Free Flight Indoor - 2004/02

IN A PREVIOUS column I wrote that access to the Santa Ana,
California, hangars had collapsed from lack of maintenance.
Actually, an earlier report stated that disagreements between the
Marines and the city of Santa Ana had resulted in loss of access.
Big Model: Several years ago at one of the hangars on the Santa
Ana Marine Corps Air Field, Hermann Andresen flew a large model,
trying for a 60-minute flight. When I asked him for details on the
aircraft, he gave the following report.
“I had a 60-inch-span, 600-square-inch [EZ60] that was flown in
Santa Ana several times. It was a prototype to check the viability of
turning tight with a large model.
“Erv Rodemsky and Bud Romak had made similar size models
which showed the potential, but these models demonstrated a major
drawback in this approach. The models had such wide turns it was
hard to keep them in the building. Computer studies published in an
NFFS [National Free Flight Society] Symposium report verified that
this was the easiest route to high performance.
“My prototype used differential wing chord [steadily increasing
wing chord, increasing linearly to the left tip] and rudder offset to
obtain more efficient turns. It could be flown easily in a single
basketball court gym, using about half the court width.
“The last time I took it to the hangar, I opened the box to find a
rat had used the materials to build a nest. End of experiment. Then
after timing Steve Brown’s 63:54 flight, I realized it had become
obsolete anyway.
“Some of my studies showed interesting results: A 30-squareinch
model would have to be kept to .001 ounce weight to be
capable of 60-minute flights. A 600-square-inch airplane could have
over seven times that wing loading for similar performance.”
Detroit Balsa Bugs: The Balsa Bugs club has at least two
interesting attributes, one of which is that it was founded before
World War II. It isn’t the oldest US club, but it is well ahead of most
Bud Tenny, Box 830545, Richardson TX 75083
FREE FLIGHT INDOOR
The late Dick Obarski prepares a
Pennyplane for flight. Dave Linstrum photo. The founders of the Detroit Balsa Bugs. (See text.) Photographer unknown.
A low-ceiling steering strategy, drawn by the author.
Fig. 1
February 2004 143
02sig5.QXD 11/25/03 9:54 am Page 143
144 MODEL AVIATION
that were founded before the huge growth of Radio Control
clubs.
The second attribute is faithful attendance. From
inception until fairly recently, including all through World
War II, Balsa Bugs club meetings were held once a week.
Now the club meets once a month, still with no break in
continuity.
Bill Shailor and Rich Doig rode in Paul Shailor’s car
when they were too young to drive. Now only Bill is alive,
but he attends meetings regularly. While browsing through
club archives, Bill found a photo of the founding members
that I’ve included this month. I am privileged to be
acquainted with almost all of them.
From left to right are Dick Kowalski, Phil Klintworth,
Otto Heithecker, Joe Bilgri, Ed Stoll, Ron Plotzke, Bob
Bienenstein, and Bruno Markigewicz. Bill thinks the last
person on the right is Joe Foster. I believe I met Joe once at
either Santa Ana or the Kibbie Dome in Idaho, but I don’t
recognize this face. Who can supply this person’s name?
Steering Sketch: A previous column gave a rundown of
steering and model retrieval—why and when to steer and
how it is done. Fig. 1 shows how a 20-plus-minute flight
was made in a 20-foot flat-ceiling site that had a steady
drift pattern. The site was the gym at the Bedford Boys
Ranch, and Stan Chilton was the flier.
In Fig. 1, the heavy arrow shows the drift direction; it
promised to put the F1D model into the corner or the goal.
Models often survive hitting the wall, but the goal is
another matter. The support structure is a mass of wires and
frame. Models that get caught drop while the propeller is
still turning. The model typically drops with the propeller
on one side of the backboard while the model slides down
until the propeller grabs framework or backboard. The
model becomes firmly locked down.
