Flying for Fun - 2004/12

70 MODEL AVIATION
D.B. Mathews
F l y i n g f o r F u n
909 N. Maize Rd., Townhouse 734, Wichita KS 67212
IN THE LAST column I waxed
enthusiastic at considerable length about
3-D miniature electric-powered foamies.
In the interim I have begun flying mine in
a vacant lot across the street from my
home. This site is approximately half the
size of a football field, with trees on either
end. It is surrounded on three sides by
town houses.
Thus far I have encountered no
difficulty in flying from the site, and the
neighbors are only aware anything is
going on if they happen to look out their
windows or step outside. I have actually
been asked how I can fly the model
without an engine, which succinctly
summarizes the reasons behind the
explosive growth of these little electric
flickers.
Brief Notes: There seems to be some
controversy regarding how far the Li-Poly
packs can safely be discharged. Fred
Marks of FMA Direct, who imports
Kokam cells, introduced Li-Poly to us
modelers and probably knows as much
about them as anyone.
He said, “There is so little capacity left
in a cell below 3.00 volts (or 2.85 volts
under load) that it makes no sense to run
the risk of one cell in the pack being
driven below 2.5 volts.”
Don Robinson recently called my
attention to a clever and useful “vault” for
charging and storing Li-Poly cells called
the Battery Bunker. As you can see in the
photo, it is a high-heat ceramic jar with a
lid. You put the pack in it, close the tightfitting
top, hang the charging cord out of a
slot, and charge the cells.
In theory, in the unlikely event that the
pack should ignite, the ceramic will
contain the blaze and dissipate the heat.
It’s handy if you would need to leave a
pack unattended while it is charging.
These containers are available from Park
Flyer Motors, at http://parkflyermotors.com.
Construction Features: All Fancy Foam
Models kits (www.fancyfoam.com) are
constructed from CNC-milled 6mm
Depron foam (which is similar to the
foam from which fast-food boxes are
made).
All outlines, hinge lines, servo and
hardware wells, wing and tail-feather
slots, slots for the servo leads, and
channels for the carbon-fiber
reinforcement rods are precisely
premilled. Only a light sanding of the
exterior edges is required.
The recommended adhesive for
assembling the models is Gorilla Glue
(five-minute epoxy is much heavier),
which is an expanding urethane material
that certainly adheres the parts well.
However, the expansion can be a
problem.
I placed a few drops in a puddle,
waited for roughly 30 minutes, and
gauged the amount of expansion in that
time period. That was a mistake! The
adhesive expands for hours and increases
its volume many times in the process!
I carefully applied some adhesive in
the wing and fuselage slots for the
carbon-fiber rods and then left the shop.
When I returned the next morning, the
adhesive had expanded well outside the
confines of the milled slots and could not
be removed. I have jokingly said that one
could overuse Gorilla Glue and end up
trapped in the shop by the expanded
On the author's Fancy Foam Extra 300L, notice the huge ailerons, all-flying stabilizer,
and vast rudder area. Clear packaging tape was used on the hinge lines.
The kit contains everything but paint, charger, adhesives, and transmitter. All
components are of the highest quality and matched for maximum performance.
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December 2004 71
material. A little goes a long way; check a
sample after 24 hours to gauge the quantity
to use!
The models’ control surfaces are, by
normal standards, absolutely huge and are
set up with equally large movements.
Hinging is accomplished by flexing the
prebeveled hinge lines and then
reinforcing them with 2-inch clear
packaging tape on the top and bottom. But
you do this after painting the model with
Krylon Short Cuts.
This Krylon product comes in small
spray cans and is available in many colors.
Available at most arts-and-crafts stores, it
is exceptionally easy to apply,
inexpensive, and adheres well. It is not
fuelproof, but it does not need to be.
The all-moving horizontal stabilizer is
hinged in the center using a novel carbonfiber
connector rod running inside sections
of aluminum tubing. The horn is a section
of Nyrod bolted through the carbon-fiber
rod. The center-section is glued into a
precut slot in the fuselage.
Be extremely careful not to allow any
adhesive to penetrate the interior of the
aluminum tube! I suggest coating the
interior of the tube with Vaseline or a
similar product to prevent glue from
flowing inside.
The motor gearbox is the familiar GWS
350 unit, which is screwed onto a section
of 3⁄8 square hardwood embedded in the
fuselage nose. The Himax brushless motor
fits this gearbox using a supplied adapter
plate.
Assembly is highly simplified by the
precisely precut slots that allow a “snap”
fit of the components. The wing-tofuselage
alignment is cleverly
accomplished using a pair of concrete
blocks or bricks to fabricate a fixture that
holds the fuselage vertical and wing
A novel use of bricks creates a fixture to hold the fuselage and wing at right angles
during gluing. The paint and decorations are applied before assembly.
Short lengths of heat-shrink tubing provide adjustment of
pushrods. Servos and wires are nested in precut wells.
The Battery Bunker from Park Flyer Motors is a ceramic “vault”
that safely holds Li-Poly packs for charging and storage.
horizontal while the adhesive cures.
