October 28, 1968
A Whoosh As Good As A Wish
Smaller and more powerful than other marine engines, Thunderbird's water jet has one disability: its price is a bit more than $40,000
Hugh Whall
As a weekend pleasure boatman, what would you say to an engine that ran more economically at high speeds than at low, that developed more horsepower than your current power plant but weighed far less and was far smaller, that burned cheap oil instead of expensive gas, and that made fallible appendages like rudders, drive shafts and propellers unnecessary? The obvious answer is: don't ask foolish questions.
As a matter of fact, however, the question is not so foolish, for a Utopian power plant meeting all those requirements and designed for the amateur boatman actually exists. For some time now the citizens of Miami, many of whom must have thought a drunk was loose on Biscayne Bay in a shiny 32-foot power cruiser, have been witnessing its trials.
Whoosh! First it would start, then stop; back then fill, aimlessly turning this way and that as if its befuddled driver couldn't find the right control. On occasion it would swing out of Government Cut and head for the rippling Gulf Stream beyond Miami Beach, where its drunken maneuvering would continue in ever-tightening figure eights. Frequently, like some airborne Keystone Cop, an agitated helicopter could be seen chasing the demented craft. But the helicopter's bubble was filled with staid engineers from Pratt & Whitney Aircraft, the company that built the engine that drove the boat in those seemingly crazy circles.
The boat itself, Formula 322, built by Thunderbird Products Corp., bears the distinctive stamp of Race Driver-Designer Jim Wynne. In her cockpit is the customary steering wheel, dashboard, seats and cabin companionway, but instead of the bulky, raised engine boxes which usually cram fast powerboats, there is delightful emptiness. The uninformed passenger might suppose the new boat was powered by nothing but wishes.
Bolted neatly beneath her cockpit deck, however, there lies a comparatively tiny but power-packed turbine and water-jet propulsion system which—to boatmen accustomed to clanging pistons, erratic fuel and ignition hookups, dragging rudders and vulnerable propellers—is as good as any wish.
The engine itself is nothing new. It is the marine version of a United Aircraft turbine that has powered everything from buses, trucks, trains and helicopters to the racing cars Andy Granatelli entered in the Indianapolis 500. Called a free turbine, it is a distant cousin to the JT4 engines which propel commercial jets and bombers. Unlike diesel and gasoline piston engines, whose thirst for fuel increases with power and whose lives get shorter the longer they run at full bore, free turbines grow more economical and durable the harder they're pushed. In boats—where engines frequently run for long periods at full throttle—the advantages are obvious. Furthermore, so reliable are turbines that airlines have found they need tear down such engines only every' 12,000 hours or so instead of the every 4,000 hours demanded by piston engines. Indeed, the airplanes themselves are likely to wear out before their engines.
But the turbine power plant alone is not what makes the Thunderbird's boat such a potential dream-come-true; it is the combination of the turbine engine with a Pratt & Whitney water-jet propulsion system. The men aboard New York City's fireboats have long known that when you stand on deck and aim a high-pressure hose at a fire on shore, your boat tends to move back away from the blaze. The fireman's hose is nothing more than a water-jet propulsion unit, and the pump that pushes the water through it could be powered by a turbine.
In Thunderbird's new Formula 322, the turbine drives an efficient, compact rotary pump that spins at 2,100 rpm to suck up sea water from beneath the boat and spew it out of a nozzle at the stern with sufficient force to drive the 32-foot boat at more than 40 mph.
"We were worried at first that the thing would wash down other boats or docks that got in the way," says Wynne, "but we soon found we could aim the jet down far enough so as not to bother anyone."
To steer the boat, the driver aims the nozzle right or left and to reverse he lowers a metal deflector flap that shoots the stream forward underneath the hull, thus pushing the boat backward.
"A lot of engineering went into this boat," says Wynne, who designed the first successful turbine-powered ocean racer. "You don't just put a thing like that in there." The water-jet pump alone took Pratt & Whitney engineers three years to sort out, and when they mounted the first one in Formula 322 they weren't at all sure their tests in the lab at West Palm Beach had given them all the answers.
Says Project Engineer Carl Comolli, "We were afraid at the time we installed it in the boat that when the driver socked full power to it, the pump might cavitate [i.e., just open up a big air bubble] and not give thrust right away." It was also feared that the pump would stall or become powerless in high-speed turns. Worse, with the boat running in reverse, engineers were afraid the jet squirting back under the boat would cause turbulence in the water intake, starve the pump of water and thereby rob the boat of power.
Happily, however, all these fears were unrealized, and almost from the beginning pump and turbine ran smoothly, potently and with few hitches.
But the designers still worried that garbage, driftwood and other water-borne debris might be sucked into the pump to gum up the works. To find out they deliberately fed the pump a diet of hardwood plugs. It quickly swallowed the mess, apparently with considerable relish. Again, to satisfy the engineers that the pump wouldn't fly apart should the boat run aground, another experiment was performed in the lab. "We put tons of sand in it to see what would happen," cheerfully explains Dr. R. A. Schmidtke, P. & W.'s chief of research. "But instead of ruining the pump, the sand simply polished up its stainless-steel rotor."
Later, on the water, the pump sucked up a length of nylon rope. On a propeller-driven boat such an accident would have meant sending a diver overboard to cut it free. But not on Formula 322. Within the safe, dry confines of her spacious cockpit a crewman merely opened up an inspection plate, reached inside the pump and unwound the tightly turned coils of nylon.
So why don't all boatmen promptly scrap their diesels and their stern drives and buy a turbine-powered water jet? Well, for one thing, it will cost them around $40,000 for the turbine alone—a sizable price even for a wealthy yachtsman. "To the man who can afford the initial price and who can prorate the cost of a turbine over several years," says one Pratt & Whitney technician, "a turbine makes sense. But anyone who thinks they're just around the corner for the average boat owner is fooling himself."
Jim Wynne and Thunderbird President Dick Genth do not agree with this pessimistic appraisal. Says Genth, "Wait until they get this Vietnam thing straightened out and military contracts begin shrinking; then turbine builders will have to start thinking about the civilian market. Also, there'll be surplus helicopter and airplane turbines around. Besides, you've got to remember this engine's not that expensive. In ocean racing after nearly every race you've got to pull piston engines. You're talking about eight to 10 engines a season, and at $4,000 to $5,000 each, that adds up. For all intents and purposes, the cost of turbines is the same." Indeed, Wynne believes turbines will one day sell for less than diesels. Other Thunderbird engineers are even more optimistic, guessing they'll go for little more than gasoline engines.
The price still makes the turbine-powered runabout the boat of the future rather than the present, but Wynne believes that turbines now make possible—for those who can afford them—big yet extremely fast power yachts. "We simply couldn't do this with any other kind of engine because they'd fill up the boat, leaving no room for cabins, galley or any comfort," he says. "Fifty-footers used to do 20 knots in a pinch. With turbines we can move up the ladder to 35 or 40, yet not give up anything in the way of accommodations."
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