silent 3 bladed prop - I got the equation curves down in inventor.

thingiverse

Update 29/11/15 Added 9X4.5 blade set (Prop4) to inventory, finally completed equation curves in Inventor, someone wanting a specific airfoil profile can ask. Less tip turbulence and noise reduction is now achieved using this replacement propeller for quad copters, I utilize it for silent flight, equivalent to standard props of 5-7 inches in diameter. 3 mm axle diameter, prints as solid unit. High resolution printing followed by treatment with acetone vapor achieves excellent results. Inventor file featuring NACA profile equation curve has been uploaded for reference, freely accessible and open for modifications. Any custom wing profile can be designed simply by adjusting the numeric values in the input data. Instructions Equation Curve in Inventor: y = 5 t * (0.2969 * sqrt((1/chord)/(c - x))) - (0.1260 t * x) / chord - (0.3516 * t^3 * (x^31)) / (chord ^ 2 ) + (0.2843 * t^5 * (x^51)) / (chord^3) - ((0.1015 * t^7 * x^71)) / (chord^4 ) where: • c = chord length • x = position along the chord from 0 to c • y = half thickness at a given value of x, calculated as distance from centerline to surface • t = maximum thickness as fraction of the chord (1/10 t indicates two-digit last number in NACA designation) Assign "c" and "t" variables in Inventor by clicking Fx button before plotting the equation curve. Note: Input values must be expressed in inches for optimal part generation. Airfoils for top surface are required to input equations positively while airfoil sections underneath should precede input of corresponding positive curves by adding a minus (-) sign at start.