my interest in electric flight first started about a decade ago,
we struggled as pioneers in our hobby just to get planes to fly.
The brushed motors and NiCd packs had so much weight that we were
happy for even a 5 minute flight. We found a few combinations of
inexpensive components that seemed to work well; the most popular
using a Speed 400 motor. Still, there were others that wanted to
push the limits
even further. They created the first Electric Ducted Fan (EDF) units
using the limited resources of the time and toiled over making smooth
surfaces to help improve the air flow efficiency. Although these
early EDF Jets barely flew, my respect for their efforts and enthusiasm
remains to today.
that 10 year span, I kept my own focus on more efficient prop
driven flyers and watched first hand as the technology changes
flooded the hobby market. It was no longer much of a challenge
to make any plane fly and fly well. The combination of new
materials, brushless motors, lighter components, and higher
density battery technologies could bring new life to any design.
the prices dropped, the new technology was incorporated into
mass produced products and sold through major distributors.
brushless motors sustaining 30,000 to over 40,000 RPMs under load,
EDF units started performing very well. We first saw a series of
"fun" jets where the EDF unit was merely used to replace
an existing prop design, almost as an afterthought. We also saw
many streamlined jet designs that were powered by pusher props.
Then, it finally happened...the first high performance ARF ducted
fan jets hit the market. This month's issue of AMP'D is all about
jet fever as EDF goes mainstream.
First Mainstream EDF Performance
Alfa Models MIG-15 could be easily hand-launched or even take-off
right from grass.
Model in the Czech Republic has always been one of the top designers
of smaller foam Almost Ready to Fly (ARF) warbirds. I have reviewed
several of their models in the past and they always flew as well
as they looked. It was little surprise that they carried the same
mastery of foam design over to EDF jets. The first one that caught
the attention of many R/Cers was the little 29-1/2" wingspan
MIG-15. The model could be easily hand-launched with a little toss
and even had enough power to Rise Off Grass (ROG) by sliding on
its belly. When equipped with the recommended brushless motor and
LiPo pack, the MIG-15 could climb at a remarkable rate and tear
up the sky with excellent speed. The popularity of this model was
enhanced by a dynamic range of speed and performance that allowed
it to slow to a crawl for easy landings.
addition to great value and performance, what made this
EDF design popular in the mainstream of R/C hobbyists is
that it included the ducted fan as well as the smooth ducting.
The overall design made it simple to construct and when
the recommended power system components were used, you could
expect success on your first EDF model.
this 150-200 watt class EDF jet model set the bar for other
mainstream designs, the weakened U.S. dollar
provided opportunity for other manufacturers to compete.
Meets Elapor Foam
of my favorite materials to work with is the ELAPOR (pronounced
el-a-pore) foam used by Multiplex. It is designed to use CA
and kicker for fast, easy assembly time and it also resists
damage compared to many other types of foam. My previous reviews
models combined with my new passion for EDF dictated that
I had to buy a Twister.
made this purchase even more exciting was that the Twister
came with a completed Ready-To-Run (RTR) EDF unit.
The 70mm unit (EPF69BL)
is a Himax Brushless RTR Ducted Fan that comes with a HA2825-3600
Himax motor and is dynamically balanced (which means the blades
are balanced with a quick dry component and tested while spinning).
Twister turned out to be a great looking EDF Jet that
flies fast but still slows down for easy landings. It
is an excellent choice for your first EDF model but does
require intermediate flying skills. It can be hand-tossed
straight out with some zest.
foam packing that so cleverly keeps the Twister protected
during shipment can also be used as a stand for the completed
model by simply cutting out a "U" channel at
the Twister is a great overall design for mainstream R/C,
there are some of us that feel the need for more speed. Unfortunately,
the Himax HA2825-3600 motor is limited to a 3-cell LiPo pack
and about 350 watts.
an easy upgrade, the Ammo 28-45-3600
Inrunner Motor can be used in place of the stock Himax motor.
This motor allows the use of a 4-cell pack like the FlightPower
25 3700mAh 4-cell (14.8v) LiPo battery which easily provides
the needed 55 amps. The resultant power output is doubled
at about 700 watts providing unlimited vertical performance
without stressing the parts.
FlightPower EVO25 4s 3700mAh
Ammo 28-45-3600 Motor
AMMO upgrade provides twice the power over the stock motor.
Sparks, the custom plastics guru, has a canopy upgrade for
the Twister that costs only $14 including shipping. The kit
contains the canopy, instrument panel, pilot and ejection
finished canopy upgrade looks fantastic and you can use your
imagination to make it as detailed as you like. You can e-mail
Keith at firstname.lastname@example.org
to order this canopy upgrade or any of his other scale enhancements.
New Mainstream Releases
ElectriFly L-39 Albatros EDF ARF
Planes has responded to the demand for mainstream EDF models
with the ElectriFly
L-39 Albatros Jet EDF ARF. The 25" span jet comes
an Ammo In-runner motor, HyperFlow Ducted Fan unit, detachable
armament, a display stand, and, instruction manual.
