July 2007 35
A simple-to-build
RC foam flying
wing that’s easy
to personalize
BY BENNY LANTERMAN
Left: The AXI 2208-34-
powered Foamy 5 is made
from five foam trays: two
black, one yellow, two small
white. The yellow tray is the
thickest; the vertical tails are
the thinnest.
Below: Foamy 4 is the
smallest and one of the
fastest in the series when
powered by a custom CD
outrunner motor.
ONE OF THE joys of living in today’s world is that the difference
between wonders caused by science and wonders caused by magic
is getting harder to differentiate. This applies to our radio-control
hobby.
The small receivers, servos, and motors have given us the ability
to put controls on almost anything we want to fly, from airplanes
weighing less than an ounce (surely magic) to turbo jet-powered,
flame-shooting monsters (definitely magic and science).
Much of the available magic is found in our trash! The modern
foam tray used in supermarkets (and other stores) is brought into our
houses while performing its prime purpose and then
unceremoniously dumped into the wastebasket. The tray is an
airplane waiting to happen; you just have to cut away everything
that isn’t an airplane and let the magic out.
Another source of foam trays is a company such as Leftovers,
etc. here in Saint Charles, Missouri. Most larger cities have a similar
facility.
It is a recycling center that supplies free and affordable materials
to teachers and crafters, and among the many items available are
foam trays. You can find these trays in many different sizes and
thicknesses, and it might be worth eating some broccoli to get a
piece of foam with the right dimensions.
For those who are unfortunate enough to live far away from a
recycling center and who never go to a supermarket, foam sheets are
available with the product name Depron. This material is available
in several thicknesses and is a lot of fun with which to work.
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36 MODEL AVIATION
pieces of foam: one wing, one vertical, and
two elevons. (I don’t count the motor
mount.)
I experimented with single and multiple
vertical tails, rectangular- and ovalplanform
wings, more delta-looking wings,
and many different profile fuselage shapes.
The model’s configuration is your choice.
Even a fully contoured fuselage could be
made from the foam with no problems.
Let your imagination be your limit. I’ll
include a simple process to determine
whether or not your design will work before
you commit any radio gear and money to
the project.
CONSTRUCTION
The first and only step is to gather the
foam and see what you can make with it.
Well, it is almost that easy; I encourage
experimentation and variation with this
material.
As simple as the Foamy is, I don’t
recommend it as a first airplane. It is fully
aerobatic and responsive in pitch and roll.
Except for Foamy 6 (which is large, light,
and slow), this design is fairly fast.
I was fortunate enough to find a large
tray that was suitable to use as the main
wing on some of the Foamy configurations
and some small trays for the fuselages and
vertical tails. Another model was
constructed from several colors and
thicknesses of foam trays.
The foam is easy to cut with a sharp
blade, and it can be glued with any foamsafe
adhesive. I use foam-friendly
cyanoacrylate and find that I can build an
airplane in just a few minutes. When in
doubt, try a few test pieces of foam and
verify that your glue and foam are
compatible.
Butt joints seem to be strong, but if you
put a large motor on the Foamy you should
reinforce any questionable area with a small
strip of thin foam or balsa on either side. I
haven’t had any joint problems with the
airplanes that are shown.
Well, I did have one problem. I was
holding Foamy 4 fairly low by one vertical
tail (while I was busy talking and walking)
and stepped on the antenna wire. I was left
with a surprised look, a tail in my hand, and
an airplane on the ground. However, that
was the only damage and it was simple to
fix.
I have presented plans for a typical
model. Foamy 1 started out as a rectangle
and flew fine, but the angular wingtip sweep
looks nice and helps determine which way
the airplane is going at any given time. It is
unnecessary to adhere blindly to any of the
dimensions I give you; just get close.
You can use the following information to
determine whether or not your changes will
allow the airplane to fly. It is my quick and
easy method of determining your design’s
aerodynamic worth and the CG for the first
flight.
