Park View: GWS-15 EDF - 2008/08

deal of prejudice concerning the F-15. I was
a member of the group that worked on its
aerodynamics, and I consider it to be “my”
airplane. I helped with some of the early
studies (using slide rules and punch cards
for computer input) and many of the windtunnel
tests (I always seemed to have the
night shifts!), hand-plotted test data (a big
yuck!), and worked on through the flighttesting
(although I was flying a desk).
Regardless of the boring part of
engineering, it was interesting to be a part of
the Eagle’s development and fine-tuning. I
can remember with excitement the
rollout in Saint Louis and the
suspense of the first test
flight. It was a good time
to be an engineer.
As the F-15’s
longitudinal and lateral
directional aerodynamic
stability and control
parameters were
measured in the
wind tunnel,
IN THE LATE 1960s and early 1970s, the
US Air Force needed a fighter capable of
operating at a performance level that would
allow it to counter the many highperformance
designs coming out of the
Russian design bureaus. The Air Force had
many airplanes flying at the time, but few
were of the air-combat variety.
The Navy’s F-4 Phantom was good in
the air-combat role, and consequently the
Air Force pressed it into service. However,
it had no air-to-air gun capability and
suffered a performance hit when considered
for the Air Force air-superiority role; it
carried the extra structural weight needed to
land on an aircraft carrier.
Later F-4 types were upgraded with a
gun, but the Phantom was getting close to
the end of its ability to counter the fast and
maneuverable Russian threats.
After several false starts, the Air Force
requested a study for an airplane—to be
called the F-15 Eagle—that would possess
the maneuverability and speed to guarantee
air superiority for many years. McDonnell
Douglas won the F-15 contract, and
MCAIR (McDonnell Aircraft Company) in
Saint Louis, Missouri, performed the design
work.
The aircraft’s design met the Air Force’s
performance requirements, but it had
something extra: that “quality” that
comes about when the design team
loves sexy airplanes. Its smooth
lines make it the best-looking
airplane of all time.
You must forgive me for having a great
76 MODEL AVIATION
BEN LANTERMAN
Park View: GWS-15 EDF
Build your own EDF from
this practical and fun kit
The all-gray F-15 needed more artistry to pull off the US Air Force daytime livery.
Acrylic paints won’t harm any of the model’s foam components.
The Photoshop picture-editing program has retracted the Gray F-15’s landing
gear and added clouds for effect. It is easy to see how effective the camouflage
paint scheme is in making this jet invisible.
the initial configuration was evaluated and
changed as required. For instance, the
vertical tail size was increased substantially
and the airfoil and wing planform was
optimized for speed and maneuverability.
Small changes, such as the notch in the LE
of the horizontal tail surface, were later
made based on flight-test results.
The full-scale design uses an all-flying
horizontal tail system for longitudinal
control and roll control. What GWS calls an
all-flying stabilizer, we called a stabilator.
To avoid confusion with the construction
manual, I will use
GWS’s terminology in
the rest of
the review.
The full-scale all-flying stabilizer and
aileron deflections used in flight are a
combination of pilot commands and an
onboard computer’s commands that are
scheduled as a function of flight conditions,
airplane angle of attack, all-flying stabilizer
deflections, etc. Since the model doesn’t
have onboard-computer capability, our
control-surface inputs will be limited to the
pilot’s commands based on visual cues and
experience.
The final full-scale Eagle performs well
over a large range of flight conditions and
angles of attack. Even when the flight
speeds are limited to those of our models,
the F-15 should be stable and maneuverable.
However, keep in mind that the F-15 wasn’t
designed to perform knife-edge flight or
tight outside loops!
Since I will never be able to afford a
turbine-powered F-15 (engineering didn’t
pay that much), having a flying model of the
aircraft seemed limited to something much
smaller than I might develop on my own
and would require a lot of work. When I saw
the ads for the Grand Wing Servo F-15—the
GWS-15—I immediately bought one.
As I built the kit, I thought others would
be interested in it, so I offered to write a
review for MA. In the process of
experimenting with different control
systems and evaluating construction
materials, I ended up buying three models!
You can never have too many.
The Models: This F-15 is not exact scale,
but it is close enough that no one except the
most fanatical Scale modeler with a ruler 78 MODEL AVIATION
The layout of the Gray F-15’s (with all-flying stabilizer) upper
fuselage before adding the lower fuselage half. The wiring along
the center into the forward fuselage is installed, and the motors
have heat sinks added.
The White F-15, with the conventional control layout and routing
of wiring from the ailerons. Power and elevator routing are along
the center fuselage in all configurations.
This shows the location of servos for the conventional elevator
configuration. The area of foam that needs to be cut out is
crosshatched. A small microservo has adequate power for the job.
The servo for the all-flying stabilizer is located in this position on
the fuselage. The area of foam that needs to be cut out is
crosshatched. Verify that you are removing the right foam chunk.
Wing-attach parts are easier to plug into
the fuselage sockets when the corners are
rounded, as shown. Ben made the F-15
wings that didn’t use ailerons removable.
The F-15 with wings attached will fit into a
normal car’s trunk.
The author installed the E-flite speed
controls with their heat sinks oriented to
allow inlet airflow over the cooling fins. He
used epoxy on their edges to hold them in
position.
The small wire stubs sticking out on the aft
part of the canopy are a portion of a 1/16-
inch wire that goes across the bottom of
the canopy assembly. These are used as a
handle to remove the assembly.
will notice. The fuselage lines are of the
full-scale baseline F-15 equipped with the
Conformal Fuel Tank. If you want to learn
more about the full-scale aircraft, do an
Internet search. There is ample information
about the GWS-15, including videos of it in
flight.
My first GWS-15 was the gray
camouflage version. (I’ll call it the Gray F-
15.) The box’s labeling had a check mark in
the square next to “EDF-2028” and a check
mark in the gray square. There are many
squares on the box, to designate the type of
model that is inside. The Gray F-15 was
constructed from a normal cooler type of
polystyrene that GWS calls “EPS.”
After finishing the Gray F-15, I saw that
an all-white version (that I’ll call the White
F-15) was available. The labeling on its box
had a check mark in the “EDF-2028” square
with a check mark in the white square. The
White F-15 was also constructed from EPS.
I decided to build the white version as
well, to check the alternate control system
that was offered. I thought it would look
great with the Edwards Air Force Base early
flight-test color scheme that includes
DayGlo red wingtips and tail surfaces.
After building these two airplanes, I
learned about a third version of the kit. It
had a check mark in the “NPS” square on
the box and a check mark in the white
square. That means there is No Power
System included and that it is made from a
white foam called EPO, which is flexible
and tough. (I’ll call this version the EPO F-
15.) The EPO F-15 kit weighs roughly 3
ounces more than the EPS versions, which
isn’t too bad considering the foam’s
toughness.
The EPO F-15 kit came with fans,
shrouds, and full wiring, but no motors. It
was probably offered as a Slope Soaring
airplane or for someone who wanted to use
a different motor. I bought two GWS motors
and assembled the propulsion units. Soon
the EPO F-15 became a part of the home
hangar, and I investigated a third control
system.
If you are buying one of these three
models, inspect the kits or talk to someone
to make sure you are getting what you want.
There are also options for a pusher-propeller
version. Seeing the propeller on the ground
detracts from the pure jet vision I wanted,
but it isn’t too noticeable in the air where it
counts.
The three F-15s gave me the opportunity
to investigate three control-system
possibilities. The Gray F-15 was built with
the all-flying stabilizer for pitch and roll
control. The ailerons were not used. The
White F-15 used a control option employing
fixed stabilizers, with conventional
elevators for pitch control and conventional
ailerons for roll control.
The EPO F-15 had the Gray F-15’s allflying-
stabilizer control system along with
the White F-15’s ailerons. This is closer to
the control system the full-scale F-15 has. I
was looking forward to seeing the difference
in flight characteristics.
I don’t define this kit as an ARF because
you do have to build it. It is first-rate and
comes with two nice ducted-fan units,
complete with quality brushless motors.
Also included are all the needed servo-wire
extensions, power-wire extensions, and
everything else that is required according to
the instructions.
There are many extra parts on the
molded plastic “trees”; use only the ones
required for this build and save the others
for another time. You have to supply glue, radio-control equipment, two ESCs, three or
four servos (depending on the control
options chosen), and flight batteries.
Equipment Used: I have purchased all the
F-15s and RC equipment I have used in this
review from my “RC modeling” cash fund.
