Parametric Centrifugal Blower Impeller

I created this while exploring whether I could optimize a popcorn popper's fan.

If you are looking for guidance on designing an efficient and effective fan, take a look at Bleier's Fan Handbook, which has all the relevant equations in chapter 7.

• offset the vanes after the support rings, promoting more even airflow
• simpler bottom surface printing--no supports needed anymore
• optimized code that renders faster
• replaced Naca4.scad, which has onerous licensing terms, with an improved version of GenNACAXXXX.scad