Large EDF Comes of Age - 2008/08

I LIVED THROUGH the bad, old days of
glow ducted fan. I have shoeboxes full of old,
burnt Rossi and O.S. .91 pistons to prove it.
Some modelers achieved reasonable
reliability with the large glow systems, but my
experience and that of most others was 10
flights at best before a pipe seal, glow plug, or
something else went; then you were testing
the rather limited gliding abilities of a 15-
pound jet (or brick).
I got a lot of flying in, but I made
numerous smoking holes along the way. I did
not enjoy the noise, the fuss, or the gallons of
glow fuel, but it was the only way to fly a jet
without sticking a propeller on the nose.
When turbines came out, I jumped right on
that—not so much because of the
performance increase, but mostly because of
the increase in reliability. Even at their worst,
turbines are tenfold more dependable than
glow ducted-fan (DF)-powered models.
Turbines have their own limitations,
though. They are expensive, intimidating, and
unwelcome at most fields for any number of
reasons.
But now there is an alternative. Several
large electric-ducted-fan (EDF) systems will
drop directly into those old glow DF airplanes
hanging from garage ceilings across the
country and fly them as well as the old Rossi
and O.S. engines did.
This did not happen overnight; it has been
a constant process of incremental
development. But there were a few
milestones, a couple of which were when
powerful-enough motors and controllers
became commonly available. That combined
with steady improvements in battery
technology has led us to where we are today.
Many individuals have spent a considerable
amount of time and money developing this
technology. However, driving large EDF into
the mainstream took the availability of
complete plug-and-play (PIP or PNP) systems
you can buy and stuff directly into an airplane
without needing an electrical degree, a
machine
shop, or
contacts
at secret
underground ESC factories in the Czech
Republic that have a two-year waiting list.
This article is not meant to be
comprehensive, but more of a primer covering
where we are today and the most popular PNP
large EDF systems out there. If you are a
jaded old hand who winds your own motors
and shows up with Horten flying wings at the
Aspach EDF meet every year, this article is
not for you. If you are an average sport
modeler who might have a hankering to get
into this new field, read on.
Keep in mind that this is not a product
comparison guide. I am neither endorsing nor
rating various systems—just showing you
what is out there, proven, and
readily available.
I had an epiphany
about large EDF a few
years ago at a jet rally.
A friend showed up
Photos by the author except as noted
STATE
SPORT
o f t h e Large EDF Comes of Age
by Curtis Mattikow
You can make an old jet state of the art!
The BVM Viper has long been popular as a glowpowered
model. Chris True adapted his to use the new
EDF systems and now enjoys this jet even more.
August 2008 65
66 MODEL AVIATION
Jason Noll’s 767-200 spans 115 inches and weighs 35 pounds. Its aero-naut 120mm
Turbo-Fan 4000 units use NeuMotors 1527 1.5Y motors to produce 18 pounds of thrust
each. The 12S Li-Poly battery system provides enough power to take off at 75% power
and cruise with only a 25% throttle setting. Ben Lanterman photo.
JHI designer and pilot Chris Wolfe
with the camouflage JHI A-7 ARF,
which is also available in an Edwards
Air Force Base paint scheme. The
ready-to-install E-Turbax fan runs on a
10S or 12S Li-Poly power system and
offers four- to five-minute flight times
with 150-160 mph performance.
with a Viper and a Yellow Aircraft Starfire
powered by EDF, and they were identical to
the “glow jobs” when they took to the air,
only without the noise.
I queried him and learned that he had been
experimenting for quite awhile with
components he had to get from all over the
planet. I was kind of turned off but intrigued
by the performance.
The next year several people showed up
with BVM Vipers—all with a PNP system
from Bob Violett Models (BVM). These
pilots were just fliers, not electric experts, and
they flew the heck out of the stuff. That was
when I realized that the large EDF had
arrived.
Who Has ’Em? There are several large EDF
units available, including the following.
• BVM Electric VioFan (EVF): The VioFan
represented the pinnacle of efficiency for glow
DF units. Both the fan unit and the engines for
the EVF went through constant evolution and
refinement to exact the most performance
from the glow-DF format.
The VioFan has been converted to electric
power and is available as a PNP unit,
consisting of fan, ESC, and motor, all factory
installed and balanced. The EVF comes in
five varieties, from one with 4,000 watts
designed for 10S Li-Poly cells to one with
more than 6,000 watts, designed around 16S
packs. The EVF puts out 14 pounds of static
thrust (20 for the 16S), well exceeding that of
the old glow versions.
Good, clean airframes have been routinely
seeing 170-200 mph with the EVF. Twenty
pounds of thrust on tap opens up possibilities
for all sorts of larger airframes that were
originally designed around 18- to 27-poundthrust
turbines.