Being retired and finding that the cash fund
is not a bottomless pit, I have to choose
equipment based on quality and price. But
other equipment will perform equally well.
It’s a good time to be in the RC hobby.
I chose the Spektrum DX7 radio system
for guidance. I have never had problems
with my 72 MHz systems I have used in
more than 50 airplanes; however, I did
manage to crash several park flyers while
using them.
I would get hot or distracted at the flying
field and forget to change the transmitter’s
memory to the appropriate model name.
Dumb, of course, but it did happen. It is a
funny feeling to see the airplane rolling left
and you bend the stick to the right. The
problems certainly would have been
prevented if I had used a preflight checklist,
but I didn’t. I can give no valid excuse.
When the Spektrum designers
developed the radio systems, they
apparently had a photo of me in front of
them. I still have excellent range and
reliability, but now I have no frequencyinterference
problems and (what I really
needed) Spektrum’s great Model Match
feature. I no longer toss a model into the
air and wonder why the ailerons aren’t
working the way I think they should.
With the Spektrum, the receiver is bound
to the particular model program. Therefore,
when I plug everything in and wonder why
nothing will work, I know to make sure I
have the correct model assigned. This is
such a great feature that I have purchased a
second transmitter. Finally I won’t be such a
menace at the Boeing Phantom Flyers club
field.
The model controlled with the all-flying
stabilizer is designed to use GWS Park
servos that fit precisely into the fuselage’s
premolded slots. Plastic fittings that couple
the all-flying stabilizers to their driving
servos are molded to fit the Park servo
output spines. Using another servo would
require a lot of adaptation.
If you do use a different servo, be sure to
check compatibility before permanently
gluing anything. Almost any microservo
will work with the conventional control
layout. I used small JR servos since I had
some and they fit the cutouts perfectly.
Since the propulsion system’s current
drain is close to 20 amps per motor and the
ESCs may be mounted in such a way that
might limit the cooling air available, I
chose the E-flite 25-Amp Pro Switch-Mode
BEC Brushless ESC. It is a good
compromise in price and capability and has
a large heat sink to aid in cooling. I needed
two of them: one for each motor.
The propulsion system’s total current
drain at the maximum power setting was
probably going to be close to 40 amps, so a
suitable-capacity three-cell Li-Poly battery
was necessary. I chose the FlightPower EVO
25 2500 mAh Li-Poly battery, which has a
25C rating. It is excellent but fairly
expensive. I also bought the E-flite 2100
mAh Li-Poly battery, which has a 20C rating
and is much easier on the modeling fund.
Both batteries will be working within
their advertised ratings. Don’t try to use a
low-rated 2100 mAh 10C battery; you won’t
get the necessary power and will likely
destroy the battery.
Construction: The manual has a minimal
number of words, but the drawings are clear.
Pay attention to the areas where cutting foam
for servos is required. Read carefully, look at
the drawings, and then, with parts in hand,
do a dry run of positioning and checking for
interference, fits, etc. Then review
everything again.
Make sure you are confident before
proceeding to any step, because the
conventional control configuration and allflying-
stabilizer control configurations are
intermixed within the manual. Because of
the model’s construction, it becomes next to
impossible to go back and fix things once
you glue the fuselage top to the fuselage
bottom.
The wiring diagrams are well done, and
you should have no problem setting up that
part of the airplane.
The F-15 goes together nicely because
everything fits well. A modeler who is
experienced enough to fly the airplane should be able to work his or her way
through the manual. However, there are
several things that might make the build
easier.
All the radio and propulsion parts are
installed in the upper fuselage half, so you
can fully check things out one last time
before permanently gluing on the bottom
fuselage half. The ducted fans fit into slotted
areas, and the wiring for them and the servos
are routed along the fuselage centerline.
Cavities were molded to allow the wires
to fit, but because I changed connectors,
there isn’t quite enough room for
everything. You may have to remove a bit of
foam to make things fit, but no strength loss
is involved.
As you arrange the wiring for the servos
and propulsion gear in the fuselage, use
small pieces of tape to hold the wires in
place. When all the wiring is positioned in
the top, the bottom of the fuselage is glued
on and the rest of the assembly goes fairly
quickly.
Before I started this project, I didn’t care
for the GWS glue. Although it hardens
nicely, it has an extremely long working
time and I get in a hurry. I changed my mind
when I assembled the upper and lower
fuselage halves; the adhesive provided the
working time to do this properly.
I used the GWS glue on everything in the
Gray F-15 and White F-15 assemblies and
had no problems. They are molded from the
82 MODEL AVIATION
standard GWS EPS material, which
dissolves when almost any kind of glue or
solvent other than the GWS adhesive is
used.
When using the GWS glue, plan your
building schedule so that main glue
interfaces, such as the top and bottom
fuselage halves or main spar inserts, can
set up overnight. It will make things seem
to go quickly.
Take the time while the glue is
hardening to read the manual. The glue can
also be used like a contact adhesive where
applicable.
I constructed the EPO F-15 with
regular cyanoacrylate glue. This type of
foam doesn’t melt with cyanoacrylate use,
and I think the bond is better than with the
GWS glue. Foam-safe cyanoacrylate
doesn’t stick as well to the EPO foam. I
encountered no problems with the regular
cyanoacrylate and built the airplane in two
days. Test any substitute glue on a
noncritical, out-of-the-way area.
The wing flight loads are carried into
the fuselage through three tube spars and
one square spar. You can remove the wing
by pushing on a tab attached to the square
spar.
I glued the socket parts into the
fuselage and the plug parts into the wing,
with no major attempt to align them to
each other. I just pushed the part firmly
into its appropriate molded cavity.
When I finally pushed the wing spars
into the fuselage sockets, I was happily
surprised to find that everything slid into
place perfectly. However, when it’s 95°
and sweat is in your eyes at the flying
field, it might be difficult to hit the holes.
You can make wing attachment easier by
sanding a semirounded point on the ends
of the wing tubes and using a drill to
slightly chamfer the holes in the fuselage
sockets.
The canopy-latch mechanism was a
tight snap fit when I checked it before
installation. I had doubts that I could
remove the canopy without damaging the
canopy’s foam base using the supplied
parts.
I finally gave up on the supplied latch
parts and used 3/8-inch-diameter
neodymium magnets to attach the canopy
assembly. Just glue the magnets into the
foam at the front and rear of the canopy
with the appropriate glue or epoxy.
(Remember to check foam/glue
compatibility.)
Some sort of handle at the aft part of
the canopy is recommended to make
removal easier. I glued a piece of 1/16-inchdiameter
piano wire across the underside
of the aft part of the canopy assembly. I
allowed approximately 1/4 inch to stick out
on each side of the canopy base. I pull up
on each of the nearly invisible wire ends to
unlatch.
Don’t forget to add a pilot before
gluing the canopy on its base. It would be
nice if GWS included a pilot bust in the
kit.
I used the fixed-landing-gear option on
all my F-15s. I have seen videos of awful
hand launches of the model that
demonstrated its great recovery
characteristics. I thought it would be
difficult to hand launch because of the large
flat bottom and my small hands. The
landing gear will work fine on the beautiful
runway at the Boeing Phantom Flyers field.
The manual indicated that the CG
should be 160mm plus or minus 5mm aft of
the lower lip of the inlet. My F-15s’ CGs
came out within 1mm or 2mm of the
required 160mm mark when the ESCs were
installed roughly halfway in the inlet
ducting wall and with the battery installed.
The construction manual’s diagrams do
a nice job of illustrating the control-system
setups. To set up the EPO F-15’s
configuration, I installed the all-flying
stabilizer setup as used in the Gray F-15
and then put a servo splitter in the
Spektrum AR6100 receiver AUX port for
the aileron input. This may seem to make
the aileron servos move in the same
direction on the bench, but everything
works in the appropriate direction when the
servos are installed in the wing cutouts.
I don’t have information to answer
questions about any other type of radio
system. Make sure things work
correctly before fixing the servos
permanently in place. Set the initial
control-surface throws to those shown
for your setup in the manual.
The airplane looks good at this point,
but it would be great if GWS included a
bottle of touch-up paint in the gray kit. The
existing paint film is thin and easily
damaged during construction. Cover your
building area with soft materials to protect
the models.
I mixed some gray colors using artist’s
acrylic paint to touch up the construction
nicks and camouflage markings. Test any
paint for foam compatibility, and wash the
areas to be painted with alcohol or soapy
water.
