42 MODEL AVIATION
Introduction to
Indoor Radio Control
I WROTE A feature article published in last
month’s MA titled “Introduction to Parking
Lot Flying.” That category involves flying
relatively small, easy-to-build, and relatively
inexpensive RC models close in.
Aircraft in that size category (up to
roughly 16 ounces total weight) can also,
under certain circumstances, be flown in
indoor facilities. From a practical standpoint,
the larger parking lot-size models can be
flown easily and safely in extra-large indoor
facilities such as golf practice domes
(inflatable) and field houses used for football
practice.
Since winter weather hits many areas
of our country, indoor RC flying during
those months is increasing in popularity.
Not everyone has a golf dome or a field
house in his or her community, but almost
everyone has a school gymnasium or
auditorium that can be an excellent
substitute. To be able to use these smaller
indoor flying facilities, you have to
by Bob Aberle
Author’s original-design Kiwi weighs just 3.4 ounces with 100-
square-inch wing. It uses FMA Direct M5 receiver and two FMA
Direct PS-20 submicroservos. Battery power is two 145 mAh Li-
Poly cells.
Dynamic Web Enterprises proprietors Dan Hurd (L) and his dad
Clarence. Dan holds 1-ounce Pitts Special biplane; Clarence
holds his own-design Lil Skeeter.
Another Joe Wagner FF design from the early
1950s: the Dakota biplane. At right is originalsize
model powered by .049 glow engine. The
author built reduced-size version (left) which
weighs 1.3 ounces with 69 square inches of total
wing area. Power is single 145 mAh Li-Poly
battery. Construction article and plans were
published in May 2003 RC MicroFlight.
Author holds 3.8-ounce version of
popular Joe Wagner FF design—
The Sioux—from the early 1950s.
It has 90-square-inch wing and is
powered by GWS LPS/B2C-C
motor and two FMA Direct/Kokam
340 mAh HD Li-Poly cells. Will
soon be featured as construction
article in Quiet Flyer magazine.
The 2004 NIRAC Indoor Championships will be held
at the big Oakland Yard Athletics facility in Waterford MI.
Fun-flying will be permitted before contest rounds.
All are invited!
07sig2.QXD 4/26/04 8:23 am Page 42
July 2004 43
Pair of typical magnetic actuators. They have a moving magnet within a
coil. Exact separation between two coils and the fact that they are at right
angles to one another provide for control position centering.
Todd Long of Todd’s Models has been selling his Tiny for several years.
Depending on motor and battery choice, this excellent-flying design can
weigh approximately 4 ounces and provide considerable indoor RC funflying.
Don Stackhouse of DJ Aerotech holds two of his Roadkill-series
profile sport-scale models: an Me 109 (L) and a Ryan ST. Each
weighs roughly 3-3.5 ounces and operates on two Li-Poly
batteries.
Closer view of Clarence Hurd’s Lil Skeeter, which was
designed around DWE’s RFFS-100 micro RC system. It
has 46 square inches of wing area and weighs 23 grams
(.81 ounce) including single 130 mAh Li-Poly battery.
Motor is KP-00 geared at 2.67:1.
The Lightning RTF foam model was originally
intended to be an electric-powered FF. An
excellent conversion article by Greg Covey
detailing how to install the DWE RFFS-100 micro
radio system is on the DWE Web site.
DWE RFFS-100 micro RC system is extremely
popular. On this one, PC board weighing 1.8
grams is an RC receiver, ESC, and two magnetic
actuator drivers. It’s one of the best starting
points for flying RC models at or near 1-ounce
total weight.
Photos courtesy the author
07sig2.QXD 4/26/04 8:26 am Page 43
Let’s get into the details of these small, or as we call them, “microsize”
RC aircraft.
Micromodel Sizing: Micro-size models dedicated to indoor RC
flying can range from roughly 8 ounces total weight down to only a
few grams. For this presentation I’m concentrating on 4 ounces total
weight and less.
Right now the range of 4 ounces down to approximately 2.5
ounces can be enjoyed while employing the
available equipment technology, and at
relatively moderate prices. From 2.5 ounces
down to roughly .75 ounce, you will need one
of the several submicroservos on the market
or magnetic actuators. For less than .75 ounce
down to a few grams, you need highly
specialized equipment and considerable
model-building skills.
Typical 4-ounce models can have
approximately 80-120 square inches of wing
area, which will yield wing loadings in the
range of roughly 4-6 ounces/square foot. The
4-ounce total weight could consist of 2.25
ounces of equipment (receiver, two servos,
Li-Poly battery, motor, propeller, and motor
speed controller). The remaining 1.75 ounces
includes the model structure (including
covering, finish, wheels, hinges, and control
linkages).
This typical 4-ounce model can employ
traditional RC equipment, but it will be
smaller in size and weight. The servos will
consider reducing your RC model’s size and weight.
The subject of this presentation is flying RC indoors with models
that weigh less than 3 or 4 ounces. As I noted, there are certain
situations in which you can fly a parking lot model inside. There are
also times in which you can fly a 1-ounce RC model outdoors. To do
that, you need to seek out the dead-calm early-morning or -evening
air. Calm-air outdoor flying also lends itself well to backyard-type
flying, making it a perfect family hobby/sport!
44 MODEL AVIATION
Popular little KP-00 geared motor and companion 3-inch-diameter
propeller. Several sources sell this motor, as noted in text. Power
range is intended for .75- to roughly 1.5-ounce models!
Rear of FMA Direct M5 dual-conversion receiver, which is
smallest dual-conversion RC receiver on the market. It is
available on 72 MHz and six-meter RC channels. Weighs .35
ounce with case!
Basic RC system for 2.5- to 4-ounce model weight (L-R): Castle
Creations Pixie-7P ESC, FMA Direct M5 dual-conversion
microreceiver, two FMA Direct PS-20 submicroservos, two-cell
FMA Direct/Kokam 340 mAh HD Li-Poly battery pack.
Power, RC system needed to fly 1-ounce total-weight model.
Left: KP-00 geared motor, 3-inch-diameter propeller. Top center:
Pair of EFlight Designs magnetic actuators to operate rudder,
elevator. Top right: A 145 mAh Li-Poly battery cell. Just below
that is DWE RFFS-100 PC board containing receiver, ESC, two
magnetic actuator drivers. Lower right: Azarr’s E Cubed RC
reduced-size receiver antenna.
Cutaway of GWS LPS/B2C-C geared motor
mounted to 3⁄16-inch wood dowel. A
setscrew holds motor in place. Two
plywood formers support dowel. It’s
simple and effective! You can easily
change motor at flying site.
Dave Burley has been developing
microservos for indoor RC fliers’ benefit.
His latest (shown) is 1-gram proportional
feedback ultramicroservo. He demonstrated
it to many indoor RC experts at 2003 NEAT
Fair. Dave wants to interest a prominent
manufacturer to pick up on production
rights for it. It worked well, and he hopes it
can be produced at a reasonable unit price.
07sig2.QXD 4/26/04 8:28 am Page 44
July 2004 45
provide regular proportional control, operating from a conventional
RC transmitter.
I have a little indoor sport model that I’m flying at 74 square inches
of wing area and 1.2 ounces total weight. The wing loading works out
to only 2.3 ounces/square foot. It employs two magnetic actuators, and
a 145 mAh Li-Poly battery cell provides all the power. When flown
outdoors, this model doesn’t like any wind! I’ll get into the specifics of
the RC equipment later.
Safety: As is the case with parking lot flying, indoor RC flying has
certain safety issues about which you should be concerned. Even
though you are flying inside, radio signals can travel through buildings
easily without much attenuation of strength. Someone might be flying
right outside your indoor facility, so please check around first. It’s best
to check local hobby shops and RC clubs too.
Also safety related is your model’s speed in flight. An airplane
with less than 100 square inches of wing area and weighing
approximately 10 ounces might be capable of speeds in excess of 60-
75 mph. If it hits something or someone, it could cause physical or
property damage.
Common sense must prevail and reasonable weights and flying
speeds must be commensurate with the size of the facility. A leadertype
person should be in charge of each flying session. That person
must have the last word on who can or can’t fly, and his/her judgment
must be respected at all times!
Micromodel Design: I’ve already suggested weights and wing
loadings, and soon I will get into power systems. There aren’t many
ARF models in the less-than-4-ounce category; that might be
considered the bad news. The good news is that a 4-ounce airplane
can, for the most part, be constructed from scratch, with a minimum of
materials and a minimum of assembly time and skills. I’ve built 1-
ounce RC models from a single sheet of 1⁄32 x 3 x 36-inch balsa. That
is almost as inexpensive as you can go!
The 2- to 4-ounce models can often be built up from the many
rubber-powered kits on the hobby market. Doing this has become
popular. Another possibility are the profile semiscale models, such as
DJ Aerotech’s Roadkill series. Those are easy to build, inexpensive,
and are even supplied with the recommended motor.
If you want to try a 1-ounce model for the first time, the best
trainer is the Lil Skeeter designed by Clarence Hurd of Dynamic Web
Enterprises (DWE). This design was reviewed in the June 2002 RC
MicroFlight newsletter. Plans are available from DWE, and you
receive a free plans copy when you purchase the DWE RFFS-100
micro RC system.
A more ambitious project is Dave Robelen’s Walker, which he
Former AMA executive director and RC MicroFlight founding
editor John Worth holds Pee Wee Flyer made by Estes (the
rocket people). Wal-Mart stores throughout the country sell this
RTF for only $19.95. An article describing it was published in
the October 2003 RC MicroFlight.
Sky Hooks and Rigging owner Tom Mc Cann holds his little
Mosquito indoor slow flyer that Ken Coleman designed. It is
available from Tom as a kit. It spans 24 inches, has 131 square
inches of wing area, weighs 2.25 ounces, and flies on single Li-
Poly battery cell.
Micro-Pod is Bob’s latest original-design indoor RC model. A
construction article was published in November 2003 RC
MicroFlight. It weighs 1.2 ounces and has 74-square-inch wing
area. Power is geared KP-00 motor operating on single 145 mAh
Li-Poly cell.
calls an “ultralite indoor floater.” Dave went to the other extreme and
designed a 1-ounce model with an amazing 357 square inches of wing
area. The resulting wing loading works out to only .4 ounce/square
foot and provides flying speeds of just 3-4 mph. You can walk under
this model while it is flying. The Walker was featured in the July 2003
RC MicroFlight.
07sig2.QXD 4/26/04 8:30 am Page 45
Henry Pasquet is probably the most famous indoor RC flier. His
goal for years has been to build smaller and smaller models. He
holds his 4-inch-span Lacy M-10. It weighs 2.6 grams (total) with a
Gasparin G2.6 CO2 engine. RC system is by Nick Leichty. One No.
337 silver-oxide battery powers the system. It flies very well despite
its size!
US Airways Captain Joe Malinchak’s super-detailed Piper L-4
Grasshopper is military version of Piper Cub. Weighs 1.3 ounces
total including complete scale cockpit interior, landing-gear
shocks, etc. Has geared KP-00 for power! Joe earned DWE award at
2003 NIRAC Championships for RC Scale model with highest
points and weighing less than 1.5 ounces!
NIRAC president, MA columnist, and newly inducted Indoor RC Hall
of Fame member Dave Robelen holds his Scale 34-inch-span Piper
Vagabond. It has 200 square inches of wing area and weighs 4
ounces ready to fly. Power is a DC 5-2.4 coreless motor geared 7.5:1,
running on seven-cell 50 mAh battery pack.
Matt Keennon’s tiny electric-powered Scale P-38 twin spans only
10.5 inches and weighs 35 grams (1.23 ounces) with two M-20
motors and two Kokam 145 mAh Li-Poly cells in parallel. Flight
demos at NEAT Fair were spectacular. Matt makes a living
working on government-sponsored micromodel projects.
Nick Leichty, known for his ultramicro RC models, holds his
Micro Aero Master biplane at 2003 NEAT Fair. It employs one of
his micro three-channel RC systems powered by 4mm motor and
a 40 mAh Li-Poly battery. Model spans 5.5 inches and has 5.5-
gram (.19-ounce) total weight. Approximate flight time on a
charge is five minutes. The author saw the flights and couldn’t
believe it!
46 MODEL AVIATION
07sig2.QXD 4/26/04 8:32 am Page 46
Power Systems: Indoor power systems
primarily involve electric motors, be they
direct drive or gear driven. CO2 power
(compressed gas) is used to some extent, but
the ability to throttle these engines is still in
the experimental stages. Although some of
the tiny glow-fuel and diesel engines might
find their way into indoor RC flying, the
combination of noise and exhaust fumes
makes it somewhat impractical.
Small motors are becoming more and
more popular, and the prices keep going
down. This past year, Grand Wing Servo-
Tech (GWS)—a huge parking lot-/indoormodel
manufacturer—introduced a tiny
geared motor that it calls the “LPS” series.
One of the motors in this category—the
GWS/LPS/B2C—weighs only approximately
12 grams (.42 ounce). It is available in three
gear ratios (4:1, 5:1, 6.2:1).
I’m presently using the 6.2:1 geared
version, which operates on two Li-Poly
battery cells (nominal 7.4 volts) at 700 mA
motor current and 6-watt power level. Using a
GWS 6 x 5 propeller, I generate more than
enough thrust to fly a 4-ounce RC model.
These motors sell for roughly $10. How can
you go wrong?
The .75-1.5-ounce models are generally
powered by pager-derivative motors such as
the Knight & Pridham KP-00 (of which there
are several models with different windings),
with gearing ranging from 2.75:1 upward of
6:1. Each specific gear ratio requires a
different size propeller. Propeller diameters
range from 3 to 6 inches. The gearing choices
attempt to get the most thrust from the motor
while drawing the least current. This is the
game you must play with electric-powered
flight.
The little KP-00 motor will work well on
a single Li-Poly cell drawing roughly 700 mA
of current at approximately a 3-watt power
level. The trick with this is to be able to get an
RC system (receiver and servos) that can also
operate reliably from a single Li-Poly cell at
roughly 3.6 volts.
There are receivers that will do that,
especially those used in conjunction with
magnetic actuators. Bob Selman Designs
offers a new voltage-doubler unit that takes
the single cell voltage and increases it to
roughly 5 volts for more reliable RC
operation.
Many smaller motors are becoming
available for the indoor RC experimenter who
wants to keep reducing that total model
weight to as little as a few grams. Experts
such as Henry Pasquet and Nick Leichty are
regularly flying models weighing roughly .3
ounce! You can find tales of their
experimental efforts in RC MicroFlight. But
as I pointed out before, these truly micro RC
models require a great deal of experience and,
most of all, patience!
As this is being written, I have heard
about several micro manufacturers who have
prototype miniature brushless motors and
companion speed controllers in the works. A
lightweight, highly efficient brushless motor
will provide yet another breakthrough in
indoor RC.
Before leaving the power scene, I’ll
mention that there are CO2 motors now
available for RC model use. They are still
comparatively expensive, but a model’s
weight can be reduced even further than with
electric power because the CO2 tank weighs
less than a battery.
The biggest problem until recently has
been the ability to throttle these air-operated
motors. Stefan Gasparin in the Czech
Republic has made remarkable progress in
this regard. I urge you to look at his Web site.
ESCs: Even the electric motor speed
controllers have been shrunken to fit the
needs of our micro-size aircraft. I think it’s
safe to state that all of the micro ESCs have a
BEC, which allows for the sharing of the one
battery pack.
As you will soon learn, the new Li-Poly
battery technology requires that no cell drop
to less than 3.0 volts when in use. This is a
minimum discharge point. To be on the safe
side, a micro ESC’s low voltage cutoff point
should be set to increments of 3.0 volts per
cell. If you are using one Li-Poly cell, the
cutoff should be 3.0 volts. If your pack has
two Li-Poly cells the cutoff should be 6.0
volts, and so on.
Castle Creations’ Pixie-7P ESC allows
you to program the voltage cutoff point.
There aren’t that many choices, but they will
improve in time. Setting the voltage cutoff on
07sig2.QXD 4/26/04 8:33 am Page 48
the Pixie isn’t all that easy and does require
some patience, but this is the concept you
want to look for in the future!
Batteries: Until recently, the batteries of
choice for 4-ounce and lighter models were
the 100-125 mAh NiMH types, usually in
packs consisting of seven or eight cells. In the
past year we have been introduced to a new
form of battery known as the Li-Poly. These
new cells provide more capacity in a lighterweight
package. Both of those parameters are
exactly what you want for micro RC models.
Of equal interest is the fact that each Li-
Poly cell has a characteristic voltage of close
to 4.0; the older Ni-Cd/NiMH cells had only
1.2 volts per cell. So two Li-Poly cells work
like a six- or seven-cell Ni-Cd/NiMH pack.
We typically see two-cell packs consisting
of 145 mAh or 340 mAh powering 3- to 4-
ounce RC models. A two-cell 145 mAh Li-
Poly pack weighs 8.7 grams (.31 ounce) and
can fly that 3- to 4-ounce model at 700 mA
current (6 watts) for 10-12 minutes and more,
depending on how you throttle the motor in
flight. And two of the 340 mAh Li-Poly cells
(weighing 20.1 grams, or .71 ounce) could
provide up to 30 minutes of motor run time.
However, Li-Poly cells are still quite new
on the market, and they must be taken care of
very carefully. They require a special
dedicated charger and should not be charged
with more than a 1C current, which takes
roughly an hour. Li-Poly batteries should not
be discharged to less than 3.0 volts per cell.
Li-Poly cells are also currently somewhat
limited in their load capabilities. Initial
offerings could only provide loads up to
approximately 5C (five times the capacity of
the battery). Recently a new variety of Li-
Poly cell has been introduced that can stand
loads upward of 20C (quite an
improvement!).
Li-Poly batteries is a subject unto itself. I
wrote a comprehensive article titled
“Introduction to Lithium-Polymer Batteries”
that was published in the May 2004 MA. If
you haven’t read that piece, I highly
recommend that you do so before attempting
to use Li-Poly batteries in a model airplane of
any kind.
Micro RC System and Components: The RC
equipment is conventional technology, but is
obviously made smaller and lighter. An
inexpensive microreceiver is the GWS R-4P,
which has four-channel capability, is a singleconversion
circuit, and weighs 6.8 grams (.25
ounce). At approximately $30, it is a great
buy.
For those who want good range and
selectivity, in a crowded flying environment,
the FMA Direct M5 dual-conversion receiver
is an excellent choice, especially in the 2.5- to
4-ounce-model weight class. The M5 weighs
9.5 grams (.35 ounce).
Another outstanding choice is the Berg-
5*DSP at .35 ounce and the new Berg-4*DSP
Micro Stamp at just .25 ounce. The Berg
receivers are available from RC Direct. With
the Berg and FMA Direct receivers, you can
remove the receiver case for a further weight
reduction.
For the extra-small models (1.5 ounces
and lighter), the DWE RFFS-100 has been the
popular microsystem for some time. It is a
microreceiver, a built-in ESC with BEC, and
drivers for two magnetic actuators on a single
PC board. The entire board weighs only 1.8
grams (.06 ounce!).
The RFFS-100 receiver is not very
selective, so you can’t use several channels on
either side of your operating frequency when
flying. But this system has provided a load of
indoor RC fun-flying under the right
conditions.
Jean-Marie Piednoir (JMP) of France
makes a new and more selective
microreceiver which Bob Selman Designs
sells in the US. This receiver is claimed to be
extremely narrow band (selective!) and
includes an ESC and two magnetic actuator
drivers. It weighs 2.2 grams (.08 ounce), and
the price without connectors is $89. I’m sure
we will be seeing plenty of these units put
into indoor RC service in the near future.
As I was writing this, I learned of the new
Gasparin Penta 2.4-gram (.8-ounce) fourchannel
receiver, which is claimed to be
incredibly selective and will be selling in the
US at a reasonable $39.
In addition to receivers, servos or actuators
are also important. Conventional servos,
meaning regular proportional feedback
servos, are available at roughly 5.6 grams (.20
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07sig2.QXD 4/26/04 8:33 am Page 50
ounce). Two come to mind: the popular Hitec
HS-50 and the new FMA Direct PS-20. Each
sells for less than $30 and has been reliable.
The German WES-Technik company has
been making a linear-output-type microservo
for the past couple years. It weighs 2.1 grams
(.07 ounce) but is comparatively expensive at
$70-$80 (US).
Stefan Gasparin in conjunction with Didel
(the Swiss gear company) has designed a new
GDservo, which has a rotary output and
weighs 1.33 grams without a case. It will be
pricey, at $98 (US). Stefan also has a new
concept he calls a “Proportional Magnetic
Actuator.” I’ve seen some photos, and the
idea looks entirely realistic. Price is said to be
$39 each (US).
At the bottom of the weight scale are the
truly magnetic actuators; these are coil
devices with magnets that move inside the
coils. They require some patience to install
and offer little control force. That means your
hinges and control linkages must offer the
least possible friction. These magnetic
actuators make RC models of less than 1
ounce total weight possible. Good sources of
magnetic actuators include Bob Selman
Designs, Cloud-9 RC, E-Flight Design, and
DWE.
One last reference is to a “brick” design,
which was popular in the early 1970s. FMA
Direct is almost ready to release a microbrick
that will include one PC board, a narrow-band
receiver, ESC, control actuator drivers, and
two servos or two magnetic actuators. Placing
all of the components on a single board can
make certain installations impractical, but the
bottom line is that the brick eliminates a great
deal of wiring and connectors, thereby
reducing the overall weight. I believe this
concept will find a home in the 2.5- to 4-
ounce model category.
Connectors: The connectors and the wire size
(gauge, which refers to diameter) are
important. You want to carry the current
involved and no more; using a connector that
is too large or a wire with too large a diameter
only adds weight to little airplanes that can’t
afford it.
The larger parking lot-size models can
properly use the popular Anderson Power
Pole-type connectors (also known as Sermos
connectors). You can use these from roughly
6 amps of current up.
The Deans four-pin connectors are popular
for 3 to 6 amps of current. It is a good idea to
gang two pins to make a single connection. In
that case, the four pins yields two conductors.
From 1.5- to 3-amp current, the JST red
plastic housing connector is fine. For less than
1.5 amps of current, the JST white plastic or
Cloud 9 RC Unisex connectors will do the
job.
EFlight Designs carries an excellent line of
submicroconnectors. Wire size can start with
16 gauge for the 8- to 10-amp current. As you
work your way down in current, the wire
gauge can go from 22 to 28, and even 32.
Your hobby supplier can recommend the best
size for each current level. The JST
connectors come with the wire already
attached.
Indoor Flying Tips: If you are already an RC
sport flier or a parking lot flier, you are
certainly qualified to fly indoors; but the
generally “restricted” airspace can be
extremely challenging at times. If you are
lucky enough to be able to fly a 4-ounce
model in an inflated dome, it is almost the
same as flying outdoors—no problem!
However, when you get down to a doubleor
even single-size gymnasium, you get the
feeling that you are always turning the
airplane; there isn’t enough space for
appreciable straightaway flight.
Inside a dome my aircraft have
occasionally hit walls or even the top dead
center of the ceiling. Being such lightweight
models, they seem to just bounce off these
soft surfaces. Most of the time I lose altitude
but can easily recover the airplane to normal
flight.
On the other hand, at the Toledo, Ohio,
PERF (Perrysburg Electric River Fliers)
indoor fly a couple years ago (when it was a
smaller facility), I “shot a basket” with my
little 4.7-ounce AIKA. We had to get a large
stepladder to remove the model from the
basketball hoop/net.
However, before you start worrying about
these possibilities, consider that at such light
weights and wing loadings, not much ever
happens to micromodels—except for midair
52 MODEL AVIATION
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07sig2.QXD 4/26/04 8:34 am Page 52
July 2004 55
collisions! They do occur every once in
awhile, but if you build your entire model
from a single sheet of balsa, it’s no big deal!
NIRAC: AMA encourages SIGs to help
organize the various groups within model
aviation. We are lucky to have the National
Indoor Remote-Control Aircraft Council
(NIRAC) represent indoor RC flying within
the Academy. National Indoor Electric
Duration record-holder Bob Wilder of Texas
founded the organization several years ago.
You can access the Web site containing all
of the general information about this SIG at
www.nirac.org. Look it up, get familiar with
the organization, and show your support by
joining.
Once a year NIRAC sponsors a major
indoor RC championship. The 2004 dates are
June 4-6, and the location, as in the past, will
be the big Oakland Yard Athletics facility (an
inflated dome) in Waterford, Michigan
(www.oaklandyard.com/model_aviation.htm).
The flying plan for the three days includes
official indoor RC events including Scale,
racing, cargo lift, Old-Timer climb-and-glide,
endurance, and RC gliders. Between the
events the dome will be opened up for funflying
by all who attend.
NIRAC can also help you find local domes
and large indoor flying facilities. The current
NIRAC president—Dave Robelen—is one of
the most experienced indoor/micro RC fliers.
With indoor RC growing extraordinarily
rapidly, there is much to be learned; new
technology seems to emerge almost weekly.
The big, annual NEAT (Northeast Electric
Aircraft Technology) Fair held in upstate New
York, near the town of Downsville, includes a
series of indoor RC lectures during the three
days of the event.
Sergio Sigras coordinates these seminars.
Some of the most important names in
microflight—Henry Pasquet, Gordon
Johnson, Matt Keennon, Nick Leichty, Fred
Marks, Clarence Hurd, Bob Selman, and
more—provide the latest indoor RC
information.
For the Saturday night of the Fair, Gordon
Johnson sets up an indoor RC flight
demonstration in a double-size gym at nearby
Walton Senior High School. Guest lecturers
get to show their stuff, to the delight of
hundreds of spectators. To learn more about
the Fair, visit www.neatfair.org.
When you are attempting to gain
permission to fly indoor RC at local school
facilities, offer to lecture and/or give classes at
the school to offset your using the venue.
“Yes, you can use our gym, but why not come
in and let our young people learn how they
can participate?”
References: NIRAC is a good starting point.
Several publications regularly offer many
articles about indoor RC. Air Age Media’s RC
MicroFlight is available in hard-copy form
and online. It has been in production for more
than three years. When you subscribe, you
obtain a password that allows you access to all
previously published articles. You can even
download plans from the construction articles.
MA has two talented authors who write
alternating bimonthly columns. Dave Robelen
writes “Micro-Flying” (featuring indoor RC
and parking lot flying) and Paul Bradley
writes “Small-Field Flying” (covering parking
lot flying and backyard flying, and hitting on
indoor RC). I highly recommend these.
You can count on Quiet Flyer, under the
direction of publisher Wil Byers, for many
indoor RC-oriented articles each month. This
magazine specializes in electric power and
sailplane activities.
Flying Models magazine also has
alternating columnists who spend considerable
time in the world of indoor RC: Don Belfort
and Stew Meyers. For many years, RC
Modeler magazine has featured Jim Zare, who
now concentrates most of his activities on
micro and indoor flying.
I hate to sound too commercial, but
roughly two years ago I wrote the book
Getting Started in Backyard Flying. It
contains a lot of material about indoor RC.
You will see how parking lot/backyard flyers
tend to complement the indoor RC flyer. This
book is available from AMA, Tower Hobbies,
Balsa Products, and the publisher’s Web site:
www.rcstore.com/rs/general/books.asp.
In the late 1960s, people such as Dave
Robelen, John Worth, and Howard McEntee
experimented with multichannel proportional
RC control of glow-fueled models that
07sig2.QXD 4/26/04 8:34 am Page 55
weighed only 5-8 ounces! Those airplanes and
their equipment were tedious to work with,
but they did fly.
Soon afterward, AMA Hall of Famer Bill
Cannon of Cannon Electronics produced a
subminiature RC system that made smallscale
RC-model flying practical for everyone.
Bill continued to make that equipment for
many years and should be congratulated for
his efforts and dedication to small-model RC
flying.
Recently we have been privileged to see
the development of micro RC systems, servos,
actuators, Li-Poly batteries, tiny motors, and a
growing group of dedicated RC modelers who
have been willing to make this endeavor
grow. With modern large inflatable domes,
field houses, etc., it is now possible to enjoy
RC flying during all kinds of weather, at any
time of day or night.
Want to have some more fun in RC? Try
flying indoors. MA
Bob Aberle
[email protected]
Manufacturers/distributors:
Firefly coreless micro motors—direct and
geared:
AstroFlight Inc.
www.astroflight.com
GWS motors, propellers, Li-Poly batteries:
Balsa Products
www.balsapr.com
Li-Poly batteries:
Batteries America
www.batteriesamerica.com
JMP receivers, magnetic actuators, Li-Poly
chargers:
Bob Selman Designs
http://users.joplin.com/~bselman/
Voltage cutoff programmable ESCs:
Castle Creations
www.castlecreations.com
Assortment of micro hardware and products:
Cloud 9 RC (John Worth)
(703) 273-0607
Hard-to-get gears, motors, propellers, wire,
connectors:
David Lewis
www.homefly.com
Profile Roadkill series stand-off scale models:
DJ Aerotech
www.djaerotech.com
RFFS-100 micro RC systems, magnetic
actuators, JMP receivers, four-channel
conversion RFFS-100s:
Dynamic Web Enterprises (DWE)
www.smallrc.com
Reduced-size receiver antennas:
E Cubed R/C
www.azarr.com
Magnetic actuators, control-linkage
accessories, connectors:
EFlight Designs
www.eflightdesigns.com
Li-Poly batteries, chargers:
E-Tec (Air Craft)
www.aircraft-world.com
M5 micro DC receivers, submicroservos,
Kokam Li-Poly batteries, chargers:
FMA Direct
www.fmadirect.com
Penta 2.4-gram receivers, GDservo 1.33-gram
servos, new proportional magnetic actuators:
Gasparin
56 MODEL AVIATION
www.gasparin.cz
Motors, propellers, wheels, accessories:
Grand Wing Servo-Tech (GWS)
www.gws.com.tw
Cirrus Micro Joule receivers, ESCs, 3-gram
servos:
Global Hobby Distributors
www.globalhobby.com
Triton Li-Poly chargers:
Great Planes Model Distributors
www.electrifly.com
www.greatplanes.com
HS-50 submicroservo:
Hitec RCD
www.hitecrcd.com
Cirrus Micro Joule receiver, ESC, 3-gram
servos:
Hobby Club
www.hobbyclub.com
Motors, JR radios, Hobby Zone ARF indoor
models, Thunder Power Li-Poly batteries:
Horizon Hobby (GWS)
www.horizonhobby.com
Assortment of tiny direct- and gear-drive
motors:
Kenway Motors
(908) 850-9571
GWS motors, propellers, Li-Poly batteries:
Maxx Products International
www.maxxprod.com
ARF and RTF indoor models:
Megatech
www.megatech.com
Li-Poly batteries, connectors, wire:
Radical RC
www.radicalrc.com
Berg receivers:
RC Direct
www.rc-direct.com
Tiny geared motors, scale model kits:
RCS Technik (Chris Stewart)
www.falconmodels.uk.com
Microreceivers, ESCs, Li-Poly batteries,
chargers, model kits:
Sky Hooks and Rigging
www.microrc.com
Li-Poly batteries:
Thunder Power (Advanced Energy
Technology Inc.)
(702) 228-8883
Indoor model kits and supplies:
Todd Long Models
www.toddsmodels.com
Li-Poly chargers, ARF and RTF model kits:
Tower Hobbies
www.towerhobbies.com
7865 Mill Road, Elkins Park, PA. 19027 USA
Tel. 215 635 6520 Orders ONLY 888 721 0128 Fax. 215 635 4951
Email [email protected] www.sonictronics.com.
NEW
McDaniel R/C A Division of Sonic-Tronics Inc.
Patents, copyrights
and trademarks are
applied.
The New “Go-Slo III” has been
improved with added features.
With the precise performance of
an 8 bit microprocessor the output
is now “user selectable”. Two models are available. One can
drive a single servo, two servos in tandem, two servos with one
reversed or all three servos at once. The other model drives one,
two or three servos in parallel. Both models allow the servo speed to be
adjusted, 2 to 10+ seconds of travel in either direction. Go-Slo III units
are great for precise operation of Flaps, Gear etc. The receiver cable is now a
heavy 22 gage for better power delivery to one, two or three servos.
Go-Slo III‘s are compatible with 4.8 or 6 Volt systems and all proportional servos.
The unit is 1.5” x 1.5”x 3/4” and only .9 oz in weight.
07sig2.QXD 4/26/04 8:34 am Page 56
Edition: Model Aviation - 2004/07
Page Numbers: 42,43,44,45,46,48,50,52,55,56
Edition: Model Aviation - 2004/07
Page Numbers: 42,43,44,45,46,48,50,52,55,56
42 MODEL AVIATION
Introduction to
Indoor Radio Control
I WROTE A feature article published in last
month’s MA titled “Introduction to Parking
Lot Flying.” That category involves flying
relatively small, easy-to-build, and relatively
inexpensive RC models close in.
Aircraft in that size category (up to
roughly 16 ounces total weight) can also,
under certain circumstances, be flown in
indoor facilities. From a practical standpoint,
the larger parking lot-size models can be
flown easily and safely in extra-large indoor
facilities such as golf practice domes
(inflatable) and field houses used for football
practice.
Since winter weather hits many areas
of our country, indoor RC flying during
those months is increasing in popularity.
Not everyone has a golf dome or a field
house in his or her community, but almost
everyone has a school gymnasium or
auditorium that can be an excellent
substitute. To be able to use these smaller
indoor flying facilities, you have to
by Bob Aberle
Author’s original-design Kiwi weighs just 3.4 ounces with 100-
square-inch wing. It uses FMA Direct M5 receiver and two FMA
Direct PS-20 submicroservos. Battery power is two 145 mAh Li-
Poly cells.
Dynamic Web Enterprises proprietors Dan Hurd (L) and his dad
Clarence. Dan holds 1-ounce Pitts Special biplane; Clarence
holds his own-design Lil Skeeter.
Another Joe Wagner FF design from the early
1950s: the Dakota biplane. At right is originalsize
model powered by .049 glow engine. The
author built reduced-size version (left) which
weighs 1.3 ounces with 69 square inches of total
wing area. Power is single 145 mAh Li-Poly
battery. Construction article and plans were
published in May 2003 RC MicroFlight.
Author holds 3.8-ounce version of
popular Joe Wagner FF design—
The Sioux—from the early 1950s.
It has 90-square-inch wing and is
powered by GWS LPS/B2C-C
motor and two FMA Direct/Kokam
340 mAh HD Li-Poly cells. Will
soon be featured as construction
article in Quiet Flyer magazine.
The 2004 NIRAC Indoor Championships will be held
at the big Oakland Yard Athletics facility in Waterford MI.
Fun-flying will be permitted before contest rounds.
All are invited!
07sig2.QXD 4/26/04 8:23 am Page 42
July 2004 43
Pair of typical magnetic actuators. They have a moving magnet within a
coil. Exact separation between two coils and the fact that they are at right
angles to one another provide for control position centering.
Todd Long of Todd’s Models has been selling his Tiny for several years.
Depending on motor and battery choice, this excellent-flying design can
weigh approximately 4 ounces and provide considerable indoor RC funflying.
Don Stackhouse of DJ Aerotech holds two of his Roadkill-series
profile sport-scale models: an Me 109 (L) and a Ryan ST. Each
weighs roughly 3-3.5 ounces and operates on two Li-Poly
batteries.
Closer view of Clarence Hurd’s Lil Skeeter, which was
designed around DWE’s RFFS-100 micro RC system. It
has 46 square inches of wing area and weighs 23 grams
(.81 ounce) including single 130 mAh Li-Poly battery.
Motor is KP-00 geared at 2.67:1.
The Lightning RTF foam model was originally
intended to be an electric-powered FF. An
excellent conversion article by Greg Covey
detailing how to install the DWE RFFS-100 micro
radio system is on the DWE Web site.
DWE RFFS-100 micro RC system is extremely
popular. On this one, PC board weighing 1.8
grams is an RC receiver, ESC, and two magnetic
actuator drivers. It’s one of the best starting
points for flying RC models at or near 1-ounce
total weight.
Photos courtesy the author
07sig2.QXD 4/26/04 8:26 am Page 43
Let’s get into the details of these small, or as we call them, “microsize”
RC aircraft.
Micromodel Sizing: Micro-size models dedicated to indoor RC
flying can range from roughly 8 ounces total weight down to only a
few grams. For this presentation I’m concentrating on 4 ounces total
weight and less.
Right now the range of 4 ounces down to approximately 2.5
ounces can be enjoyed while employing the
available equipment technology, and at
relatively moderate prices. From 2.5 ounces
down to roughly .75 ounce, you will need one
of the several submicroservos on the market
or magnetic actuators. For less than .75 ounce
down to a few grams, you need highly
specialized equipment and considerable
model-building skills.
Typical 4-ounce models can have
approximately 80-120 square inches of wing
area, which will yield wing loadings in the
range of roughly 4-6 ounces/square foot. The
4-ounce total weight could consist of 2.25
ounces of equipment (receiver, two servos,
Li-Poly battery, motor, propeller, and motor
speed controller). The remaining 1.75 ounces
includes the model structure (including
covering, finish, wheels, hinges, and control
linkages).
This typical 4-ounce model can employ
traditional RC equipment, but it will be
smaller in size and weight. The servos will
consider reducing your RC model’s size and weight.
The subject of this presentation is flying RC indoors with models
that weigh less than 3 or 4 ounces. As I noted, there are certain
situations in which you can fly a parking lot model inside. There are
also times in which you can fly a 1-ounce RC model outdoors. To do
that, you need to seek out the dead-calm early-morning or -evening
air. Calm-air outdoor flying also lends itself well to backyard-type
flying, making it a perfect family hobby/sport!
44 MODEL AVIATION
Popular little KP-00 geared motor and companion 3-inch-diameter
propeller. Several sources sell this motor, as noted in text. Power
range is intended for .75- to roughly 1.5-ounce models!
Rear of FMA Direct M5 dual-conversion receiver, which is
smallest dual-conversion RC receiver on the market. It is
available on 72 MHz and six-meter RC channels. Weighs .35
ounce with case!
Basic RC system for 2.5- to 4-ounce model weight (L-R): Castle
Creations Pixie-7P ESC, FMA Direct M5 dual-conversion
microreceiver, two FMA Direct PS-20 submicroservos, two-cell
FMA Direct/Kokam 340 mAh HD Li-Poly battery pack.
Power, RC system needed to fly 1-ounce total-weight model.
Left: KP-00 geared motor, 3-inch-diameter propeller. Top center:
Pair of EFlight Designs magnetic actuators to operate rudder,
elevator. Top right: A 145 mAh Li-Poly battery cell. Just below
that is DWE RFFS-100 PC board containing receiver, ESC, two
magnetic actuator drivers. Lower right: Azarr’s E Cubed RC
reduced-size receiver antenna.
Cutaway of GWS LPS/B2C-C geared motor
mounted to 3⁄16-inch wood dowel. A
setscrew holds motor in place. Two
plywood formers support dowel. It’s
simple and effective! You can easily
change motor at flying site.
Dave Burley has been developing
microservos for indoor RC fliers’ benefit.
His latest (shown) is 1-gram proportional
feedback ultramicroservo. He demonstrated
it to many indoor RC experts at 2003 NEAT
Fair. Dave wants to interest a prominent
manufacturer to pick up on production
rights for it. It worked well, and he hopes it
can be produced at a reasonable unit price.
07sig2.QXD 4/26/04 8:28 am Page 44
July 2004 45
provide regular proportional control, operating from a conventional
RC transmitter.
I have a little indoor sport model that I’m flying at 74 square inches
of wing area and 1.2 ounces total weight. The wing loading works out
to only 2.3 ounces/square foot. It employs two magnetic actuators, and
a 145 mAh Li-Poly battery cell provides all the power. When flown
outdoors, this model doesn’t like any wind! I’ll get into the specifics of
the RC equipment later.
Safety: As is the case with parking lot flying, indoor RC flying has
certain safety issues about which you should be concerned. Even
though you are flying inside, radio signals can travel through buildings
easily without much attenuation of strength. Someone might be flying
right outside your indoor facility, so please check around first. It’s best
to check local hobby shops and RC clubs too.
Also safety related is your model’s speed in flight. An airplane
with less than 100 square inches of wing area and weighing
approximately 10 ounces might be capable of speeds in excess of 60-
75 mph. If it hits something or someone, it could cause physical or
property damage.
Common sense must prevail and reasonable weights and flying
speeds must be commensurate with the size of the facility. A leadertype
person should be in charge of each flying session. That person
must have the last word on who can or can’t fly, and his/her judgment
must be respected at all times!
Micromodel Design: I’ve already suggested weights and wing
loadings, and soon I will get into power systems. There aren’t many
ARF models in the less-than-4-ounce category; that might be
considered the bad news. The good news is that a 4-ounce airplane
can, for the most part, be constructed from scratch, with a minimum of
materials and a minimum of assembly time and skills. I’ve built 1-
ounce RC models from a single sheet of 1⁄32 x 3 x 36-inch balsa. That
is almost as inexpensive as you can go!