The EVF costs $1,195-$1,695. However, it
is well proven and the support from BVM is
unmatched. This unit is also a drop-in fit to
the many superb BVM ducted-fan airframes,
such as the Maverick, Viper, and Sabre. They
have proven to fly extremely well using the
EVF system instead of glow.
Another great advantage is that you can
get every part you need from one source:
BVM. You can buy a complete airframe, fan
parts, and specifically made saddle-type Li-
Poly packs that will drop directly into the
spaces where the old glow saddle fuel tanks
used to be. In addition, the BVM Web site
contains complete documentation and
instructions for the care and feeding of your
fan and batteries.
This system may be pricey, but notice how
many happy BVM customers you see out
there and how many of them are successful.
Bob Violett does the tinkering and
experimenting, so you get a refined and
proven product for the money.
• Jet Hangar International E-Turbax: Larry
Wolfe of Jet Hangar International (JHI) has
been at the leading edge of ducted fans since
the earliest days, and his son, Chris, has joined
him. Chris was one of the earlier proponents
of high-performance EDF models, with his
remarkable F-14 twin and their neat Skyray
for the WeMoTec 480 MiniFan.
But JHI has gone into the large-EDF ring
with a conversion of its venerable Turbax fan,
called the “E-Turbax.” It comes in 10S and
12S varieties, rated at 4,000 and 4,500 watts
and 13 and 14 pounds of static thrust
respectively. The electric units handily outrun
the O.S. .46-powered glow versions.
The E-Turbax system has been flown
extensively and proven to be reliable. It is also
affordable, at $895 for a factory-test-run and
balanced unit including the Castle Creations
Phoenix 110-HV controller.
There are a vast number of Turbaxpowered
airframes out there; they were (and
still are) sold by the thousands. Most are
slightly lighter and smaller than the average
jet because they were designed around 45-size
engines rather than the .91. This makes them
particularly suitable for EDF conversions.
JHI has everything a jet pilot could need,
including its own line of Falcon-brand Li-
Polys, made precisely for the task, and a large
range of fiberglass-and-foam jet kits. Exciting
news is that the company is gradually
releasing ARF versions of its whole range of
jets. The A-7 ARF has been out for a year or
more and has been successful. The F-86
should be available soon.
• Stumax SM110-52: The Stumax fan
differs from the others in many ways. It
was designed from the ground up as an
electric fan, and it has a pusher
configuration (motor in the front) rather
than the tractor configuration of the others.
It has also benefited from a long, careful
development process using computational
fluid dynamics to extract the maximum
August 2008 67
Left: A123Systems’ low-impedance
Nanophosphate electrode technology
provides significant competitive advantage
over alternative high-power technologies.
Above: Refueling an
electric jet is “plug-in”
easy. Chargers such as this
one from Hyperion can
handle up to a 12S battery.
They require a DC 12-volt
power supply in the form of
a deep-cycle marine battery
or a 110-volt alternating
current (AC) converter.
As is the Viper, the BVM Electra is purpose-engineered to be an
electric-powered sport jet that is sized to suit the 5.25-inch
electric-fan units and 33.0- to 44.4-volt power systems. Lanterman
photo.
Left: Kent Nogy’s F-80 has been
flown for hours with a turbine, and
it enjoys similar performance with
electric power.
The BVM Viper sport jet is
excellent as an entry-level
large-EDF project. Used
airframes can be converted.
efficiency from the available power.
The SM110-52 is almost silent when it
runs. Noise equals wasted power, and if silence
indicates efficiency, this fan is extraordinarily
efficient.
It has a 110mm diameter, which is slightly
smaller than the others, and requires only 80%
of FSA (fan swept area) for inlets. That means
it is suitable for converting many turbine
airframes that have smallish inlets designed for
turbine use.
The Stumax fan represents more of the
future, with carefully designed EDF-specific
shrouds and rotors. It is currently set up to
produce 3,500 watts at only 77 amps, but it
puts out the same amount of thrust as the other
fans while using less power. Future versions
will have even more power; a 16S fan with
perhaps 18 pounds of thrust will probably be
released by the time you read this.
The SM110-52’s design is neat, easy to
install, and has tremendous long-term potential.
And the price is reasonable for such a carefully
thought-out and sophisticated unit, at $750.
Static Thrust: This is something of a red
herring when it comes to comparing fans. I
have measured 16 pounds of static thrust on
my old Byron Sabre, but it would be lucky to
top 110 mph on the downhill. However, I had
Dynamax-powered models
that measured only 8 pounds
of static thrust but would
approach 200 mph in flight.
Manufacturers need to list
static thrust because there is
no other way to give some
idea of the fan’s performance.
But the user shouldn’t read
static thrust as a true indicator
of what a fan can do. Thrust may go way up or
down in the air, exhaust velocity may be
dramatically different, and some fans perform
better or worse on the bench or with or without
the proper inlet or exhaust ducting.