For the White F-15’s Edwards Air Force
Base flight-testing paint scheme, I used
Faskolor acrylic Fasfluorescent Red that I
bought at Mark Twain Hobbies in Saint
Charles, Missouri. Having a hobby shop of
this quality a few miles from my home is
great. The prices are competitive, and the
staff is knowledgeable and friendly. Mailorder
hobby sources are fine, but we need
to keep our local hobby shops in business.
I have one major complaint. The plastic
parts used to mount the all-flying stabilizer
and vertical tails were black—big, black,
plastic, clunky parts. Why not mold them in
a nice gray or white, to match the airplane?
The construction manual presents a
range of flying weights between 28.3 and
35.3 ounces. It suggests using a 1.3- to 1.8-
amp-hour Li-Poly battery of greater than
15C capability for power. I think a battery
with that low of a capacity will have a hard
time delivering the required power to the
ducted fans.
The final weights of my models with
no batteries were: Gray F-15, 32 ounces;
White F-15, 31 ounces; EPO F-15, 36
ounces. Its weight was because of the extra
weight of the foam type used.
Propulsion Tests: With a freshly charged
battery that was capable of delivering full
power to the system, the initial power
input was roughly 500 watts (measured
with an AstroFlight Whattmeter). That is
49 amps at 10.3 volts (voltage under full
load).
This voltage drop from the battery’s
fully charged resting voltage of more than
12 volts is typical of a Li-Poly battery
delivering high power relative to its
capacity. And the power available
throughout the motor run will be much less
than these initial measurements as the
battery discharges to the preset ESC cutoff
voltage.
Those 500 watts convert to an initial
measured static thrust of roughly 32
ounces. In-flight thrust will be less and
will drop from 30 to 20 ounces or so.
This thrust-to-weight ratio isn’t too
bad, and you do have maximum power at
takeoff. You might be unable to hover and
torque roll, but this is a ducted-fan scale
model of an F-15 for a reasonable price.
Flight Notes: Even with my rusty reflexes
and the cold weather, I found the GWS F-
15 to be delightful, fast, and smooth-flying
in all configurations. The only problem I
had was pulling back on the throttle once
the F-15 was in the air. Although it flew
nicely at lower speeds, it was way too
much fun to perform the entire flight with
full power.
My flight tests indicated that the
control-surface throws recommended in
the construction manual were well suited
to the model at the recommended CG.
Since the airplane didn’t seem twitchy,
you can fly it with a four-channel
transmitter that doesn’t have exponential
capability. However, if you have that
feature you can add exponential to suit
your preferences as you gain experience
with the airplane.
Takeoffs with the Gray F-15 and the
EPO F-15 were smooth and easy to
control. Setting the controls neutral so the
all-flying stabilizer faired with the fixed
part of the stabilizer mounted on the
fuselage was a good starting point. The
change in neutral control required for
actual level flight was a bit of up-elevator
trim.
Roll trim setting was almost on too.
There was no problem in trimming the
models.
During the White F-15’s first takeoff
with the conventional elevator for pitch
control, I had the transmitter settings to the
low control rates. I found that I didn’t have
enough back stick to rotate the model. I had set the high-rate throw to the throw
shown in the manual, and the low-rate throw
was set to approximately half that—my
mistake.
So I cut off the power on the model and
let it run off into the grass at the end of the
runway. In the process, the first 1/2 inch or
so of the nose cone broke off.
Low control-rate throws should start at
the manual’s recommended settings. Then
you can set the high throws higher than that.
When comparing the all-flying stabilizer
(Gray F-15) to the all-flying-stabilizer-plusaileron
configurations (EPO F-15), I found
that the all-flying stabilizer’s roll-control
authority is good enough that the ailerons
aren’t needed. The all-flying stabilizer also
seems more effective in pitch control than
the conventional elevator. I am looking
forward to more experimentation with all
these control systems.
The Gray F-15’s first landing was good,
but it did run out onto the short grass at the
end of the runway. This resulted in roughly
the first 1/2 inch of the nose cone’s breaking
off, as happened with the White F-15.
I didn’t think the landing was too fast,
but I was noticing a trend with the nosecone
tips. I didn’t know grass was that hard,
but it was freezing.
The EPO F-15’s landing was nice and
smooth but a bit long, and after a long
runout it was into the grass. At least the nose
cone stayed intact. So it wasn’t the grass
breaking the nose off; it was because of the
weak foam.
This should lead to a modification of the
standard kit. Replace the nose cones made from
the Styrofoam-type material with the EPO.
The other result of the trip to the flying
field was a fuselage broken in half midway
under the canopy. This happened when my
helper picked up the White F-15—but I
need to clarify that.
Most helpers and modelers have learned
to pick up a model with one hand under the
wing or fuselage near the CG and the other
hand on the nose to steady the airplane. We
might lift with considerable force on the
nose because it is often the strongest part of
the model. When you do that with this F-15,
it puts pressure on the nose in the weakest
part until it breaks at a point approximately
halfway back from the front of the canopy.
I will use carbon-fiber mat or something
similar with epoxy to strengthen the inside
of the fuselage on each side along this area.
I recommend that you do so too.
I really do like this model, how it looks,
and how it flies. I recommend it to any
experienced flier. MA
Ben Lanterman
[email protected]
Manufacturer/Distributor:
Grand Wing System U.S.A. Inc.
138 S. Brent Cir.
City of Industry CA 91789
(909) 594-4979
www.gwsus.com
Sources:
E-flite
(800) 338-4639
www.e-fliterc.com
FlightPower
(800) 637-7660
www.bestrc.com/flightpower/
Spektrum
(800) 338-4639
www.spektrumrc.com
Online Forum and Video:
www.rcgroups.com/forums/showthread.php
?t=682816
Other Review Articles:
Aviation Modeler International: May 2008
Quiet Flyer: December 2007

deal of prejudice concerning the F-15. I was
a member of the group that worked on its
aerodynamics, and I consider it to be “my”
airplane. I helped with some of the early
studies (using slide rules and punch cards
for computer input) and many of the windtunnel
tests (I always seemed to have the
night shifts!), hand-plotted test data (a big
yuck!), and worked on through the flighttesting
(although I was flying a desk).
Regardless of the boring part of
engineering, it was interesting to be a part of
the Eagle’s development and fine-tuning. I
can remember with excitement the
rollout in Saint Louis and the
suspense of the first test
flight. It was a good time
to be an engineer.
As the F-15’s
longitudinal and lateral
directional aerodynamic
stability and control
parameters were
measured in the
wind tunnel,
IN THE LATE 1960s and early 1970s, the
US Air Force needed a fighter capable of
operating at a performance level that would
allow it to counter the many highperformance
designs coming out of the
Russian design bureaus. The Air Force had
many airplanes flying at the time, but few
were of the air-combat variety.
The Navy’s F-4 Phantom was good in
the air-combat role, and consequently the
Air Force pressed it into service. However,
it had no air-to-air gun capability and
suffered a performance hit when considered
for the Air Force air-superiority role; it
carried the extra structural weight needed to
land on an aircraft carrier.
Later F-4 types were upgraded with a
gun, but the Phantom was getting close to
the end of its ability to counter the fast and
maneuverable Russian threats.
After several false starts, the Air Force
requested a study for an airplane—to be
called the F-15 Eagle—that would possess
the maneuverability and speed to guarantee
air superiority for many years. McDonnell
Douglas won the F-15 contract, and
MCAIR (McDonnell Aircraft Company) in
Saint Louis, Missouri, performed the design
work.
The aircraft’s design met the Air Force’s
performance requirements, but it had
something extra: that “quality” that
comes about when the design team
loves sexy airplanes. Its smooth
lines make it the best-looking
airplane of all time.
You must forgive me for having a great
76 MODEL AVIATION
BEN LANTERMAN
Park View: GWS-15 EDF
Build your own EDF from
this practical and fun kit
The all-gray F-15 needed more artistry to pull off the US Air Force daytime livery.
Acrylic paints won’t harm any of the model’s foam components.
The Photoshop picture-editing program has retracted the Gray F-15’s landing
gear and added clouds for effect. It is easy to see how effective the camouflage
paint scheme is in making this jet invisible.
the initial configuration was evaluated and
changed as required. For instance, the
vertical tail size was increased substantially
and the airfoil and wing planform was
optimized for speed and maneuverability.
Small changes, such as the notch in the LE
of the horizontal tail surface, were later
made based on flight-test results.
The full-scale design uses an all-flying
horizontal tail system for longitudinal
control and roll control. What GWS calls an
all-flying stabilizer, we called a stabilator.
