PHOTOS: BONNIE SIMPERS
B&V 212 awaits judging on top of its documentation (at left). The electrical system (above) of the ducted fan Blohm and Voss P. 212.03 is not as easy to get to as the BF2C.
Blohm and Voss P. 212.03, is again a model of a proposed design that garnered 30 bonus points. I’ll let him describe it. “This was my second technology demonstrator, the first a Ta-183 Huckebein in ’03. I’d been developing EDF systems to replace the Rapier standard motor. That was accomplished several years ago with max thrust to spare. It has always maxed its competition flights. On its first competition flight, the Spring of ’06, it caught a thermal and was last seen at 5 minutes (I have this flight on video). “It was found in a corn field after many hours of searching and continued to be my test, sport and competition model until this year. It flew away on its final flight at this year’s Nats. It has had many different mo- tor and impeller combinations.
“At last flight, it used a fully fabricated
29mm fan unit. Housing was paper, balsa strip and CyA construction. The impeller was four blades at 40-degree angles with twist made from a Jello cup with balsa discs for the hub. Motor was a Hobby King Turnigy 1015 brushless turning 85,000 rpm at launch. The fan unit weighs about 7 grams, producing 45 grams static thrust initially, dropping to 40 grams which holds for the 2-minute run. “The rest of the system is twin Hyperion
120/25C Li-Pos in series (7 grams total), YGE 4-amp brushless ESC (3.6 grams), and a KP controller (1.1 grams).”
The flying weight is 50 grams on this 10- inch span model. It flies fast; Martin’s aim was to replicate Rapier type flight. FAC rules allow two models to be entered in any timed event but only allow the highest scor- ing model to count, the other is eliminated. Martin’s second model, a Blohm and Voss P. 208.03, would have been fifth. He really likes those Luftwaffe proposed designs. Tom Hallman is another master modeler, but not an expert at electric power, so I de- signed the electric system for his DH-2. As a pusher bipe it rated 20 bonus points. The mod- el started as a rubber job, then went to CO2 and is now electric. This draggy bird needs a fair amount of power. The motor is a KR2 4.2:1 geared M 20 driving a four-blade 3.75-inch di- ameter prop. This 2004 motor is still available from
http://www.kenwaymicroflight.com. One of my Pico timers and a 200 mAh Li-Po round out the system. Flying weight is 27 grams for this 13-inch span bipe.
The DH-2 has been flying with electric power for several years and Tom was using some older batteries. On his first flight he found the battery didn’t give him the usual
max flight time, dropping him to third. I checked out his batteries and found the bat- tery has lost its capacity over the years. That motor swinging a four-blade prop draws a bit of current. A Li-Po will lose about fifty percent of its amp hour capacity if it is left fully charged for a year. Note to fliers: use a fresh battery for a big contest. Derek Knight, from the K of KP Aero
http://www.kpaero.com, is another master modeler from the UK. His 24-inch Tiger Moth weighs 135 grams and rated 15 bonus points as a biplane. As he tells it. “It was first built in 1987 and has had a hard life since. There have been at least three sets of bottom wings and two sets of top wings. It is on its third fin and second tailplane and the rear fuselage and undercarriage have been rebuilt. The wheels and front fuselage are reasonably original excepting the cowling which becomes damaged every time it is flown indoors with those nasty chairs and hard walls.
“During its lifetime it has won the Indoor Nationals as an electric model and at one time as a rubber model. I made a gearbox that, given the correct rubber, weighed no more than the original KP01 that was fitted and gave the same rpm and duration.
PHOTO: DEREK KNIGHT
Derek Knight’s brushless power system (above left) for the Tiger Moth. Derek’s colorful DH-82 Tiger Moth (above right) awaits judging on top of its
FLYING MODELS
PHOTO: DAN DRISCOLL
documentation. The model, originally built in 1987, has had an interesting and somewhat hard life. See the text for a fuller explanation.
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