Thursday, September 26, 2013

Fast boats

A boat owned by billionaire Larry Ellison won the 2013 America's Cup series of sailboat races. It defeated the challenger Emirates Team New Zealand in a comeback performance having lost most of the early races and won all the late ones. A costly series of overnight refits is credited with lifting the US boat's fortunes.

There is a compilation of videos documenting the race here: America's Cup 2013.

Run on and off since the middle of the nineteenth century, the race pits boats from two countries against each other. An ornate trophy passes to the winner of the event. Various yacht clubs and syndicates in the United States held the cup for many years, and during the past few decades it has been won, and defended, by Australia, Italy, Switzerland, and New Zealand. Great Britain, the first to accept a challenge for the cup, has never won it. By convention, the defending country determines the rules of each race, including the specifications of the boats.

This year's series of races took place between boats representing the United States and New Zealand. It followed elimination contests among challengers from Italy and Sweden as well as New Zealand. Aiming to profit from interest by local spectators and an international video audience, the US syndicate opted for a location, San Francisco Bay, which offered excellent spectator views and a scenic backdrop for video cameras. It chose a boat design which took advantage of the Bay's strong winds and tidal currents. And it set a course which insured that the boats would achieve maximum speed in long up- and downwind legs. The boats themselves, designated AC72, were large catamarans with sails like airplane wings, rudders analogous to the rudder/elevator combination of airplanes, and daggerboards which (akin to the tail and wings of an airplane) served the dual purpose of keel/centerboard and hydrofoil. During preliminary races, the top speed of these boats proved to be greater than fifty miles per hour.

However, sailing at top speed proved to be too dangerous. During the preliminaries an Oracle boat in the US stable flipped and was wrecked with no injury to the crew and another, Artemis from Sweden, flipped at high speed, killing one member of the crew. As a result the race committee established rules to rein in dangerous maneuvering at high speed.

Over the eleven miles that the boats traveled in each race, the eleven-man teams accomplished complicated changes of course — tacks and jibes — very rapidly and with great skill and they made frequent rapid adjustments when traveling on straight paths at top speed, all aimed at gaining the few seconds advantage that made the difference between victory and defeat. Almost literally flying, the boats were made to travel in the downwind leg of the course at twice the speed of the wind. Explanations of the physics that lie behind this achievement are opaque. The skipper of a sailboat will trim his sails to achieve maximum speed for any given course. When the boat is at rest the true wind and something called the "apparent wind" come from the same direction at the same speed. When the boat is sailing at an angle into the wind, the "apparent wind" is greater than the true wind and we are told that the difference between apparent and true wind is what enables a boat to sail faster than the wind.
As the sail moves into the wind, it "feels" a faster wind on its face. This is called the relative velocity of the wind with respect to the sail. A wind of larger relative velocity exerts a larger force on the sail, which accelerates the boat. The boat moves faster, which increases the relative speed of the wind, which increases the wind-force, which accelerates the boat, and on and on.

-- How Sailboats Sail Against the Wind, Physics for Architects

A boat won't actually sail faster than the wind, however, unless the sails are unusually efficient and the drag of the water on the hull is reduced to a minimum. The most efficient sails are no longer made of cloth but rather carbon fiber and kevlar. Called wingsails, they are composed of fore and aft sections that resemble the wing and flap of airplanes. The wingsail's "flap" is unlike the airplane's, however, being proportionately much larger than the wing itself. The wing and flap are constantly monitored by sensors connected to onboard computers and can be independently adjusted to increase or decrease the amount of lift the wing provides. Greatest lift is needed at slow speeds, but it comes at the cost of increased drag. Thus, like an airplane during take off, in flight, and landing, the boat's wingsail is adjusted to give the best balance of lift and drag as the boat moves faster or slower through the water. This constant adjustment takes the place of much of the sail trimming that's needed when using conventional sails (sheeting in and sheeting out) and in fact the AC72's wingsail is swung off center a great deal less than are conventional sails.

This graphic names the parts of a wingsail and explains its operation.

{source: Wing-Sail-tech on}

The second major element in achieving flight on water is the reduction in resistance of the water itself. This drag is reduced to a minimum by use of wing-like hydrofoils to raise the hulls out of the water. Once the wingsail has brought the boat to a critical speed one of the two foils, or both, raise the hulls out of the water. Like the job done by the wingsail, the work done by the foils is difficult to fathom. The weight of the America's Cup AC72 boats is something like 13,000 pounds. Once the boat is foiling, it can accelerate to maximum speed, up to about twice the speed of the wind.

