Park View: Great Planes XPD-8 ARF
Jim Hiller
GREAT PLANES has created a park flyer–size 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 impressive for a model spanning only 28 inches and weighing less than 13 ounces.
My XPD-8 arrived in what appeared to be a large box for such a small airplane—until I opened the package and saw the one-piece model. It required only simple assembly. The aircraft is molded foam with a rigid one-piece wing and prehinged elevons.
The finish is black 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 looks quite sophisticated 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 high-frequency ESC and ElectriFly 910 mAh, 11.1-volt Li-Poly battery. The required servos are two Futaba micro S3110 7.7-gram units, plus a micro receiver.
Assembly is straightforward
Before I began, I gathered all the required radio equipment because I wasn't building the XPD-8 so much as equipping it.
The first item of business is the ducted-fan-unit assembly, which is simple. Bolt the motor in place, locate the correct impeller adapter in the package, secure it 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 necessary 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, there is no tedious soldering—just assembly.
The completed ducted fan glues into 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.
Next, make a 3/8-inch-diameter 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 clear 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 recesses 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 balanced exactly as specified.
Position the canopy hatch, which is secured with magnets that are already installed. That's convenient—no bolts or fiddling to attach 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. The instructions were missing the elevon neutral position, so I set neutral for a slight up-elevon trim.
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 good advice, 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 toward 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 well! It does fine for a ducted fan with a brushed motor, and once it gets moving it scoots. Great Planes' Web site claims this model will exceed 50 mph in level flight, and I believe that after flying it.
The initial push after hand launching the XPD-8 will appear slow to those 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, then 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 by turbulence, so it tracks well on windy days.
Aerobatics with this aircraft are similar to those with most flying-wing designs. Rolls are fast, and they are not sensitive near center; I saw 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 management is required.
I found a useful characteristic: if it is too slow over the top of a loop, it will roll right-side up and fly out easily at the top of the loop with no altitude loss. This matters to me because I tend to fly low and tight—when you stall off the top of a loop, you lose 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 perform 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 is fun to fly. 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.
Jim Hiller [email protected]
Specifications
- 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
Test-Model Details
- 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
Manufacturer/Distributor:
- ElectriFly/Great Planes
- Champaign, IL 61826
- (217) 398-8970
- www.electrifly.com/ductedfans/gpma1865.html
Other Review Sources:
- Fly RC, February 2007
Pluses and Minuses
Pluses:
- Quick assembly time (less than two hours)
- Visible color scheme with decals
- Good electric-ducted-fan performance
Minuses:
- Elevon neutral position not provided in the directions
Transcribed from original scans by AI. Minor OCR errors may remain.
