In
2008, Electric Ducted Fans (or EDFs) started flooding the
market at a faster pace than ever. Mainstream EDF models under
3lbs and 500 watts continued to be released by major distributors.
We saw the transition from 50mm to 70mm ducted fans in greater
variety and some of the models were even made from fiberglass
instead of less expensive foam. Included in this mainstream
rush to market new models was a category of Ready-To-Fly (RTF)
EDF models that came complete with power system, radio, and
battery. Novice EDF enthusiasts, and even novice R/Cers, were
all but guaranteed success with their first electric jet model.
Since
mainstream EDF is relatively new, if you are a real jet enthusiast,
it doesn't take long until your interest goes off the beaten
path. You want a larger
model with more power or maybe a good building fix. You can't
see spending thousands of dollars on an R/C model but you
want something between 3lbs and 10lbs with enough power to
get noticed or even take-off with functional retracts.
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. Some specialty places
make their own R/C support products as an offshoot of their
main business. The choices for these EDF products range from
smaller 50mm (2") ducted fans on up to a more powerful
120mm (5") unit. The prices go up with size and power
but new entries in the market are constantly lowering the
cost through competition. There are some very innovative and
popular designs taking on this smaller portion of the market.
My
focus in this month's issue of AMP'D is to introduce newer
EDF enthusiasts that want to advance faster than the current
mainstream market allows without breaking the bank. The choices
for EDF are both vast and exciting when you start to venture
off the beaten path.
Choices? What Choices?
Here
is a list of some vendors, in alphabetical order, that provide EDF
solutions...off the beaten path.
The
general "watts per pound" rule of thumb still applies
to EDF which makes it easier to select an appropriate power
system based upon the models weight and desired performance.
Although individual preferences vary, these numbers are what
I use:
150w/lb
for Fair EDF performance
200w/lb
for Good EDF performance
250w/lb
for Great EDF performance
300w/lb
(or greater) for Extreme EDF performance
The
WeMoTec
Midi Fan pro 90mm ducted fan comes with a dynamically
balanced, 6-bladed, glass filled nylon rotor.
It
is conservatively rated for up to 1000 watts input power and
a maximum of 35,000 RPMs.
When
using brushless motors and LiPo batteries, you are already starting
out with highly efficient components compared to the old days
when brushed motors and NiCd cells were used. There are other
areas that affect EDF efficiency to a lesser degree. Inrunner
motors are more efficient than outrunner motors and not all
ducted fan units are equal. The rotor blade count and shape
can affect both efficiency and power draw for a given setup.
The
graph on the right was created by Carl Rich. He is the type
of hobbyist that has an enthusiastic drive to gather data
in a self-less manner that helps the entire hobby. Carl has
become a respected source for EDF data and graciously allowed
me to display his findings.
The
information displayed on the right shows that not all DFs
are created equal. The Wemotec Midi Fan pro 90mm ducted fan
has greater thrust than other DFs for a given power level.
This means longer run times
Thrust
vs. Watts for 90mm DFs
and
cooler components from the increased efficiency. I have tried
all the brands in Carl's graph, as well as others, and found
that they also work fine. Sometimes, a different blade count
can be a better fit for your choice of motor and cell count.
More blades, more cells, and more size all draw more current
on a given motor. These parameters, along with the motor Kv
(RPMs/volt), will allow you adjust the power system. You may
not even care or notice a loss of efficiency in other brands
of DFs but if you plan to push the limits, it is good to know
that not all DFs are created equal.
Large Foam EDFs
When
you venture off the beaten path, you will find several larger
foam models available at a lower cost than fiberglass models
of similar size. Versatile foam models allow the builder in
you to either use it as is, or treat it simply as a base for
glassing and customizing to your own vision.
One
example of a large foam model 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 (listed above). It comes with little
instruction and many ways to power it.
This
F-18 kit can be powered by twin EDF units, a single
larger EDF unit or even a pusher prop setup.
