Small-Field Flying-2007/12

106 MODEL AVIATION
some nice brushless
outrunners that are
perfect for small-field models in the 20- to
35-inch-wingspan range. That size model
makes the direct conversion of many
wonderful FF designs practical and works
well for some of the classic .010 and .020
glow-powered RC models of yesteryear.
Some of the suitable motors include the
AXI 2203 and 2204 series and the ELE
C20. (See the source listing.) The motors
weigh 18-26 grams and they will fly
models weighing 3.5-8.0 ounces on a twocell
Li-Poly battery pack—just right for
that FF conversion or vintage 1/4A glow
RC project.
I’m going to share several small-field
projects submitted by readers who
use these motors. The first one
comes from Glen Allison of
Tucson, Arizona.
In 1948 Glen’s
friend Rodney
Small-Field Flying Paul Bradley | [email protected]
FF designs, small brushless motors, and small-field flying
Glen Allison’s modern Baby Playboy is powered by a 23-gram
brushless outrunner electric motor.
John Krouse took a different approach
with his Plantraco-equipped model and
used a V-tail with rudder-only control.
John Krouse reports excellent turn control with the differential
control set up on his V-tail model.
Taylor built an Arden .099-powered Baby
Playboy. During that era that model was a
popular engine-powered FF design. Glen
decided to build a current-day Baby Playboy
but use RC assist and an electric motor for
power.
The model has a 33-inch wingspan—
perfect for one of the newer, smaller
brushless outrunner motors. Glen chose the
AXI 2204/54 turning a GWS 8 x 4.3
propeller as his power plant and a two-cell,
720 mAh Li-Poly battery pack as the energy
source. The Baby Playboy’s all-up weight is
6 ounces.
Glen reports that he is having a ball
flying the model as though it were an FF
aircraft. He lets it climb in a tight, right-hand
spiral pattern with no control input. It
reaches good altitude after 20-30 seconds of
motor run, and he cuts the power and lets the
airplane transition into nice, left-hand
MA author Bob Aberle offers a trimming tutorial for his electricTHERE
IS a trend I like. The makers of powered RC version of the Goldberg Ranger 30.
motors for model aircraft have been
delivering more suitable options for those of
us who like to fly in smaller spaces.
Within an increasing array of motors are
Also included in this column:
• The region between micro
and small
• Pat Tritle’s new Curtiss Jenny
December 2007 107
Using Plantraco gear, Lyn Coon converted the Randy Randolph No-Cal Piper J-3 FF
model to an electric-powered RC aircraft.
Above: Pat Tritle is at it again with a 60-inch-wingspan
Curtiss Jenny. The aged look of an old barnstormer
comes from a coat of Krylon Satin Clear.
Right: Pat Tritle indicated that flying the Jenny with its
smooth, predictable characteristics is the fun part.
circling glide. He flies hands-off with only
occasional steering to keep the model on the
field.
Very nice, Glen!
Another great small-field model taking
advantage of the less-than-1-ounce
brushless outrunner motors comes from Bob
Aberle. He is a Model Aviation Hall of
Fame member, an MA author, and writes for
a number of other publications.
As do many of us who were doing this
model-airplane thing a number of years ago,
Bob has some fond memories of aircraft that
were popular in a past era, one of which is
the Carl Goldberg Ranger 30. With a 30-
inch wingspan, the Ranger 30 was sold as a
sport model for FF or CL flying.
The intended power plant was a .020
when flown as an FF model and an .049 if
flown as a CL aircraft. Through the AMA
Plans Service, Bob acquired a copy of the
Ranger 30 kit plans and set about
developing a modern small-field flyer.
Bob powers the Ranger 30 with an AXI
2203/46 turning a GWS 5 x 3 propeller. His
battery is a two-cell, 300 mAh Li-Poly pack.
The model’s all-up flying weight is 6
ounces.
The photo of the Ranger 30 shows the
results of Bob’s work, but what you don’t
see is the effort that went into making a
successful flyer out of this nice conversion.
Not all the vintage FF designs fly right off
the board when we add the ability to control
them from the ground or alter their original
source of power. The tricks Bob applied to
his Ranger 30 project to get it into the
category of “nice flyer” are a good lesson
for us all.
On its first flights the Ranger 30
displayed an annoying tendency to roll on
its back when rudder input was applied.
That can be slightly unsettling. Fortunately
Bob was able to wrestle the model down in
one piece and set out to correct the problem.
First on the list of actions he took was to
enlarge the fin area. The original model had
a vertical fin area of 5% of the wing area.
Bob doubled that value to 10%, but the next
flight revealed that the problem still
existed.
Next Bob increased the wing dihedral.
The original value was slightly less than 6%
and he raised it to 9.5%. The combined
increased area of the vertical fin and
dihedral went a long way to help get the
model to turn properly.
Things were not perfect yet, so Bob
applied one more adjustment. Because FF
designs need much positive stability, they
often use more angular difference between
the wing and stabilizer. That can be an issue
when you want to control the model from
the ground.
Bob reduced the angular difference by
placing a 1/8-inch shim under the wing’s
TE. Rubber bands hold the wing on, so that
was not a major structural rework. Reducing
the angular difference in combination with
the other changes transformed the model into
a well-behaved small-field flyer.
