Radio Control Scale Aerobatics - 2011/02

128 MODEL AVIATION
I will give you a brief overview of
Aresti, examine the critical inputs in
performing this stunt, cover a general
aircraft setup to aid in flying this maneuver
consistently, and teach you about the
benefits of a throttle curve for precision
flight. Let’s get started!
The Maneuver: If you are new to the world
of Aerobatics, you may be unfamiliar with
Aresti. Count Jose Luis Aresti developed a
cataloged system that has turned into the FAI
aerobatic catalog of
maneuvers. To learn
more about Aresti
Also included in this column:
• Aresti language refresher
• Break down the figure
• Set a model up to perform
• Practice with an expert
•Wayne Mathews is in the
house
The 2011 sequences are up!
[jglezellis@comcast.net]
Radio Control Scale Aerobatics John Glezellis
Make sure that the distance from the center of the servo arm to
the ball link is the same as from the center of the hinge line to the
ball link that attaches the pushrod to the control surface. Both
ends must be equal in length to obtain a suitable ATV setting.
The Aresti diagram for this month’s maneuver includes multiple
segments. Familiarize yourself with the language of Aerobatics; you
will need to fully understand how to read Aresti at a competition.
THE 2011 INTERNATIONAL Miniature
Aerobatic Club (IMAC) sequences have
been posted. Rather than focus on an entire
sequence for a particular class, I will cover a
maneuver that contains elements you can
apply to similar variants; in particular,
maneuver seven from the Sportsman
division.
On the competition scene, different
aerobatic moves contain like components.
This month’s maneuver features positive pulls
to both a 45° up-line and another inside loop
segment, two points of a four-point roll, a half
roll, and inverted flight. Many components
happen quickly in a short period of time.
and how it applies to IMAC, please be sure
to visit the official IMAC Web site.
Many pilots use an Aresti symbol for a
specific figure. In every Aresti symbol the
start of a maneuver is shown with a large
dot, and the end of the maneuver is
indicated with a short line that is
perpendicular to the line of flight.
When the line of flight is shown, a solid
black line reveals positive-G flight, whereas
a dashed red line shows that the model is
under a negative-G load.
The figure for this month contains two
half-arched arrows, which tells us that they
are half rolls. However, one of the arched
arrows has a “2x4” above it; that tells us
that we need to perform two points of a
four-point roll. The second arched arrow
has nothing written on it, so it is a half roll.
Since you’ve just received your “crash
course” in Aresti, let’s get on with the
specifics.
Begin by orienting your aircraft parallel to
the runway. Pull to a 45° up-line with a nice,
Mike McConville with one of his
most recent designs: the Hangar
9 3.1m Sukhoi Su-26MM. A 2.5m
version is available with digital
Spektrum servos installed and
can be ready to fly in a day.
2x4
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February 2011 129
gradual radius. Show a brief line segment
and perform two points of a four-point
roll—roll the model to a knife-edge
attitude and show a brief hesitation, and
then roll the airplane to inverted—all
while on a 45° climb.
Show another brief line segment equal
to the first (the line after the pull to a 45°
climb), and then pull smoothly five-eighths
of a loop until your aircraft has attained
level, upright flight, and immediately
perform a half roll to inverted flight.
To ensure success in this maneuver,
and maneuvers in general, you need to
divide it into segments. You need to be
familiar with your model and the inputs
needed at a few different stages throughout
the stunt.
You must also be able to perform
inverted flight and four-point rolls and
hold 45° climbs with ease before you even
think about attempting this maneuver or a
similar stunt. Practice makes perfect, but
only when practice is performed in a
proper manner.
Aircraft Setup: If you have been an avid
reader of my columns, you are probably
well aware of the notion that I recommend
using flight modes throughout a flight. Too
many times I have seen a pilot fly a giantscale
Aerobatics model on only one rate:
high! It is in the competition pilot’s best
interest to employ flight modes, or at least
dual and/or triple rates.
I recommend that you use flight modes
so that only one switch is needed to
control all of your dual (or triple) rates. I
use the low rate setting for all precision
maneuvers, medium rate for snaps and
spins, and high rate for spins. I used the
following on a Hangar 9 Beast.
• Aileron: Low rate, 25°/30% exponential
(expo); medium rate, 35°/40% expo; high
rate, 40°/65% expo
• Elevator: Low rate, 15°/30% expo;
medium rate, 25°/45% expo; high rate,
40°/65% expo
• Rudder: Low rate, 35°/50% expo;
medium rate, 30°/55% expo; high rate,
40°/65% expo
I found that to perform this maneuver,
low rate values work great. This model is
precise, and enough control-surface
deflection is present to allow the maneuver
to be executed with utmost perfection in
addition to exponential, which softens the
airplane’s feel around neutral stick on the
aileron, rudder, and elevator.
