Tuesday, 29 May 2012

Complex Atlantic crossing as boats seek best winds

 Thrane & Thrane FleetBroadband onboard Abu Dhabi which
 will help the crew choose the best tactics for crossing The Atlantic 
 Photo: Nick Dana/Volvo Ocean Racing
When you cross oceans with the prevailing winds, the goal is to hook into a fast running weather system and sail with it as long as you can - a little like catching a bus. 

Crossing the north Atlantic Ocean from West to East is an ideal opportunity for this to work well for the fleet.

Now they are away from complications like gulf streams and tropical storm Alberto, the navigators have tried to line their race boats up with the fastest systems going east.

Leeway diminishes
The next trick is to play-off how much north or south you should be to benefit from the best winds that carry the full force of the front.

When you're thousands of miles away from the finish line, you can sail further to line up perfectly.

But as you get closer, there is less leeway before you find yourself sailing more distance for less overall gain.

This is exactly what’s facing the fleet now.

Elastic band
Abu Dhabi Ocean racing made a 90 nm gain when they lined up perfectly with a system.
Now the next system is coming in from the west and sweeping the back of the fleet up to meet the front.

It's like the fleet is connected with a giant elastic band, as the lead is pulled out and then caught up.

There are a number of tactical considerations being made by Puma’s Media Crew Member, Amory Ross, as he considers the options for the fleet.

Stronger winds
"It is exciting to think that after sailing 3,500 miles across the Atlantic Ocean, this leg could well restart with just 100 miles to go, and with Groupama, Telefónica, and now Abu Dhabi squandering breakaway leads due to unfavourable weather, the thrills look set to continue until the end," he said.

"Once over 90 miles to our east, Abu Dhabi is now just 30 away, and as we’ve brought the stronger winds to them, the guys to our southwest are doing the same to us.

"At some point we could all line up south to north. Fortunately, these exciting 15 to 25 knots of wind are forecasted to last at least another day, giving us a final chance to gain some leverage to the north.

Complicated tactics
"When the front begins to overtake us it should again favour the boats further north while lifting and lightening the southern pack," he added.

Making the tactics all the more complicated is the proximity of the trough to the finish, Amory explained.

Because there are only about 100 miles to sail after punching through, there’s just not enough ‘runway’ to make up for miles spent diverting far north or south of Rhumb line in search of an optimal point of transit.

"In other words, if this ridge were mid-Atlantic, you could aim and sail for a narrow band 100 miles north of where you were — no problem — but to do that for this ridge would mean you would essentially double your distance to the finish, having to sail an additional 100 miles on the other side too," said Amory.

"So we're all going to be forced to stay relatively conservative in our approach and execution, staying closer to the actual course to Lisbon than what might otherwise be most advantageous."

No comments:

Post a Comment