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

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Page 15 of 32

16 Vol.4 No.4 / April 2015 A BIG BORE RANS SUPER S-7S without any reported problems. Hal and Wayne both be- lieve the piston and cylinder durability will be as good as or better than stock Rotax. The technology is more advanced and has been proven by a decade of Porsche off-road racing where these types of pistons and cylinders are subjected to much higher power levels. Hal says they are loafing in the Rotax 912. Naturally Bombardier-Rotax does not approve of modifi- cations to its aircraft engines. However, in experimental aircraft, once you buy the kit, it's your experiment. It's true for airplane kits such as the RANS and for engine kits such as the Zipper. The parts are top-notch quality and Hal stands behind his work if he installs the kit. After that, it's your experiment because he can't know how you will oper- ate the engine. Two additional projects are currently being tested. The first is a Big Big Bore (BBB) conversion for 912 engines that puts 92-millimeter forged pistons in billet cylinders with a measured output of 118 hp. The Zipper 1662 pushes the very limits of the Rotax 912 case, which must be opened and machined to accept the oversize cylinders. One such engine has more than 100 hours of flight time. Hal has calculated that 125 hp might be possible. A second, perhaps more practical engine design is the Zipper Turbo 1417, an 86-millimeter, low-compression version for the Rotax 914 that is currently being tested by Wayne Flemington. The slightly smaller diameter provides for a strong cylinder wall needed for the higher forces involved. It could theo- retically produce 135 hp. Information about the latest developments can be found, along with pictures and customer reports, on Internet avia- tion bulletin boards such as www.TeamKitfox.com or www.RANSclan.com/forums . The largest trove of com- ments comes from a thread of 128 posts on www.Backcoun- tryPilot.org . To order a kit, call Hal Stockman at 775-934- 5714. Wayne Flemington of Southland Rotax in California can be reached at 951-255-9144. Jay Stewart in Nevada can be contacted at 775-388-2046 and will be setting up a web- site for ordering kits. Dan Grunloh, EAA 173888, is a retired scientist who began fl ying ultra- lights and light planes in 1982. He won the 2002 and 2004 U.S. National Microlight Championships in a trike and fl ew with the U.S. World Team in two FAI World Microlight Championships. T e RANS Courier normally has a door on both sides of the airplane. Hal realized he never opened the lef side on his f rst RANS, so he eliminated it and saved some weight. This oversize left window can be opened in fl ight for photography, thanks to the gas lift struts. Photography by Dan Grunloh

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