ARE YOU READING this column out of
simple curiosity? Maybe you are reading out
of morbid curiosity. Are you interested in
trying rubber-powered models? Maybe you
are an avid Radio Control flier who would
like to try your hand at a stick-and-tissue
model. Maybe you built a stick model as a
kid and want to try it again. Perhaps you are
a teenager who built a Science Olympiad
model and want to build a larger rubberpowered
model. This column may help, but
you will probably want more information
than I can provide here.
My interest in rubber-powered models
was rekindled approximately 12 years ago.
At that time I was not aware of anyone in
my area who was building rubber-powered
models. I started looking through my
collection of old model magazines, some of
which dated back to the mid-1950s. There
were many helpful articles which I either
referenced or copied and placed in a looseleaf
binder.
If you do not have such a mother lode of
information or, better yet, a personal tutor,
consider purchasing Don Ross’s Rubber
Powered Model Airplanes, published in
1988. It is a great book, loaded with useful
tips and plans for three simple models.
There is a great chapter on balsa-wood
selection as well as information about
rubber motors and propellers.
The book is available from a number of
sources including Hannan’s Runway. Send
$1 for a catalog to Box 210, Magalia CA
95954. Place your order by telephone at
(530) 873-6421, and the catalog is included.
Or use the Internet at www.hrunway.com.
This past fall I “bit the bullet” and put a
Black Bullet on the building board. The
model is kitted in three sizes; I selected the
Gene Smith, 1401 N. Husband St., Stillwater OK 74075; E-mail: [email protected]
FREE FLIGHT SPORT
The author admits that he should have been mowing his lawn
instead of taking this picture of his framed-up Black Bullet.
The stabilizer mount has been modified for a dethermalizer—a
necessary item if you want the model to stay around.
Halloween was nearing when the Black Bullet was finished, so
the fuselage is black and the horizontal surfaces are orange.
The Black Bullet’s stabilizer tip has been cut oversize to ease
cutting from the sheet wood and to prevent splitting.
138 MODEL AVIATION
04sig5.QXD 1.23.03 3:20 pm Page 138
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30-inch-span version as a good compromise
between performance and ease of storage. It
fits right into my P-30 box. Be the first kid
on your block to have a low-wing cabin
endurance model.
If you don’t already have an FAI Model
Supply catalog, get one and order your own
Black Bullet kit! Go to
www.faimodelsupply.com.
You don’t see many low-wing Duration
models. High-wing, old-time, cabin Rubber
models are popular. As a rule, they are easy
to build and are good fliers. All cabin
models seem to be popped from the same,
or at least a similar, mold. For years I
looked at the advertisements for the Black
Bullet. It had to be the neatest-looking cabin
endurance model I had seen. Not only is the
low wing unique, but the cabin has a sleek,
streamlined design.
A quick look at the plans showed a
relatively short, narrow fuselage, a big fin
and stabilizer, and plenty of dihedral. The
plans appeared to be computer-generated
and were clean and clear. The balsa in the
kit was heavy. I am sure I could have used
the kit wood, but since the model might be
flown in competition I elected to make a
copy of the parts and transfer the pattern to
lighter balsa.
There are a number of good ways to
transfer parts patterns to balsa. I have tried
most of them, but I have settled on using a
glue stick. Make a copy of the printwood
and glue it to your balsa sheet. Apply the
glue to the paper only. If you apply the glue
to the paper and the balsa, the adhesion is
semipermanent. If worse comes to worse,
the bond can be released with rubbing
alcohol.
When framing a fuselage that has curved
longerons, I like to soak the strip wood in
water overnight. Soaking long strips was a
problem until I read the following tip. Go to
a tropical-fish store and buy one of the clear
plastic tubes used for aerators. I use a 3⁄4-
inch-diameter tube. Put a cork in one end,
and secure it with silicone adhesive. To
soak your balsa strips, drop them into the
Larry Kruse’s P-30 GeezerPleezer. It uses GizmoGeezer front end
assembly, Benedek 6356b airfoil, and rolled tube fuselage.
Initial tests used a pop-up wing and stabilizer, but that proved to
be a bit on the wild side. It’s a great flier.
tube and fill it with water, corking the open
end.
When framing the fuselage, wipe the
longeron to remove surface water, glue the
longeron in place, and allow it to dry
overnight. That should minimize any
remaining tension from the bent wood.
The Black Bullet has an interesting
solution for mounting the removable wing.
The fuselage section above the wing is
framed for a loose fit so the wing can be
removed. Small hooks on top of the wing
are used to rubber-band the wing in place.
The curved portions of the wingtips and
tail feathers are built up from sheet-wood
parts. This is not one of my favorite
building techniques, but the parts did fit
well. As recently mentioned on the
Smallnet Forum, it helps to cut the tip
pieces slightly oversize. Once you have
fitted and glued the joints, sand the tip to
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final shape. It does make things go better,
particularly for models where the printed
parts don’t exactly match the plans. It also
04sig5.QXD 1.23.03 3:20 pm Page 139
140 MODEL AVIATION
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helps prevent the narrow cross-grain
portions of the tip pieces from splitting.