The 2- to 4-ounce models can often be built up from the many
rubber-powered kits on the hobby market. Doing this has become
popular. Another possibility are the profile semiscale models, such as
DJ Aerotech’s Roadkill series. Those are easy to build, inexpensive,
and are even supplied with the recommended motor.
If you want to try a 1-ounce model for the first time, the best
trainer is the Lil Skeeter designed by Clarence Hurd of Dynamic Web
Enterprises (DWE). This design was reviewed in the June 2002 RC
MicroFlight newsletter. Plans are available from DWE, and you
receive a free plans copy when you purchase the DWE RFFS-100
micro RC system.
A more ambitious project is Dave Robelen’s Walker, which he
Former AMA executive director and RC MicroFlight founding
editor John Worth holds Pee Wee Flyer made by Estes (the
rocket people). Wal-Mart stores throughout the country sell this
RTF for only $19.95. An article describing it was published in
the October 2003 RC MicroFlight.
Sky Hooks and Rigging owner Tom Mc Cann holds his little
Mosquito indoor slow flyer that Ken Coleman designed. It is
available from Tom as a kit. It spans 24 inches, has 131 square
inches of wing area, weighs 2.25 ounces, and flies on single Li-
Poly battery cell.
Micro-Pod is Bob’s latest original-design indoor RC model. A
construction article was published in November 2003 RC
MicroFlight. It weighs 1.2 ounces and has 74-square-inch wing
area. Power is geared KP-00 motor operating on single 145 mAh
Li-Poly cell.
calls an “ultralite indoor floater.” Dave went to the other extreme and
designed a 1-ounce model with an amazing 357 square inches of wing
area. The resulting wing loading works out to only .4 ounce/square
foot and provides flying speeds of just 3-4 mph. You can walk under
this model while it is flying. The Walker was featured in the July 2003
RC MicroFlight.
07sig2.QXD 4/26/04 8:30 am Page 45
Henry Pasquet is probably the most famous indoor RC flier. His
goal for years has been to build smaller and smaller models. He
holds his 4-inch-span Lacy M-10. It weighs 2.6 grams (total) with a
Gasparin G2.6 CO2 engine. RC system is by Nick Leichty. One No.
337 silver-oxide battery powers the system. It flies very well despite
its size!
US Airways Captain Joe Malinchak’s super-detailed Piper L-4
Grasshopper is military version of Piper Cub. Weighs 1.3 ounces
total including complete scale cockpit interior, landing-gear
shocks, etc. Has geared KP-00 for power! Joe earned DWE award at
2003 NIRAC Championships for RC Scale model with highest
points and weighing less than 1.5 ounces!
NIRAC president, MA columnist, and newly inducted Indoor RC Hall
of Fame member Dave Robelen holds his Scale 34-inch-span Piper
Vagabond. It has 200 square inches of wing area and weighs 4
ounces ready to fly. Power is a DC 5-2.4 coreless motor geared 7.5:1,
running on seven-cell 50 mAh battery pack.
Matt Keennon’s tiny electric-powered Scale P-38 twin spans only
10.5 inches and weighs 35 grams (1.23 ounces) with two M-20
motors and two Kokam 145 mAh Li-Poly cells in parallel. Flight
demos at NEAT Fair were spectacular. Matt makes a living
working on government-sponsored micromodel projects.
Nick Leichty, known for his ultramicro RC models, holds his
Micro Aero Master biplane at 2003 NEAT Fair. It employs one of
his micro three-channel RC systems powered by 4mm motor and
a 40 mAh Li-Poly battery. Model spans 5.5 inches and has 5.5-
gram (.19-ounce) total weight. Approximate flight time on a
charge is five minutes. The author saw the flights and couldn’t
believe it!
46 MODEL AVIATION
07sig2.QXD 4/26/04 8:32 am Page 46
Power Systems: Indoor power systems
primarily involve electric motors, be they
direct drive or gear driven. CO2 power
(compressed gas) is used to some extent, but
the ability to throttle these engines is still in
the experimental stages. Although some of
the tiny glow-fuel and diesel engines might
find their way into indoor RC flying, the
combination of noise and exhaust fumes
makes it somewhat impractical.
Small motors are becoming more and
more popular, and the prices keep going
down. This past year, Grand Wing Servo-
Tech (GWS)—a huge parking lot-/indoormodel
manufacturer—introduced a tiny
geared motor that it calls the “LPS” series.
One of the motors in this category—the
GWS/LPS/B2C—weighs only approximately
12 grams (.42 ounce). It is available in three
gear ratios (4:1, 5:1, 6.2:1).
I’m presently using the 6.2:1 geared
version, which operates on two Li-Poly
battery cells (nominal 7.4 volts) at 700 mA
motor current and 6-watt power level. Using a
GWS 6 x 5 propeller, I generate more than
enough thrust to fly a 4-ounce RC model.
These motors sell for roughly $10. How can
you go wrong?
The .75-1.5-ounce models are generally
powered by pager-derivative motors such as
the Knight & Pridham KP-00 (of which there
are several models with different windings),
with gearing ranging from 2.75:1 upward of
6:1. Each specific gear ratio requires a
different size propeller. Propeller diameters
range from 3 to 6 inches. The gearing choices
attempt to get the most thrust from the motor
while drawing the least current. This is the
game you must play with electric-powered
flight.
The little KP-00 motor will work well on
a single Li-Poly cell drawing roughly 700 mA
of current at approximately a 3-watt power
level. The trick with this is to be able to get an
RC system (receiver and servos) that can also
operate reliably from a single Li-Poly cell at
roughly 3.6 volts.
There are receivers that will do that,
especially those used in conjunction with
magnetic actuators. Bob Selman Designs
offers a new voltage-doubler unit that takes
the single cell voltage and increases it to
roughly 5 volts for more reliable RC
operation.
Many smaller motors are becoming
available for the indoor RC experimenter who
wants to keep reducing that total model
weight to as little as a few grams. Experts
such as Henry Pasquet and Nick Leichty are
regularly flying models weighing roughly .3
ounce! You can find tales of their
experimental efforts in RC MicroFlight. But
as I pointed out before, these truly micro RC
models require a great deal of experience and,
most of all, patience!
As this is being written, I have heard
about several micro manufacturers who have
prototype miniature brushless motors and
companion speed controllers in the works. A
lightweight, highly efficient brushless motor
will provide yet another breakthrough in
indoor RC.
Before leaving the power scene, I’ll
mention that there are CO2 motors now
available for RC model use. They are still
comparatively expensive, but a model’s
weight can be reduced even further than with
electric power because the CO2 tank weighs
less than a battery.
The biggest problem until recently has
been the ability to throttle these air-operated
motors. Stefan Gasparin in the Czech
Republic has made remarkable progress in
this regard. I urge you to look at his Web site.
ESCs: Even the electric motor speed
controllers have been shrunken to fit the
needs of our micro-size aircraft. I think it’s
safe to state that all of the micro ESCs have a
BEC, which allows for the sharing of the one
battery pack.
As you will soon learn, the new Li-Poly
battery technology requires that no cell drop
to less than 3.0 volts when in use. This is a
minimum discharge point. To be on the safe
side, a micro ESC’s low voltage cutoff point
should be set to increments of 3.0 volts per
cell. If you are using one Li-Poly cell, the
cutoff should be 3.0 volts. If your pack has
two Li-Poly cells the cutoff should be 6.0
volts, and so on.
Castle Creations’ Pixie-7P ESC allows
you to program the voltage cutoff point.
There aren’t that many choices, but they will
improve in time. Setting the voltage cutoff on
07sig2.QXD 4/26/04 8:33 am Page 48
the Pixie isn’t all that easy and does require
some patience, but this is the concept you
want to look for in the future!
Batteries: Until recently, the batteries of
choice for 4-ounce and lighter models were
the 100-125 mAh NiMH types, usually in
packs consisting of seven or eight cells. In the
past year we have been introduced to a new
form of battery known as the Li-Poly. These
new cells provide more capacity in a lighterweight
package. Both of those parameters are
exactly what you want for micro RC models.
Of equal interest is the fact that each Li-
Poly cell has a characteristic voltage of close
to 4.0; the older Ni-Cd/NiMH cells had only
1.2 volts per cell. So two Li-Poly cells work
like a six- or seven-cell Ni-Cd/NiMH pack.
We typically see two-cell packs consisting
of 145 mAh or 340 mAh powering 3- to 4-
ounce RC models. A two-cell 145 mAh Li-
Poly pack weighs 8.7 grams (.31 ounce) and
can fly that 3- to 4-ounce model at 700 mA
current (6 watts) for 10-12 minutes and more,
depending on how you throttle the motor in
flight. And two of the 340 mAh Li-Poly cells
(weighing 20.1 grams, or .71 ounce) could
provide up to 30 minutes of motor run time.
However, Li-Poly cells are still quite new
on the market, and they must be taken care of
very carefully. They require a special
dedicated charger and should not be charged
with more than a 1C current, which takes
roughly an hour. Li-Poly batteries should not
be discharged to less than 3.0 volts per cell.
Li-Poly cells are also currently somewhat
limited in their load capabilities. Initial
offerings could only provide loads up to
approximately 5C (five times the capacity of
the battery). Recently a new variety of Li-
Poly cell has been introduced that can stand
loads upward of 20C (quite an
improvement!).
Li-Poly batteries is a subject unto itself. I
wrote a comprehensive article titled
“Introduction to Lithium-Polymer Batteries”
that was published in the May 2004 MA. If
you haven’t read that piece, I highly
recommend that you do so before attempting
to use Li-Poly batteries in a model airplane of
any kind.
Micro RC System and Components: The RC
equipment is conventional technology, but is
obviously made smaller and lighter. An
inexpensive microreceiver is the GWS R-4P,
which has four-channel capability, is a singleconversion
circuit, and weighs 6.8 grams (.25
ounce). At approximately $30, it is a great
buy.
For those who want good range and
selectivity, in a crowded flying environment,
the FMA Direct M5 dual-conversion receiver
is an excellent choice, especially in the 2.5- to
4-ounce-model weight class. The M5 weighs
9.5 grams (.35 ounce).
Another outstanding choice is the Berg-
5*DSP at .35 ounce and the new Berg-4*DSP
Micro Stamp at just .25 ounce. The Berg
receivers are available from RC Direct. With
the Berg and FMA Direct receivers, you can
remove the receiver case for a further weight
reduction.
For the extra-small models (1.5 ounces
and lighter), the DWE RFFS-100 has been the
popular microsystem for some time. It is a
microreceiver, a built-in ESC with BEC, and
drivers for two magnetic actuators on a single
PC board. The entire board weighs only 1.8
grams (.06 ounce!).
The RFFS-100 receiver is not very
selective, so you can’t use several channels on
either side of your operating frequency when
flying. But this system has provided a load of
indoor RC fun-flying under the right
conditions.
Jean-Marie Piednoir (JMP) of France
makes a new and more selective
microreceiver which Bob Selman Designs
sells in the US. This receiver is claimed to be
extremely narrow band (selective!) and
includes an ESC and two magnetic actuator
drivers. It weighs 2.2 grams (.08 ounce), and
the price without connectors is $89. I’m sure
we will be seeing plenty of these units put
into indoor RC service in the near future.
As I was writing this, I learned of the new
Gasparin Penta 2.4-gram (.8-ounce) fourchannel
receiver, which is claimed to be
incredibly selective and will be selling in the
US at a reasonable $39.
In addition to receivers, servos or actuators
are also important. Conventional servos,
meaning regular proportional feedback
servos, are available at roughly 5.6 grams (.20
Each of these fine Foam Fun Scale ARF airplane kits
include a “Plug & Fly” Speed 280 motor with Kavan K1
Gold Connectors, SPF Gearbox, APC prop, wheels, scale
decals, hardware, and illustrated instructions.
See your local hobby dealer or visit us at www.sigmfg.com.
Kavan RC is a subsidiary of SIG Manufacturing Company, Inc. • P.O. Box 520 • Montezuma, Iowa 50171-0520
Albatros D.V.
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Fine Electric Powered Slow/Park Flyers For The Pilot In The Know
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Web Site: www.sigmfg.com • Phone: (641)623-5154
Fokker Dr. 1
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07sig2.QXD 4/26/04 8:33 am Page 50
ounce). Two come to mind: the popular Hitec
HS-50 and the new FMA Direct PS-20. Each
sells for less than $30 and has been reliable.
The German WES-Technik company has
been making a linear-output-type microservo
for the past couple years. It weighs 2.1 grams
(.07 ounce) but is comparatively expensive at
$70-$80 (US).
Stefan Gasparin in conjunction with Didel
(the Swiss gear company) has designed a new
GDservo, which has a rotary output and
weighs 1.33 grams without a case. It will be
pricey, at $98 (US). Stefan also has a new
concept he calls a “Proportional Magnetic
Actuator.” I’ve seen some photos, and the
idea looks entirely realistic. Price is said to be
$39 each (US).
At the bottom of the weight scale are the
truly magnetic actuators; these are coil
devices with magnets that move inside the
coils. They require some patience to install
and offer little control force. That means your
hinges and control linkages must offer the
least possible friction. These magnetic
actuators make RC models of less than 1
ounce total weight possible. Good sources of
magnetic actuators include Bob Selman
Designs, Cloud-9 RC, E-Flight Design, and
DWE.
One last reference is to a “brick” design,
which was popular in the early 1970s. FMA
Direct is almost ready to release a microbrick
that will include one PC board, a narrow-band
receiver, ESC, control actuator drivers, and
two servos or two magnetic actuators. Placing
all of the components on a single board can
make certain installations impractical, but the
bottom line is that the brick eliminates a great
deal of wiring and connectors, thereby
reducing the overall weight. I believe this
concept will find a home in the 2.5- to 4-
ounce model category.
Connectors: The connectors and the wire size
(gauge, which refers to diameter) are
important. You want to carry the current
involved and no more; using a connector that
is too large or a wire with too large a diameter
only adds weight to little airplanes that can’t
afford it.
The larger parking lot-size models can
properly use the popular Anderson Power
Pole-type connectors (also known as Sermos
connectors). You can use these from roughly
6 amps of current up.
The Deans four-pin connectors are popular
for 3 to 6 amps of current. It is a good idea to
gang two pins to make a single connection. In
that case, the four pins yields two conductors.
From 1.5- to 3-amp current, the JST red
plastic housing connector is fine. For less than
1.5 amps of current, the JST white plastic or
Cloud 9 RC Unisex connectors will do the
job.
EFlight Designs carries an excellent line of
submicroconnectors. Wire size can start with
16 gauge for the 8- to 10-amp current. As you
work your way down in current, the wire
gauge can go from 22 to 28, and even 32.
Your hobby supplier can recommend the best
size for each current level. The JST
connectors come with the wire already
attached.
Indoor Flying Tips: If you are already an RC
sport flier or a parking lot flier, you are
certainly qualified to fly indoors; but the
generally “restricted” airspace can be
extremely challenging at times. If you are
lucky enough to be able to fly a 4-ounce
model in an inflated dome, it is almost the
same as flying outdoors—no problem!
However, when you get down to a doubleor
even single-size gymnasium, you get the
feeling that you are always turning the
airplane; there isn’t enough space for
appreciable straightaway flight.
Inside a dome my aircraft have
occasionally hit walls or even the top dead
center of the ceiling. Being such lightweight
models, they seem to just bounce off these
soft surfaces. Most of the time I lose altitude
but can easily recover the airplane to normal
flight.
On the other hand, at the Toledo, Ohio,
PERF (Perrysburg Electric River Fliers)
indoor fly a couple years ago (when it was a
smaller facility), I “shot a basket” with my
little 4.7-ounce AIKA. We had to get a large
stepladder to remove the model from the
basketball hoop/net.
However, before you start worrying about
these possibilities, consider that at such light
weights and wing loadings, not much ever
happens to micromodels—except for midair
52 MODEL AVIATION
Since 1948 Fox Manufacturing
Company has been producing
high quality model airplane
engines, glow plugs and other
accessories. Fox has become a
name modelers can trust when
it comes to durability, power,
and performance at an
affordable price. (479) 646-1656
Fax (479) 646-1757
5305 Towson Avenue
Fort Smith, AR 72901
www.foxmanufacturing.com
email: [email protected]
07sig2.QXD 4/26/04 8:34 am Page 52
July 2004 55
collisions! They do occur every once in
awhile, but if you build your entire model
from a single sheet of balsa, it’s no big deal!
NIRAC: AMA encourages SIGs to help
organize the various groups within model
aviation. We are lucky to have the National
Indoor Remote-Control Aircraft Council
(NIRAC) represent indoor RC flying within
the Academy. National Indoor Electric
Duration record-holder Bob Wilder of Texas
founded the organization several years ago.
You can access the Web site containing all
of the general information about this SIG at
www.nirac.org. Look it up, get familiar with
the organization, and show your support by
joining.
Once a year NIRAC sponsors a major
indoor RC championship. The 2004 dates are
June 4-6, and the location, as in the past, will
be the big Oakland Yard Athletics facility (an
inflated dome) in Waterford, Michigan
(www.oaklandyard.com/model_aviation.htm).
The flying plan for the three days includes
official indoor RC events including Scale,
racing, cargo lift, Old-Timer climb-and-glide,
endurance, and RC gliders. Between the
events the dome will be opened up for funflying
by all who attend.
NIRAC can also help you find local domes
and large indoor flying facilities. The current
NIRAC president—Dave Robelen—is one of
the most experienced indoor/micro RC fliers.
With indoor RC growing extraordinarily
rapidly, there is much to be learned; new
technology seems to emerge almost weekly.
The big, annual NEAT (Northeast Electric
Aircraft Technology) Fair held in upstate New
York, near the town of Downsville, includes a
series of indoor RC lectures during the three
days of the event.
Sergio Sigras coordinates these seminars.
Some of the most important names in
microflight—Henry Pasquet, Gordon
Johnson, Matt Keennon, Nick Leichty, Fred
Marks, Clarence Hurd, Bob Selman, and
more—provide the latest indoor RC
information.
For the Saturday night of the Fair, Gordon
Johnson sets up an indoor RC flight
demonstration in a double-size gym at nearby
Walton Senior High School. Guest lecturers
get to show their stuff, to the delight of
hundreds of spectators. To learn more about
the Fair, visit www.neatfair.org.
When you are attempting to gain
permission to fly indoor RC at local school
facilities, offer to lecture and/or give classes at
the school to offset your using the venue.
“Yes, you can use our gym, but why not come
in and let our young people learn how they
can participate?”
References: NIRAC is a good starting point.
Several publications regularly offer many
articles about indoor RC. Air Age Media’s RC
MicroFlight is available in hard-copy form
and online. It has been in production for more
than three years. When you subscribe, you
obtain a password that allows you access to all
previously published articles. You can even
download plans from the construction articles.
MA has two talented authors who write
alternating bimonthly columns. Dave Robelen
writes “Micro-Flying” (featuring indoor RC
and parking lot flying) and Paul Bradley
writes “Small-Field Flying” (covering parking
lot flying and backyard flying, and hitting on
indoor RC). I highly recommend these.
You can count on Quiet Flyer, under the
direction of publisher Wil Byers, for many
indoor RC-oriented articles each month. This
magazine specializes in electric power and
sailplane activities.
Flying Models magazine also has
alternating columnists who spend considerable
time in the world of indoor RC: Don Belfort
and Stew Meyers. For many years, RC
Modeler magazine has featured Jim Zare, who
now concentrates most of his activities on
micro and indoor flying.
I hate to sound too commercial, but
roughly two years ago I wrote the book
Getting Started in Backyard Flying. It
contains a lot of material about indoor RC.
You will see how parking lot/backyard flyers
tend to complement the indoor RC flyer. This
book is available from AMA, Tower Hobbies,
Balsa Products, and the publisher’s Web site:
www.rcstore.com/rs/general/books.asp.
In the late 1960s, people such as Dave
Robelen, John Worth, and Howard McEntee
experimented with multichannel proportional
RC control of glow-fueled models that
07sig2.QXD 4/26/04 8:34 am Page 55
weighed only 5-8 ounces! Those airplanes and
their equipment were tedious to work with,
but they did fly.
Soon afterward, AMA Hall of Famer Bill
Cannon of Cannon Electronics produced a
subminiature RC system that made smallscale
RC-model flying practical for everyone.
Bill continued to make that equipment for
many years and should be congratulated for
his efforts and dedication to small-model RC
flying.
Recently we have been privileged to see
the development of micro RC systems, servos,
actuators, Li-Poly batteries, tiny motors, and a
growing group of dedicated RC modelers who
have been willing to make this endeavor
grow. With modern large inflatable domes,
field houses, etc., it is now possible to enjoy
RC flying during all kinds of weather, at any
time of day or night.
Want to have some more fun in RC? Try
flying indoors. MA
Bob Aberle
[email protected]
Manufacturers/distributors:
Firefly coreless micro motors—direct and
geared:
AstroFlight Inc.
www.astroflight.com
GWS motors, propellers, Li-Poly batteries:
Balsa Products
www.balsapr.com
Li-Poly batteries:
Batteries America
www.batteriesamerica.com
JMP receivers, magnetic actuators, Li-Poly
chargers:
Bob Selman Designs
http://users.joplin.com/~bselman/
Voltage cutoff programmable ESCs:
Castle Creations
www.castlecreations.com
Assortment of micro hardware and products:
Cloud 9 RC (John Worth)
(703) 273-0607
Hard-to-get gears, motors, propellers, wire,
connectors:
David Lewis
www.homefly.com
Profile Roadkill series stand-off scale models:
DJ Aerotech
www.djaerotech.com
RFFS-100 micro RC systems, magnetic
actuators, JMP receivers, four-channel
conversion RFFS-100s:
Dynamic Web Enterprises (DWE)
www.smallrc.com
Reduced-size receiver antennas:
E Cubed R/C
www.azarr.com
Magnetic actuators, control-linkage
accessories, connectors:
EFlight Designs
www.eflightdesigns.com
Li-Poly batteries, chargers:
E-Tec (Air Craft)
www.aircraft-world.com
M5 micro DC receivers, submicroservos,
Kokam Li-Poly batteries, chargers:
FMA Direct
www.fmadirect.com
Penta 2.4-gram receivers, GDservo 1.33-gram
servos, new proportional magnetic actuators:
Gasparin
56 MODEL AVIATION
www.gasparin.cz
Motors, propellers, wheels, accessories:
Grand Wing Servo-Tech (GWS)
www.gws.com.tw
Cirrus Micro Joule receivers, ESCs, 3-gram
servos:
Global Hobby Distributors
www.globalhobby.com
Triton Li-Poly chargers:
Great Planes Model Distributors
www.electrifly.com
www.greatplanes.com
HS-50 submicroservo:
Hitec RCD
www.hitecrcd.com
Cirrus Micro Joule receiver, ESC, 3-gram
servos:
Hobby Club
www.hobbyclub.com
Motors, JR radios, Hobby Zone ARF indoor
models, Thunder Power Li-Poly batteries:
Horizon Hobby (GWS)
www.horizonhobby.com
Assortment of tiny direct- and gear-drive
motors:
Kenway Motors
(908) 850-9571
GWS motors, propellers, Li-Poly batteries:
Maxx Products International
www.maxxprod.com
ARF and RTF indoor models:
Megatech
www.megatech.com
Li-Poly batteries, connectors, wire:
Radical RC
www.radicalrc.com
Berg receivers:
RC Direct
www.rc-direct.com
Tiny geared motors, scale model kits:
RCS Technik (Chris Stewart)
www.falconmodels.uk.com
Microreceivers, ESCs, Li-Poly batteries,
chargers, model kits:
Sky Hooks and Rigging
www.microrc.com
Li-Poly batteries:
Thunder Power (Advanced Energy
Technology Inc.)
(702) 228-8883
Indoor model kits and supplies:
Todd Long Models
www.toddsmodels.com
Li-Poly chargers, ARF and RTF model kits:
Tower Hobbies
www.towerhobbies.com
7865 Mill Road, Elkins Park, PA. 19027 USA
Tel. 215 635 6520 Orders ONLY 888 721 0128 Fax. 215 635 4951
Email [email protected] www.sonictronics.com.
NEW
McDaniel R/C A Division of Sonic-Tronics Inc.
Patents, copyrights
and trademarks are
applied.
The New “Go-Slo III” has been
improved with added features.
With the precise performance of
an 8 bit microprocessor the output
is now “user selectable”. Two models are available. One can
drive a single servo, two servos in tandem, two servos with one
reversed or all three servos at once. The other model drives one,
two or three servos in parallel. Both models allow the servo speed to be
adjusted, 2 to 10+ seconds of travel in either direction. Go-Slo III units
are great for precise operation of Flaps, Gear etc. The receiver cable is now a
heavy 22 gage for better power delivery to one, two or three servos.
Go-Slo III‘s are compatible with 4.8 or 6 Volt systems and all proportional servos.
The unit is 1.5” x 1.5”x 3/4” and only .9 oz in weight.
07sig2.QXD 4/26/04 8:34 am Page 56
Edition: Model Aviation - 2004/07
Page Numbers: 42,43,44,45,46,48,50,52,55,56
42 MODEL AVIATION
Introduction to
Indoor Radio Control
I WROTE A feature article published in last
month’s MA titled “Introduction to Parking
Lot Flying.” That category involves flying
relatively small, easy-to-build, and relatively
inexpensive RC models close in.
Aircraft in that size category (up to
roughly 16 ounces total weight) can also,
under certain circumstances, be flown in
indoor facilities. From a practical standpoint,
the larger parking lot-size models can be
flown easily and safely in extra-large indoor
facilities such as golf practice domes
(inflatable) and field houses used for football
practice.
Since winter weather hits many areas
of our country, indoor RC flying during
those months is increasing in popularity.
Not everyone has a golf dome or a field
house in his or her community, but almost
everyone has a school gymnasium or
auditorium that can be an excellent
substitute. To be able to use these smaller
indoor flying facilities, you have to
by Bob Aberle
Author’s original-design Kiwi weighs just 3.4 ounces with 100-
square-inch wing. It uses FMA Direct M5 receiver and two FMA
Direct PS-20 submicroservos. Battery power is two 145 mAh Li-
Poly cells.
Dynamic Web Enterprises proprietors Dan Hurd (L) and his dad
Clarence. Dan holds 1-ounce Pitts Special biplane; Clarence
holds his own-design Lil Skeeter.
Another Joe Wagner FF design from the early
1950s: the Dakota biplane. At right is originalsize
model powered by .049 glow engine. The
author built reduced-size version (left) which
weighs 1.3 ounces with 69 square inches of total
wing area. Power is single 145 mAh Li-Poly
battery. Construction article and plans were
published in May 2003 RC MicroFlight.
Author holds 3.8-ounce version of
popular Joe Wagner FF design—
The Sioux—from the early 1950s.
It has 90-square-inch wing and is
powered by GWS LPS/B2C-C
motor and two FMA Direct/Kokam
340 mAh HD Li-Poly cells. Will
soon be featured as construction
article in Quiet Flyer magazine.
The 2004 NIRAC Indoor Championships will be held
at the big Oakland Yard Athletics facility in Waterford MI.
Fun-flying will be permitted before contest rounds.
All are invited!
07sig2.QXD 4/26/04 8:23 am Page 42
July 2004 43
Pair of typical magnetic actuators. They have a moving magnet within a
coil. Exact separation between two coils and the fact that they are at right
angles to one another provide for control position centering.
Todd Long of Todd’s Models has been selling his Tiny for several years.
Depending on motor and battery choice, this excellent-flying design can
weigh approximately 4 ounces and provide considerable indoor RC funflying.
Don Stackhouse of DJ Aerotech holds two of his Roadkill-series
profile sport-scale models: an Me 109 (L) and a Ryan ST. Each
weighs roughly 3-3.5 ounces and operates on two Li-Poly
batteries.
Closer view of Clarence Hurd’s Lil Skeeter, which was
designed around DWE’s RFFS-100 micro RC system. It
has 46 square inches of wing area and weighs 23 grams
(.81 ounce) including single 130 mAh Li-Poly battery.
Motor is KP-00 geared at 2.67:1.
The Lightning RTF foam model was originally
intended to be an electric-powered FF. An
excellent conversion article by Greg Covey
detailing how to install the DWE RFFS-100 micro
radio system is on the DWE Web site.
DWE RFFS-100 micro RC system is extremely
popular. On this one, PC board weighing 1.8
grams is an RC receiver, ESC, and two magnetic
actuator drivers. It’s one of the best starting
points for flying RC models at or near 1-ounce
total weight.
Photos courtesy the author
07sig2.QXD 4/26/04 8:26 am Page 43
Let’s get into the details of these small, or as we call them, “microsize”
RC aircraft.
Micromodel Sizing: Micro-size models dedicated to indoor RC
flying can range from roughly 8 ounces total weight down to only a
few grams. For this presentation I’m concentrating on 4 ounces total
weight and less.
Right now the range of 4 ounces down to approximately 2.5
ounces can be enjoyed while employing the
available equipment technology, and at
relatively moderate prices. From 2.5 ounces
down to roughly .75 ounce, you will need one
of the several submicroservos on the market
or magnetic actuators. For less than .75 ounce
down to a few grams, you need highly
specialized equipment and considerable
model-building skills.
Typical 4-ounce models can have
approximately 80-120 square inches of wing
area, which will yield wing loadings in the
range of roughly 4-6 ounces/square foot. The
4-ounce total weight could consist of 2.25
ounces of equipment (receiver, two servos,
Li-Poly battery, motor, propeller, and motor
speed controller). The remaining 1.75 ounces
includes the model structure (including
covering, finish, wheels, hinges, and control
linkages).
This typical 4-ounce model can employ
traditional RC equipment, but it will be
smaller in size and weight. The servos will
consider reducing your RC model’s size and weight.
The subject of this presentation is flying RC indoors with models
that weigh less than 3 or 4 ounces. As I noted, there are certain
situations in which you can fly a parking lot model inside. There are
also times in which you can fly a 1-ounce RC model outdoors. To do
that, you need to seek out the dead-calm early-morning or -evening
air. Calm-air outdoor flying also lends itself well to backyard-type
flying, making it a perfect family hobby/sport!
44 MODEL AVIATION
Popular little KP-00 geared motor and companion 3-inch-diameter
propeller. Several sources sell this motor, as noted in text. Power
range is intended for .75- to roughly 1.5-ounce models!
Rear of FMA Direct M5 dual-conversion receiver, which is
smallest dual-conversion RC receiver on the market. It is
available on 72 MHz and six-meter RC channels. Weighs .35
ounce with case!
Basic RC system for 2.5- to 4-ounce model weight (L-R): Castle
Creations Pixie-7P ESC, FMA Direct M5 dual-conversion
microreceiver, two FMA Direct PS-20 submicroservos, two-cell
FMA Direct/Kokam 340 mAh HD Li-Poly battery pack.
Power, RC system needed to fly 1-ounce total-weight model.
Left: KP-00 geared motor, 3-inch-diameter propeller. Top center:
Pair of EFlight Designs magnetic actuators to operate rudder,
elevator. Top right: A 145 mAh Li-Poly battery cell. Just below
that is DWE RFFS-100 PC board containing receiver, ESC, two
magnetic actuator drivers. Lower right: Azarr’s E Cubed RC
reduced-size receiver antenna.
Cutaway of GWS LPS/B2C-C geared motor
mounted to 3⁄16-inch wood dowel. A
setscrew holds motor in place. Two
plywood formers support dowel. It’s
simple and effective! You can easily
change motor at flying site.
Dave Burley has been developing
microservos for indoor RC fliers’ benefit.
His latest (shown) is 1-gram proportional
feedback ultramicroservo. He demonstrated
it to many indoor RC experts at 2003 NEAT
Fair. Dave wants to interest a prominent
manufacturer to pick up on production
rights for it. It worked well, and he hopes it
can be produced at a reasonable unit price.
07sig2.QXD 4/26/04 8:28 am Page 44
July 2004 45
provide regular proportional control, operating from a conventional
RC transmitter.
I have a little indoor sport model that I’m flying at 74 square inches
of wing area and 1.2 ounces total weight. The wing loading works out
to only 2.3 ounces/square foot. It employs two magnetic actuators, and
a 145 mAh Li-Poly battery cell provides all the power. When flown
outdoors, this model doesn’t like any wind! I’ll get into the specifics of
the RC equipment later.
Safety: As is the case with parking lot flying, indoor RC flying has
certain safety issues about which you should be concerned. Even
though you are flying inside, radio signals can travel through buildings
easily without much attenuation of strength. Someone might be flying
right outside your indoor facility, so please check around first. It’s best
to check local hobby shops and RC clubs too.
Also safety related is your model’s speed in flight. An airplane
with less than 100 square inches of wing area and weighing
approximately 10 ounces might be capable of speeds in excess of 60-
75 mph. If it hits something or someone, it could cause physical or
property damage.
Common sense must prevail and reasonable weights and flying
speeds must be commensurate with the size of the facility. A leadertype
person should be in charge of each flying session. That person
must have the last word on who can or can’t fly, and his/her judgment
must be respected at all times!
Micromodel Design: I’ve already suggested weights and wing
loadings, and soon I will get into power systems. There aren’t many
ARF models in the less-than-4-ounce category; that might be
considered the bad news. The good news is that a 4-ounce airplane
can, for the most part, be constructed from scratch, with a minimum of
materials and a minimum of assembly time and skills. I’ve built 1-
ounce RC models from a single sheet of 1⁄32 x 3 x 36-inch balsa. That
is almost as inexpensive as you can go!
The 2- to 4-ounce models can often be built up from the many
rubber-powered kits on the hobby market. Doing this has become
popular. Another possibility are the profile semiscale models, such as
DJ Aerotech’s Roadkill series. Those are easy to build, inexpensive,
and are even supplied with the recommended motor.
If you want to try a 1-ounce model for the first time, the best
trainer is the Lil Skeeter designed by Clarence Hurd of Dynamic Web
Enterprises (DWE). This design was reviewed in the June 2002 RC
MicroFlight newsletter. Plans are available from DWE, and you
receive a free plans copy when you purchase the DWE RFFS-100
micro RC system.
A more ambitious project is Dave Robelen’s Walker, which he
Former AMA executive director and RC MicroFlight founding
editor John Worth holds Pee Wee Flyer made by Estes (the
rocket people). Wal-Mart stores throughout the country sell this
RTF for only $19.95. An article describing it was published in
the October 2003 RC MicroFlight.
Sky Hooks and Rigging owner Tom Mc Cann holds his little
Mosquito indoor slow flyer that Ken Coleman designed. It is
available from Tom as a kit. It spans 24 inches, has 131 square
inches of wing area, weighs 2.25 ounces, and flies on single Li-
Poly battery cell.
Micro-Pod is Bob’s latest original-design indoor RC model. A
construction article was published in November 2003 RC
MicroFlight. It weighs 1.2 ounces and has 74-square-inch wing
area. Power is geared KP-00 motor operating on single 145 mAh
Li-Poly cell.
calls an “ultralite indoor floater.” Dave went to the other extreme and
designed a 1-ounce model with an amazing 357 square inches of wing
area. The resulting wing loading works out to only .4 ounce/square
foot and provides flying speeds of just 3-4 mph. You can walk under
this model while it is flying. The Walker was featured in the July 2003
RC MicroFlight.
07sig2.QXD 4/26/04 8:30 am Page 45
Henry Pasquet is probably the most famous indoor RC flier. His
goal for years has been to build smaller and smaller models. He
holds his 4-inch-span Lacy M-10. It weighs 2.6 grams (total) with a
Gasparin G2.6 CO2 engine. RC system is by Nick Leichty. One No.
337 silver-oxide battery powers the system. It flies very well despite
its size!
US Airways Captain Joe Malinchak’s super-detailed Piper L-4
Grasshopper is military version of Piper Cub. Weighs 1.3 ounces
total including complete scale cockpit interior, landing-gear
shocks, etc. Has geared KP-00 for power! Joe earned DWE award at
2003 NIRAC Championships for RC Scale model with highest
points and weighing less than 1.5 ounces!
NIRAC president, MA columnist, and newly inducted Indoor RC Hall
of Fame member Dave Robelen holds his Scale 34-inch-span Piper
Vagabond. It has 200 square inches of wing area and weighs 4
ounces ready to fly. Power is a DC 5-2.4 coreless motor geared 7.5:1,
running on seven-cell 50 mAh battery pack.
Matt Keennon’s tiny electric-powered Scale P-38 twin spans only
10.5 inches and weighs 35 grams (1.23 ounces) with two M-20
motors and two Kokam 145 mAh Li-Poly cells in parallel. Flight
demos at NEAT Fair were spectacular. Matt makes a living
working on government-sponsored micromodel projects.
Nick Leichty, known for his ultramicro RC models, holds his
Micro Aero Master biplane at 2003 NEAT Fair. It employs one of
his micro three-channel RC systems powered by 4mm motor and
a 40 mAh Li-Poly battery. Model spans 5.5 inches and has 5.5-
gram (.19-ounce) total weight. Approximate flight time on a
charge is five minutes. The author saw the flights and couldn’t
believe it!
46 MODEL AVIATION
07sig2.QXD 4/26/04 8:32 am Page 46
Power Systems: Indoor power systems
primarily involve electric motors, be they
direct drive or gear driven. CO2 power
(compressed gas) is used to some extent, but
the ability to throttle these engines is still in
the experimental stages. Although some of
the tiny glow-fuel and diesel engines might
find their way into indoor RC flying, the
combination of noise and exhaust fumes
makes it somewhat impractical.
Small motors are becoming more and
more popular, and the prices keep going
down. This past year, Grand Wing Servo-
Tech (GWS)—a huge parking lot-/indoormodel
manufacturer—introduced a tiny
geared motor that it calls the “LPS” series.
One of the motors in this category—the
GWS/LPS/B2C—weighs only approximately
12 grams (.42 ounce). It is available in three
gear ratios (4:1, 5:1, 6.2:1).
I’m presently using the 6.2:1 geared
version, which operates on two Li-Poly
battery cells (nominal 7.4 volts) at 700 mA
motor current and 6-watt power level. Using a
GWS 6 x 5 propeller, I generate more than
enough thrust to fly a 4-ounce RC model.
These motors sell for roughly $10. How can
you go wrong?
The .75-1.5-ounce models are generally
powered by pager-derivative motors such as
the Knight & Pridham KP-00 (of which there
are several models with different windings),
with gearing ranging from 2.75:1 upward of
6:1. Each specific gear ratio requires a
different size propeller. Propeller diameters
range from 3 to 6 inches. The gearing choices
attempt to get the most thrust from the motor
while drawing the least current. This is the
game you must play with electric-powered
flight.
The little KP-00 motor will work well on
a single Li-Poly cell drawing roughly 700 mA
of current at approximately a 3-watt power
level. The trick with this is to be able to get an
RC system (receiver and servos) that can also
operate reliably from a single Li-Poly cell at
roughly 3.6 volts.
There are receivers that will do that,
especially those used in conjunction with
magnetic actuators. Bob Selman Designs
offers a new voltage-doubler unit that takes
the single cell voltage and increases it to
roughly 5 volts for more reliable RC
operation.
Many smaller motors are becoming
available for the indoor RC experimenter who
wants to keep reducing that total model
weight to as little as a few grams. Experts
such as Henry Pasquet and Nick Leichty are
regularly flying models weighing roughly .3
ounce! You can find tales of their
experimental efforts in RC MicroFlight. But
as I pointed out before, these truly micro RC
models require a great deal of experience and,
most of all, patience!
As this is being written, I have heard
about several micro manufacturers who have
prototype miniature brushless motors and
companion speed controllers in the works. A
lightweight, highly efficient brushless motor
will provide yet another breakthrough in
indoor RC.
Before leaving the power scene, I’ll
mention that there are CO2 motors now
available for RC model use. They are still
comparatively expensive, but a model’s
weight can be reduced even further than with
electric power because the CO2 tank weighs
less than a battery.
The biggest problem until recently has
been the ability to throttle these air-operated
motors. Stefan Gasparin in the Czech
Republic has made remarkable progress in
this regard. I urge you to look at his Web site.
ESCs: Even the electric motor speed
controllers have been shrunken to fit the
needs of our micro-size aircraft. I think it’s
safe to state that all of the micro ESCs have a
BEC, which allows for the sharing of the one
battery pack.
As you will soon learn, the new Li-Poly
battery technology requires that no cell drop
to less than 3.0 volts when in use. This is a
minimum discharge point. To be on the safe
side, a micro ESC’s low voltage cutoff point
should be set to increments of 3.0 volts per
cell. If you are using one Li-Poly cell, the
cutoff should be 3.0 volts. If your pack has
two Li-Poly cells the cutoff should be 6.0
volts, and so on.
Castle Creations’ Pixie-7P ESC allows
you to program the voltage cutoff point.
There aren’t that many choices, but they will
improve in time. Setting the voltage cutoff on
07sig2.QXD 4/26/04 8:33 am Page 48
the Pixie isn’t all that easy and does require
some patience, but this is the concept you
want to look for in the future!