Each fan performs differently in the air,
and I don’t want to make a point-by-point
performance comparison of the three I’ve
listed. It depends on the airplane and how you
fly.
Be careful about reading bench-test reports
in magazines and on the Internet. All benchtest
results seem great, and what a fan will do
hooked up to a test bench (usually with a
power supply instead of a battery) is often
completely different from what it will do in the
air.
Do your research! Get out to the field and
see what models pilots are flying, with what
fans, and how they go in the air.
ESC: The EVF, E-Turbax, and SM110-52 use
the Phoenix 110-HV controller. There are
alternatives, but most are expensive and come
from Europe, which can mean long wait times
if you need service; Castle Creations is located
here in the US. The 110-HV is well proven
against several others, which is a great reason
why it is the controller of choice.
And there is good news on the horizon.
Castle Creations is about to release a new
68 MODEL AVIATION
Roger Shipley’s 9-foot-long
A-10 was originally engineered to
fly on ducted-fan systems
and was adapted to use
vibration-free turbine
power. Flying a 54-pound
model such as this with
electric power is totally
doable. Lanterman photo.
Right: BVM’s
E l e c t r i c
VioFan can
drop into any
p r e v i o u s l y
e q u i p p e d
glow-powered
BVM model.
At half throttle,
the EVF will produce roughly 7.5
pounds of thrust, and consume 36
amps (10S) or 28 amps (12S), and
approximately 90 mph.
Right: JHI’s Turbax fan system has been a proven
performer for many years, powering all jet types. The
E-Turbax provides rpm exceeding 30,000 at more than
4,000 watts, producing more than 14 pounds of thrust.
version, the 110-SHV, which will be capable
of handling as many as 20 Li-Poly cells. When
motors that handle that become available, you
will be able to increase the voltage and reduce
the amperage and get the same or more power,
while being able to use less-expensive battery
cells.
Motors: All three systems I’ve mentioned also
share motors—made by Steve Neu of
NeuMotors—but they are different. Each fan
uses a particularly tweaked winding
configuration to handle the various loads of
assorted rotors.
There are alternative motors, such as
Lehner, Plettenberg, and other brands, but what
will work well in your fan is an open question.
There are good reasons why these
manufacturers have settled on NeuMotors as
their standard fitments; they work, and if
something goes amiss, service is right here in
the US rather than an ocean and a language
away.
Li-Poly Cells: For these applications you need
excellent batteries that will produce at least
25C. With lesser batteries, the voltage sags too
much under load and performance suffers or
the pack puffs. (Such a waste.)
I use MaxAmps batteries. There are many
brands, but batteries’ C ratings are often
exaggerated. This is not a big factor in most
circumstances, but these fan units are pushing
the limits, and the price of an inferior battery
may not be a bargain if it puffs on the first
flight. Stick with name brands that have good
warranties.
Also, most cell manufacturers suggest that
you don’t discharge your batteries more than
80% so they will have long, healthy lives. Be
aware of that when you are flying; a flight
timer is a must, and you need to keep flights
short at first. After every use, measure what
you put back into the battery and increase the
flight times incrementally until you have a
good idea of how much is being taken out in
what period of time.
Running a battery all the way to the lowvoltage
cutoff is bad in mainly two ways: it
shortens battery life and turns your jet into a
glider, as in the bad, old days of glow.
Airframes: There are scores of suitable
airframes. Thousands of glow-DF kits have
been sold through the years, and many are still
new in the box and available at swap meets,
just as many are hanging, gathering dust, from
ceilings at hobby stores. Some of the designs
are unsuitable for turbine conversion because
of structural issues or lack of room for fuel and
can be purchased for reasonable prices.
In addition, a goodly amount of new kits are
available from various sources, particularly
BVM and JHI, although there are not nearly as
many as there were five years ago. Nowadays
the trend is to go ARF. There are many out
there, and they are mostly for the turbine
market; but if you can keep the weight down,
some are eminently suitable for EDF
conversion. A successful conversion is the
Cermark F-16. It’s light, inexpensive, and goes
well on EDF power.
You may have to work on making proper
inlet ducting if you are converting a turbine
model. Exhaust ducting is simple—a rolled
plastic tube is basically all you need—but inlet
ducting may involve making a foam form and
then fiberglassing it and removing the foam.
If you have doubts about an airframe’s
suitability, ask your dealer for the bare
airframe’s weight and inlet and exhaust
diameters. Keep in mind that you don’t need a
wheel-brake system with EDF, so you can save
some weight and expense by using
conventional wheels and wire struts rather than
the heavier turbine landing-gear systems.
In the end, you can get almost anything
airborne with these systems, as you could with
an O.S. .91. But carefully selecting an airframe
and ducting is required to get outstanding
performance.
After the magic of seeing the model fly has
worn off, most pilots want it to perform like a
jet. Many of the older airframes weren’t sized
properly for the old glow fan systems in the
first place and flew marginally on them. That
won’t improve much with EDF power.
