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2 vs 3 Blade Sensenich for RV-12iS

bshawco

Active Member
Patron
I've been wondering about the real-world pros and cons of the 2 blade vs. 3 blade prop available from Van's for an RV-12iS. The elevation of my home field is about 6,500' MSL. I know one "con" of the 3 blade prop is cost, but I'm primarily curious about differences in climb and cruise performance. However, there may well be other considerations I haven't thought of.
 
3 blades quieter. 3 blades not as efficient, more dangerous to hand prop 3 blades. 2 blades noisier, 2 blades cheaper. 2 blades more purchase options.
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3 Blade Prop

I'm a big fan of my 3 blade MT prop. Looks cool, sounds cool and performance is fantastic with CS.
 
Thanks all - very helpful! I never thought to search "Three-blade" instead of "3 blade" on the Van's site...
 
You mention the “cool” factor for three-blades. I saw the three-blade prop at Van’s both two years ago at KOSH. I thought it really looked bad. Blades are smaller cord to disperse same fixed HP. The two-blade prop with scimitar sweeping shape is eye candy in my opinion.

If you really want multiple-blades I saw this at local airport last year…
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I have had my 3-blade installed for over a year now and I love it. For performance, I can't say I noticed any difference one way or the other. It is smoother for sure and I am a fan of the 3-blade look. You can remove the entire prop as one piece without disturbing any of the blade angle adjustments. To me, that's a major advantage over the 2-blade.

Now the bad news.....I never considered that I would be adding a great degree of difficulty in removing my lower cowling. It went from trivial (with the 2-blade) to very frustrating/difficult with the 3-blade. There is just no way to position the prop, at least one blade is always in the way. If anyone knows a slick method, PLEASE let me know!!
 
Cowl Removal with 3-blade

Paul, interesting. Looking at the hours you have on the ship (205 after 4 years), it could be that the only cowl removal you would need to do would be at annual condition inspection? Then it may be easiest to simply remove the prop. You would have to inspect it and the hardware and torque check the bolts anyway.
 
Now the bad news.....I never considered that I would be adding a great degree of difficulty in removing my lower cowling. It went from trivial (with the 2-blade) to very frustrating/difficult with the 3-blade. There is just no way to position the prop, at least one blade is always in the way. If anyone knows a slick method, PLEASE let me know!!

I elongated the hole where the exhaust comes out and have been able to remove it with another persons help - one on each side and drop down, twist & angle then pull forward. Still have to be careful but I has been worth it for me. I had a 3 blade Sensenich when she was built in 2012 and later put the new Sensenich on once it came out a little over a year ago.

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Paul, interesting. Looking at the hours you have on the ship (205 after 4 years), it could be that the only cowl removal you would need to do would be at annual condition inspection? Then it may be easiest to simply remove the prop. You would have to inspect it and the hardware and torque check the bolts anyway.

Good point Tony, I am up to 230 hours now but I really liked the random inspection capability. We have had so many SBs that require lower cowl removal for inspection, I miss the easy access. Prop removal is a good option!

I elongated the hole where the exhaust comes out and have been able to remove it with another persons help - one on each side and drop down, twist & angle then pull forward. Still have to be careful but I has been worth it for me. I had a 3 blade Sensenich when she was built in 2012 and later put the new Sensenich on once it came out a little over a year ago.

Good suggestion David, I will look into that. Just buying a little more 'wiggle-room' would make a big difference!
 
Good point Tony, I am up to 230 hours now but I really liked the random inspection capability. We have had so many SBs that require lower cowl removal for inspection, I miss the easy access. Prop removal is a good option!



Good suggestion David, I will look into that. Just buying a little more 'wiggle-room' would make a big difference!

We are at the point of making the prop decision, engine order is just around the corner.

Any chance we could get some pictures of how much elongation of the cowl was necessary to get to the point of removal without removing the prop? This seems to be the only drawback (aside from cost) of the three blade so far. More info on the impact to the cowl and maintenance in general would be appreciated!
 
We are at the point of making the prop decision, engine order is just around the corner.

Any chance we could get some pictures of how much elongation of the cowl was necessary to get to the point of removal without removing the prop? This seems to be the only drawback (aside from cost) of the three blade so far. More info on the impact to the cowl and maintenance in general would be appreciated!

Since the E-LSA RV-12iS kit is a remote build of a certified aircraft (S-LSA), if modification of the cowl was required, to be able to remove or install it, it would have been incorporated into the 3 blade propeller option kit.

We have the 3 blade prop on our demonstrator and have no modification to the cowl.
It is a little bit more difficult and does require some additional care to avoid scratching paint, etc., but nothing that would push us towards wanting to remove the prop every time the cowl was removed.
 
I agree with Scott just be careful. The exhaust hole is only 1/2 to 1 inch longer. That was the only thing I did at was done at the time of the build. Two people and it is still easy. :)
 
Thank you both for the follow up. I certainly had the E-LSA situation with the modification in mind. Appreciate the comments from both.
 
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