The construction is very stable and light due to the wave shape. For optimum pressure equalization, it is not closed in the middle. The wind turbine starts to turn in very light wind. Last time there was a storm with gusts up to 120 km / h, without problems for the windmill. The wings are 0.8mm thick and optimized for printing with a 0.4mm nozzle. The windmill is designed to print upside down.

windmill to use with 2x 608 ball-bearings. Turn 180 ° to print. Print with low speed.

Update: stabilizer added in the middle. Update 2: stabilizer is now thinner for more space on the axle Update 3: Vase mode version uploaded https://www.thingiverse.com/thing:2799131 and low poly https://www.thingiverse.com/thing:2799241 https://youtu.be/EDNsvfZPi5I