Experimenter is a magazine created by EAA for people who build airplanes. We will report on amateur-built aircraft as well as ultralights and other light aircraft.
Issue link: http://experimenter.epubxp.com/i/90184
Lohmar's canopy is more than it seems. It's been optimized to be as light and aerodynamically clean as possible. fl ying. You need fi ve instruments in the rear cockpit—any fi ve—and they have to work. We've moved the battery (and thus CG) aft. We also add lead to the rear to bring the center of gravity all the way to the legal limit. The rear seat and stick come out and stay on the ground for the race." The original T-6 empty weight of about 4,200 pounds is reduced as much as practical, through removing (or sometimes substituting or downsizing) components. Re- moval of power-sapping accoutrements (such as ventu- ris, antennae, and even wind-powered generators) helps weight reduction, too (although some of the race modi- fi cations, such as fi re-suppression systems, the pilots' parachutes, and ballast, for example, add weight). 1997 and 2005 champion Mary Dilda, a very slim blonde, said that her crew wanted her to lose a hundred pounds. Lohmar said, "In the Unlimiteds, they have two main rules: a piston engine and a minimum weight of 4,500 pounds. In our class, we have to stay true to the original certificate's specs and use the R-1340 with a 10-to-1 blower (the 12-to-1 'helicopter' blower is now illegal). During tech inspection, all the front spark plugs come out to be sure nobody's running domed pistons; the flat- tops pistons are assured. No nitrous, no enhancers [no oxygenates]. We all use 100LL, and the tech inspectors check fuel randomly, right before the race. "In the Gold [Race], the big advances come from aerody- namic cleanup. Make all the seams fi t; make all the pan- Photography by Tim Kern els lay real nice and fl at. This plane's 1,000 little panels, so we use fl ush rivets where they're allowed (and we'll even put a coat of Bondo on to make them nice and slick). Make it cleaner, with straighter rigging, better sealing. We use a polymer outer coat to reduce drag, and then we go over the whole plane just before the race with a 'California duster' and get the last bit of dust off." The canopy looks primitive; that's just how it looks. The original was made of metal framework and a number of mostly flat glass panels. Now, "We routed the edges of the Plexiglas panels on the canopy to be flush; on ours, as on most of the racers, the main canopy is actually all one piece." The metal "cage" fits into grooves in the one-piece clear plastic, presenting a flush outer surface to the wind. "We make sure the gear doors are tight and flush, and we'll reroute the fuel tank vents and change the drains," which hang down when they're stock. In sum, Lohmar said, "It's commonly thought that somehow we've made huge modifications, but the rules say they need to conform to the original certificates; and they check. Long ago, there were a lot more modifications allowed—Miss TNT was a great example." Miss TNT was fast (a seven-time Gold champion), but its extensive modifications would not be allowed to- day, and those mods likely figured into its retirement. EAA EXPERIMENTER 23