VAF Forums

VAF Forums (https://vansairforce.net/community/index.php)
-   RV-12/RV-12iS (https://vansairforce.net/community/forumdisplay.php?f=73)
-   -   3-Blade Sensenich Prop - Now available for RV-12is/RV-12 (https://vansairforce.net/community/showthread.php?t=179257)

greghughespdx 02-03-2020 05:34 PM

3-Blade Sensenich Prop - Now available for RV-12is/RV-12
 
Van's has published updated RV-12/12iS powerplant kit order forms, a new plans section (47AiS/U) and a service letter (SL 19-12-31), all of which are related to the now-available optional 3-blade Sensenich propeller kit.

We displayed this prop on a stand in our booth at Oshkosh last year and flew it to the show on one of our factory aircraft. It garnered quite a bit of interest. Now that the engineering has been completed and testing of the final install package is all wrapped up, the three-blade prop and spinner kit is available to order as an option on new powerplant kit orders (you'll get to choose either a two-blade or three-blade prop when you order). You can also place a stand-alone order for the prop without the rest of the Powerplant kit (just use the powerplant kit order form and select only the 3-blade prop option in that case).

Note that when building your airplane, in order to register ELSA the parts - including the propeller - must be bought directly from Van's and tracked in our records under that aircraft serial number. Once an aircraft has been licensed and registered ELSA you may, of course, make any changes as you wish.

People will, of course, want to know what's different between the two-blade and three-blade prop. Our testing experience showed that:
  • 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).

And, of course, there's the aesthetics: The blades are wider on the two-blade prop. Some folks prefer the look of three blades, while others prefer two. Some people like a thinner blade, while others prefer the "beefier" look.




Dvalcik 02-03-2020 07:24 PM

new prop
 
Installed the new Sensenich 3 blade replacing my 6 year old 3 blade Sensenich a few months ago. Longer blades and thinner than the original 3 blade I had.

.

Still dialing in the pitch, but performance is much improved from the older 3 blade. I picked up a few knots but still have the climb. Since I never had a 2 blade I can?t compare it since I started with a 3 blade. Performance seam very close when flying next to my buddies. Sound a little different on the ground, but smooth. :)

rvbuilder2002 02-03-2020 09:55 PM

David,
I am glad to hear that your experience parallels what we discovered.

That the original 3 blade with wide cord blades did not perform up to the level of the two blade. We just didn’t feel that we could promote it as a viable option with the only virtue being cool factor, at the expense of slightly reduced performance.

Though to some, the skinny blades don’t have the same wow factor, but it at least does provide a slight performance boost over the two blade (as mentioned.... a modest increase in climb rate while maintaining the same cruise performance).

Because of some refinement that Sensenich was able to do to the hub while changing the blade design (likely allowable because the blades were lighter as well) the overall weight of the 3 blade install is lighter than the two blade which is good for helping to maximize useful load. The weight reduction is at a less than ideal location as far as baggage payload goes, but it doesn’t seem to be a factor on RV-12’s that have a standard build configuration.

Once dynamically balanced well, it is very smooth. The simplification and weight reduction do come at a price (besides just the higher cost)......... there is now 3 blades that need to be adjusted to have closely matching pitch angles, and there is no indexing methods incorporated into the propeller. Not a big loss in my mind because they don’t work well enough to set the blade pitch close enough to each other to get it running real smooth anyway. Just something to be aware of though.

Piper J3 02-04-2020 02:43 AM

Does Sensenich require prop disassembly/visual exam at Annual Condition Inspection? Putting three blades back together correctly every twelve months doesn't sound like fun...

rvbuilder2002 02-04-2020 08:56 AM

Quote:

Originally Posted by Piper J3 (Post 1405363)
Does Sensenich require prop disassembly/visual exam at Annual Condition Inspection? Putting three blades back together correctly every twelve months doesn't sound like fun...

I think the specified inspection procedure is the same for the 3 blade as for the 2 blade. It is not that big of a deal after getting a little experience doing the blade adjustment.

One benefit over the two blade is that the hub design is different in such a way that the propeller can be removed from the engine as a complete assembly without disturbing the blade pitch adjustment. This also allows for disassembly or assembly of the propeller with it laying on a work table.

dpemmons 02-04-2020 09:31 PM

Quote:

Originally Posted by rvbuilder2002 (Post 1405440)
One benefit over the two blade is that the hub design is different in such a way that the propeller can be removed from the engine as a complete assembly without disturbing the blade pitch adjustment. This also allows for disassembly or assembly of the propeller with it laying on a work table.

Oh this is super interesting - it means one could build a jig that would let you dial in all the blades precisely and hold everything fast while you tighten the bolts.

Wolf 02-05-2020 07:32 PM

How much lighter is this prop as opposed to the two blade option?

rvbuilder2002 02-05-2020 10:19 PM

Quote:

Originally Posted by Wolf (Post 1405863)
How much lighter is this prop as opposed to the two blade option?

I may be off a bit (memory is going bad) but I think it is just shy of 6 lbs lighter.
Seemed hard to believe when we first weighed it but each blade is quite a bit lighter than the what a 2 blade blade is, plus the lower hub mass. It all adds up......

steveb 02-06-2020 08:20 AM

steve from Sensenich here.

Yes, the disassembly time for the new 3 blade is every 2000 hours.
We bobbled our initial release of prop instructions and had annual disassembly on there by mistake, but the current revision instructions on our website have the correct inspection interval.
3Y0-Installation-Instructions-rev-C-20200204-1.pdf

NinerBikes 02-06-2020 09:17 AM

Interesting that when landing it has increased braking action.

Will the POH be revised for the 3 blade prop to reflect this change, in terms of glide ratio /glide slope when dead stick landing, in the event of an emergency?

I believe with the 2 blade prop currently it's 13:1, or about 2.47 miles per 1000 ft elevation loss?


All times are GMT -6. The time now is 07:17 AM.