Small - Field flying 2003/05

WHAT DO YOU get when you combine an
interest in Free Flight (FF) with small-field
Radio Control (RC)? Michael Burdette of
Pleasant Hope, Missouri, has a great answer
to this question. Starting with Peanut Scale
plans for a Sopwith Triplane and a ruler, he
developed a gorgeous Scale small-field flyer.
In case you are unfamiliar with the term
“Peanut Scale,” it is a category of rubberpowered
Scale FF models with a wingspan
All this was combined to result in a
“large” (easily seen high and far), low-cost,
slow- and easy-flying E-craft that can rise-offground
(ROG) and that’s easily maintained
and easily repaired.
An early goal was to use a seven- or eightcell
pack in the 1700-3000 mAh range in the
Stikum. This was driven by the ready
availability, popularity, and moderate cost of
such packs. I also wanted the battery to be
easily accessible for flight-to-flight swapping
and for other reasons, which follow.
I elected to use a proven, quality geared
motor that was readily serviceable, had
replacement parts available, and had robust
gears that would not fail with the normal
propeller strike that so often occurs. Some
would see my choice of the classic geared
Astro 05 as not being low in cost, but it is
very much so in the long run; it lasts and lasts
and lasts.
Stikum had to accommodate all of the
bumps and bruises that trainers typically
sustain, so the wing and tail surfaces are
rubber-banded on. The thinking is that if it
gives some, it’s much less likely to break.
Ground loops can be hard on fixed tail
surfaces—but not on Stikum! The wing
dowels are oriented so that the wing pops off
more easily with frontal impact. These
approaches are nothing new; that’s how it was
done in the 1950s!
The battery, so positioned and held with
Velcro, can fly free upon impact, and that
precludes essentially all of the associated
damage that typically occurs during a nose-in.
(It’s nearly impossible to secure an internal
battery so well that it cannot break loose and
plow through everything in front of it in a
“normal” fuselage.)
Also, the Sermos connectors used simply
separate, thereby not encumbering the on-
May 2003 105
Simple “servo saddle” mounting plate, pushrod guide tubes,
support structure for the latter—nothing complicated.
Rubber-band-held tail assembly is not unlike the way it was done
50 years ago—much harder to damage in a mishap.
limit of 13 inches. Michael doubled the plans
size to yield a model with a 26-inch
wingspan, then he performed an equipment
transfusion from a Lite Stik and ended up
with the wonderful model you see in the
photos.
Construction is all balsa with a little light
plywood for strength where needed. The
model is covered with clear-doped craft
tissue. The markings are hand-cut from
colored tissue. The complete equipment
installation includes the GWS DX-A motor
package from the Lite Stik, a seven-cell 270
mAh NiMH battery pack, a GWS speed
control, a Hitec Feather receiver, and two
Cirrus CS-10 servos. The all-up flying weight
is 91⁄2 ounces. It’s very nice.
Michael reports that the model flies well
in indoor or outdoor venues. With all the
Peanut Scale plans in existence, it sure would
be nice to see some other models transformed
into small-field flyers. Mike, are you reading
this?
Since electric power is so popular for
small-field models, I want to let you know
about a new battery offering. Some exciting
things are happening in the computer and
mobile-telephone world that are having a
direct and positive impact on our world.
May 2003 83
Paul Bradley
S m a l l - F i e l d F l y i n g
32238 Spinnaker Run, Magnolia TX 77354; E-mail: [email protected]
Michael Burdette doubled Peanut Scale Free Flight Sopwith
Triplane plans to develop this beautiful small-field flyer.
Michael’s 26-inch-span Sopwith Triplane is powered by a GWS DX-A motor/gear drive
and weighs 91⁄2 ounces. It was constructed from balsa and light plywood.
For the author’s Top Flite Rascal 18 project, the motor simply
plugs into a piece of dowel glued to the nose block.
One is in battery technology.
In recent months a great deal of
excitement has been generated by the use of
lithium-polymer cells for powering the
smaller electric-powered models. This battery
technology offers notable increases in power
density values for electric propulsion. The
downside has been a limit on the amount of
current the cells can deliver. Fortunately,
lithium-polymer cells are emerging which can
be used for models that need a bit more
power.
Joel Maxwell and his company J&N
Performance Electric has recently started
offering a dual-cell lithium-polymer battery
pack from DynaPac along with an appropriate
charger. The contact information is in the
source listing at the end of the column.
