The Wind Tube encourages rapid iteration and testing of hypotheses with very little time between making a change and testing the design's aerodynamics.
I have been iterating on a bird design. It started with a body made of pipe cleaners and wings made of feathers. I soon upgraded to using part of an aluminum can 6-pack holder as the basis for the body.
It flew well in the wind tube, gliding along the acetate wall and remaining aloft for at least twenty seconds.
Next, I added a cardboard beak. Two layers of thin cardboard was too heavy, one worked great at keeping the bird aimed into the air current.
The wind tube creates opportunities for simple challenges or prompts. Goals can be adjusted depending on what you manage to design and how it reacts towards the goal you set. The bird remains interesting on many more levels. Launching, for example, can happen from the top or bottom of the wind tube and produces different effects. More exploration is in order!