R/CAerobatics Last month’s column introduced the Pro-
ject Pattern Redux series that will formally start next month. Model aircraft star of the series will be the Europa Pro LT.
and the already 2-meter long “yard dart” de- signs morphed into larger volume fuselages (like the EMC2). The larger fuselages more easily completed rolling maneuvers and the slowly increasing amount of integrated loop/roll maneuvers found in the FAI sched- ules. The once massive fuselage volume of the EMC2 rapidly became average amid the designs of the day including the Angels Shadow, Hydeout, Smaragd, and Synergy. While the FAI schedules continued to challenge airplane designers with increas- ingly difficult combinations of integrated loop/roll maneuvers, rolling circles, and snap roll/roll combinations, the biggest change to the Pattern landscape came from a new technological development. Of course I am alluding to electric power, which truly became viable for Pattern with the develop- ment of lithium polymer (Li-Po) batteries. As masterminded by Sean Plummer (Aero-Model, Hacker USA), Jason Shulman caused quite a stir when he flew an electric powered Rhapsody in the 2003 World Cham- pions, after qualifying for the US Team fly- ing an OS 160 EFI in the model. The Rhapsody used a 6.7:1 geared Hack-
A
er C50-14XL, Jeti electronic speed control (ESC), and Thunder Power Li-Pos to spin an APC 22–12E at approximately 5,600 rpm. The plane was right up against the weight limit, needing nearly 3.25 pounds of Li-Pos in 10S3P 6300 mAh configuration to safely provide peak power bursts needed in verti- cal climbs. Peak power output was just about 2,000 watts. In the mid 2000s, the FAI schedules con-
tinued to push aircraft design with in- creased numbers of snap rolls, more intri- cate integrated loop/roll maneuvers, and demands on knife edge flight (such as knife edge loops). Even though these maneuvers were primarily found in the finals sequences and list of maneuvers for the unknown ma-
s the larger unlimited displace- ment engines became common place, designers predictably proved the rule makers wrong,
by dave lockhart You can reach Dave Lockhart, via e-mail at
davel322@comcast.net
PHOTOGRAPHY: DAVE LOCKHART
Representative of 60 2C turnaround era, the Dash Fivemeasured 63 inches long, with a 70-inch wing span, 810 square inches, and 7.5 pounds. Several years after the 120 4C was allowed, the Prophecy was representative; much longer at 78 inches, and slightly larger wing at 74-inch wing span, 950 square inches, and 9.75 pounds.
neuvers (flown as part of the finals), the top designers and pilots designed planes for the highest levels of competition. Wing areas decreased slightly to increase
wing loading for clean snap rolls. Existing de- signs began to sprout a variety of aerody- namic devices designed to control airflow over the fuselage at high angles of attack in yaw. The modern shift to such devices was trig-
gered by the use of a “T” canalizer by multi- time World Champion Christophe Paysant Le Roux on his Oxalys at the 2005 WC. Fuselage side area increased, and shifted forward to improve knife edge performance. As the knife edge performance increased, yaw stability was compromised on many de- signs, leading to various strakes, fins, and reflexed rudder trailing edges in an effort to find the best balance of knife edge power and yaw stability. Anhedral stabilizers are once again common; aiding in the smooth translation of yaw/pitch angles during inte- grated loop/roll maneuvers on some designs. The 2005 WC was the debut of the YS 1.70
DZ (in limited numbers), and with further refinements, the 1.70 ultimately put YS solidly back at the top of the heap of inter- nal combustion (IC) engines. During that same time period, electrics were advancing at a prodigious rate, rapidly mounting a
threat to YS. I made the switch (from the Webra 1.60 MC) to electric in 2006, as I be- lieved (as did many others) the days of IC engines (reduced to YS for all practical pur- poses) in the Pattern event were limited (barring further rule changes). Approaching the current day, electric se-
tups dramatically increased in performance and popularity while dropping substantially in price (arguably cheaper than IC, at com- parable power levels). The biggest improve- ments came primarily from advances in Li- Po batteries, but also from advances in brushless motors and the software in the electronic speed controls. The “average” electric setup in 2011 used a 20–13 to 21–14 prop spinning ~6,500 rpm using 10S1P 5000 mAh Li-Pos (weighing 40–45 ounces) with peak watts ranging from 2,500–3,000. The current state of the art 4C is the YS
The long slender fuselage of the Prophecy (circa 1998) gave way to larger volume fuselages like the Vivat (circa 2005) which were better suited for maneuvers with integrated looping/rolling elements and rolling circles. The added drag of the larger Vivatfuselage was easily overcome with a 2C Webra 160 MC, whereas in the era of the Prophecy, engines were limited to 1.20 cubic inches 4C. The Prophecywas also at the end of the era of retractable landing gear; fixed gear is now preferred and used on the majority of planes since the mid-2000s.
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1.75 DZ, with an optional CDI ignition sys- tem. The YS will run props as large as 20 inches ~6,500 rpm, and of course “unloads” to higher rpm in the air (electrics in practice do not see an rpm increase in the air). The abundance of power (electric or YS) has re- sulted in higher drag designs with increased fuselage volumes and thicker trailing edges, which allow slower downlines and more con- stant speed flying. Thus far, I have not mentioned the changes in aircraft construction since the days of “Baby Huey”. Through the 1980s, a number of small companies and cottage en- terprises produced basic Pattern kits, gener- ally consisting of a fiberglass fuselage, foam cores for the wings, stabs, rudder, and some basic plywood parts for firewall, wing, and landing gear mounts. A number of all-wood built-up kits were also available, most no- tably from MK and Yoshioka. ARC and ARF versions were very limited, but a few exist- ed, and the number gradually increased. The basic construction changed little if
any through the late 1990s, albeit, more at- tention was paid to weight savings measures through the use of lighter wood, less ply-
APRIL 2012
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