L-39?s smooth surface is made from AeroCell?
foam which comes already finished with a militarystyle camouflage
trim. Decals are also factory applied and detachable display
magnetic armament is included. AeroCell? foam offers
the structural strength and rigidity of traditional structures
without building. It offers the weight advantages of foam
without the brittleness and breakage so a smooth, paintable
surface comes right out of the box factory-finished and
HyperFlow ducted fan unit was designed using flow analysis
and state-of-the-art computer modeling to identify the parameters
for high performance. The result is the ultimate ducted
fan design that, when combined with an Ammo brushless motor,
produces impressive thrust and speed.
sport-scale version of the L-39 Albatros Jet combines
extreme brushless motor performance with advanced
HyperFlow ducted fan technology. Assembly time is
quick and the wide-open flight envelope will be enjoyed
by all jet pilots.
that's what I call mainstream EDF!
E-flite F-15 Eagle DF ARF
new sport scale F-15 Eagle DF ARF (EFL7050)
is designed to emulate the flight characteristics and
response of the full-size tactical fighter. The versatile
foam model shows off an attractive Edwards Air Force Base
Safety Chase trim scheme in orange and silver with pre-applied
to use two E-flite Park 400 DF motors
(EFLM1320DF) to match the included ducted fan units
basic aerobatics, such as loops, rolls and split-S
from lightweight injection-molded EPS foam that?s
easy to repair
low wing loading and twin ductedfans allow superior maneuverability
and acceleration to perform basic aerobatics.
While this plane is capable of flying a tight flight pattern,
it can still be flown at your local park. The wings are
each reinforced with a carbon fiber tube spar for added
stability. This model also has full flying horizontal
stabilizers for pitch control and stability.
An ARF Jet design with Matching Components and retracts
is a great example of mainstream EDF!
Off the Beaten
mainstream EDF is relatively new, it doesn't take long until
your interest goes off the beaten path. You want a larger
model, more power, and maybe a good building fix. One example
is the Hayoe F-18 twin EDF kit made by Tak Lee Industrial
Company in China. This kit is sold by several U.S. distributors
but comes with little instruction and many ways to power
will detail my build and testing of the big F-18 foamy in
a future column.
At this time in the EDF revolution, you have a handful of
U.S. distributors selling unique products from around the
world. These smaller distributors support a niche part of
the market and often represent a company overseas. The choices
for EDF sizes are generally 50mm, 70mm, 90mm, and 120mm.
The prices go up with size and power but new entries in
the market are constantly lowering the cost through competition.
above are some new products from Great Planes that fit nicely
in my 90mm EDF application and provide a very cost-effective
solution. The AMMO 36-56-1800
In-Runner Brushless Motor fits perfectly in any 90mm EDF
unit. When combined with the ElectriFly Silver Series HV
60-amp ESC and a 5-cell FlightPower EVO30
4500mAh LiPo pack, the 1200 watt result produces about 4lbs
of thrust without stressing the components.
F-16 Fighting Falcon ARF
Model?s newest addition to their electric-powered
lineup of quality ARF aircraft is an exciting replica of
the F-16 that flies as well as it looks! The ARF kit features
a beautifully prepainted fiberglass fuselage with balsa
you can see, this 41" wingspan F-16
is designed to be a pusher-prop jet with a 600-800W brushless
motor and fly at about 3.5lbs.
a little work, a 90mm EDF unit can easily fit inside the
fiberglass fuselage and provide a 1200 watt ducted fan solution.
is a list of some vendors that provide EDF solutions...off the
General Rules of Ducted Fans
aerodynamics and rules of thumb of the ducted fan remain the same
regardless of the power source. Jet
Hangar International has compiled a list of items and frequently
asked questions that should be helpful to you in your EDF jet flying.
Here is their list of general rules for ducted fans.
a ducted fan works - Ducted fans operate as they sound:
they are an internally ducted high performance fan which
takes in air from the inlet opening and blows air out an
exhaust tube to generate forward thrust. The air enters
an impeller spinning at high RPM which propels pressurized
air out of its exhaust at increased pressure and velocity.
A ducted fan thrives on the air fed into it so too little
air will starve the fan, thus preventing it from perform
at its optimum design point. Conversely, inlets that are
grossly oversized can have the same effect: a ducted fan
can only process a given amount of air at any particular
time, so too much air will hamper performance --not to mention
the increased drag from the larger inlets.
Requirements for Ducted Fans - Ducted fans need inlets
sized to approximately 95%-110% of the Fan Swept Area (FSA)
with an exhaust outlet sized to approximately 75% 85% FSA.
Choking down airflow at the exhaust, increases exhaust velocity.
This in turn will increase top end speed of the aircraft.
