Sensenich prop engine high rpm's

[wingnut99]

I had to replace my damaged Prince P tip but because of a 10 month wait I ended up buying a Sensenich 54 X 62 from Sonex. I didn't have any input on the specs because it's supposed to be optimized for my 3300 Gen 4 Jabiru with a Sonex airframe. I'm seeing 3500 rpm's on takeoff and climb if I don't throttle back. WOT on my Prince never exceeded 3300 unless I was in decent and the cruise speed was 135-140 at 3000 rpm's more or less. Sonex is questioning my tachometer but I haven't touched anything that should have changed it and with the slower airspeeds I'm seeing, it seems like the prop is just not the correct pitch.
My hanger neighbor says my engine sounds like it's turning faster when I takeoff than it used to. It's unnatural for me to throttle back on takeoff but I have no other choice until I can confirm that the tach is correct or not. I'll get the engine analyzer on it and check it against my Dynon HDX next time I have the engine running. Has anyone else experienced redline rpm's with a Sonex speced Sensenich?
Thanks for taking the time. Pat Murry

[rbarber]

I have the arrangement you just mentioned. And I never see such numbers. How certain are you of your tach reading? I usually see 3000 RPM on mine

'Best,

R.

[gammaxy]

Seems unlikely the propeller would be labeled wrong, but I wonder if you can use a digital level or phone app to measure the blade pitch (and thickness and chord at say 7 inches from the tip) and compare to someone else with the same propeller? Tricky part is getting a good 0 degree reference while it's mounted on the airplane--possibly off the propeller flange or by averaging measurements from both blades.

[kmacht]

Where are you located? Maybe there is another sonex near by that would be willing to let you try their prop for an afternoon to see if it does the same thing.

[wingnut99]

Thanks for all your responses. I flew for the 4th time yesterday and again my engine was heading straight into redline had I not throttled back and at 4500' cruising at 3100 I was only getting 125 knots. The Dynon tach wire is still attached to the same alternator wire as always so nothing has changed there and before I flew I had my ignition analyzer on it and it read the same as the Dynon on the tach setting. I have a device that's similar to a timing light that I will use to read the prop rotation but I'm pretty convinced that the rpm's are right. I was mostly interested in finding out what other pilot's with the same engine and Sensenich prop combination were experiencing. Mine is stamped 54 X 62 but from what I've read it isn't performing the same. I may have to call Jeff Schultz and see if he noticed any significant changes when he went from a Sensenich to a Prince. It's kinda hard to imagine that my Sensenich got cut wrong because they custom build every prop as the order's come in, so it's not like they shipped the wrong one after the 3 months it took to get it and they put the correct stamp on it apparently according to what you guy's are saying. I suppose I can get one of the chapter AP guy's to check the pitch. I'm just glad we're heading into the non flying season while I figure it out. Thanks again, Pat Murry

[rbarber]

As I said before, I have the same setup; Jab 3300 with 54x62 Sensenich prop. I have a MGL Enigma counting RPM, and the counter setting is 6 pulses per revolution, but I would need to verify that, as it has been more than 15 years since it was set up. I typically run 2950-3000 RPM on climb out at 80-90 mph. For cruise at ~3000ft I run 2750-2800 and get 135-140 mph. 2900 RPM at the same altitude will cruise at 150 mph If I go up to 8,000ft or higher, I run 3150 RPM and get ~165-170 mph. I have had similar results for more than a decade. I am curious in what you find is different on yours.

Can you send me a picture of your prop taken from the end of a blade looking toward the hub? I may be able to calculate the pitch from that.

'Best,

R.
N157SX, AKA "Sexy Hexy"
S/N 271
~1300 Hours (400 hours with a Hula girl on the dash)

[builderflyer]

I, too, have a Sensenich 54x62 all wood prop as an initial prop on my Sonex and experience numbers similar to what Barber has posted. It is a bit underpitched as at full throttle at low altitude and level flight will allow the engine to turn about 3450 rpm, 150 rpm over red line. I've also tested 4 different Prince props and kept the 54x66 elliptical prop as it offered a 5 mph increase in cruise speed at 2750 rpm without too much loss in climb rate.. When I bought the Sensenich prop some 23 years ago they did have some quality control issues as the first one received had to be returned back to the factory. If your prop is built underpitched, perhaps it was built by a new employee..........this would be all too common in today's world.

Art,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,Jabiru 3300 #261