2016/02 © Hideo Nakano nh1886@yahoo.co.jp STRAW KITE
Introduction We can build up an improvised airplane, which has a plastic straw skeleton, a rubbish bag sheet wing and a rubber band powered toy propeller. Please collect uniform quality 227 mm long, 6.0 mm in diameter straws and 7.0 mm in diameter hard straws (longer than 156 mm). The shape of the plane looks like a kite that is why we call it gStraw kiteh. If you can find suitable rubber bands, it flies farther than 20 m.
Materials and tools
How to make the straw kite fly We recommend that please play with this kite in a big room like a school gymnasium. Hold upper part of the propeller unit axis with your left hand. Wind up rubber band connected to the propeller through turning the propeller clockwise with your right index finger. Rotate the propeller at least 150 times. (From the second flight you can rotate the propeller up to 200 turns to wind up.)
1. Wing sheet
Using good paper boards, make two wing templates.
Place a plastic sheet on a cutting
board and put the two templates on it. (If you can place some sheets
nicely overlapped, you can cut them at the same time.)
2. How to cut straws
The photo below shows cutting result of 227 mm long 6.0 mm in diameter straws
Using 7.0 mm in diameter hard straws, make the following pieces. On the lower left photo, from left: A propeller axis holder, a propeller unit axis, four 50 mm joints and a upper cross beam core. The lower right photo shows the magnified image of the propeller axis holder.
3. How to build up the kite skeleton 3.1 Upper cross beam We can start out building up the kite skeleton with the upper cross beam. We need beam core to reinforce the middle of the beam.
1) Insert a half of the upper cross beam core into a long arm of an upper cross beam and insert a remaining half of the beam core into a long arm of another upper cross beam half. 2) Make sure that twist one of the upper cross beam half to face two short arms same direction. 3) Apply 15 mm x 24 mm sticky tape strip on to the centre of the beam to connect two halves. 4) Insert an end of the beam into a propeller axis holder.
An actual image
3.2 The keel, front wing beams, and lower cross beams Now we move on to connecting the keel, front wing beams. Later you can see the lower cross beams and the upper cross beam will make the following triangle. We have to connect the keel straw and the front wing beams to make a gVh shape when you look at the nose of the kite.
3.3 Wing beam extensions and keel extensions We are going to use joints made of thick straws to extend the wing beams and the keel. Please prepare double sided sticky tape (18 mm in width) and sticky tape (24 mm in width) for connecting extensions.
3.4 Installation of the propeller
Connect two rubber bands to make a short rubber band chain. We need two chains (4 rubber bands). Pass a 50 cm copper wire or a fishing line through one of the rubber bands of each chain like the image above. Pass the copper wire ends through propeller unit axis (see the right second image).
Pass a short and flat bamboo stick through rubber band ends at the kite nose. Then connect the toy propellersf metal hook at the opposite ends of the rubber bands. (Read the gRubber band helicopterh manual to make the propeller.)
3.5 Paste plastic sheet wing
4. How to balance the kite The flight ability and controllability of the straw kite depends on the quality of the straws, rubber bands, and the propeller. After you make several straws kites, you can find that accuracy is extremely important to make a good kite.
Some of you might have a question: gWhy do we connect paper clips at the end of the LEFT front wing beam not at the end of the KEEL EXTENSION?h
Firstly, we would like to confirm the role of the toy propeller. The propeller give a backward thrust (action) and the kite moves forward (reaction). The propeller gives a fast air flow so that the air pressure above the wing becomes lower than the air pressure below the wing. This is why the kite generates lift (but it is not big). If you have learnt gBernoullifs principleh, you can understand why the kite flies easily.
Lastly, the straw kite has a propeller torque effect problem like real single propeller airplanes. You can charge potential energy into the rubber bands through rotating one of the propeller blades clockwise. After you release the blade, the propeller starts rotating anticlockwise (counterclockwise). This rotation gives a clockwise twist to the kite. In order to reduce this torque effect, we connect paper clips at the end of the left front wing beam. If you want to make the straw kite fly straight, please add or remove (a) paper clip(s).
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