There is, however, a point of diminishing returns: choking
down the exhaust too much will back pressure the fan resulting
in degraded performance. Additionally, a larger outlet area
will increase the static thrust of the system, but lower
the top end speed of the aircraft. The areas suggested above
represent a good compromise between static thrust and exhaust
Inlet Shape - The ideal inlet lip shape for a ducted
fan aircraft is a 2x1 ellipse. This represents the most
aerodynamic shape while maintaining good airflow into the
Swept Area - The fan swept area is calculated by subtracting
the area of the impeller hub from the area of the inside
of the shroud. The equation is shown below:
Area - Impeller Hub Area = Fan
Tractor vs. Pusher EDF
all EDF's are the tractor configuration in which the motor
is aft of the rotor so the air flow is pulled towards the
motor. A pusher configuration has the motor (or engine)
in front of the fan assembly and pushes air through the
duct. This configuration can be seen in Glow Ducted Fans
(GDF) but is still not very common due to efficiency and
exception to the overwhelming use of tractor-style EDF designs
is the Stumax
Aircraft SM110-52 EDF system. In this design, the motor
is forward with its wires pointing towards the battery,
which means the 180 degree bend and longer wires (typical
in tractor style designs) are no longer needed. The ESC
is now placed in between the fan unit and the battery. This
technique is more space efficient and provides less ducting
are some of us with deep pockets and equally abundant confidence.
When you mix those attributes with master craftsmanship
the result is extreme EDF performance and appearance.
Violet Models or BVMjets.com
is the place to go for extreme EDF. The new Electra
Jet provides top of the line performance.
BVM Electric VioFan uses a Neu 1521 motor, Castle Creations
HV110 ESC, and FlightPower EVO 30C 12s2p 6400mAh batteries
to exceed 200mph!
column was not meant to be an extensive dissertation on
EDF but rather an eye-opening introduction to the ongoing
evolution. The constant changes in technology have increased
the power-to-weight ratio in EDF power systems. At the same
time, prices have dropped and complete Ready-To-Run (RTR)
systems are now available through major distributors.
find it a very exciting time to get into the EDF craze.
As more products become "mainstream", you can
spend less time building and more time flying as you are
almost guaranteed success!
you fly electric, fly clean, fly quiet, and fly safe!
Special thanks for contributions
"Papa Jeff" Ring and Paul Weigand
This section of AMP'D covers some of the
questions that our readers have sent in and I thought
would be interesting for others.
V. asks: "Greg: First, congratulations on the AMP'D
segment in the rcuniverse magazine. It is what modelers
are looking for in the vast jungle of electric products
being offered. Recently burned a brushed electric motor
on my ECO 8 helicopter, I knew I was having heat problems
but not as much as burning it.
MUCH IS HOT IN AN ELECTIC MOTOR?
normal operation they turn hot, but how much heat can
they tolerate before the windings burn? Bought a brushless
inruner motor as a replacement and there is no temperature
range specification no where in the instructions.(ammo
inruner) I can only tell the engine is over heating
due to the bad selection of the engine pinion and poor
performance of the helicopter.
Thanks for the kind words. Your question about
motor temperature is a difficult one since it
has many answers that are dependant upon the motor
quality, motor type, and duration of high temperature.
I am not a heli expert but on my planes and EDF
applications, I do not like the motor temperature
to rise above 100 degrees C (212 degrees F). An
outrunner motor can hide the actual inner temperature
more than an inrunner motor due to the heavy metal
case that is spinning. Therefore, the inner temperatures
can be much hotter on an outrunner motor.
recent tests with the AMMO inrunner motors in
EDF applications look very promising and their
prices are very competitive. In the end, I guess
that motor longevity tells us when we are abusing
it too much. You seem to be able to tell when
your performance suffers so give the Ammo motor
a try. The increase in efficiency of the brushless
motor will make a big improvement. In a demanding
application like your ECO 8, it may be a trade
off between the cost of replacing a less expensive
motor and buying a more costly one meant for extreme
section of AMP'D reveals some of the feedback or suggestions
that our readers have sent in about previous issues.
RC Universe column, AMP'D - issue 4 - "Why Regulate?"
was a great article for all electric enthusiasts. It
is very important to know how all those electrons flow
and make our airplanes work. Your diagrams and text
explained it well. We will be recommending this article
to our customers. Keep up the good work!
newly released Hobby Lobby Hacker ?Warbirds
in Reno? flown by 15 year old Chris Hass
won the Open Pylon race at the E FEST in Champaign,
IL on February 8, 2008. Against a field of over
20 of the best pilots in the Midwest, Chris,
a member of the Skymasters R/C Club of Michigan,
flew the just released Strega. It is part of
a family of easy to build, fun to fly EPP aircraft.
Chris received the racer two days before the
event, assembled it with the recommended motor,
battery and prop, and did the test flights before
leaving Friday morning for Champaign. With only
a few flights under his belt Chris flew a very
tight pattern around the pylons throughout the
races. Chris took home a plaque and the $100.00
addition to the Strega five other aircraft are
available including Furias, Rare Bear, Red Baron,
Blue Bear and Ferias. A complete package for
your ?Reno Racer? is available from
Hobby Lobby. See your local dealer, visit www.hobby-lobby.com
or call 1-866-WE-Fly-RC (1-866-933-5972)
Hass poses with his Open Pylon
Award and new EPP Strega at the Great
in Champaign, IL.
is a fun airplane to build and fly? Chris
said. ?It goes together quickly. It has
a wide speed envelope so you fly it as fast
or as slow as you like. Plus it is durable.
I landed mine upside down during practice with