Small-Field Flying - 2004/12

74 MODEL AVIATION
Chris Poole, who lives in the high
elevations of Colorado, ran into this
problem with the Tower Hobbies Uproar.
The model had the features he was looking
for, but the kit produced a model that was
not suitable for his small field. Being an
innovative 16-year-old, Chris did not let
the unavailability of a kit for the size
airplane he desired stop him from having a
small-field version of the Uproar.
Chris developed plans for the aircraft at
the reduced dimension. The result of his
efforts is shown in the photo. Power for
the model comes from a direct-drive
Mabuchi 280 electric motor turning a 5-
inch Gunther propeller (the type used on
the Zagi). A two-cell 720 mAh Li-Poly
battery pack supplies the power. The
airplane has full-house controls, using
three HS-55 servos coupled to a JR
Electron 6 receiver. With a wingspan of 24
inches, Chris reports that the model is a great flier.
It’s nice to have such a young modeler who is not intimidated
by having to rescale a model and then take on a scratch-building
project to achieve a desired result. Our hats are off to you, Chris.
Probably the more common approach to rescaling a given model
design for a different venue is to make it smaller. The many great
designs from the early days of model aviation tended to be large,
and they are a common source of designs that are scaled to a
smaller size. We certainly have some excellent examples of this
being done for the small-field-flying community. Less common
but equally valuable is to make a small model larger.
It is truly amazing to see what some of the people who are
capable of building the small and really small micro RC models
can achieve. Many of these designs are quite appealing. These
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]
“THAT’S TOO BIG for my small field.” How many times have
you looked at a model and said to yourself, “I would like one of
those but it is too large for my small-field site”?
There are numerous models sized for 40 glow power or larger
engines that look appealing. Unfortunately they don’t normally
come in a size that is more commonly used for small-field flying.
Chris Poole decided that the Tower Hobbies Uproar would make
a nice small-field model, so he scaled it down in size.
Sam Will, of Phoenix, Arizona, has developed two printed-balsa all-sheet models that
are larger versions of the author’s reproduction drawings.
The author has converted the rubber-powered FF Frank Macy
American Junior reproduction Hornet to RC.
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models, though, may require an indoor site or weather conditions
that are not available to all of us. In that case, making the model
larger often allows the design to be suitable for our individual
flying-site situations.
Following this thought process, I received a photo from Sam
Will, who resides in the Phoenix, Arizona, area. As do many of
us, Sam has some nice memories of the old all-sheet-balsa Top
Flite Jigtime models. When he saw the reproduction drawing
packages of those great old designs available on my Web site
(www.parmodels.com), he jumped in with both feet.
Sam found a suitable computer ink-jet printer—an Epson
960—that could handle the balsa-printing function. In no time, he
was turning out a set of the rubber-powered Free Flight
reproduction models. Sam is also an RC flier, so it did not take
long for him to decide to adapt the Jigtime models to radio control.
The Jigtime models make nice micro RC airplanes in their
original size. Sam was interested in a larger-size model for his
flying site. His printer is capable of handling balsa sheets up to
3⁄32-inch thick, so he doubled the size of the model.
Look at the photos to see his two enlarged models from my
reproduction drawings. They had their parts printed on 1⁄16 balsa.
One is based on the Jigtime Luscombe and the other is a blowup
of the Carl Goldberg Cessna 180. Both models in the photo are
electric-powered. The motor used in the Luscombe is a geared 6-
volt Speed 400, and the Cessna has a brushless installation. The
Luscombe has a wingspan of 42 inches and the Cessna’s span is
46 inches.
I understand the printer Sam is using is no longer in
production, but I hope that there are others on the market that can
offer the same capabilities. Nice work, Sam.
Jim Walker’s Hornet was great then and now. Awhile back I
shared with you a fanciful project of mine involving the
conversion of a reproduction Jim Walker 404 Interceptor foldingwing
glider to RC. That was a fun project that has provided much
small-field-flying enjoyment.
Frank Macy, the man behind the 404 Interceptor
reproductions, makes another classic American Junior (Jim
Walker) offering of the 1950s: the rubber-powered Free Flight
Hornet.
I can’t tell you how many American Junior (AJ) Hornets my
brother Ralph and I had as kids. Thanks to those great RTF
models, we had the opportunity to experience a model airplane
that flew well. I’m not sure we would have stuck with the hobby
without some of the reinforcement that came with each successful
Hornet flight.
Having such a fond memory of the AJ Hornet, it was only a
matter of time before my reproduction
would receive an electric motor and radio
gear. The pictures tell the story.
