SCIENCE CONCEPT:
- There is some debate about where kites originated.
Some say China and some say, no, it originated in the South Pacific with
the islanders there. The Balinese have their own story which explains
the origin of kites. Nevertheless we are left with a heritage of
wonderful stories, designs and techniques for flying kites.
STUDENT OBJECTIVE:
- The student will design, build, and fly a kite. They
will observe how a kite 'catches' the wind and how different types of
kites respond to the airflow of the wind.
OVERVIEW:
- In this activity, the student will be making a kite. The kite
design and materials will be up to the students, their ability level, and
the teacher's prerogative. Included in the Teacher's Text will be a
basic list of ideas in making different types of kites. After the
students complete the kite they will go outside and fly their kites to
experience the wind lifting their kite and keeping their kite in the air.
Encourage your class to make different types and shapes of kites so that
as a class you can experience the various aerodynamic forces that impact
a kite when it is flown. Happy flying!
TEACHER TEXT:
- Kites are used as a fishing aid in the Solomon Islands. Kites
are used by the Koreans to announce the birth of a child. Kites were
used by the Chinese during battles. They were made of bamboo and had the
tendency to hum and shriek in the wind which frightened the enemy. Kites
in the Chinese and Japanese cultures were capable of holding or "flying"
a person in the air where the person could spy or act as a sniper using
bows and arrows. Many kite designs that were developed for the military
or for scientific purposes can be seen at kite festivals and competitions
today. Windsocks are a Japanese tradition that has caught on elsewhere.
In the Japanese culture the windsocks are made in the shape of a fish
called a carp and they are the symbol of strength and strong will,
overcoming great obstacles to achieve their goal. Like the Chinese, the
Japanese have a special day for flying kites or windsocks. In Japan it
is May 5th, "Children's Day." Today, we don't need a special day to fly
kites and there are many kite-flying festivals throughout the year. We
can enjoy the magic of kites any time!
How do kites fly? Let's explore the aerodynamics of kites.
Kites are heavier-than-air devices. They weigh more than the volume of
the air they displace. They are flown at the end of a string, line or
rope. Kites are aerodynes. In other words, they overcome the force of
gravity and are kept in the air by the force of the wind or the forces of
wind pressure on the kite. The aerodynamic force involved is called
lift. Lift on a kite is perpendicular to the relative wind direction.
What is relative wind? It is the actual wind, the actual direction of
wind and speed of the wind. The kite reacts to the wind pushing on it.
Lift is executed in an upward direction thereby opposing the pull of
gravity on the kite.
Newton's Third Law (for every action, there is an equal and
opposite reaction) helps explain the
aerodynamics of kite
flight. Think of the kite
as flying on an inclined plane and flying in one spot. The kite exerts a
downward force upon the air. The air passes over the top edge of the
kite and goes down the upper surface of the kite. Remember that air is
relatively heavy. As the kite pushes downward, it gets an equal push
upward by the air. As this happens, the kite gets an upward counter
force and it flies! Newton's Law states that for every action there is
an equal and opposite reaction.
For a kite to fly, the air lift potential must be greater than
the weight of the kite. For example, if the downward and upward force of
the air is equal to the weight of the kite, the sum of all the forces
will be zero and the kite will be in a state of equilibrium. It will not
fly up or down. If the downward force upon the air is greater than the
weight of the kite the upward force will also be greater and the kite
will move upward and climb higher. If the downward force is less than
the weight of the kite, the upward force will be less and the kite will
sink sometimes very quickly, crashing to the ground. Knowing these basic
principles can hep us learn how to fly a kite and how to design a kite.
Also, knowing the strength of the wind and wind direction are useful in
developing a knowledge of the basic moves and tricks in kite flying.
The tail of a kite adds to its stability and balance. It also
acts as a drag and for some kites will put a limit on the maximum
altitude that can be reached by a particular kite. In designing kites
one must consider the pros and cons to each element of design. For
example, one can eliminate the tail, but bow out the design for stability
and thus achieve greater altitude. Other ways to achieve stability may
be in the cover material, the sticks or frames, addition of wings or
keels or using shaped wing surfaces. Rudders, airfoil-shaped surfaces
and tapering are some other design possibilities.
- How do you construct a kite?
- 1. Decide on a shape or form. Kites come in various shapes and forms.
The variations are endless but the basic forms are: flat or bowed, box
or cellular and semirigid or nonrigid.
- 2. Design the sticks and frames for the kite. Make sure it will be a
strong frame but also be light weight.
- 3. Choose the cover material. Strong but light.
- 4. Choose how you will stabilize your kite. Will you have a tail? Will
you use a drogue or wind cup which catches the air and acts as an anchor.
It stabilizes the kite.
- 5. Will you bow your kite. Bowing can be one of several things. It can
be a smooth curve or an angle at the center of the kite. It can also be
angles somewhere else on the kite. The bowing can be subtle or
exaggerated. The bowing tends to stabilize the kite.
- 6. Will you vent your kite. Venting is deliberate openings in the
covering material of the kite. Venting allows some air to go through the
kite and can add stability to some kites.
When you get ready to launch your kite, make sure you are in an
area that is open and free from trees, electrical and telephone lines,
buildings, and automobile traffic. Stand with your back to the wind.
Hold the kite with one hand and the reel of string with the other. Let
the wind lift the kite and as it does, feed out the line to the height
you wish. Walk in the direction of the wind as you feed out the line.
If the kite won't climb you can reduce the bridle angle. To land the
kite, walk toward it winding the line on the reel as you walk.
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PREPARATION TIME:
- 15 - 20 minutes.
LESSON TIME:
- 60 - 80 minutes.
TEACHER PREP:
- Gather a variety of kites to show the children for
ideas in making their own kites.
WORDS TO KNOW:
- balance
- stability
- drag
- bow out
- air lift
- aerodynes
- relative wind
- heavier-than-air devices
- Newton's law of action & reaction
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