An inch of the rear turtledeck was
sheeted to provide a slot for fin alignment.
The gusset in the front of the fin was
enlarged so a hole could be made for the
rubber band to raise the stabilizer/fin. A
gusset was placed just in front of and below
the leading edge of the stabilizer for
placement of a small dowel to hold the
dethermalizer (DT) rubber band. Fourpound-
test monofilament attached to the
bottom of the fin runs through a small “U”
of .015-inch music wire at the rear of the
fuselage, then forward to a Silly Putty DT
actuator.
In two months I’ll write about
adventures in trimming the Black Bullet.
(Hint: the Black Bullet has so much dihedral
it can be trimmed like a high-wing model.)
I Like to Put It up in Braids: To get the best
performance from your rubber motor, its
length will typically be one and a half to
three times the distance from the motor
hook to the rear peg. Unless the motor is
braided, it will have a tendency to bunch
up in the rear of the model. The model
may have been balanced perfectly upon
launch, only to become tail-heavy as the
motor unwinds and bunches near the rear
peg.
This is where braiding becomes
helpful. Braiding prevents the motor from
developing slack, bunching, and altering
the center of gravity (CG) as it unwinds.
To learn the technique for braiding, read
Don Ross’s book, check your Internet
search engine for “braiding rubber
motors,” or go to Al Lidberg’s Web site:
www.aalmps.com. He has a tips section
which includes information about braiding
techniques.
Most freewheeling propellers depend
on slack in the rubber motor to allow them
to freewheel. If you braid the motor, you
may not have enough slack left for the
propeller to freewheel. You can avoid that
problem by silver-soldering a small washer
in front of the nose bearing. The motor
pulls against the washer, allowing the
propeller to freewheel.
If you use a ramp freewheeler, pull the
propeller forward to engage the ramp. It
will stay engaged until the torque is
gone—unless it hits the ground before the
motor unwinds. If that happens, the
propeller will probably release prematurely
and the motor will rapidly unwind, making
a sound like two small animals are having
a knock-down, drag-out fight inside your
model. A latch freewheeler also works
well with the small washer soldered in
front of the nose bearing.
How about those first test glides of
your new rubber-powered model with a
freewheeler? Of course you performed a
preflight on the model. You found no
unintentional warps. Any warps you saw
were put there on purpose. You put
washout on that low-winger or a touch of
washin for the right panel of that highwing
cabin model you plan to fly to the
right. You have balanced the model at the
point shown on the plans with the rubber
motor in place and wound the motor tightly
enough to remove slack.
At this point some like to pin the
propeller level and try their test glides.
However, the stationary propeller will tend
to roll the model to the right. To avoid this,
other modelers like to remove the propeller
and motor, and ballast the model to the CG
for test glides. I don’t like to go to that
trouble.
My favorite technique is to put 100
winds in the braided motor and let it
unwind fully. This ensures that the motor
has no slack. Then I put in approximately
20 hand winds and try a test glide. This
simulates that portion of the flight where
the model is transitioning from powered
flight into the glide.
If the model stalls, I lower the trailing
edge of the stabilizer. If it dives or just
doesn’t seem to want to “float,” I raise the
trailing edge of the stabilizer. I do not like
to bend the elevators up or down; I prefer
to shim the entire stabilizer and elevator as
a unit. The model should glide in a
reasonably straight line. If your model
makes a sharp turn in either direction, you
missed a warp or have too little fin area.
Now you are ready to pack in a few more
turns.
GeezerPleezer Takes to the Air: Inspired
by the GizmoGeezer Adjustable
Freewheeler Front End, Larry Kruse has
designed and built a P-30 expressly for the
GizmoGeezer. Larry has designed many
Free Flight endurance and Scale models,
but he feels that this is one of his best. I
witnessed the test flights and can truthfully
say that this model wants to fly. Larry has
entered two contests since finishing the
Pleezer and won both of them with maxes
all the way.
Those of you who fly P-30 know that a
stabilizer DT is not always enough to bring
a P-30 down when it is in a strong thermal.
Larry rigged the Pleezer with a pop-up
wing and pop-up stabilizer. Both surfaces
pivot at the leading edge. When both popups
were activated, the DT action was too
wild. Now Larry uses one or the other; the
wing pop-up when thermals are around or
the stabilizer pop-up in light lift.
If you haven’t seen the GeezerPleezer
Freewheeler Front End, check it out at
www.gizmogeezer.com/index.htm.
A Paid Advertisement: As I edited this
column, it seemed to read much like a
paid advertisement. Most of our supplies
for rubber-powered models are only
available by mail order; if you are
fortunate enough to have a nearby hobby
shop that still caters to this facet of the
hobby, by all means take advantage of
that convenience. MA
04sig5.QXD 1.23.03 3:21 pm Page 140
