APR 2015

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: https://experimenter.epubxp.com/i/492505

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Page 13 of 32

14 Vol.4 No.4 / April 2015 A BIG BORE RANS SUPER S-7S but a close look at the airframe reveals numerous small changes that could make a big difference. The wingtips plates and large tires give it the look of a purpose-built STOL aircraft. The wingtip plates were actually installed purely for hangar clearance. Hal said he believes they may help with low-speed handling. The tires are sand-racing tires that cost $65 each and work just fine compared to $1,500 bush tires. The RANS Courier normally has a door on both sides of the airplane. Hal realized he never opened the left side on his first RANS, so he eliminated it and saved some weight. Instead the window has been oversized by lowering the bottom edge, and he put gas lift struts on both sides. You don't have to latch the windows, and they don't fall closed when exiting or entering the air- plane. He can fly with the window open, which is great for photography. Ailerons and flaps were covered with metal, and the trailing edges were extended and refined to a thinner edge by extending sheet metal beyond the tube frame. It increases the chord of the ailerons and flaps about 1.5 inches and should make them more effective. The rudder trailing edge was also modified. Hal believes the trailing edge modifications increased his speed a little. An extra- heavy, double-fork, 8-inch tail wheel replaced the stock 6-inch wheel to handle Hal's rough airstrip. An access door on the left side provides for a much needed baggage compartment behind the rear seat. It can hold two 5-gallon fuel cans and accommodate up to 35 pounds. A lithium battery weighing 2.5 pounds replaced a 13-pound lead-acid battery. The different sound of the Super-7S comes in part be- cause it was equipped with a new prototype dual exhaust system by Vetterman Exhaust , which has been producing exhaust systems for the Van's RV series since 1990. It is designed to allow the engine to produce more power. The prototype exhaust is expected to evolve into a standard model for the S-7S. For a sample of the in-cockpit sound of the Vetterman exhaust in the RANS, watch the YouTube video " EAA AirVenture 2014: RANS S-7S Flight " posted by a volunteer, one of many youngsters who got a free ride from Hal while at AirVenture. It provides a nice view of the flight around the ultralight pattern. Hal uses a HACman mixture control on his Big Bore Rotax. The Rotax Bing carburetors are autocompensating up to 6,000 feet, but above that they become too rich. The controller works by reducing the ambient pressure in the carburetor float bowls. He described tests in hot weather over Washington state at 12,000 feet in his RANS Super-7S. His fuel burn without leaning was between 5 to 5.5 gph at 1,100 degrees on the exhaust gas temperature (EGT) gauge. After leaning with the HACman to 1,400 EGT, the fuel flow indicated 3.5 gph. He clearly recommends the device, and it would seem obvious you must have a working EGT gauge to A right-side door provides wide, easy entry to the cockpit. Photography by Dan Grunloh

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