Charging: You need a good charger! Actually,
you’ll probably need two. Most batteries are
set up as a pair of five- or six-cell packs rather
than one 10- or 12-cell pack. Few chargers will
handle a 10S pack, so you are probably best off
getting two chargers that will handle 6S.
I like the Hyperion EOS 0606i, available
from MaxAmps, which has a balancer built in
and is AC/DC. But the new 0606i Duo will
accommodate two packs at once, which is
much nicer than waiting two hours between
flights. You need to balance your packs for
every charge cycle.
There are some terrific chargers out there,
such as the new FMA Direct Cellpro 10s. It
will charge and balance automatically with a
push of a button. I highly suggest that you
make a modest investment in quality chargers.
They are useful for all your batteries, not just
Li-Polys, and a good charger will take care of
your batteries.
Charge times are typically 40 minutes to
one hour, depending on how far you have
discharged the cells. So unless you like
waiting, consider investing in an extra set of
batteries to get more flight time.
Generators and Gel Cells: You are throwing
August 2008 69
Bob Violett has been at the forefront of model-jet propulsion
for a long time, but his flying is smoother and his models’
engineering is better than ever. This Electra Jet spans 60
inches, weighs a light 13.75 pounds, and has 4,000 watts of
energy at the pilot’s command.
Below: The Castle Creations
110-HV ESC is the gold standard
of controllers for EDF users. It’s
good for up to 12 cells. The
newer 110-SHV unit can handle
as many as 20 Li-Poly cells.
anywhere up to 6000 mA into your model
batteries on each charge. That’s a lot of power.
And if you hook a charger up to your car
battery, you have a good chance of needing a
jump-start before the end of the day (and
having to figure out how to reset the clock on
your dashboard). So what do you do?
It’s rare to have access to 110-volt house
current at most fields, so get a marine-type,
deep-cycle, 12-volt battery to feed your
chargers. Some pilots use a small gasolinepowered
generator to top off a 12-volt battery.
It’s noisy but effective, and it’s handy to have
around the house anyway.
Don’t be the last person at the field if you
have been charging from your car. Make sure
it starts at the end of the day before everyone
else leaves and you are stuck without a jump!
Off-Brand Fans and Motors: Some other fans
out there are European and of very high
quality, and a few are from the Far East and of
somewhat doubtful quality. However, all lack
the PNP functionality of the EVF, E-Turbax,
and SM110-52.
You may get the fan unit but have a hard
time finding the right motor with the right
shaft diameter to drive it properly or the
ducting to match your airplane. There are all
sorts of potentially expensive variables.
If you are a neophyte, stick with a proven
PNP system such as the ones I’ve mentioned.
You shouldn’t ignore other systems—some
are outstanding—but unless you feel
comfortable matching components and
potentially toasting batteries, controllers, or
motors, leave the bleeding edge to others.
The Future: Maybe the biggest hurdle for
large EDF aircraft is limited flight duration.
Six minutes is usually the maximum. But that
was the case with turbine-powered models
only a few short
years ago. It isn’t
anymore, so expect
the same
improvements in
big EDF airplanes.
The motors, and
the batteries in
particular, keep
improving (and
getting cheaper),
and performance
and duration keep
increasing. EDFs
might supplant
turbines in
popularity within
five years. I don’t
claim that turbines
will go away, only
that EDFs will be
more popular. There
are more places to
fly them, less
intimidation, lower
cost, and not as
much noise. I have watched the smaller EDFs
gradually come to meet and then greatly
exceed the power and duration of their glow
counterparts, and I’m confident that the same
will happen with the large versions.
The 200 mph barrier is already broken, 1:1
thrust ratio is possible, and scale flight of
almost any airframe is doable, so not much
needs to be proven. From here on there will be
only refinement and improvement; the large
EDF has “arrived”!
When you see one of these units in action,
I think you’ll be convinced. Visit a jet or
electric rally where you know a big EDF is
being demonstrated; seeing is believing. MA
Curtis Mattikow
[email protected]
Sources:
BVM
(407) 327-6333
www.bvmjets.com
Castle Creations
(913) 390-6939
www.castlecreations.com
FMA Direct
(800) 343-2934
www.fmadirect.com
JHI
(562) 467-0260
www.jethangar.com
MaxAmps
(888) 654-4450
www.maxamps.com
NeuMotors
(858) 674-2250
www.neumotors.com
Stumax Aircraft
+61 2 8819 4330
www.stumaxaircraft.com
Left: The typical battery setup
includes a pair of 6S 5000 mAh
25C packs, for a total of 12S
going to the motor. These from
MaxAmps are well suited for
the high-output task, but
conservative battery use will
better ensure their full life.
Below: The Stumax SM110 is a
unique pusher fan configuration.
Specially designed flow
straighteners on the front of
the unit effectively direct thrust
to improve output velocity.