To avoid confusion with the construction
manual, I will use
GWS’s terminology in
the rest of
the review.
The full-scale all-flying stabilizer and
aileron deflections used in flight are a
combination of pilot commands and an
onboard computer’s commands that are
scheduled as a function of flight conditions,
airplane angle of attack, all-flying stabilizer
deflections, etc. Since the model doesn’t
have onboard-computer capability, our
control-surface inputs will be limited to the
pilot’s commands based on visual cues and
experience.
The final full-scale Eagle performs well
over a large range of flight conditions and
angles of attack. Even when the flight
speeds are limited to those of our models,
the F-15 should be stable and maneuverable.
However, keep in mind that the F-15 wasn’t
designed to perform knife-edge flight or
tight outside loops!
Since I will never be able to afford a
turbine-powered F-15 (engineering didn’t
pay that much), having a flying model of the
aircraft seemed limited to something much
smaller than I might develop on my own
and would require a lot of work. When I saw
the ads for the Grand Wing Servo F-15—the
GWS-15—I immediately bought one.
As I built the kit, I thought others would
be interested in it, so I offered to write a
review for MA. In the process of
experimenting with different control
systems and evaluating construction
materials, I ended up buying three models!
You can never have too many.
The Models: This F-15 is not exact scale,
but it is close enough that no one except the
most fanatical Scale modeler with a ruler 78 MODEL AVIATION
The layout of the Gray F-15’s (with all-flying stabilizer) upper
fuselage before adding the lower fuselage half. The wiring along
the center into the forward fuselage is installed, and the motors
have heat sinks added.
The White F-15, with the conventional control layout and routing
of wiring from the ailerons. Power and elevator routing are along
the center fuselage in all configurations.
This shows the location of servos for the conventional elevator
configuration. The area of foam that needs to be cut out is
crosshatched. A small microservo has adequate power for the job.
The servo for the all-flying stabilizer is located in this position on
the fuselage. The area of foam that needs to be cut out is
crosshatched. Verify that you are removing the right foam chunk.
Wing-attach parts are easier to plug into
the fuselage sockets when the corners are
rounded, as shown. Ben made the F-15
wings that didn’t use ailerons removable.
The F-15 with wings attached will fit into a
normal car’s trunk.
The author installed the E-flite speed
controls with their heat sinks oriented to
allow inlet airflow over the cooling fins. He
used epoxy on their edges to hold them in
position.
The small wire stubs sticking out on the aft
part of the canopy are a portion of a 1/16-
inch wire that goes across the bottom of
the canopy assembly. These are used as a
handle to remove the assembly.
will notice. The fuselage lines are of the
full-scale baseline F-15 equipped with the
Conformal Fuel Tank. If you want to learn
more about the full-scale aircraft, do an
Internet search. There is ample information
about the GWS-15, including videos of it in
flight.
My first GWS-15 was the gray
camouflage version. (I’ll call it the Gray F-
15.) The box’s labeling had a check mark in
the square next to “EDF-2028” and a check
mark in the gray square. There are many
squares on the box, to designate the type of
model that is inside. The Gray F-15 was
constructed from a normal cooler type of
polystyrene that GWS calls “EPS.”
After finishing the Gray F-15, I saw that
an all-white version (that I’ll call the White
F-15) was available. The labeling on its box
had a check mark in the “EDF-2028” square
with a check mark in the white square. The
White F-15 was also constructed from EPS.
I decided to build the white version as
well, to check the alternate control system
that was offered. I thought it would look
great with the Edwards Air Force Base early
flight-test color scheme that includes
DayGlo red wingtips and tail surfaces.
After building these two airplanes, I
learned about a third version of the kit. It
had a check mark in the “NPS” square on
the box and a check mark in the white
square. That means there is No Power
System included and that it is made from a
white foam called EPO, which is flexible
and tough. (I’ll call this version the EPO F-
15.) The EPO F-15 kit weighs roughly 3
ounces more than the EPS versions, which
isn’t too bad considering the foam’s
toughness.
The EPO F-15 kit came with fans,
shrouds, and full wiring, but no motors. It
was probably offered as a Slope Soaring
airplane or for someone who wanted to use
a different motor. I bought two GWS motors
and assembled the propulsion units. Soon
the EPO F-15 became a part of the home
hangar, and I investigated a third control
system.
If you are buying one of these three
models, inspect the kits or talk to someone
to make sure you are getting what you want.
There are also options for a pusher-propeller
version. Seeing the propeller on the ground
detracts from the pure jet vision I wanted,
but it isn’t too noticeable in the air where it
counts.
The three F-15s gave me the opportunity
to investigate three control-system
possibilities. The Gray F-15 was built with
the all-flying stabilizer for pitch and roll
control. The ailerons were not used. The
White F-15 used a control option employing
fixed stabilizers, with conventional
elevators for pitch control and conventional
ailerons for roll control.
The EPO F-15 had the Gray F-15’s allflying-
stabilizer control system along with
the White F-15’s ailerons. This is closer to
the control system the full-scale F-15 has. I
was looking forward to seeing the difference
in flight characteristics.
I don’t define this kit as an ARF because
you do have to build it. It is first-rate and
comes with two nice ducted-fan units,
complete with quality brushless motors.
Also included are all the needed servo-wire
extensions, power-wire extensions, and
everything else that is required according to
the instructions.
There are many extra parts on the
molded plastic “trees”; use only the ones
required for this build and save the others
for another time. You have to supply glue, radio-control equipment, two ESCs, three or
four servos (depending on the control
options chosen), and flight batteries.
Equipment Used: I have purchased all the
F-15s and RC equipment I have used in this
review from my “RC modeling” cash fund.
Being retired and finding that the cash fund
is not a bottomless pit, I have to choose
equipment based on quality and price. But
other equipment will perform equally well.
It’s a good time to be in the RC hobby.
I chose the Spektrum DX7 radio system
for guidance. I have never had problems
with my 72 MHz systems I have used in
more than 50 airplanes; however, I did
manage to crash several park flyers while
using them.
I would get hot or distracted at the flying
field and forget to change the transmitter’s
memory to the appropriate model name.
Dumb, of course, but it did happen. It is a
funny feeling to see the airplane rolling left
and you bend the stick to the right. The
problems certainly would have been
prevented if I had used a preflight checklist,
but I didn’t. I can give no valid excuse.
When the Spektrum designers
developed the radio systems, they
apparently had a photo of me in front of
them. I still have excellent range and
reliability, but now I have no frequencyinterference
problems and (what I really
needed) Spektrum’s great Model Match
feature. I no longer toss a model into the
air and wonder why the ailerons aren’t
working the way I think they should.
With the Spektrum, the receiver is bound
to the particular model program. Therefore,
when I plug everything in and wonder why
nothing will work, I know to make sure I
have the correct model assigned. This is
such a great feature that I have purchased a
second transmitter. Finally I won’t be such a
menace at the Boeing Phantom Flyers club
field.
The model controlled with the all-flying
stabilizer is designed to use GWS Park
servos that fit precisely into the fuselage’s
premolded slots. Plastic fittings that couple
the all-flying stabilizers to their driving
servos are molded to fit the Park servo
output spines. Using another servo would
require a lot of adaptation.
If you do use a different servo, be sure to
check compatibility before permanently
gluing anything. Almost any microservo
will work with the conventional control
layout. I used small JR servos since I had
some and they fit the cutouts perfectly.
Since the propulsion system’s current
drain is close to 20 amps per motor and the
ESCs may be mounted in such a way that
might limit the cooling air available, I
chose the E-flite 25-Amp Pro Switch-Mode
BEC Brushless ESC. It is a good
compromise in price and capability and has
a large heat sink to aid in cooling. I needed
two of them: one for each motor.
The propulsion system’s total current
drain at the maximum power setting was
probably going to be close to 40 amps, so a
suitable-capacity three-cell Li-Poly battery
was necessary. I chose the FlightPower EVO
25 2500 mAh Li-Poly battery, which has a
25C rating. It is excellent but fairly
expensive. I also bought the E-flite 2100
mAh Li-Poly battery, which has a 20C rating
and is much easier on the modeling fund.
Both batteries will be working within
their advertised ratings. Don’t try to use a
low-rated 2100 mAh 10C battery; you won’t
get the necessary power and will likely
destroy the battery.
Construction: The manual has a minimal
number of words, but the drawings are clear.
Pay attention to the areas where cutting foam
for servos is required. Read carefully, look at
the drawings, and then, with parts in hand,
do a dry run of positioning and checking for
interference, fits, etc. Then review
everything again.