Cut and glue together only the foam and
balsa reinforcement parts of your airplane,
adding the elevons with pieces of tape. With
Foamy 1’s bottom shows red balsa stiffeners. Benny initially planned to use markers to
color the whole bottom red, but test areas on foam showed that permanent markers
would dissolve it slightly.
Foamy 1 launches nice and stable. Servos sticking through the wing’s bottom give a good
holding point for launching. They are inadequate for holding higher-power Foamys.
Whether it is tray or Depron, you should
look for foam that is 1/16-1/8 inch thick
(3mm-4mm) with a smooth surface skin.
Use the thicker size for the inner wing and
fuselages and thinner material for the outer
wing and vertical tails.
If all you can find are several smaller
pieces of foam, you can glue them together
in a pleasing geometric pattern and cut your
parts out of it. I did that with the black,
yellow, and white Foamy 5 model.
The Airplane: Foamy is an airplane—or
series of airplanes—that is based on the
low-aspect-ratio flying wing. Many vertical
tail and fuselage configurations can be
added to the basic design to get many
different looks.
The flying wings presented here are only
some of what can be made from foam trays
and are examples of how little material is
required to produce a flyable airplane. The
simplest model is made from only four
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July 2007 37
Foamy 5 in the test-glide phase. Weight is added to the nose and
elevons are adjusted until it glides well. Mark the location on the
wing bottom and use it as a safe starting point for the first flight.
Foamy 6 is the slowest, lightest version tried. Its stock GWS
motor was previously used on a Pico Stick. Note the large tip
dihedral that stabilizes the Foamy in roll, still allowing full pitch
control to be maintained.
Twin Foamy was an experiment in using twin motors. Although it
uses Jeti brushless outrunners, it would fly well with small GWS
IPS geared motors.
Foamy 2 is leaving major sonic booms in its wake. (Some imagination
is needed.) The oversized Jeti Advance ESC for Li-Poly cells was
employed to make use of what was available in the model shop.
Foamy 6 on a low pass. Its slow speed makes it a good intermediate airplane. Even though it is the slowest Foamy to date, it is still
fast compared to a Pico Stick.
Photos by the author
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38 MODEL AVIATION
Sheets of 3mm Depron (12 x 24 inches) are used to make Foamy
6. This is simplicity itself. All that is needed to finish the model is
a motor mount and radio gear.
The foam trays used to construct Foamy 4. A fairly large one was
used to make the main wing. The dashed lines are where the
vertical tails are located.
no radio, motor, or batteries, it becomes a light, simple glider.
Adjust the elevons slightly up (use tape to hold them in place)
and add weight to the model’s nose to balance the airplane at
roughly 20% of the wing chord. Make adjustments to the nose
weight and elevons until the aircraft glides nicely. If you are really
off in your CG guess, the foam glider will gently flop to the floor.
Once you get an okay glide, mark that CG location on the foam
wing. Add the radio gear, motors, and batteries in the proper
fashion, per the manufacturers’ recommendations.
I won’t get too detailed with installation notes since the Foamy
shouldn’t be considered as a first model. A design such as the GWS
Pico Stick would be a better choice. (Mine still works fine after
many years, motors, and flights.)
Move the various pieces of equipment around to keep the CG in
the same location as on the nonpowered glider, and use sticky-back
Velcro to fasten the receiver and ESC. Use the photos as a general
guide for equipment locations. You can temporarily tape the
receiver, servos, etc. in place to see if the CG is going to work.
Cut holes in the wing and push the servos through with a bit of
glue to hold them in place. Set the initial elevon deflections (you can
use tape or your favorite hinges on the elevons) to be the same as
used by the glider. The model (if not the pilot) will be in fine shape
for the first flight.
I have used motors ranging from the little workhorse GWS IPS
geared units and hand-wound CD-drive conversions to the elegant
brushless golden anodized AXI 2208-34. With any lightweight
equipment the airplane will weigh less than 4.5 ounces without
batteries.
I have used a small seven-cell, 280 mAh NiMH pack with the
GWS motor system and two- or three-cell, 700 mAh Li-Poly packs
for the brushless motors. I selected propellers per the motor
manufacturer’s suggestions.