When this happens, the only way to free the model is to
lift it so that the motor can run down and be removed. Then
you can lift the model by holding the propeller and
pinching the thrust bearing between your thumb and
forefinger.
The sketch shows where the balloon string should
capture the model so that it can be released advantageously.
When to release the model is tricky. If it is released too
soon, it will go into the right-hand corner; if it’s released
too late, the orbit shifts toward the left-hand corner. When
released as shown, a near-perfect orbit results.
Laminated Outlines: Forming rounded tip outlines
Balsa lamination techniques sketched
by Jim Newman. (See text for details.)
How to build cardboard boxes for Free Flight Indoor model storage and
transportation. Tenny sketch.
Fig. 2
Fig. 3
Fig. 4
Fig. 5
02sig5.QXD 11/25/03 9:54 am Page 144
requires careful wood selection, grain
orientation, and a precise pull. If you relax
while wrapping the soaked wood around the
form, it may kink. If you pull too hard on a
thin strip after it has been soaked, it may
pull apart. If a thicker strip is needed for
strength, the basic problems get worse.
The solution has proved to be to
laminate thinner strips using thin glue. For
wet strips, white thinned Elmer’s Glue
works well. To reduce weight, I learned that
the strips can be moistened using thinned
Elmer’s Glue by slowly pulling them
through a small puddle of it. The strips are
softened and bundled in one pass.
The next step is to wrap the preglued
strips around the form. This raises the
problem of dried strips sticking to the forms.
I had tried aluminum foil, furniture polish,
candle wax, and other things, with various
degrees of success. A long time ago, Jim
Newman (of the Indiana area) suggested a
better way.
He has been using Teflon pipe thread
tape, available from plumbing stores.
Plumbers wrap a thin layer of tape around
the threads of metal pipe to form a seal for
the joint. The joint can be sealed and later
opened without having to use excessive
force.
Jim suggests that balsa strips can be
softened by spraying them with waterthinned
Elmer’s Glue or Windex before
wrapping them on the form. He showed the
process using three sketches. Fig. 2 and Fig.
3 show how wingtips (Fig. 2) and fuselage
formers for rubber-powered Scale models
(Fig. 3) can be built. In Fig. 3, the ends of
the strips should be tapered for a better joint
where the wood joins.
Tom’s third sketch (Fig. 4) shows how
he forms more than one tip at a time. For
lightweight models I form one tip at a time;
if opposite wing and stabilizer tips turn out
different, the model doesn’t know the
difference!
Model Boxes: Lightweight models (Indoor
Sticks, Intermediate Sticks, Pennyplanes,
and even P-24s) should be transported and
stored in closed boxes to keep them safe and
free from dust accumulation. Fig. 5 shows
how to build lightweight boxes to
accomplish this.
Begin with large sheets of corrugated
cardboard, usually available from large
office-supply stores. Work carefully,
making accurate measurements and precise
cuts that result in square edges on each cut.
Where two cuts come together, don’t try to
cut right up to the lines. Cut moving away
from the intersection, and then cut right up
to the line while holding the cutting edge
vertical. When the second cut is made, the
notch is clean without weakening the
cardboard on either side of the cuts.
Refer to Fig. 5 for the following. For
smaller boxes that can be made from boxes
from grocery stores and large appliances,
there is no machine-cut edge. Cut the box
into separate flat panels by cutting along
each fold. Not counting the bottom panels
February 2004 145
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02sig5.QXD 11/25/03 9:54 am Page 145
Bedford Boys Ranch gym several years ago
created some unusual events for variety,
including No-Cal Wakefield (profile). The
rules are as follows.
1) Models must be of Wakefield designs
flown from 1927 through 1956. Proof will
be required (three-views, plans, articles, or
photos).
2) Maximum wingspan is 16 inches.
Average chord may be enlarged to 2.5
inches. Planforms should closely resemble
original designs. Cover surfaces’ top sides
only.
