Traditionnal Bamboo Copter

thingiverse

Perfect gift toy for kids. Easy and fast print. Must be printed at a high percent infill (80-100%); the weight in the handle is key to make it fly. If the copter flips upside down when you try it, that means that infill/weight of the handle is not enough. Print Settings Rafts: Doesn't Matter Resolution: 0.1 to 0.3 Infill: 80 to 100% Notes: The key feature is the infill. How I Designed This My first prototype had a real wing profile, and handle was round. Then I simplify the design for printability and print time; the handle has now a hex shape, and the propeller's shape is minimalist. I also tried different sizes of each part, different angles of attack, and different infills. Designed with Openscad. WINGS, PROPELLERS, HOW DOES IT FLY? Teach to youngers and olders the basics of aerodynamics. No particular skills are necessary for this project, even if a few basics of forces and inertia would be helpful. It's all about understanding forces. A.S.: The difficulty of my research has been finding the correct English vocabulary for this project. I might be wrong for some words and I'm sorry about that. 1.SPEED Speed is the first thing to highlight. In aerodynamics, measured speed is always relative to the air/wind, not relative to the ground. This is measured with an anemometer. 2.LIFT What makes lift is the relationship between speed and wing shape. When the wing cuts through the air, air has two paths: along the upper surface (called the upper camber) and along the lower surface (called the lower camber). The path along the upper surface (upper streamline) is longer than the lower path (lower streamline). As shown on the picture, the blue point makes more distance than the red point in the same time. Conclusion: they don't have the same velocity. That difference of velocity leads to a difference of pressure on the wing's surfaces; more pressure under the wing than above. We now have a way to counter gravity. 3.PROPELLER Propellers work exactly the same way, except speed is given by rotation. As propeller is rotating, each point doesn't have the same speed. The speed at a particular point of the propeller can be measured this way: Speed = rotational speed * radial distance That means there are two ways to increase the lift of a prop (among others): increase the rotational speed and/or get a longer propeller. 4.GO FURTHER If your student gets involved in this project, you can lead them to explore more aerodynamics physics. Here are some keywords: drag coefficient - angle of attack - airfoil shape - ground effect - thrust and torque - wingtip vortices - ...