It goes up, it goes down, it goes upside down and keeps on flying. We're talking about Curtis Youngblood's latest quadcopter prototype, but as his website says, "Curtis has been flying and competing with RC Helicopters since the early 1980s and is a Multi-time World Champion and Multi-time 3D Champion." This lucky dog has managed to turn his hobby into a business; he makes and sells radio controlled helicopters -- not the $60 ones from Harbor Freight, but sophisticated aerial beasts that can carry still and video cameras and could easily be used as short-range drones, except that these are hobbyists' toys -- for hobbyists who can afford to spend hundreds and even thousands of dollars, anyway. There are plenty of quadcopter kits on the market for lots less than Youngblood's creations, along with build-it-yourself guides. But these won't fly upside down. For that, you need variable-pitch rotors and sophisticated control systems. "But what about 3-D printing?" you ask. Of *course* you can use a 3-D printer to make a quadcopter. That was an inevitable development. Here are open source instructions for building one. Enjoy the ride!