RPM question

[Speed20]

Oct 23, 2020

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I have a 2l I recently maidened in September. I have a GP 2180 . I have a Prince P-tip prop 52x48. this prop is supposed to flex some to act like a constant speed prop so to speak. It turns 3000 rpm static 3000 in level flight yielding 110-120 mph at 2000 ft. I’m running a zenith carburetor and for now ,only a single mag ignition. Before my first flight, I read many posts here and thought maybe I’d pick up 100-200 rpm in flight, but 3000 is all I get no matter what till I reduce power for landing. The engine just purrs along in level flight a d sounds great . I climb at 90 getting 500-700 ft per minute. Does it sound like a prop problem or what?? I’m baffled, and would love input from you guys . Thanks, Dennis

 

[Elviar]

I'm not an expert, but it sounds like too much pitch, and the prop isn't letting the engine wind up. Does it spin faster if you point the nose down?

 

[Speed20]

I'm not an expert, but it sounds like too much pitch, and the prop isn't letting the engine wind up. Does it spin faster if you point the nose down?

Yes it does. I’m really thinking it’s too
much pitch also

 

[kennyw]

Just for comparison, I have a Sterba 52/42. It'll turn ~3,400rpm in level flight at WOT (if you give it a little time to wind up). If you push the nose over, you'd better be pulling no more than about 23" MAP by the time the airspeed hits ~130mph. Or, it'll be up around redline.

 

[Schmleff]

There used to be an entire sticky post on here about this topic. The subject was something like Read before Flight.

 

[Schmleff]

https://www.sonerai.net/threads/normal-static-rpms-new-pilots-read-before-flight.50/

 

[DeadRinger]

That’s an expensive prop. It would be cheaper to try to get the motor to make more torque at 2800-3400 rpm. Cam heads compression exhaust should be looked at if you can’t live with it. If it was me I’d want a little more climb.

 

[DeadRinger]

Then again this might be what you need. On barnstormers

PRINCE P-TIP • $600 • FOR SALE • Prince PTip prop(CCW)for a 2100 Revmaster SN842P60BT50 Contact Loren 3606062811 • Contact Loren Sievila , Owner - located Kalama, WA United States • Telephone: 3606062811 • Posted October 9, 2020 •

 

[Speed20]

Just for comparison, I have a Sterba 52/42. It'll turn ~3,400rpm in level flight at WOT (if you give it a little time to wind up). If you push the nose over, you'd better be pulling no more than about 23" MAP by the time the airspeed hits ~130mph. Or, it'll be up around redline.

Yeah seeing your numbers,42 to 48 pitch is a considerable difference. I’ve poured over the Before you fly threads previously and really think 48 is too much. Also, I’m running a TinyTach and wonder if that could be misleading.

 

[kennyw]

Yeah seeing your numbers,42 to 48 pitch is a considerable difference. I’ve poured over the Before you fly threads previously and really think 48 is too much. Also, I’m running a TinyTach and wonder if that could be misleading.

I have a TinyTach also. I verified it with a handheld optical tach. When it was wrong, it was really way wrong and inconsistent. Once I set it up right, it agreed with the optical tach within a few RPM at all times.

 

[Speed20]

Then again this might be what you need. On barnstormers

PRINCE P-TIP • $600 • FOR SALE • Prince PTip prop(CCW)for a 2100 Revmaster SN842P60BT50 Contact Loren 3606062811 • Contact Loren Sievila , Owner - located Kalama, WA United States • Telephone: 3606062811 • Posted October 9, 2020 •

Thanks for the heads up, I texted the guy and it’s a 60”x 50 pitch! Yikes!

 

[Robin Austin]

Hi Dennis.
I had an identical issue in 1990 with a Bernie Warnke “almost constant speed” prop.
I chopped it down from 54” to 52”. RPM remained almost identical. It just flew about 5 knots slower everywhere.
Thought I’d share this with you to consider before you reached for the hacksaw like I did.
Of course others may have a different experience.
Good luck.
Cheers
Robin

PS.
Try to get that election thing finished.
Sure has created some interest.
We have Endless wall to wall coverage on tv here in Australia too. Ha ha.

 

[Speed20]

Hi Dennis.
I had an identical issue in 1990 with a Bernie Warnke “almost constant speed” prop.
I chopped it down from 54” to 52”. RPM remained almost identical. It just flew about 5 knots slower everywhere.
Thought I’d share this with you to consider before you reached for the hacksaw like I did.
Of course others may have a different experience.
Good luck.
Cheers
Robin

PS.
Try to get that election thing finished.
Sure has created some interest.
We have Endless wall to wall coverage on tv here in Australia too. Ha ha.

Thanks mate! I think my problem is too much pitch (48) .

 

[kennyw]

...
PS.
Try to get that election thing finished.
Sure has created some interest.
We have Endless wall to wall coverage on tv here in Australia too. Ha ha.

Yeah, if the lefties and the righties tear the place apart, I might be moving down that way. I really like the Freemantle area (at least I did 30 years ago).

 

[Robin Austin]

Thanks mate! I think my problem is too much pitch (48) .

You’re likely right. That was likely my problem too, I just thought back then that chopping the length would pick up my rpm and hp, and thus take off performance, but it just stuffed the beautiful new prop. I eventually sold it for $50 as a ground test prop. Just thought this experience may assist in forging a positive way forward as it appears it had very, very similar characteristics. Cheers.

 

[mhflyit]

I had a 52 inch Ed Sterba prop. I couldn't get the static rpm to 2900 so Ed removed 2 inches which made it 50/50. I picked up 200 static rpm and cruised 3200+

 

[Speed20]

I had a 52 inch Ed Sterba prop. I couldn't get the static rpm to 2900 so Ed removed 2 inches which made it 50/50. I picked up 200 static rpm and cruised 3200+

Wow