October 18, 2004
Steady Sea Flyer gives Navy its water wings
By Gidget Fuentes
Times staff writer
ABOARD SEA FLYER — Along the waterfront, this 160-foot ship wouldn’t stand out among the Navy’s larger gray hulls.
But here, off California’s Point Loma peninsula, when Sea Flyer kicks up its twin diesel engines to 28 knots, this ship goes flying — literally — through the water.
By design, the 320-ton demonstration craft — with an innovative hull the Navy is studying — doesn’t rock sideways or roll like most ships would in rougher seas.
Below the water line, Sea Flyer’s hull features a protruding, aluminum midhull foil and a titanium aft foil with twin propellers. At faster speeds, the winglike foils help lift the body of the ship, raising it off the water and reducing drag and friction from the waves.
“When it’s flying, the hull is completely lifted out of the water,” said Office of Naval Research spokesman Michael H. Bland. “You can actually see underneath the hull.”
This experimental ship can nearly pilot itself by its shipboard computers and sensors.
In the pilothouse, at Sea Flyer’s helm for a Fleet Week sea and air parade, Greg Wong isn’t just the captain. He’s a pilot, of sorts.
“It kind of acts like a hydrofoil, but it has a lot of buoyancy,” Wong said. “It’s basically like an airplane.”
At the helm is a joystick control and color monitors, computers and buttons that control the foils, flaps, engines and propulsion. Radar reads the height and roll of oncoming waves and adjusts as needed. The ship can turn a circle in 800 yards, come to a full stop in 30 seconds and barely leave a wake in “fly” mode. A computer system “does all the ride control,” he said. “I just point the boat” where he wants to go.
Sea Flyer is part of an $18 million contract with Navatek Ltd., a Hawaii firm working with ONR on future hull designs. The ship itself has no operational mission, but it will help evaluate “lifting body” technology for future Navy hull designs.
“It’s more of a technology demonstration,” said Scott Littlefield, ONR’s director of ship science and technology.
Sea Flyer itself is no stranger to the Navy. Built in 1980, this former “surface effect ship” was used to experiment with seagoing designs. Navatek in 2002 installed its “H” lifting body, which evolved from SWATH — or small waterplane area twin-hull — technology the company and ONR have also explored.
Hydrofoil isn’t a new concept. A generation ago, a fleet of a half-dozen fast-attack patrol boats — with PHM hull designation — was based at Key West, Fla., and used primarily for drug interdiction missions.
“The Navy’s interest in small, fast ships … has kind of waxed and waned over the years,” Littlefield said.
Those twin-engine boats were retired in 1993, victims of Navy downsizing.
But the coming Littoral Combat Ship and options for future sea-basing have driven a resugence in smaller boats that handle rough waters, Littlefield said.
Sea Flyer will return to Hawaii this fall and continue to be used as a test platform, in part to find ways to reduce friction drag.
Navy's Sea Flyer is no rough rider
By James W. Crawley
UNION-TRIBUNE STAFF WRITER
October 2, 2004
The experimental Sea Flyer has a submerged, winglike structure that lifts the boat's hull out of the water so it can glide above the waves.
ABOARD THE SEA FLYER – Skipper Greg Wong pushed the twin throttles forward while glancing at a cockpit computer screen.
Ten knots. The diesel engines throbbed through the steel deck. 15 knots, then 20.
Somewhere before the readout hit 25, Sea Flyer became just that – a flier.
Its hull rose above the light swells off Point Loma and the 270-ton vessel was airborne.
Sea Flyer is a boat that flies.
Built for the Office of Naval Research, Sea Flyer is a $20 million, 167-foot experimental vessel with a submerged, winglike structure that lifts the boat's hull out of the water so it can glide above the waves.
The Navy hopes the boat will be the precursor for a fleet of futuristic, high-speed combatant or surveillance ships that could maneuver through light or rough seas. The Navy's research branch has pumped millions into Sea Flyer and a fleet of other unusual watercraft in hopes of inventing faster, better ships.
"The Navy is interested in technology to improve the performance of small ships," said Scott Littlefield, the research agency's director of ship science and technology office.
"The Navy has a lot of experience with large ships," he added. "But small ships don't do well in rough seas."
To improve speed and smooth out a rough ride, Sea Flyer is designed to rise out of the water, thus reducing the hull's drag through the water. The underwater lifting structure, which Littlefield described as "a fat wing," provides lift like a plane's wing and buoyancy like a ship's hull, but with less drag.
As Wong pushed Sea Flyer to 30 knots, the boat's flat hull was fully airborne with only several struts connecting the vessel with the lifting body hidden beneath the water.
Computers constantly monitored acceleration, pitch, yaw and roll, adjusting airplane-like flaps to lift up and steer Sea Flyer. Computerized gauges showed how the flaps continuously compensated for waves and swells.
"There's no way to run it without a computer," said Wong, who works for Navatek, the Hawaii-based firm that designed and operates Sea Flyer for the Navy.
Driving – Wong called it "flying" – is simple. A light touch on a joystick mounted on the captain's chair changed Sea Flyer's course.
"The real genius in the boat is in three gray (computer) boxes," Wong said.
Sea Flyer is enjoying a second life.
It was built in 1979 as a prototype craft that used fans beneath the hull to lift it out of the water. The Coast Guard evaluated it, too. In the early 1980s, the boat was lengthened by 50 feet. The craft was eventually mothballed but resurrected last year in the Sea Flyer configuration.
As an experimental vessel, Sea Flyer has a crew of civilians and won't see combat. Next year, it will be used to train crew members for the Navy's X-Craft, a large catamaran that will try out ideas for the Navy's proposed coastal combat ships whose equipment can be changed depending on the mission.
However, that's all in the future for Wong and the Sea Flyer.
He has an eye on today's Fleet Week Sea-n-Air Parade on San Diego Bay, when the Sea Flyer will "taxi" along at a slow 8 knots.