Best DIY Boomerang in the Wide World?
Call it a Vortex, whirlpool, tornado, hurricane, dust devil, water spout... whatever you call it, it happens a lot in nature.
This Air Rocket goes higher than the tallest trees.
Here is a simpler water rocket launcher design that's easier to build and gives kids a tactile understanding of "pressure".
Wind-up Dragonfly helicopters fly higher than the tallest trees. Here is a simple version.