70 M ODEL AVIATION
WhErE ArE the kids? Pardon me while I
deviate from the intended theme, but this is a
subject we read about often—not only in the
pages of MA, but in the rest of the model press.
Wherever the kids may be, few of them
are out at the model fields in the United
States. However, they are a common sight at
Latin American fields!
A photo shows 12-year-old Julio Pastora
Jr. of Costa Rica teaching his friend Pablo
Manso on a trainer system. It looks as if
Pablo has learned his first lesson: you have
to wear cool sunglasses!
This is not uncommon. In the last couple
years, I have traveled as far south as
Argentina—and unless you go to the
Antarctic, you can’t go farther south—and I
have seen kids flying everywhere!
In Chile, I witnessed six-year-old flier
Felipe Salamanca take off, do basic
maneuvers, and land—without even breaking
the propeller. I know many adults who would
be happy to do that, don’t you?
Argentina is the home of world-class
Radio Control (RC) helicopter flier Debora
Cadelli—now an old lady of 17—who has
previously graced these pages. Those of you
lucky enough to attend the 2000 Tournament of Champions might
have had the pleasure of watching her do demonstration flights.
Teens, and even preteens, are at every Central and South
American field.
Why? I don’t have the answer. Dads obviously have a great deal
to do with it, but maybe moms have even more to do with it; they
are seen in great numbers at all fields.
After a demo in Buenos Aires by Sergio Testa—one of the country’s
top aerobatic pilots—his mother walked out to hug him and kiss his
cheek in front of roughly 5,000 spectators. Sergio is in his mid-20s!
When was the last time you saw anything even resembling this at
one of our fields? Think about it!
Cermark power Panel Plus!®: In the November issue, I treated you
to a photo of Cermark’s new many-featured power panel. It’s not
just another power panel—take my word for it.
The caption invited you to see the text for further information,
which was not included because of space limitations. Please go back
and admire the photo; here is the promised information.
I don’t know what Cermark means either, but it is a good
source of high-quality and fairly priced electronics and other
types of products, including the Dave Patrick-designed Pitts S-2B,
in a 60-inch span for .90 to 1.20 engines and four-channel (with
five servos) radios.
Unless your friends are familiar with this Almost Ready-to-Fly, you
would have no problem convincing them you built it—it is that good.
A recent addition to its line of electronic products is a new power
panel, but with interesting differences.
The Cermark Power Panel Plus!® is powered by the usual 12-
volt battery, and has the common outputs for a starter, a six- or 12-
volt electric fuel pump, and an adjustable glow-plug driver. But
that’s where the similarities to other power panels end.
It provides an adjustable charging current for your one-cell
glow-plug Ni-Cd and a 300 mA “top-off” charge for your receiver
and/or transmitter batteries.
The four-digit, half-inch-high digital Liquid Crystal Display
(LCD) indicates the state of charge of the 12-volt battery; glow-plug
Eloy Marez
E l e c t r o n i c s
2626 W. Northwood, Santa Ana CA 92704
Twelve-year-old Julio Pastora Jr. (R) acts as an instructor while Pablo Manso learns to
fly. Young RCers are common at Latin-American flying fields—why not here?
Connections for two-volt lead-acid battery provides less glow-plug power at idle. Switch “S” can be throttle-actuated.
Continued on page 74
driver current; receiver battery voltage
under a 300-milliamp load; transmitter
battery voltage under a 300 milliamp load;
and glow-plug Ni-Cd charging current.
This is the power panel to replace all
power panels, and it carries a $59.95 MSRP
(Manufacturer’s Suggested Retail Price—
don’t you hate all these abbreviations and
acronyms?). Check your favorite dealer for
the current “street” price.
Contact Cermark at 107 Edward Ave.,
Fullerton CA 92833; Tel.: (714) 680-5888;
Fax: (714) 680-5880; E-mail:
[email protected].
Expanded scale Voltmeters: Another
misnomer has found its way into our RC
vocabulary. Manufacturer’s and editorial
copy often refer to digital voltmeters, as
found in the Cermark Power Panel, as
Expanded Scale Voltmeters (ESVs) when
they are used to read battery voltage.
That is not correct. The term ESV
appeared when the only test meters we had
were analog types; i.e. scale and needle
indicator devices. When connected to read
voltage, such instruments normally read
zero to something—say, 1-10 volts.
That does not provide much accuracy on
a two-inch-long scale—little more than a
quarter of a volt.
However, when testing, say, a 4.8-volt
receiver, values much below and above that
amount are of no interest, so the reading was
“expanded” to read only four to six volts.
With any applied voltage less than four
volts, the needle did not move off the left
side—or originally, the zero point. It would
start to move at four volts, reaching its
right-side extreme of travel at six volts.
Reading only two volts instead of 10 on
the two-inch-long scale made it possible for
a far greater degree of accuracy.
The digital voltmeter is of a different
breed; a 0- to 10-volt-reading instrument can
automatically come with far greater
accuracy—often down to the hundredths of a
volt. It does not require “expanding,” or
reducing its range, in any manner. It could be
done, but without an increase in its accuracy.
