This is the racing event, involving simultaneous flying and pitstops.
2:nd, E/Ch '97:
Regis Gilbert, FRA
Final Pilots, E/Ch '97:
Ch. Gilbert, FRA,
Myself Practising Pitstops.
Pilots in Action (animated GIF)
A model from Australia: Keith Baddock's (using my wing outline)
French World Champions 2000, Maret and Perret, describe their equipment.
The international class is F2C. A pilot and a mechanic compete as a team to fly small (350 grams)(12 oz.) 65 cm (25 in.) wingspan semi-scale racing models over a tarmac or concrete surface. Lines are 15.92 meters long (52.231 ft).
Three pilot + mechanic teams compete simultaneously in the same circle, and the object is to finish the determined course as fast as possible. The all-out important catch is that tank size is limited to 7 cc. (About one and a half teaspoon.) Thus 2-3 pitstops for refueling are needed during the race.
The mechanic stands at a pit area outside the marked flight circle. He will start the engine and release the model at the start signal and then stand alert for refuelling. The pilot will operate a fuel shutoff by a quick down elevator movement after the planned number of laps so that the model can approach the mechanic at optimum speed, around 50 km/h (30 mph). The mechanic will catch the model by the wing, fill the tank from a pressurized can by a hose and finger valve. Then restart the engine by hitting the carbon fiber/epoxy resin propeller with his finger. Ground time of a good pitstop is less than three seconds.
The race course is 10 km, corresponding to 100 laps. Flying speeds are around 200 km/h (125 mph), which means that the pilots have to turn one lap in 1.8 seconds. Line pull due to centrifugal force is 85 N (17 lb) (19 g:s). A faster model will overtake by the pilot steering it above the slower one while he moves his handle with lines over the opponent pilot's head. Conduct of both pilots and mechanics is subject to numerous regulations. Line tangles aren't as common as you might think, since the penalty normally is wrecked models. Natural selection at work.
After two rounds of elimination heats, the 6, 9 or 12 fastest teams enter two semifinal rounds, and the three fastest teams in the semifinals go to the final, which is run over the double course.
Maximum engine size is 2.5 cc (.15 cu.in.). Diesel, i.e. compression ignition engines are used. They are single cylinder two-stroke, designed and highly specialized for this purpose. At the world championship level it is not uncommon that the competitors design and build their own engines. Their output power is approaching .8 horsepower at 25,000 rpm. A drawing of engine and tank.
The fuel is 50% kerosene, 35% diethyl ether, 10% castor oil plus various additives, most notably amyl nitrate 1-3%. (And maybe a few specials, such as my own.) The tank 7 cc capacity leads to fuel economy tradeoffs to limit the number of pitstops to two. The fuel system includes a multifunction valve to ensure optimum starting, running, stopping and refuelling operations.
Some model regulations:
Semi-scale appearance; Wing + tailplane area: 12 sq dm. Fuselage at pilot location: Height 100 mm, width 50 mm, area 39 sq cm. Cabin with clear windshield and pilot head are mandatory. Landing gear wheel 25 mm diameter.
Models nowadays normally are of the flying-wing type, and some think the semi-scale appearance requirement has degenerated. My own design as an example.
Wing: lightweight "quarter grain" balsa with spruce & abachi reinforcements, glass fiber/epoxy covering. Maximum thickness is around 7.5 mm (.3")
Fuselage: Either carbon fiber/epoxy shell or balsa shell plus harder wood reinforcements and glass/epoxy covering.
Other interesting facts:
The aerodynamic drag of the control lines is more than half of the total drag.
If the pilot holds his handle 30 cm (1 ft.) behind the center of rotation (due to blocking action of an opponent) this introduces more braking force than the entire drag of the model.
Fuel and compression settings have to be carefully adjusted by the mechanic. The compression setting is the means of getting the proper ignition point, and is extremely difficult do do properly. The slightest decrease will cause misfire and loss of speed, and the slightest increase will cause thermal runaway due to pre-ignition.
Simplified classes, such as Goodyear Racing, are also flown in many countries. Here models are 'profile' fuselage 1/8 scale versions of real racing aircraft, or profile fuselage versions of F2C models. My design.