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 12 of 32

EAA Experimenter 13 T HE E NGINE H A S C RUI S E D M A N Y HOUR S AT 6000 RP M The new cylinders are lighter and stronger than the original cast aluminum Rotax versions. If you drop a cast cylinder on the floor, it can break off a fin and be dam- aged, but the billet cylinder can be struck with a hammer and will only bend a fin. There is 35 percent more cooling capacity with 14 fins per cylinder instead of the original nine. Hal picked a low-tension, nitride-coated ring that allows for higher rpm but requires compression for seal- ing at low rpm. As a result, it uses a little bit of oil, but so far Hal's customers haven't complained. It's a trade-off for more power and more durability. The aftermarket cylin- ders, pistons, and rings cost less than stock Rotax parts, and they reduce total engine weight by 3 pounds. The lower reciprocating weight allows for a faster throttle response to further boost the STOL performance. Details and testing of the kit were completed, includ- ing dyno testing of the engines to confirm the calculated power output. However, Hal was still flying a Subaru on his personal airplane. He said it was awkward to be promot- ing a kit he himself was not flying. In 2013 he purchased a used Rotax 912 in running condition off another airplane for $5,000, installed the upgrade kit now called the Zipper 1484, and swapped it with the Subaru. The kit comes in two versions. The low-compression pistons will allow any 80-hp Rotax 912 or 100-hp 912S to produce 104 hp with regular 87 octane auto fuel. A high-compression ver- sion boosts the output to 114 hp but requires 91 octane fuel or avgas. Hold on to your hat. Normal cruise rpm for the modified engine is 5700 to 5800. Rotax limits rpm over 5 minutes to 5500 and specifies a redline speed of 5800. Hal said he runs the engines at higher rpm because they can, and that's where you get the extra power. His engine can cruise at 6000 rpm and has cruised many hours at 6000 rpm. Heat is rarely an issue with those 14 cooling fins. When in a hurry to catch up with someone, he has run it at 6100 or 6200 rpm. Normal cruise for his RANS Super-7S is about 105 to 110 mph, where it burns 5 to 5.5 gallons per hour. Maximum climb is 1,000 fpm at 40 mph. With reduced pitch on the Whirlwind prop, it will climb much faster. When bystanders ask why they should consider the Zipper kit, Hal's answer always comes to the same point. This kit is for folks who need more power than the stan- dard Rotax 912 series for whatever reason (including floats) and also for those who need or want to run on regular auto fuel. Hal flies out at 5,300 MSL from a 700-foot sagebrush runway on the side of a hill with obstacles in Nevada's northern high country, so he needs to get in and out in hot weather at high-density altitude. A IRF R A ME C H A NGE S Hal gives the bulk of the credit for the amazing takeoff performance seen at AirVenture to the power of the engine, This cockpit view reveals a lightweight lithium battery on the fi rewall and HACman mixture control (red knob) on a simple panel.

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