Your aircraft should now be
programmed to your liking. Using the
preceding control throws and expo rates
might get you started on the right track,
but all flight setups are personal. If you
feel that your model is too sensitive or
relaxed in feel, make the necessary
adjustments to control throw and/or expo
settings.
To do this, start with the factorysupplied
control-throw values. If you think
that your airplane has too much throw on a
given surface (for example, the roll rate is
difficult for you to keep up with because it
is too fast), decrease the amount of control
throw.
If the roll rate is acceptable but you feel
that the aircraft is too sensitive and
corrections you give are immediately
shown, increase the amount of expo.
However, do not do so in large increments.
Add 5% increments and take note of how
it gradually changes the flight
characteristics of your model.
And notice that different radio
manufacturers use varying values of expo;
JR uses positive expo values and Futaba
uses negative values to make the center
stick input feel softer. For safety purposes,
check with the instruction manual of your
radio to ensure that you are making the
right change.
I am a strong advocate of using a
throttle curve. Let’s say that your model is
properly programmed, but you are not
content with how your engine responds
and you feel that its transition occurs
rapidly near 10%-40% of stick movement.
Check to ensure that your throttle’s
Adjustable Travel Volume (ATV) values
are similar for high and low throttle. If
they are not, the reaction time of the servo
will be nonlinear and you will not obtain a
linear feel in throttle transition. Simply,
your engine might be too slow or too quick
to respond when transitioning from idle
onward, etc.
I recommend that you default your
ATV for throttle to 100% for high and
low, make sure that no subtrim exists on
throttle, unfasten the throttle pushrod, and
turn your airplane and radio on. Go to
approximately 50% throttle stick and open
the carburetor roughly 50%.
Then fasten the throttle pushrod, and
make necessary mechanical adjustments to
ensure that no binding exists when the
throttle transitions from idle to maximum
power.
If you have done that properly and you
are still unsatisfied with the transition of
your engine via the throttle stick, you can
add points to the throttle curve. Many
radios differ, and this might be impossible
unless you have a high-end computer
system; look at the instruction manual.
I usually add a few points to my throttle
curve on the transition from 0%-60%.
Then I adjust the values for each point so
that I obtain a smooth transition.
Be sure to take advantage of the throttle
curve; it will help you add smoothness and
precision to your IMAC routine.
Putting It All Together: Now you have the
proper aircraft setup and a thorough
description of this maneuver. What’s next,
you ask? Let’s tie in everything you’ve
learned.
Since this is an end-box maneuver—
performed at the left or right side of the
field, depending on which way the
sequence direction began—make sure that
you are at your base altitude. Apply the
inputs I listed earlier, but take notice of the
following key areas.
1. Your model performs a gentle radius
into the maneuver at the start to define the
45° climb.
2. The 45° up-line is neither too
shallow nor too steep in angle.
3. Line segments both before and after
the two points of a four-point roll are equal
in length.
4. A gentle pull is performed to loop
the model back to upright, level flight
5. A half roll is performed immediately
when upright, and level flight is
established to roll the model to inverted.
6. Your entry and exit altitude are the
same.
7. No loss in heading occurs throughout
the maneuver.
Now you have learned about how to
decipher this maneuver in terms of Aresti;
you have been given the basic flight setup
required, inputs needed, and learned how
to perform this maneuver; and you have
learned about the benefits of a throttle
curve. When learning a maneuver, seek
help from a more experienced pilot if you
question any of your inputs or how you
can improve the presentation.
But seek advice from someone who
will give you the proper feedback.
Practicing a given maneuver the wrong
way is unsuccessful practice—and in that
event it will not matter how many gallons
of fuel you burn at the field.
Late-Breaking News: Congratulations to
Wayne Mathews on becoming the new
IMAC president. His participation and
support of the organization through the
years has been no secret, and his
assignment to the position seems not only
logical but also an act of providence.
Wayne has asked MA to help support
the IMAC Web site with tools to help new
pilots succeed. We’ll be posting them
along with archives of my column in PDF
form a bit at a time, so that people can
catch up or maybe send comments to me
on what they’d like to learn about in future
RC Scale Aerobatics columns.
Thank you for the support, and best
wishes to Wayne and everyone for a fun
and safe IMAC season!
Until next time ... MA
Sources:
International Miniature Aerobatic Club
www.mini-iac.com
Hangar 9
(800) 338-4639
www.hangar-9.com
JR
(800) 338-4639
www.jrradios.com
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