The parting line must be very precise and continuous around the entire perimeter of the mold cavity to allow precision molding of the very thin airfoils used on many of the APC propellers. The airfoil shapes may vary with span. 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. Also, the aft region is somewhat thicker. This alters the zero-lift angle by approximately one degree and provides greater lift without having to twist the blade even more.
All blades have some washout near the tip.
For applications where Mach number effects become significant near the tip, either pitch washout or camber reduction tailoring minimizes Mach drag rise. Hub geometry Cross-section geometry in and near the hub region is defined with specialized algorithms. Hub geometry for 3 and 4 bladed propellers is very complex because of the need to match mold parting lines at all points on the mold surface perimeter. Theoretical basis-aerodynamics Vortex theory is the basis for the computational method used to calculate blade loading. These flow field effects are computed using 3D potential flow theory.