Batteries: Until recently, the batteries of
choice for 4-ounce and lighter models were
the 100-125 mAh NiMH types, usually in
packs consisting of seven or eight cells. In the
past year we have been introduced to a new
form of battery known as the Li-Poly. These
new cells provide more capacity in a lighterweight
package. Both of those parameters are
exactly what you want for micro RC models.
Of equal interest is the fact that each Li-
Poly cell has a characteristic voltage of close
to 4.0; the older Ni-Cd/NiMH cells had only
1.2 volts per cell. So two Li-Poly cells work
like a six- or seven-cell Ni-Cd/NiMH pack.
We typically see two-cell packs consisting
of 145 mAh or 340 mAh powering 3- to 4-
ounce RC models. A two-cell 145 mAh Li-
Poly pack weighs 8.7 grams (.31 ounce) and
can fly that 3- to 4-ounce model at 700 mA
current (6 watts) for 10-12 minutes and more,
depending on how you throttle the motor in
flight. And two of the 340 mAh Li-Poly cells
(weighing 20.1 grams, or .71 ounce) could
provide up to 30 minutes of motor run time.
However, Li-Poly cells are still quite new
on the market, and they must be taken care of
very carefully. They require a special
dedicated charger and should not be charged
with more than a 1C current, which takes
roughly an hour. Li-Poly batteries should not
be discharged to less than 3.0 volts per cell.
Li-Poly cells are also currently somewhat
limited in their load capabilities. Initial
offerings could only provide loads up to
approximately 5C (five times the capacity of
the battery). Recently a new variety of Li-
Poly cell has been introduced that can stand
loads upward of 20C (quite an
improvement!).
Li-Poly batteries is a subject unto itself. I
wrote a comprehensive article titled
“Introduction to Lithium-Polymer Batteries”
that was published in the May 2004 MA. If
you haven’t read that piece, I highly
recommend that you do so before attempting
to use Li-Poly batteries in a model airplane of
any kind.
Micro RC System and Components: The RC
equipment is conventional technology, but is
obviously made smaller and lighter. An
inexpensive microreceiver is the GWS R-4P,
which has four-channel capability, is a singleconversion
circuit, and weighs 6.8 grams (.25
ounce). At approximately $30, it is a great
buy.
For those who want good range and
selectivity, in a crowded flying environment,
the FMA Direct M5 dual-conversion receiver
is an excellent choice, especially in the 2.5- to
4-ounce-model weight class. The M5 weighs
9.5 grams (.35 ounce).
Another outstanding choice is the Berg-
5*DSP at .35 ounce and the new Berg-4*DSP
Micro Stamp at just .25 ounce. The Berg
receivers are available from RC Direct. With
the Berg and FMA Direct receivers, you can
remove the receiver case for a further weight
reduction.
For the extra-small models (1.5 ounces
and lighter), the DWE RFFS-100 has been the
popular microsystem for some time. It is a
microreceiver, a built-in ESC with BEC, and
drivers for two magnetic actuators on a single
PC board. The entire board weighs only 1.8
grams (.06 ounce!).
The RFFS-100 receiver is not very
selective, so you can’t use several channels on
either side of your operating frequency when
flying. But this system has provided a load of
indoor RC fun-flying under the right
conditions.
Jean-Marie Piednoir (JMP) of France
makes a new and more selective
microreceiver which Bob Selman Designs
sells in the US. This receiver is claimed to be
extremely narrow band (selective!) and
includes an ESC and two magnetic actuator
drivers. It weighs 2.2 grams (.08 ounce), and
the price without connectors is $89. I’m sure
we will be seeing plenty of these units put
into indoor RC service in the near future.
As I was writing this, I learned of the new
Gasparin Penta 2.4-gram (.8-ounce) fourchannel
receiver, which is claimed to be
incredibly selective and will be selling in the
US at a reasonable $39.
In addition to receivers, servos or actuators
are also important. Conventional servos,
meaning regular proportional feedback
servos, are available at roughly 5.6 grams (.20
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07sig2.QXD 4/26/04 8:33 am Page 50
ounce). Two come to mind: the popular Hitec
HS-50 and the new FMA Direct PS-20. Each
sells for less than $30 and has been reliable.
The German WES-Technik company has
been making a linear-output-type microservo
for the past couple years. It weighs 2.1 grams
(.07 ounce) but is comparatively expensive at
$70-$80 (US).
Stefan Gasparin in conjunction with Didel
(the Swiss gear company) has designed a new
GDservo, which has a rotary output and
weighs 1.33 grams without a case. It will be
pricey, at $98 (US). Stefan also has a new
concept he calls a “Proportional Magnetic
Actuator.” I’ve seen some photos, and the
idea looks entirely realistic. Price is said to be
$39 each (US).
At the bottom of the weight scale are the
truly magnetic actuators; these are coil
devices with magnets that move inside the
coils. They require some patience to install
and offer little control force. That means your
hinges and control linkages must offer the
least possible friction. These magnetic
actuators make RC models of less than 1
ounce total weight possible. Good sources of
magnetic actuators include Bob Selman
Designs, Cloud-9 RC, E-Flight Design, and
DWE.
One last reference is to a “brick” design,
which was popular in the early 1970s. FMA
Direct is almost ready to release a microbrick
that will include one PC board, a narrow-band
receiver, ESC, control actuator drivers, and
two servos or two magnetic actuators. Placing
all of the components on a single board can
make certain installations impractical, but the
bottom line is that the brick eliminates a great
deal of wiring and connectors, thereby
reducing the overall weight. I believe this
concept will find a home in the 2.5- to 4-
ounce model category.
Connectors: The connectors and the wire size
(gauge, which refers to diameter) are
important. You want to carry the current
involved and no more; using a connector that
is too large or a wire with too large a diameter
only adds weight to little airplanes that can’t
afford it.
The larger parking lot-size models can
properly use the popular Anderson Power
Pole-type connectors (also known as Sermos
connectors). You can use these from roughly
6 amps of current up.
The Deans four-pin connectors are popular
for 3 to 6 amps of current. It is a good idea to
gang two pins to make a single connection. In
that case, the four pins yields two conductors.
From 1.5- to 3-amp current, the JST red
plastic housing connector is fine. For less than
1.5 amps of current, the JST white plastic or
Cloud 9 RC Unisex connectors will do the
job.
EFlight Designs carries an excellent line of
submicroconnectors. Wire size can start with
16 gauge for the 8- to 10-amp current. As you
work your way down in current, the wire
gauge can go from 22 to 28, and even 32.
Your hobby supplier can recommend the best
size for each current level. The JST
connectors come with the wire already
attached.
Indoor Flying Tips: If you are already an RC
sport flier or a parking lot flier, you are
certainly qualified to fly indoors; but the
generally “restricted” airspace can be
extremely challenging at times. If you are
lucky enough to be able to fly a 4-ounce
model in an inflated dome, it is almost the
same as flying outdoors—no problem!
However, when you get down to a doubleor
even single-size gymnasium, you get the
feeling that you are always turning the
airplane; there isn’t enough space for
appreciable straightaway flight.
Inside a dome my aircraft have
occasionally hit walls or even the top dead
center of the ceiling. Being such lightweight
models, they seem to just bounce off these
soft surfaces. Most of the time I lose altitude
but can easily recover the airplane to normal
flight.
On the other hand, at the Toledo, Ohio,
PERF (Perrysburg Electric River Fliers)
indoor fly a couple years ago (when it was a
smaller facility), I “shot a basket” with my
little 4.7-ounce AIKA. We had to get a large
stepladder to remove the model from the
basketball hoop/net.
However, before you start worrying about
these possibilities, consider that at such light
weights and wing loadings, not much ever
happens to micromodels—except for midair
52 MODEL AVIATION
Since 1948 Fox Manufacturing
Company has been producing
high quality model airplane
engines, glow plugs and other
accessories. Fox has become a
name modelers can trust when
it comes to durability, power,
and performance at an
affordable price. (479) 646-1656
Fax (479) 646-1757
5305 Towson Avenue
Fort Smith, AR 72901
www.foxmanufacturing.com
email: [email protected]
07sig2.QXD 4/26/04 8:34 am Page 52
July 2004 55
collisions! They do occur every once in
awhile, but if you build your entire model
from a single sheet of balsa, it’s no big deal!
NIRAC: AMA encourages SIGs to help
organize the various groups within model
aviation. We are lucky to have the National
Indoor Remote-Control Aircraft Council
(NIRAC) represent indoor RC flying within
the Academy. National Indoor Electric
Duration record-holder Bob Wilder of Texas
founded the organization several years ago.
You can access the Web site containing all
of the general information about this SIG at
www.nirac.org. Look it up, get familiar with
the organization, and show your support by
joining.
Once a year NIRAC sponsors a major
indoor RC championship. The 2004 dates are
June 4-6, and the location, as in the past, will
be the big Oakland Yard Athletics facility (an
inflated dome) in Waterford, Michigan
(www.oaklandyard.com/model_aviation.htm).
The flying plan for the three days includes
official indoor RC events including Scale,
racing, cargo lift, Old-Timer climb-and-glide,
endurance, and RC gliders. Between the
events the dome will be opened up for funflying
by all who attend.
NIRAC can also help you find local domes
and large indoor flying facilities. The current
NIRAC president—Dave Robelen—is one of
the most experienced indoor/micro RC fliers.
With indoor RC growing extraordinarily
rapidly, there is much to be learned; new
technology seems to emerge almost weekly.
The big, annual NEAT (Northeast Electric
Aircraft Technology) Fair held in upstate New
York, near the town of Downsville, includes a
series of indoor RC lectures during the three
days of the event.
Sergio Sigras coordinates these seminars.
Some of the most important names in
microflight—Henry Pasquet, Gordon
Johnson, Matt Keennon, Nick Leichty, Fred
Marks, Clarence Hurd, Bob Selman, and
more—provide the latest indoor RC
information.
For the Saturday night of the Fair, Gordon
Johnson sets up an indoor RC flight
demonstration in a double-size gym at nearby
Walton Senior High School. Guest lecturers
get to show their stuff, to the delight of
hundreds of spectators. To learn more about
the Fair, visit www.neatfair.org.
When you are attempting to gain
permission to fly indoor RC at local school
facilities, offer to lecture and/or give classes at
the school to offset your using the venue.
“Yes, you can use our gym, but why not come
in and let our young people learn how they
can participate?”
References: NIRAC is a good starting point.
Several publications regularly offer many
articles about indoor RC. Air Age Media’s RC
MicroFlight is available in hard-copy form
and online. It has been in production for more
than three years. When you subscribe, you
obtain a password that allows you access to all
previously published articles. You can even
download plans from the construction articles.
MA has two talented authors who write
alternating bimonthly columns. Dave Robelen
writes “Micro-Flying” (featuring indoor RC
and parking lot flying) and Paul Bradley
writes “Small-Field Flying” (covering parking
lot flying and backyard flying, and hitting on
indoor RC). I highly recommend these.
You can count on Quiet Flyer, under the
direction of publisher Wil Byers, for many
indoor RC-oriented articles each month. This
magazine specializes in electric power and
sailplane activities.
Flying Models magazine also has
alternating columnists who spend considerable
time in the world of indoor RC: Don Belfort
and Stew Meyers. For many years, RC
Modeler magazine has featured Jim Zare, who
now concentrates most of his activities on
micro and indoor flying.
I hate to sound too commercial, but
roughly two years ago I wrote the book
Getting Started in Backyard Flying. It
contains a lot of material about indoor RC.
You will see how parking lot/backyard flyers
tend to complement the indoor RC flyer. This
book is available from AMA, Tower Hobbies,
Balsa Products, and the publisher’s Web site:
www.rcstore.com/rs/general/books.asp.
In the late 1960s, people such as Dave
Robelen, John Worth, and Howard McEntee
experimented with multichannel proportional
RC control of glow-fueled models that
07sig2.QXD 4/26/04 8:34 am Page 55
weighed only 5-8 ounces! Those airplanes and
their equipment were tedious to work with,
but they did fly.
Soon afterward, AMA Hall of Famer Bill
Cannon of Cannon Electronics produced a
subminiature RC system that made smallscale
RC-model flying practical for everyone.
Bill continued to make that equipment for
many years and should be congratulated for
his efforts and dedication to small-model RC
flying.
Recently we have been privileged to see
the development of micro RC systems, servos,
actuators, Li-Poly batteries, tiny motors, and a
growing group of dedicated RC modelers who
have been willing to make this endeavor
grow. With modern large inflatable domes,
field houses, etc., it is now possible to enjoy
RC flying during all kinds of weather, at any
time of day or night.
Want to have some more fun in RC? Try
flying indoors. MA
Bob Aberle
[email protected]
Manufacturers/distributors:
Firefly coreless micro motors—direct and
geared:
AstroFlight Inc.
www.astroflight.com
GWS motors, propellers, Li-Poly batteries:
Balsa Products
www.balsapr.com
Li-Poly batteries:
Batteries America
www.batteriesamerica.com
JMP receivers, magnetic actuators, Li-Poly
chargers:
Bob Selman Designs
http://users.joplin.com/~bselman/
Voltage cutoff programmable ESCs:
Castle Creations
www.castlecreations.com
Assortment of micro hardware and products:
Cloud 9 RC (John Worth)
(703) 273-0607
Hard-to-get gears, motors, propellers, wire,
connectors:
David Lewis
www.homefly.com
Profile Roadkill series stand-off scale models:
DJ Aerotech
www.djaerotech.com
RFFS-100 micro RC systems, magnetic
actuators, JMP receivers, four-channel
conversion RFFS-100s:
Dynamic Web Enterprises (DWE)
www.smallrc.com
Reduced-size receiver antennas:
E Cubed R/C
www.azarr.com
Magnetic actuators, control-linkage
accessories, connectors:
EFlight Designs
www.eflightdesigns.com
Li-Poly batteries, chargers:
E-Tec (Air Craft)
www.aircraft-world.com
M5 micro DC receivers, submicroservos,
Kokam Li-Poly batteries, chargers:
FMA Direct
www.fmadirect.com
Penta 2.4-gram receivers, GDservo 1.33-gram
servos, new proportional magnetic actuators:
Gasparin
56 MODEL AVIATION
www.gasparin.cz
Motors, propellers, wheels, accessories:
Grand Wing Servo-Tech (GWS)
www.gws.com.tw
Cirrus Micro Joule receivers, ESCs, 3-gram
servos:
Global Hobby Distributors
www.globalhobby.com
Triton Li-Poly chargers:
Great Planes Model Distributors
www.electrifly.com
www.greatplanes.com
HS-50 submicroservo:
Hitec RCD
www.hitecrcd.com
Cirrus Micro Joule receiver, ESC, 3-gram
servos:
Hobby Club
www.hobbyclub.com
Motors, JR radios, Hobby Zone ARF indoor
models, Thunder Power Li-Poly batteries:
Horizon Hobby (GWS)
www.horizonhobby.com
Assortment of tiny direct- and gear-drive
motors:
Kenway Motors
(908) 850-9571
GWS motors, propellers, Li-Poly batteries:
Maxx Products International
www.maxxprod.com
ARF and RTF indoor models:
Megatech
www.megatech.com
Li-Poly batteries, connectors, wire:
Radical RC
www.radicalrc.com
Berg receivers:
RC Direct
www.rc-direct.com
Tiny geared motors, scale model kits:
RCS Technik (Chris Stewart)
www.falconmodels.uk.com
Microreceivers, ESCs, Li-Poly batteries,
chargers, model kits:
Sky Hooks and Rigging
www.microrc.com
Li-Poly batteries:
Thunder Power (Advanced Energy
Technology Inc.)
(702) 228-8883
Indoor model kits and supplies:
Todd Long Models
www.toddsmodels.com
Li-Poly chargers, ARF and RTF model kits:
Tower Hobbies
www.towerhobbies.com
7865 Mill Road, Elkins Park, PA. 19027 USA
Tel. 215 635 6520 Orders ONLY 888 721 0128 Fax. 215 635 4951
Email [email protected] www.sonictronics.com.
NEW
McDaniel R/C A Division of Sonic-Tronics Inc.
Patents, copyrights
and trademarks are
applied.
The New “Go-Slo III” has been
improved with added features.
With the precise performance of
an 8 bit microprocessor the output
is now “user selectable”. Two models are available. One can
drive a single servo, two servos in tandem, two servos with one
reversed or all three servos at once. The other model drives one,
two or three servos in parallel. Both models allow the servo speed to be
adjusted, 2 to 10+ seconds of travel in either direction. Go-Slo III units
are great for precise operation of Flaps, Gear etc. The receiver cable is now a
heavy 22 gage for better power delivery to one, two or three servos.
Go-Slo III‘s are compatible with 4.8 or 6 Volt systems and all proportional servos.
The unit is 1.5” x 1.5”x 3/4” and only .9 oz in weight.
07sig2.QXD 4/26/04 8:34 am Page 56
Edition: Model Aviation - 2004/07
Page Numbers: 42,43,44,45,46,48,50,52,55,56
42 MODEL AVIATION
Introduction to
Indoor Radio Control
I WROTE A feature article published in last
month’s MA titled “Introduction to Parking
Lot Flying.” That category involves flying
relatively small, easy-to-build, and relatively
inexpensive RC models close in.
Aircraft in that size category (up to
roughly 16 ounces total weight) can also,
under certain circumstances, be flown in
indoor facilities. From a practical standpoint,
the larger parking lot-size models can be
flown easily and safely in extra-large indoor
facilities such as golf practice domes
(inflatable) and field houses used for football
practice.
Since winter weather hits many areas
of our country, indoor RC flying during
those months is increasing in popularity.
Not everyone has a golf dome or a field
house in his or her community, but almost
everyone has a school gymnasium or
auditorium that can be an excellent
substitute. To be able to use these smaller
indoor flying facilities, you have to
by Bob Aberle
Author’s original-design Kiwi weighs just 3.4 ounces with 100-
square-inch wing. It uses FMA Direct M5 receiver and two FMA
Direct PS-20 submicroservos. Battery power is two 145 mAh Li-
Poly cells.
Dynamic Web Enterprises proprietors Dan Hurd (L) and his dad
Clarence. Dan holds 1-ounce Pitts Special biplane; Clarence
holds his own-design Lil Skeeter.
Another Joe Wagner FF design from the early
1950s: the Dakota biplane. At right is originalsize
model powered by .049 glow engine. The
author built reduced-size version (left) which
weighs 1.3 ounces with 69 square inches of total
wing area. Power is single 145 mAh Li-Poly
battery. Construction article and plans were
published in May 2003 RC MicroFlight.
Author holds 3.8-ounce version of
popular Joe Wagner FF design—
The Sioux—from the early 1950s.
It has 90-square-inch wing and is
powered by GWS LPS/B2C-C
motor and two FMA Direct/Kokam
340 mAh HD Li-Poly cells. Will
soon be featured as construction
article in Quiet Flyer magazine.
The 2004 NIRAC Indoor Championships will be held
at the big Oakland Yard Athletics facility in Waterford MI.
Fun-flying will be permitted before contest rounds.
All are invited!
07sig2.QXD 4/26/04 8:23 am Page 42
July 2004 43
Pair of typical magnetic actuators. They have a moving magnet within a
coil. Exact separation between two coils and the fact that they are at right
angles to one another provide for control position centering.
Todd Long of Todd’s Models has been selling his Tiny for several years.
Depending on motor and battery choice, this excellent-flying design can
weigh approximately 4 ounces and provide considerable indoor RC funflying.
Don Stackhouse of DJ Aerotech holds two of his Roadkill-series
profile sport-scale models: an Me 109 (L) and a Ryan ST. Each
weighs roughly 3-3.5 ounces and operates on two Li-Poly
batteries.
Closer view of Clarence Hurd’s Lil Skeeter, which was
designed around DWE’s RFFS-100 micro RC system. It
has 46 square inches of wing area and weighs 23 grams
(.81 ounce) including single 130 mAh Li-Poly battery.
Motor is KP-00 geared at 2.67:1.
The Lightning RTF foam model was originally
intended to be an electric-powered FF. An
excellent conversion article by Greg Covey
detailing how to install the DWE RFFS-100 micro
radio system is on the DWE Web site.
DWE RFFS-100 micro RC system is extremely
popular. On this one, PC board weighing 1.8
grams is an RC receiver, ESC, and two magnetic
actuator drivers. It’s one of the best starting
points for flying RC models at or near 1-ounce
total weight.
Photos courtesy the author
07sig2.QXD 4/26/04 8:26 am Page 43
Let’s get into the details of these small, or as we call them, “microsize”
RC aircraft.
Micromodel Sizing: Micro-size models dedicated to indoor RC
flying can range from roughly 8 ounces total weight down to only a
few grams. For this presentation I’m concentrating on 4 ounces total
weight and less.
Right now the range of 4 ounces down to approximately 2.5
ounces can be enjoyed while employing the
available equipment technology, and at
relatively moderate prices. From 2.5 ounces
down to roughly .75 ounce, you will need one
of the several submicroservos on the market
or magnetic actuators. For less than .75 ounce
down to a few grams, you need highly
specialized equipment and considerable
model-building skills.
Typical 4-ounce models can have
approximately 80-120 square inches of wing
area, which will yield wing loadings in the
range of roughly 4-6 ounces/square foot. The
4-ounce total weight could consist of 2.25
ounces of equipment (receiver, two servos,
Li-Poly battery, motor, propeller, and motor
speed controller). The remaining 1.75 ounces
includes the model structure (including
covering, finish, wheels, hinges, and control
linkages).
This typical 4-ounce model can employ
traditional RC equipment, but it will be
smaller in size and weight. The servos will
consider reducing your RC model’s size and weight.
The subject of this presentation is flying RC indoors with models
that weigh less than 3 or 4 ounces. As I noted, there are certain
situations in which you can fly a parking lot model inside. There are
also times in which you can fly a 1-ounce RC model outdoors. To do
that, you need to seek out the dead-calm early-morning or -evening
air. Calm-air outdoor flying also lends itself well to backyard-type
flying, making it a perfect family hobby/sport!
44 MODEL AVIATION
Popular little KP-00 geared motor and companion 3-inch-diameter
propeller. Several sources sell this motor, as noted in text. Power
range is intended for .75- to roughly 1.5-ounce models!
Rear of FMA Direct M5 dual-conversion receiver, which is
smallest dual-conversion RC receiver on the market. It is
available on 72 MHz and six-meter RC channels. Weighs .35
ounce with case!
Basic RC system for 2.5- to 4-ounce model weight (L-R): Castle
Creations Pixie-7P ESC, FMA Direct M5 dual-conversion
microreceiver, two FMA Direct PS-20 submicroservos, two-cell
FMA Direct/Kokam 340 mAh HD Li-Poly battery pack.
Power, RC system needed to fly 1-ounce total-weight model.
Left: KP-00 geared motor, 3-inch-diameter propeller. Top center:
Pair of EFlight Designs magnetic actuators to operate rudder,
elevator. Top right: A 145 mAh Li-Poly battery cell. Just below
that is DWE RFFS-100 PC board containing receiver, ESC, two
magnetic actuator drivers. Lower right: Azarr’s E Cubed RC
reduced-size receiver antenna.
Cutaway of GWS LPS/B2C-C geared motor
mounted to 3⁄16-inch wood dowel. A
setscrew holds motor in place. Two
plywood formers support dowel. It’s
simple and effective! You can easily
change motor at flying site.
Dave Burley has been developing
microservos for indoor RC fliers’ benefit.
His latest (shown) is 1-gram proportional
feedback ultramicroservo. He demonstrated
it to many indoor RC experts at 2003 NEAT
Fair. Dave wants to interest a prominent
manufacturer to pick up on production
rights for it. It worked well, and he hopes it
can be produced at a reasonable unit price.
07sig2.QXD 4/26/04 8:28 am Page 44
July 2004 45
provide regular proportional control, operating from a conventional
RC transmitter.
I have a little indoor sport model that I’m flying at 74 square inches
of wing area and 1.2 ounces total weight. The wing loading works out
to only 2.3 ounces/square foot. It employs two magnetic actuators, and
a 145 mAh Li-Poly battery cell provides all the power. When flown
outdoors, this model doesn’t like any wind! I’ll get into the specifics of
the RC equipment later.
Safety: As is the case with parking lot flying, indoor RC flying has
certain safety issues about which you should be concerned. Even
though you are flying inside, radio signals can travel through buildings
easily without much attenuation of strength. Someone might be flying
right outside your indoor facility, so please check around first. It’s best
to check local hobby shops and RC clubs too.
Also safety related is your model’s speed in flight. An airplane
with less than 100 square inches of wing area and weighing
approximately 10 ounces might be capable of speeds in excess of 60-
75 mph. If it hits something or someone, it could cause physical or
property damage.
Common sense must prevail and reasonable weights and flying
speeds must be commensurate with the size of the facility. A leadertype
person should be in charge of each flying session. That person
must have the last word on who can or can’t fly, and his/her judgment
must be respected at all times!
Micromodel Design: I’ve already suggested weights and wing
loadings, and soon I will get into power systems. There aren’t many
ARF models in the less-than-4-ounce category; that might be
considered the bad news. The good news is that a 4-ounce airplane
can, for the most part, be constructed from scratch, with a minimum of
materials and a minimum of assembly time and skills. I’ve built 1-
ounce RC models from a single sheet of 1⁄32 x 3 x 36-inch balsa. That
is almost as inexpensive as you can go!
The 2- to 4-ounce models can often be built up from the many
rubber-powered kits on the hobby market. Doing this has become
popular. Another possibility are the profile semiscale models, such as
DJ Aerotech’s Roadkill series. Those are easy to build, inexpensive,
and are even supplied with the recommended motor.
If you want to try a 1-ounce model for the first time, the best
trainer is the Lil Skeeter designed by Clarence Hurd of Dynamic Web
Enterprises (DWE). This design was reviewed in the June 2002 RC
MicroFlight newsletter. Plans are available from DWE, and you
receive a free plans copy when you purchase the DWE RFFS-100
micro RC system.
A more ambitious project is Dave Robelen’s Walker, which he
Former AMA executive director and RC MicroFlight founding
editor John Worth holds Pee Wee Flyer made by Estes (the
rocket people). Wal-Mart stores throughout the country sell this
RTF for only $19.95. An article describing it was published in
the October 2003 RC MicroFlight.
Sky Hooks and Rigging owner Tom Mc Cann holds his little
Mosquito indoor slow flyer that Ken Coleman designed. It is
available from Tom as a kit. It spans 24 inches, has 131 square
inches of wing area, weighs 2.25 ounces, and flies on single Li-
Poly battery cell.
Micro-Pod is Bob’s latest original-design indoor RC model. A
construction article was published in November 2003 RC
MicroFlight. It weighs 1.2 ounces and has 74-square-inch wing
area. Power is geared KP-00 motor operating on single 145 mAh
Li-Poly cell.
calls an “ultralite indoor floater.” Dave went to the other extreme and
designed a 1-ounce model with an amazing 357 square inches of wing
area. The resulting wing loading works out to only .4 ounce/square
foot and provides flying speeds of just 3-4 mph. You can walk under
this model while it is flying. The Walker was featured in the July 2003
RC MicroFlight.
07sig2.QXD 4/26/04 8:30 am Page 45
Henry Pasquet is probably the most famous indoor RC flier. His
goal for years has been to build smaller and smaller models. He
holds his 4-inch-span Lacy M-10. It weighs 2.6 grams (total) with a
Gasparin G2.6 CO2 engine. RC system is by Nick Leichty. One No.
337 silver-oxide battery powers the system. It flies very well despite
its size!
US Airways Captain Joe Malinchak’s super-detailed Piper L-4
Grasshopper is military version of Piper Cub. Weighs 1.3 ounces
total including complete scale cockpit interior, landing-gear
shocks, etc. Has geared KP-00 for power! Joe earned DWE award at
2003 NIRAC Championships for RC Scale model with highest
points and weighing less than 1.5 ounces!
NIRAC president, MA columnist, and newly inducted Indoor RC Hall
of Fame member Dave Robelen holds his Scale 34-inch-span Piper
Vagabond. It has 200 square inches of wing area and weighs 4
ounces ready to fly. Power is a DC 5-2.4 coreless motor geared 7.5:1,
running on seven-cell 50 mAh battery pack.
Matt Keennon’s tiny electric-powered Scale P-38 twin spans only
10.5 inches and weighs 35 grams (1.23 ounces) with two M-20
motors and two Kokam 145 mAh Li-Poly cells in parallel. Flight
demos at NEAT Fair were spectacular. Matt makes a living
working on government-sponsored micromodel projects.
Nick Leichty, known for his ultramicro RC models, holds his
Micro Aero Master biplane at 2003 NEAT Fair. It employs one of
his micro three-channel RC systems powered by 4mm motor and
a 40 mAh Li-Poly battery. Model spans 5.5 inches and has 5.5-
gram (.19-ounce) total weight. Approximate flight time on a
charge is five minutes. The author saw the flights and couldn’t
believe it!
46 MODEL AVIATION
07sig2.QXD 4/26/04 8:32 am Page 46
Power Systems: Indoor power systems
primarily involve electric motors, be they
direct drive or gear driven. CO2 power
(compressed gas) is used to some extent, but
the ability to throttle these engines is still in
the experimental stages. Although some of
the tiny glow-fuel and diesel engines might
find their way into indoor RC flying, the
combination of noise and exhaust fumes
makes it somewhat impractical.
Small motors are becoming more and
more popular, and the prices keep going
down. This past year, Grand Wing Servo-
Tech (GWS)—a huge parking lot-/indoormodel
manufacturer—introduced a tiny
geared motor that it calls the “LPS” series.
One of the motors in this category—the
GWS/LPS/B2C—weighs only approximately
12 grams (.42 ounce). It is available in three
gear ratios (4:1, 5:1, 6.2:1).
I’m presently using the 6.2:1 geared
version, which operates on two Li-Poly
battery cells (nominal 7.4 volts) at 700 mA
motor current and 6-watt power level. Using a
GWS 6 x 5 propeller, I generate more than
enough thrust to fly a 4-ounce RC model.
These motors sell for roughly $10. How can
you go wrong?
The .75-1.5-ounce models are generally
powered by pager-derivative motors such as
the Knight & Pridham KP-00 (of which there
are several models with different windings),
with gearing ranging from 2.75:1 upward of
6:1. Each specific gear ratio requires a
different size propeller. Propeller diameters
range from 3 to 6 inches. The gearing choices
attempt to get the most thrust from the motor
while drawing the least current. This is the
game you must play with electric-powered
flight.
The little KP-00 motor will work well on
a single Li-Poly cell drawing roughly 700 mA
of current at approximately a 3-watt power
level. The trick with this is to be able to get an
RC system (receiver and servos) that can also
operate reliably from a single Li-Poly cell at
roughly 3.6 volts.
There are receivers that will do that,
especially those used in conjunction with
magnetic actuators. Bob Selman Designs
offers a new voltage-doubler unit that takes
the single cell voltage and increases it to
roughly 5 volts for more reliable RC
operation.
Many smaller motors are becoming
available for the indoor RC experimenter who
wants to keep reducing that total model
weight to as little as a few grams. Experts
such as Henry Pasquet and Nick Leichty are
regularly flying models weighing roughly .3
ounce! You can find tales of their
experimental efforts in RC MicroFlight. But
as I pointed out before, these truly micro RC
models require a great deal of experience and,
most of all, patience!
As this is being written, I have heard
about several micro manufacturers who have
prototype miniature brushless motors and
companion speed controllers in the works. A
lightweight, highly efficient brushless motor
will provide yet another breakthrough in
indoor RC.
Before leaving the power scene, I’ll
mention that there are CO2 motors now
available for RC model use. They are still
comparatively expensive, but a model’s
weight can be reduced even further than with
electric power because the CO2 tank weighs
less than a battery.
The biggest problem until recently has
been the ability to throttle these air-operated
motors. Stefan Gasparin in the Czech
Republic has made remarkable progress in
this regard. I urge you to look at his Web site.
ESCs: Even the electric motor speed
controllers have been shrunken to fit the
needs of our micro-size aircraft. I think it’s
safe to state that all of the micro ESCs have a
BEC, which allows for the sharing of the one
battery pack.
As you will soon learn, the new Li-Poly
battery technology requires that no cell drop
to less than 3.0 volts when in use. This is a
minimum discharge point. To be on the safe
side, a micro ESC’s low voltage cutoff point
should be set to increments of 3.0 volts per
cell. If you are using one Li-Poly cell, the
cutoff should be 3.0 volts. If your pack has
two Li-Poly cells the cutoff should be 6.0
volts, and so on.
Castle Creations’ Pixie-7P ESC allows
you to program the voltage cutoff point.
There aren’t that many choices, but they will
improve in time. Setting the voltage cutoff on
07sig2.QXD 4/26/04 8:33 am Page 48
the Pixie isn’t all that easy and does require
some patience, but this is the concept you
want to look for in the future!
Batteries: Until recently, the batteries of
choice for 4-ounce and lighter models were
the 100-125 mAh NiMH types, usually in
packs consisting of seven or eight cells. In the
past year we have been introduced to a new
form of battery known as the Li-Poly. These
new cells provide more capacity in a lighterweight
package. Both of those parameters are
exactly what you want for micro RC models.
Of equal interest is the fact that each Li-
Poly cell has a characteristic voltage of close
to 4.0; the older Ni-Cd/NiMH cells had only
1.2 volts per cell. So two Li-Poly cells work
like a six- or seven-cell Ni-Cd/NiMH pack.
We typically see two-cell packs consisting
of 145 mAh or 340 mAh powering 3- to 4-
ounce RC models. A two-cell 145 mAh Li-
Poly pack weighs 8.7 grams (.31 ounce) and
can fly that 3- to 4-ounce model at 700 mA
current (6 watts) for 10-12 minutes and more,
depending on how you throttle the motor in
flight. And two of the 340 mAh Li-Poly cells
(weighing 20.1 grams, or .71 ounce) could
provide up to 30 minutes of motor run time.
However, Li-Poly cells are still quite new
on the market, and they must be taken care of
very carefully. They require a special
dedicated charger and should not be charged
with more than a 1C current, which takes
roughly an hour. Li-Poly batteries should not
be discharged to less than 3.0 volts per cell.
Li-Poly cells are also currently somewhat
limited in their load capabilities. Initial
offerings could only provide loads up to
approximately 5C (five times the capacity of
the battery). Recently a new variety of Li-
Poly cell has been introduced that can stand
loads upward of 20C (quite an
improvement!).
Li-Poly batteries is a subject unto itself. I
wrote a comprehensive article titled
“Introduction to Lithium-Polymer Batteries”
that was published in the May 2004 MA. If
you haven’t read that piece, I highly
recommend that you do so before attempting
to use Li-Poly batteries in a model airplane of
any kind.
Micro RC System and Components: The RC
equipment is conventional technology, but is
obviously made smaller and lighter. An
inexpensive microreceiver is the GWS R-4P,
which has four-channel capability, is a singleconversion
circuit, and weighs 6.8 grams (.25
ounce). At approximately $30, it is a great
buy.
For those who want good range and
selectivity, in a crowded flying environment,
the FMA Direct M5 dual-conversion receiver
is an excellent choice, especially in the 2.5- to
4-ounce-model weight class. The M5 weighs
9.5 grams (.35 ounce).
Another outstanding choice is the Berg-
5*DSP at .35 ounce and the new Berg-4*DSP
Micro Stamp at just .25 ounce. The Berg
receivers are available from RC Direct. With
the Berg and FMA Direct receivers, you can
remove the receiver case for a further weight
reduction.
For the extra-small models (1.5 ounces
and lighter), the DWE RFFS-100 has been the
popular microsystem for some time. It is a
microreceiver, a built-in ESC with BEC, and
drivers for two magnetic actuators on a single
PC board. The entire board weighs only 1.8
grams (.06 ounce!).
The RFFS-100 receiver is not very
selective, so you can’t use several channels on
either side of your operating frequency when
flying. But this system has provided a load of
indoor RC fun-flying under the right
conditions.
Jean-Marie Piednoir (JMP) of France
makes a new and more selective
microreceiver which Bob Selman Designs
sells in the US. This receiver is claimed to be
extremely narrow band (selective!) and
includes an ESC and two magnetic actuator
drivers. It weighs 2.2 grams (.08 ounce), and
the price without connectors is $89. I’m sure
we will be seeing plenty of these units put
into indoor RC service in the near future.
As I was writing this, I learned of the new
Gasparin Penta 2.4-gram (.8-ounce) fourchannel
receiver, which is claimed to be
incredibly selective and will be selling in the
US at a reasonable $39.
In addition to receivers, servos or actuators
are also important. Conventional servos,
meaning regular proportional feedback
servos, are available at roughly 5.6 grams (.20
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07sig2.QXD 4/26/04 8:33 am Page 50
ounce). Two come to mind: the popular Hitec
HS-50 and the new FMA Direct PS-20. Each
sells for less than $30 and has been reliable.
The German WES-Technik company has
been making a linear-output-type microservo
for the past couple years. It weighs 2.1 grams
(.07 ounce) but is comparatively expensive at
$70-$80 (US).
Stefan Gasparin in conjunction with Didel
(the Swiss gear company) has designed a new
GDservo, which has a rotary output and
weighs 1.33 grams without a case. It will be
pricey, at $98 (US). Stefan also has a new
concept he calls a “Proportional Magnetic
Actuator.” I’ve seen some photos, and the
idea looks entirely realistic. Price is said to be
$39 each (US).
At the bottom of the weight scale are the
truly magnetic actuators; these are coil
devices with magnets that move inside the
coils. They require some patience to install
and offer little control force. That means your
hinges and control linkages must offer the
least possible friction. These magnetic
actuators make RC models of less than 1
ounce total weight possible. Good sources of
magnetic actuators include Bob Selman
Designs, Cloud-9 RC, E-Flight Design, and
DWE.
One last reference is to a “brick” design,
which was popular in the early 1970s. FMA
Direct is almost ready to release a microbrick
that will include one PC board, a narrow-band
receiver, ESC, control actuator drivers, and
two servos or two magnetic actuators. Placing
all of the components on a single board can
make certain installations impractical, but the
bottom line is that the brick eliminates a great
deal of wiring and connectors, thereby
reducing the overall weight. I believe this
concept will find a home in the 2.5- to 4-
ounce model category.
Connectors: The connectors and the wire size
(gauge, which refers to diameter) are
important. You want to carry the current
involved and no more; using a connector that
is too large or a wire with too large a diameter
only adds weight to little airplanes that can’t
afford it.
The larger parking lot-size models can
properly use the popular Anderson Power
Pole-type connectors (also known as Sermos
connectors). You can use these from roughly
6 amps of current up.
The Deans four-pin connectors are popular
for 3 to 6 amps of current. It is a good idea to
gang two pins to make a single connection. In
that case, the four pins yields two conductors.
From 1.5- to 3-amp current, the JST red
plastic housing connector is fine. For less than
1.5 amps of current, the JST white plastic or
Cloud 9 RC Unisex connectors will do the
job.
EFlight Designs carries an excellent line of
submicroconnectors. Wire size can start with
16 gauge for the 8- to 10-amp current. As you
work your way down in current, the wire
gauge can go from 22 to 28, and even 32.
Your hobby supplier can recommend the best
size for each current level. The JST
connectors come with the wire already
attached.
Indoor Flying Tips: If you are already an RC
sport flier or a parking lot flier, you are
certainly qualified to fly indoors; but the
generally “restricted” airspace can be
extremely challenging at times. If you are
lucky enough to be able to fly a 4-ounce
model in an inflated dome, it is almost the
same as flying outdoors—no problem!
However, when you get down to a doubleor
even single-size gymnasium, you get the
feeling that you are always turning the
airplane; there isn’t enough space for
appreciable straightaway flight.
Inside a dome my aircraft have
occasionally hit walls or even the top dead
center of the ceiling. Being such lightweight
models, they seem to just bounce off these
soft surfaces. Most of the time I lose altitude
but can easily recover the airplane to normal
flight.
On the other hand, at the Toledo, Ohio,
PERF (Perrysburg Electric River Fliers)
indoor fly a couple years ago (when it was a
smaller facility), I “shot a basket” with my
little 4.7-ounce AIKA. We had to get a large
stepladder to remove the model from the
basketball hoop/net.
However, before you start worrying about
these possibilities, consider that at such light
weights and wing loadings, not much ever
happens to micromodels—except for midair
52 MODEL AVIATION
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email: [email protected]
07sig2.QXD 4/26/04 8:34 am Page 52
July 2004 55
collisions! They do occur every once in
awhile, but if you build your entire model
from a single sheet of balsa, it’s no big deal!
NIRAC: AMA encourages SIGs to help
organize the various groups within model
aviation. We are lucky to have the National
Indoor Remote-Control Aircraft Council
(NIRAC) represent indoor RC flying within
the Academy. National Indoor Electric
Duration record-holder Bob Wilder of Texas
founded the organization several years ago.
You can access the Web site containing all
of the general information about this SIG at
www.nirac.org. Look it up, get familiar with
the organization, and show your support by
joining.
