Radio Control Pylon Racing - 2010/10

120 MODEL AVIATION
in the fiberglass, but you need the resin to turn
the fiberglass from cloth to a stiff composite.
I glued the V-tail into the fuselage to help
strengthen this known weak area. I removed
the plywood cap from the center-section of the
V-tail with a 3/8-inch-wide wood chisel, to
allow for the standard 3/32-inch shim required
under the TE to get the V-tail incidence
correct.
If you don’t shim the TE, the Viper will
carry a substantial amount of up-elevator trim
during flight. I also trimmed approximately 1
inch off of the V-tail tips and rounded them to
match the shape of the wingtips.
I fiberglassed the V-tail with 3/4-ounce
cloth, top and bottom. Before that, I tackglued,
with thin CA, the elevators to the V-tail
assembly and sanded down the LE and TE
ridges.
The bevel in the factory elevators
fills with resin during the fiberglass
process. It can be
challenging to cut off.
The factory
aluminum wing bolts
have a tendency to back
out during flight. I
bolted the wing to the
I HAVE RACED the Great Planes Viper 500
ARF in local Sport Quickie (AMA event 424)
contests for approximately three seasons. I
recently purchased a Viper 500 Ready-to-
Cover (RTC) version for a Sport Quickie
backup and eventual use in the evolving Sport
Jett Quickee 500 class.
I was impressed with the Viper RTC
package and construction. It comes ready for
strengthening, meaning there is no reinforcing
fiberglass, as on the ARF version.
To describe the materials used for
reinforcement, I will start with the nose of the
model and work my way back. The epoxy
strengtheners and fillers I will describe were
bought from Aerospace Composites and
Tower Hobbies.
In the nose, before installing the top hatch,
I used epoxy and chopped carbon fiber. (I
used Zap Z-Poxy Finishing Resin in all of the
epoxy mixtures I will describe.) The goal is to
wet the chopped carbon enough to securely
bond it to the firewall and fuselage sides.
This mixture can be challenging to
position. The best method is to wet your
fingertip (with isopropyl alcohol) and move
the material to form the fillets.
While the nose cured, I moved to the wing.
The aileron torque rods installed in the wing
were not tight. I used an X-Acto knife to
remove 1/8 x 3/8-inch pieces of balsa, to expose
the torque rod near the center-section and the
aileron intersection.
I used a small brush to apply car wax to
the torque rod (I’m told that Vaseline works
well too), and then I put in an epoxy/
microballoons/cabosil mixture to fill in the
opening down to the torque rod. This creates
bushings at both ends of the tube and
minimizes slop.
Cabosil, sometimes called Aerosil, is a
thickening additive that helps keep the epoxy
from flowing. The microballoon mixture
works well for areas where strength is
noncritical and sanding might be required.
I fiberglassed the wing with 3/4-ounce
cloth, top and bottom. The top pattern was
approximately 12 inches wide at the LE,
tapering back to 6 inches wide at the TE. The
bottom piece of cloth was a constant 8 inches
in width.
Spread the finishing resin with an old
credit card or hotel-room key, and try to pull
off as much resin as possible. The strength is
Great Planes Viper 500: ARF vs. RTC
[[email protected]]
Radio Control Pylon Racing Aaron “AJ” Seaholm
Above: A Judgeman mini display in use at
the late-June Bloomington IL event. This
race-management system greatly improves
the competition experience for racers and
spectators.
Left: Mike Langlois is the owner, builder,
and sparkplug behind Old Julian Airport
raceway, featured in this month’s “Salute
to Local Racers” section.
Also included in this column:
• Judgeman system
• Old Julian Airport races
AJ’s Great
Planes Viper
RTC is personalized
from firewall to tail post.
He describes the assembly
and improvement techniques in this
month’s column.
The Viper is available
in RTC and ARF
versions. AJ ’s tips
apply to whichever
you choose for either
racing or sport-flying.
10sig4.QXD_00MSTRPG.QXD 8/20/10 12:41 PM Page 120
fuselage with one factory bolt at the LE and
TE, diagonal from one another. Then I
popped out the wing hold-down blind nuts
and tapped the holes for a 1/4-20 bolt.
After countersinking the holes in the
wing, I installed the 1/4-20 nylon flat-head
bolts and then repeated the process on the
final two holes. I ran thin CA onto the
threads of the fuselage wing hold-downs
and then retapped to improve thread
durability.
After installing the V-tail servos, I cut an
opening into the factory hatch located aft of
the wing. I measured in approximately 3/8
inch from the sides and approximately 3
inches in length. I cut this new hatch
opening from the stock plywood hatch with
a utility knife.
I used small triangular-shaped 1/64
plywood pieces at the corners, to allow the
new hatch to sit in place. With the wing
installed, I glued the revamped plywood
hatch assembly to the fuselage with medium
CA.
Next comes potting the wing. I placed
masking tape on the wing and covered the
tape with car wax. I prefer Johnson’s Paste
Wax. The tape provides tolerance and keeps
the epoxy potting material from getting on
the wing.
