JC's
Planes and Projects
Ryan
Aircraft electric P-47 Thunderbolt with Mega brushless motor
Specifications:
Wingspan: 31
inches
Length: 27.25 inches
Weight: 20-oz
RTF
Transmitter:
Futaba T6XA
Receiver: Hitec
555
Servos: 3 x
Hitec HS-55 for full four-channel control.
Power: Mega
16/15/5 brushless motor with Jeti 18-3P controller. Batteries are 8-cell packs
of Sanyo KR600AE or HEcell 1100 mah NiMH.
Prop: APC 7x5 E
Finish: Glassed
and painted with Model-Master Acrylics and Krylon. Scheme is Col. Francis
"Gabby" Gabreski's P-47D.
Features: The
stock 1-meter antenna was cropped in favor of an internal Azzar 6" long
antenna.
Everyone
has his or her favorite WWII warbird. For me it is the Republic P-47
Thunderbolt. There is something about the fat fuselage, stubby elliptical
wings, and blunt nose that are very appealing to me. When I read about Jim
Ryan's little electric P-47 in Model Aviation, I knew that I would be buying
one someday. Being a true modeler, I ordered the kit despite having three other
projects in the works!
The kit is
available online from Jim Ryan's website. He takes PayPal and ships quickly.
Upon receiving the kit I was impressed with the full-size rolled plans and all
laser-cut wood. The quality of the wood was excellent. Also included in the kit
is the plastic canopy for the "bubble" or "razorback"
model, as well as some excellent frisket stencils to help you paint the canopy
frame. The kit contains no assembly instructions, so I used the instructions
given for scratch-building the Jug in Model Aviation.
The kit builds
very quickly and the laser-cut pieces fit very well. The wings were done before
I knew it. The fuselage was a new experience using a crutch to hold the formers
in position as you stringer and sheet the assembly. The pre-cut 1/16"
skins for the fuse were a great help and required minimal trimming. If you have
never sheeted a warbird fuselage, well…you'll get used to it! Use a little water/alcohol to help with the
bending. I would slide the fuse crutch back and forth a bit during assembly
just to make sure that it was not glued to any formers. I wanted that sucker to
come out of there when I was done sheeting! It did and the result was a very
strong, light, stressed-skin fuselage.
The only
construction areas that were vague to me were the control system installation.
The routing of the aileron flex-cable is shown on the plans, but you were
pretty much on your own from there. The single servo and flex cable ended up
working very well with no binding to speak of. This is the smallest R/C
airplane that I have built and most of the control hardware that I found at the
local hobby shop was too big and over-built. I took Jim's advice and fashioned
all control horns out of thin plywood and mortised them into the control
surfaces. The pushrods for the rudder and elevator are music wire with Z-bends
at the servo end and clevises soldered on to the control surface end. I had the
radio on, servos centered, and surfaces clamped in neutral while I soldered.
For the ailerons, I fashioned Z-bends out of music wire with about a one-inch
"tail" and soldered them to a parallel length of the control cable.
Above is the
aileron servo in the center section of the wing. Two mounting rails were glued
to the bottom of the wing to mount the servo. The fat belly easily accommodates
the servo. I used a screw lock on the control horn, fed the cable through, and
tightened a 6-32 nylock screw to hold it in place.
I glassed the
structure using the same technique that I used on my big Jug. I did use a
thinner mixture of Z-poxy for the second coat, however. Remember that this
thing is supposed to be light! After wet sanding and filling with glazing
compound, the structure was primed with white Krylon primer. I used a plastic
model kit of the P-47 as my documentation for the Gabreski Jug scheme. While challenging,
this scheme is really wild and I especially like the invasion stripes on the
tops of the wings. This will present a great visual reference when flying this
diminutive airplane.
The underside of
the airplane is "natural metal" and I messed-up by using the wrong
paint. I don't know if I ordered the wrong stuff, or if Tower sent me the wrong
stuff. It is a "metalizer" for use with plastic models. Some of it has rubbed off the belly already.
Oh well, live and learn. This was also my first use of an airbrush. I did a lot
of experimenting until I got the hang of the thing. I first used a silver paint
pen to mark the major panel lines on the wings and fuselage. I then used Pacer
canopy glue to apply rivets in key areas on the cowling, fuse and tail fillets,
and wing access panels. I applied a dab of silver to the top of all the rivets
so they could be revealed later during weathering.
I then proceeded
with the light gull gray base coat on the top of the airplane and then
freehanded the camo patterns in gunship gray. The Acrylics look nice, but
required quite a bit of thinning to flow well through the brush. I have not
tried enamels, so I can't compare the two.