Once a year NIRAC sponsors a major
indoor RC championship. The 2004 dates are
June 4-6, and the location, as in the past, will
be the big Oakland Yard Athletics facility (an
inflated dome) in Waterford, Michigan
(www.oaklandyard.com/model_aviation.htm).
The flying plan for the three days includes
official indoor RC events including Scale,
racing, cargo lift, Old-Timer climb-and-glide,
endurance, and RC gliders. Between the
events the dome will be opened up for funflying
by all who attend.
NIRAC can also help you find local domes
and large indoor flying facilities. The current
NIRAC president—Dave Robelen—is one of
the most experienced indoor/micro RC fliers.
With indoor RC growing extraordinarily
rapidly, there is much to be learned; new
technology seems to emerge almost weekly.
The big, annual NEAT (Northeast Electric
Aircraft Technology) Fair held in upstate New
York, near the town of Downsville, includes a
series of indoor RC lectures during the three
days of the event.
Sergio Sigras coordinates these seminars.
Some of the most important names in
microflight—Henry Pasquet, Gordon
Johnson, Matt Keennon, Nick Leichty, Fred
Marks, Clarence Hurd, Bob Selman, and
more—provide the latest indoor RC
information.
For the Saturday night of the Fair, Gordon
Johnson sets up an indoor RC flight
demonstration in a double-size gym at nearby
Walton Senior High School. Guest lecturers
get to show their stuff, to the delight of
hundreds of spectators. To learn more about
the Fair, visit www.neatfair.org.
When you are attempting to gain
permission to fly indoor RC at local school
facilities, offer to lecture and/or give classes at
the school to offset your using the venue.
“Yes, you can use our gym, but why not come
in and let our young people learn how they
can participate?”
References: NIRAC is a good starting point.
Several publications regularly offer many
articles about indoor RC. Air Age Media’s RC
MicroFlight is available in hard-copy form
and online. It has been in production for more
than three years. When you subscribe, you
obtain a password that allows you access to all
previously published articles. You can even
download plans from the construction articles.
MA has two talented authors who write
alternating bimonthly columns. Dave Robelen
writes “Micro-Flying” (featuring indoor RC
and parking lot flying) and Paul Bradley
writes “Small-Field Flying” (covering parking
lot flying and backyard flying, and hitting on
indoor RC). I highly recommend these.
You can count on Quiet Flyer, under the
direction of publisher Wil Byers, for many
indoor RC-oriented articles each month. This
magazine specializes in electric power and
sailplane activities.
Flying Models magazine also has
alternating columnists who spend considerable
time in the world of indoor RC: Don Belfort
and Stew Meyers. For many years, RC
Modeler magazine has featured Jim Zare, who
now concentrates most of his activities on
micro and indoor flying.
I hate to sound too commercial, but
roughly two years ago I wrote the book
Getting Started in Backyard Flying. It
contains a lot of material about indoor RC.
You will see how parking lot/backyard flyers
tend to complement the indoor RC flyer. This
book is available from AMA, Tower Hobbies,
Balsa Products, and the publisher’s Web site:
www.rcstore.com/rs/general/books.asp.
In the late 1960s, people such as Dave
Robelen, John Worth, and Howard McEntee
experimented with multichannel proportional
RC control of glow-fueled models that
07sig2.QXD 4/26/04 8:34 am Page 55
weighed only 5-8 ounces! Those airplanes and
their equipment were tedious to work with,
but they did fly.
Soon afterward, AMA Hall of Famer Bill
Cannon of Cannon Electronics produced a
subminiature RC system that made smallscale
RC-model flying practical for everyone.
Bill continued to make that equipment for
many years and should be congratulated for
his efforts and dedication to small-model RC
flying.
Recently we have been privileged to see
the development of micro RC systems, servos,
actuators, Li-Poly batteries, tiny motors, and a
growing group of dedicated RC modelers who
have been willing to make this endeavor
grow. With modern large inflatable domes,
field houses, etc., it is now possible to enjoy
RC flying during all kinds of weather, at any
time of day or night.
Want to have some more fun in RC? Try
flying indoors. MA
Bob Aberle
[email protected]
Manufacturers/distributors:
Firefly coreless micro motors—direct and
geared:
AstroFlight Inc.
www.astroflight.com
GWS motors, propellers, Li-Poly batteries:
Balsa Products
www.balsapr.com
Li-Poly batteries:
Batteries America
www.batteriesamerica.com
JMP receivers, magnetic actuators, Li-Poly
chargers:
Bob Selman Designs
http://users.joplin.com/~bselman/
Voltage cutoff programmable ESCs:
Castle Creations
www.castlecreations.com
Assortment of micro hardware and products:
Cloud 9 RC (John Worth)
(703) 273-0607
Hard-to-get gears, motors, propellers, wire,
connectors:
David Lewis
www.homefly.com
Profile Roadkill series stand-off scale models:
DJ Aerotech
www.djaerotech.com
RFFS-100 micro RC systems, magnetic
actuators, JMP receivers, four-channel
conversion RFFS-100s:
Dynamic Web Enterprises (DWE)
www.smallrc.com
Reduced-size receiver antennas:
E Cubed R/C
www.azarr.com
Magnetic actuators, control-linkage
accessories, connectors:
EFlight Designs
www.eflightdesigns.com
Li-Poly batteries, chargers:
E-Tec (Air Craft)
www.aircraft-world.com
M5 micro DC receivers, submicroservos,
Kokam Li-Poly batteries, chargers:
FMA Direct
www.fmadirect.com
Penta 2.4-gram receivers, GDservo 1.33-gram
servos, new proportional magnetic actuators:
Gasparin
56 MODEL AVIATION
www.gasparin.cz
Motors, propellers, wheels, accessories:
Grand Wing Servo-Tech (GWS)
www.gws.com.tw
Cirrus Micro Joule receivers, ESCs, 3-gram
servos:
Global Hobby Distributors
www.globalhobby.com
Triton Li-Poly chargers:
Great Planes Model Distributors
www.electrifly.com
www.greatplanes.com
HS-50 submicroservo:
Hitec RCD
www.hitecrcd.com
Cirrus Micro Joule receiver, ESC, 3-gram
servos:
Hobby Club
www.hobbyclub.com
Motors, JR radios, Hobby Zone ARF indoor
models, Thunder Power Li-Poly batteries:
Horizon Hobby (GWS)
www.horizonhobby.com
Assortment of tiny direct- and gear-drive
motors:
Kenway Motors
(908) 850-9571
GWS motors, propellers, Li-Poly batteries:
Maxx Products International
www.maxxprod.com
ARF and RTF indoor models:
Megatech
www.megatech.com
Li-Poly batteries, connectors, wire:
Radical RC
www.radicalrc.com
Berg receivers:
RC Direct
www.rc-direct.com
Tiny geared motors, scale model kits:
RCS Technik (Chris Stewart)
www.falconmodels.uk.com
Microreceivers, ESCs, Li-Poly batteries,
chargers, model kits:
Sky Hooks and Rigging
www.microrc.com
Li-Poly batteries:
Thunder Power (Advanced Energy
Technology Inc.)
(702) 228-8883
Indoor model kits and supplies:
Todd Long Models
www.toddsmodels.com
Li-Poly chargers, ARF and RTF model kits:
Tower Hobbies
www.towerhobbies.com
7865 Mill Road, Elkins Park, PA. 19027 USA
Tel. 215 635 6520 Orders ONLY 888 721 0128 Fax. 215 635 4951
Email [email protected] www.sonictronics.com.
NEW
McDaniel R/C A Division of Sonic-Tronics Inc.
Patents, copyrights
and trademarks are
applied.
The New “Go-Slo III” has been
improved with added features.
With the precise performance of
an 8 bit microprocessor the output
is now “user selectable”. Two models are available. One can
drive a single servo, two servos in tandem, two servos with one
reversed or all three servos at once. The other model drives one,
two or three servos in parallel. Both models allow the servo speed to be
adjusted, 2 to 10+ seconds of travel in either direction. Go-Slo III units
are great for precise operation of Flaps, Gear etc. The receiver cable is now a
heavy 22 gage for better power delivery to one, two or three servos.
Go-Slo III‘s are compatible with 4.8 or 6 Volt systems and all proportional servos.
The unit is 1.5” x 1.5”x 3/4” and only .9 oz in weight.
07sig2.QXD 4/26/04 8:34 am Page 56
Edition: Model Aviation - 2004/07
Page Numbers: 42,43,44,45,46,48,50,52,55,56
42 MODEL AVIATION
Introduction to
Indoor Radio Control
I WROTE A feature article published in last
month’s MA titled “Introduction to Parking
Lot Flying.” That category involves flying
relatively small, easy-to-build, and relatively
inexpensive RC models close in.
Aircraft in that size category (up to
roughly 16 ounces total weight) can also,
under certain circumstances, be flown in
indoor facilities. From a practical standpoint,
the larger parking lot-size models can be
flown easily and safely in extra-large indoor
facilities such as golf practice domes
(inflatable) and field houses used for football
practice.
Since winter weather hits many areas
of our country, indoor RC flying during
those months is increasing in popularity.
Not everyone has a golf dome or a field
house in his or her community, but almost
everyone has a school gymnasium or
auditorium that can be an excellent
substitute. To be able to use these smaller
indoor flying facilities, you have to
by Bob Aberle
Author’s original-design Kiwi weighs just 3.4 ounces with 100-
square-inch wing. It uses FMA Direct M5 receiver and two FMA
Direct PS-20 submicroservos. Battery power is two 145 mAh Li-
Poly cells.
Dynamic Web Enterprises proprietors Dan Hurd (L) and his dad
Clarence. Dan holds 1-ounce Pitts Special biplane; Clarence
holds his own-design Lil Skeeter.
Another Joe Wagner FF design from the early
1950s: the Dakota biplane. At right is originalsize
model powered by .049 glow engine. The
author built reduced-size version (left) which
weighs 1.3 ounces with 69 square inches of total
wing area. Power is single 145 mAh Li-Poly
battery. Construction article and plans were
published in May 2003 RC MicroFlight.
Author holds 3.8-ounce version of
popular Joe Wagner FF design—
The Sioux—from the early 1950s.
It has 90-square-inch wing and is
powered by GWS LPS/B2C-C
motor and two FMA Direct/Kokam
340 mAh HD Li-Poly cells. Will
soon be featured as construction
article in Quiet Flyer magazine.
The 2004 NIRAC Indoor Championships will be held
at the big Oakland Yard Athletics facility in Waterford MI.
Fun-flying will be permitted before contest rounds.
All are invited!
07sig2.QXD 4/26/04 8:23 am Page 42
July 2004 43
Pair of typical magnetic actuators. They have a moving magnet within a
coil. Exact separation between two coils and the fact that they are at right
angles to one another provide for control position centering.
Todd Long of Todd’s Models has been selling his Tiny for several years.
Depending on motor and battery choice, this excellent-flying design can
weigh approximately 4 ounces and provide considerable indoor RC funflying.
Don Stackhouse of DJ Aerotech holds two of his Roadkill-series
profile sport-scale models: an Me 109 (L) and a Ryan ST. Each
weighs roughly 3-3.5 ounces and operates on two Li-Poly
batteries.
Closer view of Clarence Hurd’s Lil Skeeter, which was
designed around DWE’s RFFS-100 micro RC system. It
has 46 square inches of wing area and weighs 23 grams
(.81 ounce) including single 130 mAh Li-Poly battery.
Motor is KP-00 geared at 2.67:1.
The Lightning RTF foam model was originally
intended to be an electric-powered FF. An
excellent conversion article by Greg Covey
detailing how to install the DWE RFFS-100 micro
radio system is on the DWE Web site.
DWE RFFS-100 micro RC system is extremely
popular. On this one, PC board weighing 1.8
grams is an RC receiver, ESC, and two magnetic
actuator drivers. It’s one of the best starting
points for flying RC models at or near 1-ounce
total weight.
Photos courtesy the author
07sig2.QXD 4/26/04 8:26 am Page 43
Let’s get into the details of these small, or as we call them, “microsize”
RC aircraft.
Micromodel Sizing: Micro-size models dedicated to indoor RC
flying can range from roughly 8 ounces total weight down to only a
few grams. For this presentation I’m concentrating on 4 ounces total
weight and less.
Right now the range of 4 ounces down to approximately 2.5
ounces can be enjoyed while employing the
available equipment technology, and at
relatively moderate prices. From 2.5 ounces
down to roughly .75 ounce, you will need one
of the several submicroservos on the market
or magnetic actuators. For less than .75 ounce
down to a few grams, you need highly
specialized equipment and considerable
model-building skills.
Typical 4-ounce models can have
approximately 80-120 square inches of wing
area, which will yield wing loadings in the
range of roughly 4-6 ounces/square foot. The
4-ounce total weight could consist of 2.25
ounces of equipment (receiver, two servos,
Li-Poly battery, motor, propeller, and motor
speed controller). The remaining 1.75 ounces
includes the model structure (including
covering, finish, wheels, hinges, and control
linkages).
This typical 4-ounce model can employ
traditional RC equipment, but it will be
smaller in size and weight. The servos will
consider reducing your RC model’s size and weight.
The subject of this presentation is flying RC indoors with models
that weigh less than 3 or 4 ounces. As I noted, there are certain
situations in which you can fly a parking lot model inside. There are
also times in which you can fly a 1-ounce RC model outdoors. To do
that, you need to seek out the dead-calm early-morning or -evening
air. Calm-air outdoor flying also lends itself well to backyard-type
flying, making it a perfect family hobby/sport!
44 MODEL AVIATION
Popular little KP-00 geared motor and companion 3-inch-diameter
propeller. Several sources sell this motor, as noted in text. Power
range is intended for .75- to roughly 1.5-ounce models!
Rear of FMA Direct M5 dual-conversion receiver, which is
smallest dual-conversion RC receiver on the market. It is
available on 72 MHz and six-meter RC channels. Weighs .35
ounce with case!
Basic RC system for 2.5- to 4-ounce model weight (L-R): Castle
Creations Pixie-7P ESC, FMA Direct M5 dual-conversion
microreceiver, two FMA Direct PS-20 submicroservos, two-cell
FMA Direct/Kokam 340 mAh HD Li-Poly battery pack.
Power, RC system needed to fly 1-ounce total-weight model.
Left: KP-00 geared motor, 3-inch-diameter propeller. Top center:
Pair of EFlight Designs magnetic actuators to operate rudder,
elevator. Top right: A 145 mAh Li-Poly battery cell. Just below
that is DWE RFFS-100 PC board containing receiver, ESC, two
magnetic actuator drivers. Lower right: Azarr’s E Cubed RC
reduced-size receiver antenna.
Cutaway of GWS LPS/B2C-C geared motor
mounted to 3⁄16-inch wood dowel. A
setscrew holds motor in place. Two
plywood formers support dowel. It’s
simple and effective! You can easily
change motor at flying site.
Dave Burley has been developing
microservos for indoor RC fliers’ benefit.
His latest (shown) is 1-gram proportional
feedback ultramicroservo. He demonstrated
it to many indoor RC experts at 2003 NEAT
Fair. Dave wants to interest a prominent
manufacturer to pick up on production
rights for it. It worked well, and he hopes it
can be produced at a reasonable unit price.
07sig2.QXD 4/26/04 8:28 am Page 44
July 2004 45
provide regular proportional control, operating from a conventional
RC transmitter.
I have a little indoor sport model that I’m flying at 74 square inches
of wing area and 1.2 ounces total weight. The wing loading works out
to only 2.3 ounces/square foot. It employs two magnetic actuators, and
a 145 mAh Li-Poly battery cell provides all the power. When flown
outdoors, this model doesn’t like any wind! I’ll get into the specifics of
the RC equipment later.
Safety: As is the case with parking lot flying, indoor RC flying has
certain safety issues about which you should be concerned. Even
though you are flying inside, radio signals can travel through buildings
easily without much attenuation of strength. Someone might be flying
right outside your indoor facility, so please check around first. It’s best
to check local hobby shops and RC clubs too.
Also safety related is your model’s speed in flight. An airplane
with less than 100 square inches of wing area and weighing
approximately 10 ounces might be capable of speeds in excess of 60-
75 mph. If it hits something or someone, it could cause physical or
property damage.
Common sense must prevail and reasonable weights and flying
speeds must be commensurate with the size of the facility. A leadertype
person should be in charge of each flying session. That person
must have the last word on who can or can’t fly, and his/her judgment
must be respected at all times!
Micromodel Design: I’ve already suggested weights and wing
loadings, and soon I will get into power systems. There aren’t many
ARF models in the less-than-4-ounce category; that might be
considered the bad news. The good news is that a 4-ounce airplane
can, for the most part, be constructed from scratch, with a minimum of
materials and a minimum of assembly time and skills. I’ve built 1-
ounce RC models from a single sheet of 1⁄32 x 3 x 36-inch balsa. That
is almost as inexpensive as you can go!
The 2- to 4-ounce models can often be built up from the many
rubber-powered kits on the hobby market. Doing this has become
popular. Another possibility are the profile semiscale models, such as
DJ Aerotech’s Roadkill series. Those are easy to build, inexpensive,
and are even supplied with the recommended motor.
If you want to try a 1-ounce model for the first time, the best
trainer is the Lil Skeeter designed by Clarence Hurd of Dynamic Web
Enterprises (DWE). This design was reviewed in the June 2002 RC
MicroFlight newsletter. Plans are available from DWE, and you
receive a free plans copy when you purchase the DWE RFFS-100
micro RC system.
A more ambitious project is Dave Robelen’s Walker, which he
Former AMA executive director and RC MicroFlight founding
editor John Worth holds Pee Wee Flyer made by Estes (the
rocket people). Wal-Mart stores throughout the country sell this
RTF for only $19.95. An article describing it was published in
the October 2003 RC MicroFlight.
Sky Hooks and Rigging owner Tom Mc Cann holds his little
Mosquito indoor slow flyer that Ken Coleman designed. It is
available from Tom as a kit. It spans 24 inches, has 131 square
inches of wing area, weighs 2.25 ounces, and flies on single Li-
Poly battery cell.
Micro-Pod is Bob’s latest original-design indoor RC model. A
construction article was published in November 2003 RC
MicroFlight. It weighs 1.2 ounces and has 74-square-inch wing
area. Power is geared KP-00 motor operating on single 145 mAh
Li-Poly cell.
calls an “ultralite indoor floater.” Dave went to the other extreme and
designed a 1-ounce model with an amazing 357 square inches of wing
area. The resulting wing loading works out to only .4 ounce/square
foot and provides flying speeds of just 3-4 mph. You can walk under
this model while it is flying. The Walker was featured in the July 2003
RC MicroFlight.
07sig2.QXD 4/26/04 8:30 am Page 45
Henry Pasquet is probably the most famous indoor RC flier. His
goal for years has been to build smaller and smaller models. He
holds his 4-inch-span Lacy M-10. It weighs 2.6 grams (total) with a
Gasparin G2.6 CO2 engine. RC system is by Nick Leichty. One No.
337 silver-oxide battery powers the system. It flies very well despite
its size!
US Airways Captain Joe Malinchak’s super-detailed Piper L-4
Grasshopper is military version of Piper Cub. Weighs 1.3 ounces
total including complete scale cockpit interior, landing-gear
shocks, etc. Has geared KP-00 for power! Joe earned DWE award at
2003 NIRAC Championships for RC Scale model with highest
points and weighing less than 1.5 ounces!
NIRAC president, MA columnist, and newly inducted Indoor RC Hall
of Fame member Dave Robelen holds his Scale 34-inch-span Piper
Vagabond. It has 200 square inches of wing area and weighs 4
ounces ready to fly. Power is a DC 5-2.4 coreless motor geared 7.5:1,
running on seven-cell 50 mAh battery pack.
Matt Keennon’s tiny electric-powered Scale P-38 twin spans only
10.5 inches and weighs 35 grams (1.23 ounces) with two M-20
motors and two Kokam 145 mAh Li-Poly cells in parallel. Flight
demos at NEAT Fair were spectacular. Matt makes a living
working on government-sponsored micromodel projects.
Nick Leichty, known for his ultramicro RC models, holds his
Micro Aero Master biplane at 2003 NEAT Fair. It employs one of
his micro three-channel RC systems powered by 4mm motor and
a 40 mAh Li-Poly battery. Model spans 5.5 inches and has 5.5-
gram (.19-ounce) total weight. Approximate flight time on a
charge is five minutes. The author saw the flights and couldn’t
believe it!
46 MODEL AVIATION
07sig2.QXD 4/26/04 8:32 am Page 46
Power Systems: Indoor power systems
primarily involve electric motors, be they
direct drive or gear driven. CO2 power
(compressed gas) is used to some extent, but
the ability to throttle these engines is still in
the experimental stages. Although some of
the tiny glow-fuel and diesel engines might
find their way into indoor RC flying, the
combination of noise and exhaust fumes
makes it somewhat impractical.
Small motors are becoming more and
more popular, and the prices keep going
down. This past year, Grand Wing Servo-
Tech (GWS)—a huge parking lot-/indoormodel
manufacturer—introduced a tiny
geared motor that it calls the “LPS” series.
One of the motors in this category—the
GWS/LPS/B2C—weighs only approximately
12 grams (.42 ounce). It is available in three
gear ratios (4:1, 5:1, 6.2:1).
I’m presently using the 6.2:1 geared
version, which operates on two Li-Poly
battery cells (nominal 7.4 volts) at 700 mA
motor current and 6-watt power level. Using a
GWS 6 x 5 propeller, I generate more than
enough thrust to fly a 4-ounce RC model.
These motors sell for roughly $10. How can
you go wrong?
The .75-1.5-ounce models are generally
powered by pager-derivative motors such as
the Knight & Pridham KP-00 (of which there
are several models with different windings),
with gearing ranging from 2.75:1 upward of
6:1. Each specific gear ratio requires a
different size propeller. Propeller diameters
range from 3 to 6 inches. The gearing choices
attempt to get the most thrust from the motor
while drawing the least current. This is the
game you must play with electric-powered
flight.
The little KP-00 motor will work well on
a single Li-Poly cell drawing roughly 700 mA
of current at approximately a 3-watt power
level. The trick with this is to be able to get an
RC system (receiver and servos) that can also
operate reliably from a single Li-Poly cell at
roughly 3.6 volts.
There are receivers that will do that,
especially those used in conjunction with
magnetic actuators. Bob Selman Designs
offers a new voltage-doubler unit that takes
the single cell voltage and increases it to
roughly 5 volts for more reliable RC
operation.
Many smaller motors are becoming
available for the indoor RC experimenter who
wants to keep reducing that total model
weight to as little as a few grams. Experts
such as Henry Pasquet and Nick Leichty are
regularly flying models weighing roughly .3
ounce! You can find tales of their
experimental efforts in RC MicroFlight. But
as I pointed out before, these truly micro RC
models require a great deal of experience and,
most of all, patience!
As this is being written, I have heard
about several micro manufacturers who have
prototype miniature brushless motors and
companion speed controllers in the works. A
lightweight, highly efficient brushless motor
will provide yet another breakthrough in
indoor RC.
Before leaving the power scene, I’ll
mention that there are CO2 motors now
available for RC model use. They are still
comparatively expensive, but a model’s
weight can be reduced even further than with
electric power because the CO2 tank weighs
less than a battery.
The biggest problem until recently has
been the ability to throttle these air-operated
motors. Stefan Gasparin in the Czech
Republic has made remarkable progress in
this regard. I urge you to look at his Web site.
ESCs: Even the electric motor speed
controllers have been shrunken to fit the
needs of our micro-size aircraft. I think it’s
safe to state that all of the micro ESCs have a
BEC, which allows for the sharing of the one
battery pack.
As you will soon learn, the new Li-Poly
battery technology requires that no cell drop
to less than 3.0 volts when in use. This is a
minimum discharge point. To be on the safe
side, a micro ESC’s low voltage cutoff point
should be set to increments of 3.0 volts per
cell. If you are using one Li-Poly cell, the
cutoff should be 3.0 volts. If your pack has
two Li-Poly cells the cutoff should be 6.0
volts, and so on.
Castle Creations’ Pixie-7P ESC allows
you to program the voltage cutoff point.
There aren’t that many choices, but they will
improve in time. Setting the voltage cutoff on
07sig2.QXD 4/26/04 8:33 am Page 48
the Pixie isn’t all that easy and does require
some patience, but this is the concept you
want to look for in the future!
Batteries: Until recently, the batteries of
choice for 4-ounce and lighter models were
the 100-125 mAh NiMH types, usually in
packs consisting of seven or eight cells. In the
past year we have been introduced to a new
form of battery known as the Li-Poly. These
new cells provide more capacity in a lighterweight
package. Both of those parameters are
exactly what you want for micro RC models.
Of equal interest is the fact that each Li-
Poly cell has a characteristic voltage of close
to 4.0; the older Ni-Cd/NiMH cells had only
1.2 volts per cell. So two Li-Poly cells work
like a six- or seven-cell Ni-Cd/NiMH pack.
We typically see two-cell packs consisting
of 145 mAh or 340 mAh powering 3- to 4-
ounce RC models. A two-cell 145 mAh Li-
Poly pack weighs 8.7 grams (.31 ounce) and
can fly that 3- to 4-ounce model at 700 mA
current (6 watts) for 10-12 minutes and more,
depending on how you throttle the motor in
flight. And two of the 340 mAh Li-Poly cells
(weighing 20.1 grams, or .71 ounce) could
provide up to 30 minutes of motor run time.
However, Li-Poly cells are still quite new
on the market, and they must be taken care of
very carefully. They require a special
dedicated charger and should not be charged
with more than a 1C current, which takes
roughly an hour. Li-Poly batteries should not
be discharged to less than 3.0 volts per cell.
Li-Poly cells are also currently somewhat
limited in their load capabilities. Initial
offerings could only provide loads up to
approximately 5C (five times the capacity of
the battery). Recently a new variety of Li-
Poly cell has been introduced that can stand
loads upward of 20C (quite an
improvement!).
Li-Poly batteries is a subject unto itself. I
wrote a comprehensive article titled
“Introduction to Lithium-Polymer Batteries”
that was published in the May 2004 MA. If
you haven’t read that piece, I highly
recommend that you do so before attempting
to use Li-Poly batteries in a model airplane of
any kind.
Micro RC System and Components: The RC
equipment is conventional technology, but is
obviously made smaller and lighter. An
inexpensive microreceiver is the GWS R-4P,
which has four-channel capability, is a singleconversion
circuit, and weighs 6.8 grams (.25
ounce). At approximately $30, it is a great
buy.
For those who want good range and
selectivity, in a crowded flying environment,
the FMA Direct M5 dual-conversion receiver
is an excellent choice, especially in the 2.5- to
4-ounce-model weight class. The M5 weighs
9.5 grams (.35 ounce).
Another outstanding choice is the Berg-
5*DSP at .35 ounce and the new Berg-4*DSP
Micro Stamp at just .25 ounce. The Berg
receivers are available from RC Direct. With
the Berg and FMA Direct receivers, you can
remove the receiver case for a further weight
reduction.
For the extra-small models (1.5 ounces
and lighter), the DWE RFFS-100 has been the
popular microsystem for some time. It is a
microreceiver, a built-in ESC with BEC, and
drivers for two magnetic actuators on a single
PC board. The entire board weighs only 1.8
grams (.06 ounce!).
The RFFS-100 receiver is not very
selective, so you can’t use several channels on
either side of your operating frequency when
flying. But this system has provided a load of
indoor RC fun-flying under the right
conditions.
Jean-Marie Piednoir (JMP) of France
makes a new and more selective
microreceiver which Bob Selman Designs
sells in the US. This receiver is claimed to be
extremely narrow band (selective!) and
includes an ESC and two magnetic actuator
drivers. It weighs 2.2 grams (.08 ounce), and
the price without connectors is $89. I’m sure
we will be seeing plenty of these units put
into indoor RC service in the near future.
As I was writing this, I learned of the new
Gasparin Penta 2.4-gram (.8-ounce) fourchannel
receiver, which is claimed to be
incredibly selective and will be selling in the
US at a reasonable $39.
In addition to receivers, servos or actuators
are also important. Conventional servos,
meaning regular proportional feedback
servos, are available at roughly 5.6 grams (.20
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07sig2.QXD 4/26/04 8:33 am Page 50
ounce). Two come to mind: the popular Hitec
HS-50 and the new FMA Direct PS-20. Each
sells for less than $30 and has been reliable.
The German WES-Technik company has
been making a linear-output-type microservo
for the past couple years. It weighs 2.1 grams
(.07 ounce) but is comparatively expensive at
$70-$80 (US).
Stefan Gasparin in conjunction with Didel
(the Swiss gear company) has designed a new
GDservo, which has a rotary output and
weighs 1.33 grams without a case. It will be
pricey, at $98 (US). Stefan also has a new
concept he calls a “Proportional Magnetic
Actuator.” I’ve seen some photos, and the
idea looks entirely realistic. Price is said to be
$39 each (US).
At the bottom of the weight scale are the
truly magnetic actuators; these are coil
devices with magnets that move inside the
coils. They require some patience to install
and offer little control force. That means your
hinges and control linkages must offer the
least possible friction. These magnetic
actuators make RC models of less than 1
ounce total weight possible. Good sources of
magnetic actuators include Bob Selman
Designs, Cloud-9 RC, E-Flight Design, and
DWE.
One last reference is to a “brick” design,
which was popular in the early 1970s. FMA
Direct is almost ready to release a microbrick
that will include one PC board, a narrow-band
receiver, ESC, control actuator drivers, and
two servos or two magnetic actuators. Placing
all of the components on a single board can
make certain installations impractical, but the
bottom line is that the brick eliminates a great
deal of wiring and connectors, thereby
reducing the overall weight. I believe this
concept will find a home in the 2.5- to 4-
ounce model category.
Connectors: The connectors and the wire size
(gauge, which refers to diameter) are
important. You want to carry the current
involved and no more; using a connector that
is too large or a wire with too large a diameter
only adds weight to little airplanes that can’t
afford it.
The larger parking lot-size models can
properly use the popular Anderson Power
Pole-type connectors (also known as Sermos
connectors). You can use these from roughly
6 amps of current up.
The Deans four-pin connectors are popular
for 3 to 6 amps of current. It is a good idea to
gang two pins to make a single connection. In
that case, the four pins yields two conductors.
From 1.5- to 3-amp current, the JST red
plastic housing connector is fine. For less than
1.5 amps of current, the JST white plastic or
Cloud 9 RC Unisex connectors will do the
job.
EFlight Designs carries an excellent line of
submicroconnectors. Wire size can start with
16 gauge for the 8- to 10-amp current. As you
work your way down in current, the wire
gauge can go from 22 to 28, and even 32.
Your hobby supplier can recommend the best
size for each current level. The JST
connectors come with the wire already
attached.
Indoor Flying Tips: If you are already an RC
sport flier or a parking lot flier, you are
certainly qualified to fly indoors; but the
generally “restricted” airspace can be
extremely challenging at times. If you are
lucky enough to be able to fly a 4-ounce
model in an inflated dome, it is almost the
same as flying outdoors—no problem!
However, when you get down to a doubleor
even single-size gymnasium, you get the
feeling that you are always turning the
airplane; there isn’t enough space for
appreciable straightaway flight.
Inside a dome my aircraft have
occasionally hit walls or even the top dead
center of the ceiling. Being such lightweight
models, they seem to just bounce off these
soft surfaces. Most of the time I lose altitude
but can easily recover the airplane to normal
flight.
On the other hand, at the Toledo, Ohio,
PERF (Perrysburg Electric River Fliers)
indoor fly a couple years ago (when it was a
smaller facility), I “shot a basket” with my
little 4.7-ounce AIKA. We had to get a large
stepladder to remove the model from the
basketball hoop/net.
However, before you start worrying about
these possibilities, consider that at such light
weights and wing loadings, not much ever
happens to micromodels—except for midair
52 MODEL AVIATION
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engines, glow plugs and other
accessories. Fox has become a
name modelers can trust when
it comes to durability, power,
and performance at an
affordable price. (479) 646-1656
Fax (479) 646-1757
5305 Towson Avenue
Fort Smith, AR 72901
www.foxmanufacturing.com
email: [email protected]
07sig2.QXD 4/26/04 8:34 am Page 52
July 2004 55
collisions! They do occur every once in
awhile, but if you build your entire model
from a single sheet of balsa, it’s no big deal!
NIRAC: AMA encourages SIGs to help
organize the various groups within model
aviation. We are lucky to have the National
Indoor Remote-Control Aircraft Council
(NIRAC) represent indoor RC flying within
the Academy. National Indoor Electric
Duration record-holder Bob Wilder of Texas
founded the organization several years ago.
You can access the Web site containing all
of the general information about this SIG at
www.nirac.org. Look it up, get familiar with
the organization, and show your support by
joining.
Once a year NIRAC sponsors a major
indoor RC championship. The 2004 dates are
June 4-6, and the location, as in the past, will
be the big Oakland Yard Athletics facility (an
inflated dome) in Waterford, Michigan
(www.oaklandyard.com/model_aviation.htm).
The flying plan for the three days includes
official indoor RC events including Scale,
racing, cargo lift, Old-Timer climb-and-glide,
endurance, and RC gliders. Between the
events the dome will be opened up for funflying
by all who attend.
NIRAC can also help you find local domes
and large indoor flying facilities. The current
NIRAC president—Dave Robelen—is one of
the most experienced indoor/micro RC fliers.
With indoor RC growing extraordinarily
rapidly, there is much to be learned; new
technology seems to emerge almost weekly.
The big, annual NEAT (Northeast Electric
Aircraft Technology) Fair held in upstate New
York, near the town of Downsville, includes a
series of indoor RC lectures during the three
days of the event.
Sergio Sigras coordinates these seminars.
Some of the most important names in
microflight—Henry Pasquet, Gordon
Johnson, Matt Keennon, Nick Leichty, Fred
Marks, Clarence Hurd, Bob Selman, and
more—provide the latest indoor RC
information.
For the Saturday night of the Fair, Gordon
Johnson sets up an indoor RC flight
demonstration in a double-size gym at nearby
Walton Senior High School. Guest lecturers
get to show their stuff, to the delight of
hundreds of spectators. To learn more about
the Fair, visit www.neatfair.org.
When you are attempting to gain
permission to fly indoor RC at local school
facilities, offer to lecture and/or give classes at
the school to offset your using the venue.
“Yes, you can use our gym, but why not come
in and let our young people learn how they
can participate?”
References: NIRAC is a good starting point.
Several publications regularly offer many
articles about indoor RC. Air Age Media’s RC
MicroFlight is available in hard-copy form
and online. It has been in production for more
than three years. When you subscribe, you
obtain a password that allows you access to all
previously published articles. You can even
download plans from the construction articles.
MA has two talented authors who write
alternating bimonthly columns. Dave Robelen
writes “Micro-Flying” (featuring indoor RC
and parking lot flying) and Paul Bradley
writes “Small-Field Flying” (covering parking
lot flying and backyard flying, and hitting on
indoor RC). I highly recommend these.
You can count on Quiet Flyer, under the
direction of publisher Wil Byers, for many
indoor RC-oriented articles each month. This
magazine specializes in electric power and
sailplane activities.
Flying Models magazine also has
alternating columnists who spend considerable
time in the world of indoor RC: Don Belfort
and Stew Meyers. For many years, RC
Modeler magazine has featured Jim Zare, who
now concentrates most of his activities on
micro and indoor flying.
I hate to sound too commercial, but
roughly two years ago I wrote the book
Getting Started in Backyard Flying. It
contains a lot of material about indoor RC.
You will see how parking lot/backyard flyers
tend to complement the indoor RC flyer. This
book is available from AMA, Tower Hobbies,
Balsa Products, and the publisher’s Web site:
www.rcstore.com/rs/general/books.asp.
In the late 1960s, people such as Dave
Robelen, John Worth, and Howard McEntee
experimented with multichannel proportional
RC control of glow-fueled models that
07sig2.QXD 4/26/04 8:34 am Page 55
weighed only 5-8 ounces! Those airplanes and
their equipment were tedious to work with,
but they did fly.
Soon afterward, AMA Hall of Famer Bill
Cannon of Cannon Electronics produced a
subminiature RC system that made smallscale
RC-model flying practical for everyone.
Bill continued to make that equipment for
many years and should be congratulated for
his efforts and dedication to small-model RC
flying.
Recently we have been privileged to see
the development of micro RC systems, servos,
actuators, Li-Poly batteries, tiny motors, and a
growing group of dedicated RC modelers who
have been willing to make this endeavor
grow. With modern large inflatable domes,
field houses, etc., it is now possible to enjoy
RC flying during all kinds of weather, at any
time of day or night.
Want to have some more fun in RC? Try
flying indoors. MA
Bob Aberle
[email protected]
Manufacturers/distributors:
Firefly coreless micro motors—direct and
geared:
AstroFlight Inc.
www.astroflight.com
GWS motors, propellers, Li-Poly batteries:
Balsa Products
www.balsapr.com
Li-Poly batteries:
Batteries America
www.batteriesamerica.com
JMP receivers, magnetic actuators, Li-Poly
chargers:
Bob Selman Designs
http://users.joplin.com/~bselman/
Voltage cutoff programmable ESCs:
Castle Creations
www.castlecreations.com
Assortment of micro hardware and products:
Cloud 9 RC (John Worth)
(703) 273-0607
Hard-to-get gears, motors, propellers, wire,
connectors:
David Lewis
www.homefly.com
Profile Roadkill series stand-off scale models:
DJ Aerotech
www.djaerotech.com
RFFS-100 micro RC systems, magnetic
actuators, JMP receivers, four-channel
conversion RFFS-100s:
Dynamic Web Enterprises (DWE)
www.smallrc.com
Reduced-size receiver antennas:
E Cubed R/C
www.azarr.com
Magnetic actuators, control-linkage
accessories, connectors:
EFlight Designs
www.eflightdesigns.com
Li-Poly batteries, chargers:
E-Tec (Air Craft)
www.aircraft-world.com
M5 micro DC receivers, submicroservos,
Kokam Li-Poly batteries, chargers:
FMA Direct
www.fmadirect.com
Penta 2.4-gram receivers, GDservo 1.33-gram
servos, new proportional magnetic actuators:
Gasparin
56 MODEL AVIATION
www.gasparin.cz
Motors, propellers, wheels, accessories:
Grand Wing Servo-Tech (GWS)
www.gws.com.tw
Cirrus Micro Joule receivers, ESCs, 3-gram
servos:
Global Hobby Distributors
www.globalhobby.com
Triton Li-Poly chargers:
Great Planes Model Distributors
www.electrifly.com
www.greatplanes.com
HS-50 submicroservo:
Hitec RCD
www.hitecrcd.com
Cirrus Micro Joule receiver, ESC, 3-gram
servos:
Hobby Club
www.hobbyclub.com
Motors, JR radios, Hobby Zone ARF indoor
models, Thunder Power Li-Poly batteries:
Horizon Hobby (GWS)
www.horizonhobby.com
Assortment of tiny direct- and gear-drive
motors:
Kenway Motors
(908) 850-9571
GWS motors, propellers, Li-Poly batteries:
Maxx Products International
www.maxxprod.com
ARF and RTF indoor models:
Megatech
www.megatech.com
Li-Poly batteries, connectors, wire:
Radical RC
www.radicalrc.com
Berg receivers:
RC Direct
www.rc-direct.com
Tiny geared motors, scale model kits:
RCS Technik (Chris Stewart)
www.falconmodels.uk.com
Microreceivers, ESCs, Li-Poly batteries,
chargers, model kits:
Sky Hooks and Rigging
www.microrc.com
Li-Poly batteries:
Thunder Power (Advanced Energy
Technology Inc.)
(702) 228-8883
Indoor model kits and supplies:
Todd Long Models
www.toddsmodels.com
Li-Poly chargers, ARF and RTF model kits:
Tower Hobbies
www.towerhobbies.com
7865 Mill Road, Elkins Park, PA. 19027 USA
Tel. 215 635 6520 Orders ONLY 888 721 0128 Fax. 215 635 4951
Email [email protected] www.sonictronics.com.
NEW
McDaniel R/C A Division of Sonic-Tronics Inc.
Patents, copyrights
and trademarks are
applied.
The New “Go-Slo III” has been
improved with added features.
With the precise performance of
an 8 bit microprocessor the output
is now “user selectable”. Two models are available. One can
drive a single servo, two servos in tandem, two servos with one
reversed or all three servos at once. The other model drives one,
two or three servos in parallel. Both models allow the servo speed to be
adjusted, 2 to 10+ seconds of travel in either direction. Go-Slo III units
are great for precise operation of Flaps, Gear etc. The receiver cable is now a
heavy 22 gage for better power delivery to one, two or three servos.
Go-Slo III‘s are compatible with 4.8 or 6 Volt systems and all proportional servos.
The unit is 1.5” x 1.5”x 3/4” and only .9 oz in weight.
