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Kite sailing - Go fly a kite

With the push for clean energy gaining ground, will sailors and commercial ship captains soon be using kite sails to capture the wind in new ways?

With the push for clean energy gaining ground, will sailors and commercial ship captains soon be using kite sails to capture the wind in new ways?

Harnessing the wind’s energy with kites to lift loads and pull something or someone across land or water is an entertaining endeavor that made kite sports a fixture in places with strong, steady breezes. Stunt kiters show their baffling tricks, para carts (aka kite buggies) zip about at breakneck speeds, and kite-surfers go bonkers and airborne.

Traction kites, as they are called, have a long and geeky history in propulsion experiments, towing skiers, sleds, buggies, boards and all manner of watercraft (see accompanying story). So there’s plenty of evidence that the concept works in certain settings. But how does it scale? And is it cost-efficient, practical and user-friendly enough to be applied on yachts? Can kite culture ease the sting of rising fuel costs, help reduce the smog-forming emissions of commercial vessels, and bring back motorsailing, that hybrid propulsion of wind-deprived cruising sailors and early steamships? What are the challenges, the solutions? And who’s going to become the Microsoft of traction kites?

Kite Sailing 101

“Our business is kite sailing, not kite surfing,” says David Culp, president of KiteShip Inc., a Martinez, Calif.-based company that manufactures and markets traction kites for marine applications ( ). Culp, who cut his teeth at speed-sailing events with kite boats more than 20 years ago, is putting kites on sailboats but has yet to land a contract with a commercial shipper.

“It’s the age-old conundrum of chicken and egg,” he says, referring to investment capital and sales revenue. “If you have one, you get the other.”

Culp and his business partner Dean Jordan, a kite designer, are maneuvering in the market’s gray zone between curiosity and acceptance. “Kite sailing is very different from kite surfing,” Jordan says. “It’s about MMR, the minimum-to-maximum pull ratio.” Simplified, it’s a matter of scale.

On a board or a buggy, one person can handle a kite across the entire wind window. However, a gigantic kite on a freighter could produce 120 tons of pulling force, which requires sophisticated equipment to control it. Jordan and Culp estimate that the sail area of these monster kites might exceed 50,000, even 100,000 square feet. But size isn’t the problem.

“With kites, bigger is better,” Jordan says.

Culp points to the 2005 Guinness Book of World Records, which lists KiteShip for the largest traction kite ever built, and the largest boat ever powered by a kite. The former is a 4,500-square-foot kite for the 66-foot Australian raceboat AAPT, while the latter is one of Larry Ellison’s 75-foot, 25-ton Oracle BMW America’s Cup boats.

KiteShip is using the racing market to gain visibility, but thus far big trophies have proved elusive. AAPT’s plans to ride a kite to victory in the 2004 Sydney-Hobart Race were foiled by adverse weather, and Oracle BMW’s experiments with kites for the 2002 Luis Vuitton Cup turned out to be more of a feint than a secret weapon.

Oracle personnel declined to comment, but observers say the syndicate might have pursued kites more for tactical advantages rather than performance gain. A kite flown on very long lines could have extended the boat’s length by several hundred feet, making it possible to cross the downwind finish line ahead of another boat that was sailing ahead of them with a conventional spinnaker. If successful, it also could have increased maneuverability in luffing matches, since a free-flying sail tethered to the deck wouldn’t produce heel like a spinnaker rigged to the mast. Capturing more wind at higher elevation — kites can fly well above the masthead — also was a perceived advantage.

Still, the Oracle kite remained in the bag. The official line is that development time ran out, but some surmise that gains did not materialize and that a kite proved impractical for match racing, since it would be difficult to set in a tight mark rounding with the large mainsail up.

A kite-sailing experience

Undeterred, Culp and Jordan keep demonstrating the virtues of their technology on raceboats and offer a money-back guarantee if, after 15 hours flying time, the boat isn’t faster than an identical boat with the same size spinnaker in the same conditions (minimum average wind speed of 10 knots). In moderate air, the Transpac 52 Flash reportedly reached a top speed of 12 knots with a 3,000-square-foot kite, while Shenanigans, a well-kept 1980 C&C 36, flirted with double digits under a 750-square-footer on a deep beam reach. Neither boat used a mainsail, so there was no significant heel because the kite pulled from deck level.

On Shenanigans, it took three people to handle the sail, without grinders for the primary winches. (In higher winds, additional crewmembers might be necessary as grinders.) The kite was connected to the boat with four lines: the halyard, attached to the kite’s upper edge and a block high up on the forestay; two control lines between the primary winches and the wing tips (the outer ends of the kite); and a center line from the kite’s trailing edge, or foot, to a cabin-top winch to adjust articulation.

To launch, the kite was hoisted from its bag on the foredeck and up to the block on the forestay, where it unfolded and caught the breeze. Culp trimmed both wing lines, Jordan saw to the center line, and one crewmember made sure the halyard was either slackened or “bumped” (a quick jerk on the halyard) as the kite crisscrossed the course line 100 feet ahead of the boat, sometimes kissing the water, sometimes surging above the masthead.

