Radio Control Pylon Racing - 2009/02

RACING IS INSTINCTIVE. No matter
what the contest, be it Tonka trucks, tuner
cars, or Reno, racing is something that
almost anyone can relate to and enjoy.
What I’ve written about in this column
so far is a lot about the sanctioned AMA
events that are popular across the country.
However, other RC racing interests are
strongly gaining in popularity.
The Unlimited Scale Racing Association
(USRA) is one with a colorful and
passionate heritage. The 2006 racing season
was one of the most popular, and MA’s
coverage of the Rumble Over Rantoul
received numerous positive letters and
comments.
MA Editor Michael Ramsey wanted to
share his experience at a recent Giant Scale
racing event held at El Mirage, California,
called the Frightfully Fast Bash. Here he is
to tell you more.
I was given the generous opportunity to not
only travel and cover the 2008 USRA
Nationals, held Halloween weekend, but I
was also invited to participate in the
Sundowner class.
Every special interest has a basic
competition level, and, logically, it has to
include readily available equipment that is
versatile and affordable. The USRA body
decided that, for the time being, that entrylevel
class would focus its study of such an
entry class’s viability by adapting the
success of the 80-inch-wingspan Hangar 9
Sundowner ARF.
In the upper classes of USRA
competition, 1/3-scale models are flown. The
IMAA (International Miniature Aircraft
Association)-legal Sundowner is just a few
percent larger than 1/4 scale. This model can
start to look small on either end of the
1,800-foot, two-pole course, but its size is
popular with everyday RC pilots.
This class of racing was officially
introduced last year, with rules that
stipulated the exact engine required. The
effort was to make the Sundowner emulate
the upper classes, so the Evolution 35cc gas
engine was chosen.
Also included in this column:
• Inside tips for the Sundowner
Lite class
The event did attract a large number of
new racers to the USRA style of flying;
however, the stringent specifications proved
to be outside the ability of the airplane’s
design and many newer pilots’ skill level.
The 35cc engine put the Sundowner at
such a high wing loading that tight turns
around the pylon were difficult to perform
without the model high-speed stalling
through them; trim and setup were critical.
Most airplanes weighed close to 16 pounds,
which also made them difficult to land. And,
overall, the expected 135 mph speed was
never realized.
Live and learn, and because less than
four USRA events are held each year, time
is accordingly necessary for a new class to
find its comfort zone. The 2008 season
included Sundowner rules that were opened
way up and allowed the use of any engine
type as long as it was within the
manufacturer’s recommendations.
The use of any of the glow burners
available instantly dropped 2-3 pounds from
the airframe. This not only put the model in
a better wing-loading range, but it also
opened up the speed envelope. While a gaspowered
Sundowner could best do 110 mph
downwind, the glow-powered models were
grabbing course speeds of 125-135 and
turning corners like they were hooking the
pole with the inside wing.
Sundowner Tips: I set up my model with
the exact equipment that Hangar 9
recommended. Different stabilizer support
systems are available; one is hollow
aluminum and the other is solid steel. I used
the steel tubes.
I’m a fan of the four-stroke engine, so I
chose the Saito 1.80. I would also be flying
the model as a sport airplane, so this setup
fit in well with most fields’ noise standards.
For those competitors with unlimited
resources (also a racing necessity in the
upper classes), at El Mirage the YS 1.70
proved itself to be the lightest and strongest
power plant of all the available engines on
the market. It thrived on 45%-nitromethane
helicopter fuel and, with an APC 16 x 16
propeller, it could bite the air in bigger
chunks. This also proved to be the setup that
required a pilot’s diligence in flighttrimming.
As the Sundowner reaches top speed, its
control sensitivity heightens tremendously;
control-throw rate options and using
exponential seriously helped the model, not
only in pulling through the turns, but also in
managing entry and exit from them. After
all, what good is speed if the airplane can’t
be kept on the course?
On the heels of the YS setup were the
two-stroke engines—specifically the Moki
and Mark 2.10. The Mark’s popularity is
high, because its price and friendliness of
use are a long-standing tradition.
The Mark 2.10 appears to have great
potential. However, since the class isn’t
labeled “unlimited,” a propeller cap was
placed on it. An APC 17 x 12 is the only
legal propeller for that engine.
The Moki 1.80 is also a viable option. And
because it has no propeller restrictions, it’s
possible that this engine matched with a good
pilot could contend with the Moki 2.10- and
YS 1.70-equipped Sundowners. Racing is so
much fun that it’s worth flying no matter what
engine you use.
