Model Aviation

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Model Aviation
Educational activity for young people.
Presentation Placed in Public Domain by Bill Kuhl
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Introduction
Model aviation has been both an enjoyable and
educational activity for much of my life. Two
ways it has helped me is demonstrating my
thinking was incorrect or inaccurate, and
learning the process of refinement. Often I
thought small changes in trim, propellers, or
rubber motors would not make much of a difference
but I was proven wrong. In the process of being
proven incorrect I have learned to test
individual aspects, record important data, and do
the process again after making new changes. It
is my hope that this presentation can be used to
promote the virtues of model aviation as a fun
and educational activity for young people. Feel
free to copy this presentation, I only asked that
it is not sold for profit. Bill Kuhl
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History
Modern copy of Penauds Planophore
Flew 131 feet in1871.
First Rubber-powered Model Airplane
The first rubber-powered model plane can be
credited to the French aviation enthusiast,
Alphonse Penaud. Initially he experimented with
rubber-powered model helicopters but later
turned to building model planes powered by
rubber. The Wright brothers were first exposed
to flight by the toy helicopter their father
gave them based on the helicopter developed by
Penaud.
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History
The First Aeromodeling Clubs The first model
airplane clubs started in the New York City area
as early as 1907. Balsa wood was not used in
model planes until around 1911, so models were
constructed of materials such as bamboo, pine,
and spruce. Most models were twin pushers, two
motor sticks with a prop in the rear of each,
coming together in front. Viewed from the top it
looked like a capital letter A. The propellers
turned in opposing directions to cancel the
effects of torque.
Twin-pusher
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History
City Sponsored Model Airplane Clubs In the
1930s, even city government promoted model
aviationby sponsoring contest and clubs. Detroit
Department of Recreation sponsored twenty-two
clubs, and even sold modeling supplies. School
gyms were open one night a weekfor indoor flying.
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History
Spirit of St. Louis
The Influence of Charles Lindbergh on
Aeromodeling Charles Lindberghs historic flight
from New York to Paris in 1927 was the driving
force to skyrocket the popularity of
aeromodeling. Before Lindberghs flight only
around a dozen model airplane kit manufacturers
existed and within a year of the flight there
were over two thousand.
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History
Science Olympiad
Today, the largest number of young people are
exposed tofree flight model airplanes by an
event that is part of a competitionheld in many
middle and high schools known as Science
Olympiad. The model airplane event is now known
as,The Wright Stuff. Planes must be built
according to specifications that limit the size
and minimum weight of theairplane. Competitions
are held at regional and national levels,with
the top times equaling what a very skillful
indoor modeler might accomplish.
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Safety
Safety is of primary importance for any activity
for young people. Small rubber powered planes
that weigh less than an ounce are relatively safe
if used with common sense.

• Relatively safe hobby because the models are
  light and fly slow.
• Biggest danger is when children do not use good
  judgment in retrieving a model that is caught in
  a tree, power line, or on top of a building.
• Students need to be taught safe techniques for
  working with razor blades. Another option is to
  pre-cut all pieces.