The
EPS foam kit comes in many pieces so there is plenty
of work required to complete it. It can be fit with
retracts, fixed gear, or nothing but a hook for bungee
launching.
My
Hayoe F-18 was finished in a Blue Angles color scheme. It
uses two Ammo 28-45-3600
Inrunner Motors with the MPI EPF69BL
5-blade 70mm fans equipped with the EPF69-3
Rotor adapter for 1/8" shaft.
Using
a 4-cell pack like the ThunderPower eXtreme
V2 3300mAh (14.8v) LiPo battery, I measured 55 amps at
700 watts on each EDF.
The
maximum constant current rating of the AMMO 28-45-3600 Inrunner
Motor is 600w so its not being pushed too hard for 700w bursts.
The FlightTech 60A
ESC and TP eXtreme V2 packs can easily handle the 55 amp
bursts at full throttle. My F-18 was ready to fly at 102oz
(6.4lbs) with the two TP V2 3s 3300mAh packs. The combined
70mm EDFs created a 1400 watt power system that provided 219w/lb
which allowed the big F-18 to lift at a lower speed than if
it had been fitted with retracts and heavier 90mm EDFs or
batteries.
The
finished Hayoe F-18 weighed 6.4lbs Ready-To-Fly.
The
F-18 is bungee-launched from a machined foot launcher (detailed
below)
The
BAe Hawk is another example of a large foam EDF model. It
is one member in a series of Styrofoam EDF jets from FlyFly
Hobby. These models are distributed overseas by Hobby88.com
or here in the U.S. by Electric Jet Factory (EJF.com).
If
you are not familiar with FlyFly Hobby foam jet models,
they are uniquely engineered designs that are made from
EPS foam. The large jets are designed for 90mm EDFs and
fit together like a precision 3D puzzle piece. They come
with the ducted fan unit and fixed landing gear. They can
be hand-launched over grass or fitted with optional retracts.
The
BAe Hawk is powered by a single 92mm ducted fan unit that
uses a B36-class 1000w brushless motor. The kit comes with
the scale aluminum suspension (Oleo strut) landing gear
and the fuselage is separated by 4 pieces for easy shipping.
The Hawk is designed for both fixed and retractable gear.
The fuselage has enough room for high capacity battery packs
for longer run time and higher air speed.
My
Hawk was powered by the following components listed below.
The AMMO 36-56-1800 motor is $20 less than the Typhoon EDF-600-32
motor and has a higher Kv for greater speed. The FlightPower
ESC can be hammered hard even in heli applications up to
80-amps and doesn't need a separate BEC for up to a 6s Lipo.
However, it is always safest to use an external BEC on most
ESCs running a 5s or 6s LiPo pack.
The
5-cell FlightPower pack weighs 21oz compared to the 18oz
6-cell pack. The higher capacity 5-cell pack will provide
longer flights but not fly as fast as the 6-cell pack.
The
AMMO motor mounted easily using the 5mm adapter that comes
with the Hawk. Note that the motor wires are extended to
23" lengths. This allows the ESC to enter the battery
compartment under the canopy for easy access. I tested the
completed assembly before mounting it in the fuselage. It
ran very smooth with almost no vibration.
There
was plenty of room for my FlightPower 30C 5s and 6s packs.
The model balanced well being slightly nose heavy. The battery
to ESC connection is easy to make due to the quick canopy
release so I removed the On/Off switch and soldered the
wires together.
My
FlyFly BAe Hawk was Ready-To-Fly at 83oz (or 5.2lbs) with
battery pack. The plane without a pack weighed 62oz. The
power level was 775w at 47amps using the 21oz FlightPower
EVO30 5s 4500mAh pack and 1200w at 64amps using the 18oz
FlightPower EVO30 6s 3200mAh pack.