Four of the 23 Sundowner pilots at the
Frightfully Fast Bash used the Saito 1.80.
Early on, many of us were plagued with stock
muffler-retention issues. Because the engine
required the Saito 90° adapter to route the
stock muffler, that adapter’s threads run
parallel with the strongest axis of vibration.
After a series of Loctite experiments,
tightening when it was hot, and tightening
when it was cold, I finally resorted to
reinforcing the snug jam nuts with J.B. Weld.
Then the adapter broke and disappeared on
the next flight. Sheesh!
This torturous exercise led to my nowproven
love for the Slimline custom fourstroke
muffler line, which is available for
almost any four-banger on the market. Since I
installed the Slimline, I have not complained
once about an exhaust issue—and that’s more
of a relief than words can describe. The $90
investment is well worth every penny.
I was able to compensate for the heavier
Slimline muffler by moving my four-cell,
1500 mAh battery pack from above the tank
to just over the landing-gear plate.
A proper run-in of the Saito will assure
that the engine’s power will improve with
every run. Correct valve adjustment is also
important. After nearly a gallon of running on
12.5% helicopter fuel, my Saito was still
looking groovy on the inside—not polished
like its ring should have been. Nonetheless, I
stepped up the fuel to a 30%-nitro helicopter
blend.
An APC 15 x 12 proved to be a strong
propeller for the Sundowner. However, left
over from my 1.20-engine RC Aerobatics
days was an APC 14.4 x 12 propeller that was
nearly an ounce lighter and would let the
engine turn a bit faster.
Under the radar gun, my Sundowner was
clocked in a downwind pass at 132 mph and
did approximately 121 upwind. To say that
the smile on my face was big is an
understatement.
Around the simulated course, the
Sundowner could corner like it was on rails. I
found that the recommended low rate/
exponential settings for the elevator were
perfect for sport-flying and the high speeds
that the model was reaching on the course;
there was no high-speed stalling whatsoever.
High-rate elevator was tested early and
proved to be uncomfortable; therefore, I left it
turned off. (That’s an odd statement coming
from a huge fan of 3-D rate controls.) Lowrate
aileron was fine; however, I set it roughly
20% higher with 25% exponential so I could
roll out quickly in an emergency.
During the official races, many of my
Saito 1.80-user friends and I faced issues—
this time with our engines starving in the turns
once the fuel tank depleted past a certain
level. Most of us were stumped at this point.
What fuel and propeller choice we made had a
lot to do with when the engine would quit.
Some were satisfied with running the
needle at a slightly rich setting. It seemed
that my luck prevented this fix from being
the solution.
I was the only Saito user burning 30%
and my tried-and-true 14.4 x 12 propeller. I
was turning much higher rpm, which could
mean that my fuel demands were possibly
outside the capability of this sport engine’s
sensible and reliable design.
Some suggested that the tank was too
low, and they were certainly right. With a
sport propeller and sport fuel, the tank
position was fine, and I never had issues
while breaking in the airplane and engine.
When I began asking for every bit of power
from the engine, the tank placement became
more critical.
Trouble with the Sundowner is that to get
the tank higher, it needs to be moved back a
good 3 inches. The Saito loves to have the
tank as close to the carburetor as possible.
Moving the tank back helped to a point, but
the gravity-feed carburetor began to starve
once more when the fuel level got low again.
The solution, and the lightest option, was
installing a Perry N20 fuel pump from
Conley Precision Engines. As do the
Walbro-equipped gas engines used in the
Unlimited-class models that burn 80 ounces
inside six minutes, the Saito could finally
keep running through the course, because its
fuel feed with the N20 was more constant. I
actually didn’t solve my engine problems
until I got back home and rebuilt the fuel
system.
Everyone was so helpful at the event in
California. I can’t thank everybody enough
for making my first experience in Giant Scale
racing a memorable one.
I’m looking forward to seeing everyone
again this coming June in Ashtabula, Ohio,
for a more successful attempt at what I’ve
found to be a seriously fun and addictive part
of aeromodeling. MA
Sources:
USRA
www.usrainfo.org
Hangar 9
(217) 352-1913
www.hangar-9.com
YS Engines
(775) 267-9252
www.yspartsandservice.com
Global Hobby Distributors
(714) 963-0329
www.globalhobby.com
Slimline Products
(480) 967-5053
www.slimlineproducts.com
Conley Precision Engines
(630) 858-3160
www.conleyprecision.com
140 MODEL AVIATION
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