project pattern
L
Redux
ast month, Algis provided an overview of the construction of Yuri at RC-Composites. As previously noted, the aileron and elevator ser-
vos for Yuri were specified at the time of the construction order, such that the internal mounting structures could be properly sized to accept the servos. So, while Yuri is in transit crossing the “pond”, it is time to take a closer look at the options/requirements for equipment in a modern day Pattern aircraft. And perhaps just as importantly, where to get the latest and greatest goodies. Given the large number of equipment
choices available to the modern day Pattern pilot, it is quite difficult to have detailed knowledge of every item currently available. My knowledge is not limited to, but certain- ly biased based on the sponsorships/affilia- tions I have which include Horizon Hobby (JR and Spektrum), Castle Creations, Thun- der Power RC, NeuMotors, Central Hobbies, F3A Unlimited, Tech Aero Designs, and WistModels. Certainly I know the most about and favor offerings from these ven- dors, but they are not the only products available and suitable for the highest levels of competition. I’ve included a list of the components I se-
lected to prepare Yuri for flight, a list of sup- pliers for Pattern equipment, and then some of my thoughts as to the pros/cons of the suitable Pattern equipment available today. Starting with the powerplant, the basic
initial choice is between electric, glow, or gas. Yes, there are some gasoline fueled en- gine options (DLE, Mintor, OS, Syssa, and ZDZ) that should be able to provide suitable performance (with appropriate soft mount and exhaust systems). However, I’ve yet to see such a setup used successfully at a top level of competition, so I’ll omit this option from further discussion. Moving on to the “glow” option, the choic-
es have essentially dwindled to the OS FS- 200S and the YS 175DZ, the latter being far more popular and available with an ignition system (while retaining alcohol/oil mix for fuel). While dwindling in popularity, the YS option is as competitive as ever, taking first (Christophe Paysant LeRoux) and second (Tetsuo Onda) places at the 2011 F3A World Championships. Initial investment costs (approximately $1,200) and operating costs (fuel at $30 per gallon, vibration wear to air- frame, etc.) and a shrinking number of YS savvy pilots at the field are all contributing to the decreased use of YS (and other glow engines) in Pattern. A future installment of Project Pattern Redux will include a sidebar with specific details about the YS 175DZ. The favored powerplant for most Pattern
pilots is the electric variety. While the con- cept of electric powered Pattern planes has been around since the 1990s, it was not vi- able until lithium polymer (Li-Po) batteries surfaced in the world of R/C in the early 2000s. Jason Shulman was the first promi- nent pilot to use electric power, and did so with great success placing seventh at the
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2003 World Champi- onships. Granted, the system used by Jason was pushing the equipment (pri- marily the Li-Pos) to the ragged edge, but by 2006, electric power was truly vi- able for Pattern. At the 2011 US Nationals, electrics comprised approxi- mately 80% of the en- trants in the FAI and Masters classes. The “tipping” point ar- guably occurred in 2009, at which time electrics became ar- guably cheaper to source and operate, multiple setups had been proven, and the net competitive advantage of the glow/electric setups seemed to be a wash. The first decision
by dave lockhart with algirdas ungulaitis You can reach Dave Lockhart via e-mail at
davel322@comcast.net
PHOTO: DAVE LOCKHART
point when choosing an electric power- plant is the motor it- self, with the biggest decision being geared or direct drive (not synonymous with inrun- ner and outrunner). Geared motors suitable for Pattern are of the inrunner type, where the case and stationary windings surround the inner rotating magnetic core that is af- fixed to the motor shaft. The motor shaft ter- minates in a pinion gear which mates to a
Equipment for Yuri Motor: NeuMotors NEU-F3A-1
Electronic Speed Control: Castle Creations Phoenix ICE 2 HV 80
Motor battery: Thunder Power RC G6 Pro Lite 25C 5S 5000 mAh (2) Li-Po
Propeller: PT Models 22–12 carbon fiber
Motor mount: Merle Hyde NFR type softmount with tailring support
Receiver: JR 921
Aileron servos: JR 9411sa (one per aileron)
Elevator servos: JR 3517sa (one per elevator)
Rudder servo: JR 8711
Receiver Li-Pos: Thunder Power RC G6 Pro Lite 25C 2S 480 (2)
Receiver voltage regulators: Tech Aero Designs FlexReg PLR5-E (2)
The long known benefits of counter rotating propellers became much easier to realize with the arrival of suitable electric power systems. Mounted in Dave’s #2 Bravo, the Brenner Sharp designed “Contra Drive” is rapidly developing a following among Pattern devotees.
planetary gearbox affixed to the front of the motor housing. The typical gear ratio is 6.7:1.
Geared motors are generally more effi-
cient, have a broader torque curve, faster throttle response, and greater downline braking (less tendency to spool up and in- crease rpm). The dimensions of a typical in- runner motor (with gearbox) for pattern use are approximately 1.75 inches in diameter and 5 inches in length. The overall form fac- tor is well suited for installations in the slenderest of noses, but also requires mount- ing/support at both the front and back of the motor. The downsides of geared motors are that
the gearboxes require periodic maintenance (cleaning/regreasing) and the gearbox itself is an additional source of noise. The main- tenance is minimal; approximately one hour every 50 flights, and roller bearings may need to be replaced every 500 flights (give or take). The gearbox life can be extended and the noise can be reduced (by about 2 dB) with a good softmount. Direct drive motors, until very recently,
were of the outrunner type. With an out- runner, the magnets are attached to the out- er case which rotates about the stationary core, within which the windings are located. The output shaft passes through the core but is driven by the outer casing. The grow- ing popularity of outrunners is attributable to primarily two reasons; lower manufac- turing cost, and they naturally produce sub- stantial torque at relatively low rpm (mini- mizing the need for a gearbox). Very recently, new large diameter inrun-
JULY 2012
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