07sig2.QXD 4/26/04 8:34 am Page 56
Edition: Model Aviation - 2004/07
Page Numbers: 42,43,44,45,46,48,50,52,55,56
42 MODEL AVIATION
Introduction to
Indoor Radio Control
I WROTE A feature article published in last
month’s MA titled “Introduction to Parking
Lot Flying.” That category involves flying
relatively small, easy-to-build, and relatively
inexpensive RC models close in.
Aircraft in that size category (up to
roughly 16 ounces total weight) can also,
under certain circumstances, be flown in
indoor facilities. From a practical standpoint,
the larger parking lot-size models can be
flown easily and safely in extra-large indoor
facilities such as golf practice domes
(inflatable) and field houses used for football
practice.
Since winter weather hits many areas
of our country, indoor RC flying during
those months is increasing in popularity.
Not everyone has a golf dome or a field
house in his or her community, but almost
everyone has a school gymnasium or
auditorium that can be an excellent
substitute. To be able to use these smaller
indoor flying facilities, you have to
by Bob Aberle
Author’s original-design Kiwi weighs just 3.4 ounces with 100-
square-inch wing. It uses FMA Direct M5 receiver and two FMA
Direct PS-20 submicroservos. Battery power is two 145 mAh Li-
Poly cells.
Dynamic Web Enterprises proprietors Dan Hurd (L) and his dad
Clarence. Dan holds 1-ounce Pitts Special biplane; Clarence
holds his own-design Lil Skeeter.
Another Joe Wagner FF design from the early
1950s: the Dakota biplane. At right is originalsize
model powered by .049 glow engine. The
author built reduced-size version (left) which
weighs 1.3 ounces with 69 square inches of total
wing area. Power is single 145 mAh Li-Poly
battery. Construction article and plans were
published in May 2003 RC MicroFlight.
Author holds 3.8-ounce version of
popular Joe Wagner FF design—
The Sioux—from the early 1950s.
It has 90-square-inch wing and is
powered by GWS LPS/B2C-C
motor and two FMA Direct/Kokam
340 mAh HD Li-Poly cells. Will
soon be featured as construction
article in Quiet Flyer magazine.
The 2004 NIRAC Indoor Championships will be held
at the big Oakland Yard Athletics facility in Waterford MI.
Fun-flying will be permitted before contest rounds.
All are invited!
07sig2.QXD 4/26/04 8:23 am Page 42
July 2004 43
Pair of typical magnetic actuators. They have a moving magnet within a
coil. Exact separation between two coils and the fact that they are at right
angles to one another provide for control position centering.
Todd Long of Todd’s Models has been selling his Tiny for several years.
Depending on motor and battery choice, this excellent-flying design can
weigh approximately 4 ounces and provide considerable indoor RC funflying.
Don Stackhouse of DJ Aerotech holds two of his Roadkill-series
profile sport-scale models: an Me 109 (L) and a Ryan ST. Each
weighs roughly 3-3.5 ounces and operates on two Li-Poly
batteries.
Closer view of Clarence Hurd’s Lil Skeeter, which was
designed around DWE’s RFFS-100 micro RC system. It
has 46 square inches of wing area and weighs 23 grams
(.81 ounce) including single 130 mAh Li-Poly battery.
Motor is KP-00 geared at 2.67:1.
The Lightning RTF foam model was originally
intended to be an electric-powered FF. An
excellent conversion article by Greg Covey
detailing how to install the DWE RFFS-100 micro
radio system is on the DWE Web site.
DWE RFFS-100 micro RC system is extremely
popular. On this one, PC board weighing 1.8
grams is an RC receiver, ESC, and two magnetic
actuator drivers. It’s one of the best starting
points for flying RC models at or near 1-ounce
total weight.
Photos courtesy the author
07sig2.QXD 4/26/04 8:26 am Page 43
Let’s get into the details of these small, or as we call them, “microsize”
RC aircraft.
Micromodel Sizing: Micro-size models dedicated to indoor RC
flying can range from roughly 8 ounces total weight down to only a
few grams. For this presentation I’m concentrating on 4 ounces total
weight and less.
Right now the range of 4 ounces down to approximately 2.5
ounces can be enjoyed while employing the
available equipment technology, and at
relatively moderate prices. From 2.5 ounces
down to roughly .75 ounce, you will need one
of the several submicroservos on the market
or magnetic actuators. For less than .75 ounce
down to a few grams, you need highly
specialized equipment and considerable
model-building skills.
Typical 4-ounce models can have
approximately 80-120 square inches of wing
area, which will yield wing loadings in the
range of roughly 4-6 ounces/square foot. The
4-ounce total weight could consist of 2.25
ounces of equipment (receiver, two servos,
Li-Poly battery, motor, propeller, and motor
speed controller). The remaining 1.75 ounces
includes the model structure (including
covering, finish, wheels, hinges, and control
linkages).
This typical 4-ounce model can employ
traditional RC equipment, but it will be
smaller in size and weight. The servos will
consider reducing your RC model’s size and weight.
The subject of this presentation is flying RC indoors with models
that weigh less than 3 or 4 ounces. As I noted, there are certain
situations in which you can fly a parking lot model inside. There are
also times in which you can fly a 1-ounce RC model outdoors. To do
that, you need to seek out the dead-calm early-morning or -evening
air. Calm-air outdoor flying also lends itself well to backyard-type
flying, making it a perfect family hobby/sport!
44 MODEL AVIATION
Popular little KP-00 geared motor and companion 3-inch-diameter
propeller. Several sources sell this motor, as noted in text. Power
range is intended for .75- to roughly 1.5-ounce models!
Rear of FMA Direct M5 dual-conversion receiver, which is
smallest dual-conversion RC receiver on the market. It is
available on 72 MHz and six-meter RC channels. Weighs .35
ounce with case!
Basic RC system for 2.5- to 4-ounce model weight (L-R): Castle
Creations Pixie-7P ESC, FMA Direct M5 dual-conversion
microreceiver, two FMA Direct PS-20 submicroservos, two-cell
FMA Direct/Kokam 340 mAh HD Li-Poly battery pack.
Power, RC system needed to fly 1-ounce total-weight model.
Left: KP-00 geared motor, 3-inch-diameter propeller. Top center:
Pair of EFlight Designs magnetic actuators to operate rudder,
elevator. Top right: A 145 mAh Li-Poly battery cell. Just below
that is DWE RFFS-100 PC board containing receiver, ESC, two
magnetic actuator drivers. Lower right: Azarr’s E Cubed RC
reduced-size receiver antenna.
Cutaway of GWS LPS/B2C-C geared motor
mounted to 3⁄16-inch wood dowel. A
setscrew holds motor in place. Two
plywood formers support dowel. It’s
simple and effective! You can easily
change motor at flying site.
Dave Burley has been developing
microservos for indoor RC fliers’ benefit.
His latest (shown) is 1-gram proportional
feedback ultramicroservo. He demonstrated
it to many indoor RC experts at 2003 NEAT
Fair. Dave wants to interest a prominent
manufacturer to pick up on production
rights for it. It worked well, and he hopes it
can be produced at a reasonable unit price.
07sig2.QXD 4/26/04 8:28 am Page 44
July 2004 45
provide regular proportional control, operating from a conventional
RC transmitter.
I have a little indoor sport model that I’m flying at 74 square inches
of wing area and 1.2 ounces total weight. The wing loading works out
to only 2.3 ounces/square foot. It employs two magnetic actuators, and
a 145 mAh Li-Poly battery cell provides all the power. When flown
outdoors, this model doesn’t like any wind! I’ll get into the specifics of
the RC equipment later.
Safety: As is the case with parking lot flying, indoor RC flying has
certain safety issues about which you should be concerned. Even
though you are flying inside, radio signals can travel through buildings
easily without much attenuation of strength. Someone might be flying
right outside your indoor facility, so please check around first. It’s best
to check local hobby shops and RC clubs too.
Also safety related is your model’s speed in flight. An airplane
with less than 100 square inches of wing area and weighing
approximately 10 ounces might be capable of speeds in excess of 60-
75 mph. If it hits something or someone, it could cause physical or
property damage.
Common sense must prevail and reasonable weights and flying
speeds must be commensurate with the size of the facility. A leadertype
person should be in charge of each flying session. That person
must have the last word on who can or can’t fly, and his/her judgment
must be respected at all times!
Micromodel Design: I’ve already suggested weights and wing
loadings, and soon I will get into power systems. There aren’t many
ARF models in the less-than-4-ounce category; that might be
considered the bad news. The good news is that a 4-ounce airplane
can, for the most part, be constructed from scratch, with a minimum of
materials and a minimum of assembly time and skills. I’ve built 1-
ounce RC models from a single sheet of 1⁄32 x 3 x 36-inch balsa. That
is almost as inexpensive as you can go!
The 2- to 4-ounce models can often be built up from the many
rubber-powered kits on the hobby market. Doing this has become
popular. Another possibility are the profile semiscale models, such as
DJ Aerotech’s Roadkill series. Those are easy to build, inexpensive,
and are even supplied with the recommended motor.
If you want to try a 1-ounce model for the first time, the best
trainer is the Lil Skeeter designed by Clarence Hurd of Dynamic Web
Enterprises (DWE). This design was reviewed in the June 2002 RC
MicroFlight newsletter. Plans are available from DWE, and you
receive a free plans copy when you purchase the DWE RFFS-100
micro RC system.
A more ambitious project is Dave Robelen’s Walker, which he
Former AMA executive director and RC MicroFlight founding
editor John Worth holds Pee Wee Flyer made by Estes (the
rocket people). Wal-Mart stores throughout the country sell this
RTF for only $19.95. An article describing it was published in
the October 2003 RC MicroFlight.
Sky Hooks and Rigging owner Tom Mc Cann holds his little
Mosquito indoor slow flyer that Ken Coleman designed. It is
available from Tom as a kit. It spans 24 inches, has 131 square
inches of wing area, weighs 2.25 ounces, and flies on single Li-
Poly battery cell.
Micro-Pod is Bob’s latest original-design indoor RC model. A
construction article was published in November 2003 RC
MicroFlight. It weighs 1.2 ounces and has 74-square-inch wing
area. Power is geared KP-00 motor operating on single 145 mAh
Li-Poly cell.
calls an “ultralite indoor floater.” Dave went to the other extreme and
designed a 1-ounce model with an amazing 357 square inches of wing
area. The resulting wing loading works out to only .4 ounce/square
foot and provides flying speeds of just 3-4 mph. You can walk under
this model while it is flying. The Walker was featured in the July 2003
RC MicroFlight.
07sig2.QXD 4/26/04 8:30 am Page 45
Henry Pasquet is probably the most famous indoor RC flier. His
goal for years has been to build smaller and smaller models. He
holds his 4-inch-span Lacy M-10. It weighs 2.6 grams (total) with a
Gasparin G2.6 CO2 engine. RC system is by Nick Leichty. One No.
337 silver-oxide battery powers the system. It flies very well despite
its size!
US Airways Captain Joe Malinchak’s super-detailed Piper L-4
Grasshopper is military version of Piper Cub. Weighs 1.3 ounces
total including complete scale cockpit interior, landing-gear
shocks, etc. Has geared KP-00 for power! Joe earned DWE award at
2003 NIRAC Championships for RC Scale model with highest
points and weighing less than 1.5 ounces!
NIRAC president, MA columnist, and newly inducted Indoor RC Hall
of Fame member Dave Robelen holds his Scale 34-inch-span Piper
Vagabond. It has 200 square inches of wing area and weighs 4
ounces ready to fly. Power is a DC 5-2.4 coreless motor geared 7.5:1,
running on seven-cell 50 mAh battery pack.
Matt Keennon’s tiny electric-powered Scale P-38 twin spans only
10.5 inches and weighs 35 grams (1.23 ounces) with two M-20
motors and two Kokam 145 mAh Li-Poly cells in parallel. Flight
demos at NEAT Fair were spectacular. Matt makes a living
working on government-sponsored micromodel projects.
Nick Leichty, known for his ultramicro RC models, holds his
Micro Aero Master biplane at 2003 NEAT Fair. It employs one of
his micro three-channel RC systems powered by 4mm motor and
a 40 mAh Li-Poly battery. Model spans 5.5 inches and has 5.5-
gram (.19-ounce) total weight. Approximate flight time on a
charge is five minutes. The author saw the flights and couldn’t
believe it!
46 MODEL AVIATION
07sig2.QXD 4/26/04 8:32 am Page 46
Power Systems: Indoor power systems
primarily involve electric motors, be they
direct drive or gear driven. CO2 power
(compressed gas) is used to some extent, but
the ability to throttle these engines is still in
the experimental stages. Although some of
the tiny glow-fuel and diesel engines might
find their way into indoor RC flying, the
combination of noise and exhaust fumes
makes it somewhat impractical.
Small motors are becoming more and
more popular, and the prices keep going
down. This past year, Grand Wing Servo-
Tech (GWS)—a huge parking lot-/indoormodel
manufacturer—introduced a tiny
geared motor that it calls the “LPS” series.
One of the motors in this category—the
GWS/LPS/B2C—weighs only approximately
12 grams (.42 ounce). It is available in three
gear ratios (4:1, 5:1, 6.2:1).
I’m presently using the 6.2:1 geared
version, which operates on two Li-Poly
battery cells (nominal 7.4 volts) at 700 mA
motor current and 6-watt power level. Using a
GWS 6 x 5 propeller, I generate more than
enough thrust to fly a 4-ounce RC model.
These motors sell for roughly $10. How can
you go wrong?
The .75-1.5-ounce models are generally
powered by pager-derivative motors such as
the Knight & Pridham KP-00 (of which there
are several models with different windings),
with gearing ranging from 2.75:1 upward of
6:1. Each specific gear ratio requires a
different size propeller. Propeller diameters
range from 3 to 6 inches. The gearing choices
attempt to get the most thrust from the motor
while drawing the least current. This is the
game you must play with electric-powered
flight.
The little KP-00 motor will work well on
a single Li-Poly cell drawing roughly 700 mA
of current at approximately a 3-watt power
level. The trick with this is to be able to get an
RC system (receiver and servos) that can also
operate reliably from a single Li-Poly cell at
roughly 3.6 volts.
There are receivers that will do that,
especially those used in conjunction with
magnetic actuators. Bob Selman Designs
offers a new voltage-doubler unit that takes
the single cell voltage and increases it to
roughly 5 volts for more reliable RC
operation.
Many smaller motors are becoming
available for the indoor RC experimenter who
wants to keep reducing that total model
weight to as little as a few grams. Experts
such as Henry Pasquet and Nick Leichty are
regularly flying models weighing roughly .3
ounce! You can find tales of their
experimental efforts in RC MicroFlight. But
as I pointed out before, these truly micro RC
models require a great deal of experience and,
most of all, patience!
As this is being written, I have heard
about several micro manufacturers who have
prototype miniature brushless motors and
companion speed controllers in the works. A
lightweight, highly efficient brushless motor
will provide yet another breakthrough in
indoor RC.
Before leaving the power scene, I’ll
mention that there are CO2 motors now
available for RC model use. They are still
comparatively expensive, but a model’s
weight can be reduced even further than with
electric power because the CO2 tank weighs
less than a battery.
The biggest problem until recently has
been the ability to throttle these air-operated
motors. Stefan Gasparin in the Czech
Republic has made remarkable progress in
this regard. I urge you to look at his Web site.
ESCs: Even the electric motor speed
controllers have been shrunken to fit the
needs of our micro-size aircraft. I think it’s
safe to state that all of the micro ESCs have a
BEC, which allows for the sharing of the one
battery pack.
As you will soon learn, the new Li-Poly
battery technology requires that no cell drop
to less than 3.0 volts when in use. This is a
minimum discharge point. To be on the safe
side, a micro ESC’s low voltage cutoff point
should be set to increments of 3.0 volts per
cell. If you are using one Li-Poly cell, the
cutoff should be 3.0 volts. If your pack has
two Li-Poly cells the cutoff should be 6.0
volts, and so on.
Castle Creations’ Pixie-7P ESC allows
you to program the voltage cutoff point.
There aren’t that many choices, but they will
improve in time. Setting the voltage cutoff on
07sig2.QXD 4/26/04 8:33 am Page 48
the Pixie isn’t all that easy and does require
some patience, but this is the concept you
want to look for in the future!
Batteries: Until recently, the batteries of
choice for 4-ounce and lighter models were
the 100-125 mAh NiMH types, usually in
packs consisting of seven or eight cells. In the
past year we have been introduced to a new
form of battery known as the Li-Poly. These
new cells provide more capacity in a lighterweight
package. Both of those parameters are
exactly what you want for micro RC models.
Of equal interest is the fact that each Li-
Poly cell has a characteristic voltage of close
to 4.0; the older Ni-Cd/NiMH cells had only
1.2 volts per cell. So two Li-Poly cells work
like a six- or seven-cell Ni-Cd/NiMH pack.
We typically see two-cell packs consisting
of 145 mAh or 340 mAh powering 3- to 4-
ounce RC models. A two-cell 145 mAh Li-
Poly pack weighs 8.7 grams (.31 ounce) and
can fly that 3- to 4-ounce model at 700 mA
current (6 watts) for 10-12 minutes and more,
depending on how you throttle the motor in
flight. And two of the 340 mAh Li-Poly cells
(weighing 20.1 grams, or .71 ounce) could
provide up to 30 minutes of motor run time.
However, Li-Poly cells are still quite new
on the market, and they must be taken care of
very carefully. They require a special
dedicated charger and should not be charged
with more than a 1C current, which takes
roughly an hour. Li-Poly batteries should not
be discharged to less than 3.0 volts per cell.
Li-Poly cells are also currently somewhat
limited in their load capabilities. Initial
offerings could only provide loads up to
approximately 5C (five times the capacity of
the battery). Recently a new variety of Li-
Poly cell has been introduced that can stand
loads upward of 20C (quite an
improvement!).
Li-Poly batteries is a subject unto itself. I
wrote a comprehensive article titled
“Introduction to Lithium-Polymer Batteries”
that was published in the May 2004 MA. If
you haven’t read that piece, I highly
recommend that you do so before attempting
to use Li-Poly batteries in a model airplane of
any kind.
Micro RC System and Components: The RC
equipment is conventional technology, but is
obviously made smaller and lighter. An
inexpensive microreceiver is the GWS R-4P,
which has four-channel capability, is a singleconversion
circuit, and weighs 6.8 grams (.25
ounce). At approximately $30, it is a great
buy.
For those who want good range and
selectivity, in a crowded flying environment,
the FMA Direct M5 dual-conversion receiver
is an excellent choice, especially in the 2.5- to
4-ounce-model weight class. The M5 weighs
9.5 grams (.35 ounce).
Another outstanding choice is the Berg-
5*DSP at .35 ounce and the new Berg-4*DSP
Micro Stamp at just .25 ounce. The Berg
receivers are available from RC Direct. With
the Berg and FMA Direct receivers, you can
remove the receiver case for a further weight
reduction.
For the extra-small models (1.5 ounces
and lighter), the DWE RFFS-100 has been the
popular microsystem for some time. It is a
microreceiver, a built-in ESC with BEC, and
drivers for two magnetic actuators on a single
PC board. The entire board weighs only 1.8
grams (.06 ounce!).
The RFFS-100 receiver is not very
selective, so you can’t use several channels on
either side of your operating frequency when
flying. But this system has provided a load of
indoor RC fun-flying under the right
conditions.
Jean-Marie Piednoir (JMP) of France
makes a new and more selective
microreceiver which Bob Selman Designs
sells in the US. This receiver is claimed to be
extremely narrow band (selective!) and
includes an ESC and two magnetic actuator
drivers. It weighs 2.2 grams (.08 ounce), and
the price without connectors is $89. I’m sure
we will be seeing plenty of these units put
into indoor RC service in the near future.
As I was writing this, I learned of the new
Gasparin Penta 2.4-gram (.8-ounce) fourchannel
receiver, which is claimed to be
incredibly selective and will be selling in the
US at a reasonable $39.
In addition to receivers, servos or actuators
are also important. Conventional servos,
meaning regular proportional feedback
servos, are available at roughly 5.6 grams (.20
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07sig2.QXD 4/26/04 8:33 am Page 50
ounce). Two come to mind: the popular Hitec
HS-50 and the new FMA Direct PS-20. Each
sells for less than $30 and has been reliable.
The German WES-Technik company has
been making a linear-output-type microservo
for the past couple years. It weighs 2.1 grams
(.07 ounce) but is comparatively expensive at
$70-$80 (US).
Stefan Gasparin in conjunction with Didel
(the Swiss gear company) has designed a new
GDservo, which has a rotary output and
weighs 1.33 grams without a case. It will be
pricey, at $98 (US). Stefan also has a new
concept he calls a “Proportional Magnetic
Actuator.” I’ve seen some photos, and the
idea looks entirely realistic. Price is said to be
$39 each (US).
At the bottom of the weight scale are the
truly magnetic actuators; these are coil
devices with magnets that move inside the
coils. They require some patience to install
and offer little control force. That means your
hinges and control linkages must offer the
least possible friction. These magnetic
actuators make RC models of less than 1
ounce total weight possible. Good sources of
magnetic actuators include Bob Selman
Designs, Cloud-9 RC, E-Flight Design, and
DWE.
One last reference is to a “brick” design,
which was popular in the early 1970s. FMA
Direct is almost ready to release a microbrick
that will include one PC board, a narrow-band
receiver, ESC, control actuator drivers, and
two servos or two magnetic actuators. Placing
all of the components on a single board can
make certain installations impractical, but the
bottom line is that the brick eliminates a great
deal of wiring and connectors, thereby
reducing the overall weight. I believe this
concept will find a home in the 2.5- to 4-
ounce model category.
Connectors: The connectors and the wire size
(gauge, which refers to diameter) are
important. You want to carry the current
involved and no more; using a connector that
is too large or a wire with too large a diameter
only adds weight to little airplanes that can’t
afford it.
The larger parking lot-size models can
properly use the popular Anderson Power
Pole-type connectors (also known as Sermos
connectors). You can use these from roughly
6 amps of current up.
The Deans four-pin connectors are popular
for 3 to 6 amps of current. It is a good idea to
gang two pins to make a single connection. In
that case, the four pins yields two conductors.
From 1.5- to 3-amp current, the JST red
plastic housing connector is fine. For less than
1.5 amps of current, the JST white plastic or
Cloud 9 RC Unisex connectors will do the
job.
EFlight Designs carries an excellent line of
submicroconnectors. Wire size can start with
16 gauge for the 8- to 10-amp current. As you
work your way down in current, the wire
gauge can go from 22 to 28, and even 32.
Your hobby supplier can recommend the best
size for each current level. The JST
connectors come with the wire already
attached.
Indoor Flying Tips: If you are already an RC
sport flier or a parking lot flier, you are
certainly qualified to fly indoors; but the
generally “restricted” airspace can be
extremely challenging at times. If you are
lucky enough to be able to fly a 4-ounce
model in an inflated dome, it is almost the
same as flying outdoors—no problem!
However, when you get down to a doubleor
even single-size gymnasium, you get the
feeling that you are always turning the
airplane; there isn’t enough space for
appreciable straightaway flight.
Inside a dome my aircraft have
occasionally hit walls or even the top dead
center of the ceiling. Being such lightweight
models, they seem to just bounce off these
soft surfaces. Most of the time I lose altitude
but can easily recover the airplane to normal
flight.
On the other hand, at the Toledo, Ohio,
PERF (Perrysburg Electric River Fliers)
indoor fly a couple years ago (when it was a
smaller facility), I “shot a basket” with my
little 4.7-ounce AIKA. We had to get a large
stepladder to remove the model from the
basketball hoop/net.
However, before you start worrying about
these possibilities, consider that at such light
weights and wing loadings, not much ever
happens to micromodels—except for midair
52 MODEL AVIATION
Since 1948 Fox Manufacturing
Company has been producing
high quality model airplane
engines, glow plugs and other
accessories. Fox has become a
name modelers can trust when
it comes to durability, power,
and performance at an
affordable price. (479) 646-1656
Fax (479) 646-1757
5305 Towson Avenue
Fort Smith, AR 72901
www.foxmanufacturing.com
email: [email protected]
07sig2.QXD 4/26/04 8:34 am Page 52
July 2004 55
collisions! They do occur every once in
awhile, but if you build your entire model
from a single sheet of balsa, it’s no big deal!
NIRAC: AMA encourages SIGs to help
organize the various groups within model
aviation. We are lucky to have the National
Indoor Remote-Control Aircraft Council
(NIRAC) represent indoor RC flying within
the Academy. National Indoor Electric
Duration record-holder Bob Wilder of Texas
founded the organization several years ago.
You can access the Web site containing all
of the general information about this SIG at
www.nirac.org. Look it up, get familiar with
the organization, and show your support by
joining.
Once a year NIRAC sponsors a major
indoor RC championship. The 2004 dates are
June 4-6, and the location, as in the past, will
be the big Oakland Yard Athletics facility (an
inflated dome) in Waterford, Michigan
(www.oaklandyard.com/model_aviation.htm).
The flying plan for the three days includes
official indoor RC events including Scale,
racing, cargo lift, Old-Timer climb-and-glide,
endurance, and RC gliders. Between the
events the dome will be opened up for funflying
by all who attend.
NIRAC can also help you find local domes
and large indoor flying facilities. The current
NIRAC president—Dave Robelen—is one of
the most experienced indoor/micro RC fliers.
With indoor RC growing extraordinarily
rapidly, there is much to be learned; new
technology seems to emerge almost weekly.
The big, annual NEAT (Northeast Electric
Aircraft Technology) Fair held in upstate New
York, near the town of Downsville, includes a
series of indoor RC lectures during the three
days of the event.
Sergio Sigras coordinates these seminars.
Some of the most important names in
microflight—Henry Pasquet, Gordon
Johnson, Matt Keennon, Nick Leichty, Fred
Marks, Clarence Hurd, Bob Selman, and
more—provide the latest indoor RC
information.
For the Saturday night of the Fair, Gordon
Johnson sets up an indoor RC flight
demonstration in a double-size gym at nearby
Walton Senior High School. Guest lecturers
get to show their stuff, to the delight of
hundreds of spectators. To learn more about
the Fair, visit www.neatfair.org.
When you are attempting to gain
permission to fly indoor RC at local school
facilities, offer to lecture and/or give classes at
the school to offset your using the venue.
“Yes, you can use our gym, but why not come
in and let our young people learn how they
can participate?”
References: NIRAC is a good starting point.
Several publications regularly offer many
articles about indoor RC. Air Age Media’s RC
MicroFlight is available in hard-copy form
and online. It has been in production for more
than three years. When you subscribe, you
obtain a password that allows you access to all
previously published articles. You can even
download plans from the construction articles.
MA has two talented authors who write
alternating bimonthly columns. Dave Robelen
writes “Micro-Flying” (featuring indoor RC
and parking lot flying) and Paul Bradley
writes “Small-Field Flying” (covering parking
lot flying and backyard flying, and hitting on
indoor RC). I highly recommend these.
You can count on Quiet Flyer, under the
direction of publisher Wil Byers, for many
indoor RC-oriented articles each month. This
magazine specializes in electric power and
sailplane activities.
Flying Models magazine also has
alternating columnists who spend considerable
time in the world of indoor RC: Don Belfort
and Stew Meyers. For many years, RC
Modeler magazine has featured Jim Zare, who
now concentrates most of his activities on
micro and indoor flying.
I hate to sound too commercial, but
roughly two years ago I wrote the book
Getting Started in Backyard Flying. It
contains a lot of material about indoor RC.
You will see how parking lot/backyard flyers
tend to complement the indoor RC flyer. This
book is available from AMA, Tower Hobbies,
Balsa Products, and the publisher’s Web site:
www.rcstore.com/rs/general/books.asp.
In the late 1960s, people such as Dave
Robelen, John Worth, and Howard McEntee
experimented with multichannel proportional
RC control of glow-fueled models that
07sig2.QXD 4/26/04 8:34 am Page 55
weighed only 5-8 ounces! Those airplanes and
their equipment were tedious to work with,
but they did fly.
Soon afterward, AMA Hall of Famer Bill
Cannon of Cannon Electronics produced a
subminiature RC system that made smallscale
RC-model flying practical for everyone.
Bill continued to make that equipment for
many years and should be congratulated for
his efforts and dedication to small-model RC
flying.
Recently we have been privileged to see
the development of micro RC systems, servos,
actuators, Li-Poly batteries, tiny motors, and a
growing group of dedicated RC modelers who
have been willing to make this endeavor
grow. With modern large inflatable domes,
field houses, etc., it is now possible to enjoy
RC flying during all kinds of weather, at any
time of day or night.
Want to have some more fun in RC? Try
flying indoors. MA
Bob Aberle
[email protected]
Manufacturers/distributors:
Firefly coreless micro motors—direct and
geared:
AstroFlight Inc.
www.astroflight.com
GWS motors, propellers, Li-Poly batteries:
Balsa Products
www.balsapr.com
Li-Poly batteries:
Batteries America
www.batteriesamerica.com
JMP receivers, magnetic actuators, Li-Poly
chargers:
Bob Selman Designs
http://users.joplin.com/~bselman/
Voltage cutoff programmable ESCs:
Castle Creations
www.castlecreations.com
Assortment of micro hardware and products:
Cloud 9 RC (John Worth)
(703) 273-0607
Hard-to-get gears, motors, propellers, wire,
connectors:
David Lewis
www.homefly.com
Profile Roadkill series stand-off scale models:
DJ Aerotech
www.djaerotech.com
RFFS-100 micro RC systems, magnetic
actuators, JMP receivers, four-channel
conversion RFFS-100s:
Dynamic Web Enterprises (DWE)
www.smallrc.com
Reduced-size receiver antennas:
E Cubed R/C
www.azarr.com
Magnetic actuators, control-linkage
accessories, connectors:
EFlight Designs
www.eflightdesigns.com
Li-Poly batteries, chargers:
E-Tec (Air Craft)
www.aircraft-world.com
M5 micro DC receivers, submicroservos,
Kokam Li-Poly batteries, chargers:
FMA Direct
www.fmadirect.com
Penta 2.4-gram receivers, GDservo 1.33-gram
servos, new proportional magnetic actuators:
Gasparin
56 MODEL AVIATION
www.gasparin.cz
Motors, propellers, wheels, accessories:
Grand Wing Servo-Tech (GWS)
www.gws.com.tw
Cirrus Micro Joule receivers, ESCs, 3-gram
servos:
Global Hobby Distributors
www.globalhobby.com
Triton Li-Poly chargers:
Great Planes Model Distributors
www.electrifly.com
www.greatplanes.com
HS-50 submicroservo:
Hitec RCD
www.hitecrcd.com
Cirrus Micro Joule receiver, ESC, 3-gram
servos:
Hobby Club
www.hobbyclub.com
Motors, JR radios, Hobby Zone ARF indoor
models, Thunder Power Li-Poly batteries:
Horizon Hobby (GWS)
www.horizonhobby.com
Assortment of tiny direct- and gear-drive
motors:
Kenway Motors
(908) 850-9571
GWS motors, propellers, Li-Poly batteries:
Maxx Products International
www.maxxprod.com
ARF and RTF indoor models:
Megatech
www.megatech.com
Li-Poly batteries, connectors, wire:
Radical RC
www.radicalrc.com
Berg receivers:
RC Direct
www.rc-direct.com
Tiny geared motors, scale model kits:
RCS Technik (Chris Stewart)
www.falconmodels.uk.com
Microreceivers, ESCs, Li-Poly batteries,
chargers, model kits:
Sky Hooks and Rigging
www.microrc.com
Li-Poly batteries:
Thunder Power (Advanced Energy
Technology Inc.)
(702) 228-8883
Indoor model kits and supplies:
Todd Long Models
www.toddsmodels.com
Li-Poly chargers, ARF and RTF model kits:
Tower Hobbies
www.towerhobbies.com
7865 Mill Road, Elkins Park, PA. 19027 USA
Tel. 215 635 6520 Orders ONLY 888 721 0128 Fax. 215 635 4951
Email [email protected] www.sonictronics.com.
NEW
McDaniel R/C A Division of Sonic-Tronics Inc.
Patents, copyrights
and trademarks are
applied.
The New “Go-Slo III” has been
improved with added features.
With the precise performance of
an 8 bit microprocessor the output
is now “user selectable”. Two models are available. One can
drive a single servo, two servos in tandem, two servos with one
reversed or all three servos at once. The other model drives one,
two or three servos in parallel. Both models allow the servo speed to be
adjusted, 2 to 10+ seconds of travel in either direction. Go-Slo III units
are great for precise operation of Flaps, Gear etc. The receiver cable is now a
heavy 22 gage for better power delivery to one, two or three servos.
Go-Slo III‘s are compatible with 4.8 or 6 Volt systems and all proportional servos.
The unit is 1.5” x 1.5”x 3/4” and only .9 oz in weight.
07sig2.QXD 4/26/04 8:34 am Page 56
Edition: Model Aviation - 2004/07
Page Numbers: 42,43,44,45,46,48,50,52,55,56
42 MODEL AVIATION
Introduction to
Indoor Radio Control
I WROTE A feature article published in last
month’s MA titled “Introduction to Parking
Lot Flying.” That category involves flying
relatively small, easy-to-build, and relatively
inexpensive RC models close in.
Aircraft in that size category (up to
roughly 16 ounces total weight) can also,
under certain circumstances, be flown in
indoor facilities. From a practical standpoint,
the larger parking lot-size models can be
flown easily and safely in extra-large indoor
facilities such as golf practice domes
(inflatable) and field houses used for football
practice.
Since winter weather hits many areas
of our country, indoor RC flying during
those months is increasing in popularity.
Not everyone has a golf dome or a field
house in his or her community, but almost
everyone has a school gymnasium or
auditorium that can be an excellent
substitute. To be able to use these smaller
indoor flying facilities, you have to
by Bob Aberle
Author’s original-design Kiwi weighs just 3.4 ounces with 100-
square-inch wing. It uses FMA Direct M5 receiver and two FMA
Direct PS-20 submicroservos. Battery power is two 145 mAh Li-
Poly cells.
Dynamic Web Enterprises proprietors Dan Hurd (L) and his dad
Clarence. Dan holds 1-ounce Pitts Special biplane; Clarence
holds his own-design Lil Skeeter.
Another Joe Wagner FF design from the early
1950s: the Dakota biplane. At right is originalsize
model powered by .049 glow engine. The
author built reduced-size version (left) which
weighs 1.3 ounces with 69 square inches of total
wing area. Power is single 145 mAh Li-Poly
battery. Construction article and plans were
published in May 2003 RC MicroFlight.
Author holds 3.8-ounce version of
popular Joe Wagner FF design—
The Sioux—from the early 1950s.
It has 90-square-inch wing and is
powered by GWS LPS/B2C-C
motor and two FMA Direct/Kokam
340 mAh HD Li-Poly cells. Will
soon be featured as construction
article in Quiet Flyer magazine.
The 2004 NIRAC Indoor Championships will be held
at the big Oakland Yard Athletics facility in Waterford MI.
Fun-flying will be permitted before contest rounds.
All are invited!
07sig2.QXD 4/26/04 8:23 am Page 42
July 2004 43
Pair of typical magnetic actuators. They have a moving magnet within a
coil. Exact separation between two coils and the fact that they are at right
angles to one another provide for control position centering.
Todd Long of Todd’s Models has been selling his Tiny for several years.
Depending on motor and battery choice, this excellent-flying design can
weigh approximately 4 ounces and provide considerable indoor RC funflying.
Don Stackhouse of DJ Aerotech holds two of his Roadkill-series
profile sport-scale models: an Me 109 (L) and a Ryan ST. Each
weighs roughly 3-3.5 ounces and operates on two Li-Poly
batteries.
Closer view of Clarence Hurd’s Lil Skeeter, which was
designed around DWE’s RFFS-100 micro RC system. It
has 46 square inches of wing area and weighs 23 grams
(.81 ounce) including single 130 mAh Li-Poly battery.
Motor is KP-00 geared at 2.67:1.
The Lightning RTF foam model was originally
intended to be an electric-powered FF. An
excellent conversion article by Greg Covey
detailing how to install the DWE RFFS-100 micro
radio system is on the DWE Web site.
DWE RFFS-100 micro RC system is extremely
popular. On this one, PC board weighing 1.8
grams is an RC receiver, ESC, and two magnetic
actuator drivers. It’s one of the best starting
points for flying RC models at or near 1-ounce
total weight.
Photos courtesy the author
07sig2.QXD 4/26/04 8:26 am Page 43
Let’s get into the details of these small, or as we call them, “microsize”
RC aircraft.
Micromodel Sizing: Micro-size models dedicated to indoor RC
flying can range from roughly 8 ounces total weight down to only a
few grams. For this presentation I’m concentrating on 4 ounces total
weight and less.
Right now the range of 4 ounces down to approximately 2.5
ounces can be enjoyed while employing the
available equipment technology, and at
relatively moderate prices. From 2.5 ounces
down to roughly .75 ounce, you will need one
of the several submicroservos on the market
or magnetic actuators. For less than .75 ounce
down to a few grams, you need highly
specialized equipment and considerable
model-building skills.
Typical 4-ounce models can have
approximately 80-120 square inches of wing
area, which will yield wing loadings in the
range of roughly 4-6 ounces/square foot. The
4-ounce total weight could consist of 2.25
ounces of equipment (receiver, two servos,
Li-Poly battery, motor, propeller, and motor
speed controller). The remaining 1.75 ounces
includes the model structure (including
covering, finish, wheels, hinges, and control
linkages).
This typical 4-ounce model can employ
traditional RC equipment, but it will be
smaller in size and weight. The servos will
consider reducing your RC model’s size and weight.
The subject of this presentation is flying RC indoors with models
that weigh less than 3 or 4 ounces. As I noted, there are certain
situations in which you can fly a parking lot model inside. There are
also times in which you can fly a 1-ounce RC model outdoors. To do
that, you need to seek out the dead-calm early-morning or -evening
air. Calm-air outdoor flying also lends itself well to backyard-type
flying, making it a perfect family hobby/sport!
44 MODEL AVIATION
Popular little KP-00 geared motor and companion 3-inch-diameter
propeller. Several sources sell this motor, as noted in text. Power
range is intended for .75- to roughly 1.5-ounce models!
Rear of FMA Direct M5 dual-conversion receiver, which is
smallest dual-conversion RC receiver on the market. It is
available on 72 MHz and six-meter RC channels. Weighs .35
ounce with case!
Basic RC system for 2.5- to 4-ounce model weight (L-R): Castle
Creations Pixie-7P ESC, FMA Direct M5 dual-conversion
microreceiver, two FMA Direct PS-20 submicroservos, two-cell
FMA Direct/Kokam 340 mAh HD Li-Poly battery pack.
Power, RC system needed to fly 1-ounce total-weight model.
Left: KP-00 geared motor, 3-inch-diameter propeller. Top center:
Pair of EFlight Designs magnetic actuators to operate rudder,
elevator. Top right: A 145 mAh Li-Poly battery cell. Just below
that is DWE RFFS-100 PC board containing receiver, ESC, two
magnetic actuator drivers. Lower right: Azarr’s E Cubed RC
reduced-size receiver antenna.
Cutaway of GWS LPS/B2C-C geared motor
mounted to 3⁄16-inch wood dowel. A
setscrew holds motor in place. Two
plywood formers support dowel. It’s
simple and effective! You can easily
change motor at flying site.
Dave Burley has been developing
microservos for indoor RC fliers’ benefit.
His latest (shown) is 1-gram proportional
feedback ultramicroservo. He demonstrated
it to many indoor RC experts at 2003 NEAT
Fair. Dave wants to interest a prominent
manufacturer to pick up on production
rights for it. It worked well, and he hopes it
can be produced at a reasonable unit price.
07sig2.QXD 4/26/04 8:28 am Page 44
July 2004 45
provide regular proportional control, operating from a conventional
RC transmitter.
I have a little indoor sport model that I’m flying at 74 square inches
of wing area and 1.2 ounces total weight. The wing loading works out
to only 2.3 ounces/square foot. It employs two magnetic actuators, and
a 145 mAh Li-Poly battery cell provides all the power. When flown
outdoors, this model doesn’t like any wind! I’ll get into the specifics of
the RC equipment later.
Safety: As is the case with parking lot flying, indoor RC flying has
certain safety issues about which you should be concerned. Even
though you are flying inside, radio signals can travel through buildings
easily without much attenuation of strength. Someone might be flying
right outside your indoor facility, so please check around first. It’s best
to check local hobby shops and RC clubs too.
Also safety related is your model’s speed in flight. An airplane
with less than 100 square inches of wing area and weighing
approximately 10 ounces might be capable of speeds in excess of 60-
75 mph. If it hits something or someone, it could cause physical or
property damage.
Common sense must prevail and reasonable weights and flying
speeds must be commensurate with the size of the facility. A leadertype
person should be in charge of each flying session. That person
must have the last word on who can or can’t fly, and his/her judgment
must be respected at all times!
Micromodel Design: I’ve already suggested weights and wing
loadings, and soon I will get into power systems. There aren’t many
ARF models in the less-than-4-ounce category; that might be
considered the bad news. The good news is that a 4-ounce airplane
can, for the most part, be constructed from scratch, with a minimum of
materials and a minimum of assembly time and skills. I’ve built 1-
ounce RC models from a single sheet of 1⁄32 x 3 x 36-inch balsa. That
is almost as inexpensive as you can go!
