60 M ODEL AVIATION
Construct this jet
from inexpensive
sheet foam
MiG-15
n Tony Peters
Expanded polystyrene sheet
foam is excellent construction
material for Fun Scale profile jet
models, such as this MiG-15.
The author looks up admiringly at his
handiwork as it scribes a steady,
predictable flight pattern. It’s a fun model.
A good launch angle is critical for
establishing the proper flight profile.
The author has this down to a science!
Action shots by Matt McCarthy Static shot by Author
60 M ODEL AVIATION
May 2001 61
love building model airplanes. There is something wonderful
about turning a flat drawing and bits of wood and tissue into a
three-dimensional sculpture that magically flies through the air.
For years I churned out model after model, hanging them wingtipto-
wingtip in my summer home and in my son’s bedroom.
Now that I am more or less retired, I have little time to
build. Those of you on the working side of Social Security will
scoff at this—I know I did—but most of my aging peers are
probably nodding in agreement.
Some time ago a neighbor—a retired building contractor—asked
me how I liked being retired and whether or not I was making lots of
new models. I told him how busy I was and how the days seemed to
slip like sand through my fingers, leaving me little time to build. He
thought about that for a moment.
“Put on more men,” he advised me.
This has become my geriatric cohort’s motto, but there is a better
solution to the embarrassment and boredom of showing up week
after week with the same tired models: a foam profile model.
These models have other advantages than quick and easy
construction: they are cheap (a personal favorite feature);
they’re sturdy (my MiG has survived countless collisions with
walls and table legs, was knocked out of the grasp of trees with
a wildly flailing pole, and even spent a rainy week in a tree as it
worked its way down to where I could get at it); and last but not
least, they look really neat.
CONSTRUCTION
You will need some sheet foam to start with. Don Ross advised
me that Aerospace Composites (Box 16621, Irvine CA 92714),
Kenway Microflight (Box 889, Hackettstown NJ 07840), and Peck-
Polymers (Box 710399, Santee CA 92072) have it. You could also
try disposable foam dinner plates, take-out food containers, or trays.
Many of these inexpensive alternates are too small for a
whole wing or fuselage, but they can be butt-joint-glued
together. The joint should be strengthened with a skin of glue
and, if you like, reinforced with Tyvek®.
Tyvek® is like a plastic-reinforced paper, most easily accessible
as FedEx® or Express Mail envelopes. You can cut the material
with a razor or scissors, but you cannot tear it. I split it with a razor
blade (Figure 1) and glue it fuzzy-side down.
I have a few words about glue and Tyvek®. For gluing
foam, you can use any number of water-based white glues and
some solvent-based glues, such as Goo-Loo and Duco®. I use
a water-based acrylic clear varnish to attach the decorations
(such as the red tissue-paper stars).
Whatever you use, test it on a bit of scrap first!
Now we’re ready to build.
Cut the parts from the plan. The fuselage and the lower half of
the vertical fin are one piece, you only need one wing, and don’t
bother with the wing fences. Cut two small square holes in each
pattern, and use them to tape the pattern to the foam.
The fuselage and wing are from thicker foam (2mm in my MiG),
and the tail and fences are from thinner foam (1mm). Cut out the
foam with a new X-Acto™ or razor blade.
After you’ve cut the fuselage outline, cut the wing-mount space
and the airfoil (Figure 2). The first 5⁄8 inch of the nose is balsa to
match the thickness of the fuselage foam. Glue the balsa nose to the
foam, and round all the edges. (There’s no engineering or
aerodynamic reason for this; I just like the way it looks.)
The motorstick is 1⁄16 x 1⁄4 hard balsa, and it runs from the
nose to the rear of the fuselage. The motor mount is a sandwich
of three bits of 1⁄16 balsa and a 1⁄8 hardwood dowel, drilled for
the prop hook (Figure 3).
There are a number of ways to make easily and subtly adjustable
motor mounts. The problem—for me—is that a mount that is “easily
and subtly adjustable” is also easily and subtly nonadjustable, then
for some mysterious reason your model isn’t doing so well …
With my motor mount it’s either the way I set it or it’s
broken off. I change the thrust adjustment by slicing off the
mount and regluing it. It only takes a few minutes for the wood
glue to dry, and I can fly another model or schmooze (modelflying
is a very social thing, after all).