I LIVED THROUGH the bad, old days of
glow ducted fan. I have shoeboxes full of old,
burnt Rossi and O.S. .91 pistons to prove it.
Some modelers achieved reasonable
reliability with the large glow systems, but my
experience and that of most others was 10
flights at best before a pipe seal, glow plug, or
something else went; then you were testing
the rather limited gliding abilities of a 15-
pound jet (or brick).
I got a lot of flying in, but I made
numerous smoking holes along the way. I did
not enjoy the noise, the fuss, or the gallons of
glow fuel, but it was the only way to fly a jet
without sticking a propeller on the nose.
When turbines came out, I jumped right on
that—not so much because of the
performance increase, but mostly because of
the increase in reliability. Even at their worst,
turbines are tenfold more dependable than
glow ducted-fan (DF)-powered models.
Turbines have their own limitations,
though. They are expensive, intimidating, and
unwelcome at most fields for any number of
reasons.
But now there is an alternative. Several
large electric-ducted-fan (EDF) systems will
drop directly into those old glow DF airplanes
hanging from garage ceilings across the
country and fly them as well as the old Rossi
and O.S. engines did.
This did not happen overnight; it has been
a constant process of incremental
development. But there were a few
milestones, a couple of which were when
powerful-enough motors and controllers
became commonly available. That combined
with steady improvements in battery
technology has led us to where we are today.
Many individuals have spent a considerable
amount of time and money developing this
technology. However, driving large EDF into
the mainstream took the availability of
complete plug-and-play (PIP or PNP) systems
you can buy and stuff directly into an airplane
without needing an electrical degree, a
machine
shop, or
contacts
at secret
underground ESC factories in the Czech
Republic that have a two-year waiting list.
This article is not meant to be
comprehensive, but more of a primer covering
where we are today and the most popular PNP
large EDF systems out there. If you are a
jaded old hand who winds your own motors
and shows up with Horten flying wings at the
Aspach EDF meet every year, this article is
not for you. If you are an average sport
modeler who might have a hankering to get
into this new field, read on.
Keep in mind that this is not a product
comparison guide. I am neither endorsing nor
rating various systems—just showing you
what is out there, proven, and
readily available.
I had an epiphany
about large EDF a few
years ago at a jet rally.
A friend showed up
Photos by the author except as noted
STATE
SPORT
o f t h e Large EDF Comes of Age
by Curtis Mattikow
You can make an old jet state of the art!
The BVM Viper has long been popular as a glowpowered
model. Chris True adapted his to use the new
EDF systems and now enjoys this jet even more.
August 2008 65
66 MODEL AVIATION
Jason Noll’s 767-200 spans 115 inches and weighs 35 pounds. Its aero-naut 120mm
Turbo-Fan 4000 units use NeuMotors 1527 1.5Y motors to produce 18 pounds of thrust
each. The 12S Li-Poly battery system provides enough power to take off at 75% power
and cruise with only a 25% throttle setting. Ben Lanterman photo.
JHI designer and pilot Chris Wolfe
with the camouflage JHI A-7 ARF,
which is also available in an Edwards
Air Force Base paint scheme. The
ready-to-install E-Turbax fan runs on a
10S or 12S Li-Poly power system and
offers four- to five-minute flight times
with 150-160 mph performance.
with a Viper and a Yellow Aircraft Starfire
powered by EDF, and they were identical to
the “glow jobs” when they took to the air,
only without the noise.
I queried him and learned that he had been
experimenting for quite awhile with
components he had to get from all over the
planet. I was kind of turned off but intrigued
by the performance.
The next year several people showed up
with BVM Vipers—all with a PNP system
from Bob Violett Models (BVM). These
pilots were just fliers, not electric experts, and
they flew the heck out of the stuff. That was
when I realized that the large EDF had
arrived.
Who Has ’Em? There are several large EDF
units available, including the following.
• BVM Electric VioFan (EVF): The VioFan
represented the pinnacle of efficiency for glow
DF units. Both the fan unit and the engines for
the EVF went through constant evolution and
refinement to exact the most performance
from the glow-DF format.
The VioFan has been converted to electric
power and is available as a PNP unit,
consisting of fan, ESC, and motor, all factory
installed and balanced. The EVF comes in
five varieties, from one with 4,000 watts
designed for 10S Li-Poly cells to one with
more than 6,000 watts, designed around 16S
packs. The EVF puts out 14 pounds of static
thrust (20 for the 16S), well exceeding that of
the old glow versions.
Good, clean airframes have been routinely
seeing 170-200 mph with the EVF. Twenty
pounds of thrust on tap opens up possibilities
for all sorts of larger airframes that were
originally designed around 18- to 27-poundthrust
turbines.