3) The tailplane may be enlarged to 1⁄3 of
the wing area.
4) The fuselage may be altered
reasonably to accept enlarged chords. Cover
left side only.
5) Landing gear may be altered,
shortened, but propeller must clear on
takeoff, bracing eliminated, wire instead of
wood, and folding gear permitted if used on
original.
6) Fin may be divided for trim
adjustment, covered on left side only unless
original was wood sheet, then sheet is okay.
7) Propeller must be 6.5 inches
maximum, wood, foam, or modified
lightened plastic.
8) Minimum weight is 6 grams,
excluding rubber.
9) Covering is to be Japanese tissue or
equivalent; color schemes of original are
encouraged.
10) Must rise-off-ground unassisted,
using both hands per Wakefield rule.
11) Three official flights, two 20 seconds
maximum, attempts for each flight. Times to
be in even seconds. The highest average of
the three flights wins. There will be oneflight
tie flyoffs.
12) An official flight is an unassisted
takeoff timed from point of release to
touchdown, of 20 seconds or more. A 10-
second hang-up rule is used.
13) Proxy flying is permitted. MA
(these are usually scuffed by handling,
storage, and shipping), you will have four
side panels and four flaps, some of which
will be too small to be useful.
Most of the panels will not have a clean
machine-cut edge, so use a straightedge to
draw lines as close to the edge as possible.
One of the longer lines can be the base (line
A-C) of the triangle shown in Fig. 5.
This gives the largest precision panel that
can be cut from the box. From whatever
cardboard you have, the width of flaps that
become box sides and ends must be equal.
Whatever cardboard is not used for flaps is
the largest bottom the box can have.
Cuts made as shown form flaps that go
inside the box bottom and outside a slightly
larger lid that closes the box to form a
container that is similar to a shoe box. After
you have one or more boxes, anchor
whatever models will fit so that not even
dropping the box will dislodge the model(s),
and you are finished.
Basic Winding: I consider a torquemeter
imperative when using Tan II rubber. For
less-than-full-power applications, Tan II is
like Pirelli after you learn to make the
appropriate adjustments in cross-section and
length. The following covers taking any
rubber absolutely “all the way”; you don’t
necessarily have to push rubber quite that
hard in most cases.
1) Begin a windup with no more than
four times stretch, and wind slowly as you
watch the torquemeter.
2) The torque will rise steadily for a
while, more slowly for approximately the
same number of turns, then ever more
rapidly.
3) When the torque rise speeds up, wind
for short periods of time and then
momentarily reduce the stretch. If the
indicated torque drops lower as the stretch
reduces and remains there as you come to
the original stretch, you are approaching
maximum stress for that amount of stretch.
4) When the torque rises as you come
back to the original stretch, reduce stretch
by roughly 15% and resume winding
slowly.
5) Repeat the unstretch/stretch maneuver
until you reach maximum stress for the
distance between hooks on the model.
6) Hold the turns with the motor at
model hook length, and massage all of the
large knots until they rearrange into smaller
knots.
7) If the torque drops while you are
manipulating the knots, add turns to restore
the torque level. Winding is complete at
max stress when further manipulation does
not reduce the torque. If this torque level
won’t cause the model to outclimb the
ceiling, hook up and launch.
8) If the torque is too high for the ceiling,
slowly reduce turns until the torque is at the
right level. Tan II rubber has a steep curve
in the last few turns, so it is almost
impossible to transfer full torque to the
model, even if you need it.
Beware! It has been my experience that
you cannot rush the last 20% of turns. Any
rubber must be scrupulously clean for
“blast” winding, especially for Tan because
the surface is so smooth. There must be
sufficient lube on the rubber to prevent
scuffing! The motor must not have any nicks
or other mechanical damage; otherwise,
stress can concentrate at the damage site and
cause it to break. Try it if you must since
you can get by with it sometimes.
The group of modelers who flew at the
146 MODEL AVIATION
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