The author’s new electric-powered Combat model weighs 510 grams ready-to-fly.
Greg Wojtecki’s electric-powered Bosta flies
on 52-foot, 0.015-inch lines at a speed of
approximately 25 seconds for 10 laps.
Side projects for the “off-peak” season
by Mark Rudner
rudner@mit.edu
This is the last column that I’ll write this year during the “off-peak” season (it’s now early February), so
it seemed appropriate to dedicate some
space to Combat-related side projects.
I refer to this time as “off peak” because
“off season” would imply that flying has
stopped. I hope that many of you still
manage to fly throughout the winter
months.
It’s been a long time since I last wrote
about developments in the world of
electric-powered Control Line (CL)
Combat. This is not because of a lack of
activity, but rather because of the large
volume of other topics to cover. I’ll now
give an update on some developments
coming from Denmark and the US.
When I first started seriously
experimenting with electric power for
CL Combat, I retrofitted an old-style, 2008 vintage F2D model to hold a LiPo
battery, ESC, and radio receiver. For the front end, I modified a set of F2D engine
mounts to allow the electric motor to be fitted onto the existing mount block.
This was my first attempt, so I had little idea what would be the most efficient
and lightest way to get all components onboard and in position. My most important
goal was to get the model in the air and to start collecting data. One of my key
targets, however, was to put together a setup that could match the performance of a
top-of-the-line F2D model—even if only for a minute.
For a first attempt, that setup worked well and taught me many valuable
lessons. However, the model was heavy. Throughout the variety of battery and
motor combinations that I tried, the total takeoff weight ranged from 550 to 610
grams. For comparison, a decent ready-to-fly F2D model—including a full tank
of fuel—generally weighs between 500 and 520 grams. Although some of the
combinations that I tried had great power, there was a huge weight penalty that hurt
maneuverability.
After toying with the original electric model for some time, it eventually
became clear that I would need to start over and build a new airplane to
make significant progress.
With many things going on and an intense F2D schedule to follow,
I lacked the motivation to start anew. One day I let one of my
club members take a turn flying the model, and after
a wild ride, he planted it solidly in the mud. The
aircraft was badly damaged and it was the best
thing that ever happened to it.
The broken model lay dormant in my shop for
some time, until my dad came to visit before the
Danish World Cup in May 2015. In anticipation
of the electric Combat event to be held there,
we took one of my relatively modern Riga F2D
retrofitted it for the battery and ESC in
an entirely new way.
When preparing the new model, I
aimed to minimize weight as much as
possible. We tailored the modifications
directly toward the lightest of the high-powered motors that I had on hand (a
high-revving NTM Prop Drive 28-36
3,000 Kv motor from HobbyKing).
This motor weighs approximately
87 grams and can turn
a standard F2D
119 Model Aviation MAY 2016
www.ModelAviation.com
CONTROL LINE COMBAT
