2 blade vs 3 blade propeller

[Deano747]

Hi. Looking for opinions on fitting a 2 blade or 3 blade propeller to my Rotax 912is with a constant speed unit.
I know that the old wisdom was that 3 blades were better for takeoff and 2 blades for cruise as the 3 blade was 1) heavier and 2) had more drag, but a lot of that was based on either fixed pitch or ground adjustable propellers and is the wisdom still valid for operation with a CSU (mechanical knob to a hydraulic actuator) in the age of the new composite materials (light & stiff) the blades are constructed from.

[zaitcev]

I don't think it matters what material is used in construction. A propeller with a smaller number of blades will be more effective. Some designers in the past even experimented with 1-bladed propellers. That said, the diameter plays into it as well. On many airplanes it's not feasible to make propellers larger and the gearing taller (or it may be a direct drive to begin with).

Currently I fly a Mooney and it indeed the only difference is the better climb and greater weight for propellers with greater number of blades there. They are all constant speed units.

On an LSA, every pound mattered to me, I even fought with carpets. Of course I would use a two-balded propeller if I could.

[Dave C]

If that is true I wonder why most LSAs come equipped with 3 bladed propellers. Why is that?

[3Dreaming]

If that is true I wonder why most LSAs come equipped with 3 bladed propellers. Why is that?

Because takeoff and climb performance are more important than speed for a LSA. Also in my opinion three blade propellers tend to run smoother that two blade propellers.