Manual 12682467
F LY R C M A G A Z I N E
ELECTRIC WARBIRD TRAINER
FLIGHT REPORT
by Roger M. Post Sr.
SPECS
PLANE: Stearman PT-17
MANUFACTURER: Maxford USA
DISTRIBUTOR: Maxford USA
Manufacturing
TYPE: Sport-scale biplane
FOR: Intermediate to advanced pilot
The 1/8 scale pilots fit perfectly in the cockpit, but I had to trim one instrument down and add ¼-inch
balsa stock to the other to get them to fit into the cockpits.
WINGSPAN: 50 in.
WING AREA: 720 sq. in.
A sport-scale icon
with a 50-inch span.
MAXFORD USA
Stearman
PT-17
Y
ears ago, I had a ¼-scale PT-17 kit
that sat in my garage’s rafters for
what I’m guessing was a couple of
decades—something about aging the wood
before you build it. Eventually, I either
gave, or sold, it to someone, but the thought
of having a model of Lloyd Stearman’s classic design has never left me.
Back in January 2011, I saw an advertisement for Maxford USA’s 50-inch, electric-
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powered PT-17 that has John Mohr’s fullsize -17’s Army Air Corps pre-war color
scheme and thought that it would be the
perfect answer to my Stearman desires. It
was small enough that it would fit into my
car in one piece, and with an electric motor,
I could fly at just about any open field.
A little investigation into the combination
packages Maxford offers for this 1/8 scale
(rounded off from 1/7.72) model showed that I
could get just the PT-17, or the -17 and the recommended power package, which includes
the Uranus 35425 brushless outrunner motor,
60-amp ESC and a 3S 2100mAh battery. They
also offer a Detail Upgrade Package that
includes two, 1/8 scale pilot figures and two
instrument panels. Sticking closely to
Maxford’s recommendations, I opted to get
their power system and detail package, rather
than hunt around for equivalent options.
The box for just the model was very
securely packed with everything arriving
damage-free. It contained the factory-built,
laser-cut balsa- and light plywood-constructed fuselage, wings, empennage and
N-struts that were pre-covered with Mylar,
nylon string for flying wires, a pre-painted
7-cylinder dummy radial engine, scalelooking windshields, a pre-covered hatch
that attaches with rare-earth magnets, precut servo mounts, a full set of CA hinges
with matching pre-cut hinge slots, a complete pushrod set with all the required control horns and linkages, a pre-bent aluminum main landing gear with plastic fairings, wheels (with treaded tires) and their
required mounting hardware, a scale-look-
ing steerable tailwheel-wire strut assembly
and tailwheel with mounting hardware,
plywood cabane struts and their hardware,
carbon-fiber wing rods, a battery mounting
platform and Velcro to attach the battery,
all the screws, nuts and bolts to complete
the assembly process and decals. Possibly it
was an oversight, but I didn’t receive the
detailed assembly manual with color photos, so I printed it from Maxford’s website.
A close inspection showed that the constructed parts were made well and that the covering
application was quite good. After removing a
couple wrinkles, it was time to build.
TIPS FOR SUCCESS
The first thing to do is to read through the
entire manual and determine
that all the correct parts and
hardware are included. Mine
was an earlier version and
had some incorrect screws
for the dummy radial engine
mounting and not enough
correct-length bolts for the
aileron control horns (two of
the six were too short). So a
quick look in the workshop’s
screw/bolt supply fixed this.
Assembly starts with rudder and elevator pushrods
being placed and the tailwheel wire and its strut
being trial-fitted into the
bottom of the aft fuselage.
The horizontal stabilizer
must first be placed in its
cutout so you can see where
Included in the kit is a dummy
engine that replicates the original 7-cylinder Continental that
initially powered the -17s.
WEIGHT: 4 lb.
WING LOADING: 12.8 oz./sq. ft.
WING CUBE LOADING: 5.72
LENGTH: 37 in.
