Transcript Model Aviation - HBC - HBC Hiawatha Broadband

Model Aviation
Educational activity for young people.
Presentation Placed in Public Domain by Bill Kuhl
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
History
Modern
copy of
Penaud’s
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.
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
History
City Sponsored Model Airplane Clubs
In the 1930’s, even city government promoted model aviation
by sponsoring contest and clubs. Detroit Department of
Recreation sponsored twenty-two clubs, and even sold
modeling supplies. School gyms were open one night a week
for indoor flying.
History
Spirit of St. Louis
The Influence of Charles Lindbergh on Aeromodeling
Charles Lindbergh’s historic flight from New York to Paris in
1927 was the driving force to skyrocket the popularity of
aeromodeling. Before Lindbergh’s flight only around a dozen
model airplane kit manufacturers existed and within a year of
the flight there were over two thousand.
History
Science Olympiad
Today, the largest number of young people are exposed to
free flight model airplanes by an event that is part of a competition
held 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 the
airplane. Competitions are held at regional and national levels,
with the top times equaling what a very skillful indoor modeler
might accomplish.
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.
Building
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.
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.
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.
What Tools & Materials are Needed
The Essentials - razor blade or modeling knife, pins, and
glue.
Building Surface that pins can be pushed
into 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.
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; 15:1 and 5:1.
5:1 Winder
15:1 Winder
Armorall can be
used as a lubricant
Flying
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.
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.
Indoor Flying Gallery
Outdoor Flying Gallery
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
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.
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.
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.
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 5:1: 1032 / 5 = 206.4, truncating to a
whole number would be 206 winder turns.
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"
The End
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