The cells produce 7.6 volts and have a
capacity of 640 mAh. The great thing about
these packs is that they weigh only 33 grams
and can deliver 2 amps continuous with peaks
of 3 amps. This really opens the door to a
wide range of small-field subjects in terms of
offering a lightweight, high power density
electric power source. I think it is safe to say
that lithium-polymer battery technology will
move electric forward as a viable power
source for model aviation.
Have you noticed some of the new offerings
from DJ Aerotech? You may recall my
84 MODEL AVIATION
discussing a fondness for profile models in a
past installment of this column. Included in
that discussion was mention of a P-51D I
built from a DJ Aerotech Roadkill kit.
The little profile beauties in the Roadkill
series have proven quite popular with the
small-field/indoor crowd. As a result, Don
Stackhouse and Joe Hahn—the guys behind
the company—have added two additional
categories to the Roadkill lineup.
Complementing the original World War II
models are selections from World War I and
classic civilian aircraft.
Any of the models from the Roadkill line
make nice small-field flyers—especially if
you add a lithium-polymer battery as the
energy source. The lighter weight and
greater power density of the newer cells
really bring the Roadkill models to life. Take
a look at the lineup.
My Rascal 18 Project—the Final
Installment: In the past two columns I have
given you a peek at a project that has been
the combination of a trip down nostalgia
lane and modern micro RC gear. My efforts
have been to develop a replica of the old Top
Flite Rascal 18 then convert it to an electric
RC small-field flyer. I’m happy to report that
the project has reached a successful
conclusion. The electric-powered RC Rascal
18 is gracefully flying about my back yard.
I have included a few pictures to give
you an idea of how the RC version of the
model went together. The motor is a
Mabuchi M20 sporting a homemade 4.2:1
gear drive (thanks to my brother Ralph), the
receiver is an RFFS-100 from Dynamic Web
Enterprises, the actuators are from Bob
Selman, and the battery pack is a single-cell
190 mAh lithium-polymer unit. The all-up
flying weight is 30 grams.
One unique feature is the method Ralph
set up for mounting the motor. The
propeller-shaft support simply plugs into a
slightly tapered hole in a piece of dowel that
is glued to the nose block. This allows the
The RFFS-100 receiver from Dynamic Web Enterprises, Bob Selman actuators, and
lithium-polymer battery fit nicely in the author’s Rascal 18’s tiny fuselage.
Ready to fly, the author’s Rascal 18 conversion project weighs 30 grams.
motor to be easily inserted into or removed
from the model. Watching this airplane float
around my back yard has resulted in many
smiles on my face.
In wrapping up the Rascal 18 discussion,
I’ll share a story from one of the people who
helped with the original kit development. In
response to the January 2003 column in
which I first mentioned my Rascal 18
project, I received a great note from Ed Mate.
In his youth he had the opportunity to be part
of the Rascal 18 development team.
Following are his recollections.
“Your Rascal 18 Jigtime story really
struck a chord. In 1950 I was studying
architecture and needed a summer job to help
with college tuition. The magnet of model
airplanes was stronger than that of what I
was studying, so when my classmates went
to work for architects for the summer I
decided I wanted to work for the great Carl
Goldberg. His company at the time was
American Hobby Specialties. Reading this
sign on the door I walked in and asked to see
the master. Soon Carl appeared and I nearly
begged him for a summer job. I was 18 years
old.
“He handed me a notepad and a pencil
and pointed at the Rascal 18 prototype on a
display table in the general office area. He
told me he would be back and that I should
make a perspective sketch of the Rascal. He
would decide when he saw the sketch. Thank
God for the gift he gave me of drawing
ability. After a slight correction (which Carl
always did) I passed.
“He explained that I would work on his
dream of a beginner’s model airplane that
would be guaranteed to fly. That it would be
called Jigtime because the parts would be so
designed that they would only fit one way,
the right way.
“He said we had to design a total of four
models. He already had picked the Stinson
Sentinel and the Piper Vagabond for two of
the remaining three. He asked me to think
about what the other airplane should be. But
right now we were to go all the way with the
Rascal to produce a test model for testing
with teenagers. It would go on the market
alone for this purpose.
“Bill Ehrlich and myself would take hand
cut parts, assemble the new Jigtime
prototype, and then do the most critical
drafting operation, the die drawings that
would be rubber cemented and shellacked to
3⁄8 inch plywood so a jigsaw genius could
split a saw cut with our .005 lines for
razorblade stock. Thus we had our Jigtime
parts dies. Later we would add rubber stamp
material to print the color pattern to the balsa
as it was die cut. The wing had a separate
operation to form the airfoil section curve
into it. The only non flat part in the kit.
“We had it ready for the market in about
three to four weeks. But first we would test it
with Boy Scout groups. Not too good. The
kids were not paying any attention to the