Frequently Asked Questions - 2006/01

THIS IS THE 22nd monthly column in
which I will try to give you the best
possible answers to questions you have
written or E-mailed to me. Each new
inquiry has a sequential number for
identification purposes.
Because publication space is limited,
part of this month’s material will be
published here, and you can find the
column in its entirety on the AMA Web site
at www.modelaircraft.org/mag/faq/index.asp.
All questions and answers are posted there.
Once the material is posted to the Web
site, you must access particular questions
and answers by subject matter or
categories. This is done to help you retrieve
data for particular subjects. When you call
up a question, it reads “Answer … ”
Double-click on that word, and that
information, along with any related photos,
will appear.
Let’s get started!
Q174: “I attended the AMA Nationals
competition held in Muncie IN this past
July primarily to observe the Control Line
Stunt [Precision Aerobatics] event
participants. While walking around and
talking to all the experts I learned that
several of the top fliers were thinking of
using electric power, instead of glow, and
that two of the Advanced class entrants had
electric-powered models entered.
“Is this a viable idea? Since you are so
involved in electric-powered flight, can you
give me your thoughts on this new thrust?”
A174: You asked the right guy because I’m
quite aware of this new trend in electricpowered
CL Stunt models. At least 10 years
ago I witnessed a modeler fly an electricpowered
CL model while attending the old
KRC [Keystone Radio Control club]
Electric Fun Fly in Quakertown,
Pennsylvania.
I even remember MA’s Aeromodeling
Editor Bob Hunt taking a flight with his
modified RD-1 model back then. He had
converted it from glow power to electric.
At that time the best that electric power
could offer was a cobalt, geared motor and Ni-Cd batteries. That
combination was inefficient and somewhat heavy. A timing device,
made by SR Batteries I believe, was set to cut off the motor rather
than let it “slow out.”
Unknown to me, many top CL Stunt competitors have been
experimenting with electric power since that time. Recently I learned
that Model Aviation Hall of Famer Windy Urtnowski is offering a
DVD documenting a good deal of the progress in electric-powered
CL models up to the present time. You can obtain this video from
Windy by E-mailing [email protected] or calling (201) 896-8740
before 6 p.m. EST.
With the more recent progress in brushless motors and Li-Poly
batteries, electric CL models are getting a real lift! Immediately after
the 2005 AMA Nats (to which the reader referred), Bob Hunt,
another Model Aviation Hall of Famer, decided to retrofit his
Genesis Extreme design with electric power. That model was
originally designed for .40-size glow power.
Bob decided to use the electrified Genesis to try to win a spot on
the US F2B (CL Stunt) team that will compete at the FAI CL World
Championships, to be held in Spain July 16-23, 2006. Bob made this
decision after having watched the successes Mike Palko has had
with his Silencer (which was featured in a construction article in the
Is electric-powered CL really viable?
January 2006 91
? Frequently Asked Questions Bob Aberle | [email protected]
MA Aeromodeling Editor Bob Hunt holds his Genesis Extreme CL Precision Aerobatics
model that is now electric powered. Bob won a spot on the US F2B team with it.
Also included in this column:
92 MODEL AVIATION
Bob Hunt makes an impressive demonstration flight with his
Genesis Extreme at the recent NEAT Fair in New York.
How FMA Direct’s Viewer Software for the 6s charger looks on
your PC screen. Individual battery voltages are displayed at the
left; the Ah going back into each cell is displayed at the right.
The heart of any CL electric model is a specially designed
timer/controller. Bob Hunt uses this one by Sergio Zigras.
Primary components of FMA Direct’s Skyvolt battery system (L-R): the DPM, the
Skyvolt 6s charger, and the three- and five-cell Skyvolt battery packs.
Using FMA Direct’s interface module
cable and a USB-to-serial port adapter,
you can view all your Skyvolt battery
parameters on a laptop computer.
March 2005 MA—the electric-power theme issue).
Hobby Lobby International provided Bob with an AXI 2826/10
brushless Outrunner motor and a Thunder Power 4S2P Li-Poly
battery pack made from 2000 mAh cells. That yields a pack with a
nominal voltage of 14.8 and a capacity of 4000 mAh.
Bob also used a Castle Creations Phoenix-45 speed control and
a Bill Lee 11.5 x 4.1 carbon-fiber three-blade propeller. The
maximum motor current turned out to be 39 amps.
An electric-powered CL model cannot benefit from radio
control. Something must operate the ESC, and that is the allimportant
solid-state timer/controller. Sergio Zigras (whose
company is Z Tron) has designed and is manufacturing a new
version of the timer. It is distributed by Windy Urtnowski and costs
$30. You can learn more at www.windyurtnowski.com.