Make sure you are confident before
proceeding to any step, because the
conventional control configuration and allflying-
stabilizer control configurations are
intermixed within the manual. Because of
the model’s construction, it becomes next to
impossible to go back and fix things once
you glue the fuselage top to the fuselage
bottom.
The wiring diagrams are well done, and
you should have no problem setting up that
part of the airplane.
The F-15 goes together nicely because
everything fits well. A modeler who is
experienced enough to fly the airplane should be able to work his or her way
through the manual. However, there are
several things that might make the build
easier.
All the radio and propulsion parts are
installed in the upper fuselage half, so you
can fully check things out one last time
before permanently gluing on the bottom
fuselage half. The ducted fans fit into slotted
areas, and the wiring for them and the servos
are routed along the fuselage centerline.
Cavities were molded to allow the wires
to fit, but because I changed connectors,
there isn’t quite enough room for
everything. You may have to remove a bit of
foam to make things fit, but no strength loss
is involved.
As you arrange the wiring for the servos
and propulsion gear in the fuselage, use
small pieces of tape to hold the wires in
place. When all the wiring is positioned in
the top, the bottom of the fuselage is glued
on and the rest of the assembly goes fairly
quickly.
Before I started this project, I didn’t care
for the GWS glue. Although it hardens
nicely, it has an extremely long working
time and I get in a hurry. I changed my mind
when I assembled the upper and lower
fuselage halves; the adhesive provided the
working time to do this properly.
I used the GWS glue on everything in the
Gray F-15 and White F-15 assemblies and
had no problems. They are molded from the
82 MODEL AVIATION
standard GWS EPS material, which
dissolves when almost any kind of glue or
solvent other than the GWS adhesive is
used.
When using the GWS glue, plan your
building schedule so that main glue
interfaces, such as the top and bottom
fuselage halves or main spar inserts, can
set up overnight. It will make things seem
to go quickly.
Take the time while the glue is
hardening to read the manual. The glue can
also be used like a contact adhesive where
applicable.
I constructed the EPO F-15 with
regular cyanoacrylate glue. This type of
foam doesn’t melt with cyanoacrylate use,
and I think the bond is better than with the
GWS glue. Foam-safe cyanoacrylate
doesn’t stick as well to the EPO foam. I
encountered no problems with the regular
cyanoacrylate and built the airplane in two
days. Test any substitute glue on a
noncritical, out-of-the-way area.
The wing flight loads are carried into
the fuselage through three tube spars and
one square spar. You can remove the wing
by pushing on a tab attached to the square
spar.
I glued the socket parts into the
fuselage and the plug parts into the wing,
with no major attempt to align them to
each other. I just pushed the part firmly
into its appropriate molded cavity.
When I finally pushed the wing spars
into the fuselage sockets, I was happily
surprised to find that everything slid into
place perfectly. However, when it’s 95°
and sweat is in your eyes at the flying
field, it might be difficult to hit the holes.
You can make wing attachment easier by
sanding a semirounded point on the ends
of the wing tubes and using a drill to
slightly chamfer the holes in the fuselage
sockets.
The canopy-latch mechanism was a
tight snap fit when I checked it before
installation. I had doubts that I could
remove the canopy without damaging the
canopy’s foam base using the supplied
parts.
I finally gave up on the supplied latch
parts and used 3/8-inch-diameter
neodymium magnets to attach the canopy
assembly. Just glue the magnets into the
foam at the front and rear of the canopy
with the appropriate glue or epoxy.
(Remember to check foam/glue
compatibility.)
Some sort of handle at the aft part of
the canopy is recommended to make
removal easier. I glued a piece of 1/16-inchdiameter
piano wire across the underside
of the aft part of the canopy assembly. I
allowed approximately 1/4 inch to stick out
on each side of the canopy base. I pull up
on each of the nearly invisible wire ends to
unlatch.
Don’t forget to add a pilot before
gluing the canopy on its base. It would be
nice if GWS included a pilot bust in the
kit.
I used the fixed-landing-gear option on
all my F-15s. I have seen videos of awful
hand launches of the model that
demonstrated its great recovery
characteristics. I thought it would be
difficult to hand launch because of the large
flat bottom and my small hands. The
landing gear will work fine on the beautiful
runway at the Boeing Phantom Flyers field.
The manual indicated that the CG
should be 160mm plus or minus 5mm aft of
the lower lip of the inlet. My F-15s’ CGs
came out within 1mm or 2mm of the
required 160mm mark when the ESCs were
installed roughly halfway in the inlet
ducting wall and with the battery installed.
The construction manual’s diagrams do
a nice job of illustrating the control-system
setups. To set up the EPO F-15’s
configuration, I installed the all-flying
stabilizer setup as used in the Gray F-15
and then put a servo splitter in the
Spektrum AR6100 receiver AUX port for
the aileron input. This may seem to make
the aileron servos move in the same
direction on the bench, but everything
works in the appropriate direction when the
servos are installed in the wing cutouts.
I don’t have information to answer
questions about any other type of radio
system. Make sure things work
correctly before fixing the servos
permanently in place. Set the initial
control-surface throws to those shown
for your setup in the manual.
The airplane looks good at this point,
but it would be great if GWS included a
bottle of touch-up paint in the gray kit. The
existing paint film is thin and easily
damaged during construction. Cover your
building area with soft materials to protect
the models.
I mixed some gray colors using artist’s
acrylic paint to touch up the construction
nicks and camouflage markings. Test any
paint for foam compatibility, and wash the
areas to be painted with alcohol or soapy
water.
For the White F-15’s Edwards Air Force
Base flight-testing paint scheme, I used
Faskolor acrylic Fasfluorescent Red that I
bought at Mark Twain Hobbies in Saint
Charles, Missouri. Having a hobby shop of
this quality a few miles from my home is
great. The prices are competitive, and the
staff is knowledgeable and friendly. Mailorder
hobby sources are fine, but we need
to keep our local hobby shops in business.
I have one major complaint. The plastic
parts used to mount the all-flying stabilizer
and vertical tails were black—big, black,
plastic, clunky parts. Why not mold them in
a nice gray or white, to match the airplane?
The construction manual presents a
range of flying weights between 28.3 and
35.3 ounces. It suggests using a 1.3- to 1.8-
amp-hour Li-Poly battery of greater than
15C capability for power. I think a battery
with that low of a capacity will have a hard
time delivering the required power to the
ducted fans.
The final weights of my models with
no batteries were: Gray F-15, 32 ounces;
White F-15, 31 ounces; EPO F-15, 36
ounces. Its weight was because of the extra
weight of the foam type used.
Propulsion Tests: With a freshly charged
battery that was capable of delivering full
power to the system, the initial power
input was roughly 500 watts (measured
with an AstroFlight Whattmeter). That is
49 amps at 10.3 volts (voltage under full
load).
This voltage drop from the battery’s
fully charged resting voltage of more than
12 volts is typical of a Li-Poly battery
delivering high power relative to its
capacity. And the power available
throughout the motor run will be much less
than these initial measurements as the
battery discharges to the preset ESC cutoff
voltage.
Those 500 watts convert to an initial
measured static thrust of roughly 32
ounces. In-flight thrust will be less and
will drop from 30 to 20 ounces or so.
This thrust-to-weight ratio isn’t too
bad, and you do have maximum power at
takeoff. You might be unable to hover and
torque roll, but this is a ducted-fan scale
model of an F-15 for a reasonable price.
Flight Notes: Even with my rusty reflexes
and the cold weather, I found the GWS F-
15 to be delightful, fast, and smooth-flying
in all configurations. The only problem I
had was pulling back on the throttle once
the F-15 was in the air. Although it flew
nicely at lower speeds, it was way too
much fun to perform the entire flight with
full power.
My flight tests indicated that the
control-surface throws recommended in
the construction manual were well suited
to the model at the recommended CG.
Since the airplane didn’t seem twitchy,
you can fly it with a four-channel
transmitter that doesn’t have exponential
capability. However, if you have that
feature you can add exponential to suit
your preferences as you gain experience
with the airplane.
Takeoffs with the Gray F-15 and the
EPO F-15 were smooth and easy to
control. Setting the controls neutral so the
all-flying stabilizer faired with the fixed
part of the stabilizer mounted on the
fuselage was a good starting point. The
change in neutral control required for
actual level flight was a bit of up-elevator
trim.
Roll trim setting was almost on too.
There was no problem in trimming the
models.