We
test flew the Hawk in some pretty harsh conditions during
the winter. The cold winds gusted from 15-25mph but didn't
seem to faze the Hawk on either a 5s or 6s LiPo pack. This
plane is an impressive flyer and can easily be hand-launched.
Fiberglass EDF Models
If
cost-effective fiberglass models are your preference, then
High
End Technology RC (or HET) is the place to check out.
HET specializes in manufacturing Electric Ducted Fan Jets
and accessories such as ducted fans, brushless motors and
ESCs.
HET
has many single EDF models to choose from and several twin
EDF models like this F-18.
My
HET F-18 uses twin 70mm power systems to create 1400 watts
total power very similar to my bigger foam Hayoe F-18. I use
the cost-effective ElectriFly AMMO motors as they are less
than comparable motors with seemingly equal performance. The
FlightPower ESCs can be hammered hard even in heli applications
up to 80-amps and don't need a separate BEC for up to a 6s
Lipo.
Here
is what I used to power my HET twin 70mm model:
The
V-Pro Mig-15 EDF Jet ARF from Advantage
Hobby boasts speeds of over 120mph! The painted fiberglass
fuselage comes with the 69mm fan unit and motor pre-installed.
The sheeted wing and tail halves are pre-covered, making assembly
time quick!
The
model comes with a 7-page construction guide, decals, linkages,
hardware, Tamazo DF-69 Fan Unit with mounted brushless motor,
and a "sling-shot" starter set.
The
33" long, pre-painted, single-piece fiberglass fuselage
also contains the vertical stabilizer. The sheeted wing halves
were rock-solid and perfectly covered. The ARF jet package
comes with a minimum amount of parts.
V-Pro
MIG-15 EDF ARF
Specifications:
Length:
33.3"
Wingspan: 32.9"
Wingarea: 222 sq. in.
Flying Weight: 39 - 42 oz.
The bottom "cheater" holes (shown on left) allow
more air into the ducted fan unit for increased thrust.
The
power system was completed with the E-flite (EFLA1060)
60-amp Pro Brushless ESC that has a switching BEC regulator
which allows you to operate up
to 7 analog or 6
digital standard-sized servos on any recommended input voltage.
No external regulator is needed with the 4-cell LiPo pack.
The pre-installed E-flite ESC motor connectors fit the pre-installed
Tamazo motor connectors perfectly. It was a simple plug and
play solution with no programming needed.
The
FlightPower (EVO2537004S)
25C 4-cell 3700mAh LiPo Pack provides a perfect CG balance
of 70mm from the trailing edge at 13oz. The pack can deliver
up to 90-amps continuous, if needed, so the 42-amp demand
will not stress it even if the entire flight is at full throttle.
The
MIG-15 was Ready-To-Fly at 46.5oz (2.9lbs) including the 13oz
FlightPower pack. The power system measured 600 watts at 42-amps
for a power level of 207w/lb.
The
Mig-15 flew fantastic! It rolled nicely and flew inverted.
It does land at a quick pace until you get some experience
with it so a long field is needed. We used 300' to 400' to
land.
Although
the Mig-15 flies fantastic, I would only recommend this model
to the intermediate to advanced level pilot because it really
moves out and can literally disappear in a grey sky. This
skill level requirement is typical when you go off the beaten
path.
For
a complete review on the MIG-15 from Advantage Hobby, click
here.
The
EDF
Predator UCAV from Nitro Planes is a large fiberglass
jet model with sheeted wings. It comes complete with landing
gear, fiberglass canopy, missiles, and all hardware. The model
can be powered by a 90mm to 101mm ( 3.5" to 4" )
EDF unit.
The
fiberglass canopy is pre-finished and only needs the latch
mechanism attached. The landing gear are fixed with a steerable
nose wheel assembly. Two sheets of finishing decals are supplied
and the 7-page manual, although sparse, provides sufficient
photos and text to complete the model by an experienced assembler.
