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  #1  
Old 04-27-2018, 11:23 AM
Piper J3's Avatar
Piper J3 Piper J3 is offline
 
Join Date: Nov 2014
Location: Hinckley, Ohio
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Default Refining Prop Pitch...

Iím trying to find optimum prop pitch for my RV-12/912 ULS/320TT. Most of my flying is below 4000 MSL and airport is 870 MSL grass runway. If Iím going somewhere Iíll flight plan ~ 7000 MSL.

Iíve been adding a couple tenthís degree pitch and today I have performance listed in table below with one person aboard and half fuel.

Engine is running smooth and seems happy. Temps are all good.

Question - Do you think 4920 rpm is too slow for full power climb?
-
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Jim Stricker
Hinckley, Ohio
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2004
80 hrs Flying Aeronca Chief 11AC
1130 hrs Flying 46 Piper J-3 Cub
RV-12 E-LSA #120058 AWC Jul 2012 - Bought Flying Oct 2015 with 48TT - Hobbs now 400

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  #2  
Old 04-27-2018, 01:11 PM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
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Quote:
Originally Posted by Piper J3 View Post
Question - Do you think 4920 rpm is too slow for full power climb?
-
I do.

You have likely crossed over to the coarse side of ideal, where additional pitch wont really give you any more speed but will degrade climb.
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Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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  #3  
Old 04-27-2018, 02:23 PM
Driftdown Driftdown is offline
 
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Location: Clearwater, Florida
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For overall best performance (climb and cruise) the best RPM is 5600-5650, set at wide open throttle (WOT), flown straight and level, at your typical cruise altitude. Here in Florida, that is 3500 ft MSL for me.
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  #4  
Old 04-27-2018, 04:23 PM
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scottmillhouse scottmillhouse is offline
 
Join Date: Apr 2007
Location: Madison, AL
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Default

I agree, way too coarse. I wasted a lot of time way over pitching mine but at that climb RPM I was seeing 128 knots at 5500 with Dynon Betty yelling at me for going too fast. Flattened a lot to about .2 coarser than Van recommends getting about 5080 at 75 knots but I climb after initial about 85 closer to 5200. My SNF trip at 3500' solo I was seeing 120 TAS at around 5360 at 25.4 MP. Hot weather and time will tell on climb performance but for now it appears I gained about 5 knots in cruise for my long cross countries from my initial pitch setting.

At this pitch I'm also getting 5600- 5700 WOT at around 3500', goes to redline above.
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Last edited by scottmillhouse : 04-28-2018 at 09:30 AM. Reason: added text
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  #5  
Old 04-27-2018, 05:38 PM
DHeal DHeal is offline
 
Join Date: Sep 2006
Location: Windsor, California
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Over-pitching your prop has the potential to damage your engine. See Figure 1 of ROTAX's SL-912-016R1 at:

https://legacy.rotaxowner.com/si_tb_...912-016-r1.pdf

I use the numbers Driftdown noted above and am happy with the balanced climb/cruise performance.
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Last edited by DHeal : 04-27-2018 at 06:01 PM.
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  #6  
Old 04-27-2018, 10:35 PM
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Phantom30 Phantom30 is offline
 
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Iíve played around both over and undered pitched....finding Vanís recommended pitch of 71.4 to be dead on for overall performance.

Finding a good digital level was a trip, but once I got one. I can dial in both blades to within .1 degree of each other.
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RV-12 Kit#729 "N312RD" is now a full functioning fun machine!! Thanks Van for fulfilling my dream😎
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  #7  
Old 04-27-2018, 11:13 PM
Driftdown Driftdown is offline
 
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Quote:
Originally Posted by Phantom30 View Post
Iíve played around both over and undered pitched....finding Vanís recommended pitch of 71.4 to be dead on for overall performance.
Give us some performance numbers.
During straight and level flight, what is the maximum achievable engine RPM, when throttle is wide open?
At that maximum RPM, what is your indicated airspeed?
During the takeoff run, at full throttle, what is your RPM at rotation?
During climbout, at that RPM, what is the climb rate (and airplane weight)?
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  #8  
Old 04-28-2018, 06:35 PM
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Phantom30 Phantom30 is offline
 
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Quote:
Originally Posted by Driftdown View Post
Give us some performance numbers.
During straight and level flight, what is the maximum achievable engine RPM, when throttle is wide open?
At that maximum RPM, what is your indicated airspeed?
During the takeoff run, at full throttle, what is your RPM at rotation?
During climbout, at that RPM, what is the climb rate (and airplane weight)?
Will give info in a few days...as iím On my way down from Idaho to get plane in Phoenix.
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307 (CAB) Phantom
Search and Destroy (Can
Tho RVN)
Distinguished Flying Cross Society Member
CH-47 & UH-1H "Driver"
Rotax 9 Series Service IRMT

RV-12 Kit#729 "N312RD" is now a full functioning fun machine!! Thanks Van for fulfilling my dream😎
2018 Dues Paid
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  #9  
Old 04-29-2018, 05:15 AM
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joedallas joedallas is offline
 
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Location: Spring Hill Fl
Posts: 708
Default Best digital leval

Ric

I would like to know what digital level you used to get them that close.

Thanks

Joe Dallas




Quote:
Originally Posted by Phantom30 View Post
Iíve played around both over and undered pitched....finding Vanís recommended pitch of 71.4 to be dead on for overall performance.

Finding a good digital level was a trip, but once I got one. I can dial in both blades to within .1 degree of each other.
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  #10  
Old 04-29-2018, 06:59 AM
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DaleB DaleB is offline
 
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Quote:
Originally Posted by joedallas View Post
I would like to know what digital level you used to get them that close.
I bought this one (https://www.amazon.com/gp/product/B006JR8XBG). It claims 0.05 degrees resolution with +/- 0.2į accuracy. Needless to say I was skeptical and ready to return it.

What I have found is that, while I can't speak to its absolute accuracy in every situation, it is dead on at 0 and 90, at least as close as I can test it. More importantly to me, its measurements are perfectly repeatable. The same angle will measure exactly the same, every time.
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