The 2- to 4-ounce models can often be built up from the many
rubber-powered kits on the hobby market. Doing this has become
popular. Another possibility are the profile semiscale models, such as
DJ Aerotech’s Roadkill series. Those are easy to build, inexpensive,
and are even supplied with the recommended motor.
If you want to try a 1-ounce model for the first time, the best
trainer is the Lil Skeeter designed by Clarence Hurd of Dynamic Web
Enterprises (DWE). This design was reviewed in the June 2002 RC
MicroFlight newsletter. Plans are available from DWE, and you
receive a free plans copy when you purchase the DWE RFFS-100
micro RC system.
A more ambitious project is Dave Robelen’s Walker, which he
Former AMA executive director and RC MicroFlight founding
editor John Worth holds Pee Wee Flyer made by Estes (the
rocket people). Wal-Mart stores throughout the country sell this
RTF for only $19.95. An article describing it was published in
the October 2003 RC MicroFlight.
Sky Hooks and Rigging owner Tom Mc Cann holds his little
Mosquito indoor slow flyer that Ken Coleman designed. It is
available from Tom as a kit. It spans 24 inches, has 131 square
inches of wing area, weighs 2.25 ounces, and flies on single Li-
Poly battery cell.
Micro-Pod is Bob’s latest original-design indoor RC model. A
construction article was published in November 2003 RC
MicroFlight. It weighs 1.2 ounces and has 74-square-inch wing
area. Power is geared KP-00 motor operating on single 145 mAh
Li-Poly cell.
calls an “ultralite indoor floater.” Dave went to the other extreme and
designed a 1-ounce model with an amazing 357 square inches of wing
area. The resulting wing loading works out to only .4 ounce/square
foot and provides flying speeds of just 3-4 mph. You can walk under
this model while it is flying. The Walker was featured in the July 2003
RC MicroFlight.
07sig2.QXD 4/26/04 8:30 am Page 45
Henry Pasquet is probably the most famous indoor RC flier. His
goal for years has been to build smaller and smaller models. He
holds his 4-inch-span Lacy M-10. It weighs 2.6 grams (total) with a
Gasparin G2.6 CO2 engine. RC system is by Nick Leichty. One No.
337 silver-oxide battery powers the system. It flies very well despite
its size!
US Airways Captain Joe Malinchak’s super-detailed Piper L-4
Grasshopper is military version of Piper Cub. Weighs 1.3 ounces
total including complete scale cockpit interior, landing-gear
shocks, etc. Has geared KP-00 for power! Joe earned DWE award at
2003 NIRAC Championships for RC Scale model with highest
points and weighing less than 1.5 ounces!
NIRAC president, MA columnist, and newly inducted Indoor RC Hall
of Fame member Dave Robelen holds his Scale 34-inch-span Piper
Vagabond. It has 200 square inches of wing area and weighs 4
ounces ready to fly. Power is a DC 5-2.4 coreless motor geared 7.5:1,
running on seven-cell 50 mAh battery pack.
Matt Keennon’s tiny electric-powered Scale P-38 twin spans only
10.5 inches and weighs 35 grams (1.23 ounces) with two M-20
motors and two Kokam 145 mAh Li-Poly cells in parallel. Flight
demos at NEAT Fair were spectacular. Matt makes a living
working on government-sponsored micromodel projects.
Nick Leichty, known for his ultramicro RC models, holds his
Micro Aero Master biplane at 2003 NEAT Fair. It employs one of
his micro three-channel RC systems powered by 4mm motor and
a 40 mAh Li-Poly battery. Model spans 5.5 inches and has 5.5-
gram (.19-ounce) total weight. Approximate flight time on a
charge is five minutes. The author saw the flights and couldn’t
believe it!
46 MODEL AVIATION
07sig2.QXD 4/26/04 8:32 am Page 46
Power Systems: Indoor power systems
primarily involve electric motors, be they
direct drive or gear driven. CO2 power
(compressed gas) is used to some extent, but
the ability to throttle these engines is still in
the experimental stages. Although some of
the tiny glow-fuel and diesel engines might
find their way into indoor RC flying, the
combination of noise and exhaust fumes
makes it somewhat impractical.
Small motors are becoming more and
more popular, and the prices keep going
down. This past year, Grand Wing Servo-
Tech (GWS)—a huge parking lot-/indoormodel
manufacturer—introduced a tiny
geared motor that it calls the “LPS” series.
One of the motors in this category—the
GWS/LPS/B2C—weighs only approximately
12 grams (.42 ounce). It is available in three
gear ratios (4:1, 5:1, 6.2:1).
I’m presently using the 6.2:1 geared
version, which operates on two Li-Poly
battery cells (nominal 7.4 volts) at 700 mA
motor current and 6-watt power level. Using a
GWS 6 x 5 propeller, I generate more than
enough thrust to fly a 4-ounce RC model.
These motors sell for roughly $10. How can
you go wrong?
The .75-1.5-ounce models are generally
powered by pager-derivative motors such as
the Knight & Pridham KP-00 (of which there
are several models with different windings),
with gearing ranging from 2.75:1 upward of
6:1. Each specific gear ratio requires a
different size propeller. Propeller diameters
range from 3 to 6 inches. The gearing choices
attempt to get the most thrust from the motor
while drawing the least current. This is the
game you must play with electric-powered
flight.
The little KP-00 motor will work well on
a single Li-Poly cell drawing roughly 700 mA
of current at approximately a 3-watt power
level. The trick with this is to be able to get an
RC system (receiver and servos) that can also
operate reliably from a single Li-Poly cell at
roughly 3.6 volts.
There are receivers that will do that,
especially those used in conjunction with
magnetic actuators. Bob Selman Designs
offers a new voltage-doubler unit that takes
the single cell voltage and increases it to
roughly 5 volts for more reliable RC
operation.
Many smaller motors are becoming
available for the indoor RC experimenter who
wants to keep reducing that total model
weight to as little as a few grams. Experts
such as Henry Pasquet and Nick Leichty are
regularly flying models weighing roughly .3
ounce! You can find tales of their
experimental efforts in RC MicroFlight. But
as I pointed out before, these truly micro RC
models require a great deal of experience and,
most of all, patience!
As this is being written, I have heard
about several micro manufacturers who have
prototype miniature brushless motors and
companion speed controllers in the works. A
lightweight, highly efficient brushless motor
will provide yet another breakthrough in
indoor RC.
Before leaving the power scene, I’ll
mention that there are CO2 motors now
available for RC model use. They are still
comparatively expensive, but a model’s
weight can be reduced even further than with
electric power because the CO2 tank weighs
less than a battery.
The biggest problem until recently has
been the ability to throttle these air-operated
motors. Stefan Gasparin in the Czech
Republic has made remarkable progress in
this regard. I urge you to look at his Web site.
ESCs: Even the electric motor speed
controllers have been shrunken to fit the
needs of our micro-size aircraft. I think it’s
safe to state that all of the micro ESCs have a
BEC, which allows for the sharing of the one
battery pack.
As you will soon learn, the new Li-Poly
battery technology requires that no cell drop
to less than 3.0 volts when in use. This is a
minimum discharge point. To be on the safe
side, a micro ESC’s low voltage cutoff point
should be set to increments of 3.0 volts per
cell. If you are using one Li-Poly cell, the
cutoff should be 3.0 volts. If your pack has
two Li-Poly cells the cutoff should be 6.0
volts, and so on.
Castle Creations’ Pixie-7P ESC allows
you to program the voltage cutoff point.
There aren’t that many choices, but they will
improve in time. Setting the voltage cutoff on
07sig2.QXD 4/26/04 8:33 am Page 48
the Pixie isn’t all that easy and does require
some patience, but this is the concept you
want to look for in the future!
Batteries: Until recently, the batteries of
choice for 4-ounce and lighter models were
the 100-125 mAh NiMH types, usually in
packs consisting of seven or eight cells. In the
past year we have been introduced to a new
form of battery known as the Li-Poly. These
new cells provide more capacity in a lighterweight
package. Both of those parameters are
exactly what you want for micro RC models.
Of equal interest is the fact that each Li-
Poly cell has a characteristic voltage of close
to 4.0; the older Ni-Cd/NiMH cells had only
1.2 volts per cell. So two Li-Poly cells work
like a six- or seven-cell Ni-Cd/NiMH pack.
We typically see two-cell packs consisting
of 145 mAh or 340 mAh powering 3- to 4-
ounce RC models. A two-cell 145 mAh Li-
Poly pack weighs 8.7 grams (.31 ounce) and
can fly that 3- to 4-ounce model at 700 mA
current (6 watts) for 10-12 minutes and more,
depending on how you throttle the motor in
flight. And two of the 340 mAh Li-Poly cells
(weighing 20.1 grams, or .71 ounce) could
provide up to 30 minutes of motor run time.
However, Li-Poly cells are still quite new
on the market, and they must be taken care of
very carefully. They require a special
dedicated charger and should not be charged
with more than a 1C current, which takes
roughly an hour. Li-Poly batteries should not
be discharged to less than 3.0 volts per cell.
Li-Poly cells are also currently somewhat
limited in their load capabilities. Initial
offerings could only provide loads up to
approximately 5C (five times the capacity of
the battery). Recently a new variety of Li-
Poly cell has been introduced that can stand
loads upward of 20C (quite an
improvement!).
Li-Poly batteries is a subject unto itself. I
wrote a comprehensive article titled
“Introduction to Lithium-Polymer Batteries”
that was published in the May 2004 MA. If
you haven’t read that piece, I highly
recommend that you do so before attempting
to use Li-Poly batteries in a model airplane of
any kind.
Micro RC System and Components: The RC
equipment is conventional technology, but is
obviously made smaller and lighter. An
inexpensive microreceiver is the GWS R-4P,
which has four-channel capability, is a singleconversion
circuit, and weighs 6.8 grams (.25
ounce). At approximately $30, it is a great
buy.
For those who want good range and
selectivity, in a crowded flying environment,
the FMA Direct M5 dual-conversion receiver
is an excellent choice, especially in the 2.5- to
4-ounce-model weight class. The M5 weighs
9.5 grams (.35 ounce).
Another outstanding choice is the Berg-
5*DSP at .35 ounce and the new Berg-4*DSP
Micro Stamp at just .25 ounce. The Berg
receivers are available from RC Direct. With
the Berg and FMA Direct receivers, you can
remove the receiver case for a further weight
reduction.
For the extra-small models (1.5 ounces
and lighter), the DWE RFFS-100 has been the
popular microsystem for some time. It is a
microreceiver, a built-in ESC with BEC, and
drivers for two magnetic actuators on a single
PC board. The entire board weighs only 1.8
grams (.06 ounce!).
The RFFS-100 receiver is not very
selective, so you can’t use several channels on
either side of your operating frequency when
flying. But this system has provided a load of
indoor RC fun-flying under the right
conditions.
Jean-Marie Piednoir (JMP) of France
makes a new and more selective
microreceiver which Bob Selman Designs
sells in the US. This receiver is claimed to be
extremely narrow band (selective!) and
includes an ESC and two magnetic actuator
drivers. It weighs 2.2 grams (.08 ounce), and
the price without connectors is $89. I’m sure
we will be seeing plenty of these units put
into indoor RC service in the near future.
As I was writing this, I learned of the new
Gasparin Penta 2.4-gram (.8-ounce) fourchannel
receiver, which is claimed to be
incredibly selective and will be selling in the
US at a reasonable $39.
In addition to receivers, servos or actuators
are also important. Conventional servos,
meaning regular proportional feedback
servos, are available at roughly 5.6 grams (.20
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07sig2.QXD 4/26/04 8:33 am Page 50
ounce). Two come to mind: the popular Hitec
HS-50 and the new FMA Direct PS-20. Each
sells for less than $30 and has been reliable.
The German WES-Technik company has
been making a linear-output-type microservo
for the past couple years. It weighs 2.1 grams
(.07 ounce) but is comparatively expensive at
$70-$80 (US).
Stefan Gasparin in conjunction with Didel
(the Swiss gear company) has designed a new
GDservo, which has a rotary output and
weighs 1.33 grams without a case. It will be
pricey, at $98 (US). Stefan also has a new
concept he calls a “Proportional Magnetic
Actuator.” I’ve seen some photos, and the
idea looks entirely realistic. Price is said to be
$39 each (US).
At the bottom of the weight scale are the
truly magnetic actuators; these are coil
devices with magnets that move inside the
coils. They require some patience to install
and offer little control force. That means your
hinges and control linkages must offer the
least possible friction. These magnetic
actuators make RC models of less than 1
ounce total weight possible. Good sources of
magnetic actuators include Bob Selman
Designs, Cloud-9 RC, E-Flight Design, and
DWE.
One last reference is to a “brick” design,
which was popular in the early 1970s. FMA
Direct is almost ready to release a microbrick
that will include one PC board, a narrow-band
receiver, ESC, control actuator drivers, and
two servos or two magnetic actuators. Placing
all of the components on a single board can
make certain installations impractical, but the
bottom line is that the brick eliminates a great
deal of wiring and connectors, thereby
reducing the overall weight. I believe this
concept will find a home in the 2.5- to 4-
ounce model category.
Connectors: The connectors and the wire size
(gauge, which refers to diameter) are
important. You want to carry the current
involved and no more; using a connector that
is too large or a wire with too large a diameter
only adds weight to little airplanes that can’t
afford it.
The larger parking lot-size models can
properly use the popular Anderson Power
Pole-type connectors (also known as Sermos
connectors). You can use these from roughly
6 amps of current up.
The Deans four-pin connectors are popular
for 3 to 6 amps of current. It is a good idea to
gang two pins to make a single connection. In
that case, the four pins yields two conductors.
From 1.5- to 3-amp current, the JST red
plastic housing connector is fine. For less than
1.5 amps of current, the JST white plastic or
Cloud 9 RC Unisex connectors will do the
job.
EFlight Designs carries an excellent line of
submicroconnectors. Wire size can start with
16 gauge for the 8- to 10-amp current. As you
work your way down in current, the wire
gauge can go from 22 to 28, and even 32.
Your hobby supplier can recommend the best
size for each current level. The JST
connectors come with the wire already
attached.
Indoor Flying Tips: If you are already an RC
sport flier or a parking lot flier, you are
certainly qualified to fly indoors; but the
generally “restricted” airspace can be
extremely challenging at times. If you are
lucky enough to be able to fly a 4-ounce
model in an inflated dome, it is almost the
same as flying outdoors—no problem!
However, when you get down to a doubleor
even single-size gymnasium, you get the
feeling that you are always turning the
airplane; there isn’t enough space for
appreciable straightaway flight.
Inside a dome my aircraft have
occasionally hit walls or even the top dead
center of the ceiling. Being such lightweight
models, they seem to just bounce off these
soft surfaces. Most of the time I lose altitude
but can easily recover the airplane to normal
flight.
On the other hand, at the Toledo, Ohio,
PERF (Perrysburg Electric River Fliers)
indoor fly a couple years ago (when it was a
smaller facility), I “shot a basket” with my
little 4.7-ounce AIKA. We had to get a large
stepladder to remove the model from the
basketball hoop/net.
However, before you start worrying about
these possibilities, consider that at such light
weights and wing loadings, not much ever
happens to micromodels—except for midair
52 MODEL AVIATION
Since 1948 Fox Manufacturing
Company has been producing
high quality model airplane
engines, glow plugs and other
accessories. Fox has become a
name modelers can trust when
it comes to durability, power,
and performance at an
affordable price. (479) 646-1656
Fax (479) 646-1757
5305 Towson Avenue
Fort Smith, AR 72901
www.foxmanufacturing.com
email: [email protected]
07sig2.QXD 4/26/04 8:34 am Page 52
July 2004 55
collisions! They do occur every once in
awhile, but if you build your entire model
from a single sheet of balsa, it’s no big deal!
NIRAC: AMA encourages SIGs to help
organize the various groups within model
aviation. We are lucky to have the National
Indoor Remote-Control Aircraft Council
(NIRAC) represent indoor RC flying within
the Academy. National Indoor Electric
Duration record-holder Bob Wilder of Texas
founded the organization several years ago.
You can access the Web site containing all
of the general information about this SIG at
www.nirac.org. Look it up, get familiar with
the organization, and show your support by
joining.
Once a year NIRAC sponsors a major
indoor RC championship. The 2004 dates are
June 4-6, and the location, as in the past, will
be the big Oakland Yard Athletics facility (an
inflated dome) in Waterford, Michigan
(www.oaklandyard.com/model_aviation.htm).
The flying plan for the three days includes
official indoor RC events including Scale,
racing, cargo lift, Old-Timer climb-and-glide,
endurance, and RC gliders. Between the
events the dome will be opened up for funflying
by all who attend.
NIRAC can also help you find local domes
and large indoor flying facilities. The current
NIRAC president—Dave Robelen—is one of
the most experienced indoor/micro RC fliers.
With indoor RC growing extraordinarily
rapidly, there is much to be learned; new
technology seems to emerge almost weekly.
The big, annual NEAT (Northeast Electric
Aircraft Technology) Fair held in upstate New
York, near the town of Downsville, includes a
series of indoor RC lectures during the three
days of the event.
Sergio Sigras coordinates these seminars.
Some of the most important names in
microflight—Henry Pasquet, Gordon
Johnson, Matt Keennon, Nick Leichty, Fred
Marks, Clarence Hurd, Bob Selman, and
more—provide the latest indoor RC
information.
For the Saturday night of the Fair, Gordon
Johnson sets up an indoor RC flight
demonstration in a double-size gym at nearby
Walton Senior High School. Guest lecturers
get to show their stuff, to the delight of
hundreds of spectators. To learn more about
the Fair, visit www.neatfair.org.
When you are attempting to gain
permission to fly indoor RC at local school
facilities, offer to lecture and/or give classes at
the school to offset your using the venue.
“Yes, you can use our gym, but why not come
in and let our young people learn how they
can participate?”
References: NIRAC is a good starting point.
Several publications regularly offer many
articles about indoor RC. Air Age Media’s RC
MicroFlight is available in hard-copy form
and online. It has been in production for more
than three years. When you subscribe, you
obtain a password that allows you access to all
previously published articles. You can even
download plans from the construction articles.
MA has two talented authors who write
alternating bimonthly columns. Dave Robelen
writes “Micro-Flying” (featuring indoor RC
and parking lot flying) and Paul Bradley
writes “Small-Field Flying” (covering parking
lot flying and backyard flying, and hitting on
indoor RC). I highly recommend these.
You can count on Quiet Flyer, under the
direction of publisher Wil Byers, for many
indoor RC-oriented articles each month. This
magazine specializes in electric power and
sailplane activities.
Flying Models magazine also has
alternating columnists who spend considerable
time in the world of indoor RC: Don Belfort
and Stew Meyers. For many years, RC
Modeler magazine has featured Jim Zare, who
now concentrates most of his activities on
micro and indoor flying.
I hate to sound too commercial, but
roughly two years ago I wrote the book
Getting Started in Backyard Flying. It
contains a lot of material about indoor RC.
You will see how parking lot/backyard flyers
tend to complement the indoor RC flyer. This
book is available from AMA, Tower Hobbies,
Balsa Products, and the publisher’s Web site:
www.rcstore.com/rs/general/books.asp.
In the late 1960s, people such as Dave
Robelen, John Worth, and Howard McEntee
experimented with multichannel proportional
RC control of glow-fueled models that
07sig2.QXD 4/26/04 8:34 am Page 55
weighed only 5-8 ounces! Those airplanes and
their equipment were tedious to work with,
but they did fly.
Soon afterward, AMA Hall of Famer Bill
Cannon of Cannon Electronics produced a
subminiature RC system that made smallscale
RC-model flying practical for everyone.
Bill continued to make that equipment for
many years and should be congratulated for
his efforts and dedication to small-model RC
flying.
Recently we have been privileged to see
the development of micro RC systems, servos,
actuators, Li-Poly batteries, tiny motors, and a
growing group of dedicated RC modelers who
have been willing to make this endeavor
grow. With modern large inflatable domes,
field houses, etc., it is now possible to enjoy
RC flying during all kinds of weather, at any
time of day or night.
Want to have some more fun in RC? Try
flying indoors. MA
Bob Aberle
[email protected]
Manufacturers/distributors:
Firefly coreless micro motors—direct and
geared:
AstroFlight Inc.
www.astroflight.com
GWS motors, propellers, Li-Poly batteries:
Balsa Products
www.balsapr.com
Li-Poly batteries:
Batteries America
www.batteriesamerica.com
JMP receivers, magnetic actuators, Li-Poly
chargers:
Bob Selman Designs
http://users.joplin.com/~bselman/
Voltage cutoff programmable ESCs:
Castle Creations
www.castlecreations.com
Assortment of micro hardware and products:
Cloud 9 RC (John Worth)
(703) 273-0607
Hard-to-get gears, motors, propellers, wire,
connectors:
David Lewis
www.homefly.com
Profile Roadkill series stand-off scale models:
DJ Aerotech
www.djaerotech.com
RFFS-100 micro RC systems, magnetic
actuators, JMP receivers, four-channel
conversion RFFS-100s:
Dynamic Web Enterprises (DWE)
www.smallrc.com
Reduced-size receiver antennas:
E Cubed R/C
www.azarr.com
Magnetic actuators, control-linkage
accessories, connectors:
EFlight Designs
www.eflightdesigns.com
Li-Poly batteries, chargers:
E-Tec (Air Craft)
www.aircraft-world.com
M5 micro DC receivers, submicroservos,
Kokam Li-Poly batteries, chargers:
FMA Direct
www.fmadirect.com
Penta 2.4-gram receivers, GDservo 1.33-gram
servos, new proportional magnetic actuators:
Gasparin
56 MODEL AVIATION
www.gasparin.cz
Motors, propellers, wheels, accessories:
Grand Wing Servo-Tech (GWS)
www.gws.com.tw
Cirrus Micro Joule receivers, ESCs, 3-gram
servos:
Global Hobby Distributors
www.globalhobby.com
Triton Li-Poly chargers:
Great Planes Model Distributors
www.electrifly.com
www.greatplanes.com
HS-50 submicroservo:
Hitec RCD
www.hitecrcd.com
Cirrus Micro Joule receiver, ESC, 3-gram
servos:
Hobby Club
www.hobbyclub.com
Motors, JR radios, Hobby Zone ARF indoor
models, Thunder Power Li-Poly batteries:
Horizon Hobby (GWS)
www.horizonhobby.com
Assortment of tiny direct- and gear-drive
motors:
Kenway Motors
(908) 850-9571
GWS motors, propellers, Li-Poly batteries:
Maxx Products International
www.maxxprod.com
ARF and RTF indoor models:
Megatech
www.megatech.com
Li-Poly batteries, connectors, wire:
Radical RC
www.radicalrc.com
Berg receivers:
RC Direct
www.rc-direct.com
Tiny geared motors, scale model kits:
RCS Technik (Chris Stewart)
www.falconmodels.uk.com
Microreceivers, ESCs, Li-Poly batteries,
chargers, model kits:
Sky Hooks and Rigging
www.microrc.com
Li-Poly batteries:
Thunder Power (Advanced Energy
Technology Inc.)
(702) 228-8883
Indoor model kits and supplies:
Todd Long Models
www.toddsmodels.com
Li-Poly chargers, ARF and RTF model kits:
Tower Hobbies
www.towerhobbies.com
7865 Mill Road, Elkins Park, PA. 19027 USA
Tel. 215 635 6520 Orders ONLY 888 721 0128 Fax. 215 635 4951
Email [email protected] www.sonictronics.com.
NEW
McDaniel R/C A Division of Sonic-Tronics Inc.
Patents, copyrights
and trademarks are
applied.
The New “Go-Slo III” has been
improved with added features.
With the precise performance of
an 8 bit microprocessor the output
is now “user selectable”. Two models are available. One can
drive a single servo, two servos in tandem, two servos with one
reversed or all three servos at once. The other model drives one,
two or three servos in parallel. Both models allow the servo speed to be
adjusted, 2 to 10+ seconds of travel in either direction. Go-Slo III units
are great for precise operation of Flaps, Gear etc. The receiver cable is now a
heavy 22 gage for better power delivery to one, two or three servos.
Go-Slo III‘s are compatible with 4.8 or 6 Volt systems and all proportional servos.
The unit is 1.5” x 1.5”x 3/4” and only .9 oz in weight.
07sig2.QXD 4/26/04 8:34 am Page 56
Edition: Model Aviation - 2004/07
Page Numbers: 42,43,44,45,46,48,50,52,55,56
42 MODEL AVIATION
Introduction to
Indoor Radio Control
I WROTE A feature article published in last
month’s MA titled “Introduction to Parking
Lot Flying.” That category involves flying
relatively small, easy-to-build, and relatively
inexpensive RC models close in.
Aircraft in that size category (up to
roughly 16 ounces total weight) can also,
under certain circumstances, be flown in
indoor facilities. From a practical standpoint,
the larger parking lot-size models can be
flown easily and safely in extra-large indoor
facilities such as golf practice domes
(inflatable) and field houses used for football
practice.
Since winter weather hits many areas
of our country, indoor RC flying during
those months is increasing in popularity.
Not everyone has a golf dome or a field
house in his or her community, but almost
everyone has a school gymnasium or
auditorium that can be an excellent
substitute. To be able to use these smaller
indoor flying facilities, you have to
by Bob Aberle
Author’s original-design Kiwi weighs just 3.4 ounces with 100-
square-inch wing. It uses FMA Direct M5 receiver and two FMA
Direct PS-20 submicroservos. Battery power is two 145 mAh Li-
Poly cells.
Dynamic Web Enterprises proprietors Dan Hurd (L) and his dad
Clarence. Dan holds 1-ounce Pitts Special biplane; Clarence
holds his own-design Lil Skeeter.
Another Joe Wagner FF design from the early
1950s: the Dakota biplane. At right is originalsize
model powered by .049 glow engine. The
author built reduced-size version (left) which
weighs 1.3 ounces with 69 square inches of total
wing area. Power is single 145 mAh Li-Poly
battery. Construction article and plans were
published in May 2003 RC MicroFlight.
Author holds 3.8-ounce version of
popular Joe Wagner FF design—
The Sioux—from the early 1950s.
It has 90-square-inch wing and is
powered by GWS LPS/B2C-C
motor and two FMA Direct/Kokam
340 mAh HD Li-Poly cells. Will
soon be featured as construction
article in Quiet Flyer magazine.
The 2004 NIRAC Indoor Championships will be held
at the big Oakland Yard Athletics facility in Waterford MI.
Fun-flying will be permitted before contest rounds.
All are invited!
07sig2.QXD 4/26/04 8:23 am Page 42
July 2004 43
Pair of typical magnetic actuators. They have a moving magnet within a
coil. Exact separation between two coils and the fact that they are at right
angles to one another provide for control position centering.
Todd Long of Todd’s Models has been selling his Tiny for several years.
Depending on motor and battery choice, this excellent-flying design can
weigh approximately 4 ounces and provide considerable indoor RC funflying.
Don Stackhouse of DJ Aerotech holds two of his Roadkill-series
profile sport-scale models: an Me 109 (L) and a Ryan ST. Each
weighs roughly 3-3.5 ounces and operates on two Li-Poly
batteries.
Closer view of Clarence Hurd’s Lil Skeeter, which was
designed around DWE’s RFFS-100 micro RC system. It
has 46 square inches of wing area and weighs 23 grams
(.81 ounce) including single 130 mAh Li-Poly battery.
Motor is KP-00 geared at 2.67:1.
The Lightning RTF foam model was originally
intended to be an electric-powered FF. An
excellent conversion article by Greg Covey
detailing how to install the DWE RFFS-100 micro
radio system is on the DWE Web site.
DWE RFFS-100 micro RC system is extremely
popular. On this one, PC board weighing 1.8
grams is an RC receiver, ESC, and two magnetic
actuator drivers. It’s one of the best starting
points for flying RC models at or near 1-ounce
total weight.
Photos courtesy the author
07sig2.QXD 4/26/04 8:26 am Page 43
Let’s get into the details of these small, or as we call them, “microsize”
RC aircraft.
Micromodel Sizing: Micro-size models dedicated to indoor RC
flying can range from roughly 8 ounces total weight down to only a
few grams. For this presentation I’m concentrating on 4 ounces total
weight and less.
Right now the range of 4 ounces down to approximately 2.5
ounces can be enjoyed while employing the
available equipment technology, and at
relatively moderate prices. From 2.5 ounces
down to roughly .75 ounce, you will need one
of the several submicroservos on the market
or magnetic actuators. For less than .75 ounce
down to a few grams, you need highly
specialized equipment and considerable
model-building skills.
Typical 4-ounce models can have
approximately 80-120 square inches of wing
area, which will yield wing loadings in the
range of roughly 4-6 ounces/square foot. The
4-ounce total weight could consist of 2.25
ounces of equipment (receiver, two servos,
Li-Poly battery, motor, propeller, and motor
speed controller). The remaining 1.75 ounces
includes the model structure (including
covering, finish, wheels, hinges, and control
linkages).
This typical 4-ounce model can employ
traditional RC equipment, but it will be
smaller in size and weight. The servos will
consider reducing your RC model’s size and weight.
The subject of this presentation is flying RC indoors with models
that weigh less than 3 or 4 ounces. As I noted, there are certain
situations in which you can fly a parking lot model inside. There are
also times in which you can fly a 1-ounce RC model outdoors. To do
that, you need to seek out the dead-calm early-morning or -evening
air. Calm-air outdoor flying also lends itself well to backyard-type
flying, making it a perfect family hobby/sport!
44 MODEL AVIATION
Popular little KP-00 geared motor and companion 3-inch-diameter
propeller. Several sources sell this motor, as noted in text. Power
range is intended for .75- to roughly 1.5-ounce models!
Rear of FMA Direct M5 dual-conversion receiver, which is
smallest dual-conversion RC receiver on the market. It is
available on 72 MHz and six-meter RC channels. Weighs .35
ounce with case!
Basic RC system for 2.5- to 4-ounce model weight (L-R): Castle
Creations Pixie-7P ESC, FMA Direct M5 dual-conversion
microreceiver, two FMA Direct PS-20 submicroservos, two-cell
FMA Direct/Kokam 340 mAh HD Li-Poly battery pack.
Power, RC system needed to fly 1-ounce total-weight model.
Left: KP-00 geared motor, 3-inch-diameter propeller. Top center:
Pair of EFlight Designs magnetic actuators to operate rudder,
elevator. Top right: A 145 mAh Li-Poly battery cell. Just below
that is DWE RFFS-100 PC board containing receiver, ESC, two
magnetic actuator drivers. Lower right: Azarr’s E Cubed RC
reduced-size receiver antenna.
Cutaway of GWS LPS/B2C-C geared motor
mounted to 3⁄16-inch wood dowel. A
setscrew holds motor in place. Two
plywood formers support dowel. It’s
simple and effective! You can easily
change motor at flying site.
Dave Burley has been developing
microservos for indoor RC fliers’ benefit.
His latest (shown) is 1-gram proportional
feedback ultramicroservo. He demonstrated
it to many indoor RC experts at 2003 NEAT
Fair. Dave wants to interest a prominent
manufacturer to pick up on production
rights for it. It worked well, and he hopes it
can be produced at a reasonable unit price.
07sig2.QXD 4/26/04 8:28 am Page 44
July 2004 45
provide regular proportional control, operating from a conventional
RC transmitter.
I have a little indoor sport model that I’m flying at 74 square inches
of wing area and 1.2 ounces total weight. The wing loading works out
to only 2.3 ounces/square foot. It employs two magnetic actuators, and
a 145 mAh Li-Poly battery cell provides all the power. When flown
outdoors, this model doesn’t like any wind! I’ll get into the specifics of
the RC equipment later.
Safety: As is the case with parking lot flying, indoor RC flying has
certain safety issues about which you should be concerned. Even
though you are flying inside, radio signals can travel through buildings
easily without much attenuation of strength. Someone might be flying
right outside your indoor facility, so please check around first. It’s best
to check local hobby shops and RC clubs too.
Also safety related is your model’s speed in flight. An airplane
with less than 100 square inches of wing area and weighing
approximately 10 ounces might be capable of speeds in excess of 60-
75 mph. If it hits something or someone, it could cause physical or
property damage.
Common sense must prevail and reasonable weights and flying
speeds must be commensurate with the size of the facility. A leadertype
person should be in charge of each flying session. That person
must have the last word on who can or can’t fly, and his/her judgment
must be respected at all times!
Micromodel Design: I’ve already suggested weights and wing
loadings, and soon I will get into power systems. There aren’t many
ARF models in the less-than-4-ounce category; that might be
considered the bad news. The good news is that a 4-ounce airplane
can, for the most part, be constructed from scratch, with a minimum of
materials and a minimum of assembly time and skills. I’ve built 1-
ounce RC models from a single sheet of 1⁄32 x 3 x 36-inch balsa. That
is almost as inexpensive as you can go!
The 2- to 4-ounce models can often be built up from the many
rubber-powered kits on the hobby market. Doing this has become
popular. Another possibility are the profile semiscale models, such as
DJ Aerotech’s Roadkill series. Those are easy to build, inexpensive,
and are even supplied with the recommended motor.
If you want to try a 1-ounce model for the first time, the best
trainer is the Lil Skeeter designed by Clarence Hurd of Dynamic Web
Enterprises (DWE). This design was reviewed in the June 2002 RC
MicroFlight newsletter. Plans are available from DWE, and you
receive a free plans copy when you purchase the DWE RFFS-100
micro RC system.
A more ambitious project is Dave Robelen’s Walker, which he
Former AMA executive director and RC MicroFlight founding
editor John Worth holds Pee Wee Flyer made by Estes (the
rocket people). Wal-Mart stores throughout the country sell this
RTF for only $19.95. An article describing it was published in
the October 2003 RC MicroFlight.
Sky Hooks and Rigging owner Tom Mc Cann holds his little
Mosquito indoor slow flyer that Ken Coleman designed. It is
available from Tom as a kit. It spans 24 inches, has 131 square
inches of wing area, weighs 2.25 ounces, and flies on single Li-
Poly battery cell.
Micro-Pod is Bob’s latest original-design indoor RC model. A
construction article was published in November 2003 RC
MicroFlight. It weighs 1.2 ounces and has 74-square-inch wing
area. Power is geared KP-00 motor operating on single 145 mAh
Li-Poly cell.
calls an “ultralite indoor floater.” Dave went to the other extreme and
designed a 1-ounce model with an amazing 357 square inches of wing
area. The resulting wing loading works out to only .4 ounce/square
foot and provides flying speeds of just 3-4 mph. You can walk under
this model while it is flying. The Walker was featured in the July 2003
RC MicroFlight.
07sig2.QXD 4/26/04 8:30 am Page 45
Henry Pasquet is probably the most famous indoor RC flier. His
goal for years has been to build smaller and smaller models. He
holds his 4-inch-span Lacy M-10. It weighs 2.6 grams (total) with a
Gasparin G2.6 CO2 engine. RC system is by Nick Leichty. One No.
337 silver-oxide battery powers the system. It flies very well despite
its size!
US Airways Captain Joe Malinchak’s super-detailed Piper L-4
Grasshopper is military version of Piper Cub. Weighs 1.3 ounces
total including complete scale cockpit interior, landing-gear
shocks, etc. Has geared KP-00 for power! Joe earned DWE award at
2003 NIRAC Championships for RC Scale model with highest
points and weighing less than 1.5 ounces!
NIRAC president, MA columnist, and newly inducted Indoor RC Hall
of Fame member Dave Robelen holds his Scale 34-inch-span Piper
Vagabond. It has 200 square inches of wing area and weighs 4
ounces ready to fly. Power is a DC 5-2.4 coreless motor geared 7.5:1,
running on seven-cell 50 mAh battery pack.
Matt Keennon’s tiny electric-powered Scale P-38 twin spans only
10.5 inches and weighs 35 grams (1.23 ounces) with two M-20
motors and two Kokam 145 mAh Li-Poly cells in parallel. Flight
demos at NEAT Fair were spectacular. Matt makes a living
working on government-sponsored micromodel projects.
Nick Leichty, known for his ultramicro RC models, holds his
Micro Aero Master biplane at 2003 NEAT Fair. It employs one of
his micro three-channel RC systems powered by 4mm motor and
a 40 mAh Li-Poly battery. Model spans 5.5 inches and has 5.5-
gram (.19-ounce) total weight. Approximate flight time on a
charge is five minutes. The author saw the flights and couldn’t
believe it!
46 MODEL AVIATION
07sig2.QXD 4/26/04 8:32 am Page 46
Power Systems: Indoor power systems
primarily involve electric motors, be they
direct drive or gear driven. CO2 power
(compressed gas) is used to some extent, but
the ability to throttle these engines is still in
the experimental stages. Although some of
the tiny glow-fuel and diesel engines might
find their way into indoor RC flying, the
combination of noise and exhaust fumes
makes it somewhat impractical.
Small motors are becoming more and
more popular, and the prices keep going
down. This past year, Grand Wing Servo-
Tech (GWS)—a huge parking lot-/indoormodel
manufacturer—introduced a tiny
geared motor that it calls the “LPS” series.
One of the motors in this category—the
GWS/LPS/B2C—weighs only approximately
12 grams (.42 ounce). It is available in three
gear ratios (4:1, 5:1, 6.2:1).
I’m presently using the 6.2:1 geared
version, which operates on two Li-Poly
battery cells (nominal 7.4 volts) at 700 mA
motor current and 6-watt power level. Using a
GWS 6 x 5 propeller, I generate more than
enough thrust to fly a 4-ounce RC model.
These motors sell for roughly $10. How can
you go wrong?
The .75-1.5-ounce models are generally
powered by pager-derivative motors such as
the Knight & Pridham KP-00 (of which there
are several models with different windings),
with gearing ranging from 2.75:1 upward of
6:1. Each specific gear ratio requires a
different size propeller. Propeller diameters
range from 3 to 6 inches. The gearing choices
attempt to get the most thrust from the motor
while drawing the least current. This is the
game you must play with electric-powered
flight.
The little KP-00 motor will work well on
a single Li-Poly cell drawing roughly 700 mA
of current at approximately a 3-watt power
level. The trick with this is to be able to get an
RC system (receiver and servos) that can also
operate reliably from a single Li-Poly cell at
roughly 3.6 volts.
There are receivers that will do that,
especially those used in conjunction with
magnetic actuators. Bob Selman Designs
offers a new voltage-doubler unit that takes
the single cell voltage and increases it to
roughly 5 volts for more reliable RC
operation.
Many smaller motors are becoming
available for the indoor RC experimenter who
wants to keep reducing that total model
weight to as little as a few grams. Experts
such as Henry Pasquet and Nick Leichty are
regularly flying models weighing roughly .3
ounce! You can find tales of their
experimental efforts in RC MicroFlight. But
as I pointed out before, these truly micro RC
models require a great deal of experience and,
most of all, patience!
As this is being written, I have heard
about several micro manufacturers who have
prototype miniature brushless motors and
companion speed controllers in the works. A
lightweight, highly efficient brushless motor
will provide yet another breakthrough in
indoor RC.
Before leaving the power scene, I’ll
mention that there are CO2 motors now
available for RC model use. They are still
comparatively expensive, but a model’s
weight can be reduced even further than with
electric power because the CO2 tank weighs
less than a battery.
The biggest problem until recently has
been the ability to throttle these air-operated
motors. Stefan Gasparin in the Czech
Republic has made remarkable progress in
this regard. I urge you to look at his Web site.
ESCs: Even the electric motor speed
controllers have been shrunken to fit the
needs of our micro-size aircraft. I think it’s
safe to state that all of the micro ESCs have a
BEC, which allows for the sharing of the one
battery pack.
As you will soon learn, the new Li-Poly
battery technology requires that no cell drop
to less than 3.0 volts when in use. This is a
minimum discharge point. To be on the safe
side, a micro ESC’s low voltage cutoff point
should be set to increments of 3.0 volts per
cell. If you are using one Li-Poly cell, the
cutoff should be 3.0 volts. If your pack has
two Li-Poly cells the cutoff should be 6.0
volts, and so on.
Castle Creations’ Pixie-7P ESC allows
you to program the voltage cutoff point.
There aren’t that many choices, but they will
improve in time. Setting the voltage cutoff on
07sig2.QXD 4/26/04 8:33 am Page 48
the Pixie isn’t all that easy and does require
some patience, but this is the concept you
want to look for in the future!
Batteries: Until recently, the batteries of
choice for 4-ounce and lighter models were
the 100-125 mAh NiMH types, usually in
packs consisting of seven or eight cells. In the
past year we have been introduced to a new
form of battery known as the Li-Poly. These
new cells provide more capacity in a lighterweight
package. Both of those parameters are
exactly what you want for micro RC models.