Figure 2
Figure 1
Figure 3
Figure 4
Figure 5
Figure 6
Wing
Airfoil
Shape
Tyvek®
62 M ODEL AVIATION
The rear motor mount is a loop of wire sandwiched between
the motor mount and a bit of 1⁄16 balsa, and secured with
Tyvek®. The motor mount is glued onto the fuselage between
the marks on the plan.
(I put my motorstick on the right side because I’m right-handed,
and I don’t want to see the motorstick when I hold up my model to
admire it. You can do whatever pleases you.)
The skin, which is an artifact of the manufacture of sheet foam,
imparts a good deal of the strength. To get a good glue joint, sand it
a bit where the motorstick goes on the fuselage and where the
horizontal stabilizer sits on the fin.
Cut out the wings and, holding them back-to-back, sand them to
match. While still holding them together, trim a little bit of airfoil
shape. Hold the wings together so that you will positively make one
left and one right wing the first time.
Sand the airfoil on a flat surface (Figure 4). A foam profile
model will fly nicely with a flat wing (you don’t even need an
airfoil), but it will fly slower and longer with an undercamber.
To put in the undercamber, gently roll the wing on a large dowel
(Figure 5). You don’t need much—just enough to match the wing
airfoil shape you cut out of the fuselage.
Fold a strip of Tyvek® and use a triangle or the end of a ruler
to make a sharp crease. Cut a 1/4-inch-wide strip, and glue it to the
wing leading edge (Figure 6).
It’s important to glue the wing straight on the wing airfoil shape.
Draw a line, and wedge the airfoil between scrap balsa to hold it in
place (Figure 7).
Glue the wings to each other and to the airfoil, and hold them down
with pins (Figure 8). Reinforce the joint with Tyvek®.
The wing fences have to be custom-made to fit the top of the wing.
Hold a piece of foam over the wing, and transfer the curve with a felttip
pen in a compass (Figure 9). Use the compass to mark the height of
the fence (Figure 10), and trim the ends to match the plan.
Cut out the thin foam tail, and cut the radio mast from thin plastic.
Finish and Markings: Mask off the red stars, leaving a white
border, and spray everything silver. Also spray some Tyvek® silver,
so you can use it to reinforce the wing mounting.
I sprayed my MiG with a water-based acrylic, but I have used spray
cans on other models. Test it first; some solvents, such as dope, will
melt foam the way Dorothy melted the Wicked Witch of the West.
Add the red tissue-paper stars and draw all the panel lines,
doors, control surfaces, and gun blisters with a non-waterbased
felt-tip pen. Don’t do the back part of the canopy above
the wing until it is in place.
Cut the number and canopy from black Con-tact® paper.
Score both sides of the rudder and elevator hinge lines so you can
bend them neatly for trimming.
Put the wing into the fuselage and reinforce the joint with a strip
of Tyvek®, glue the horizontal stabilizer to the fin and the rest of
the fin on top of that, and make the propeller while that’s drying.
Cut the prop blades from a clear-plastic cup from the take-out
department of your local supermarket, and insert them into slots cut
in a balsa hub with 1⁄16-inch-square stops for the prop hook (see
plan). The hole for the prop shaft is lined with metal or plastic
tubing, or with a drilled bit of hardwood dowel.
Flying: Each model is different and has to be trimmed individually.
Because I fly mostly indoors and on small fields, I trim my models
to fly right. I needed some right-thrust to do this.
My MiG is very sensitive to right rudder; too much keeps it from
climbing. With long, thin motors indoors, it needs up-elevator; with shorter
motors outside, it has a marvelous climb and a long, floating glide.
When the MiG-15 appeared over Korea a half-century ago, it
was an unpleasant surprise for the United Nations airmen. I’ve been
flying my MiG for half a decade, and watching it circle serenely
overhead has been a constant source of pleasure.
Keep ’em flying. MA
Tony Peters
303 W. 66th St. #12C-W
New York NY 10023
Type: Sport Scale profile FF
Wingspan: 16 inches
Flying weight: 14 grams
Construction: Sheet foam and balsa
Finish: Spray water-based acrylic paint
MiG-15
Figure 7 Wing Airfoil Shape
Tyvek®
Trim Excess
When Glue Dries
Figure 8
Figure 10
Figure 9
Foam
Wing