January 2014

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/247918

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Page 21 of 38

THE SPORT PANTHER ADDITIVE MANUFACTURING MAKING PARTS WITH 3D PRINTING, BY PAUL SALTER Additive manufacturing is a relatively new type of manufacturing that has been evolving over the last 15 years, and it promises to revolutionize manufacturing techniques. Current machining processes require the purchase of large pieces of material, and then everything that is not needed for the part you are making is cut away. This generates an enormous amount of scrap material. Additive manufacturing reverses this process and starts with material in either a powder or filament form and only places material where it is needed to form the part. This saves a great deal of material costs and allows complex items to be made almost as easily as hitting the print button on your computer, with little or no scrap. Large aerospace companies are starting to use additive manufacturing techniques using metal powders that are heated with a laser to form jet engine blades, rocket engine injectors, and other difficult-to-manufacture items. Unfortunately the equipment for additive manufacturing with metal is very expensive and currently starts at prices of $100,000 or more. Fortunately, another type of printer has emerged using plastic filament on spools. The filament is heated nearly to its melting point and deposited in layers using the same technology as CNC milling machines. As the material cools, it bonds to the surrounding material, forming the part. These printers are now available in kits that can be purchased and assembled for as little as $600 by a hobbyist. They are also available in pre-assembled versions starting around $1,000. Sport Performance Aviation has started to use one of these low-cost printers to manufacture some of the plastic parts for its folding-wing Panther aerobatic aircraft. These include an isolator used for the automatic connection of the fuel sender unit in the wing and for a fixture to make the assembly of the rudder easier. These parts have a honeycomb internal structure and are essentially hollow. This allows the rudder fixture to be manufactured using approximately half of the material used by conventional manufacturing techniques. The isolators and rudder fixture are only the beginning; there are plans to use this technology for other parts. Sport Performance Aviation is always looking for innovative engineering solutions along with inexpensive and practical manufacturing techniques. Looking at his dream not only as a fulfllment of his own ideas but also as a commercial kit from the start, he notes similarities between his Panther and other well-known kits. designed for 80 to 160 hp," Dan said. In addition to his favorite Corvair, the engine options include the Jabiru four- or six-cylinder engines, the AeroVee, O-200; and Lycoming O-233/235, O-320 for the Sport version, plus ULPower four- and six-cylinder engine. Other Panthers are currently under construction, including a tricycle LSA with a Continental O-200, a Jabiru 3300 LSA taildragger, and an O-320 taildragger Sport. Building the Panther should be on the easy side. In addition to a conscious efort to reduce parts count and include a jigwelded frame, all the machined parts are precisely made with CNC equipment; the 7075-T6 main gear is grooved for the brake lines; the sheet metal has matched holes. Builders can buy precut, prepunched, preformed, powder-coated forward fuselage kits. Though most of the sheet metal parts on the tail cone and fuselage are match-hole, some skin holes are necessary in final fitting. WHAT ABOUT FLYING? One airplane, the LSA taildragger version with a Corvair engine seen at Oshkosh 2013, and most recently seen flying at U.S. Sport Aviation Expo in Sebring, Florida, has completed flight testing. As tests were concluded, test parameters were widened until the design limits were all confirmed. "As of today (early December 2013), we have 80 hours on it and full positive-g aerobatic testing from 0 to 222 mph, with g-loads from -1.5 to +6, including deep stalls, spins, and aerobatic maneuvers," Dan said. "We have not been surprised." Dan said, "It spins, but you have to make it spin. Hands-of recovery takes about one turn; assisted, half that." So far, Dan's flying impressions tend to describe the Panther's flight characteristics "like a really light RV-4. The stick travel is long but crisp, and it's not twitchy. Long rudder travel gives a light feel there; it's easy to do full control-stop slips, with or without flaps." PRICING The firewall-aft kit sells for $11,500. A kit for the cowling, pre-welded engine mount, and bafing for the Corvair goes for $1,500, with prop and exhaust builder options. For more information, visit www.FlyWithSPA.com. The 3D "printer" that Sport Performance Aircraft uses to manufacture parts for the Panther. 22 Vol.3 No.1 / January 2014 Tim Kern is a private pilot and has written for more than 40 different aviation magazines. He was a key builder on two aircraft projects and has earned the title of Certified Aviation Manager from the NBAA. Photography courtesy of Sport Performance Aircraft

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