The Z Tron CL ESC Controller and Timer measures 1 x 3/4 x 1/2
inch and weighs only 2 grams. It allows you to time your flights
from 0.5 to 8.0 minutes in programmable 30-second increments.
Motor speed is adjustable during the timed flight period.
One optional feature allows you to arm the timer (push-button
switch), and then you have 30 seconds to walk out to your control
handle and get set, and then the motor starts. The prescribed
One of the biggest benefits of electric
power is that the motor essentially makes
no noise. Therefore, you can fly at sunrise
at a local athletic field and no one will even
know you are there. (It’s best to get
permission in advance, however.)
Flying his electric-powered Genesis
Extreme, Bob Hunt earned one of the three
team spots—being the first US team
member to fly CL with electric power. He
will join the first-place man on the team
Paul Walker and second-place man David
Fitzgerald. Bob, I wish you and the rest of
the team the best of luck!
(Editor’s note: Thanks from all of the
team members!)
Q175: “I read your review article on the
new FMA Direct Skyvolt balanced batterycharging
system that appeared in a recent
Model Airplane News. I noticed in the
photos that the FMA Direct 6s Skyvolt
charger has only LED indicators and no
meter.
“I’m kind of disappointed since I’ve
been used to the LCD screen on my
AstroFlight 109 Lithium charger. Is there
any chance that FMA may add a meter at a
later time?”
A175: It probably won’t come as a surprise
that I have been using two different FMA
Direct Skyvolt batteries, the 6s charger, and
both types of DPMs (Discharge Protection
Modules) for the past three months. I’m
thoroughly satisfied with the total
performance of this integrated Li-Poly cellbalancing
concept.
The 6s charger has six separate outputs
built into one case. Therefore, each cell in
your Skyvolt battery pack is individually
charged to the same maximum voltage, and,
as a result, all the cells in the pack will be
balanced (equal) after each charge.
But I admit that I was also a bit
disappointed about not having an LCD
screen, with metered outputs, on the 6s
charger. In a discussion with FMA Direct
engineers I learned that they may come out
with a deluxe version of the 6s charger that
will have an LCD display screen.
I also learned that FMA Direct has
upgraded its Viewer Software program (that
is normally supplied with its FS5 and FS8
receivers) to include the 6s charger. You
can download this program from the FMA
Web site (www.fmadirect.com) by going to
the “Service & Support” “Downloads”
section. Download “Dot.Net Framework
Update” and then “Charger 6s Viewer.”
If you don’t already have FMA
Direct’s interface cable, you will need
one. It is identified as the Flight Systems
PC Serial Interface Module and sells for
$19.95. You plug the servo connector lead
from this module into the 6s charger. The
serial connector goes into a serial port on
your PC, or by using a serial-to-USB
Dell laptop and plugged the 6s
interface module cable and adapter into
one of my three USB ports. When you
open the software, you will obtain a neat
data sheet that displays the voltage of each
cell in your Skyvolt battery pack and the
Ah (ampere-hours) that were out back into
each cell during the charging process.
You also see a digital readout of the
charge current you set. Best of all, you can
view a graph of the data and even file the
data using a “Save As” command.
I put my laptop next to my 6s charger
while at the flying field. If you expect to
be out for a long time, you better get a
power inverter to operate your laptop since
the PC batteries don’t last that long. I’m
enjoying myself even more using this new
feature. It’s actually better than having an
LCD screen built into the 6s charger.
Q176: “I have had my electric motor stop
abruptly in flight when the ESC lowvoltage
cutoff operated. I ended up almost
losing my aircraft because when that
happened I was quite far from the runway.
“A friend told me I should time the full
motor run on the ground as a guide and then
keep track of that flight time while flying so
I can shut down the motor before it cuts off
by itself. Does that sound right?”
A176: No, it is not right because you
should not run a motor statically on the
ground for long periods of time. However,
a quick motor-current check is okay.
Without the benefit of natural airflow
(that your model gets while flying), you
can easily overheat your motor, your ESC,
and even your battery. Many new ESCs
have a setting for a slow cutoff that gives
you some warning before the motor stops
completely. If a sudden cutoff bothers you,
this may be the kind of ESC you should
adapter you can basically connect the 6s
to a USB port on your PC.
maneuvers in the AMA Precision Aerobatics pattern are completed
in approximately 5.6 minutes, so the timer is set to 6.0 minutes.
This is comparable to running the fuel tank dry on a glow engine.
01sig3.QXD 11/22/05 3:06 PM Page 92
A close-up of the Genesis Extreme’s underside, showing the
carefully cowled-in AXI 2826/10 brushless Outrunner motor.
01sig3.QXD 11/22/05 2:51 PM Page 91