I mixed a batch of epoxy/microballoons/
cabosil to the consistency of peanut butter. I
smeared the mixture on the wing saddle,
installed the wing, and used a Popsicle stick
to scrape off the excess material.
Then I replaced the balsa tank hatch with
1/8 light plywood. I glued 1/4 x 1/4 triangle
stock to the top of the fuselage sides and
then used epoxy and milled fiberglass to
secure the light plywood hatch to the top of
the fuselage.
This is a good time to create a thin fillet
of epoxy and milled fiberglass along the
bottom sheeting and fuselage side joint and
landing gear block joints under the wing
opening.
I glued the tail in with epoxy and milled
fiberglass. If you do this, don’t forget the
3/32 TE shim. I used a piece of balsa on top
of the V-tail to blend into the fuselage.
I fiberglassed the fuselage with 3/4-
ounce cloth, sanded with 220-grit paper,
applied a thin second coat of epoxy, and
sanded again with 220. Then I used
Sheetrock spackling in my hand, thinned
with water, to rub down the entire
fuselage. I sanded that off with 220-grit
paper and then with 320 grit.
I shot automotive urethane clear coat on
the fuselage, using an HVLP (high-velocity,
low-pressure) spray gun. I’ve been using
PPG DC3000 urethane clear on my Quarter
40s, so that is what I used on this project.
I used the thinned spackling mixture on
the wing as well. I sanded the filler off with
220-grit paper, followed by 320. I used
UltraCote to cover the wing and vinyl
graphics to doll it up.
After all of that mixing, spreading,
covering, and sanding, which is better: the
ARF or the RTC?
From a feel standpoint, the fiberglassed
RTC Viper flew more locked in on the
racecourse. I used the ARF at a Wichita,
Kansas, race in early June. Temperatures
were in the upper 90s and the wind was
blowing at approximately 15 mph.
I raced the RTC version with the same
Thunder Tiger Pro .40 engine as at Wichita
the second day in Bloomington, Illinois, in
late June. Conditions in Bloomington were
in the upper 80s with a similar roughly 15
mph gusty wind.
My best time in Wichita with the ARF
was 1:23.88. In Bloomington my best time
was a 1:23.66 with the RTC.
So there doesn’t seem to be a huge
advantage for the extra work involved, but I
hope the durability of the fiberglassed RTC
will pay off in the long run. The landing gear
block and firewall loosened in the ARF after
a couple of races.
The Judgeman RC Pylon system is the
brainchild of Hank Kauffman of Canada.
Jim Allen, Tom Scott, Stan Douglass, Hank,
and others have invested huge amounts of
time designing and refining this system.
The simplest description for the
Judgeman is a race-management system that
simplifies officiating for the course worker.
The digital displays and laptop computer are
connected by a 2.4 GHz wireless signal.
Kansas City Radio Control (KCRC)
purchased an assembled system from Tom
Scott and the Can-Am Pylon Society in the
winter of 2009. The KCRC system has boxes
for the Pylon 1/2/3 judges that allow for
quick cut signaling with the flip of a switch.
A large display for the pilots and callers
makes it easy to determine which lap it is, if
a cut has been posted, and where a cut has
been posted, and it provides a consistent
start-up and takeoff sequence for the start of
a heat.
The small display allows lap counters to
see that their laps have registered and the
crowd to see all the details of a heat. The
Judgeman system tremendously improves
the racing and spectator experience.
Salute to Local Racers: The first Pylon race
of 2010 was held at Old Julian Airport
raceway in Julian, North Carolina, May 1-2.
By all accounts it was a huge success, thanks
to the organization and dedication of the
facility owner and builder, Mike Langlois.
He has set up a first-class operation with
golf carts and tractor trailer to carry racers,
callers, and aircraft to and from the flightline.
Everything ran like clockwork as a result of
exceptional planning and organization.
Several racers made the trek from across
the country, with participants from as far
away as California, Maryland, Tennessee, and
Florida.
Event staff and course workers did a great
job and withstood the effects of the heat to
hold a well-run event. All course-worker
positions were well equipped with sun
shading and safety barriers. Safety is a
primary focus during an RC Pylon event, and
Mike’s attention to this was apparent.
Food and refreshments were available
both days, handled by Mabel Langlois and her
fine groups of cooks and preparers. Saturday
night was especially nice; Mabel served North
Carolina barbecue, which the racers ate under
the shade of old pecan trees near the pit area.
This exceptional meal provided time for
racers and workers to wind down, make new
friends, and recap after an exciting day of
competition. Good times, good food, and great
racing are the essence of RC Pylon.
If you are ever in North Carolina, check out
the Old Julian Airport or make plans to attend
the next event that will be held there. MA
Sources:
Great Planes
(800) 637-7660
www.greatplanes.com
Aerospace Composites
(925) 443-5900
www.acp-composites.com
Tower Hobbies
(800) 637-6050
www.towerhobbies.com
ZAP
www.zapglue.com
Old Julian Airport
www.oldjulianairport.com
National Miniature Pylon Racing Association
www.nmpra.org