The following photo shows the Emirates Team New Zealand boat elevated on one of its two hydrofoils (the other is raised above the port hull). The two aft rudders have adjustable wing extensions, but they are used, like the elevators on the tail section of an airplane to which they are analogous, to keep the hulls parallel with the water surface and not to raise the hulls into flying mode.

{Caption: Emirates Team New Zealand’s AC72 foil sailing on the Hauraki gulf. Auckland, 6 September 2012. Photo copyright Chris Cameron / Emirates Team New Zealand; source:}

Below is a computer drawing of an AC72 catamaran such as the ones racing for the America's Cup. I've marked the image to show the articulated wingsail and the starboard hydrofoil, which sailors call a daggerboard. Daggerboards not only provide lift, but also help keep the boat from being pushed sideways against the wind. This function is performed by the keel or centerboard of mono-hulled vessels. Note that AC72 daggerboards are lifted up and down vertically while centerboards swing up and down from a forward pivot (keels are fixed in place). The AC72 boats can carry two jibs, as shown here, but in most races they have carried only one small one. The jibs (also called foresails or softsails) are made of cloth and their main job is to direct air over the wingsail.

This image shows the two boats that competed in this year's America's Cup series. The next one, directly below, shows what America's Cup competitors looked like in 1899.

{Caption: Emirates Team New Zealand leads Oracle Team USA down the first run in race seven on day four of the America's Cup 34, 9/12/2013; source:}

The 1899 boats, like all America's Cup boats contenders to 1988, were mono-hulled. They were gaff-rigged sloops with narrow beam. The sail area was enormous. It's evident that they are manned by about twice the number of sailors as are this year's boats (which the rules limit to a total of eleven).

{Caption: Shamrock and Columbia maneuvering for the start, Detroit Publishing Co., Oct. 19, 1899; source: Library of Congress Prints and Photographs Division}

This image indicates how large is the AC72 wingsail. The AC45 is a catamaran which closely resembles the AC72 on a smaller scale. It was used in shakedown and elimination races prior to this years America's Cup series.


As the image suggests, it's the height of the AC72 wingsail which most impresses. Its supporting mast is 131 feet high. By comparison, the yacht that won the America's Cup for the first time (1851) and the schooners and sloops that raced for the Cup during the rest of the nineteenth century had masts no higher than 105 feet.

The location of the race in San Francisco Bay and its windward/leeward course as well as the speed-oriented design of the boats themselves were chosen with a view to making money off the event. Huge numbers of on-site spectators and world-wide TV viewers could pretty much be guaranteed by the excitement generated in extremely fast racing close to a major city, offering on-land as well as on-water viewing of spectators, and TV viewing via large numbers of video cameras, in helicopter, in tracking boats, and onboard the AC72s themselves.

In fact, the boats' design proved to sacrifice safety for speed. When, during preliminary races, one accident destroyed a boat and another killed a sailor, rules had to be revised to prevent possible collisions during the critical moments just prior to start and to shut down racing when winds, currents, and wave heights made it too dangerous. "Too dangerous" is a relative measure, however, as the race series has proved to involve a great deal of risk for boats and crews.

This graphic shows the course. The high-speed long legs between windward and leeward gates, which the boats traversed three times during each race, insured that spectators got to see many extremely fast tacks and jibes.

It's difficult for people accustomed to soft-sail racing to comprehend how the AC72s are able to reach their highest speeds when sailing with the wind at their backs. They do not run before the wind in the usual sense but rather jibe and jibe again just as if they were tacking into the wind. That is to say they take a zig-zag course when the wind is astern just as they do when it is coming from the front. During these jibes they actually look like they are tacking since the wingsail is not let out, as a soft sail would be, but is kept close-hauled as in tacking. As one sailor said: "You might have also observed how tight in the sails were trimmed in the 'downwind' heading. They were tight – even the non-winged headsail. This means the AC72s were on a close haul heading downwind. Messes with your mind doesn't it?" (Apparent Wind on Americas Cup AC72's)

So, the defender and the challenger in this year's America's Cup were fast and exciting to watch. During early races in the series they were also evenly matched. The boats seemed to be capable of the same speed and maneuverability. Sailing skill, tactical acumen, and quite a bit of luck mattered most in determining who would win each race in the series. Oracle gained an edge, however, after making a number of adjustments to the boat after it lost enough races to come within one of losing the Cup. The most significant change was apparently the installation or revision of an automatic levelling system. It is said that the Emirates Team New Zealand boat, relying on manual control of its stabilizers, couldn't match Oracle's computerized system. Ironically, the technology used by Oracle was designed and built by New Zealanders under contract to Oracle's owner Larry Ellison. It's worth noting that both boats were built in New Zealand and both were mostly crewed by New Zealanders. Many accounts credited the Oracle Team USA win with increases in sailing skill achieved during the race series rather than changes made to the boat.

