Radio Control Combat - 2008/09

120 MODEL AVIATION
Also included in this column:
• Lee Liddle’s SSC Falcon
• Setting up an O.S. .15 LA
engine
• Hill Top Flyers’ Easter SSC
event
Why SSC has become the Combat of choice
[[email protected]]
Radio Control Combat Don Grissom
Club judges at the
Hill Top Flyers’
Easter SSC contest
made it special and
gave the pilots
extra time needed
to work on their
aircraft.
Left: A close-up of the O.S. 15LA engine shows
that the needle valve has been relocated to the
engine mount to keep it from breaking off.
Below: Lee Liddle of Texas designed the
author’s SSC Falcon. Most of the parts came
from a local hardware or home-improvement
store.
THIS YEAR HAS been great for me! I have
enjoyed getting a chance to fly some types of
RC Combat other than Slow Survivable
(SSC). The 2548 Zero I flew in Florida has
done well, and I have some Open B Avengers
I plan to fly in the Nats in Muncie, Indiana.
But when it comes to my favorite type of
Combat, I enjoy SSC the most.
When getting started this year, I decided to
rebuild all my SSC airplanes. Many people
wonder why you would want to spend more
money on models when you can just repair
them. With SSC, it is important to keep the
airplanes as close as you can to the 2-pound,
6-ounce minimum weight.
I fly an SSC Falcon designed by Lee
Liddle of Texas. It’s a simple model to build
and inexpensive, since most of the parts come
from the local hardware or homeimprovement
store.
The Falcon’s wing is made from 25-pound
foam shaped with a hot-wire cutter. A 2-inchthick
4 x 8-inch piece of foam is enough
material to make as many as 12 wings. Some
people use EPP foam, which has a spongier
feel to it, for the LE. This can sometimes lead
to less damage, but occasionally there are
issues with obtaining EPP foam.
The main spar is made from 1/4 basswood
that I cut with a band saw. The blocks in front
of and behind the spar are also basswood that
has been cut using a scroll saw. One of the
things I have found useful when assembling
any wings is to have a smooth surface where
you can lay the wing for a day to dry.
I use a polyurethane glue and bidirectional
tape to assemble the wing. I apply the tape to
the backside of the wing with the spars in
place and glue the LE and then the TE to the
spar. Once they are glued together, I place
another piece of tape on the top side of both
wings before gluing the halves of each
together.
While the parts are “green,” I lay them up
on the floor overnight to dry. A good solution
to keep your wing straight is to use Ziploc
bags filled with sand to hold them down while
they dry. Why do I use the floor? Because it’s
typically flat, but you should check yours
beforehand to make sure. Also, the moisture
in the air is denser on the floor, and water is
the catalyst that helps the polyurethane glue
cure properly.
The engine mount is made from a plastic
cutting board. To cut it to shape, I use a scroll
saw with a plastic cutting blade. You do not
cut it at high speeds, because it will cause the
material to melt. It is a good idea to make
additional engine mounts since they are the
most likely parts to break in a crash.
To bring the weight up to the minimum
limit, I use standard-size servos as well as a 4-
ounce fuel tank that will be mounted in the
wing. The covering is 2.2mm color-coding
tape that is available from Fast Pack or Uline.
The most important part of any flying
wing is the balance, which for this airplane is
located directly on the spar. To adjust the
balance, I make additional screw holes in the
mount so the engine can be moved forward
and back.
Preparing an engine for Combat can be easy
if you do some basic things before your first
contest. The most common engine used is an
O.S. 15LA. For cost and performance, it tends
to be the best for SSC.
The first thing you should do when you
take the engine out of the box is seal the
backplate. The .15 LA uses a plastic backplate
that can leak because of the pressure it is put
under.
Some people use a gasket sealer, but I find
that the best sealer is plumber’s tape. You can
wrap it around the backplate just in front of the screws to get a good seal. This allows you
to replace it easily in case of a leak. You can
purchase a metal backplate, but I found that
the plastic one works fine.
The next thing you should do is cut the
needle valve away from the backplate and
mount it in another location. (It will
inevitably break off anyway.) If you prefer
the stock mount, make a small cut using a
Dremel tool that would allow it to break
cleanly, leaving the backplate intact after a
sudden impact.
You will find that the muffler will
occasionally come loose, so I recommend
that you replace the bolts with socket-head
bolts. The correct size is 2.5mm x 25mm.
At this point, you are ready to break in the
engine. I normally use a 6 x 3 propeller from
Master Airscrew. You can also use an 8 x 3
Combat propeller and cut 1 inch off each end,
but that would require balancing it correctly.
Start the engine and lean it to the point
where it is running at 90% of peak power
(rpm). Run it for 30 seconds and then shut it
off and let it cool to the touch. This normally
takes approximately five minutes.
This process heats the cylinder so it
expands. This will keep the interference fit to
its minimum, preventing undesirable wear on
the piston and cylinder. It also ensures that
the crankpin-to-connecting rod fit is started.
Finally, it relieves stresses in the cast cylinder
by getting it hot and letting it cool. Repeat
this process six times.
After the short runs, make four threeminute
runs, pinching the fuel line to get peak
rpm once every 30 seconds. Once you have
completed these steps, you are ready for the
first flight.
These are only the basics of setting up the
O.S. 15LA. For more complete information,
visit the Georgia RC Aircraft Combat Web
site.
This year, the club I belong to, the Hill Top
Flyers, had its SSC contest Easter weekend in
March. Six pilots showed up at this smallerthan-
usual contest. Bob Loescher of Ohio,
Chris Quinn of Tennessee, and Chris
Handegard of Florida attended.
Since we were all on different
frequencies, we did “all up” at the same time.
We had club judges, which made for a
relaxing day. It is nice to go to a contest
where there are club judges to help give us
some time to work on the airplanes.
CD Don Pruitt did a great job of directing
the event and giving us the time we needed to
get ready so everyone’s models could make it
into the air. Chris Handegard ended up the
winner even after starting with a -60 on the
first round. He ended up with 1,904 points.
Second went to Wayne Voyles, and third
went to Chris Quinn. I came in fourth place to
end up with the last trophy for the day. MA
Sources:
Georgia RC Aircraft Combat
www.georgiacombat.com
Hill Top Flyers
www.hilltopflyers.com