The EVF costs $1,195-$1,695. However, it
is well proven and the support from BVM is
unmatched. This unit is also a drop-in fit to
the many superb BVM ducted-fan airframes,
such as the Maverick, Viper, and Sabre. They
have proven to fly extremely well using the
EVF system instead of glow.
Another great advantage is that you can
get every part you need from one source:
BVM. You can buy a complete airframe, fan
parts, and specifically made saddle-type Li-
Poly packs that will drop directly into the
spaces where the old glow saddle fuel tanks
used to be. In addition, the BVM Web site
contains complete documentation and
instructions for the care and feeding of your
fan and batteries.
This system may be pricey, but notice how
many happy BVM customers you see out
there and how many of them are successful.
Bob Violett does the tinkering and
experimenting, so you get a refined and
proven product for the money.
• Jet Hangar International E-Turbax: Larry
Wolfe of Jet Hangar International (JHI) has
been at the leading edge of ducted fans since
the earliest days, and his son, Chris, has joined
him. Chris was one of the earlier proponents
of high-performance EDF models, with his
remarkable F-14 twin and their neat Skyray
for the WeMoTec 480 MiniFan.
But JHI has gone into the large-EDF ring
with a conversion of its venerable Turbax fan,
called the “E-Turbax.” It comes in 10S and
12S varieties, rated at 4,000 and 4,500 watts
and 13 and 14 pounds of static thrust
respectively. The electric units handily outrun
the O.S. .46-powered glow versions.
The E-Turbax system has been flown
extensively and proven to be reliable. It is also
affordable, at $895 for a factory-test-run and
balanced unit including the Castle Creations
Phoenix 110-HV controller.
There are a vast number of Turbaxpowered
airframes out there; they were (and
still are) sold by the thousands. Most are
slightly lighter and smaller than the average
jet because they were designed around 45-size
engines rather than the .91. This makes them
particularly suitable for EDF conversions.
JHI has everything a jet pilot could need,
including its own line of Falcon-brand Li-
Polys, made precisely for the task, and a large
range of fiberglass-and-foam jet kits. Exciting
news is that the company is gradually
releasing ARF versions of its whole range of
jets. The A-7 ARF has been out for a year or
more and has been successful. The F-86
should be available soon.
• Stumax SM110-52: The Stumax fan
differs from the others in many ways. It
was designed from the ground up as an
electric fan, and it has a pusher
configuration (motor in the front) rather
than the tractor configuration of the others.
It has also benefited from a long, careful
development process using computational
fluid dynamics to extract the maximum
August 2008 67
Left: A123Systems’ low-impedance
Nanophosphate electrode technology
provides significant competitive advantage
over alternative high-power technologies.
Above: Refueling an
electric jet is “plug-in”
easy. Chargers such as this
one from Hyperion can
handle up to a 12S battery.
They require a DC 12-volt
power supply in the form of
a deep-cycle marine battery
or a 110-volt alternating
current (AC) converter.
As is the Viper, the BVM Electra is purpose-engineered to be an
electric-powered sport jet that is sized to suit the 5.25-inch
electric-fan units and 33.0- to 44.4-volt power systems. Lanterman
photo.
Left: Kent Nogy’s F-80 has been
flown for hours with a turbine, and
it enjoys similar performance with
electric power.
The BVM Viper sport jet is
excellent as an entry-level
large-EDF project. Used
airframes can be converted.
efficiency from the available power.
The SM110-52 is almost silent when it
runs. Noise equals wasted power, and if silence
indicates efficiency, this fan is extraordinarily
efficient.
It has a 110mm diameter, which is slightly
smaller than the others, and requires only 80%
of FSA (fan swept area) for inlets. That means
it is suitable for converting many turbine
airframes that have smallish inlets designed for
turbine use.
The Stumax fan represents more of the
future, with carefully designed EDF-specific
shrouds and rotors. It is currently set up to
produce 3,500 watts at only 77 amps, but it
puts out the same amount of thrust as the other
fans while using less power. Future versions
will have even more power; a 16S fan with
perhaps 18 pounds of thrust will probably be
released by the time you read this.
The SM110-52’s design is neat, easy to
install, and has tremendous long-term potential.
And the price is reasonable for such a carefully
thought-out and sophisticated unit, at $750.
Static Thrust: This is something of a red
herring when it comes to comparing fans. I
have measured 16 pounds of static thrust on
my old Byron Sabre, but it would be lucky to
top 110 mph on the downhill. However, I had
Dynamax-powered models
that measured only 8 pounds
of static thrust but would
approach 200 mph in flight.
Manufacturers need to list
static thrust because there is
no other way to give some
idea of the fan’s performance.
But the user shouldn’t read
static thrust as a true indicator
of what a fan can do. Thrust may go way up or
down in the air, exhaust velocity may be
dramatically different, and some fans perform
better or worse on the bench or with or without
the proper inlet or exhaust ducting.
Each fan performs differently in the air,
and I don’t want to make a point-by-point
performance comparison of the three I’ve
listed. It depends on the airplane and how you
fly.
