RADIO CONTROL SLOPE SOARING - 2004/08

108 MODEL AVIATION
FOAMIE SLOPE sailplanes have gotten
much better looking in the last year or
two, and they have made steady
performance gains. They have even
generated a Foamie Warbird Racing class,
which the Inland Slope Rebels out West
(www.inlandsloperebels.com) originated
and the Lincoln Area Soaring Society in
the Midwest supports at the Midwest
Slope Challenge (home.alltel.net/mwsc).
The “Look good, go fast” bug has bitten
my flying buddies in the great Northeast
as well.
By my reckoning, and as of this
writing (spring 2004), we now have kits
available for a “third generation” of
foamie warbirds. Pat Bowman started the
ball rolling in roughly 1995, when he
learned that EPP foam could be cut to
shape with a hot wire. He made great use
of the rugged material’s properties in
Bowman’s Hobbies kits (www.bowmans
hobbies.com).
The first generation of foamie
warbirds burst onto the scene with Dave
Sanders’ (www.davesaircraftworks.com)
prolific series of foamie combat warbirds.
Hundreds of Slope pilots built and flew
Dave’s Foam 51, foaMe-109, and
Kawafoamie Ki61, and showed us how
good a foamie could look in iron-oncovering
“war paint.”
The second generation of foam
warbirds had bulkier (more scale-looking)
Dave Garwood, 5 Birch Ln., Scotia NY 12302; E-mail: [email protected]
RADIO CONTROL SLOPE SOARING
Brian Laird’s (Moreno Valley CA) Air-Rage
Reno Racer at Cajon Summit 2003. He has
turned his attention to making the
foamies look better and fly faster.
Larry Purdy (Russell KS) launches Erik Eaton’s (Hays KS) SR Hobbies MiG-3 during
foam warbird combat heat at Midwest Slope Challenge 2003. Joe Chovan photo.
Best Foam Awards at Cajon Summit 2003 (L-R): Ren DiLeo, scratch-built Messerschmitt
Bf 109; Jack Cooper, scratch-built SR-71 Blackbird; Brian Koester, scratch-built Sukhoi
Su-35; Jack Mullen, scratch-built Bell X-1 FSW; Rick Schwemmer, Leading Edge Gliders
P-51 Mustang.
A secret to designing and building a good-looking foamie is to put all components on
the inside. Jack Cooper’s P-40 Warhawk fuselage is under construction.
08sig4.QXD 5/21/04 12:04 pm Page 108
110 MODEL AVIATION
fuselages and thinner airfoils (less drag),
and they were speedier. I saw Steve
Patton’s (home.earthlink.net/~pattonacft)
Focke-Wulf Ta 152 clocked at 109 mph in
a dive at Cajon Summit.
Steve’s Messerschmitt Me 262 had the
first really scale fuselage I remember
seeing, along with his trademark thinner
section wing. Jack Cooper’s Grumman
Hellcat also had a fat fuselage—it truly
looked the part—but still had a wide-chord
wing, which gave plenty of lift but limited
its top speed.
Jack’s Hellcat was the first kit I saw in
which fuselage components disassembled
to mount the internal components, and
were then glued together for completion.
Now we had all of the control linkages
mounted internally for reduced parasitic
drag and smoother appearance.
Then in May 2003 I saw and flew my
first “third-generation” foamie: Brian
Laird’s original-design Air-Rage Reno
Racer. Man, there was a lot to like about
that airplane. It had a fat fuselage and a
thin, narrow-chord wing. Over the
strapping tape was Solartex iron-on
covering and a painted finish. I couldn’t
tell it was a foamie from more than a few
feet away. It was heavy and flew fast, all
the while tracking like it was on rails.
Brian is perhaps the most prolific Slope
Soaring warbird designer in the country
today, having produced maybe 20 designs
in molded fiberglass with sheeted foamcore
wings under the “Slope Scale” brand
name (www.rcglider.com).
It was a happy day for foamie fliers
when Brian applied his talent and
experience to foam—especially for those
who wanted to fly fast and look good
while doing it. He did the basic design
For easy replacement, one end of a pair of aileron servos are
screwed to a wood block glued to Dave’s P-40’s wing spar.
Dave’s method for making strong internal elevator control horn
was first published in July 2003 Model Airplane News.
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August 2004 111
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work for three 60-inch-span Foamie
Warbird Racing-class sailplanes, and
then Jack Cooper at Leading Edge
Gliders (www.leadingedgegliders.com)
developed and kitted them.
Most of the third-generation foamie
warbirds are not combat rated because
they have balsa tail parts. They are
designed for racing and sport-flying, but
because of the predominant EPP-foam
construction material, they’ll resist
collision and crash damage that would
put a fiberglass sailplane on the repair
bench.
In addition to the fatter fuselages,
thinner-section airfoils, and narrowerchord
wings, third-generation sailplanes
tend to have stiffer fuselages and a
painted finish. Because these gliders are
not used for full-contact combat, they
are likely to have a longer service life.
We’re more willing to put more time
into building them, and because the
fuselages don’t turn to mush as quickly,
they may live long enough to have
internal components wear out and need
replaced.
I will present some ideas on how to
make your airplanes look better by
moving linkages to inside the fuselage
and suggest mounting servos and the
receiver so that they are easier to remove
and replace than the traditional “glued
into a foam cocoon” method we used in
our first foamie warbirds.