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Building
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What are the models made of?
Balsa Wood The most popular material for building
rubber powered model airplanes is balsa wood.
It is a very fast- growing tree which reaches a
height of 15 feet in the first year, and 60 to 90
feet during the next six to ten years. Most balsa
comes from balsa plantations in Ecuador owned and
operated by the Baltek Corporation of Northvale,
NJ. Although balsa may appear rather fragile, it
is fairly strong for its weight. The weight of
balsa can vary considerably, for small models the
best performance can be obtained by selecting
lighter balsa.
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What are the models made of?
Covering Some models are constructed entirely of
balsa wood, but more often a balsa structure is
covered with a paper, tissue, or plastic. The
covering not only covers the structure for
flight, but also adds to the strength of the
structure. Some models use onion skin paper as
plan and covering material. This is a strong
material but is also rather heavy and can warp
the structure as the humidity changes.
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Building Questions
How long does it take to build a model airplane?
This can vary a lot but the simplest planes such
as the AMA Cub or Delta Dart can be completed in
about an hour. Planes with ribs in wing and tail
could take considerably longer. Can you repair
the plane if it breaks? Unless a really large
truck runs over your plane, any breaks to the
balsa wood should be easily glued. A bigger
problem is when the plane becomes severally
warped, if the warp is bad enough, better to
build a new plane.
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What Tools Materials are Needed
The Essentials - razor blade or modeling knife,
pins, and glue.
Building Surface that pins can be pushedinto
ceiling tile sections or cardboard. Normally
plans are covered with wax paper, but some planes
use the plan as the covering material. Helpful to
have a sanding block. Gluestick is used to attach
covering material to balsa framework.
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What Tools Materials are Needed
Winders Essential to get flying times of more
than a few seconds, is a mechanical winder. The
rubber motor is stretched and lubricated, and
turns are wound in as the winder is brought
closer to the other end of the rubber loop.
Common ratios for winders are 151 and 51.
51 Winder 151 Winder
Armorall can be used as a lubricant
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Flying
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Free Flight
The cost of simple rubber-powered airplanes is
low, but that is not why they are known as free
flight, it is because they do not have any
external control. The flight path is controlled
by the trim adjustments in the model, the
stability built into the model, and how the wind
blows.
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Where can these models be flown?
Flying indoors in a gym is a year-round activity.
Models can be flown outdoors when the breeze is
very light.
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Indoor Flying Gallery
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Outdoor Flying Gallery
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Educational Aspects
I owe as much, if not more, to my uncle who
introduced me to model airplanes when I was a kid
30 years ago than I do to any of my university
professors in helping me to become the
knowledgeable structural engineer that I am
today. Thanks Uncle Tom. Cliff I know what you
mean Cliff. I had an uncle who gave me a model
airplane kit at Christmas time when I was maybe 9
years old. I thought it was a very big deal. This
same uncle later gave me his old Boy Scout
Manual. That uncle probably had a bigger
influence on my life and the way I turned out
than anyone else, even my parents. Ed
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Educational Aspects
Accuracy Building and adjusting the model
accurately can make a huge difference in the
performance. As you build additional models, you
will want to improve the accuracy of your work
for aesthetic reasons. Hopefully this desire to
do more accurate work will transfer into all
areas of your life.
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Educational Aspects
Creativity Designing and building your model
airplane is rather easy to do. With some
understanding of aerodynamics and using rule of
thumb proportions, anyone can design a
successful model. There are many more unusual
types of aircraft that can provide additional
challenges such as flying wings or canards
(tail first).
Flying Wing aircraft in flight indoors.
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Educational Aspects
Test Theories Even the simplest model plane,
flies according to the principles of aerodynamics
and physics. Often the common sense ideas we
have on the factors that affect flight
performance are proven inaccurate. Small changes
can make a huge difference hopefully model
aviation will open your mind to new ways of
thinking.
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Educational Aspects
Mathematics - Example calculation of winder
turns. Maximum turns per inch for 3/32" rubber is
129, for our rubber motor 10" long, maximum turns
would be 1290. For sport flying 80 would result
in 1032 turns. 129 x 10 1290 1290 x .8 1032
Once we know the total turns, it is easy to
calculate the total cranks of the winder needed.
Simply divide the total turns by the ratio of the
winder. For example using the 51 1032 / 5
206.4, truncating to a whole number would be 206
winder turns.
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Educational Aspects
Physics How Does the Rubber Motor Work (in terms
of energy transfer)? When you crank the winder,
mechanical energy is converted to potential
energy stored in the rubber. To be more precise,
this is elastic potential energy. Harcourts
Dictionary defines elastic potential energy as
"the energy made available for use by the return
of an elastic body to its original
configuration." Potential energy of the wound
rubber is converted to kinetic energy of the
spinning propeller. Harcourts Dictionary defines
kinetic energy as "the energy inherent in the
motion of a body"
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The End
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