by the blue colour).

Lane choices
The fleet had picked a lane on their approach to this problem, with an east-to-west spread across the fleet of seven miles. Turn the Tide on Plastic were out to the west with Dongfeng, and Vestas 11th Hour Racing to the east with MAPFRE. So much for the set-up, let’s see how it played out.

The first thing that happened was probably predictable; MAPFRE (white) swopped sides to stay close to Dongfeng Race Team (red) as we see in Image 2 from 20:00UTC on the 20th March.

©Geovoile - Image 2 (Click for larger image)

This pair were now third and fourth respectively, with Vestas 11th Hour Racing (orange) leading from Team AkzoNobel (purple). Those two were taking the inside or northerly track, with Team Brunel (yellow) following their line in fifth place, nine miles behind the leader.

Then we had Turn the Tide on Plastic in 6th with a 12 mile deficit to the leader, and Team Sun Hung Kai / Scallywag bringing up the back in seventh, just over 15 miles behind Vestas 11th Hour Racing.

Turning left
The left-hand turn indicators stayed on, and by Image 3 at 13:00UTC on the 21st March the fleet were sailing east in a solid 20 knot north-westerly wind. There had been a few lane changes in that time; Vestas 11th Hour Racing had moved to join MAPFRE in the south and had given up the lead in doing so.

©Geovoile - Image 3 (Click for larger image)

They had been replaced at the top of the leaderboard by Team AkzoNobel who were benefitting from holding steady on their northerly strategy, and had been joined by Dongfeng Race Team – escaping the clutches of MAPFRE at least temporarily.

Team Brunel and Turn the Tide on Plastic were also in that group about ten miles north of Vestas 11th Hour Racing and MAPFRE. Always the outlier, the Scallywags were taking a route all on their own another ten miles north of Turn the Tide on Plastic.

Convergence
Ahead of them, to the right in Image 3, we can see the blue colour of the light winds at the centre of the high. This light wind met the faded red of the ice exclusion zone – this was the needle that they had to thread. The good news was that in the bigger picture, a new low pressure system and front was sweeping in from the south-west and was predicted to move the high out of the way for them.

If we go forward to Image 4 from 03:30UTC on the 22nd March the fleet (well, apart from the Scallywags ploughing their lonely furrow to the north) have converged on the ice exclusion zone. And the northern group had won this one, with Team AkzoNobel coming out in front to grab an eight mile lead from MAPFRE.

©Geovoile - Image 4 (Click for larger image)

I think this was down to the fact that the high was pushed out of their way and they were never lacking wind. They still had over 20 knots of north-westerly, with the front racing up from behind. The way this played out, the boats on the southern route sailed extra miles to stay in the breeze and didn’t need to – so a win to Team AkzoNobel.

Caught by the front
It didn’t take long for the front to catch them, if we go forward to Image 5 from 01:30UTC from the 23rd March we can see the fleet now in the south-westerly breeze behind the front.

©Geovoile - Image 5 (Click for larger image)

MAPFRE had gybed first and were clearly keen to stay south near the ice exclusion zone where the wind was strongest. It was a move that had got them back into the lead. There was no shortage of power though, everyone registering up to 30 knots as the front went through. It took a couple of hours for the shift to the south-west to complete and for everyone to get onto starboard. After that, they were sailing a course that converged slowly onto the ice exclusion zone, and so the gybe-fest began.

Walking the line
What followed was some brutal physical sailing in tough conditions with no one able to get much of a grip on the lead as they traded gybes along the ice line. The next wind shift was back to the west as the low pressure continued to move ahead of them, as we can see in Image 6 from 16:00UTC on the 23rd March. The whole fleet now has 20-30 knots of westerly wind, with MAPFRE still the most southerly boat and still holding a narrow lead.

©Geovoile - Image 6 (Click for larger image)

Options open
The options now started to open, as we can see in Image 7 from 17:00UTC on the 24th March. A split has started; MAPFRE still led the race from the south. They were right back on the ice line with Turn the Tide on Plastic eight miles behind them, and Scallywag 140 miles back after breaking a runner block. While Team Brunel now led a northerly pack consisting of Team AkzoNobel, Vestas 11th Hour Racing and Dongfeng Race Team.

©Geovoile - Image 7 (Click for larger image)

The interesting part of this image was that the wind flow was not uniform. The breeze for the southern group was back in the south-west, while the northern group had a westerly wind. We can see this in both the wind flow in the image and in the reported wind directions in the table below. A westerly wind will benefit a boat on port gybe, while a south-westerly wind will benefit a boat on starboard gybe – remember that, it’s going to be important.

