Parametric Balloon Nozzle

Simple, quick and easy to print, parametric (you can change the sizes) - this is a nozzle to go in the mouth of a balloon. When you inflate the balloon and let it go, the nozzle controls the rate at which air is released from the balloon, which you can then adjust for maximum flight time, or altitude, or just for fun.

The .scad design includes fins, and I printed a few with fins, but they're not practical at all when it comes to filling the balloon with air, and I didn't see any improved flight characteristics. I did notice that a heavier (more infill) nozzle seems to increase stability, keeping the balloon more upright for more controlled flight.

For 12" latex balloons, I found that about 3.5mm openings were good for long flight times, much smaller and the weaker balloons don't make enough thrust to fly.