Park View: Great Planes XPD-8 ARF - 2008/03

80 MODEL AVIATION
JIM HILLER
Park View: Great Planes XPD-8 ARF
The large ducted-fan inlet stands out in the front view but is necessary to
attain performance with this aircraft.
A ducted-fan model to use for
zipping around small fields
The military stealth paint scheme is in
contrast with the light-gray bottom. The
canopy is attached with magnets.
GREAT PLANES has created a park flyersize,
electric-ducted-fan model that can fly
well in moderate wind conditions.
According to the Web site, the XPD-8 ARF
has a top speed approaching 55 mph; that’s
good for a model spanning only 28 inches
and weighing less than 13 ounces.
My XPD-8 came in what appeared to be
a large box for such a small airplane. I
thought that until I opened the package and
saw the one-piece model. It required only
some simple assembly. The aircraft is
molded foam with a rigid one-piece wing
and prehinged elevons.
The finish is black paint on top with a
gray bottom—good contrasting colors. The
foam canopy hatch is light blue and detailed
with canopy frame lines in black. In
addition, the XPD-8 has well-placed letter
decals and red stripes. It is quite
sophisticated in appearance for a simple
foam model.
The HyperFlow electric-ducted-fan unit
is included, with a quality 370 BB brushed
motor. I stayed the Great Planes/ElectriFly
route with the suggested C-25 mini highfrequency
ESC and ElectriFly 910 mAh,
11.1-volt Li-Poly battery. The required
servos are two Futaba micro S3110, 7.7-
gram units in addition to a microreceiver.
Assembly is straightforward. Before I
began I took the time to gather all the
required radio equipment because I wasn’t
building the XPD-8; I was really only
equipping it.
The first item of business is the ductedfan-
unit assembly, which is simple. Bolt the
motor in place, locate the correct propeller
(impeller) adapter in the package, secure it
in place on the motor shaft, and then bolt on
the fan.
Final assembly requires gluing on the
spinner and the aft speed fairing. Trimming
the aft speed fairing is required to clear the
motor wires. The motor comes prewired with
simple in-line connectors that mate with the
C-25 speed-control connectors. If you stick
with the Great Planes/ElectriFly product line,
you will find that there is no tedious soldering
to do—just assembly.
The completed ducted fan glues in place to
the fuselage duct channel in the molded
recess. The recommended glues are either
epoxy or foam-safe cyanoacrylate. I opted for
hot-melt glue because there is no smell and it
is simple to use.
Now the tough part. Make a 3/8-inchdiameter
hole through the fuselage top half for
the motor wires. Once that is complete, cut
two additional holes per the instructions for
the servo wires.
Great Planes provides a great write-up in
the instructions about how to mark and cut
these holes in the foam. Take time to read
the directions.
With the holes complete, glue on the
fuselage upper half. While the glue is out,
also mount the two fins. I was impressed by
the supplied fins; they are not just simple
foam, but are actually molded with a thin
plastic skin. These fins are rigid and rugged
for such a small model.
The molded recess for the servos fit
perfectly, so I used a bit of hot glue to
secure the servos—one for each elevon. The
kit includes all pushrods, control horns, and
pushrod connectors. The pushrods are the
indoor style, with a piece of heat-shrink
tubing splicing two piano wires together to
set the pushrod length. This is a simple and
popular method for making pushrods on
smaller, lightweight models.
The receiver, battery, and speed control
mount on top of the fuselage using the
supplied hook-and-loop material. The
instructions discuss positioning the battery
fore or aft under the canopy to obtain proper
balance; my model came out exactly as
specified.
Position the canopy hatch, which is
secured with magnets that are already
installed. That’s cool; there are no bolts or
fiddling with attaching the canopy. The
recommended 910 mAh, 11.1-volt Li-Poly
is almost the largest battery that will fit
under the canopy.
Final setup of the XPD-8 only requires
setting the control travels as recommended:
half travel of the elevons for elevator and
half travel for aileron. My instructions were
missing the elevator neutral position of the
03sig3.QXD 1/25/08 10:12 AM Page 80March 2008 81
The XPD-8 comes nicely packaged with the fan unit and motor supplied. This model is
truly almost ready to fly, less equipment installation.
Photos by the author
Servo installation is quick and easy with pockets molded in; simply
glue the servos in place. Notice the finger wells to assist in hand
launching.
The supplied HyperFlow ducted-fan unit is
well designed and comes complete with a
performance 370 BB brushed motor.
The HyperFlow ducted-fan unit is glued into the fuselage duct
before gluing on the upper fuselage half. Notice the duct’s crosssection
shape.