The stripes were
masked using low tack tape. The white acrylic had poor coverage, so I
"cheated" and started using flat white Krylon straight from the can
for better opacity. All insignias and markings were cut from frisket stencils
and painted on. This was not as difficult as I thought although it was time
consuming. The end result is much better than a decal. The red nose and tail
were sprayed from a can of Krylon and over-coated with Testors dull-coat
lacquer. For weathering, I scratched the paint on panel lines and rivet areas
to expose the silver pen markings below. The effect is acceptable, but most of
the panel lines were lost under the dark camo and I could not find them to
reveal them. Next time I will just pick some key panel lines and access panels
for this process.
Based on Jim
Ryan’s advice, I installed an Azzar 6-inch antenna in the bottom of the rear
fuse. This a great product that rids you
of that 3-foot antenna dangling from your scale airplane while still offering
enough range to fly your little model out of sight. I opted to use small pin and socket
connectors to make the RX removable since the antenna is glued into the fuse
permanently.
I have flown a
5-turn Mega Brushless motor in my Zagi most of last summer. The performance was
excellent, so I decided to go brushless on this model as well. After all the
work, I wanted optimum performance and duration from this model. I purchased a
6-turn Mega 16/15/6 with a prop adapter, prop, and TMM 18+3P controller from
Northeast Sailplane Products. The pricing and promptness of shipment from this
vendor was very good. I wish that was the
end of the story, but I don’t want to give you a diatribe when you came here to
read about the airplane. For more info
on the power system issues see bottom of this page. To make a long story short, I ended up with a
5-turn Mega motor and a Jeti 18-3P ESC and they work flawlessly as
expected.
With the
airplane fully assembled, and an 8-cell KR600AE battery installed, the AUW was
20-ounces. This is two more ounces than target, but the power of the brushless
motor should more than make up for it. A
test run-up gave excellent thrust and full-throttle duration of about five
minutes. The batteries were comfortably warm afterwards. I also purchased an 8-cell pack of the new
HEcell 1100mah NiMH cells at the
I located the CG
per the plans and balanced the model using the two different battery
packs. I used Velcro to mount them to
the battery tray. I used a colored
marker to indicate the location of the battery packs. Jim really did his homework! He put the battery tray in exactly the right
place! The controls throws were set to
3/16” as recommended with ¼” set for high-rates.
The little Ryan
Jug was a very fun project combining the best of R/C and fine scale
modeling. I highly recommend this kit
and power system!
Flying
the little Jug
Post flight
inspection revealed that one of the lower firewall mounts had broken and the
battery was moving around in the fuse due to insufficient Velcro to hold
it. I should have packed it up right
there but I went up again and this time used the HEcells. Mike tossed it up again, and again I had to
correct it before it hit the ground.
This time was a little more exciting as it came a foot from dragging a
wing-tip! I got it up and cruising around
when I started hearing a vibration at various throttle settings. I landed and noticed that I had lost the
second lower firewall mount. Time to go
home for repairs. At home I installed
the lower firewall mounts and added Velcro to the batteries and tray. Ready to go again.
The second
outing had my knees knocking since nobody was at the field to help with the
launch! The good thing was that there
was a nice steady wind in my face of 7-10 mph.
I took Jim Ryan’s advice and trimmed some up elevator. I spooled up the motor, took a couple of
quick steps, and pushed it into the breeze.
Guess what? The little Jug just
climbed out of my hand at a 30-degree angle at a slight bank. Easy as pie!
I tooled around and eventually started some mild aerobatics. After several applications of War Emergency
Power (WEP) I started hearing vibration again!
I kept the Jug aloft at ½ throttle to avoid exciting the resonant point
until the ESC kicked in. I landed and
found that the lower firewall had delaminated at the lower firewall
mounts. Darn! I packed it up and went home. Needless to say I went at that firewall hard
with the CA that evening. I also got out
my Great Planes magnetic prop balancer and balance two props to
perfection. Bench tests showed no
vibrations.
5/23/03 - Well,
last night everything came together and I got four good consistent flights on
the little Jug. Conditions were about a
7 mph steady wind and cool temps.
Launches are a snap. I dial in
half of my up trim and give it a quick push into the breeze. It climbs away easily. The flying qualities are very nice. I thought that it would be a real fast
airplane but it is quite manageable. It
will slow down nicely or burn a low pass as you see fit. Stall tests showed that it will “bob” as it repeatedly
stalls and recovers. No snap or wing
drop was apparent. That washout really
works!
The airplane
does “suffer” a little for it’s scale plan form. This is no Zagi and was not designed to
be. My Jug will wander a little in pitch
and oscillate a little in yaw after a maneuver or a buffeting by a gust. Hey, I heard that the real one did the same
thing and that is why they put the little dorsal spine on the later
models! Anyway, this is not a flaw but
more the character of a scale design. I
have yet to fly it in calm conditions to see exactly how she tracks. Power is more than adequate with WEP needed
only for towering vertical maneuvers or burning low passes.
