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-12is 2blade vs 3blade prop

Daniel S.

Well Known Member
Thinking of ordering the remaining kits for my -12… Does any one have a side by side comparison of the 2 vs 3 blade prop performance on the -12? Does it make a difference? Any benefit of the 3 blade besides cool factor? I recall when I was doing research for my -7 project, I found that the 3 blade props were a little less efficient / a couple knots slower. Any insight much appreciated!
 
The 3 blade is going on mine.

IMHO: The 12iS is an LSA, so top speed isn't a primary concern for me.
3 blades (commanche experience) help in acceleration and climb, but not on the top end, like cruise. They also "seem" to be quieter. 3 blades break up the thrust pulses into shorter duration and less powerful beats. It may be more psycho acoustic, but they seem quieter to me in the cabin. They also might reduce lower frequency resonances that cause rumble.
Plus, I think its cool. Some people don't, but I do...

:D
 
Don't know if the Rotax would be any different than on other motors, but a 3 blade may be noticeably smoother.
 
Here is what Van's has to say (from https://www.vansaircraft.com/2020/02/three-blade-propeller-for-the-rv-12-rv-12is-available/)

-Cruise performance was the same (at lower altitudes)
-Climb performance was greater
-Propeller braking action was slightly greater, which allowed a slightly steeper descent angle in the pattern
-The sound/pitch is different, although the measured noise level is about the same (they are the same diameter).

There are also reports of the cowling being easier to remove and attach with the 2 blade.

I don't think you'll go wrong with either choice. For me, it came down to seeing them in person. While I generally prefer three blade props, the three blade for the 12 has very skinny blades. Whenever I see it, I can't help but think that thing belongs on a powered parachute.
 
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