title_body: Does the sharpness of a propeller blade affect efficiency? Some of the propellers I have used on drones have sharp edges (sharp enough that they have cut me) and others have comparatively dull edges. Does the sharpness of the leading edge of a propeller impact the efficiency of a quadcopter at all? Would it be better to use propellers with sharp or dull leading edges for race drones?
upvoted_answer: Rounded leading edges are better for subsonic aerofoils.
  
  Props and wings have to work at a range of angles of attack. The airflow has to split to pass either side of the aerofoil, and a rounded leading edge allows the separation point to move smoothly. Sharp leading edges cause a lot of drag at extreme angles of attack when air has to flow across the sharp edge.
  
  That said, the sharp edge on some props is just mould flash and can be sanded off with fine sand paper.
  
  Sharp trailing edges are OK aerodynamically but easily damaged, and dings in thin plastic can cause drag, so there's a practical limit to the sharpness of a trailing edge.