Be careful about reading bench-test reports
in magazines and on the Internet. All benchtest
results seem great, and what a fan will do
hooked up to a test bench (usually with a
power supply instead of a battery) is often
completely different from what it will do in the
air.
Do your research! Get out to the field and
see what models pilots are flying, with what
fans, and how they go in the air.
ESC: The EVF, E-Turbax, and SM110-52 use
the Phoenix 110-HV controller. There are
alternatives, but most are expensive and come
from Europe, which can mean long wait times
if you need service; Castle Creations is located
here in the US. The 110-HV is well proven
against several others, which is a great reason
why it is the controller of choice.
And there is good news on the horizon.
Castle Creations is about to release a new
68 MODEL AVIATION
Roger Shipley’s 9-foot-long
A-10 was originally engineered to
fly on ducted-fan systems
and was adapted to use
vibration-free turbine
power. Flying a 54-pound
model such as this with
electric power is totally
doable. Lanterman photo.
Right: BVM’s
E l e c t r i c
VioFan can
drop into any
p r e v i o u s l y
e q u i p p e d
glow-powered
BVM model.
At half throttle,
the EVF will produce roughly 7.5
pounds of thrust, and consume 36
amps (10S) or 28 amps (12S), and
approximately 90 mph.
Right: JHI’s Turbax fan system has been a proven
performer for many years, powering all jet types. The
E-Turbax provides rpm exceeding 30,000 at more than
4,000 watts, producing more than 14 pounds of thrust.
version, the 110-SHV, which will be capable
of handling as many as 20 Li-Poly cells. When
motors that handle that become available, you
will be able to increase the voltage and reduce
the amperage and get the same or more power,
while being able to use less-expensive battery
cells.
Motors: All three systems I’ve mentioned also
share motors—made by Steve Neu of
NeuMotors—but they are different. Each fan
uses a particularly tweaked winding
configuration to handle the various loads of
assorted rotors.
There are alternative motors, such as
Lehner, Plettenberg, and other brands, but what
will work well in your fan is an open question.
There are good reasons why these
manufacturers have settled on NeuMotors as
their standard fitments; they work, and if
something goes amiss, service is right here in
the US rather than an ocean and a language
away.
Li-Poly Cells: For these applications you need
excellent batteries that will produce at least
25C. With lesser batteries, the voltage sags too
much under load and performance suffers or
the pack puffs. (Such a waste.)
I use MaxAmps batteries. There are many
brands, but batteries’ C ratings are often
exaggerated. This is not a big factor in most
circumstances, but these fan units are pushing
the limits, and the price of an inferior battery
may not be a bargain if it puffs on the first
flight. Stick with name brands that have good
warranties.
Also, most cell manufacturers suggest that
you don’t discharge your batteries more than
80% so they will have long, healthy lives. Be
aware of that when you are flying; a flight
timer is a must, and you need to keep flights
short at first. After every use, measure what
you put back into the battery and increase the
flight times incrementally until you have a
good idea of how much is being taken out in
what period of time.
Running a battery all the way to the lowvoltage
cutoff is bad in mainly two ways: it
shortens battery life and turns your jet into a
glider, as in the bad, old days of glow.
Airframes: There are scores of suitable
airframes. Thousands of glow-DF kits have
been sold through the years, and many are still
new in the box and available at swap meets,
just as many are hanging, gathering dust, from
ceilings at hobby stores. Some of the designs
are unsuitable for turbine conversion because
of structural issues or lack of room for fuel and
can be purchased for reasonable prices.
In addition, a goodly amount of new kits are
available from various sources, particularly
BVM and JHI, although there are not nearly as
many as there were five years ago. Nowadays
the trend is to go ARF. There are many out
there, and they are mostly for the turbine
market; but if you can keep the weight down,
some are eminently suitable for EDF
conversion. A successful conversion is the
Cermark F-16. It’s light, inexpensive, and goes
well on EDF power.
You may have to work on making proper
inlet ducting if you are converting a turbine
model. Exhaust ducting is simple—a rolled
plastic tube is basically all you need—but inlet
ducting may involve making a foam form and
then fiberglassing it and removing the foam.
If you have doubts about an airframe’s
suitability, ask your dealer for the bare
airframe’s weight and inlet and exhaust
diameters. Keep in mind that you don’t need a
wheel-brake system with EDF, so you can save
some weight and expense by using
conventional wheels and wire struts rather than
the heavier turbine landing-gear systems.
In the end, you can get almost anything
airborne with these systems, as you could with
an O.S. .91. But carefully selecting an airframe
and ducting is required to get outstanding
performance.
After the magic of seeing the model fly has
worn off, most pilots want it to perform like a
jet. Many of the older airframes weren’t sized
properly for the old glow fan systems in the
first place and flew marginally on them. That
won’t improve much with EDF power.