The shift goes thro’
If we now jump forward to Image 8 from the 25th March at 03:00UTC we can see that the northern group and in particular Team Brunel have been the winners. The reason goes back to the moment that I have circled in black on that image (be aware that the weather and wind shown is from 25th March, not the moment circled which is about 11:00UTC on the 24th March).

©Geovoile - Image 8 (Click for larger image)

At this point, both boats had a westerly breeze, and Team Brunel gybed to port to take advantage of it. In contrast, anxious to stay close to the ice line, MAPFRE had stayed on starboard and committed to the south. They got back into the south-westerly a few hours later, and then gybed back and forth in this breeze along the ice line. All the time they spent on port in the south-westerly, they were losing to a boat that was spending that time on port in the westerly. And that boat was Team Brunel.

It’s around this time that MAPFRE did their mast damage, so we don’t know the extent to which their tactics were forced on them by trying to protect or repair their rig – so none of this may have been willing.

It doesn’t alter the outcome, which was that eventually Team Brunel also gybed to starboard while still in the westerly. They got into the south-westerly not long after (at the point circled in yellow) but now they were so far north of the ice line that they were able to stay on that starboard gybe and just keep going – on the right gybe for the wind shift, in comparison to the boats to the south. Those boats were forced by the proximity of the ice line to keep spending time on port in the south-westerly, on the wrong gybe for the wind shift.

And so, when they came together as we see in Image 8, Team Brunel had punched into a 20 mile lead. Sweet. They avoided doing unnecessary distance on the wrong gybe in a bad shift just to avoid the ice boundary. They also did half the number of gybes. Together it was a gain, despite sailing in a little less breeze. The strategy that worked in Leg 3 didn’t work in Leg 7 – that’s sailboat racing for you.

Rinse, repeat
Fast sailing followed, as the ice exclusion zone line moved south and made the race track a bit wider, allowing everyone to pour it on in the south-westerly. The next front was already in-bound though, bringing another shift to the west. We can see this underway in Image 9 from 02:00UTC this morning, the 26th March.

The track of the leading pack has slowly curved to the south-east as the wind has shifted from south-west to west. If the ice line hadn’t moved south they would have been forced to gybe (like Scallywag). This was something they didn’t want to do until they got into the westerly or even north-westerly wind that was on its way with the front that was slowly overtaking them.

If we now bring it more or less up to date with Image 10 from 09:00UTC today, 26th March we can see that the front has caught the main pack, shifted their wind into the north-west and they have gybed more or less in unison. Everyone is pointed at Cape Horn with the hammer down in survival conditions. When the table is reporting wind speeds of 35-45 knots you know it’s a lot more in some of the gusts.

Looking ahead
The front and the low pressure centred to their south will slowly move ahead, and the wind will once again go back to the west behind it. If we have a look at Image 11 from 15:00 this afternoon, 26th March, we can see the predicted best route to Cape Horn in the dashed lines. The optimum route has the fleet gybing to starboard when the westerly wind reaches them, so the main pack will go before Team Brunel, creating some separation.

They will all head south-east on starboard until they hit the ice exclusion zone once again and then have to gybe to port. This sets them up for a long, fast leg that will take them all the way to South America, chasing the front the whole way.

Closing on the coast
It gets strategically interesting again when they start to close on the coast, and the front hits the mountains of Patagonia and Tierra del Fuego. This will compress the breeze and shift it to the north-west.

Team Brunel at the Horn
The wind shift will help Team Brunel get down to Cape Horn, but everyone else will be left gybing along the coast of Chile. The leader should go around the Horn at about midnight UTC on the 28th March (Wednesday) as we can see in Image 12, with the rest of the fleet following about three hours later. It should be a bonus point to Team Brunel for rounding the Horn first, and all thanks to that nice move on one wind shift.

Falklands question?
There is always plenty of discussion about whether the boats should route inside or outside the Falkland Islands as they go north. This year, it looks like inside will work fine for the lead pack as they head north in the westerly winds escaping through the mountains of South America and into the Atlantic – as we see in Image 13 with the predicted weather and boat positions from 14:30 on the 29th March.

After that it gets tricky again, as a bubble of high pressure forms in the lee of those same mountains and starts to move very quickly across in front of them. By the time of Image 14, 09:00UTC on the 30th they will be going upwind in the northerly breeze to the west of the centre of the high pressure.

Ch-ch-ch-changes
It doesn’t appear that this is going to create any kind of passing lane though, so I’d expect Team Brunel to still be leading (barring accident or breakdown) at the weekend. After that, the changes come thick and fast; another low pressure switching their breeze back to southerly before they have to negotiate a zone of high pressure and light winds. I’ll be back at the end of the week to see how this might play out through to the finish in Brazil.