I have been using the small, single-conversion receivers that
GWS and Hitec make. I have used a large variety of ESC brands,
but I have used the Jeti the most. In each case the unit has been
appropriate for the motor and battery pack. Use string to tie down
any loose wires so it looks fairly neat.
The motor is attached to a hardwood stick with balsa fill added
as necessary to fit the power plant that is used. Although we never
crash, remember that the stick should be the weakest link—weak
enough to break instead of the motor on those rare nose-down
arrivals.
Flying: The magic takes wing at the flying field. A gentle toss will
set the airplane flying straight and level. Trim as needed and be
prepared to have a great deal of relaxed fun. With almost zero cost
in materials for the airplane, the scary part of flying disappears.
Take along foam-friendly cyanoacrylate and kicker to do field
Type: RC sport electric
Wingspan: 24 inches
Weight: 4.5 ounces (without batteries)
Wing area: 268 square inches
Length: 12 inches (without motor)
Power: AXI 2208-34 motor with 30- to 50-watt output, 8-
to 10-amp ESC, two- to three-cell, 800 mAh Li-Poly
battery
Radio: Three channels minimum with two microservos
Construction: 3mm-6mm foam
Covering/finish: Magic Marker, foam-safe paint
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July 2007 39
Full-Size Plans Available—See Page 215
07sig2.QXD 5/23/07 10:55 AM Page 39
repairs, and fly all day! The large, flat
piece of foam is a great-flying airplane
with flight characteristics dependent on
weight, size, and power.
There is one thing to watch out for (and
the embarrassing reason why I almost
called the model the “Whacker”). Make
sure you have a good grip on the Foamy
when checking the motor.
I was holding the airplane too loosely,
and it pivoted in my hand enough to allow
the propeller to hit the heel of my hand
several fierce whacks. A half dozen oozing
cuts put home the lesson: the little motors
should be treated with care and respect.
A large, light Foamy 1 or Foamy 6 with
the small GWS motor flies gently. It might
loop if you hold the dive long enough and
are lucky. It will roll more easily, but not
all that well. It is a bit like a butterfly, but I
have flown one in nearly 15 mph winds.
Using the tip dihedral makes the airplane
roll stable and helps the more
inexperienced pilot.
The same airplane with an AXI
brushless motor is a different machine.
Straight flight under full power is
surprisingly fast, yet slow flight is still very
nice. You can do continuous loops and
rolls, and go straight up for a long time.
Foamy 1 has made many flights and, as
the resident test bed, received my first
small brushless motor. While doing a
series of fast, small loops on its first flight,
I noticed it was developing more and more
dihedral until the wing folded in the center.
I throttled back and the Foamy slowly
fluttered down and settled on the runway
(another good thing about the light foam
wings). I put glue in the break and added
a 1/16-inch-thick, 2-inch-wide balsa wing
spar at the 25% chord position. In the
photos it is seen as the red-markered area
under the wing. No problems have
resurfaced since that addition.
Foamy 4 with the Custom CD or small
AXI brushless outrunner motor is a true
speed demon with amazing looping and
rolling performance. For this variation I
recommend the thicker foam.
Performance in the wind is great, and it
will be flying when other types of models
are grounded.
The other Foamys have varying
components and characteristics. They
have been a lot of fun to fly. Each one is
different and leads me to try something
else. No boring airplanes here!
I am presently wondering how
rounded surfaces would look and thinking
about the benefits of a full fuselage. A
single tail would be okay too, if you like
that kind of configuration. A recent
addition has been the twin Foamy that is
shown. It flies nicely and has a great twin
sound.
Something fun and educational is to
take one of the models, scissors, extra
pieces of foam, tape, foam-friendly
cyanoacrylate, and cyanoacrylate kicker
to the flying field. There you can
experiment with wing extensions, wing
strakes, vertical tail sizes, control-surface
sizes, and anything else you can think of.
What you can do is limited only by how
much magic you are willing to let out of
the foam. MA
Benny Lanterman
[email protected]