Although
it is still a work in progress, my planned power system will
be a WeMoTec Midi Pro 90mm EDF, a new AMMO 36-88-1280kV Inrunner
Brushless motor, Castle Creations HV85 ESC, and an 8s FlightPower
LiPo pack. At only $100, the AMMO motor appears to be a great
fit for high-powering a low-cost 90mm EDF. On an 8s LiPo supply,
it can provide burst power up to 2000 watts at a 74amp burst
current. This delivers 6.9lbs of EDF thrust and is within
the AMMO 36-88-1280kV Inrunner specifications.
One of the fun parts of going off the beaten path is to try
new combinations.
Two FlightPower LiPo 14.8V 4s EVO30
3200mAh packs in series
EDF Launching Methods
Unless you are fortunate enough to have a paved runway to
fly off of, or don't have any smaller sized EDF models, you
will need to consider other methods for launching these planes.
Some jet designs are surprisingly adaptable and can be modified
to take off of grass or even your hand! If hand-launching
doesn't work or it is just out of the question, consider a
bungee launch system with wheels, dolly, or catapult ramp.
Don't Fear the Bungee!
This
bungee launcher system is manufactured by MBM Jets and distributed
by DuctedFans.com.
It is designed to keep the nose of the plane up and off the
ground for easy launches. Various cord sizes and lengths can
be purchased for planes ranging from 2lbs to 12lbs.
The
bungee pedal release unit is produced by manufacturers like
MBM Jets and Wemotec. Both DuctedFans.com and WarbirdsR-C.com
distribute the launcher. The spike is built into the bungee
pedal release unit making it very easy to setup in the field.
The design allows the pilot to launch his own jet.
I
used an old drapery hanger as a tow hook on my big Hayoe F-18.
The pull force is distributed by plywood pieces that were
epoxied in place just in front of the CG. The foot-release
launcher allows me to get all set up at my leisure before
the flight begins. I used the 6-8lb cord on my 6.4lb model.
Bungee Catapult
This
PVC ramp "Bungee Catapult" from ClassicFlyingMachines.com
is available as a short kit (90% complete) which saves you
both time and money because all the hard work is done. The
original launcher, designed by Brian Riddell around 2002,
used to be available on the E-Zone (RC Groups) as a construction
article.
Mini Bungee
- The "sling-shot" starter set (shown right) came
with the V-Pro MIG-15 ARF and worked perfect every time. It
is a great mini-bungee launcher for models up to 3lbs. You
pull the bungee back (using the model's tail) as far as it
can go and then let the jet go when the motor is up to speed.
The
key to a successful bungee launch is to get as low as possible
to the ground and pull the cord back just short of all the
way. This technique can be seen several times on the MIG-15
video here.
Take-off Dolly
This
wireless take-off Dolly was designed to be simple and flexible.
I made it from 1-1/4" PVC pipe, three end caps, a "T"-coupling
joint, Dubro 3.35" wheels, and gear mains from an old
.40-size Skylark pattern plane.
The
Spektrum AR6100
receiver could be bound to another club member's DSM2 transmitter
which would then follow the rudder channel for ground steering.
The
Velcro mounting technique allowed others to make their own
custom foam base and easily swap it without tools.
I
used a digital servo that could run on 3-12 volts so a regulator
was not needed. Both the receiver and digital servo could
run directly on a 2-cell LiPo pack.
The
disadvantage of a take-off Dolly is that it needs plenty
of plane power to get going. Thick grass provides excessive
resistance so it works best on dirt or pavement.
Hand Toss
The trick to determining whether you can successfully hand
toss a model is by looking at the wing loading, power level,
and thickness of the wing (or lift). If an EDF jet model is
designed to go over 100mph, you will not likely be able to
hand toss it. Smaller designs like the Exceed F/A-18C (above)
from Nitro
Planes can easily be hand tossed because it weighs only
2lbs and has plenty of power. Larger models like the 5.2lb
BAe Hawk (below) from FlyFly
Hobby can also be hand tossed because the wing loading
is light and the thick wing is designed for lift rather than
speed.