The design uses two aileron servos to
enable differential flap positions and other
mixing to be programmed in. Those and
the other two servos are adhered to the
precut wells using a craft hot-glue gun.
This hot glue is also used to adhere the
excess servo leads, etc. to the fuselage
sides.
Although a programmable computertype
transmitter is not required, the ability
to program the ailerons, add mixing, and
select levels of exponential is certainly
handy. Dick Massey, one of my flying
buddies, can only fly single-stick
transmitters, and no computer single-stick
transmitters are currently available. As a
consequence, he has been flying his CAP
with an old nonprogrammable radio with
satisfactory results. Yes, he can hover the
model.
Radio Installation: Here is simple
access. Everything is outside the model;
fishing around inside a structure is not
required. Again, there is no exhaust
residue with which to contend. CNCmilled
carbon-fiber control horns are
provided for the rudder and ailerons; they
simply fit into precut slots in the surfaces
and are glued in.
Fancy Foam Models recommends
making two Z bends in the .032-inchdiameter
music-wire pushrods to create a
neutral position between the servos and
the surfaces. However, I am not skilled
enough to accurately make two Z bends in
the same length of wire to an accurate
dimension.
Therefore, I used two shorter sections
of wire with Z bends in each, overlapped
the wire, adjusted the length inside a
section of heat-shrink tubing, and then
flowed thin cyanoacrylate into the gap.
An alternative could be to use Du-Bro
Mini E/Z Connectors on the servo horn
and a Z bend on the surface horn.
The well-detailed and photo-illustrated
printed instructions call out the surface
12sig3.QXD 10/25/04 11:07 am Page 71
72 MODEL AVIATION
deflections for all three surfaces in high
and low rates. Would you believe that
high-rate elevator is 70° in each direction?
Yes, 70°! The instructions also call for
flaperon/spoileron mix and up-elevator
with rudder to help knife-edge flight.
A “bobbin” is provided to shorten the
antenna length, to avoid hanging excess
length from the back. Without it, as tightly
as this model loops, it might actually be
possible to catch the antenna with the
propeller.
The Castle Creations speed control is a
splendid micro-sized unit with a tiny LED
that goes through a series of flashes to
signal its programming steps. The
instructions included with it go through a
step-by-step method of setting the speed
control up to match the motor and battery
pack, but this is a bit complex. It involves
setting a series of sequential flashes, and it
is easy to lose track.
I suggest developing a flow chart and
marking each step off as it is
accomplished. An alternative is an
interlink that uses a computer to set it up.
This is available as an accessory from
Fancy Foam Models.
Batteries: As I expressed last month, Li-
Poly batteries are not dangerous; not
adhering to the instructions is dangerous.
Although the programmable ESC will shut
off the motor before the battery reaches a
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dangerous discharge point, performance
becomes sluggish and you can tell that
it’s time to land before the motor actually
cuts out. It seems to sort of “hiccup” a
few times as it reaches that point.
I am unfamiliar with all of the
available chargers, but some of my flying
buddies are using units from various
manufacturers with good results. I use an
ElectriFly Triton and am delighted with it
in every way. Whatever you do, avoid
going cheap on this critical piece of
hardware!
Flying: Forget everything you’ve ever
learned about model aerodynamics! These
little foam wonders will not glide on a
bet; they have no recognizable airfoil—
only a flat plate. Turn off the power, and
they fall from the sky; they don’t stall or
spiral down in the conventional sense.
After several days of scratching my
head, it dawned on me: these things use
vectored thrust in the same way a Harrier
jet does. No thrust, no flight. No thrust, no
response to control inputs.
This makes it sound as if the models
are viciously unstable, which they are not.
Even with the power off, they don’t stall
and spin; they just sort of plop onto the
ground. Therefore, one needs to keep
power going until the model is extremely
close to the deck, and then chop it. There
is so much power to its light weight, and
the propeller is so large compared to
wingspan, that the model won’t stall and
certainly won’t snap at slow or high
speeds unless forced.
The Himax HA2015-4100 motor
running on three 1500 mAh Kokam Li-
Poly cells produces more than 100 watts
for a model that weighs only 12.5 ounces,
geared as it is in this series. The weightto-
thrust ratio is way off the chart. Flying
is done at half throttle, except for during
vertical maneuvers, yet flight duration is
12-24 minutes, depending on throttle
management.
I admit to being humbled by all of
this. But theory aside, the darn thing flies
amazingly well. Aerobatics are incredibly
tight, so one can perform all sorts of
nutty stuff right on the deck. Toss off
three consecutive outside downhill snap
rolls. If you’re disoriented at the end, hit
full up and notice which direction the
model goes in the loop, and then fly it
from the top or bottom.
These little guys are wonderful
aerobatic trainers for a number of
reasons, not the least of which are
minimal cost, minimal building effort,
and minimal damage if you do prang
them. Those virtues certainly help a
pilot’s confidence swell and motivate
aggressiveness.
In all my years of flying RC, I’ve
never had so much fun outdoors that was
not illegal, immoral, or fattening. You
and I deserve the best, and this may well
be it! MA
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