Duxford propellors

Topic:
Rotation
"Duxford propellers" is the work of some 14-year old students attending a STEM fair activity at the Duxford Air Museum near Cambridge organised by the STEM Team East on 14th June 2012. The points A, B and D define the size and shape of the propellers. The point C is animated to revole on the circle centre A through D. Click on the "Start" button to fire up the engines!
Can you work out the image was created? Can you animate interesting creations of your own?