For RC use, both types of instruments are
often designed to “load” the battery—that is,
draw a certain amount from it while it is being
tested. That seems to be where the wordsmiths
go wrong; any voltage-reading meter that loads
the battery being tested, regardless of whether
the display is analog or digital, becomes an
“Expanded” Scale Voltmeter.
servo screws and the Proper Mounting of
Servos: As with all components of RC
systems, servo screws have been greatly
improved from what we lived with in the
early days of EK, Kraft, and Orbit!
In the phrase “fantastic power and
resolution,” the last word is the term used
to describe how accurately and repeatedly
they follow your commands.
74 M ODEL AVIATION
Continued from page 70
Electronics
Laser Provided
Envelope 074
March 2001 77
Unfortunately, some of it is lost through
sloppy installations!
First, those metal grommets that all
manufacturers provide need to be installed
from the bottom—not from the top, as is
often seen. The reason is, when installed
with the sharp edges down, they will dig
into the mounting material—especially if
plastic trays are not used and the servo is
being mounted on wood.
The results are too much compression of
the rubber grommet, eliminating most of its
shock and vibration isolation. When the
brass grommet is installed correctly, from
the bottom, the base will not dig into the
mounting surface and the rubber grommet
is not overly compressed!
Next, select the proper mounting
screws. Servo-makers generally furnish
sheet-metal or wood screws for mounting
servos. They will work, but they are the
easy way out—and the easy way is not
necessarily the most efficient way.
My opinion (backed up with years and
hundreds of in-flight hours without a single
servo coming loose) is to use machine
screws in threaded wooden beam mounts. It
is slightly more work, but the sense of
security is well worth it.
Equally important is using the propersize
screw—regardless of the type you
prefer. I see many servos mounted with No.
2 hardware; that is far too small for the hole
in the bronze grommet, allowing enough
shift when the servo is under load to lose all
that precision you paid for in the first place.
Most grommets are better fits for No. 3
or 4 screws; use the one that fits closer with
the grommets in use.
Marking and drilling the holes properly
is important, and I have found a surefire
method to do it.
Install those brass grommets
incorrectly—with the large side upward.
With the servo locked in position, mark the
mounting holes with one of Great Planes’
Engine Mount Hole Locators. The name
indicates its primary intended use, but it is
the perfect tool for locating mounting holes
for anything requiring already-located
mounting holes.
Drill the proper-size hole for the final
tap size, tap once, and drop some thin
cyanoacrylate glue into the hole. Let the
adhesive dry thoroughly, then retap it.
The result will be a perfect thread that
will accept installation and removal of the
servo as many times as you want to do so,
without losing security.
Lighting Glow plugs at Idle: This is not a new
concept, but I have a different approach for
those of you running twin-cylinder engines.
Once the engine is running, you don’t
need full voltage on the plug to keep the
engine going during long periods of idle.
Full voltage, as applied during the starting
process, cannot damage the engine, but it
has to overheat the plug and shorten its life
if applied for long periods of time.
Less than one volt is ample to keep things
percolating—even during long periods at idle.
The system proved its merit a few
years ago when I was flying a Kavan
50cc engine on glow, which never failed
me after I resorted to lighting the plugs
during idle. It involves the use of a twovolt
cell connected to both plugs in series.
What with wire, switch, and connector
losses, the voltage at the plug is
approximately .8 volt—not enough to heat it
to that familiar level we see when a 1.25-volt
Ni-Cd is applied, but enough to keep the plug
hot while the engine is running at idle.
The wiring is simple, including an
external source, which can be a power
panel, that automatically cuts out the
internal power when plugged in to
provide starting voltage.
The source—the secret to this
particular system—is a two-volt sealed
lead-acid cell, rated at 2 volts at 2.5
amperes. It is the same size as a common
“D” alkaline cell, except that it has pushon
terminals on top rather than the
alkaline-type contacts at either end.
The cell weighs 6.4 ounces, which
should not be a problem since I am
referring to fairly large-size airplanes—a
1⁄3-scale model for the Kavan I mentioned.
Such cells are fairly common from
electronic sources; they are often surplus
from alarm systems in which they are
replaced at given intervals.
The cells are available new for
$6.50 (No. G2-001) from Herbach and
Rademan, 353 Crider Ave.,
Moorestown NJ 08057; (856) 802-
0422; E-mail: [email protected].
I supplied the charging current with
an Ace metered variable charger—a
handy unit that will handle all normal
and unusual requirements.
Herbach and Rademan catalogs a sixvolt
800 mAh charger (No.
TM95ADR2961) at $4.50, which will
probably require you to add a low-value
resistor in series to adjust the current to a
C/10 (capacity divided by 10, or 250
mA)—a rate at which a completely
discharged cell will be revived in 10 hours.
Normally, four or five hours will put
back what most of us use in a normal
flying session. Avoid overheating sealed
lead-acid batteries during recharging. MA
