Virtual Skies

1. Before starting, write what you think you already know about each of the following topics.
2. Then conduct the web quest and add to / change your initial ideas as you go.
3. Tip #1: Write in your own words or put quotations around direct quotes. You may want to use some of these ideas later, so you need to know which are your words and which are not.
4. Tip #2: Use the FIND function in your network browser to find keywords on any page. This will speed up your scanning for information!
5. Tip #3: Don't spend too much time on one question Ð if you can't find the answer, move on- you may find it later!

1. Aerodynamics: In what direction do lift, drag, and weight occur? How could these be measured?
   Lift = perpendicular to the wind direction, opposite of gravity force (weight) Drag = Perpendicular to lift, parallel to and in the same direction as wind Measurement strategies may vary, though some students will think of using a scale.



2. Newton's Third Law states that for every action that is an equal and opposite reaction. How is this related to kite flying? (Hint: How is it related to #1?)
   Lift is the force of air pushing on the kite as the kite pushes down (with the help of gravity and weight).



3. What is cant or bowing? How does cant help create lift and stability? Is there a limit to its power (too much or too little cant)?
   Bowing "can be a smooth curve or an angle," often "at the center of the kite." It helps the kite catch the wind, like a parachute does. It can increase lift, especially if the kite is like a cambered wing (see below), due to Bernoulli's Principle. Having too much cant might trap wind and create too much drag, or provide too much weight. Having too little will cause kite to act as if there is none, so the pressure difference between the top and bottom of the kite is not very different.



4. Some kites have one string, and some have more. What are advantages to having more?
   More strings mean more maneuverability that can help the kite do tricks and move more quickly.



5. Some kites fly better at different wind speeds. Describe the speeds and which kites work best with them. Also describe the feature of each kite that makes it best suited for that speed.
   "Deltas, diamonds, and dragon kites fly well in light to medium winds (approximately 6-15 mph), while Box Kites and stickless Parafoil kites fly better when the winds get a little stronger (approximately 8-25 mph)." Box and parafoil kites have depth to them or several layers of sails, so wind needs to be strong enough to work between these layers and still provide significant pressure differences. The low-wind kites have a single layer, so require less wind.



6. What is venting? What purpose does it serve?
   Venting involves cutting slits or holes for air to pass through. This can provide stability for the kite.



7. Almost all kites have tails. What functions do they serve? Would it be better to have a long or short tail for a kite at high altitude?
   Tails provide flight-axis stability to keep the kite from spinning about the axis (rolling) or darting laterally. It also provides downward weight to prevent too much pitch movement. (Aesthetics may also be mentioned.)
   Long tails at better at high altitude; more force is required to stabilize the kite, and a long tail can produce more drag than a short tail.



8. What is a rudder and where would you find it on a kite? How is it controlled? What purpose does it serve?
   "A rudder is anything that is oriented perpendicular to the plane of the main sail of the kite." It can be controlled by the wind (if attached in a stable manner to the main sail / kite frame or with a tail to keep it in place), or by a string the kite flier can control. If controlled with string, it can be used for steering.



9. Most people think kites are just for fun. However, historically kites have had more functional purposes. What are these?
   "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. " Kites carried people who provided air surveillance, as well as messages received by airplanes or people living at high altitudes. Kites were used to improve velocity in buggy or boat travel, and marked locations of people lost at sea. Kites have also been used "to measure, and conduct scientific experiments, for target practice, to fight and compete, to entertain, and a endless list of other utilizations," including construction of buildings.



10. Bernoulli's Principle is very important for flier design. Describe the principle and how it will apply to your kite.
    As air passes over propellers, cambered wings, or even a cambered kite sail, the air above the sail moves over more area, so its pressure decreases. Conversely, the air at the bottom has a higher pressure. This pressure difference results in lift. One interesting thing for students to test is comparative lift between a kite that is like a cambered wing, made up of a bowed sheet and a flat sheet, such that there are two sheets enclosing empty space, versus a kite with a single bowed sheet.