During the White F-15’s first takeoff
with the conventional elevator for pitch
control, I had the transmitter settings to the
low control rates. I found that I didn’t have
enough back stick to rotate the model. I had set the high-rate throw to the throw
shown in the manual, and the low-rate throw
was set to approximately half that—my
mistake.
So I cut off the power on the model and
let it run off into the grass at the end of the
runway. In the process, the first 1/2 inch or
so of the nose cone broke off.
Low control-rate throws should start at
the manual’s recommended settings. Then
you can set the high throws higher than that.
When comparing the all-flying stabilizer
(Gray F-15) to the all-flying-stabilizer-plusaileron
configurations (EPO F-15), I found
that the all-flying stabilizer’s roll-control
authority is good enough that the ailerons
aren’t needed. The all-flying stabilizer also
seems more effective in pitch control than
the conventional elevator. I am looking
forward to more experimentation with all
these control systems.
The Gray F-15’s first landing was good,
but it did run out onto the short grass at the
end of the runway. This resulted in roughly
the first 1/2 inch of the nose cone’s breaking
off, as happened with the White F-15.
I didn’t think the landing was too fast,
but I was noticing a trend with the nosecone
tips. I didn’t know grass was that hard,
but it was freezing.
The EPO F-15’s landing was nice and
smooth but a bit long, and after a long
runout it was into the grass. At least the nose
cone stayed intact. So it wasn’t the grass
breaking the nose off; it was because of the
weak foam.
This should lead to a modification of the
standard kit. Replace the nose cones made from
the Styrofoam-type material with the EPO.
The other result of the trip to the flying
field was a fuselage broken in half midway
under the canopy. This happened when my
helper picked up the White F-15—but I
need to clarify that.
Most helpers and modelers have learned
to pick up a model with one hand under the
wing or fuselage near the CG and the other
hand on the nose to steady the airplane. We
might lift with considerable force on the
nose because it is often the strongest part of
the model. When you do that with this F-15,
it puts pressure on the nose in the weakest
part until it breaks at a point approximately
halfway back from the front of the canopy.
I will use carbon-fiber mat or something
similar with epoxy to strengthen the inside
of the fuselage on each side along this area.
I recommend that you do so too.
I really do like this model, how it looks,
and how it flies. I recommend it to any
experienced flier. MA
Ben Lanterman
[email protected]
Manufacturer/Distributor:
Grand Wing System U.S.A. Inc.
138 S. Brent Cir.
City of Industry CA 91789
(909) 594-4979
www.gwsus.com
Sources:
E-flite
(800) 338-4639
www.e-fliterc.com
FlightPower
(800) 637-7660
www.bestrc.com/flightpower/
Spektrum
(800) 338-4639
www.spektrumrc.com
Online Forum and Video:
www.rcgroups.com/forums/showthread.php
?t=682816
Other Review Articles:
Aviation Modeler International: May 2008
Quiet Flyer: December 2007

deal of prejudice concerning the F-15. I was
a member of the group that worked on its
aerodynamics, and I consider it to be “my”
airplane. I helped with some of the early
studies (using slide rules and punch cards
for computer input) and many of the windtunnel
tests (I always seemed to have the
night shifts!), hand-plotted test data (a big
yuck!), and worked on through the flighttesting
(although I was flying a desk).
Regardless of the boring part of
engineering, it was interesting to be a part of
the Eagle’s development and fine-tuning. I
can remember with excitement the
rollout in Saint Louis and the
suspense of the first test
flight. It was a good time
to be an engineer.
As the F-15’s
longitudinal and lateral
directional aerodynamic
stability and control
parameters were
measured in the
wind tunnel,
IN THE LATE 1960s and early 1970s, the
US Air Force needed a fighter capable of
operating at a performance level that would
allow it to counter the many highperformance
designs coming out of the
Russian design bureaus. The Air Force had
many airplanes flying at the time, but few
were of the air-combat variety.
The Navy’s F-4 Phantom was good in
the air-combat role, and consequently the
Air Force pressed it into service. However,
it had no air-to-air gun capability and
suffered a performance hit when considered
for the Air Force air-superiority role; it
carried the extra structural weight needed to
land on an aircraft carrier.
Later F-4 types were upgraded with a
gun, but the Phantom was getting close to
the end of its ability to counter the fast and
maneuverable Russian threats.
After several false starts, the Air Force
requested a study for an airplane—to be
called the F-15 Eagle—that would possess
the maneuverability and speed to guarantee
air superiority for many years. McDonnell
Douglas won the F-15 contract, and
MCAIR (McDonnell Aircraft Company) in
Saint Louis, Missouri, performed the design
work.
The aircraft’s design met the Air Force’s
performance requirements, but it had
something extra: that “quality” that
comes about when the design team
loves sexy airplanes. Its smooth
lines make it the best-looking
airplane of all time.
You must forgive me for having a great
76 MODEL AVIATION
BEN LANTERMAN
Park View: GWS-15 EDF
Build your own EDF from
this practical and fun kit
The all-gray F-15 needed more artistry to pull off the US Air Force daytime livery.
Acrylic paints won’t harm any of the model’s foam components.
The Photoshop picture-editing program has retracted the Gray F-15’s landing
gear and added clouds for effect. It is easy to see how effective the camouflage
paint scheme is in making this jet invisible.
the initial configuration was evaluated and
changed as required. For instance, the
vertical tail size was increased substantially
and the airfoil and wing planform was
optimized for speed and maneuverability.
Small changes, such as the notch in the LE
of the horizontal tail surface, were later
made based on flight-test results.
The full-scale design uses an all-flying
horizontal tail system for longitudinal
control and roll control. What GWS calls an
all-flying stabilizer, we called a stabilator.
To avoid confusion with the construction
manual, I will use
GWS’s terminology in
the rest of
the review.
The full-scale all-flying stabilizer and
aileron deflections used in flight are a
combination of pilot commands and an
onboard computer’s commands that are
scheduled as a function of flight conditions,
airplane angle of attack, all-flying stabilizer
deflections, etc. Since the model doesn’t
have onboard-computer capability, our
control-surface inputs will be limited to the
pilot’s commands based on visual cues and
experience.
The final full-scale Eagle performs well
over a large range of flight conditions and
angles of attack. Even when the flight
speeds are limited to those of our models,
the F-15 should be stable and maneuverable.
However, keep in mind that the F-15 wasn’t
designed to perform knife-edge flight or
tight outside loops!
Since I will never be able to afford a
turbine-powered F-15 (engineering didn’t
pay that much), having a flying model of the
aircraft seemed limited to something much
smaller than I might develop on my own
and would require a lot of work. When I saw
the ads for the Grand Wing Servo F-15—the
GWS-15—I immediately bought one.
As I built the kit, I thought others would
be interested in it, so I offered to write a
review for MA. In the process of
experimenting with different control
systems and evaluating construction
materials, I ended up buying three models!
You can never have too many.
The Models: This F-15 is not exact scale,
but it is close enough that no one except the
most fanatical Scale modeler with a ruler 78 MODEL AVIATION
The layout of the Gray F-15’s (with all-flying stabilizer) upper
fuselage before adding the lower fuselage half. The wiring along
the center into the forward fuselage is installed, and the motors
have heat sinks added.
The White F-15, with the conventional control layout and routing
of wiring from the ailerons. Power and elevator routing are along
the center fuselage in all configurations.
This shows the location of servos for the conventional elevator
configuration. The area of foam that needs to be cut out is
crosshatched. A small microservo has adequate power for the job.
The servo for the all-flying stabilizer is located in this position on
the fuselage. The area of foam that needs to be cut out is
crosshatched. Verify that you are removing the right foam chunk.
Wing-attach parts are easier to plug into
the fuselage sockets when the corners are
rounded, as shown. Ben made the F-15
wings that didn’t use ailerons removable.
The F-15 with wings attached will fit into a
normal car’s trunk.
The author installed the E-flite speed
controls with their heat sinks oriented to
allow inlet airflow over the cooling fins. He
used epoxy on their edges to hold them in
position.
The small wire stubs sticking out on the aft
part of the canopy are a portion of a 1/16-
inch wire that goes across the bottom of
the canopy assembly. These are used as a
handle to remove the assembly.
will notice. The fuselage lines are of the
full-scale baseline F-15 equipped with the
Conformal Fuel Tank. If you want to learn
more about the full-scale aircraft, do an
Internet search. There is ample information
about the GWS-15, including videos of it in
flight.