RADIO: 4 to 5 channels required, with
four mini servos; flown with a Spektrum
DX7 transmitter, a Spektrum AR500 DSM2
receiver and 4 Hitec HS-65HB servos
POWER SYSTEM: Maxford USA Uranus
35425 outrunner brushless motor,
Maxford USA 60-amp brushless ESC,
Thunder Power 3S 11.1V 2250mAh 30C
Pro Power LiPo battery, Maxford 11 x 7
electric propeller
FULL THROTTLE POWER: 35 amps,
388.5 watts, 6.07 watts/oz, 97.13 watts/lb
TOP RPM: 8,000
DURATION: 7 minutes
MINIMAL FLYING AREA: sports field
PRICE: $195.99
COMPONENTS NEEDED TO
COMPLETE: 4-5 channel transmitter and
receiver, 4 mini servos, one 6-inch Y-harness
(for a 4-channel radio), two 10-inch servo
extensions, (if using two channels for the
ailerons, add two 6-inch servo extensions), a
Uranus 35425 outrunner brushless motor,
60-amp brushless ESC, 3S 11.1V 2100mAh
LiPo battery and compatible charger, 11 x 7
electric propeller; there is a Detail Upgrade
Package that can be added, which includes
two pilot figures and two instrument panels.
SUMMARY
The construction was quite good and the
Mylar covering needed only a little touchup with the iron to take out some wrinkles. I recommend picking up the Detail
Upgrade Package because it really
enhances the PT-17’s overall “scale”
appearance. It flies very well, and could
easily be handled by an intermediate-skill
pilot; but most importantly, don’t be afraid
to add whatever weight is necessary to
make it balance at the recommended CG
mark: 3 3/8 inches from the leading edge.
JULY 2011 81
MAXFORD USA STEARMAN PT-17
There is plenty of room in the radio compartment for
your RC gear. To help with balancing the airplane,
push the battery as far forward as it will go.
AIRBORNE
the extended tailwheel wire goes through
the pre-drilled hole in the stabilizer. The
stabilizer is then glued into position before
the tailwheel wire and strut are mounted.
Make sure the tailwheel’s strut portion is
vertically straight—in-line with the model’s
yaw axis. The remaining empennage
assembly steps are self-explanatory.
For the aileron’s servo set-up, I used the
flaperon mode, so I added two 6-inch servo
extensions to my receiver. I prefer this to a
Y-connector because it gives you individual
control over each servo. The bottom wing
halves slide onto their carbon-fiber wing
rod and alignment pins. They fit tightly into
place and there aren’t any bolts to secure
them. When the top wing and the N-struts
are attached to the overall structure, the
bottom wings are then secured in place via
their attachment to the N-struts.
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With a 44-degree temperature and the sun shining brightly, I at last had the perfect day for a
test flight. After double and triple checking that everything was securely tightened, I turned
on the radio and plugged in the battery, confirmed that all control surfaces moved in the
correct direction and blipped the throttle. The motor response was good and there was
enough thrust to fly the model.
When taxiing on bumpy grass, the -17’s narrow gear stance had it waddling a little bit, and
it’s best to hold full-up elevator to keep the tailwheel planted for positive steering. On a
paved surface, the biplane taxis very smoothly.
A gradual throttle application to about 2/3 had the PT rolling about 12 feet to become airborne. The obligatory right rudder kept it tracking straight, and once it lifted off, it immediately climbed with a 45- to 50-degree AoA. To make the climb-out shallower, I fed in a little
down elevator. Once the plane reached a safe altitude, I added seven beeps of down trim
and brought the power back to ½. With this accomplished, the model was now flying
straight and level, hands-off.
After a few circuits, rolls and loops were performed, using some dives to gain airspeed,
rather than adding too much extra throttle to pull the model through the maneuver. A small
amount of forward stick keeps inverted flight from losing altitude; spins, however, turned
into spirals, as the model needs more rudder throw than what is recommended. Stalls were
gentle and showed no sign of falling off on a wing.
Knife-edge flight requires a good head of steam at the entry to maintain it, as there is a lot
of drag with those two wings and their supportive struts. One thing I did before I flew this
was to watch some videos of John Mohr flying his stock Stearman. He does what appears
to be a low-level forward slip down the length of the runway with the smoke on. Well, I
don’t have the smoke, but I did try this cross-control maneuver. It worked out great, but it
sure was funny to see the airplane’s nose pointing in a different direction than which the PT
was traveling.
