The author converted a Midwest Cougar Super
Stunter to RC. He added 2 inches to the wing to
make it 56 inches in length.
Why would anyone want to make a Control Line (CL) Aerobatics-to-RC conversion? For me it was the challenge, and because I have experience in both disciplines, it wasn’t too difficult.
If you are a builder, a reason might be that there are not too many kits available
anymore unless you spend your time mining eBay. However, a variety of CL
Aerobatics or Stunt kits is available thanks to the Builder of the Model Rule and
John Brodak’s dedication to keeping CL alive. There are also kits by such suppliers as
Sig Manufacturing Co. and RSM Distribution. Another reason is that there are a lot
of good-looking Stunt aircraft!
This conversion business is not new to me. I converted a Midwest Panther Stunt
model for RC in 1973, using an early Citizenship proportional radio with kit-built
World Engines S-4a servos. They were small servos for their day, equivalent to
today’s standard servo. To make it work I had to cut holes in the W- 1 ribs to mount
the servos with only the output of the servo protruding into the fuselage radio bay.
The Panther had been built and was half painted when I moved from Pennsylvania
to Utah and sold it to my friend, Pete Carr. Pete finished it and flew it for six years.
I’ve had a kit of the Panther’s sister model, the Cougar, and I wanted it to be an RC
conversion as well because it has better geometry than the Panther.
Many will remember the RC Nobler. That was more a redesign than a conversion.
I wanted my Cougar to still look like an authentic Cougar Stunt aircraft. Today’s
small radios make that goal obtainable. Let’s go to work!
Change 1: Equal Wing Panels
This is presented first because, other
than creating ailerons from the flaps,
this is the only indespensible conversion.
Stunt models almost always have
unequal wing panels to eliminate extra
lift in the outboard wing caused by
that panel moving faster because of
the circular flight path. There is also a
need for more lift in the inner panel
because of the effects of the control
lines. Most CL Stunt models have some
combination of outboard tip weight and
wing imbalance to correct these forces.
Figure 1 represents a typical Stunt
wing. The outboard wing is usually 1 to
2 inches shorter. Some wings, such as
those on the Veco Thunderbird, have
by Dan Grotzinger
39 Model Aviation AUGUS T 2015 www.ModelAviation.com