My first GWS-15 was the gray
camouflage version. (I’ll call it the Gray F-
15.) The box’s labeling had a check mark in
the square next to “EDF-2028” and a check
mark in the gray square. There are many
squares on the box, to designate the type of
model that is inside. The Gray F-15 was
constructed from a normal cooler type of
polystyrene that GWS calls “EPS.”
After finishing the Gray F-15, I saw that
an all-white version (that I’ll call the White
F-15) was available. The labeling on its box
had a check mark in the “EDF-2028” square
with a check mark in the white square. The
White F-15 was also constructed from EPS.
I decided to build the white version as
well, to check the alternate control system
that was offered. I thought it would look
great with the Edwards Air Force Base early
flight-test color scheme that includes
DayGlo red wingtips and tail surfaces.
After building these two airplanes, I
learned about a third version of the kit. It
had a check mark in the “NPS” square on
the box and a check mark in the white
square. That means there is No Power
System included and that it is made from a
white foam called EPO, which is flexible
and tough. (I’ll call this version the EPO F-
15.) The EPO F-15 kit weighs roughly 3
ounces more than the EPS versions, which
isn’t too bad considering the foam’s
toughness.
The EPO F-15 kit came with fans,
shrouds, and full wiring, but no motors. It
was probably offered as a Slope Soaring
airplane or for someone who wanted to use
a different motor. I bought two GWS motors
and assembled the propulsion units. Soon
the EPO F-15 became a part of the home
hangar, and I investigated a third control
system.
If you are buying one of these three
models, inspect the kits or talk to someone
to make sure you are getting what you want.
There are also options for a pusher-propeller
version. Seeing the propeller on the ground
detracts from the pure jet vision I wanted,
but it isn’t too noticeable in the air where it
counts.
The three F-15s gave me the opportunity
to investigate three control-system
possibilities. The Gray F-15 was built with
the all-flying stabilizer for pitch and roll
control. The ailerons were not used. The
White F-15 used a control option employing
fixed stabilizers, with conventional
elevators for pitch control and conventional
ailerons for roll control.
The EPO F-15 had the Gray F-15’s allflying-
stabilizer control system along with
the White F-15’s ailerons. This is closer to
the control system the full-scale F-15 has. I
was looking forward to seeing the difference
in flight characteristics.
I don’t define this kit as an ARF because
you do have to build it. It is first-rate and
comes with two nice ducted-fan units,
complete with quality brushless motors.
Also included are all the needed servo-wire
extensions, power-wire extensions, and
everything else that is required according to
the instructions.
There are many extra parts on the
molded plastic “trees”; use only the ones
required for this build and save the others
for another time. You have to supply glue, radio-control equipment, two ESCs, three or
four servos (depending on the control
options chosen), and flight batteries.
Equipment Used: I have purchased all the
F-15s and RC equipment I have used in this
review from my “RC modeling” cash fund.
Being retired and finding that the cash fund
is not a bottomless pit, I have to choose
equipment based on quality and price. But
other equipment will perform equally well.
It’s a good time to be in the RC hobby.
I chose the Spektrum DX7 radio system
for guidance. I have never had problems
with my 72 MHz systems I have used in
more than 50 airplanes; however, I did
manage to crash several park flyers while
using them.
I would get hot or distracted at the flying
field and forget to change the transmitter’s
memory to the appropriate model name.
Dumb, of course, but it did happen. It is a
funny feeling to see the airplane rolling left
and you bend the stick to the right. The
problems certainly would have been
prevented if I had used a preflight checklist,
but I didn’t. I can give no valid excuse.
When the Spektrum designers
developed the radio systems, they
apparently had a photo of me in front of
them. I still have excellent range and
reliability, but now I have no frequencyinterference
problems and (what I really
needed) Spektrum’s great Model Match
feature. I no longer toss a model into the
air and wonder why the ailerons aren’t
working the way I think they should.
With the Spektrum, the receiver is bound
to the particular model program. Therefore,
when I plug everything in and wonder why
nothing will work, I know to make sure I
have the correct model assigned. This is
such a great feature that I have purchased a
second transmitter. Finally I won’t be such a
menace at the Boeing Phantom Flyers club
field.
The model controlled with the all-flying
stabilizer is designed to use GWS Park
servos that fit precisely into the fuselage’s
premolded slots. Plastic fittings that couple
the all-flying stabilizers to their driving
servos are molded to fit the Park servo
output spines. Using another servo would
require a lot of adaptation.
If you do use a different servo, be sure to
check compatibility before permanently
gluing anything. Almost any microservo
will work with the conventional control
layout. I used small JR servos since I had
some and they fit the cutouts perfectly.
Since the propulsion system’s current
drain is close to 20 amps per motor and the
ESCs may be mounted in such a way that
might limit the cooling air available, I
chose the E-flite 25-Amp Pro Switch-Mode
BEC Brushless ESC. It is a good
compromise in price and capability and has
a large heat sink to aid in cooling. I needed
two of them: one for each motor.
The propulsion system’s total current
drain at the maximum power setting was
probably going to be close to 40 amps, so a
suitable-capacity three-cell Li-Poly battery
was necessary. I chose the FlightPower EVO
25 2500 mAh Li-Poly battery, which has a
25C rating. It is excellent but fairly
expensive. I also bought the E-flite 2100
mAh Li-Poly battery, which has a 20C rating
and is much easier on the modeling fund.
Both batteries will be working within
their advertised ratings. Don’t try to use a
low-rated 2100 mAh 10C battery; you won’t
get the necessary power and will likely
destroy the battery.
Construction: The manual has a minimal
number of words, but the drawings are clear.
Pay attention to the areas where cutting foam
for servos is required. Read carefully, look at
the drawings, and then, with parts in hand,
do a dry run of positioning and checking for
interference, fits, etc. Then review
everything again.
Make sure you are confident before
proceeding to any step, because the
conventional control configuration and allflying-
stabilizer control configurations are
intermixed within the manual. Because of
the model’s construction, it becomes next to
impossible to go back and fix things once
you glue the fuselage top to the fuselage
bottom.
The wiring diagrams are well done, and
you should have no problem setting up that
part of the airplane.
The F-15 goes together nicely because
everything fits well. A modeler who is
experienced enough to fly the airplane should be able to work his or her way
through the manual. However, there are
several things that might make the build
easier.
All the radio and propulsion parts are
installed in the upper fuselage half, so you
can fully check things out one last time
before permanently gluing on the bottom
fuselage half. The ducted fans fit into slotted
areas, and the wiring for them and the servos
are routed along the fuselage centerline.
Cavities were molded to allow the wires
to fit, but because I changed connectors,
there isn’t quite enough room for
everything. You may have to remove a bit of
foam to make things fit, but no strength loss
is involved.
As you arrange the wiring for the servos
and propulsion gear in the fuselage, use
small pieces of tape to hold the wires in
place. When all the wiring is positioned in
the top, the bottom of the fuselage is glued
on and the rest of the assembly goes fairly
quickly.
Before I started this project, I didn’t care
for the GWS glue. Although it hardens
nicely, it has an extremely long working
time and I get in a hurry. I changed my mind
when I assembled the upper and lower
fuselage halves; the adhesive provided the
working time to do this properly.
I used the GWS glue on everything in the
Gray F-15 and White F-15 assemblies and
had no problems. They are molded from the
82 MODEL AVIATION
standard GWS EPS material, which
dissolves when almost any kind of glue or
solvent other than the GWS adhesive is
used.
When using the GWS glue, plan your
building schedule so that main glue
interfaces, such as the top and bottom
fuselage halves or main spar inserts, can
set up overnight. It will make things seem
to go quickly.
Take the time while the glue is
hardening to read the manual. The glue can
also be used like a contact adhesive where
applicable.
I constructed the EPO F-15 with
regular cyanoacrylate glue. This type of
foam doesn’t melt with cyanoacrylate use,
and I think the bond is better than with the
GWS glue. Foam-safe cyanoacrylate
doesn’t stick as well to the EPO foam. I
encountered no problems with the regular
cyanoacrylate and built the airplane in two
days. Test any substitute glue on a
noncritical, out-of-the-way area.
The wing flight loads are carried into
the fuselage through three tube spars and
one square spar. You can remove the wing
by pushing on a tab attached to the square
spar.
I glued the socket parts into the
fuselage and the plug parts into the wing,
with no major attempt to align them to
each other. I just pushed the part firmly
into its appropriate molded cavity.
When I finally pushed the wing spars
into the fuselage sockets, I was happily
surprised to find that everything slid into
place perfectly. However, when it’s 95°
and sweat is in your eyes at the flying
field, it might be difficult to hit the holes.
