Quote Originally Posted by chargerbill View Post

The other piece of the performance puzzle is prop specs. My understanding is a long 2 blade prop is more efficient than a tri blade. Anyone have details around this?
Chargerbill,

Prop manufacturers spend millions on R&D. I’m just a guy that tinkers with small aircraft. So take the following with a grain of salt.

The best advice I can give you is to use the prop others have proven works well. There’s a reason most Rotax flyers use a 3 blade. It works. Likewise, many Rotec Radial engine installations use a 2 blade… because it works. Using the engine/prop combination that others use will save you lots of cash in the long run.

With that in mind we can try to answer your other question: Why use one over the other? A 3 blade prop is often installed on an engine/airframe to obtain greater ground clearance or to lower the tip speeds at max RPM. The 3 blade often has a lower perceived noise and vibration levels.

There is no guaranty that a 3 blade will always work better. For example: The Cessna Cardinal RG climbs and cruises faster with a 2 blade prop. The thinking is the 3 blade prop has more drag with the extra blade and it sucks up too much power. There may be something to that.

It’s a subject that can fill volumes.

Then, there is the most important reason for choosing one design over another; because it looks good.

John Pitkin
Greenville, Texas