Let's go fly a kite!

Follow these instructions to make your own kite and learn about the Bernoulli principle and Newton's Laws.

• 11 January 2007 | Updated 14 October 2011

• What you need
• What to do
• What's happening

What you need

To make your kite you will need the following items:

• paper
• crayons
• string (for the bridle) – 15 centimetres long
• bamboo
• ribbon
• tape
• fishing line (for flying line).

What to do

1. The paper needs to be a diamond shape, with the bottom triangle being twice the size of the other.
2. Now is the best time to decorate the kite. You can do this however you like.
3. After decoration, turn the kite over and tape the bamboo sticks in place. They will form a cross when taped onto the kite's length and width. Make sure you tape the longest stick first.
4. Fold your ribbon in half and tape the middle of it as a tail on the kite.
5. Next, take about 15 centimetres of string and tie a loop. This is then attached to the middle of the bamboo cross and poked through a hole to the non-bamboo side of the kite. This is the bridle.
6. Lastly, attach the flying line to the bridle.
7. Go fly a kite!

What’s happening

Humans have been flying kites for a very long time. The ancient Chinese were great kite builders. And legend has it that Benjamin Franklin discovered lightning was electrical during a science experiment with a kite – not one to try at home though! The science behind flying a kite is fairly straight forward, and is actually quite similar to aeroplane flight.

Kites are flown so that they angle into the wind, and as air hits the kite it is deflected downwards. If air is being deflected downwards then according to Newton's laws, where every action has an equal and opposite reaction, the kite is pushed upwards.

Put another way, the air travelling under the kite goes slower than the air travelling on top of the kite. This results in air travelling faster over the kite than under it. And it is this that pushes the kite upwards, just like an aeroplane wing, because the faster moving air has less pressure than the slower moving air, and the kite moves from higher pressure to lower pressure (up!).

This theory of faster air creating lower pressure is called the Bernoulli principle. Try blowing between two inflated balloons to see what happens as fast moving air moves between the two balloons, creating an area of lower pressure.

For more hands-on activities, join CSIRO's Double Helix Science Club.