You can make wing attachment easier by
sanding a semirounded point on the ends
of the wing tubes and using a drill to
slightly chamfer the holes in the fuselage
sockets.
The canopy-latch mechanism was a
tight snap fit when I checked it before
installation. I had doubts that I could
remove the canopy without damaging the
canopy’s foam base using the supplied
parts.
I finally gave up on the supplied latch
parts and used 3/8-inch-diameter
neodymium magnets to attach the canopy
assembly. Just glue the magnets into the
foam at the front and rear of the canopy
with the appropriate glue or epoxy.
(Remember to check foam/glue
compatibility.)
Some sort of handle at the aft part of
the canopy is recommended to make
removal easier. I glued a piece of 1/16-inchdiameter
piano wire across the underside
of the aft part of the canopy assembly. I
allowed approximately 1/4 inch to stick out
on each side of the canopy base. I pull up
on each of the nearly invisible wire ends to
unlatch.
Don’t forget to add a pilot before
gluing the canopy on its base. It would be
nice if GWS included a pilot bust in the
kit.
I used the fixed-landing-gear option on
all my F-15s. I have seen videos of awful
hand launches of the model that
demonstrated its great recovery
characteristics. I thought it would be
difficult to hand launch because of the large
flat bottom and my small hands. The
landing gear will work fine on the beautiful
runway at the Boeing Phantom Flyers field.
The manual indicated that the CG
should be 160mm plus or minus 5mm aft of
the lower lip of the inlet. My F-15s’ CGs
came out within 1mm or 2mm of the
required 160mm mark when the ESCs were
installed roughly halfway in the inlet
ducting wall and with the battery installed.
The construction manual’s diagrams do
a nice job of illustrating the control-system
setups. To set up the EPO F-15’s
configuration, I installed the all-flying
stabilizer setup as used in the Gray F-15
and then put a servo splitter in the
Spektrum AR6100 receiver AUX port for
the aileron input. This may seem to make
the aileron servos move in the same
direction on the bench, but everything
works in the appropriate direction when the
servos are installed in the wing cutouts.
I don’t have information to answer
questions about any other type of radio
system. Make sure things work
correctly before fixing the servos
permanently in place. Set the initial
control-surface throws to those shown
for your setup in the manual.
The airplane looks good at this point,
but it would be great if GWS included a
bottle of touch-up paint in the gray kit. The
existing paint film is thin and easily
damaged during construction. Cover your
building area with soft materials to protect
the models.
I mixed some gray colors using artist’s
acrylic paint to touch up the construction
nicks and camouflage markings. Test any
paint for foam compatibility, and wash the
areas to be painted with alcohol or soapy
water.
For the White F-15’s Edwards Air Force
Base flight-testing paint scheme, I used
Faskolor acrylic Fasfluorescent Red that I
bought at Mark Twain Hobbies in Saint
Charles, Missouri. Having a hobby shop of
this quality a few miles from my home is
great. The prices are competitive, and the
staff is knowledgeable and friendly. Mailorder
hobby sources are fine, but we need
to keep our local hobby shops in business.
I have one major complaint. The plastic
parts used to mount the all-flying stabilizer
and vertical tails were black—big, black,
plastic, clunky parts. Why not mold them in
a nice gray or white, to match the airplane?
The construction manual presents a
range of flying weights between 28.3 and
35.3 ounces. It suggests using a 1.3- to 1.8-
amp-hour Li-Poly battery of greater than
15C capability for power. I think a battery
with that low of a capacity will have a hard
time delivering the required power to the
ducted fans.
The final weights of my models with
no batteries were: Gray F-15, 32 ounces;
White F-15, 31 ounces; EPO F-15, 36
ounces. Its weight was because of the extra
weight of the foam type used.
Propulsion Tests: With a freshly charged
battery that was capable of delivering full
power to the system, the initial power
input was roughly 500 watts (measured
with an AstroFlight Whattmeter). That is
49 amps at 10.3 volts (voltage under full
load).
This voltage drop from the battery’s
fully charged resting voltage of more than
12 volts is typical of a Li-Poly battery
delivering high power relative to its
capacity. And the power available
throughout the motor run will be much less
than these initial measurements as the
battery discharges to the preset ESC cutoff
voltage.
Those 500 watts convert to an initial
measured static thrust of roughly 32
ounces. In-flight thrust will be less and
will drop from 30 to 20 ounces or so.
This thrust-to-weight ratio isn’t too
bad, and you do have maximum power at
takeoff. You might be unable to hover and
torque roll, but this is a ducted-fan scale
model of an F-15 for a reasonable price.
Flight Notes: Even with my rusty reflexes
and the cold weather, I found the GWS F-
15 to be delightful, fast, and smooth-flying
in all configurations. The only problem I
had was pulling back on the throttle once
the F-15 was in the air. Although it flew
nicely at lower speeds, it was way too
much fun to perform the entire flight with
full power.
My flight tests indicated that the
control-surface throws recommended in
the construction manual were well suited
to the model at the recommended CG.
Since the airplane didn’t seem twitchy,
you can fly it with a four-channel
transmitter that doesn’t have exponential
capability. However, if you have that
feature you can add exponential to suit
your preferences as you gain experience
with the airplane.
Takeoffs with the Gray F-15 and the
EPO F-15 were smooth and easy to
control. Setting the controls neutral so the
all-flying stabilizer faired with the fixed
part of the stabilizer mounted on the
fuselage was a good starting point. The
change in neutral control required for
actual level flight was a bit of up-elevator
trim.
Roll trim setting was almost on too.
There was no problem in trimming the
models.
During the White F-15’s first takeoff
with the conventional elevator for pitch
control, I had the transmitter settings to the
low control rates. I found that I didn’t have
enough back stick to rotate the model. I had set the high-rate throw to the throw
shown in the manual, and the low-rate throw
was set to approximately half that—my
mistake.
So I cut off the power on the model and
let it run off into the grass at the end of the
runway. In the process, the first 1/2 inch or
so of the nose cone broke off.
Low control-rate throws should start at
the manual’s recommended settings. Then
you can set the high throws higher than that.
When comparing the all-flying stabilizer
(Gray F-15) to the all-flying-stabilizer-plusaileron
configurations (EPO F-15), I found
that the all-flying stabilizer’s roll-control
authority is good enough that the ailerons
aren’t needed. The all-flying stabilizer also
seems more effective in pitch control than
the conventional elevator. I am looking
forward to more experimentation with all
these control systems.
The Gray F-15’s first landing was good,
but it did run out onto the short grass at the
end of the runway. This resulted in roughly
the first 1/2 inch of the nose cone’s breaking
off, as happened with the White F-15.
I didn’t think the landing was too fast,
but I was noticing a trend with the nosecone
tips. I didn’t know grass was that hard,
but it was freezing.
The EPO F-15’s landing was nice and
smooth but a bit long, and after a long
runout it was into the grass. At least the nose
cone stayed intact. So it wasn’t the grass
breaking the nose off; it was because of the
weak foam.
This should lead to a modification of the
standard kit. Replace the nose cones made from
the Styrofoam-type material with the EPO.
The other result of the trip to the flying
field was a fuselage broken in half midway
under the canopy. This happened when my
helper picked up the White F-15—but I
need to clarify that.
Most helpers and modelers have learned
to pick up a model with one hand under the
wing or fuselage near the CG and the other
hand on the nose to steady the airplane. We
might lift with considerable force on the
nose because it is often the strongest part of
the model. When you do that with this F-15,
it puts pressure on the nose in the weakest
part until it breaks at a point approximately
halfway back from the front of the canopy.
I will use carbon-fiber mat or something
similar with epoxy to strengthen the inside
of the fuselage on each side along this area.
I recommend that you do so too.
I really do like this model, how it looks,
and how it flies. I recommend it to any
experienced flier. MA
Ben Lanterman
[email protected]
Manufacturer/Distributor:
Grand Wing System U.S.A. Inc.
138 S. Brent Cir.
City of Industry CA 91789
(909) 594-4979
www.gwsus.com
Sources:
E-flite
(800) 338-4639
www.e-fliterc.com
FlightPower
(800) 637-7660
www.bestrc.com/flightpower/
Spektrum
(800) 338-4639
www.spektrumrc.com
Online Forum and Video:
www.rcgroups.com/forums/showthread.php
?t=682816
Other Review Articles:
Aviation Modeler International: May 2008
Quiet Flyer: December 2007