Radio Control Scale Aerobatics - 2010/06

So you’re putting together your first giant-scale aerobat …
June 2010 121
[[email protected]]
Radio Control Scale Aerobatics John Glezellis
Also included in this column:
• Servo synchronizers
• Multichannel radios make
setup as simple as possible
A model such as this Thunder Tiger 40% Katana can be completed without
servo synchronizers. This month’s column describes how.
John’s setup choice for a Hangar 9 Sukhoi
eliminated the need for servo synchronizers.
By using a nine-channel receiver with a nineplus-
channel transmitter, every servo has a
place.
On John’s 35% Katana, he activated the 4-
AILE feature on his JR 12X radio. Doing so
automatically assigned all aileron servos to
specific receiver ports. A similar function
can be performed with the Futaba 14MZ.
To activate two channels assigned to
slave functions, Aux 4 and Aux 5 channels
are inhibited in the Device Select menu
for the elevator and rudder.
Aux 4 has been selected as a mate for
elevator and Aux 5 as a mate for rudder.
The transmitter trim function is
automatically linked to the slave servos.
A fellow modeler who had just started assembling his first
giant Scale Aerobatics model recently asked me a few questions.
Specifically, he purchased his first 35% airplane and was concerned
about what radio system he should use. Moreover, he wanted to know
if his seven-channel radio would suffice or if he needed a system with
more channels.
This month I will share my experience with you, in hopes of
simplifying your life when it comes to computer radios and proper
aerobatic setup techniques. It is, and will always be, my goal to provide
you with the knowledge necessary to equip your airplane the best way
possible.
Let’s begin!
Question 1: Are servo synchronizers needed? If you have been
flying giant-scale models for sometime, you might be familiar with
the term “servo synchronizer” (such as the JR MatchBox and
Futaba’s MSA-10). Such devices allow the end user to gang as many
as four servos into a servo synchronizer, which is then plugged to
the receiver.
Then the end user can adjust the center and endpoint values of
each servo so that none bind against each other. In addition, a
separate power source can be plugged in to power a given channel
through a servo synchronizer.
Back to the question. If you want to use a seven-channel
system in your giant-scale aerobatic model, you might need to use
servo synchronizers if you are employing more than seven servos
within the airframe and want each servo to plug directly to the
receiver.
You may be asking, Why can’t I simply use a Y harness with a
servo reverser? This is a great question, but I do not recommend
06sig4.QXD_00MSTRPG.QXD 4/22/10 11:05 AM Page 121
After Wing Type has been selected and Aux
4 and 5 have been selected as mates for
elevator and rudder, reverse any specific
servo in the Reverse Switch function. The JR
12X automatically updates the name of each
slave channel; RAL2 is Right Aileron 2, LAL2
is Left Aileron 2, etc.
Changes can be made to the rudder servo
within the 12X Balance Function. Think of
it as multiple-point mix. These values
change how the rudder servo moves with
respect to the slaved servo.
After the two rudder servos were
programmed on the 35% Katana, the rudder
setup was completed by mechanically
adjusting the pull-pull cable to ensure that
the rudder surface was centered.
doing so. It does not always allow the user to
make independent adjustments on a given
servo.
Let’s say that you have two elevator
servos plugged into a Y harness, and one of
them is reversed. Since both servos are
plugged to the same port in the receiver—the
elevator port—if one adjustment is made in
either the subtrim or Adjustable Travel
Volume (ATV) functions, the modifications
will apply to both. By plugging each servo to
its own port, you can make independent
changes to each servo.
If your airplane has one servo per aileron,
two servos on the rudder, two servos on the
rudder, and a servo on the throttle, most
seven-channel systems will work (because
that is a total of seven servos). However, if
you have a 35% model with two servos per
aileron, two servos on the elevator, two
servos on the rudder, and a throttle servo,
you will need more channels.
The preceding shows the need for a ninechannel
radio. If you plan on having multiple
giant-scale Aerobatics models, I recommend
that you invest in a nine-channel, or more,
system so that you will not have to purchase
multiple servo synchronizers per airplane.