A kite derives its power from moving across the wind window, therefore it is in constant motion, jibing back and forth in front of the boat. David Wahle, an experienced skipper and former ocean racer, tested a kite on a 65-foot cat-rigged ketch. “It took the constant attention of two trimmers to keep it flying and pulling,” he says.

Learning to fly

After the kite was doused on Shenanigans and the Spectra sheets were stuffed into mesh bags, the boat motored upwind for another run — this time with the crew in charge of flight control. Listening to Culp and Jordan’s instruction, the mates learned to handle the kite and had the boat moving nicely. But they also dropped the kite in the water several times, once while letting a container ship pass. Twice they relaunched it from the drink, but at other times they had to bring in the halyard to hoist it, and it quickly filled again. Sailing kites, unlike surf kites, don’t have inflated edges that can assist a water launch, and sailboats, unlike surfers, won’t stop if the kite goes down. In any case, fast retrieval or relaunch minimizes the chance of passing boats fouling the floating control lines.

“The jury’s still out,” says Dave Fiorito, owner and skipper of Shenanigans. “The boat felt stable and fast, but I’d like to try it with the main up, too.”

“The speed under kite alone was as good as under standard spinnaker and main,” says crewmember Tim Jones.

His colleague George Wien liked that the kite in the water doesn’t cause broaching. “But a mainsail with its wind shadow and reduced forward visibility would make [kite operation] more challenging,” he says.

The session showed that the advertised benefits of traction kites — easy retrofit, no heel, and greater efficiency than traditional spinnakers — are real. On the other hand, the exercise also indicated that it takes the attention of a well-oiled crew and more than 10 knots of true wind to operate a kite effectively.

Thus far, sailmakers have kept a low profile in the kite game. “I think today the technology is not user friendly enough to warrant our involvement,” says David Ullman, founder and president of international sailmaker Ullman Sails. “But that is not to say it won’t happen down the road.”

Kites on commercial ships

SkySails, based in Hamburg, Germany, plans to bring kites to luxury yachts and target the commercial shipping market. Partly funded by government subsidies, SkySails was trying to land the first big deal but was pitching to potential investors.

Whereas KiteShip’s kite uses three control lines, the Germans incorporate a control pod under the kite that’s connected to the ship with a single cable. To assist with launching and retrieval, SkySails says it will use a telescopic mast. Last fall the company demonstrated a small system that pulled a 50-foot, 18-ton pilot vessel. Starting this year, SkySails says it will install traction kites on yachts and hopes to fit out more than 900 freighters by 2015.

“Our calculations show that fuel savings will vary by vessel but can reach up to 50 percent,” says Anne Staack, a spokeswoman for SkySails ( ). This claim should please shipping executives who are groaning because of high fuel costs and the growing scrutiny of engine emissions.

MARPOL (the International Convention for the Prevention of Pollution from Ships) and European Union laws now require ships to use more expensive low-sulfur fuels in designated Sulfur Emission Control Areas like the English Channel, the Baltic, and the North Sea. Yet few companies seem ready to bet future and fortune on kite power.

“Reducing fuel consumption is one of our main objectives,” says Lena Blomqvist, vice president of environmental and fleet performance at Wallenius Wilhelmsen, the Sweden-based shipping line that handles logistics for the current Volvo Ocean Race and purchases 800,0000 tons of bunker fuel annually. She’s aware of the kite concept and finds it viable, but says the company presently has no plans to employ it. Instead, Blomqvist points out its development of the futuristic Orcelle, a zero-emission car carrier that uses a combination of sun, wind, wave and fuel cell technologies.

Matson Navigation Company, an Oakland-based shipping company that operates in the Pacific trade-wind zone, imposed a 1.5-percent surcharge to offset higher fuel costs, but a spokesman says kite systems aren’t being considered for auxiliary power.

The race for solutions

To become commercially viable, kites must suit the needs of the shipping industry and its tight schedules, which don’t accommodate course changes for motorsailing. KiteShip and SkySails hope to build megakites of 50,000 square feet or more that would be complex to handle if conditions made it necessary to reduce or increase sail area.

Another challenge is the possibility of kites crashing ahead of a ship and fouling its rudder and propellers. In the 1980s a British Petrol research team abandoned experiments using helium-filled chambers to solve the retrieval problems because it was deemed too complicated and expensive.

Critics and proponents agree that making kites practical for commercial shipping is a tall order, and competes with other clean technologies that strive to balance cost, convenience and reliability. At this point, traction kites for large applications still haven’t closed the gap between possibility and practicability, but advanced electronics, new computer software and lightweight materials might change that. With higher fuel costs and more stringent emission controls looming, kites hold alluring promise, so there’s plenty of motivation to finish first in this race.

If the concept catches on, boaters could soon get used to the sight of kites pulling anything from container ships to cruising boats and wherries. But at this time, the operative word remains “if.”