My choices of components for
transforming the model into a small-field
RC flyer began with selection of a suitable
microreceiver. I used the RFFS-100 from
Dynamic Web Enterprises. Another good
choice is the JMP receiver (see source
listing). It has the bonus of being narrow
band. Both weigh roughly 2 grams and
include a built-in 1.5-amp speed control.
To operate the rudder and elevator, I
chose Bob Selman standard-size magnetic
actuators. I used a Mabuchi N-20 motor
coupled to a Bob Selman 4.2:1 gear drive.
The gear drive that Bob sells for the N-20
motor is well suited to a project such as the
AJ Hornet conversion. The propeller for
this model is the same 5-inch Gunther unit
that Chris Poole selected for his scaleddown
Uproar.
In its Free Flight configuration—which
includes the rubber motor—the AJ Hornet
weighs 18 grams. The electric-powered
December 2004 75
The AJ Hornet conversion uses a 5-inch Gunther propeller, a Bob
Selman gear drive, and a Mabuchi N-20 motor.
The AJ Hornet conversion is a wonderful small-field flyer that takes advantage of micro
gear such as the RFFS-100 or JMP receiver and magnetic actuators.
Bill Stodgell takes advantage of a backyard swimming pool to
fine-tune a float setup on his Bantam biplane.
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RC version weighs 41 grams. You might
think that the weight gained in the
transformation would have a large
negative impact on flight performance,
but that was not the case. The RC Hornet
is a wonderful small-field flyer.
I elected to use two Li-Poly cells in
series. This gives plenty of power to let
the model punch through wind and do
simple aerobatics. My chosen battery has
a capacity of 190 mAh. This gives flights
in excess of 20 minutes. To use two cells
with the RFFS-100 or JMP receiver, you
need an adapter. These receivers are
designed to operate on one Lithium cell.
Bob Selman sells a two-cell adapter for
each of the microreceivers mentioned.
After flying the RC Hornet, the idea of
using it as an air-tow tug for the 404
Interceptor floated my way. At first I set
the idea aside, thinking there would not be
enough power to tow the Interceptor,
especially because of the increased weight
of the RC configuration.
The more I thought about this idea, the
more I felt compelled to try it. As I write
this, I have started the process of
developing air-tow techniques for the
Interceptor. My first attempts have
demonstrated that the little RC Hornet has
plenty of power for the job. I need to tune
the towing geometry to get a more stable
flight of the Interceptor while being
towed, but this looks as though it will
develop into a great backyard-flying
adventure.
The RC Hornet and similar models are
great for small-field venues such as a big
back yard. That is where I like to fly
mine. It is so nice on a calm evening to
walk out to the backyard and do ROGs
(rise-off-grounds) from the back porch.
Life is good in the small-field-flying
world.
Float-Flying Revisited: Early in the life
of this column I wrote about the subject of
float-flying. Some nice bodies of water
exist that can be used by our small-field
models when they are equipped with
floats. Bill Stodgell of Jefferson City,
Missouri, brought to my attention one
aspect of float-flying using small-field
models that I failed to see.
When we are talking about electricpowered
models, it is possible to test their
water characteristics in a backyard
swimming pool. Even if the model will be
flown off water in an open area, you can
take advantage of a pool to fine-tune your
float setup. One of the photos shows Bill
doing just that with his float-equipped SR
Batteries Bantam biplane.
After reading the March 2004 MA that
included the Electric Flash construction
article, Bill was inspired to adapt the float
design for that model to his Bantam. After
getting the floats built and installed, he
was able to do the fine-tuning in a family
member’s swimming pool. This is a great
idea that takes full advantage of the
smaller size and clean power of the SR
Bantam biplane on floats.
This brings me to the close of this edition
of the column. As always, don’t be
bashful about sharing your latest smallfield-
flyer project. Please send me a
picture or two of your models so we can
all enjoy them. MA
Sources:
AJ Hornet:
Frank Macy
1501 SW Baker St. #53
McMinnville OR 97128
(503) 435-1916
[email protected]
RFFS-100 receiver:
Dynamic Web Enterprises
159 Little Robin Rd.
Amherst NY 14228
(866) Fly-Micro
www.smallrc.com
Magnetic actuators, JMP receiver, N-20
motor/gear drive, two-cell receiver
adapter:
Bob Selman Designs
9054 Gum Rd.
Carthage MO 64836
(417) 358-9521 (after 6 p.m. CST)
www.bsdmicrorc.com
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