A photo shows my Leading Edge
Gliders P-40—a 60-inch-span foamie
warbird racer—under construction.
Notice the pair of carbon-fiber tubes
inserted along the fuselage centerline to
stiffen the structure. The servo shown
controls the elevator, and its control
snake is completely internal.
The receiver slides into a tunnel so it can
be removed for testing and replacement if
necessary. The receiver battery pack is
permanently mounted, but since the
fuselage may have a long life span, I
installed a large-capacity (1200 mAh),
high-quality battery pack made by SR
Batteries (www.srbatteries.com).
Another photo shows the aileronservo
mounting on the upper side of the
wing. I used a pair of Airtronics
(www.airtronics.net) 94831 servos
because I may rig this model with
spoilerons and because I had them in
stock. Since I used another 94831 for the
elevator, one spare servo in my toolbox
will suffice to replace any of the three,
should it come to that.
When building a foamie, we have
traditionally wrapped a servo in masking
tape and glued it (permanently) in place
with Goop. This holds the servo fine, but
it’s no fun to remove it when it needs
repair or replacement, or to “harvest” the
radio gear for a worn-out airframe at the
end of its service life.
On balsa and fiberglass airplanes we
use wood mounting rails or a plywood or
plastic servo tray to mount servos with
screws so that they are easy to remove.
Why not try the same methods in our
foamies?
For this installation I used a
combination of mounting methods: screws
and Accu-Cut foam. I situated the servos
so that at the rear they could screw into a
wooden rail glued to the spar, and I cut the
cavity in the foam extremely carefully to
assure that there was firm pressure from
the springy EPP foam to further hold the
servos in place. The screws fix the servos
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ELEVONMIXER
08sig4.QXD 5/21/04 12:05 pm Page 111
116 MODEL AVIATION
against fore-and-aft movement, and the
foam pressure keeps them from wiggling
side to side.
I’ve already removed the servos once,
to apply strapping tape to the wing, and it
took less than a minute, with no
degradation to the mount itself and no
danger of damaging a cable with a blade.
Although I had intended to install rails
and use screws to mount the elevator
servo, there was no handy structure to
attach the rails to. So I wrapped this servo
in tape and glued it in place, as I’ve done
on many foamies.
I put glue only on the two long sides of
the servo, and I mounted it in a place
where I can easily get to it with the wing
removed. (This glider has a bolt-on wing.)
When I need to remove that servo, I’ll run
a knife along its sides to free it from the
glue, working carefully not to damage the
cable.
The next item is an internal elevator
control horn. An external control horn and
a clevis poking out the side of the rear
fuselage is jarringly visible to me when
launching a Slope warbird, but it doesn’t
take much to move the horn inside the
fuselage and out of sight. We already
know how to make internal aileron control
horns; that’s the norm for many balsa and
fiberglass kits. We just need to apply this
method to our foamies.
For a 48-inch-span warbird, the
materials needed are soft steel wire stock
from a 2-56 threaded control wire and 5⁄32-
inch-diameter brass tubing. For a larger
sailplane, you may want to use thicker
wire and larger tubing. The parts are
shown, and the steps are:
1) Cut the wire to the required length—
likely 6-8 inches.
2) Cut the brass tube to the required
length—roughly 1 inch.
3) Bend the wire in the center to double
it over.
4) Bend the wire halves 90°, leaving 1⁄2
inch for the lower part of the “T.”
5) Accurately align the wire halves to
make an accurate “T” shape.
6) Flatten 1⁄4 inch of brass tube, grind it
round, and drill a hole for the clevis.
7) Hold the brass tube in a vise, and
install the wire “T” with a light hammer.
8) Solder the wire inside the brass tube
for extra security.
9) Bend the ends of the wire to fit the
elevator halves and trim to length.
The final upgrades to improve the new
foamie warbird’s appearance are spackle,
Solartex iron-on covering, and a painted
final finish. Some advanced builders apply
a coat of drywall-patching “light spackle”
(which is available at the hardware store)
after final-carving and -sanding the foam,
to fill the small voids between the foam
beads and to repair chunked-out foam
areas.
When the spackle dries, final-sand the
surfaces, spray on the 3M Super 77 contact
cement, and apply the strapping tape as
carefully as you can. Any strapping-tape
overlaps may show through the final
covering.
The high-end builders use Solartex
fabric covering because it’s tough. After
the material is applied with a heating iron,
the airplane gets two, three, or four coats
of sandable primer paint, with wet sanding
between coats, to fill the weave of the
fabric.
Last, spray on the final color coats.
Selecting accurate paint colors really gives
an impression of scale realism. On my
current P-40 Warhawk project, I’m using
the new series of Tamiya aircraft colors in
3.25-ounce cans (www.tamiya.com). The
new paint is looking great and working
great in paint compatibility tests so far; I
have yet to finish this project.
What’s next for improving the appearance
and increasing the performance of Slope
warbirds? How about CNC (Computer
Numeric Control) machining to shape the
parts? At least one manufacturer has
announced that he will make kits using that
production method. For a glimpse into the
future, visit the Plane Insane Models Web
site at www.planeinsanemodels.com. MA
08sig4.QXD 5/21/04 12:06 pm Page 116