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/339662
EAA Experimenter 21 Mark wasn't completely new to the powerplant design world. A dozen years ago, he invented the Rad-Cam, a two- cycle, 65-hp gasoline rotary engine. The Rad-Cam's design was quite different; its novel cam shape held the piston at the top dead center of its stroke. The cylinder would then hold a confined, lean mixture under high pressure. Thus, the engine would produce a complete burn of the lean mix- ture. The engine was predicted to lower emissions, lower vi- bration, and increase efficiency over conventional engines. The concept demonstrated one thing that is quite striking about Mark: his obsession with efficiency. It started when he was five and he became interested in how much fuel airplanes burned. Now Mark talks about thermal efficiency, explaining that if you can feel heat coming off a machine, there is some lost energy and the machine could be made more efficient. Similarly, if you can hear a vehicle, then the sound vibrations are costing efficiency. Perhaps that is why Mark is so soft spoken. Mark's approach to the Rad-Cam emphasized both technical efficiency and cost efficiency. He anticipated the engine would greatly improve ultralight performance, but it would also be attractive for other, bigger markets as well— motorcycles, personal watercraft, recreational vehicles, electric generators, and—take that, Rotax—snowmobiles. With this approach, a third party would manufacture the Rad-Cam engine in large volumes, making the engine afford- able for all. Ultimately, the Rad-Cam was a victim of the recession. Al- though the engine had fl own, Mark no longer had the money to develop the concept further. He switched his focus to elec- tric fl ight. The airplane he would "electrify" was the company prototype Gull 2000 ultralight. It had an empty weight of 248 pounds and a 20-foot wingspan, and it fl ew with a 28-hp Hirth F33 engine. Mark used of -the-shelf motor system com- ponents for the early fl ights. The motor was a PMG 132 model weighing 25 pounds. The controller was a 72-volt Kelly 72401, and the batteries were Rhino model airplane packs weighing about 25 pounds. The only modifi cations made to the Gull 2000 airplane were the mounts for the batteries, controller, and motor. The electric ultralight's public debut was at the 2009 Arlington (Washing- ton) Fly-In. Mark fl ew several demonstration fl ights at the fl y- in, and then he had to replace a high-amperage connector that was causing a heating problem. The Gull 2000 had served its purpose as a test bed, but its endurance was less than hoped for. Mark decided to switch Gulls in midstream. The obvious candidate for an airframe more suited to electric fl ight was his single-seat Soaring Gull. Its longer wings (28 feet versus 20 feet on the Gull 2000), simi- lar empty weight, and stall speed meant the Soaring Gull would of er better overall ef ciency than the Gull 2000 with the elec- tric motor. Mark made the change and renamed it as the e-Gull and also experimented with dif erent motors. The brush-type Mark plugs the motor in to charge during AirVenture 2013. This is the Joby motor that resulted from Mark's collaborations with Thomas Sankel of Germany that's now produced by Joby Motors. It weighs 26 pounds, has a 20-kilowatt output and produces 27 hp. He will likely fl y this motor at AirVenture 2014. E A A E X P _ J u l y 1 4 . i n d d 2 1 EAAEXP_July14.indd 21 7 / 1 / 1 4 9 : 5 5 A M 7/1/14 9:55 AM