Digital Servoless Retracts
The
Digital Servoless Retract (DSR) system from Sonic
Electric is a revolutionary design suitable for
R/C models around 4-6lbs. (1.8-2.7kg) The retracts move
in a scale speed instead of the fast bang-bang manner
that air-powered systems exhibit.
The
DSR system is controlled via a Digital Control Box which
plugs into your receiver gear channel. You no longer
need an air canister, hand-pump, or controlling servo
for your retracts. The new metal arm version comes complete
and ready to use!
This
DSR-46C-A retract system comes with a metal arm pre-installed
on both the nose and main retracts. The metal arm is made
from light weight aluminum alloy which increase the system's
maximum loading and impact capability (over the older plastic
version) from 7 to 10lbs. In addition to the metal arm version,
the nose strut length has been increased and allows for some
adjustability. The main struts diameter also has been increased
and adjustable in length.
There
are three independent control circuits to detect the status
of each retract. An auto cut-off function will be started
if a retract is jammed after 20 seconds to avoid draining
the current from your Rx battery or BEC. You can use one servo
to connect to your rudder and the steerable nose unit. The
rudder will act independently while the strut is up because
the strut disengages. Nose struts can be turned 360 degrees
to suit most airplanes and the shock system is spring loaded.
The
photos on the right show the DSR system installed in a FlyFly
F-86 Sabre. A separate Hitec HS-55 servo is used for steering
the nose wheel. Although the retract assembly will fit perfectly
in the FlyFly model, the lower right photo shows how to distribute
the landing forces into the foam with thin plywood pieces.
The plywood can also be used to achieve the proper height
for the mounted retract. You can watch the DSR system operation
in our inverted FlyFly F-86 Sabre here.
EDF Conversions
Not
all jet models are created equal. Some of the reasons for
these differences are due to the unique needs of different
power sources. An EDF-powered jet needs more air intake area
than its turbine-powered counterpart. The turbine engine also
creates tremendous heat so the design must be capable of insulating
or deflecting areas that are sensitive to high temperature.
A GDF-powered (Glow Ducted Fan) jet needs to be built to handle
extra vibration and residue from the fuel oil. It also needs
more air intake than turbines.
This
Byron A-4 on the right belongs to Mark Willey of Erie, PA.
Mark completely refurbished his A-4 model including a new
Byron fan and O.S. 91. They were considered high-end for their
time.
The Byron A-4 above was also originally flown with the O.S.
91 engine shown. The stock 6" diameter fan put out between
10-12 lbs of thrust. This 15-20 year old fiberglass model
is now being converted to EDF. One reason that makes this
model attractive as an EDF conversion is that they can usually
be picked up at auctions for a relatively low cost. The air
intake openings for GDF are larger than needed for turbine-powered
jets but are a great fit for EDF. The new EDF components weigh
less than their original glow-powered counterparts. The engine
and fan shown above weigh in at 1.5lbs. When we added the
tuned pipe, Rx. battery pack, Byron duct unit, extra servos
for throttle and fuel mix change, we eliminated over 3.25lbs
not counting the slimy exhaust tube, 24oz fuel tank and 2oz
header tank. All in all, we estimate removing about 5lbs for
the GDF power system.
There
are many ways to convert glow-powered Byron jets to clean
and reliable electric power. Some can even exceed the original
performance. One way that is both cost-effective and similar
in power to the original glow-powered design is to simply
replace the glow engine with an electric motor while keeping
the Byron fan unit in place.
The
Byron fan was designed for about 20,000 RPMs using the O.S.91
engine or about 24,000 RPMs with a Hurricane rotor upgrade.
The design had plenty of static thrust but lacked on high-end
dynamic thrust. Still, the Byron F-16 could approach maximum
speeds of up to 120mph which is still respectable today.
