Taketonbo Science
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An
airplane wing, called an airfoil has a very distinctive
cross-section shape.
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When air moves
across this airfoil shape, there are changes in air pressure.
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The changes in
air pressure create forces that cause the airfoil
to fly.
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Taketonbos
fly for the same reason airplanes fly - differences in air pressure
caused by an airfoil.
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Real
dragonflies use the same aerodynamic principles to fly.
About
Airfoils --
First, airfoils have
a very distinctive shape when looked at in cross-section. They are usually flat
on the bottom and they curve in the front and the top. They usually come to
a rather sharp point at the back. They definitely have a front and a back. In
order to work correctly, airfoils must move forward through air. The force that
provides forward movement is often called thrust.
Front
Back
Second, even though
some airfoils are hollow, they all act as if they are solid. Airfoils split
the air as they move. Airfoils are designed in such a way that when the air
splits, the air going over the top side has to travel farther than the air going
over the bottom side. Since the top side is more curved than the bottom side,
the air must travel farther as it goes along the top curve than it does as it
goes along the straight bottom.
Air going over the top goes farther
Third, because the
air is made up of many millions of molecules, they tend to hold each other in
place. As the airfoil moves through the air, the molecules split apart, move
along the surface of the airfoil, then come back together very close to the
same place they were before they split. This means that in order for the molecules
that split apart to get to the same place at the same time the ones traveling
farther (the ones on top) must also travel faster.
The light blue molecules on top have to move faster.
High
and Low Air Pressure--
There are two kinds
of fluids; one kind is called gas the other kind is called liquid. There are
specific scientific laws that tell us how fluids work. Airfoils follow the rules
that apply to gases. The most important rule that applies to an airfoil is Bernoulli's
Principle.
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Bernoulli's Principle
states that faster moving gases have lower pressure than slower moving
gases.
A
Guy Named Daniel Bernoulli (1700-1782) --
Daniel
Bernoulli was a Swiss mathemetician and physicist. His father was Johann
Bernoulli (1667-1748) and he had an uncle named Jakob Bernoulli (1654-1705)
who were also methemeticians. They were the ones who together with Sir Issac
Newton and Gottfried Leibniz figured out the branch of mathematics called
calculus. In the year 1738 Daniel Bernoulli noticed an interesting phenomenon
(an extraordinary and/or remarkable event). When a fluid moves faster its
pressure drops. Bernoulli wasn't sure how this discovery would apply to
many things at the time, but he experimented with it anyway. After his experiments
he was reasonably sure that fluids behave this way all the time. Now this
didn't seem like such a big deal at the time. But Bernoulli's Principle
has a HUGE effect in our modern world.
This entry contributed
by Dana Romero. Portions of this entry contributed by Leonardo Motta
If you really want
to get carried away, check out the math on this page.
Forces that
create flight
As a result of Bernoulli's Principle
acting on airfoils as they move through the air, unbalanced situations exist.
The force (air pressure) pushing down on airfoils (F2) is less than the force
(air pressure) pushing up on them (F1).
We can draw the forces
as arrows called vectors. They have a starting point, a direction, and a measurement.
Vectors can be added and subtracted almost like regular numbers. If we draw
a picture of the vectors as they look when we add them together we get the following
image:
When we use vectors,
we usually use positive and negative symbols to tell us the direction of the
force. In this case we will use positive (+) for upward force and negative (-)
for downward force. The F1 blue arrow which is positive (+) is bigger than the
F2 orange arrow which is negative (-). When we add them together, we get a smaller
positive (+) force, Fn, which is shown as a red arrow. This is called the net
force since it is the only force left that works on the airfoil after we have
added all the component forces together. We use the term lift to identify this
force.
An airfoil works because
a condition of unbalanced forces is created as it is used.
Taketonbo
Flight --
In order to understand
how taketonbos fly, we must understand the four forces of flight.
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Lift is an upward
force created by the airfoil. The force is about 90º to the direction of
the apperant wind. As long as Lift is equal to Weight the aircraft flies
level. If Lift is greater than Weight the aircraft goes up. If Lift is less
than Weight the aircraft goes down.
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Weight is the force
caused by gravityacting on the mass of the aircraft. It is directed toward
the center of the earth from the center of balance of the aircraft. Weight
has to be less than Lift for an aircraft to climb, and equal to Lift for
an aircraft to fly level.
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Drag is a force
parallel to the apperant wind. Drag tries to slow the aircraft down. It
is caused by the billions of air molecules rubbing on the side of the aircraft
as it forces them out of the way to pass through.
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Thrust is the force
that keeps the aircraft moving. Thrust is either a push or pull produced
by the aircraft engines. Thrust is directed opposite Drag.
If you want to very
deep get into this information check out John S. Denker "See How It Flies"
Like a real helecopter,
the wing of a taketonbo is also its propeller
The procedural component
of this activity is not to follow a step-by-step approach, but rather to utilize
previous knowledge and laboratory experiences to design a technique for experimentation
with the Bamboo Dragonfly. There are two fundamental types of Bamboo Flyers.
One is based on simply placing the propeller shaft in the palms of your hands
and quickly creating the appropriate torque to generate a large enough angular
velocity to create an unbalanced condition of pressures above and below the
propeller blades to create lift. The second is a smaller bamboo shaft with propeller
placed inside a larger diameter hollowed bamboo shaft. A string is wrapped around
the propellered shaft that can then pulled with a Force (F) that should be measurable.
The second form of the Bamboo Dragonfly is similar in many ways to the condition
of rotation that is exemplified by the rotational motion of the bicycle wheel
around a vertical axis. We should be able to: 1.Draw a free body diagram showing
the forces acting on the smaller bamboo shaft with mass, m, in terms of m, a
and FT. 2.If the magnitude of the linear acceleration of the mass, m, is measured
to be a, what is the equation that should be used the calculate the tension,
FT, in the string (i.e. what equations relates m, FT and a)? Note: In a system
where FT - mag = ma, if ag<
Real
Helicopters --
Glenn
S. Bloom former Army helicopter pilot
7 section site on how
helicopters work
Section
1 Rotary Wing Terminology - http://www.geocities.com/CapeCanaveral/Hangar/1425/section1.html
Section
2 Dis-Symmetry Of Lift - http://www.geocities.com/CapeCanaveral/Hangar/1425/section2.html
Section
3 The Forces At Work - http://www.geocities.com/CapeCanaveral/Hangar/1425/section3.html
Section
5 Unique To Helicopters - http://www.geocities.com/CapeCanaveral/Hangar/1425/section5.html
Section
6 The AHIP Program - http://www.geocities.com/CapeCanaveral/Hangar/1425/section6.html
Section
7 Aircraft Specifications - http://www.geocities.com/CapeCanaveral/Hangar/1425/section7.html
Real
Dragonflies --
http://www.ups.edu/biology/museum/museum.html
http://www.ups.edu/biology/museum/UPSdragonflies.html
http://members.bellatlantic.net/~dbarber/odonatology.html
http://stephenville.tamu.edu/~fmitchel/dragonfly/index.html
This site is still 
John D. Hickey