The XPD-8 is a fast flier with good aerobatic capabilities that are common with flyingwing-
type models. Flight speeds are likely between 50 and 60 mph.
elevons, so I set neutral for slight up-elevon.
Flying: All systems were ready, batteries
were charged, and it was time for some fun.
Equipped with the 910 mAh 3S pack, my
XPD-8 weighed only 12.1 ounces with the
stock motor. Great Planes recommends that
an assistant launch the XPD-8 while the
pilot flies it. That’s a good idea, as I soon
learned.
I had concerns about the elevon neutral
position on my test flight, and I got it
wrong. With not enough up-trim, the XPD-8
settled right to the ground, hooked a
wingtip, and broke off a fin.
With a bit of hot glue, some hurt pride,
and more up-elevon trim, I tried again. The
next hand launch was successful, and the
recommended throws worked well. The
neutral trim point worked out to be
approximately 3/16 inch up.
How does the XPD-8 fly? Actually quite
03sig3.QXD 1/25/08 9:44 AM Page 8182 MODEL AVIATION
Type: RC sport
Pilot skill level: Intended for advanced
sport
Wingspan: 28 inches
Wing area: 209 square inches
Length: 15 inches
Weight: 12-13 ounces
Wing loading: 8.3-8.9 ounces/square
foot
Motor: 370 BB brushed
Radio: Three channels with elevon
mixing, two servos
Construction: Molded foam
Covering/finish: Paint, stick-on decals
Price: $99.99 street
Specifications
Motor: Supplied 370 BB brushed with
ElectriFly C-25 ESC
Propeller: Supplied HyperFlow ducted
fan
Battery: ElectriFly 910 mAh, 11.1-volt
3C Li-Poly
Radio system: JR 10S transmitter, two
Hitec HS-55 servos, FMA Direct
microreceiver
Ready-to-fly weight: 12.1 ounces
Flight duration: Five minutes
Test-Model Details
+
• Quick assembly time (less than two
hours)
• Visible color scheme with decals
• Good electric-ducted-fan performance -•
No elevon neutral position provided
in directions
Pluses and Minuses
well! It does fine for a ducted fan with a
brushed motor, and once it gets moving it
does scoot. Great Planes’ Web site claims
that this model will exceed 50 mph in level
flight, and I can believe that after flying it.
The initial push after hand launching the
XPD-8 will appear slow to those who are
accustomed to propeller aircraft, but it is as
good as any ducted-fan electric model with
a brushed motor that I have flown. I use a
few additional clicks of up-elevator trim for
the hand launch, and then I retrim for flight
once the XPD-8 gains airspeed.
I was surprised by the speed this model
builds up to; it likes to go fast! I have
looped it from level flight. It is fast enough
and heavy enough to comfortably handle
winds up to 15 mph; in fact, you may prefer
the wind to aid in the hand launch. The
XPD-8 is not blown around with turbulence,
so it tracks well on windy days.
Aerobatics with this aircraft are similar
to those with most flying-wing designs.
Rolls are fast, but what impresses me is that
they are not sensitive near center; I have felt
no need to program in exponential. Loops
are as good as the airspeed you have at
entry. The XPD-8 does not have a light
wing loading for this size model, so good
airspeed usage is required.
I did find that the XPD-8 has a
characteristic that works well. If it is too
slow over the top of a loop, it will roll rightside
up and fly out easily at the top of the
loop with no altitude loss. This is important
to me; I tend to fly low and tight, and when
you stall off the top of a loop, you use up
much more altitude than you start with.
The XPD-8 glides in nicely for landing,
but do not stall it; keep it gliding in at a
comfortable speed, with power off. Touch
down with the wings level, and it will slide
along the ground to a stop. This model will
drop a wing if you stall it, so touch down
with a smooth flare and do not try to slow it
too much during the approach.
This ElectriFly model is a cute little
ducted-fan design that one can have some
fun flying. It is a true ARF; one evening of
assembly time is more than ample. The fan
unit works well, and the aircraft flies as
advertised.
I fly the XPD-8 in a park area of only 320
x 175 feet, which is adequate for an
experienced pilot. It is tight, but the model has
the speed and wing loading to shine at larger
fields, even when the wind is kicking up. MA
Jim Hiller
[email protected]
Manufacturer/Distributor:
ElectriFly/Great Planes
Champaign IL 61826
(217) 398-8970
www.electrifly.com/ductedfans/gpma1865.h
tml
Other Review Sources:
Fly RC, February 2007
WW1 AERO 1900 to 1919 SKYWAYS 1920 to 1940
03sig3.QXD 1/25/08 9:47 AM Page 82