This
Scorpion
HK-4035-630 outrunner motor is available at Electric
Jet Factory. When combined with the FS-ADAPTER1
CNC adapter (shown right), spacer,
and spinner,
you can easily convert the ICDF Byron Fan to EDF. Power system
setups vary based on application using ESC's between 90amp
& 110amps on 10s to 12s LiPo setups with a pack capacity
of between 5AH and 6.6AH. The result is a clean and reliable
electric-powered thrust from 10 to 12lbs.
Another way to convert a Byron GDF power system to EDF is
to completely replace the 6" fan with a more powerful
and efficient 5" fan. The E-Turbax fan from Jet
Hangar International can be purchased as a fully integrated
system or as individual components.
The
E-Turbax fan is a drop-in fit into any aircraft designed
for a 120mm (5") glow ducted fan. With the recommended
Neu
motor (1521/1.5Y or 1524/1.5Y or 1527/1.5Y), Castle
Creations Phoenix
HV-110 ESC, and 10s to 12s 6AH battery, this setup can
provide over 30,000 RPMs at 4500 watts for up to 15lbs of
thrust!
Although still a work in progress, I expect my Byron A-4
to be tearing up the skies in the 2009 flying season.
Summary
The
choices for EDF are both vast and exciting when you start
to venture off the beaten path. Newer EDF enthusiasts that
want to advance faster than the current mainstream market
allows can use the information in this column as a introduction
to some of the choices that are available today. The FlyFly
F-86 Sabre (on the right) has been re-painted and fitted
with the DSR retracts (discussed above) to demonstrate one
possible option of many that exist for these larger flexible
foam designs. One of the real joys of our hobby is that
you can tailor it to fit your own needs and desires.
High-powered
EDFs and Do-It-Yourself conversions aren't for everyone
as they can push the limits of today's technology, and your
skills, so always keep safety in mind! The on-line world
has plenty of experienced members that can help you when
needed, but it is usually best to look for a consensus of
opinion rather than listening only to the loudest voices.
When
you fly electric, fly clean, fly quiet, and fly safe!
Special thanks for contributions
by:
"Papa Jeff" Ring and Lynn Bowerman
This
section of AMP'D covers some of the questions that our
readers have sent in and I thought would be interesting
for others.
Roger
H. asks:
Hi
Greg,
I need some advice as I am very new
to electrics. I recently purchased a GWS Tiger Moth
400 and enjoyed reading your review. I purchased a Thunderpower
3-cell LiPo 1300mAh pack as suggested in your review.
Here is my question...I have a Triton Jr. charger and
while reading the instructions it mentions a cell balancer
is required for LiPo batteries. The Electrifly balancer
has a certain connector as part of the balancer. Will
the Thunderpower connector fit? Is there a pinout diagram
somewhere so I can make an adaptor? Is there another
comparable priced balancer that would work?
Any help would be appreciated.
Thanks, Roger
Greg:
Hi Roger,
The ElectriFly node connector is not compatible
with the ThunderPower connector. ElectriFly is
compatible with E-flite and ThunderPower is compatible
with FlightPower. To allow your Triton
Jr. charger to charge/balance your 3-cell
Thunderpower pack, you will also need to purchase
the Great Planes ElectriFly Equinox
LiPo Cell Balancer and the Equinox 3s
Adapter to FlightPower.
To
Charge/Balance ElectriFly and E-flite packs or
ThunderPower and FlightPower packs, I would also
recommend the following chargers and adapters.
E-flite (EFLC505)
1-5 Cell LiPo Charger with Balancer
E-flite (EFLA229)
Adapter Cables for ThunderPower/FlightPower
Can you provide an article, to get more informative about control surface throws, the rates/or exponential, and the meaning of large throws? That is to say, what about airloads on control surfaces at higher airspeeds, as with EDF and other (turbine) jets?
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