Pencil-copter blade

thingiverse

This is something that has been made available elsewhere, but it's likely too expensive to have gained much popularity. It's more art than science, which makes it challenging to get right without a 3D printer. The size and orientation will probably need adjustment for proper printing. Plastic should give slightly at the hub, while fitting snugly on a typical 6-sided pencil. The idea is to create a common toy, similar to those rudimentary "helicopters" that people use two hands to spin the axle and then release. This is just one of those silly things that can be used for modest hijinks, but it's also necessary to exercise caution. Using an unsharpened pencil is recommended.