After 6.5 minutes of flying, the battery ran out of juice, so I glided the -17 in for a soft
touchdown. It has a nice flat glide and I was able to make the runway without a problem. I
did cut the downwind leg at the numbers to ensure the plane could make the runway.
Once I got the high AoA under control, the -17 proved to be a smooth flyer and quite stable.
I’m looking forward to a summer of barnstorming fun with this one.
MAXFORD USA STEARMAN PT-17
As ARFs are notorious for weak landinggear areas, I beefed up the PT’s with some
triangular stock placed inside the fuselage. I
also changed the mounting bolts and nuts
to 4/40s, using blind-nuts in the plywood
mounting plate.
Quick connectors are used on the aileron
control horns and the rudder and elevator
servo arms. I had to drill out their holes to
get the connectors’ pins to fit in. When
installing the radio, I had to slightly carve
out the servo openings so they would accept
the Hitec HS-65s. From here, I hooked up the
radio and checked to see that everything was
going in the correct direction.
When I added the instrument panels to
the cockpits in the hatch, I discovered that
they were both the same size, however, the
openings varied because of the fuselage’s contour. So, for the front one, I
had to trim it slightly to get it to fit and,
for the aft one, I had to add some ¼square balsa stock to get it touch the
hatch’s sides and top. The pilots mount
on straddled Popsicle sticks that need to
be cut to a four-inch length, not 3 5/8 as
the manual states. The latter length is too
short. Once the windshields were added,
the hatch assembly was complete
The motor and ESC are now plugged
in, tested for correct motor-rotation
direction and then mounted on and in
the fuselage.
When attaching the cabane struts,
remember to also include the four
swivels required for the flying wire rigging. They go on the top-outside of each
strut. The top wing is then assembled and
attached to the cabanes, and then the Nstruts are added with the required swivels:
four per strut, with one each on the topinside and two on the forward-bottom. The
N-struts have a certain way the go on, so
correctly match up the holes before you
start placing the bolts, swivels and nuts.
Four other swivels are mounted to the fuselage with wood screws; two are located in
front of the lower wing’s leading edge and
two are located in front of the landing gear’s
upper fairings.
Once the flying wire rigging is completed,
the dummy radial is trial fitted and
attached. The propeller was then balanced
and attached, and when the decals were
placed, the assembly process was complete.
After I set up the given control throws, it
was time to balance the model and here is
where it got interesting.
When completed, the model weighs 3
pounds 9.5 ounces. The 2.2 pounds listed in
the specs is just for the ARF without any
electronics. To get the -17 to balance at the 3
3/8-inch mark, I had to add 6.5 ounces to the
nose. The main problem was: where?! I
wound up placing 3.5 ounces in the dummy
radial’s hollow crankcase area, one ounce on
the firewall and picked up a Harry Higley 2ounce, brass prop nut to replace the stock
nut. That did the trick and I now had a bal-
When you install the tailwheel strut fairing,
ensure that it is vertically straight (parallel) to
the fuselage’s yaw axis.
anced model. Now, if you are concerned
about all that additional weight, don’t be.
There is plenty of wing area and power to
fly this model at the total 64-ounce weight,
and that was proven on the first flight.
CONCLUSION
So after a few days of work and a little
changing of some hardware, I finally had
the Stearman that I have always desired. It
looks great, flies well and sure gets some
attention from my flying buddies. If you’re
a Stearman fan, this Maxford model will fill
the void of one missing from your hangar.
And, there is just something about two
wings, open cockpits and a round motor
that is very satisfying! =
Visit find.flyrc.com/071102 to watch the video!
Links
Harry Higley, www.harryhigley.com
Hitec USA, www.hitecrcd.com, (858) 748-6948
Maxford USA, www.maxfordusa.com,
(866) 706-8288
Thunder Power, www.thunderpowerrc.com,
(702) 228-8883
Spektrum, distributed by Horizon Hobby,
www.spektrumrc.com, (800) 338-4639
For more information, please see our source guide
on page 121.
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