That brings me to the next question.
Question 2: What are the benefits of a radio
system with nine or more channels? It is said
that a picture is worth a thousand words, so
let me paint a picture in your mind to serve
as an example.
This past winter I built a 35% Katana
from Thunder Tiger. It has two aileron
servos per aileron, one servo per elevator
half, two servos on the rudder, a throttle
servo, and a choke servo.
As the aircraft is built, I am using a ninechannel
system with each servo plugged into
its own channel. However, if I want to use
smoke I will need another channel.
I can either purchase a servo
synchronizer for the Katana, as well as for
any other model built in this configuration,
or I can use a radio system with 10 or more
channels. By using a 12- or 14-channel radio
system with either a 12- or 14-channel
receiver, I can eliminate the need for servo
synchronizers.
Chances are that if you are building a
typical 40% aircraft, you do not need more
than 12 or 14 servos on a given airframe.
Although special conditions exist, this
scenario applies to the masses.
Let’s explore a few functions that are
common in most higher-end computer radio
systems. If your transmitter features different
wing types (some transmitters have a dual
aileron setup, some have a four-aileron
setup, and so on), activating a simple
program may allow you to make adjustments
for both the center and endpoints of a given
servo or servos. Some transmitters also
feature dual elevator setups.
If you have a nine-channel or more
computer radio, you might be able to eliminate
the need for servo synchronizers in general.
Consult the instruction manual that came with
your radio to see what mixing potential it has.
Let’s look at how I program my 35%
giant Scale Aerobatics models without using
servo synchronizers on my JR 12X. After
selecting a new airplane and naming it, I:
• Enter System Mode.
• Enter Wing Type.
• Change the Wing Type to Flaperon if I am
using two servos (one servo per half) or 4-
AILE if I am using two servos per aileron
half.
• Exit this program and enter DeviceSEL
(Device Select).
• Inhibit (INH) Aux 4 and Aux 5 and exit
this screen (if two servos are to be used on
both the elevator and rudder channels).
• Go back into Wing Type.
• Assign elevator (ELEV) to Aux 4.
• Assign rudder (RUDD) to Aux 5.
With those steps completed, it’s time to
adjust all servos within the 35% or 40%
model.
In the preceding example, four ports will
be assigned for all aileron servos and two
ports are automatically assigned for both the
elevator and rudder servos. Adjust center
and endpoints using the Sub Trim and ATV
functions or take advantage of the Balance
Function.
The end user can adjust multiple points
throughout the servo’s travel so it will not
bind with another servo throughout its
movement. No accessories other than the
typical servo lead extensions are required.
However, if you are not using a JR 12X,
or a radio that is capable of automatically
assigning multiple servos to a given function,
explore your system’s programmable mixes.
Let’s say that you have two servos on the
rudder. Use a programmable mix to assign the
master channel, rudder, to a slave channel
such as Aux 2 (typically Channel 7).
Then after you adjust the percentages to
ensure that the second servo (Aux 2) is
moving when rudder is applied, you can
adjust the centers of both servos by using
Sub Trim and the endpoints using ATV or
EPA (End Point Adjustment), depending on
the brand of transmitter.
An interesting feature of the 12X that no
synchronizer can perform is called the
“Balance Function.” In the preceding, two
aileron servos can be precisely matched with
their corresponding mates, as can the
elevator and rudder channels.
In writing this column, I am not claiming that
purchasing a 12- or 14-channel system will
eliminate the need for a servo synchronizer.
However, it does help and actually simplifies
aircraft setup. If you are setting up a 35% or
40% model in the manners I have described, a
12- or 14-channel system will cater to all of
your needs.
As I have suggested, take your time when
it comes to equipment selection and building
your airplane to ensure success at the field.
Until next time, fly hard! MA
Sources:
Futaba
(217) 398-8970
www.futaba-rc.com
JR
(800) 338-4639
www.jrradios.com
Thunder Tiger
(949) 900-3300
www.acehobby.com
International Miniature Aerobatic Club
www.mini-iac.com