Thin electric, slow-fly, and multi-rotor propellers typically blend the low Reynolds number Eppler E63 airfoil (inboard) with a Clark-Y similar airfoil near the tip. For applications where Mach number effects become significant near the tip, either pitch washout or camber reduction are used to minimize Mach drag rise. Most blades have some washout near the tip. This alters the zero-lift angle by approximately one degree and provides greater lift without having to twist the blade more. Also, the aft region is somewhat thicker. The dominant basis for the primary airfoil shape used in most APC propellers is similar to the NACA 4412 and Clark-Y airfoils, except the leading edge is somewhat lower. Capability exists to smoothly “splice” together widely different airfoil shapes. The airfoils may have arbitrary shapes defined with either tabular data (splined cubic fits) or analytical functions typically used for NACA airfoils. The parting line must be very precise and continuous around the entire perimeter of the tooling cavity to allow precision molding of the very thin airfoils used on many APC propellers. The APC computer software, used to define airfoils, blade shape and the resulting CNC motion, dominantly reflects parting line driven requirements. CNC milling machines are used to accurately machine the molds, aka tooling. Injection Molding Parting Line RequirementsĪPC propellers are injection molded using a pair of mold halves. The first version of the software came on line in 1989. The system has been undergoing continuous development and improvement for over three decades. This specialized software allows APC to design, analyze, and manufacture all propellers in-house at our California facility. The software is specifically tailored for model and UAV propeller design and manufacture. Engineering Design Process Used to Develop APC PropellersĪPC propeller development uses a proprietary PC based CAD-CAM software.
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