What you Need
What to do
Tape the three pencils together:
It is a good idea to put something soft under the card when you are doing the punching - otherwise you will probably either make a hole in your table, or your hand.
Make sure the holes are quite loose on the launcher, so that the card can lift off easily.
What may happen
With any luck, and a bit of practise, you should be able to get the helicopter to take off and fly for 3-4 seconds.
Why does it happen?
When you spin the piece of card, it moves through the air like a wing. As the air hits the flaps, it is forced downwards. Isaac Newton worked out that if you push something one way, it will push you back; so the card pushing the air downwards means that the air pushes the card upwards.
Essentially you have built a rotating wing. The wing is moving through the air even if the card stays over the same place, therefore it can hover.
This is exactly the same principle as a helicopter, but a helicopter has added problems. Because its engine is always pushing the rotor blade around, the equal and opposite force should cause the helicopter to spin in the opposite direction. This is why helicopters have to have a tail rotor to provide a balancing force.