Early on, the US team had shown that they were capable of cheating. During preliminary races the crew of the US boat were caught adding weight to the bow in order to improve its fore-and-aft trim. In other sports, it's the norm to exclude cheaters from competition, but, since the United States were the defenders, the entire series of races would have to be canceled if the US side was prevented from sailing. Therefore, although race officials declared that "the seriousness of the breaches cannot be understated," they contented themselves with barring from competition the sailors who were found to be directly involved in the scandal and with giving the challenger a two point advantage in the race series. The two-point advantage meant that the Emirates Team New Zealand boat needed nine points to win while Oracle Team USA required eleven. A "point" in this context is the winning of a race in the America's Cup series.

One might suspect that the lack of sportsmanship shown by the American side had something to do with the billionaires' club atmosphere of the races themselves, billionaires being thought by some to be accustomed to getting their way by fair means or foul.

We are accustomed to the influence of individual wealth in sports: baseball, football, and soccer teams owned by billionaires as well as billionaire owners of race horses and race cars. As owners and participants both, wealthy people dominate elite sports like polo and dressage, and they reserve to themselves certain exclusive ski resorts, golf clubs, and shore properties. The America's Cup races were dominated by men of wealth considerably more than other sports. The cost of competing was calculated at about $100 million per participant. Larry Ellison, owner of the US boats, is said to be the third richest man in America, fifth richest in the world, and the owners or major investors in the challenger boats were mainly billionaires themselves. There were three challengers participating in preliminary races to determine who would sail against Oracle Team USA. Sweden's boat, Artemis, belongs to billionaire Torbjorn Tornqvist, a Swedish oil magnate; Italy's, Luna Rossa, by billionaire Patrizio Bertelli, Prada's chief executive, backed Italy’s Luna Rossa. Although New Zealand's team was partly financed by its government, its main source of funds was the sovereign wealth fund of the United Arab Emirates and that fund is directed by the ruling monarch of the country and his family, who are billionaires.

As we're accustomed to the presence of billionaires in sports, so we're also accustomed to the billionaires' practice of treating sports as investments, or quasi-businesses, whose tax consequences are often the production of massive deductions. I've found little information on this practice in the America's Cup races beyond the obvious concern to maximize revenue from spectators, whether in San Francisco or watching TV worldwide.

The down-to-the-wire racing and a dramatic come-from-behind finish of this year's America's Cup series made for an exciting spectacle, but the sport is so much more outrageously elitist than other spectator sports that this Cup is bound, like most of the others, to be quickly forgotten. As the editor of Slate says,
Oracle Team USA fell way behind and then beat Emirates Team New Zealand, proving once and for all that the mercenary Kiwis who race monstrously expensive death boats for the good old Stars and Stripes perform better in the clutch than the Kiwis who race monstrously expensive death boats for the motherland... There’s really no rational reason for someone who isn't from New Zealand and/or some type of robber baron to care even one bit about the America’s Cup, or to root for Larry Ellison and his team of sailing carpetbaggers.
-- The Miracle on San Francisco Bay; Oracle Team USA’s billionaire-funded, cheat-tastic America’s Cup comeback reveals the awesome power of the inspirational sports narrative. by Josh Levin, Sept. 25, 2013, in Slate


Some additional images:

This shows the left, leeward, hull of the US boat, Oracle, showing the leeward hydrofoil daggerboard (below the American flag) and the leeward rudder (red). The rudder has a fin which provides horizontal trim to the hull (it raises and lowers the stern) as well as twisting to turn the boat.

source: AC34, Louis Vuitton Finals: Weekend Wrapup on

This shows the Emirates New Zealand boat from above. It is here shown headed downwind, but nonetheless close-hauled (both jib and wingsail are close to parallel with the hull). The white dash-marks just to the right of the wing (a wide center-mark and adjacent narrow marks) show how very little the wing swivels from side to side. You can see that the starboard daggerboard is down while the port one is up. It's hard to tell, but it seems that neither hull is touching the water; that is to say, the boat is flying on its starboard hydrofoil daggerboard. You can see the disturbance in the water caused by the port rudder, but it's obvious the port hull is entirely elevated.


