Illustration by John MacNeill
To boost thrust and compensate for a slower engine speed, Hill mounted a larger, 14-inch propeller on the plane.
The Spirit of Butts Farm is powered by a vintage four-stroke O.S. 61 engine. Hill determined that tuning the engine to a relatively pokey 3,900 rpm could more than quadruple the aircraft’s range on the same-size tank of gas.
Two microchips crunch data from a GPS receiver, an altitude sensor, a tachometer and a piezoelectric rate gyro, which monitors angular velocity to determine whether the aircraft is flying level.
Hill eliminated landing gear and made the plane’s cross-section as small as possible to reduce drag.
Since 1981, Hill has used Coleman lantern fuel to set many of his 23 world records for distance. The fuel burns hotter and generates less engine-clogging carbon. To prevent the engine from melting during flight, Hill mixed in an industrial lubricant.
He may be legally blind and partially deaf, but 77-year-old Maynard Hill can still perform miracles with balsa and glue: In August the retired engineer stunned the hobby world by building the first model airplane to cross an ocean.
The Spirit of Butts Farm sailed from Newfoundland to Ireland in 38 hours and 52 minutes, shattering world aeromodel records for flight time and distance.
Strict rules set by the Switzerland-based Fdration Aronautique Internationale demand that a model weigh no more than 11 pounds. So Hill and his 12-man team spent five years developing a miniature satellite-guided autopilot capable of navigating the Atlantic. Even more daunting was how to fly 1,888 miles on less than a gallon of fuel, which was all Spirit‘s tank could hold and still make weight.
Hill started by swapping out the stock carburetor in his four-stroke, 10cc engine for a smaller one that sucked less gas. He then wired the engine with an electronic ignition and spark plug capable of burning Coleman lantern fuel, which explodes with more gusto than the Glo fuel most hobbyists use, he says.
Another fuel-saving trick: Hill tuned Spirit‘s engine to putter along at an average 49 miles per hour. The result? “A typical model engine can go for 10 minutes on 12 ounces of fuel,” Hill says. “Mine can go for about six hours.”