Cup Experience

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AC72 Design – Artemis wing1 and 2 side by side

 

AC72 wing sail 1 & 2 for 2013 America's Cup in San Francisco AC72 wing sail 1 & 2 for 2013 America’s Cup in San Francisco Wings 1 & 2 side by side. Artemis AC72 Artemis Racing has put wing 2 in the boat recently and will be sailing with it soon. Their AC72 design team has made big changes from wing 1: The new wing looks to have only 2 elements (meaning only 1 slot between elements) and the flaps are much wider. In “tech-speak” this means the ratio of the chords of the 2 elements has changed dramatically. (Look here for Wikipedia’s discussion of chords in wings.) The AC72 design battle continues, in the build up to the 2013 America’s Cup in San Francisco!

 

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AC72 design Artemis ergonomics

Artemis has a central station for grinders and trimmers.
Artemis has 2 grinding pedestals on each hull and 2 in their central station for a total of 6. USA 17, New Zealand and Luna Rossa each has 4 grinding pedastals on each hull for a total of 8. Crew choreography will be fundamentally different on Artemis.

See more about ergonomics in AC72 designs here.

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Recovering the lost € 40,000 camera?

 

Luna-Rossa-launched-Naples-Day-1

Luna-Rossa-launched-Naples-Day-1 (1)
Luna Rossa launched – Naples Day 1

Luna Rossa launched – Naples Day 1

Did you see Matthew Sheahan‘s Yachting Worldblog post about the boat carnage in Naples on Day 1 of Racing (Wed 11 April 2012)?  Matthew writes:

The first focus of attention was on Artemis’ wing which, after hitting the water trailing edge first in their spectacular nose dive capsize had been wrecked beyond repair, at least within the timeframe available during this regatta.

He then quotes ACRM CEO and regatta director Iain Murray:

“It will take around 200 hours to fix the wing,” said Murray, “so I guess that’s around 20,000 Euros.”

But as the assembled journalists started to suck their teeth in surprise, Murray was quick to put the cost in perspective.

“To be honest we’re more concerned about the onboard camera that fell off their bowsprit, that’s worth 40,000 Euros.“It’s down there somewhere and if anybody knows where it is we’d like to have it back,” he joked.

Well, Iain, maybe I can help. Your GPS data tells you exactly where the boats were.  I can tell you exactly when the camera fell off:   While watching the race, I saw it fall off, well before the capsize.  Watch this video:

http://youtu.be/8G3kN44AGZY?t=31m50s

31:50  Helicopter shot of Artemis approaching the left hand mark boat at the leeward gate.

31:56   Closeup of Artemis approaching the gate, 44 seconds after Spithill rounded.

32:02 The diagonal cable from the starboard hull to the bowsprit takes two shocks as the strut below the bowsprit hits waves and the camera falls off the bowsprit!

Too bad I didn’t find the exact moment in the replay until today – the weather is so rough today that racing has been cancelled and the waves probably stirred up the bottom and moved the sunken treasure of the €40,000 camera!

 

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Artemis wing details – how many elements & slots?

 

And why are “elements” and “slots” important?

Since we got the first photos of Artemis’s AC72 wing there have been many questions about the wing’s configuration – how many elements? How many slots?  (For the basics, see this short video explaining wing stucture and controls here.)

Wing AR 2 slots? jjga Wing AR 2 slots? jjga

Artemis wingsail: 3 elements. How many slots? Copyright ? Annotations: Jack Griffin 365 x 260 Artemis Racing 365 x 260 Artemis Racing

First sail of the Artemis Racing AC72 wing. Valencia, 15 March 2012. Photo copyright Sander van der Borch / Artemis Racing

Let’s compare with the two element wing on USA 17 in race 1 of the 33rd America’s Cup Match against Alinghi 5 in Valencia in February 2010.  Look at the dimensions of the leading and trailing elements of Artemis’s wing and USA 17’s. Quite a difference!

USA17 camber-TM jjga USA17 camber-TM jjga

Two element wingsail of USA 17 in race 1, 33rd America’s Cup. Annotations: Jack Griffin

Camber is the angle between the leading and trailing elements. (You knew that, right?) By the way, here’s how camber is controlled on an AC45:

Wing AC45 camber control jjga Wing AC45 camber control jjga

AC45 wingsail camber control – Copyright Jack Griffin

It will be interesting to learn about the control systems for Artemis’s wing.  Kimball Livingston quoted Artemis CEO Paul Cayard  last November as saying the wing would have 38 hydraulic cylinders.  True? Or disinformation to throw off the competition?

In the same article, Kimball wrote:

The Artemis approach to efficiency, Cayard says, uses a three-element, two-slot wing. No surprise. Any wing is much more efficient than a mast and soft sail—for many reasons, not the least of which is that mid-leech tension becomes a non-issue—and C Class catamarans long ago demonstrated that three elements, two slots, are faster than two elements, one slot. I expect every AC72 to have a three-element wing.

 But that might not be quite right…   Here’s a picture of a C Class catamaran’s wing.  An aeronautical designer would say it has two elements, one of which has a flap.  In aeronautical terminology, the number of elements = number of slots + 1.

595x446-Wing-C-class-detail-3-el-2-slot-jjgb 595×446-Wing-C-class-detail-3-el-2-slot-jjgb

Wingsail design: C-Class catamaran wing with 2 elements + 1 tab

Do you think the Artemis wing has one or two slots?Comments? Questions? Answers?

What are the advantages of two slots?

How will the control systems work on AC72 wings?

 

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Surrogate yacht

 

Under the Protocol for the 34th America’s Cup, the number of sailing days in an AC72 or a surrogate is restricted.  But a team can sail as much as they want in yachts that are not catamarans over 40 feet long, unless it is an AC45.
Team New Zealand uses two “SL33” catamarans (less than 40 feet long) and tests wing designs on them.

Artemis has found a more clever (and expensive) solution:  they use a 60 feet long trimaran, big enough to test their full-size AC72 wing, which they first installed on 14 March 2012.  How much will this help Artemis?  Is the sailing performance of the trimaran close enough to a lighter AC72 catamaran? Share your opinion with a comment!