This list gives the AC72 design parameters:
LOA 22.0 meters (72 feet)
Beam 14.0 meters (46 feet)
Displacement 5,700 kilograms (12,500 pounds)
All-up weight 7,000 kilograms (15,500 pounds)
Wingsail area 260 square meters (2,800 square feet)
Wingsail height 40 meters (130 feet)
Wingsail chord 8.5 meters (28 feet)
Sail trimming Manual grinders
Configuration Twin-hulled catamaran
Crew 11
Sail trimming No mechanically powered systems
Sail area reduction Removable top sections/leech elements
Appendages Maximum of 2 rudders, 2 daggerboards
Construction Minimum 600 grams per square meter outer-skin;
High-modulus carbon-fiber permitted in wingsail spar

-- 34th America’s Cup: New AC72 class, the fast, spectacular, wingsail catamaran unveiled, September 20, 2010

This shows one of Oracle's boats capsizing in preliminary trails a year ago.

{Caption: Oct 16, 2012: Oracle Team USA's disastrous AC72 capsize; source:}

This gives an idea of the size of the wingsail.

{Caption: Emirates New Zealand wing sail; source}


Some sources:

Kiwis Reach Record Speed in AC 72-Foot Catamaran, Associated Press, Jul 19, 2013

The Boat That Could Sink the America’s Cup by Adam Fisher, 05/09/13 on

America's Cup
on YouTube

Day 6 racing blog
SEPTEMBER 15, 2013
Race 10 Performance Data

Course: 5 Legs/10.02 nautical miles
Elapsed Time: ETNZ – 22:00, OTUSA – 22:16
Delta: ETNZ +:16
Total distance sailed: ETNZ – 11.8 NM, OTUSA – 11.7 NM
Average Speed: ETNZ – 32.25 knots (37 mph), OTUSA – 31.76 knots (36 mph)
Top Speed: ETNZ – 43.01 knots (49 mph), OTUSA – 44.98 knots (52 mph)
Windspeed: Average – 18.3 knots, Peak – 22.3 knots
Number of Tacks/Jibes: ETNZ – 7/7, OTUSA – 7/7

Emirates Team New Zealand gets leg up on ORACLE TEAM USA
by Sean McNeill

America's Cup: Emirates Team NZ admits AC72 can foil sailing downwind by Richard Gladwell on

Americas Cup Apparent Wind on

Apparent Wind on Americas Cup AC72's on

America's Cup boats use innovative design built for speed and power on

The Sailors and Their Flying Machines,


wingsails on

America's Cup News and Information on

America's Cup on YouTube

America's Cup: How hydrofoiling works in the AC72's on

Image Bank on

Severe penalties for cheating Team Oracle by Duncan Johnstone, 4/9/13, on

Yet another AC34 Controversy by Adam Cort, Aug 16, 2013, on

AC34 Team Oracle Caught Cheating…Again on

Billionaire death race: inside America's Cup and the world's most dangerous sailboat. Capsized yachts and a sailor’s death cast a pall over this week’s finals. by Casey Newton on September 3, 2013, on The Verge

Winging It: America’s Cup Racers Push the Sailboat to Its Limits by Adam Fisher, August 18, 2011, in Wired magazine

The Husky Sailors Take on America…or at least its Cup

The Lawson history of the America's cup: a record of fifty years by Winfield M. Thompson (Boston, Mass., T.W. Lawson, 1902)

Wing-Sail-tech at

AC34: The Anatomy of an AC72 by Mike Drummond, Jun 19, 2013, in Sail Magazine

AC34: How to Get Around the Racecourse by Kimball Livingston, Sail Magazine, Jun 18, 2013

Well at least the horse racing industry is recovering by Lydia DePillis, September 23, 2013, in the Washington Post

"Valkyrie's Steel Mast Will Be One Hundred and Five Feet Long and Very Light." New York Times, August 6, 1896 (filed Glascow, July 7).

Made-for-TV America’s Cup Imperils Sailors Pursuing Speed by Aaron Kuriloff, Sep 12, 2013, on

AC72: Ellison's Dream Is Scariest Racing Yacht Yet on

Larry Ellison's Ahab-Like Quest For The America's Cup by Daniel Fisher, on Forbes, 5/22/2013

Meet the Billionaires Behind America’s Cup by Tara Loader Wilkinson, 14 August 2013, on

Board of Directors, Investment Corporation of Dubai

Larry Ellison's Amazing Victory and Huge Failure by Jonathan Mahler Sep 25, 2013, on

The Miracle on San Francisco Bay; Oracle Team USA’s billionaire-funded, cheat-tastic America’s Cup comeback reveals the awesome power of the inspirational sports narrative. by Josh Levin, Sept. 25, 2013, in Slate

Kiwi fans ask: 'Did Oracle cheat?' by Tom McRae, 26 Sep 2013,

America's Cup: Legal challenge not likely by Paul Lewis, Sep 26, 2013, on

America's Cup on wikipedia

AC72 (America's Cup 72 class) on wikipedia

Sailing faster than the wind on wikipedia

Wingsail on wikipedia

Sailing hydrofoil


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