11. Symmetry is very important in almost all designs, and an example of this is the formation of a dihedral. What is a dihedral? If your kite is asymmetrical, what is likely to occur?
    The dihedral, or angle formed where two sides of the kite come together, must be balanced or symmetrical, so that wind presses equally on both sides. If it is not, the wind presses unequally on the sides and it will roll. Asymmetry in other parts will cause the kite to be unstable.



12. What is pitch and roll? What parts of the kite influence pitch and roll?
    Pitch is rotation about the lateral axis (movement of top tip downward).
    Roll is rotation about the longitudinal (vertical) axis (left tip goes to right).
    If the kite is not balanced on right and left wing, rolling may occur. If it is not properly balanced with bridal, top, and bottom, the kite may want to pitch.



13. What is the bridle point? What trigonometric equation is used to find it?
    The bridal point is the point at which the string attached to the kite attaches to the bridal (main flight string). The equation to determine where it should be (x, y) is:
    

    X = KcosA; y= KsinA
    CosA= (K² + H² Ð (B-K)²)/2KH

    
    K is the bottom string length attached from bridal point to the kite.
    B is the top string length attached from the bridal point to the kite.
    H is the height of the kite.



14. Aspect ratio is an important concept to consider when developing any flier. What is it? Describe how aspect ratio influences lift and drag. Which is better: a kite with a high or low aspect ratio?
    Aspect ratio = span / chord for a flat kite OR (span * span)/area for more complex kites.
    The aspect ratio is directly related to the ratio between lift and drag. Thus, the higher the aspect ratio, the higher the lift during flight. Some people, however, state that it is more difficult for a high aspect ratio kite to take off than a low one.



15. If the wind is coming from the East, in which direction do you run/walk, to get your kite to take flight?
    Your back should be to the wind, so your kite will take off into the wind.



16. Experimentation with kites led several scientists to some major discoveries / developments in many fields. List as many of them as you can:
    Answers will vary.
    
    1. Study of variations of temperature and altitude
    2. Research electricity (Ben Franklin & Alexander McAdie)
    3. Aerial Photography
    4. Development of the Airplane and Gliders (Alexander Graham Bell and Wright Brothers)
    5. Bridge construction Ð kites assisted in laying initial spanning lines (Homan Walsh)
    6. Improvements in target practice for moving aerial targets (like airplanes in WWII)(Paul Garber)
    7. Transport of messages between ships and aircraft (WWII development)(Paul Garber)



17. Do you have any other questions about kites? (optional)

Here are sites to start your quest. Remember to use your FIND function in your browser to speed up scanning!:

1. Kite Museum: Stabilizing Principles of Flight (yes, it is incomplete): http://www.win.tue.nl/~pp/ kites/fak/science/stabilizing.principles.html
2. History and basic info on kites: http://www.grc.nasa.gov /WWW/K-12/airplane/kite1.html
3. Kite history, designs, aerodynamics (see science section under teachers) from National Kite Month's web site: http://www.NationalKiteMonth.org/
4. Aerodynamic forces on a kite: http://www.grc.nasa.gov/ WWW/K-12/airplane/kiteaero.html
5. Bridal point geometry: http://www.grc.nasa.gov/ WWW/K-12/airplane/kitebrid.html
6. The Kite Zoo (plans and information on the number of lines and kite use): http://www.kites.org/zoo/
7. How to fly different kites: http://www.gombergkites.com/how.html
8. Kite terminology index: http://www.win.tue.nl/~pp/kites/terminology/kiteterm.html#aspectratio
9. A very detailed and well written response to questions about aspect ratio: http://www.kites.tug.com/Building/msg00120.html
10. Aeronautics in the context of airplanes and other flying things explained. Includes Bernoulli's Principle: http://quest.arc.nasa.gov/aero/virtual/demo/main/maeronautics.html
11. Geocities kite sites: http://www.geocities.com/Colosseum/4569/
12. Plans, pictures, and general information: http://enterprise.sct.gu.edu.au/~anthony/kites/
13. Kite history, plans, and general information: http://www.total.net/~kite/index.html
    your kite! Measure the lift and drag vectors, as well as height, using trigonometry (see resource list)!

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