Thanks for sharing your nice project,
Bob, and I appreciate the important lessons
on taming a poor-handling model. You will
find a nice construction article about this
model in the September 2007 issue of RC
Micro World. This is a great online
publication from John Worth. See the source
listing at the end of the column.
While on the subject of small models for
our small-field-flying venues, I’m going to
spend time in the region between micro and
small. I occasionally get into the smaller end
of our small-field spectrum. There are two
readers’ models that struck my fancy that I
would like to share with you. The first comes
from Lyn Coon of Arkadelphia, Arkansas.
When we think of a Randy Randolph
design, our mental image is probably of an
RC model that typically fits well in the
small-field arena. Randy was also a great FF
model designer.
One such design is a rubber-powered
profile (No-Cal) model of the J-3 Piper Cub.
Lyn’s father has been flying one. Watching
its performance, Lyn reasoned that it would
be a perfect RC conversion subject using the
micro gear from Plantraco. I have converted
a few No-Cal FF designs of my own to RC
with the Plantraco gear, and Lyn was right
on target.
Lyn used the .9-gram Plantraco threechannel
receiver. He also used the
Plantraco-supplied 90 mAh Li-Poly cell that
includes magnetic contacts to hold the
battery to the receiver. This is a slick setup
and makes battery changes a snap.
Control functions include rudder and
elevator that are handled by Plantraco
magnetic actuators. All-up flying weight for
Lyn’s No-Cal J-3 is 16 grams. I can see that
beauty in the photo floating slowly around
the back yard late in the evening.
Another Plantraco-equipment-based
model shown is the aircraft with the V-tail
and nice elliptical-planform wing from John
Krouse of Rockville, Maryland. John used
the Plantraco .9-gram receiver and 90 mAh
Li-Poly cell, as Lyn did.
John’s model has rudder and throttle
control, so he used only one magnetic
actuator. The wingspan is 16 inches and the
airplane has a flying weight of 18 grams.
What sets this aircraft apart from many
others is the use of a V-tail. John’s use of
only rudder input to control the model’s
flight direction works by setting up the
“ruddervators” to move differentially. This
is done easily with the magnetic actuator.
The photo shows that the actuator pivots
inside the electromagnetic coil so the output
arm moves the way a typical servo does.
The control is fully proportional, and you
get the differential surface movement
needed to create rudder action from a Vtail
setup.
John reports that the model has excellent
turn control with this arrangement. Very
cool, John.
Where is the Pat Tritle installment? Pat is
such a prolific designer and builder that I
almost expect something new each time I
prepare a column. My last one did not
include anything from Pat, but I’m most
pleased to report that he is back.
Not only does Pat have a new offering,
but it is special. How about a 60-inch-span
Curtiss Jenny that weighs only 23 ounces?
Pat is completely redefining the term “slow
flyer.” As you can see from the photos, this
model is a real looker.
The Jenny is powered with the low-cost,
1,000 rpm-per-volt outrunner motor from
RC Hot Deals (Tower Pro 2409-18), turning
a GWS 10 x 4.7 propeller, and a two-cell,
2100 mAh Li-Poly battery pack. Control
functions include aileron, rudder, elevator,
and throttle.
The design was set up with 1° of dihedral
so the wings don’t look “droopy.” The
wings are removable for easy transport and
can be assembled at the field in less then a
minute with only two screws.
Nelson LiteFilm covers the model and
Pat added details with an airbrush. A light
coat of Krylon Satin Clear gives it that aged
look of an old barnstormer. Keith “Sparky”
Sparks of Park Flyer Plastics did the plastic
detail parts. The fuselage script was worked
up in Microsoft Word, printed on Avery
clear label material, and applied before the
weathering was added.
Pat indicates that flying the Jenny is
the fun part. It is smooth, honest, and
predictable, although it still exhibits the
Jenny’s distinct flying qualities. With the
long, slender wing, it doesn’t like steep
banks, but by adding “top aileron” in the
turn to maintain a shallower bank, the
distinct skidding turn looks just right.
Pat reports that the ailerons are
effective and the rudder has a “soft” feel.
As with any of these old airplane designs,
there is a small amount of adverse yaw.
The model will turn on ailerons alone, but
it looks slightly sloppy.
With the limited dihedral, a rudder turn
is possible but recovery is sluggish.
However, with rudder/aileron coordination
the model will do anything a Jenny is
supposed to do. The model is fun to fly
and even shoots nice touch-and-gos
although landings are slightly “floaty” in
ground effect.
Watch Model Airplane News for a
construction article about this lovely
model. Pat indicates that short kits will be
made available when the article is
published.
Here we are again at the end of another
column. As always, don’t be bashful about
sending me a picture or two of your latest
project. In addition to the E-mail address
in the column header, you can reach me
via regular mail at 32238 Spinnaker Run,
Magnolia TX 77354. MA
Sources:
Brushless motors less than 1 ounce:
Hobby Lobby International, Inc.
(615) 373-1444
www.hobby-lobby.com
BP Hobbies
(732) 287-3933
www.bphobbies.com
Plantraco micro RC gear:
Bob Selman Designs
(417) 358-9521
www.bsdmicrorc.com
Pat Tritle’s 60-inch Curtiss Jenny:
Pat’s Custom Models
(505) 296-4511
www.patscustom-models.com
RC Hot Deals
(302) 250-4611 or (503) 708-2214
www.rchotdeals.com
RC Micro World
(703) 273-0607
http://cloud9rc.com