Of equal interest is the fact that each Li-
Poly cell has a characteristic voltage of close
to 4.0; the older Ni-Cd/NiMH cells had only
1.2 volts per cell. So two Li-Poly cells work
like a six- or seven-cell Ni-Cd/NiMH pack.
We typically see two-cell packs consisting
of 145 mAh or 340 mAh powering 3- to 4-
ounce RC models. A two-cell 145 mAh Li-
Poly pack weighs 8.7 grams (.31 ounce) and
can fly that 3- to 4-ounce model at 700 mA
current (6 watts) for 10-12 minutes and more,
depending on how you throttle the motor in
flight. And two of the 340 mAh Li-Poly cells
(weighing 20.1 grams, or .71 ounce) could
provide up to 30 minutes of motor run time.
However, Li-Poly cells are still quite new
on the market, and they must be taken care of
very carefully. They require a special
dedicated charger and should not be charged
with more than a 1C current, which takes
roughly an hour. Li-Poly batteries should not
be discharged to less than 3.0 volts per cell.
Li-Poly cells are also currently somewhat
limited in their load capabilities. Initial
offerings could only provide loads up to
approximately 5C (five times the capacity of
the battery). Recently a new variety of Li-
Poly cell has been introduced that can stand
loads upward of 20C (quite an
improvement!).
Li-Poly batteries is a subject unto itself. I
wrote a comprehensive article titled
“Introduction to Lithium-Polymer Batteries”
that was published in the May 2004 MA. If
you haven’t read that piece, I highly
recommend that you do so before attempting
to use Li-Poly batteries in a model airplane of
any kind.
Micro RC System and Components: The RC
equipment is conventional technology, but is
obviously made smaller and lighter. An
inexpensive microreceiver is the GWS R-4P,
which has four-channel capability, is a singleconversion
circuit, and weighs 6.8 grams (.25
ounce). At approximately $30, it is a great
buy.
For those who want good range and
selectivity, in a crowded flying environment,
the FMA Direct M5 dual-conversion receiver
is an excellent choice, especially in the 2.5- to
4-ounce-model weight class. The M5 weighs
9.5 grams (.35 ounce).
Another outstanding choice is the Berg-
5*DSP at .35 ounce and the new Berg-4*DSP
Micro Stamp at just .25 ounce. The Berg
receivers are available from RC Direct. With
the Berg and FMA Direct receivers, you can
remove the receiver case for a further weight
reduction.
For the extra-small models (1.5 ounces
and lighter), the DWE RFFS-100 has been the
popular microsystem for some time. It is a
microreceiver, a built-in ESC with BEC, and
drivers for two magnetic actuators on a single
PC board. The entire board weighs only 1.8
grams (.06 ounce!).
The RFFS-100 receiver is not very
selective, so you can’t use several channels on
either side of your operating frequency when
flying. But this system has provided a load of
indoor RC fun-flying under the right
conditions.
Jean-Marie Piednoir (JMP) of France
makes a new and more selective
microreceiver which Bob Selman Designs
sells in the US. This receiver is claimed to be
extremely narrow band (selective!) and
includes an ESC and two magnetic actuator
drivers. It weighs 2.2 grams (.08 ounce), and
the price without connectors is $89. I’m sure
we will be seeing plenty of these units put
into indoor RC service in the near future.
As I was writing this, I learned of the new
Gasparin Penta 2.4-gram (.8-ounce) fourchannel
receiver, which is claimed to be
incredibly selective and will be selling in the
US at a reasonable $39.
In addition to receivers, servos or actuators
are also important. Conventional servos,
meaning regular proportional feedback
servos, are available at roughly 5.6 grams (.20
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07sig2.QXD 4/26/04 8:33 am Page 50
ounce). Two come to mind: the popular Hitec
HS-50 and the new FMA Direct PS-20. Each
sells for less than $30 and has been reliable.
The German WES-Technik company has
been making a linear-output-type microservo
for the past couple years. It weighs 2.1 grams
(.07 ounce) but is comparatively expensive at
$70-$80 (US).
Stefan Gasparin in conjunction with Didel
(the Swiss gear company) has designed a new
GDservo, which has a rotary output and
weighs 1.33 grams without a case. It will be
pricey, at $98 (US). Stefan also has a new
concept he calls a “Proportional Magnetic
Actuator.” I’ve seen some photos, and the
idea looks entirely realistic. Price is said to be
$39 each (US).
At the bottom of the weight scale are the
truly magnetic actuators; these are coil
devices with magnets that move inside the
coils. They require some patience to install
and offer little control force. That means your
hinges and control linkages must offer the
least possible friction. These magnetic
actuators make RC models of less than 1
ounce total weight possible. Good sources of
magnetic actuators include Bob Selman
Designs, Cloud-9 RC, E-Flight Design, and
DWE.
One last reference is to a “brick” design,
which was popular in the early 1970s. FMA
Direct is almost ready to release a microbrick
that will include one PC board, a narrow-band
receiver, ESC, control actuator drivers, and
two servos or two magnetic actuators. Placing
all of the components on a single board can
make certain installations impractical, but the
bottom line is that the brick eliminates a great
deal of wiring and connectors, thereby
reducing the overall weight. I believe this
concept will find a home in the 2.5- to 4-
ounce model category.
Connectors: The connectors and the wire size
(gauge, which refers to diameter) are
important. You want to carry the current
involved and no more; using a connector that
is too large or a wire with too large a diameter
only adds weight to little airplanes that can’t
afford it.
The larger parking lot-size models can
properly use the popular Anderson Power
Pole-type connectors (also known as Sermos
connectors). You can use these from roughly
6 amps of current up.
The Deans four-pin connectors are popular
for 3 to 6 amps of current. It is a good idea to
gang two pins to make a single connection. In
that case, the four pins yields two conductors.
From 1.5- to 3-amp current, the JST red
plastic housing connector is fine. For less than
1.5 amps of current, the JST white plastic or
Cloud 9 RC Unisex connectors will do the
job.
EFlight Designs carries an excellent line of
submicroconnectors. Wire size can start with
16 gauge for the 8- to 10-amp current. As you
work your way down in current, the wire
gauge can go from 22 to 28, and even 32.
Your hobby supplier can recommend the best
size for each current level. The JST
connectors come with the wire already
attached.
Indoor Flying Tips: If you are already an RC
sport flier or a parking lot flier, you are
certainly qualified to fly indoors; but the
generally “restricted” airspace can be
extremely challenging at times. If you are
lucky enough to be able to fly a 4-ounce
model in an inflated dome, it is almost the
same as flying outdoors—no problem!
However, when you get down to a doubleor
even single-size gymnasium, you get the
feeling that you are always turning the
airplane; there isn’t enough space for
appreciable straightaway flight.
Inside a dome my aircraft have
occasionally hit walls or even the top dead
center of the ceiling. Being such lightweight
models, they seem to just bounce off these
soft surfaces. Most of the time I lose altitude
but can easily recover the airplane to normal
flight.
On the other hand, at the Toledo, Ohio,
PERF (Perrysburg Electric River Fliers)
indoor fly a couple years ago (when it was a
smaller facility), I “shot a basket” with my
little 4.7-ounce AIKA. We had to get a large
stepladder to remove the model from the
basketball hoop/net.
However, before you start worrying about
these possibilities, consider that at such light
weights and wing loadings, not much ever
happens to micromodels—except for midair
52 MODEL AVIATION
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accessories. Fox has become a
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it comes to durability, power,
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affordable price. (479) 646-1656
Fax (479) 646-1757
5305 Towson Avenue
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www.foxmanufacturing.com
email: [email protected]
07sig2.QXD 4/26/04 8:34 am Page 52
July 2004 55
collisions! They do occur every once in
awhile, but if you build your entire model
from a single sheet of balsa, it’s no big deal!
NIRAC: AMA encourages SIGs to help
organize the various groups within model
aviation. We are lucky to have the National
Indoor Remote-Control Aircraft Council
(NIRAC) represent indoor RC flying within
the Academy. National Indoor Electric
Duration record-holder Bob Wilder of Texas
founded the organization several years ago.
You can access the Web site containing all
of the general information about this SIG at
www.nirac.org. Look it up, get familiar with
the organization, and show your support by
joining.
Once a year NIRAC sponsors a major
indoor RC championship. The 2004 dates are
June 4-6, and the location, as in the past, will
be the big Oakland Yard Athletics facility (an
inflated dome) in Waterford, Michigan
(www.oaklandyard.com/model_aviation.htm).
The flying plan for the three days includes
official indoor RC events including Scale,
racing, cargo lift, Old-Timer climb-and-glide,
endurance, and RC gliders. Between the
events the dome will be opened up for funflying
by all who attend.
NIRAC can also help you find local domes
and large indoor flying facilities. The current
NIRAC president—Dave Robelen—is one of
the most experienced indoor/micro RC fliers.
With indoor RC growing extraordinarily
rapidly, there is much to be learned; new
technology seems to emerge almost weekly.
The big, annual NEAT (Northeast Electric
Aircraft Technology) Fair held in upstate New
York, near the town of Downsville, includes a
series of indoor RC lectures during the three
days of the event.
Sergio Sigras coordinates these seminars.
Some of the most important names in
microflight—Henry Pasquet, Gordon
Johnson, Matt Keennon, Nick Leichty, Fred
Marks, Clarence Hurd, Bob Selman, and
more—provide the latest indoor RC
information.
For the Saturday night of the Fair, Gordon
Johnson sets up an indoor RC flight
demonstration in a double-size gym at nearby
Walton Senior High School. Guest lecturers
get to show their stuff, to the delight of
hundreds of spectators. To learn more about
the Fair, visit www.neatfair.org.
When you are attempting to gain
permission to fly indoor RC at local school
facilities, offer to lecture and/or give classes at
the school to offset your using the venue.
“Yes, you can use our gym, but why not come
in and let our young people learn how they
can participate?”
References: NIRAC is a good starting point.
Several publications regularly offer many
articles about indoor RC. Air Age Media’s RC
MicroFlight is available in hard-copy form
and online. It has been in production for more
than three years. When you subscribe, you
obtain a password that allows you access to all
previously published articles. You can even
download plans from the construction articles.
MA has two talented authors who write
alternating bimonthly columns. Dave Robelen
writes “Micro-Flying” (featuring indoor RC
and parking lot flying) and Paul Bradley
writes “Small-Field Flying” (covering parking
lot flying and backyard flying, and hitting on
indoor RC). I highly recommend these.
You can count on Quiet Flyer, under the
direction of publisher Wil Byers, for many
indoor RC-oriented articles each month. This
magazine specializes in electric power and
sailplane activities.
Flying Models magazine also has
alternating columnists who spend considerable
time in the world of indoor RC: Don Belfort
and Stew Meyers. For many years, RC
Modeler magazine has featured Jim Zare, who
now concentrates most of his activities on
micro and indoor flying.
I hate to sound too commercial, but
roughly two years ago I wrote the book
Getting Started in Backyard Flying. It
contains a lot of material about indoor RC.
You will see how parking lot/backyard flyers
tend to complement the indoor RC flyer. This
book is available from AMA, Tower Hobbies,
Balsa Products, and the publisher’s Web site:
www.rcstore.com/rs/general/books.asp.
In the late 1960s, people such as Dave
Robelen, John Worth, and Howard McEntee
experimented with multichannel proportional
RC control of glow-fueled models that
07sig2.QXD 4/26/04 8:34 am Page 55
weighed only 5-8 ounces! Those airplanes and
their equipment were tedious to work with,
but they did fly.
Soon afterward, AMA Hall of Famer Bill
Cannon of Cannon Electronics produced a
subminiature RC system that made smallscale
RC-model flying practical for everyone.
Bill continued to make that equipment for
many years and should be congratulated for
his efforts and dedication to small-model RC
flying.
Recently we have been privileged to see
the development of micro RC systems, servos,
actuators, Li-Poly batteries, tiny motors, and a
growing group of dedicated RC modelers who
have been willing to make this endeavor
grow. With modern large inflatable domes,
field houses, etc., it is now possible to enjoy
RC flying during all kinds of weather, at any
time of day or night.
Want to have some more fun in RC? Try
flying indoors. MA
Bob Aberle
[email protected]
Manufacturers/distributors:
Firefly coreless micro motors—direct and
geared:
AstroFlight Inc.
www.astroflight.com
GWS motors, propellers, Li-Poly batteries:
Balsa Products
www.balsapr.com
Li-Poly batteries:
Batteries America
www.batteriesamerica.com
JMP receivers, magnetic actuators, Li-Poly
chargers:
Bob Selman Designs
http://users.joplin.com/~bselman/
Voltage cutoff programmable ESCs:
Castle Creations
www.castlecreations.com
Assortment of micro hardware and products:
Cloud 9 RC (John Worth)
(703) 273-0607
Hard-to-get gears, motors, propellers, wire,
connectors:
David Lewis
www.homefly.com
Profile Roadkill series stand-off scale models:
DJ Aerotech
www.djaerotech.com
RFFS-100 micro RC systems, magnetic
actuators, JMP receivers, four-channel
conversion RFFS-100s:
Dynamic Web Enterprises (DWE)
www.smallrc.com
Reduced-size receiver antennas:
E Cubed R/C
www.azarr.com
Magnetic actuators, control-linkage
accessories, connectors:
EFlight Designs
www.eflightdesigns.com
Li-Poly batteries, chargers:
E-Tec (Air Craft)
www.aircraft-world.com
M5 micro DC receivers, submicroservos,
Kokam Li-Poly batteries, chargers:
FMA Direct
www.fmadirect.com
Penta 2.4-gram receivers, GDservo 1.33-gram
servos, new proportional magnetic actuators:
Gasparin
56 MODEL AVIATION
www.gasparin.cz
Motors, propellers, wheels, accessories:
Grand Wing Servo-Tech (GWS)
www.gws.com.tw
Cirrus Micro Joule receivers, ESCs, 3-gram
servos:
Global Hobby Distributors
www.globalhobby.com
Triton Li-Poly chargers:
Great Planes Model Distributors
www.electrifly.com
www.greatplanes.com
HS-50 submicroservo:
Hitec RCD
www.hitecrcd.com
Cirrus Micro Joule receiver, ESC, 3-gram
servos:
Hobby Club
www.hobbyclub.com
Motors, JR radios, Hobby Zone ARF indoor
models, Thunder Power Li-Poly batteries:
Horizon Hobby (GWS)
www.horizonhobby.com
Assortment of tiny direct- and gear-drive
motors:
Kenway Motors
(908) 850-9571
GWS motors, propellers, Li-Poly batteries:
Maxx Products International
www.maxxprod.com
ARF and RTF indoor models:
Megatech
www.megatech.com
Li-Poly batteries, connectors, wire:
Radical RC
www.radicalrc.com
Berg receivers:
RC Direct
www.rc-direct.com
Tiny geared motors, scale model kits:
RCS Technik (Chris Stewart)
www.falconmodels.uk.com
Microreceivers, ESCs, Li-Poly batteries,
chargers, model kits:
Sky Hooks and Rigging
www.microrc.com
Li-Poly batteries:
Thunder Power (Advanced Energy
Technology Inc.)
(702) 228-8883
Indoor model kits and supplies:
Todd Long Models
www.toddsmodels.com
Li-Poly chargers, ARF and RTF model kits:
Tower Hobbies
www.towerhobbies.com
7865 Mill Road, Elkins Park, PA. 19027 USA
Tel. 215 635 6520 Orders ONLY 888 721 0128 Fax. 215 635 4951
Email [email protected] www.sonictronics.com.
NEW
McDaniel R/C A Division of Sonic-Tronics Inc.
Patents, copyrights
and trademarks are
applied.
The New “Go-Slo III” has been
improved with added features.
With the precise performance of
an 8 bit microprocessor the output
is now “user selectable”. Two models are available. One can
drive a single servo, two servos in tandem, two servos with one
reversed or all three servos at once. The other model drives one,
two or three servos in parallel. Both models allow the servo speed to be
adjusted, 2 to 10+ seconds of travel in either direction. Go-Slo III units
are great for precise operation of Flaps, Gear etc. The receiver cable is now a
heavy 22 gage for better power delivery to one, two or three servos.
Go-Slo III‘s are compatible with 4.8 or 6 Volt systems and all proportional servos.
The unit is 1.5” x 1.5”x 3/4” and only .9 oz in weight.
07sig2.QXD 4/26/04 8:34 am Page 56
Edition: Model Aviation - 2004/07
Page Numbers: 42,43,44,45,46,48,50,52,55,56
42 MODEL AVIATION
Introduction to
Indoor Radio Control
I WROTE A feature article published in last
month’s MA titled “Introduction to Parking
Lot Flying.” That category involves flying
relatively small, easy-to-build, and relatively
inexpensive RC models close in.
Aircraft in that size category (up to
roughly 16 ounces total weight) can also,
under certain circumstances, be flown in
indoor facilities. From a practical standpoint,
the larger parking lot-size models can be
flown easily and safely in extra-large indoor
facilities such as golf practice domes
(inflatable) and field houses used for football
practice.
Since winter weather hits many areas
of our country, indoor RC flying during
those months is increasing in popularity.
Not everyone has a golf dome or a field
house in his or her community, but almost
everyone has a school gymnasium or
auditorium that can be an excellent
substitute. To be able to use these smaller
indoor flying facilities, you have to
by Bob Aberle
Author’s original-design Kiwi weighs just 3.4 ounces with 100-
square-inch wing. It uses FMA Direct M5 receiver and two FMA
Direct PS-20 submicroservos. Battery power is two 145 mAh Li-
Poly cells.
Dynamic Web Enterprises proprietors Dan Hurd (L) and his dad
Clarence. Dan holds 1-ounce Pitts Special biplane; Clarence
holds his own-design Lil Skeeter.
Another Joe Wagner FF design from the early
1950s: the Dakota biplane. At right is originalsize
model powered by .049 glow engine. The
author built reduced-size version (left) which
weighs 1.3 ounces with 69 square inches of total
wing area. Power is single 145 mAh Li-Poly
battery. Construction article and plans were
published in May 2003 RC MicroFlight.
Author holds 3.8-ounce version of
popular Joe Wagner FF design—
The Sioux—from the early 1950s.
It has 90-square-inch wing and is
powered by GWS LPS/B2C-C
motor and two FMA Direct/Kokam
340 mAh HD Li-Poly cells. Will
soon be featured as construction
article in Quiet Flyer magazine.
The 2004 NIRAC Indoor Championships will be held
at the big Oakland Yard Athletics facility in Waterford MI.
Fun-flying will be permitted before contest rounds.
All are invited!
07sig2.QXD 4/26/04 8:23 am Page 42
July 2004 43
Pair of typical magnetic actuators. They have a moving magnet within a
coil. Exact separation between two coils and the fact that they are at right
angles to one another provide for control position centering.
Todd Long of Todd’s Models has been selling his Tiny for several years.
Depending on motor and battery choice, this excellent-flying design can
weigh approximately 4 ounces and provide considerable indoor RC funflying.
Don Stackhouse of DJ Aerotech holds two of his Roadkill-series
profile sport-scale models: an Me 109 (L) and a Ryan ST. Each
weighs roughly 3-3.5 ounces and operates on two Li-Poly
batteries.
Closer view of Clarence Hurd’s Lil Skeeter, which was
designed around DWE’s RFFS-100 micro RC system. It
has 46 square inches of wing area and weighs 23 grams
(.81 ounce) including single 130 mAh Li-Poly battery.
Motor is KP-00 geared at 2.67:1.
The Lightning RTF foam model was originally
intended to be an electric-powered FF. An
excellent conversion article by Greg Covey
detailing how to install the DWE RFFS-100 micro
radio system is on the DWE Web site.
DWE RFFS-100 micro RC system is extremely
popular. On this one, PC board weighing 1.8
grams is an RC receiver, ESC, and two magnetic
actuator drivers. It’s one of the best starting
points for flying RC models at or near 1-ounce
total weight.
Photos courtesy the author
07sig2.QXD 4/26/04 8:26 am Page 43
Let’s get into the details of these small, or as we call them, “microsize”
RC aircraft.
Micromodel Sizing: Micro-size models dedicated to indoor RC
flying can range from roughly 8 ounces total weight down to only a
few grams. For this presentation I’m concentrating on 4 ounces total
weight and less.
Right now the range of 4 ounces down to approximately 2.5
ounces can be enjoyed while employing the
available equipment technology, and at
relatively moderate prices. From 2.5 ounces
down to roughly .75 ounce, you will need one
of the several submicroservos on the market
or magnetic actuators. For less than .75 ounce
down to a few grams, you need highly
specialized equipment and considerable
model-building skills.
Typical 4-ounce models can have
approximately 80-120 square inches of wing
area, which will yield wing loadings in the
range of roughly 4-6 ounces/square foot. The
4-ounce total weight could consist of 2.25
ounces of equipment (receiver, two servos,
Li-Poly battery, motor, propeller, and motor
speed controller). The remaining 1.75 ounces
includes the model structure (including
covering, finish, wheels, hinges, and control
linkages).
This typical 4-ounce model can employ
traditional RC equipment, but it will be
smaller in size and weight. The servos will
consider reducing your RC model’s size and weight.
The subject of this presentation is flying RC indoors with models
that weigh less than 3 or 4 ounces. As I noted, there are certain
situations in which you can fly a parking lot model inside. There are
also times in which you can fly a 1-ounce RC model outdoors. To do
that, you need to seek out the dead-calm early-morning or -evening
air. Calm-air outdoor flying also lends itself well to backyard-type
flying, making it a perfect family hobby/sport!
44 MODEL AVIATION
Popular little KP-00 geared motor and companion 3-inch-diameter
propeller. Several sources sell this motor, as noted in text. Power
range is intended for .75- to roughly 1.5-ounce models!
Rear of FMA Direct M5 dual-conversion receiver, which is
smallest dual-conversion RC receiver on the market. It is
available on 72 MHz and six-meter RC channels. Weighs .35
ounce with case!
Basic RC system for 2.5- to 4-ounce model weight (L-R): Castle
Creations Pixie-7P ESC, FMA Direct M5 dual-conversion
microreceiver, two FMA Direct PS-20 submicroservos, two-cell
FMA Direct/Kokam 340 mAh HD Li-Poly battery pack.
Power, RC system needed to fly 1-ounce total-weight model.
Left: KP-00 geared motor, 3-inch-diameter propeller. Top center:
Pair of EFlight Designs magnetic actuators to operate rudder,
elevator. Top right: A 145 mAh Li-Poly battery cell. Just below
that is DWE RFFS-100 PC board containing receiver, ESC, two
magnetic actuator drivers. Lower right: Azarr’s E Cubed RC
reduced-size receiver antenna.
Cutaway of GWS LPS/B2C-C geared motor
mounted to 3⁄16-inch wood dowel. A
setscrew holds motor in place. Two
plywood formers support dowel. It’s
simple and effective! You can easily
change motor at flying site.
Dave Burley has been developing
microservos for indoor RC fliers’ benefit.
His latest (shown) is 1-gram proportional
feedback ultramicroservo. He demonstrated
it to many indoor RC experts at 2003 NEAT
Fair. Dave wants to interest a prominent
manufacturer to pick up on production
rights for it. It worked well, and he hopes it
can be produced at a reasonable unit price.
07sig2.QXD 4/26/04 8:28 am Page 44
July 2004 45
provide regular proportional control, operating from a conventional
RC transmitter.
I have a little indoor sport model that I’m flying at 74 square inches
of wing area and 1.2 ounces total weight. The wing loading works out
to only 2.3 ounces/square foot. It employs two magnetic actuators, and
a 145 mAh Li-Poly battery cell provides all the power. When flown
outdoors, this model doesn’t like any wind! I’ll get into the specifics of
the RC equipment later.
Safety: As is the case with parking lot flying, indoor RC flying has
certain safety issues about which you should be concerned. Even
though you are flying inside, radio signals can travel through buildings
easily without much attenuation of strength. Someone might be flying
right outside your indoor facility, so please check around first. It’s best
to check local hobby shops and RC clubs too.
Also safety related is your model’s speed in flight. An airplane
with less than 100 square inches of wing area and weighing
approximately 10 ounces might be capable of speeds in excess of 60-
75 mph. If it hits something or someone, it could cause physical or
property damage.
Common sense must prevail and reasonable weights and flying
speeds must be commensurate with the size of the facility. A leadertype
person should be in charge of each flying session. That person
must have the last word on who can or can’t fly, and his/her judgment
must be respected at all times!
Micromodel Design: I’ve already suggested weights and wing
loadings, and soon I will get into power systems. There aren’t many
ARF models in the less-than-4-ounce category; that might be
considered the bad news. The good news is that a 4-ounce airplane
can, for the most part, be constructed from scratch, with a minimum of
materials and a minimum of assembly time and skills. I’ve built 1-
ounce RC models from a single sheet of 1⁄32 x 3 x 36-inch balsa. That
is almost as inexpensive as you can go!
The 2- to 4-ounce models can often be built up from the many
rubber-powered kits on the hobby market. Doing this has become
popular. Another possibility are the profile semiscale models, such as
DJ Aerotech’s Roadkill series. Those are easy to build, inexpensive,
and are even supplied with the recommended motor.
If you want to try a 1-ounce model for the first time, the best
trainer is the Lil Skeeter designed by Clarence Hurd of Dynamic Web
Enterprises (DWE). This design was reviewed in the June 2002 RC
MicroFlight newsletter. Plans are available from DWE, and you
receive a free plans copy when you purchase the DWE RFFS-100
micro RC system.
A more ambitious project is Dave Robelen’s Walker, which he
Former AMA executive director and RC MicroFlight founding
editor John Worth holds Pee Wee Flyer made by Estes (the
rocket people). Wal-Mart stores throughout the country sell this
RTF for only $19.95. An article describing it was published in
the October 2003 RC MicroFlight.
Sky Hooks and Rigging owner Tom Mc Cann holds his little
Mosquito indoor slow flyer that Ken Coleman designed. It is
available from Tom as a kit. It spans 24 inches, has 131 square
inches of wing area, weighs 2.25 ounces, and flies on single Li-
Poly battery cell.
Micro-Pod is Bob’s latest original-design indoor RC model. A
construction article was published in November 2003 RC
MicroFlight. It weighs 1.2 ounces and has 74-square-inch wing
area. Power is geared KP-00 motor operating on single 145 mAh
Li-Poly cell.
calls an “ultralite indoor floater.” Dave went to the other extreme and
designed a 1-ounce model with an amazing 357 square inches of wing
area. The resulting wing loading works out to only .4 ounce/square
foot and provides flying speeds of just 3-4 mph. You can walk under
this model while it is flying. The Walker was featured in the July 2003
RC MicroFlight.
07sig2.QXD 4/26/04 8:30 am Page 45
Henry Pasquet is probably the most famous indoor RC flier. His
goal for years has been to build smaller and smaller models. He
holds his 4-inch-span Lacy M-10. It weighs 2.6 grams (total) with a
Gasparin G2.6 CO2 engine. RC system is by Nick Leichty. One No.
337 silver-oxide battery powers the system. It flies very well despite
its size!
US Airways Captain Joe Malinchak’s super-detailed Piper L-4
Grasshopper is military version of Piper Cub. Weighs 1.3 ounces
total including complete scale cockpit interior, landing-gear
shocks, etc. Has geared KP-00 for power! Joe earned DWE award at
2003 NIRAC Championships for RC Scale model with highest
points and weighing less than 1.5 ounces!
NIRAC president, MA columnist, and newly inducted Indoor RC Hall
of Fame member Dave Robelen holds his Scale 34-inch-span Piper
Vagabond. It has 200 square inches of wing area and weighs 4
ounces ready to fly. Power is a DC 5-2.4 coreless motor geared 7.5:1,
running on seven-cell 50 mAh battery pack.
Matt Keennon’s tiny electric-powered Scale P-38 twin spans only
10.5 inches and weighs 35 grams (1.23 ounces) with two M-20
motors and two Kokam 145 mAh Li-Poly cells in parallel. Flight
demos at NEAT Fair were spectacular. Matt makes a living
working on government-sponsored micromodel projects.
Nick Leichty, known for his ultramicro RC models, holds his
Micro Aero Master biplane at 2003 NEAT Fair. It employs one of
his micro three-channel RC systems powered by 4mm motor and
a 40 mAh Li-Poly battery. Model spans 5.5 inches and has 5.5-
gram (.19-ounce) total weight. Approximate flight time on a
charge is five minutes. The author saw the flights and couldn’t
believe it!
46 MODEL AVIATION
07sig2.QXD 4/26/04 8:32 am Page 46
Power Systems: Indoor power systems
primarily involve electric motors, be they
direct drive or gear driven. CO2 power
(compressed gas) is used to some extent, but
the ability to throttle these engines is still in
the experimental stages. Although some of
the tiny glow-fuel and diesel engines might
find their way into indoor RC flying, the
combination of noise and exhaust fumes
makes it somewhat impractical.
Small motors are becoming more and
more popular, and the prices keep going
down. This past year, Grand Wing Servo-
Tech (GWS)—a huge parking lot-/indoormodel
manufacturer—introduced a tiny
geared motor that it calls the “LPS” series.
One of the motors in this category—the
GWS/LPS/B2C—weighs only approximately
12 grams (.42 ounce). It is available in three
gear ratios (4:1, 5:1, 6.2:1).
I’m presently using the 6.2:1 geared
version, which operates on two Li-Poly
battery cells (nominal 7.4 volts) at 700 mA
motor current and 6-watt power level. Using a
GWS 6 x 5 propeller, I generate more than
enough thrust to fly a 4-ounce RC model.
These motors sell for roughly $10. How can
you go wrong?
The .75-1.5-ounce models are generally
powered by pager-derivative motors such as
the Knight & Pridham KP-00 (of which there
are several models with different windings),
with gearing ranging from 2.75:1 upward of
6:1. Each specific gear ratio requires a
different size propeller. Propeller diameters
range from 3 to 6 inches. The gearing choices
attempt to get the most thrust from the motor
while drawing the least current. This is the
game you must play with electric-powered
flight.
The little KP-00 motor will work well on
a single Li-Poly cell drawing roughly 700 mA
of current at approximately a 3-watt power
level. The trick with this is to be able to get an
RC system (receiver and servos) that can also
operate reliably from a single Li-Poly cell at
roughly 3.6 volts.
There are receivers that will do that,
especially those used in conjunction with
magnetic actuators. Bob Selman Designs
offers a new voltage-doubler unit that takes
the single cell voltage and increases it to
roughly 5 volts for more reliable RC
operation.
Many smaller motors are becoming
available for the indoor RC experimenter who
wants to keep reducing that total model
weight to as little as a few grams. Experts
such as Henry Pasquet and Nick Leichty are
regularly flying models weighing roughly .3
ounce! You can find tales of their
experimental efforts in RC MicroFlight. But
as I pointed out before, these truly micro RC
models require a great deal of experience and,
most of all, patience!
As this is being written, I have heard
about several micro manufacturers who have
prototype miniature brushless motors and
companion speed controllers in the works. A
lightweight, highly efficient brushless motor
will provide yet another breakthrough in
indoor RC.
Before leaving the power scene, I’ll
mention that there are CO2 motors now
available for RC model use. They are still
comparatively expensive, but a model’s
weight can be reduced even further than with
electric power because the CO2 tank weighs
less than a battery.
The biggest problem until recently has
been the ability to throttle these air-operated
motors. Stefan Gasparin in the Czech
Republic has made remarkable progress in
this regard. I urge you to look at his Web site.
ESCs: Even the electric motor speed
controllers have been shrunken to fit the
needs of our micro-size aircraft. I think it’s
safe to state that all of the micro ESCs have a
BEC, which allows for the sharing of the one
battery pack.
As you will soon learn, the new Li-Poly
battery technology requires that no cell drop
to less than 3.0 volts when in use. This is a
minimum discharge point. To be on the safe
side, a micro ESC’s low voltage cutoff point
should be set to increments of 3.0 volts per
cell. If you are using one Li-Poly cell, the
cutoff should be 3.0 volts. If your pack has
two Li-Poly cells the cutoff should be 6.0
volts, and so on.
Castle Creations’ Pixie-7P ESC allows
you to program the voltage cutoff point.
There aren’t that many choices, but they will
improve in time. Setting the voltage cutoff on
07sig2.QXD 4/26/04 8:33 am Page 48
the Pixie isn’t all that easy and does require
some patience, but this is the concept you
want to look for in the future!
Batteries: Until recently, the batteries of
choice for 4-ounce and lighter models were
the 100-125 mAh NiMH types, usually in
packs consisting of seven or eight cells. In the
past year we have been introduced to a new
form of battery known as the Li-Poly. These
new cells provide more capacity in a lighterweight
package. Both of those parameters are
exactly what you want for micro RC models.
Of equal interest is the fact that each Li-
Poly cell has a characteristic voltage of close
to 4.0; the older Ni-Cd/NiMH cells had only
1.2 volts per cell. So two Li-Poly cells work
like a six- or seven-cell Ni-Cd/NiMH pack.
We typically see two-cell packs consisting
of 145 mAh or 340 mAh powering 3- to 4-
ounce RC models. A two-cell 145 mAh Li-
Poly pack weighs 8.7 grams (.31 ounce) and
can fly that 3- to 4-ounce model at 700 mA
current (6 watts) for 10-12 minutes and more,
depending on how you throttle the motor in
flight. And two of the 340 mAh Li-Poly cells
(weighing 20.1 grams, or .71 ounce) could
provide up to 30 minutes of motor run time.
However, Li-Poly cells are still quite new
on the market, and they must be taken care of
very carefully. They require a special
dedicated charger and should not be charged
with more than a 1C current, which takes
roughly an hour. Li-Poly batteries should not
be discharged to less than 3.0 volts per cell.
Li-Poly cells are also currently somewhat
limited in their load capabilities. Initial
offerings could only provide loads up to
approximately 5C (five times the capacity of
the battery). Recently a new variety of Li-
Poly cell has been introduced that can stand
loads upward of 20C (quite an
improvement!).
Li-Poly batteries is a subject unto itself. I
wrote a comprehensive article titled
“Introduction to Lithium-Polymer Batteries”
that was published in the May 2004 MA. If
you haven’t read that piece, I highly
recommend that you do so before attempting
to use Li-Poly batteries in a model airplane of
any kind.
Micro RC System and Components: The RC
equipment is conventional technology, but is
obviously made smaller and lighter. An
inexpensive microreceiver is the GWS R-4P,
which has four-channel capability, is a singleconversion
circuit, and weighs 6.8 grams (.25
ounce). At approximately $30, it is a great
buy.
For those who want good range and
selectivity, in a crowded flying environment,
the FMA Direct M5 dual-conversion receiver
is an excellent choice, especially in the 2.5- to
4-ounce-model weight class. The M5 weighs
9.5 grams (.35 ounce).
Another outstanding choice is the Berg-
5*DSP at .35 ounce and the new Berg-4*DSP
Micro Stamp at just .25 ounce. The Berg
receivers are available from RC Direct. With
the Berg and FMA Direct receivers, you can
remove the receiver case for a further weight
reduction.
For the extra-small models (1.5 ounces
and lighter), the DWE RFFS-100 has been the
popular microsystem for some time. It is a
microreceiver, a built-in ESC with BEC, and
drivers for two magnetic actuators on a single
PC board. The entire board weighs only 1.8
grams (.06 ounce!).
The RFFS-100 receiver is not very
selective, so you can’t use several channels on
either side of your operating frequency when
flying. But this system has provided a load of
indoor RC fun-flying under the right
conditions.
Jean-Marie Piednoir (JMP) of France
makes a new and more selective
microreceiver which Bob Selman Designs
sells in the US. This receiver is claimed to be
extremely narrow band (selective!) and
includes an ESC and two magnetic actuator
drivers. It weighs 2.2 grams (.08 ounce), and
the price without connectors is $89. I’m sure
we will be seeing plenty of these units put
into indoor RC service in the near future.
As I was writing this, I learned of the new
Gasparin Penta 2.4-gram (.8-ounce) fourchannel
receiver, which is claimed to be
incredibly selective and will be selling in the
US at a reasonable $39.
In addition to receivers, servos or actuators
are also important. Conventional servos,
meaning regular proportional feedback
servos, are available at roughly 5.6 grams (.20
Each of these fine Foam Fun Scale ARF airplane kits
include a “Plug & Fly” Speed 280 motor with Kavan K1
Gold Connectors, SPF Gearbox, APC prop, wheels, scale
decals, hardware, and illustrated instructions.
See your local hobby dealer or visit us at www.sigmfg.com.
Kavan RC is a subsidiary of SIG Manufacturing Company, Inc. • P.O. Box 520 • Montezuma, Iowa 50171-0520
Albatros D.V.
Item #KAV6527
Fine Electric Powered Slow/Park Flyers For The Pilot In The Know
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07sig2.QXD 4/26/04 8:33 am Page 50
ounce). Two come to mind: the popular Hitec
HS-50 and the new FMA Direct PS-20. Each
sells for less than $30 and has been reliable.
The German WES-Technik company has
been making a linear-output-type microservo
for the past couple years. It weighs 2.1 grams
(.07 ounce) but is comparatively expensive at
$70-$80 (US).
Stefan Gasparin in conjunction with Didel
(the Swiss gear company) has designed a new
GDservo, which has a rotary output and
weighs 1.33 grams without a case. It will be
pricey, at $98 (US). Stefan also has a new
concept he calls a “Proportional Magnetic
Actuator.” I’ve seen some photos, and the
idea looks entirely realistic. Price is said to be
$39 each (US).
At the bottom of the weight scale are the
truly magnetic actuators; these are coil
devices with magnets that move inside the
coils. They require some patience to install
and offer little control force. That means your
hinges and control linkages must offer the
least possible friction. These magnetic
actuators make RC models of less than 1
ounce total weight possible. Good sources of
magnetic actuators include Bob Selman
Designs, Cloud-9 RC, E-Flight Design, and
DWE.
One last reference is to a “brick” design,
which was popular in the early 1970s. FMA
Direct is almost ready to release a microbrick
that will include one PC board, a narrow-band
receiver, ESC, control actuator drivers, and
two servos or two magnetic actuators. Placing
all of the components on a single board can
make certain installations impractical, but the
bottom line is that the brick eliminates a great
deal of wiring and connectors, thereby
reducing the overall weight. I believe this
concept will find a home in the 2.5- to 4-
ounce model category.
Connectors: The connectors and the wire size
(gauge, which refers to diameter) are
important. You want to carry the current
involved and no more; using a connector that
is too large or a wire with too large a diameter
only adds weight to little airplanes that can’t
afford it.
The larger parking lot-size models can
properly use the popular Anderson Power
Pole-type connectors (also known as Sermos
connectors). You can use these from roughly
6 amps of current up.
The Deans four-pin connectors are popular
for 3 to 6 amps of current. It is a good idea to
gang two pins to make a single connection. In
that case, the four pins yields two conductors.
From 1.5- to 3-amp current, the JST red
plastic housing connector is fine. For less than
1.5 amps of current, the JST white plastic or
Cloud 9 RC Unisex connectors will do the
job.
EFlight Designs carries an excellent line of
submicroconnectors. Wire size can start with
16 gauge for the 8- to 10-amp current. As you
work your way down in current, the wire
gauge can go from 22 to 28, and even 32.
Your hobby supplier can recommend the best
size for each current level. The JST
connectors come with the wire already
attached.
Indoor Flying Tips: If you are already an RC
sport flier or a parking lot flier, you are
certainly qualified to fly indoors; but the
generally “restricted” airspace can be
extremely challenging at times. If you are
lucky enough to be able to fly a 4-ounce
model in an inflated dome, it is almost the
same as flying outdoors—no problem!
However, when you get down to a doubleor
even single-size gymnasium, you get the
feeling that you are always turning the
airplane; there isn’t enough space for
appreciable straightaway flight.
Inside a dome my aircraft have
occasionally hit walls or even the top dead
center of the ceiling. Being such lightweight
models, they seem to just bounce off these
soft surfaces. Most of the time I lose altitude
but can easily recover the airplane to normal
flight.
On the other hand, at the Toledo, Ohio,
PERF (Perrysburg Electric River Fliers)
indoor fly a couple years ago (when it was a
smaller facility), I “shot a basket” with my
little 4.7-ounce AIKA. We had to get a large
stepladder to remove the model from the
basketball hoop/net.
However, before you start worrying about
these possibilities, consider that at such light
weights and wing loadings, not much ever
happens to micromodels—except for midair
52 MODEL AVIATION
Since 1948 Fox Manufacturing
Company has been producing
high quality model airplane
engines, glow plugs and other
accessories. Fox has become a
name modelers can trust when
it comes to durability, power,
and performance at an
affordable price. (479) 646-1656
Fax (479) 646-1757
5305 Towson Avenue
Fort Smith, AR 72901
www.foxmanufacturing.com
email: [email protected]
07sig2.QXD 4/26/04 8:34 am Page 52
July 2004 55
collisions! They do occur every once in
awhile, but if you build your entire model
from a single sheet of balsa, it’s no big deal!