Charging: You need a good charger! Actually,
you’ll probably need two. Most batteries are
set up as a pair of five- or six-cell packs rather
than one 10- or 12-cell pack. Few chargers will
handle a 10S pack, so you are probably best off
getting two chargers that will handle 6S.
I like the Hyperion EOS 0606i, available
from MaxAmps, which has a balancer built in
and is AC/DC. But the new 0606i Duo will
accommodate two packs at once, which is
much nicer than waiting two hours between
flights. You need to balance your packs for
every charge cycle.
There are some terrific chargers out there,
such as the new FMA Direct Cellpro 10s. It
will charge and balance automatically with a
push of a button. I highly suggest that you
make a modest investment in quality chargers.
They are useful for all your batteries, not just
Li-Polys, and a good charger will take care of
your batteries.
Charge times are typically 40 minutes to
one hour, depending on how far you have
discharged the cells. So unless you like
waiting, consider investing in an extra set of
batteries to get more flight time.
Generators and Gel Cells: You are throwing
August 2008 69
Bob Violett has been at the forefront of model-jet propulsion
for a long time, but his flying is smoother and his models’
engineering is better than ever. This Electra Jet spans 60
inches, weighs a light 13.75 pounds, and has 4,000 watts of
energy at the pilot’s command.
Below: The Castle Creations
110-HV ESC is the gold standard
of controllers for EDF users. It’s
good for up to 12 cells. The
newer 110-SHV unit can handle
as many as 20 Li-Poly cells.
anywhere up to 6000 mA into your model
batteries on each charge. That’s a lot of power.
And if you hook a charger up to your car
battery, you have a good chance of needing a
jump-start before the end of the day (and
having to figure out how to reset the clock on
your dashboard). So what do you do?
It’s rare to have access to 110-volt house
current at most fields, so get a marine-type,
deep-cycle, 12-volt battery to feed your
chargers. Some pilots use a small gasolinepowered
generator to top off a 12-volt battery.
It’s noisy but effective, and it’s handy to have
around the house anyway.
Don’t be the last person at the field if you
have been charging from your car. Make sure
it starts at the end of the day before everyone
else leaves and you are stuck without a jump!
Off-Brand Fans and Motors: Some other fans
out there are European and of very high
quality, and a few are from the Far East and of
somewhat doubtful quality. However, all lack
the PNP functionality of the EVF, E-Turbax,
and SM110-52.
You may get the fan unit but have a hard
time finding the right motor with the right
shaft diameter to drive it properly or the
ducting to match your airplane. There are all
sorts of potentially expensive variables.
If you are a neophyte, stick with a proven
PNP system such as the ones I’ve mentioned.
You shouldn’t ignore other systems—some
are outstanding—but unless you feel
comfortable matching components and
potentially toasting batteries, controllers, or
motors, leave the bleeding edge to others.
The Future: Maybe the biggest hurdle for
large EDF aircraft is limited flight duration.
Six minutes is usually the maximum. But that
was the case with turbine-powered models
only a few short
years ago. It isn’t
anymore, so expect
the same
improvements in
big EDF airplanes.
The motors, and
the batteries in
particular, keep
improving (and
getting cheaper),
and performance
and duration keep
increasing. EDFs
might supplant
turbines in
popularity within
five years. I don’t
claim that turbines
will go away, only
that EDFs will be
more popular. There
are more places to
fly them, less
intimidation, lower
cost, and not as
much noise. I have watched the smaller EDFs
gradually come to meet and then greatly
exceed the power and duration of their glow
counterparts, and I’m confident that the same
will happen with the large versions.
The 200 mph barrier is already broken, 1:1
thrust ratio is possible, and scale flight of
almost any airframe is doable, so not much
needs to be proven. From here on there will be
only refinement and improvement; the large
EDF has “arrived”!
When you see one of these units in action,
I think you’ll be convinced. Visit a jet or
electric rally where you know a big EDF is
being demonstrated; seeing is believing. MA
Curtis Mattikow
[email protected]
Sources:
BVM
(407) 327-6333
www.bvmjets.com
Castle Creations
(913) 390-6939
www.castlecreations.com
FMA Direct
(800) 343-2934
www.fmadirect.com
JHI
(562) 467-0260
www.jethangar.com
MaxAmps
(888) 654-4450
www.maxamps.com
NeuMotors
(858) 674-2250
www.neumotors.com
Stumax Aircraft
+61 2 8819 4330
www.stumaxaircraft.com
Left: The typical battery setup
includes a pair of 6S 5000 mAh
25C packs, for a total of 12S
going to the motor. These from
MaxAmps are well suited for
the high-output task, but
conservative battery use will
better ensure their full life.
Below: The Stumax SM110 is a
unique pusher fan configuration.
Specially designed flow
straighteners on the front of
the unit effectively direct thrust
to improve output velocity.