Pathfinders Build A Leonardo Da Vinci Helicopter/Aerial Screw Ages 9+Working re creation of one of Leonardo Da Vinci's most iconic drawings, the 15th century Aerial Screw. This STEM building kit encourages problem solving skills and hands on exploration. A fun stem activity. This working model uses a bevel gear, to spin the canopy and support structure, illustrating a way Leonardo thought flight might be possible! A fun and inspiring arts and crafts project that is spun from one of the great minds of history. A 3 d