NIRAC: AMA encourages SIGs to help
organize the various groups within model
aviation. We are lucky to have the National
Indoor Remote-Control Aircraft Council
(NIRAC) represent indoor RC flying within
the Academy. National Indoor Electric
Duration record-holder Bob Wilder of Texas
founded the organization several years ago.
You can access the Web site containing all
of the general information about this SIG at
www.nirac.org. Look it up, get familiar with
the organization, and show your support by
joining.
Once a year NIRAC sponsors a major
indoor RC championship. The 2004 dates are
June 4-6, and the location, as in the past, will
be the big Oakland Yard Athletics facility (an
inflated dome) in Waterford, Michigan
(www.oaklandyard.com/model_aviation.htm).
The flying plan for the three days includes
official indoor RC events including Scale,
racing, cargo lift, Old-Timer climb-and-glide,
endurance, and RC gliders. Between the
events the dome will be opened up for funflying
by all who attend.
NIRAC can also help you find local domes
and large indoor flying facilities. The current
NIRAC president—Dave Robelen—is one of
the most experienced indoor/micro RC fliers.
With indoor RC growing extraordinarily
rapidly, there is much to be learned; new
technology seems to emerge almost weekly.
The big, annual NEAT (Northeast Electric
Aircraft Technology) Fair held in upstate New
York, near the town of Downsville, includes a
series of indoor RC lectures during the three
days of the event.
Sergio Sigras coordinates these seminars.
Some of the most important names in
microflight—Henry Pasquet, Gordon
Johnson, Matt Keennon, Nick Leichty, Fred
Marks, Clarence Hurd, Bob Selman, and
more—provide the latest indoor RC
information.
For the Saturday night of the Fair, Gordon
Johnson sets up an indoor RC flight
demonstration in a double-size gym at nearby
Walton Senior High School. Guest lecturers
get to show their stuff, to the delight of
hundreds of spectators. To learn more about
the Fair, visit www.neatfair.org.
When you are attempting to gain
permission to fly indoor RC at local school
facilities, offer to lecture and/or give classes at
the school to offset your using the venue.
“Yes, you can use our gym, but why not come
in and let our young people learn how they
can participate?”
References: NIRAC is a good starting point.
Several publications regularly offer many
articles about indoor RC. Air Age Media’s RC
MicroFlight is available in hard-copy form
and online. It has been in production for more
than three years. When you subscribe, you
obtain a password that allows you access to all
previously published articles. You can even
download plans from the construction articles.
MA has two talented authors who write
alternating bimonthly columns. Dave Robelen
writes “Micro-Flying” (featuring indoor RC
and parking lot flying) and Paul Bradley
writes “Small-Field Flying” (covering parking
lot flying and backyard flying, and hitting on
indoor RC). I highly recommend these.
You can count on Quiet Flyer, under the
direction of publisher Wil Byers, for many
indoor RC-oriented articles each month. This
magazine specializes in electric power and
sailplane activities.
Flying Models magazine also has
alternating columnists who spend considerable
time in the world of indoor RC: Don Belfort
and Stew Meyers. For many years, RC
Modeler magazine has featured Jim Zare, who
now concentrates most of his activities on
micro and indoor flying.
I hate to sound too commercial, but
roughly two years ago I wrote the book
Getting Started in Backyard Flying. It
contains a lot of material about indoor RC.
You will see how parking lot/backyard flyers
tend to complement the indoor RC flyer. This
book is available from AMA, Tower Hobbies,
Balsa Products, and the publisher’s Web site:
www.rcstore.com/rs/general/books.asp.
In the late 1960s, people such as Dave
Robelen, John Worth, and Howard McEntee
experimented with multichannel proportional
RC control of glow-fueled models that
07sig2.QXD 4/26/04 8:34 am Page 55
weighed only 5-8 ounces! Those airplanes and
their equipment were tedious to work with,
but they did fly.
Soon afterward, AMA Hall of Famer Bill
Cannon of Cannon Electronics produced a
subminiature RC system that made smallscale
RC-model flying practical for everyone.
Bill continued to make that equipment for
many years and should be congratulated for
his efforts and dedication to small-model RC
flying.
Recently we have been privileged to see
the development of micro RC systems, servos,
actuators, Li-Poly batteries, tiny motors, and a
growing group of dedicated RC modelers who
have been willing to make this endeavor
grow. With modern large inflatable domes,
field houses, etc., it is now possible to enjoy
RC flying during all kinds of weather, at any
time of day or night.
Want to have some more fun in RC? Try
flying indoors. MA
Bob Aberle
[email protected]
Manufacturers/distributors:
Firefly coreless micro motors—direct and
geared:
AstroFlight Inc.
www.astroflight.com
GWS motors, propellers, Li-Poly batteries:
Balsa Products
www.balsapr.com
Li-Poly batteries:
Batteries America
www.batteriesamerica.com
JMP receivers, magnetic actuators, Li-Poly
chargers:
Bob Selman Designs
http://users.joplin.com/~bselman/
Voltage cutoff programmable ESCs:
Castle Creations
www.castlecreations.com
Assortment of micro hardware and products:
Cloud 9 RC (John Worth)
(703) 273-0607
Hard-to-get gears, motors, propellers, wire,
connectors:
David Lewis
www.homefly.com
Profile Roadkill series stand-off scale models:
DJ Aerotech
www.djaerotech.com
RFFS-100 micro RC systems, magnetic
actuators, JMP receivers, four-channel
conversion RFFS-100s:
Dynamic Web Enterprises (DWE)
www.smallrc.com
Reduced-size receiver antennas:
E Cubed R/C
www.azarr.com
Magnetic actuators, control-linkage
accessories, connectors:
EFlight Designs
www.eflightdesigns.com
Li-Poly batteries, chargers:
E-Tec (Air Craft)
www.aircraft-world.com
M5 micro DC receivers, submicroservos,
Kokam Li-Poly batteries, chargers:
FMA Direct
www.fmadirect.com
Penta 2.4-gram receivers, GDservo 1.33-gram
servos, new proportional magnetic actuators:
Gasparin
56 MODEL AVIATION
www.gasparin.cz
Motors, propellers, wheels, accessories:
Grand Wing Servo-Tech (GWS)
www.gws.com.tw
Cirrus Micro Joule receivers, ESCs, 3-gram
servos:
Global Hobby Distributors
www.globalhobby.com
Triton Li-Poly chargers:
Great Planes Model Distributors
www.electrifly.com
www.greatplanes.com
HS-50 submicroservo:
Hitec RCD
www.hitecrcd.com
Cirrus Micro Joule receiver, ESC, 3-gram
servos:
Hobby Club
www.hobbyclub.com
Motors, JR radios, Hobby Zone ARF indoor
models, Thunder Power Li-Poly batteries:
Horizon Hobby (GWS)
www.horizonhobby.com
Assortment of tiny direct- and gear-drive
motors:
Kenway Motors
(908) 850-9571
GWS motors, propellers, Li-Poly batteries:
Maxx Products International
www.maxxprod.com
ARF and RTF indoor models:
Megatech
www.megatech.com
Li-Poly batteries, connectors, wire:
Radical RC
www.radicalrc.com
Berg receivers:
RC Direct
www.rc-direct.com
Tiny geared motors, scale model kits:
RCS Technik (Chris Stewart)
www.falconmodels.uk.com
Microreceivers, ESCs, Li-Poly batteries,
chargers, model kits:
Sky Hooks and Rigging
www.microrc.com
Li-Poly batteries:
Thunder Power (Advanced Energy
Technology Inc.)
(702) 228-8883
Indoor model kits and supplies:
Todd Long Models
www.toddsmodels.com
Li-Poly chargers, ARF and RTF model kits:
Tower Hobbies
www.towerhobbies.com
7865 Mill Road, Elkins Park, PA. 19027 USA
Tel. 215 635 6520 Orders ONLY 888 721 0128 Fax. 215 635 4951
Email [email protected] www.sonictronics.com.
NEW
McDaniel R/C A Division of Sonic-Tronics Inc.
Patents, copyrights
and trademarks are
applied.
The New “Go-Slo III” has been
improved with added features.
With the precise performance of
an 8 bit microprocessor the output
is now “user selectable”. Two models are available. One can
drive a single servo, two servos in tandem, two servos with one
reversed or all three servos at once. The other model drives one,
two or three servos in parallel. Both models allow the servo speed to be
adjusted, 2 to 10+ seconds of travel in either direction. Go-Slo III units
are great for precise operation of Flaps, Gear etc. The receiver cable is now a
heavy 22 gage for better power delivery to one, two or three servos.
Go-Slo III‘s are compatible with 4.8 or 6 Volt systems and all proportional servos.
The unit is 1.5” x 1.5”x 3/4” and only .9 oz in weight.
07sig2.QXD 4/26/04 8:34 am Page 56
Edition: Model Aviation - 2004/07
Page Numbers: 42,43,44,45,46,48,50,52,55,56
42 MODEL AVIATION
Introduction to
Indoor Radio Control
I WROTE A feature article published in last
month’s MA titled “Introduction to Parking
Lot Flying.” That category involves flying
relatively small, easy-to-build, and relatively
inexpensive RC models close in.
Aircraft in that size category (up to
roughly 16 ounces total weight) can also,
under certain circumstances, be flown in
indoor facilities. From a practical standpoint,
the larger parking lot-size models can be
flown easily and safely in extra-large indoor
facilities such as golf practice domes
(inflatable) and field houses used for football
practice.
Since winter weather hits many areas
of our country, indoor RC flying during
those months is increasing in popularity.
Not everyone has a golf dome or a field
house in his or her community, but almost
everyone has a school gymnasium or
auditorium that can be an excellent
substitute. To be able to use these smaller
indoor flying facilities, you have to
by Bob Aberle
Author’s original-design Kiwi weighs just 3.4 ounces with 100-
square-inch wing. It uses FMA Direct M5 receiver and two FMA
Direct PS-20 submicroservos. Battery power is two 145 mAh Li-
Poly cells.
Dynamic Web Enterprises proprietors Dan Hurd (L) and his dad
Clarence. Dan holds 1-ounce Pitts Special biplane; Clarence
holds his own-design Lil Skeeter.
Another Joe Wagner FF design from the early
1950s: the Dakota biplane. At right is originalsize
model powered by .049 glow engine. The
author built reduced-size version (left) which
weighs 1.3 ounces with 69 square inches of total
wing area. Power is single 145 mAh Li-Poly
battery. Construction article and plans were
published in May 2003 RC MicroFlight.
Author holds 3.8-ounce version of
popular Joe Wagner FF design—
The Sioux—from the early 1950s.
It has 90-square-inch wing and is
powered by GWS LPS/B2C-C
motor and two FMA Direct/Kokam
340 mAh HD Li-Poly cells. Will
soon be featured as construction
article in Quiet Flyer magazine.
The 2004 NIRAC Indoor Championships will be held
at the big Oakland Yard Athletics facility in Waterford MI.
Fun-flying will be permitted before contest rounds.
All are invited!
07sig2.QXD 4/26/04 8:23 am Page 42
July 2004 43
Pair of typical magnetic actuators. They have a moving magnet within a
coil. Exact separation between two coils and the fact that they are at right
angles to one another provide for control position centering.
Todd Long of Todd’s Models has been selling his Tiny for several years.
Depending on motor and battery choice, this excellent-flying design can
weigh approximately 4 ounces and provide considerable indoor RC funflying.
Don Stackhouse of DJ Aerotech holds two of his Roadkill-series
profile sport-scale models: an Me 109 (L) and a Ryan ST. Each
weighs roughly 3-3.5 ounces and operates on two Li-Poly
batteries.
Closer view of Clarence Hurd’s Lil Skeeter, which was
designed around DWE’s RFFS-100 micro RC system. It
has 46 square inches of wing area and weighs 23 grams
(.81 ounce) including single 130 mAh Li-Poly battery.
Motor is KP-00 geared at 2.67:1.
The Lightning RTF foam model was originally
intended to be an electric-powered FF. An
excellent conversion article by Greg Covey
detailing how to install the DWE RFFS-100 micro
radio system is on the DWE Web site.
DWE RFFS-100 micro RC system is extremely
popular. On this one, PC board weighing 1.8
grams is an RC receiver, ESC, and two magnetic
actuator drivers. It’s one of the best starting
points for flying RC models at or near 1-ounce
total weight.
Photos courtesy the author
07sig2.QXD 4/26/04 8:26 am Page 43
Let’s get into the details of these small, or as we call them, “microsize”
RC aircraft.
Micromodel Sizing: Micro-size models dedicated to indoor RC
flying can range from roughly 8 ounces total weight down to only a
few grams. For this presentation I’m concentrating on 4 ounces total
weight and less.
Right now the range of 4 ounces down to approximately 2.5
ounces can be enjoyed while employing the
available equipment technology, and at
relatively moderate prices. From 2.5 ounces
down to roughly .75 ounce, you will need one
of the several submicroservos on the market
or magnetic actuators. For less than .75 ounce
down to a few grams, you need highly
specialized equipment and considerable
model-building skills.
Typical 4-ounce models can have
approximately 80-120 square inches of wing
area, which will yield wing loadings in the
range of roughly 4-6 ounces/square foot. The
4-ounce total weight could consist of 2.25
ounces of equipment (receiver, two servos,
Li-Poly battery, motor, propeller, and motor
speed controller). The remaining 1.75 ounces
includes the model structure (including
covering, finish, wheels, hinges, and control
linkages).
This typical 4-ounce model can employ
traditional RC equipment, but it will be
smaller in size and weight. The servos will
consider reducing your RC model’s size and weight.
The subject of this presentation is flying RC indoors with models
that weigh less than 3 or 4 ounces. As I noted, there are certain
situations in which you can fly a parking lot model inside. There are
also times in which you can fly a 1-ounce RC model outdoors. To do
that, you need to seek out the dead-calm early-morning or -evening
air. Calm-air outdoor flying also lends itself well to backyard-type
flying, making it a perfect family hobby/sport!
44 MODEL AVIATION
Popular little KP-00 geared motor and companion 3-inch-diameter
propeller. Several sources sell this motor, as noted in text. Power
range is intended for .75- to roughly 1.5-ounce models!
Rear of FMA Direct M5 dual-conversion receiver, which is
smallest dual-conversion RC receiver on the market. It is
available on 72 MHz and six-meter RC channels. Weighs .35
ounce with case!
Basic RC system for 2.5- to 4-ounce model weight (L-R): Castle
Creations Pixie-7P ESC, FMA Direct M5 dual-conversion
microreceiver, two FMA Direct PS-20 submicroservos, two-cell
FMA Direct/Kokam 340 mAh HD Li-Poly battery pack.
Power, RC system needed to fly 1-ounce total-weight model.
Left: KP-00 geared motor, 3-inch-diameter propeller. Top center:
Pair of EFlight Designs magnetic actuators to operate rudder,
elevator. Top right: A 145 mAh Li-Poly battery cell. Just below
that is DWE RFFS-100 PC board containing receiver, ESC, two
magnetic actuator drivers. Lower right: Azarr’s E Cubed RC
reduced-size receiver antenna.
Cutaway of GWS LPS/B2C-C geared motor
mounted to 3⁄16-inch wood dowel. A
setscrew holds motor in place. Two
plywood formers support dowel. It’s
simple and effective! You can easily
change motor at flying site.
Dave Burley has been developing
microservos for indoor RC fliers’ benefit.
His latest (shown) is 1-gram proportional
feedback ultramicroservo. He demonstrated
it to many indoor RC experts at 2003 NEAT
Fair. Dave wants to interest a prominent
manufacturer to pick up on production
rights for it. It worked well, and he hopes it
can be produced at a reasonable unit price.
07sig2.QXD 4/26/04 8:28 am Page 44
July 2004 45
provide regular proportional control, operating from a conventional
RC transmitter.
I have a little indoor sport model that I’m flying at 74 square inches
of wing area and 1.2 ounces total weight. The wing loading works out
to only 2.3 ounces/square foot. It employs two magnetic actuators, and
a 145 mAh Li-Poly battery cell provides all the power. When flown
outdoors, this model doesn’t like any wind! I’ll get into the specifics of
the RC equipment later.
Safety: As is the case with parking lot flying, indoor RC flying has
certain safety issues about which you should be concerned. Even
though you are flying inside, radio signals can travel through buildings
easily without much attenuation of strength. Someone might be flying
right outside your indoor facility, so please check around first. It’s best
to check local hobby shops and RC clubs too.
Also safety related is your model’s speed in flight. An airplane
with less than 100 square inches of wing area and weighing
approximately 10 ounces might be capable of speeds in excess of 60-
75 mph. If it hits something or someone, it could cause physical or
property damage.
Common sense must prevail and reasonable weights and flying
speeds must be commensurate with the size of the facility. A leadertype
person should be in charge of each flying session. That person
must have the last word on who can or can’t fly, and his/her judgment
must be respected at all times!
Micromodel Design: I’ve already suggested weights and wing
loadings, and soon I will get into power systems. There aren’t many
ARF models in the less-than-4-ounce category; that might be
considered the bad news. The good news is that a 4-ounce airplane
can, for the most part, be constructed from scratch, with a minimum of
materials and a minimum of assembly time and skills. I’ve built 1-
ounce RC models from a single sheet of 1⁄32 x 3 x 36-inch balsa. That
is almost as inexpensive as you can go!
The 2- to 4-ounce models can often be built up from the many
rubber-powered kits on the hobby market. Doing this has become
popular. Another possibility are the profile semiscale models, such as
DJ Aerotech’s Roadkill series. Those are easy to build, inexpensive,
and are even supplied with the recommended motor.
If you want to try a 1-ounce model for the first time, the best
trainer is the Lil Skeeter designed by Clarence Hurd of Dynamic Web
Enterprises (DWE). This design was reviewed in the June 2002 RC
MicroFlight newsletter. Plans are available from DWE, and you
receive a free plans copy when you purchase the DWE RFFS-100
micro RC system.
A more ambitious project is Dave Robelen’s Walker, which he
Former AMA executive director and RC MicroFlight founding
editor John Worth holds Pee Wee Flyer made by Estes (the
rocket people). Wal-Mart stores throughout the country sell this
RTF for only $19.95. An article describing it was published in
the October 2003 RC MicroFlight.
Sky Hooks and Rigging owner Tom Mc Cann holds his little
Mosquito indoor slow flyer that Ken Coleman designed. It is
available from Tom as a kit. It spans 24 inches, has 131 square
inches of wing area, weighs 2.25 ounces, and flies on single Li-
Poly battery cell.
Micro-Pod is Bob’s latest original-design indoor RC model. A
construction article was published in November 2003 RC
MicroFlight. It weighs 1.2 ounces and has 74-square-inch wing
area. Power is geared KP-00 motor operating on single 145 mAh
Li-Poly cell.
calls an “ultralite indoor floater.” Dave went to the other extreme and
designed a 1-ounce model with an amazing 357 square inches of wing
area. The resulting wing loading works out to only .4 ounce/square
foot and provides flying speeds of just 3-4 mph. You can walk under
this model while it is flying. The Walker was featured in the July 2003
RC MicroFlight.
07sig2.QXD 4/26/04 8:30 am Page 45
Henry Pasquet is probably the most famous indoor RC flier. His
goal for years has been to build smaller and smaller models. He
holds his 4-inch-span Lacy M-10. It weighs 2.6 grams (total) with a
Gasparin G2.6 CO2 engine. RC system is by Nick Leichty. One No.
337 silver-oxide battery powers the system. It flies very well despite
its size!
US Airways Captain Joe Malinchak’s super-detailed Piper L-4
Grasshopper is military version of Piper Cub. Weighs 1.3 ounces
total including complete scale cockpit interior, landing-gear
shocks, etc. Has geared KP-00 for power! Joe earned DWE award at
2003 NIRAC Championships for RC Scale model with highest
points and weighing less than 1.5 ounces!
NIRAC president, MA columnist, and newly inducted Indoor RC Hall
of Fame member Dave Robelen holds his Scale 34-inch-span Piper
Vagabond. It has 200 square inches of wing area and weighs 4
ounces ready to fly. Power is a DC 5-2.4 coreless motor geared 7.5:1,
running on seven-cell 50 mAh battery pack.
Matt Keennon’s tiny electric-powered Scale P-38 twin spans only
10.5 inches and weighs 35 grams (1.23 ounces) with two M-20
motors and two Kokam 145 mAh Li-Poly cells in parallel. Flight
demos at NEAT Fair were spectacular. Matt makes a living
working on government-sponsored micromodel projects.
Nick Leichty, known for his ultramicro RC models, holds his
Micro Aero Master biplane at 2003 NEAT Fair. It employs one of
his micro three-channel RC systems powered by 4mm motor and
a 40 mAh Li-Poly battery. Model spans 5.5 inches and has 5.5-
gram (.19-ounce) total weight. Approximate flight time on a
charge is five minutes. The author saw the flights and couldn’t
believe it!
46 MODEL AVIATION
07sig2.QXD 4/26/04 8:32 am Page 46
Power Systems: Indoor power systems
primarily involve electric motors, be they
direct drive or gear driven. CO2 power
(compressed gas) is used to some extent, but
the ability to throttle these engines is still in
the experimental stages. Although some of
the tiny glow-fuel and diesel engines might
find their way into indoor RC flying, the
combination of noise and exhaust fumes
makes it somewhat impractical.
Small motors are becoming more and
more popular, and the prices keep going
down. This past year, Grand Wing Servo-
Tech (GWS)—a huge parking lot-/indoormodel
manufacturer—introduced a tiny
geared motor that it calls the “LPS” series.
One of the motors in this category—the
GWS/LPS/B2C—weighs only approximately
12 grams (.42 ounce). It is available in three
gear ratios (4:1, 5:1, 6.2:1).
I’m presently using the 6.2:1 geared
version, which operates on two Li-Poly
battery cells (nominal 7.4 volts) at 700 mA
motor current and 6-watt power level. Using a
GWS 6 x 5 propeller, I generate more than
enough thrust to fly a 4-ounce RC model.
These motors sell for roughly $10. How can
you go wrong?
The .75-1.5-ounce models are generally
powered by pager-derivative motors such as
the Knight & Pridham KP-00 (of which there
are several models with different windings),
with gearing ranging from 2.75:1 upward of
6:1. Each specific gear ratio requires a
different size propeller. Propeller diameters
range from 3 to 6 inches. The gearing choices
attempt to get the most thrust from the motor
while drawing the least current. This is the
game you must play with electric-powered
flight.
The little KP-00 motor will work well on
a single Li-Poly cell drawing roughly 700 mA
of current at approximately a 3-watt power
level. The trick with this is to be able to get an
RC system (receiver and servos) that can also
operate reliably from a single Li-Poly cell at
roughly 3.6 volts.
There are receivers that will do that,
especially those used in conjunction with
magnetic actuators. Bob Selman Designs
offers a new voltage-doubler unit that takes
the single cell voltage and increases it to
roughly 5 volts for more reliable RC
operation.
Many smaller motors are becoming
available for the indoor RC experimenter who
wants to keep reducing that total model
weight to as little as a few grams. Experts
such as Henry Pasquet and Nick Leichty are
regularly flying models weighing roughly .3
ounce! You can find tales of their
experimental efforts in RC MicroFlight. But
as I pointed out before, these truly micro RC
models require a great deal of experience and,
most of all, patience!
As this is being written, I have heard
about several micro manufacturers who have
prototype miniature brushless motors and
companion speed controllers in the works. A
lightweight, highly efficient brushless motor
will provide yet another breakthrough in
indoor RC.
Before leaving the power scene, I’ll
mention that there are CO2 motors now
available for RC model use. They are still
comparatively expensive, but a model’s
weight can be reduced even further than with
electric power because the CO2 tank weighs
less than a battery.
The biggest problem until recently has
been the ability to throttle these air-operated
motors. Stefan Gasparin in the Czech
Republic has made remarkable progress in
this regard. I urge you to look at his Web site.
ESCs: Even the electric motor speed
controllers have been shrunken to fit the
needs of our micro-size aircraft. I think it’s
safe to state that all of the micro ESCs have a
BEC, which allows for the sharing of the one
battery pack.
As you will soon learn, the new Li-Poly
battery technology requires that no cell drop
to less than 3.0 volts when in use. This is a
minimum discharge point. To be on the safe
side, a micro ESC’s low voltage cutoff point
should be set to increments of 3.0 volts per
cell. If you are using one Li-Poly cell, the
cutoff should be 3.0 volts. If your pack has
two Li-Poly cells the cutoff should be 6.0
volts, and so on.
Castle Creations’ Pixie-7P ESC allows
you to program the voltage cutoff point.
There aren’t that many choices, but they will
improve in time. Setting the voltage cutoff on
07sig2.QXD 4/26/04 8:33 am Page 48
the Pixie isn’t all that easy and does require
some patience, but this is the concept you
want to look for in the future!
Batteries: Until recently, the batteries of
choice for 4-ounce and lighter models were
the 100-125 mAh NiMH types, usually in
packs consisting of seven or eight cells. In the
past year we have been introduced to a new
form of battery known as the Li-Poly. These
new cells provide more capacity in a lighterweight
package. Both of those parameters are
exactly what you want for micro RC models.
Of equal interest is the fact that each Li-
Poly cell has a characteristic voltage of close
to 4.0; the older Ni-Cd/NiMH cells had only
1.2 volts per cell. So two Li-Poly cells work
like a six- or seven-cell Ni-Cd/NiMH pack.
We typically see two-cell packs consisting
of 145 mAh or 340 mAh powering 3- to 4-
ounce RC models. A two-cell 145 mAh Li-
Poly pack weighs 8.7 grams (.31 ounce) and
can fly that 3- to 4-ounce model at 700 mA
current (6 watts) for 10-12 minutes and more,
depending on how you throttle the motor in
flight. And two of the 340 mAh Li-Poly cells
(weighing 20.1 grams, or .71 ounce) could
provide up to 30 minutes of motor run time.
However, Li-Poly cells are still quite new
on the market, and they must be taken care of
very carefully. They require a special
dedicated charger and should not be charged
with more than a 1C current, which takes
roughly an hour. Li-Poly batteries should not
be discharged to less than 3.0 volts per cell.
Li-Poly cells are also currently somewhat
limited in their load capabilities. Initial
offerings could only provide loads up to
approximately 5C (five times the capacity of
the battery). Recently a new variety of Li-
Poly cell has been introduced that can stand
loads upward of 20C (quite an
improvement!).
Li-Poly batteries is a subject unto itself. I
wrote a comprehensive article titled
“Introduction to Lithium-Polymer Batteries”
that was published in the May 2004 MA. If
you haven’t read that piece, I highly
recommend that you do so before attempting
to use Li-Poly batteries in a model airplane of
any kind.
Micro RC System and Components: The RC
equipment is conventional technology, but is
obviously made smaller and lighter. An
inexpensive microreceiver is the GWS R-4P,
which has four-channel capability, is a singleconversion
circuit, and weighs 6.8 grams (.25
ounce). At approximately $30, it is a great
buy.
For those who want good range and
selectivity, in a crowded flying environment,
the FMA Direct M5 dual-conversion receiver
is an excellent choice, especially in the 2.5- to
4-ounce-model weight class. The M5 weighs
9.5 grams (.35 ounce).
Another outstanding choice is the Berg-
5*DSP at .35 ounce and the new Berg-4*DSP
Micro Stamp at just .25 ounce. The Berg
receivers are available from RC Direct. With
the Berg and FMA Direct receivers, you can
remove the receiver case for a further weight
reduction.
For the extra-small models (1.5 ounces
and lighter), the DWE RFFS-100 has been the
popular microsystem for some time. It is a
microreceiver, a built-in ESC with BEC, and
drivers for two magnetic actuators on a single
PC board. The entire board weighs only 1.8
grams (.06 ounce!).
The RFFS-100 receiver is not very
selective, so you can’t use several channels on
either side of your operating frequency when
flying. But this system has provided a load of
indoor RC fun-flying under the right
conditions.
Jean-Marie Piednoir (JMP) of France
makes a new and more selective
microreceiver which Bob Selman Designs
sells in the US. This receiver is claimed to be
extremely narrow band (selective!) and
includes an ESC and two magnetic actuator
drivers. It weighs 2.2 grams (.08 ounce), and
the price without connectors is $89. I’m sure
we will be seeing plenty of these units put
into indoor RC service in the near future.
As I was writing this, I learned of the new
Gasparin Penta 2.4-gram (.8-ounce) fourchannel
receiver, which is claimed to be
incredibly selective and will be selling in the
US at a reasonable $39.
In addition to receivers, servos or actuators
are also important. Conventional servos,
meaning regular proportional feedback
servos, are available at roughly 5.6 grams (.20
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07sig2.QXD 4/26/04 8:33 am Page 50
ounce). Two come to mind: the popular Hitec
HS-50 and the new FMA Direct PS-20. Each
sells for less than $30 and has been reliable.
The German WES-Technik company has
been making a linear-output-type microservo
for the past couple years. It weighs 2.1 grams
(.07 ounce) but is comparatively expensive at
$70-$80 (US).
Stefan Gasparin in conjunction with Didel
(the Swiss gear company) has designed a new
GDservo, which has a rotary output and
weighs 1.33 grams without a case. It will be
pricey, at $98 (US). Stefan also has a new
concept he calls a “Proportional Magnetic
Actuator.” I’ve seen some photos, and the
idea looks entirely realistic. Price is said to be
$39 each (US).
At the bottom of the weight scale are the
truly magnetic actuators; these are coil
devices with magnets that move inside the
coils. They require some patience to install
and offer little control force. That means your
hinges and control linkages must offer the
least possible friction. These magnetic
actuators make RC models of less than 1
ounce total weight possible. Good sources of
magnetic actuators include Bob Selman
Designs, Cloud-9 RC, E-Flight Design, and
DWE.
One last reference is to a “brick” design,
which was popular in the early 1970s. FMA
Direct is almost ready to release a microbrick
that will include one PC board, a narrow-band
receiver, ESC, control actuator drivers, and
two servos or two magnetic actuators. Placing
all of the components on a single board can
make certain installations impractical, but the
bottom line is that the brick eliminates a great
deal of wiring and connectors, thereby
reducing the overall weight. I believe this
concept will find a home in the 2.5- to 4-
ounce model category.
Connectors: The connectors and the wire size
(gauge, which refers to diameter) are
important. You want to carry the current
involved and no more; using a connector that
is too large or a wire with too large a diameter
only adds weight to little airplanes that can’t
afford it.
The larger parking lot-size models can
properly use the popular Anderson Power
Pole-type connectors (also known as Sermos
connectors). You can use these from roughly
6 amps of current up.
The Deans four-pin connectors are popular
for 3 to 6 amps of current. It is a good idea to
gang two pins to make a single connection. In
that case, the four pins yields two conductors.
From 1.5- to 3-amp current, the JST red
plastic housing connector is fine. For less than
1.5 amps of current, the JST white plastic or
Cloud 9 RC Unisex connectors will do the
job.
EFlight Designs carries an excellent line of
submicroconnectors. Wire size can start with
16 gauge for the 8- to 10-amp current. As you
work your way down in current, the wire
gauge can go from 22 to 28, and even 32.
Your hobby supplier can recommend the best
size for each current level. The JST
connectors come with the wire already
attached.
Indoor Flying Tips: If you are already an RC
sport flier or a parking lot flier, you are
certainly qualified to fly indoors; but the
generally “restricted” airspace can be
extremely challenging at times. If you are
lucky enough to be able to fly a 4-ounce
model in an inflated dome, it is almost the
same as flying outdoors—no problem!
However, when you get down to a doubleor
even single-size gymnasium, you get the
feeling that you are always turning the
airplane; there isn’t enough space for
appreciable straightaway flight.
Inside a dome my aircraft have
occasionally hit walls or even the top dead
center of the ceiling. Being such lightweight
models, they seem to just bounce off these
soft surfaces. Most of the time I lose altitude
but can easily recover the airplane to normal
flight.
On the other hand, at the Toledo, Ohio,
PERF (Perrysburg Electric River Fliers)
indoor fly a couple years ago (when it was a
smaller facility), I “shot a basket” with my
little 4.7-ounce AIKA. We had to get a large
stepladder to remove the model from the
basketball hoop/net.
However, before you start worrying about
these possibilities, consider that at such light
weights and wing loadings, not much ever
happens to micromodels—except for midair
52 MODEL AVIATION
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Fax (479) 646-1757
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www.foxmanufacturing.com
email: [email protected]
07sig2.QXD 4/26/04 8:34 am Page 52
July 2004 55
collisions! They do occur every once in
awhile, but if you build your entire model
from a single sheet of balsa, it’s no big deal!
NIRAC: AMA encourages SIGs to help
organize the various groups within model
aviation. We are lucky to have the National
Indoor Remote-Control Aircraft Council
(NIRAC) represent indoor RC flying within
the Academy. National Indoor Electric
Duration record-holder Bob Wilder of Texas
founded the organization several years ago.
You can access the Web site containing all
of the general information about this SIG at
www.nirac.org. Look it up, get familiar with
the organization, and show your support by
joining.
Once a year NIRAC sponsors a major
indoor RC championship. The 2004 dates are
June 4-6, and the location, as in the past, will
be the big Oakland Yard Athletics facility (an
inflated dome) in Waterford, Michigan
(www.oaklandyard.com/model_aviation.htm).
The flying plan for the three days includes
official indoor RC events including Scale,
racing, cargo lift, Old-Timer climb-and-glide,
endurance, and RC gliders. Between the
events the dome will be opened up for funflying
by all who attend.
NIRAC can also help you find local domes
and large indoor flying facilities. The current
NIRAC president—Dave Robelen—is one of
the most experienced indoor/micro RC fliers.
With indoor RC growing extraordinarily
rapidly, there is much to be learned; new
technology seems to emerge almost weekly.
The big, annual NEAT (Northeast Electric
Aircraft Technology) Fair held in upstate New
York, near the town of Downsville, includes a
series of indoor RC lectures during the three
days of the event.
Sergio Sigras coordinates these seminars.
Some of the most important names in
microflight—Henry Pasquet, Gordon
Johnson, Matt Keennon, Nick Leichty, Fred
Marks, Clarence Hurd, Bob Selman, and
more—provide the latest indoor RC
information.
For the Saturday night of the Fair, Gordon
Johnson sets up an indoor RC flight
demonstration in a double-size gym at nearby
Walton Senior High School. Guest lecturers
get to show their stuff, to the delight of
hundreds of spectators. To learn more about
the Fair, visit www.neatfair.org.
When you are attempting to gain
permission to fly indoor RC at local school
facilities, offer to lecture and/or give classes at
the school to offset your using the venue.
“Yes, you can use our gym, but why not come
in and let our young people learn how they
can participate?”
References: NIRAC is a good starting point.
Several publications regularly offer many
articles about indoor RC. Air Age Media’s RC
MicroFlight is available in hard-copy form
and online. It has been in production for more
than three years. When you subscribe, you
obtain a password that allows you access to all
previously published articles. You can even
download plans from the construction articles.
MA has two talented authors who write
alternating bimonthly columns. Dave Robelen
writes “Micro-Flying” (featuring indoor RC
and parking lot flying) and Paul Bradley
writes “Small-Field Flying” (covering parking
lot flying and backyard flying, and hitting on
indoor RC). I highly recommend these.
You can count on Quiet Flyer, under the
direction of publisher Wil Byers, for many
indoor RC-oriented articles each month. This
magazine specializes in electric power and
sailplane activities.
Flying Models magazine also has
alternating columnists who spend considerable
time in the world of indoor RC: Don Belfort
and Stew Meyers. For many years, RC
Modeler magazine has featured Jim Zare, who
now concentrates most of his activities on
micro and indoor flying.
I hate to sound too commercial, but
roughly two years ago I wrote the book
Getting Started in Backyard Flying. It
contains a lot of material about indoor RC.
You will see how parking lot/backyard flyers
tend to complement the indoor RC flyer. This
book is available from AMA, Tower Hobbies,
Balsa Products, and the publisher’s Web site:
www.rcstore.com/rs/general/books.asp.
In the late 1960s, people such as Dave
Robelen, John Worth, and Howard McEntee
experimented with multichannel proportional
RC control of glow-fueled models that
07sig2.QXD 4/26/04 8:34 am Page 55
weighed only 5-8 ounces! Those airplanes and
their equipment were tedious to work with,
but they did fly.
Soon afterward, AMA Hall of Famer Bill
Cannon of Cannon Electronics produced a
subminiature RC system that made smallscale
RC-model flying practical for everyone.
Bill continued to make that equipment for
many years and should be congratulated for
his efforts and dedication to small-model RC
flying.
Recently we have been privileged to see
the development of micro RC systems, servos,
actuators, Li-Poly batteries, tiny motors, and a
growing group of dedicated RC modelers who
have been willing to make this endeavor
grow. With modern large inflatable domes,
field houses, etc., it is now possible to enjoy
RC flying during all kinds of weather, at any
time of day or night.
Want to have some more fun in RC? Try
flying indoors. MA
Bob Aberle
[email protected]
Manufacturers/distributors:
Firefly coreless micro motors—direct and
geared:
AstroFlight Inc.
www.astroflight.com
GWS motors, propellers, Li-Poly batteries:
Balsa Products
www.balsapr.com
Li-Poly batteries:
Batteries America
www.batteriesamerica.com
JMP receivers, magnetic actuators, Li-Poly
chargers:
Bob Selman Designs
http://users.joplin.com/~bselman/
Voltage cutoff programmable ESCs:
Castle Creations
www.castlecreations.com
Assortment of micro hardware and products:
Cloud 9 RC (John Worth)
(703) 273-0607
Hard-to-get gears, motors, propellers, wire,
connectors:
David Lewis
www.homefly.com
Profile Roadkill series stand-off scale models:
DJ Aerotech
www.djaerotech.com
RFFS-100 micro RC systems, magnetic
actuators, JMP receivers, four-channel
conversion RFFS-100s:
Dynamic Web Enterprises (DWE)
www.smallrc.com
Reduced-size receiver antennas:
E Cubed R/C
www.azarr.com
Magnetic actuators, control-linkage
accessories, connectors:
EFlight Designs
www.eflightdesigns.com
Li-Poly batteries, chargers:
E-Tec (Air Craft)
www.aircraft-world.com
M5 micro DC receivers, submicroservos,
Kokam Li-Poly batteries, chargers:
FMA Direct
www.fmadirect.com
Penta 2.4-gram receivers, GDservo 1.33-gram
servos, new proportional magnetic actuators:
Gasparin
56 MODEL AVIATION
www.gasparin.cz
Motors, propellers, wheels, accessories:
Grand Wing Servo-Tech (GWS)
www.gws.com.tw
Cirrus Micro Joule receivers, ESCs, 3-gram
servos:
Global Hobby Distributors
www.globalhobby.com
Triton Li-Poly chargers:
Great Planes Model Distributors
www.electrifly.com
www.greatplanes.com
HS-50 submicroservo:
Hitec RCD
www.hitecrcd.com
Cirrus Micro Joule receiver, ESC, 3-gram
servos:
Hobby Club
www.hobbyclub.com
Motors, JR radios, Hobby Zone ARF indoor
models, Thunder Power Li-Poly batteries:
Horizon Hobby (GWS)
www.horizonhobby.com
Assortment of tiny direct- and gear-drive
motors:
Kenway Motors
(908) 850-9571
GWS motors, propellers, Li-Poly batteries:
Maxx Products International
www.maxxprod.com
ARF and RTF indoor models:
Megatech
www.megatech.com
Li-Poly batteries, connectors, wire:
Radical RC
www.radicalrc.com
Berg receivers:
RC Direct
www.rc-direct.com
Tiny geared motors, scale model kits:
RCS Technik (Chris Stewart)
www.falconmodels.uk.com
Microreceivers, ESCs, Li-Poly batteries,
chargers, model kits:
Sky Hooks and Rigging
www.microrc.com
Li-Poly batteries:
Thunder Power (Advanced Energy
Technology Inc.)
(702) 228-8883
Indoor model kits and supplies:
Todd Long Models
www.toddsmodels.com
Li-Poly chargers, ARF and RTF model kits:
Tower Hobbies
www.towerhobbies.com
7865 Mill Road, Elkins Park, PA. 19027 USA
Tel. 215 635 6520 Orders ONLY 888 721 0128 Fax. 215 635 4951
Email [email protected] www.sonictronics.com.
NEW
McDaniel R/C A Division of Sonic-Tronics Inc.
Patents, copyrights
and trademarks are
applied.
The New “Go-Slo III” has been
improved with added features.
With the precise performance of
an 8 bit microprocessor the output
is now “user selectable”. Two models are available. One can
drive a single servo, two servos in tandem, two servos with one
reversed or all three servos at once. The other model drives one,
two or three servos in parallel. Both models allow the servo speed to be
adjusted, 2 to 10+ seconds of travel in either direction. Go-Slo III units
are great for precise operation of Flaps, Gear etc. The receiver cable is now a
heavy 22 gage for better power delivery to one, two or three servos.
Go-Slo III‘s are compatible with 4.8 or 6 Volt systems and all proportional servos.
The unit is 1.5” x 1.5”x 3/4” and only .9 oz in weight.
07sig2.QXD 4/26/04 8:34 am Page 56