I now fly on
higher rates than the initial settings with about ¼” elevator and at least as
much aileron. Power settings have very
little effect on pitch and this is a very welcome attribute. The flat bottom airfoil will give you a
touch of ballooning as you turn into the wind.
Rolls are very axial, pitch sensitivity is fine but if my radio had
exponential I would use it on the elevator.
Rudder effectiveness is good and the airplane will hammerhead well and
do a mean snap-roll. Spins have not been
tested. The airplane seems to loose
speed quickly during g-loaded maneuvers.
This is especially apparent in loops.
Inverted flight is surprisingly stable considering the flat-bottom
airfoil. In fact, it flies much better
inverted than my Zagi.
OK, OK, so “how
is the duration?” you are wondering. I
timed three flights. One flight at
mostly half throttle with the HEcells gave 11 minutes and 45 seconds! Wow!
The same cells with generous application of WEP gave over 9
minutes. A flight with the KR600AE
cells, with heaping application of WEP, gave 5 minutes. The HEcells purport to have more punch than
the AE cells. My qualitative testing
shows the opposite but it is a very close call.
The AE cells seem to have more punch (i.e. better current delivery,
voltage holdup, less internal resistance, blah, blah), albeit at a much shorter
duration. A test of the
Hopefully, I now
have all the bugs out of this airplane and power system. I am pleased with it’s appearance and
performance. I look forward to many calm
evenings at the field where the silence is disturbed only by Gabby’s little Jug
burning a low-pass and pulling up into a victory roll!
Duration is not
a problem. I went to the field with two HEcell packs charged and one AE pack uncharged. During the course of five flights and three
charges, I had to wait on the charger once for about five minutes. Duration with either cell type is more than
adequate. In fact, duration with the HEcell packs is longer than I would fly if this were a glow
ship! I continue to fly until ESC
cut-off. The onset of cut-off is pretty
predictable and I just reset the ESC and use ½ power
to setup for landings. At this power
setting you could even do a couple of missed approaches. I have overshot every landing so far. For a fat little warbird
with stubby wings it glides pretty well!
Needless to say, I am thrilled with the appearance and performance of
this design!
Front right
shows faux radial engine image downloaded from Jim Ryan's site.
Right rear of
the little Jug. All insignias and lettering are painted on.
Mega Motor and TMM ESC Story
I was
disappointed in the TMM controller as delivered. The unit comes with the input
side bypass capacitor loose in a little baggy. The instructions were very vague
on when/if this cap was needed. Erring on the side of caution, I snipped the
heat shrink off the controller and soldered the bypass cap onto the input power
pads. That was easy, the hard part was trying to find some of that clear rubbery
heat shrink to put the controller back together. The controller needs some kind of heat shrink
to press and maintain the heat sink to the tops of the drive transistors. I wrote Northeast Sailplane products to see
if they had some that I could purchase - no response (minus one point for NE
Sail - I guess you have to spend more than $200 to get on their radar?). I
ended up using regular battery pack heat shrink. The TMM controller also has
you do a little procedure before it will start. Turn radio on with throttle
shut (for no brake or WOT for brake), turn on airplane and wait for beep, cycle
throttle to WOT and wait for beep, close throttle and wait for beep, then fly.
Hmmm…….on my Jeti you just turn the darn thing on and fly!
During the first
run-ups of the motor I noticed several areas of audible resonance. They were most noticeable at ¼ and 1/3
throttle. They were much more pronounced
than anything my other motor produced. I
thought something was wrong and took appropriate action.
I
returned the Mega motor and TMM controller to Sal at NeSail. They sent me back another motor with the
receipt saying “motor replaced.” The
motor looked to be used. It had
scratches, dings, and gouges on the faceplate indicative of wear. Also, no box was provided with the
motor. I was not happy with this, but I
installed the motor anyway and spooled it up.
Screeeeeeeeeeeeeeeeeech!!! I am
talking a LOUD screeching sound much, much worse than the first. I put the propeller on and the noise was
damped but still there and still indicating a defective motor or
controller. I called Sal at NeSail and
he sent me to Ken Mizel at MegaMotor
Several
posts on Ezone indicate that other people experience resonance. One gentleman used an oscilloscope to
determine that the resonance points occur when the commutation frequency is in
phase with the chopping frequency. In
retrospect, there was nothing wrong with the first motor and controller. Yes it made noise at some frequencies and it
was irritating. The consensus of the
Ezone is that this is normal behavior and will not damage the motor or
ESC. It is just noise. Being a modestly experienced e-flyer, I only
had my previous experience to draw on.
My Zagi did not have significant audible resonance so I assumed that
something was wrong.
I
am still trying to get my ESC back from Mega Motor. Ken sent it to the
