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  #1  
Old 05-11-2019, 07:45 PM
Tacco Tacco is offline
 
Join Date: Jan 2017
Location: White Salmon, WA
Posts: 86
Default Prop Pitch Setting and Zeroing to Canopy Deck

The KAI says to calibrate your level to the canopy deck then measure the prop pitch. I did this and got it set to 71.4 as recommended.

Today after a test flight I was chasing down a slight vibration. I measured the prop pitch at 67.1 on both blades.

Then I remembered that I used to righ side of the canopy deck to set the blades, today I used the left side.

Measured the canopy deck sides and sure enough there is a 4 degree difference!

Donít know what to make of this, just putting it out there. Iím thinking the important thing is that the blades are within .1 degree of each other and that ď71.4Ē is a relative thing ?
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  #2  
Old 05-12-2019, 02:35 AM
HansLab HansLab is offline
 
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Location: Netherlands
Posts: 67
Default

perhaps the gain in weight makes the difference? Fuel on the right side, you added to it...? Just guessing.
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  #3  
Old 05-12-2019, 05:52 AM
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joedallas joedallas is offline
 
Join Date: May 2010
Location: Spring Hill Fl
Posts: 723
Default Maybe you level is of by 2į

Steve

Rotate your level 180° ( the same end of the level forward )

Maybe you level is off by 2°

if so recalibrate your level

It is hard to believe longerons are 4° different. Your readings may be different if you are parked on a large cross slope.

The prop pitch should be 71.4° from level or 18.6° from plumb when the longerons level ( 18.6° from plane of rotation )

You must add or subtract from the angle if the longerons are not level.

Joe Dallas




Quote:
Originally Posted by Tacco View Post
The KAI says to calibrate your level to the canopy deck then measure the prop pitch. I did this and got it set to 71.4 as recommended.

Today after a test flight I was chasing down a slight vibration. I measured the prop pitch at 67.1 on both blades.

Then I remembered that I used to righ side of the canopy deck to set the blades, today I used the left side.

Measured the canopy deck sides and sure enough there is a 4 degree difference!

Don’t know what to make of this, just putting it out there. I’m thinking the important thing is that the blades are within .1 degree of each other and that “71.4” is a relative thing ?
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Last edited by joedallas : 05-12-2019 at 08:28 AM. Reason: Clairification
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  #4  
Old 05-12-2019, 08:00 AM
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Piper J3 Piper J3 is offline
 
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 1,384
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Quote:
Originally Posted by Tacco View Post
Measured the canopy deck sides and sure enough there is a 4 degree difference!
This isn't possible. The RV-12 is CNC punched and self-jigging. The holes line up and the airframe is true and straight. There can’t be anywhere near 4° mismatch in the longerons otherwise the canopy would never close properly. My guess is your technique with digital level needs improvement.

Follow instructions on KAI PAGE 47-07 exactly and use tools as described. Technique and repeatability are key to good outcome. When blades are set correctly you will achieve very close to 5150 rpm in initial climb with full power. This will translate to near 115 knots @ 5500 rpm and throttle will be pulled back about 1” from wide open throttle at this cruise setting. 71.4° is starting point. Set blade pitch to achieve above results.

If you are still having difficulty, I can make a more detailed step-by-step set of instructions for setting blade pitch.
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80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
RV-12 E-LSA #120058 AWC July 2012 N633CM
RV-12 Bought Flying Oct 2015 with 48TT - Hobbs now 441

LSRM-A Certificate 2016
Special Thanks... EJ Trucks - Crew Chief A-4 Skyhawk
and MJ Stricker (CFI) - 1st Lt. Captain B-17H

Last edited by Piper J3 : 05-12-2019 at 08:05 AM.
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  #5  
Old 05-12-2019, 10:01 AM
Tacco Tacco is offline
 
Join Date: Jan 2017
Location: White Salmon, WA
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Default

Ok here is what I think is going on...

My level is a little too long to position exactly fore and aft due to rivet interference on the canopy deck. Therefore, I angle it slightly to fit aside the rivet line and sit flat. When I bent the longerons, it is possible that they are out of plane laterally, e.i. twisted. Iím pretty sure the outside edge follows the top edge of the fuselage skin, not sure the inside edge does.

On my way to the hanger today to check this out and will let you know.
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  #6  
Old 05-12-2019, 12:02 PM
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scottmillhouse scottmillhouse is offline
 
Join Date: Apr 2007
Location: Madison, AL
Posts: 278
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I have found that contrary to Vans procedure on zeroing first on longerons, that for my plane and procedure it does not then reference to the 71.4 requested and could allow you to get a degree off. After searching for the right pitch, to be repeatable I found it best to do all based upon true level. Probably repitched flat and coarse a half dozen times and am not back to 71.4 for all around performance.
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  #7  
Old 05-12-2019, 02:08 PM
Tacco Tacco is offline
 
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Location: White Salmon, WA
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Joe had it right. The level is off. If I set it on the deck and zero it, then rotate it 180, it measures 4.4 degrees. Weird.

Lesson learned, important to maintain levelís orientation when taking the level from the deck rail to the prop. Just as the KIA mentions.
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  #8  
Old 05-12-2019, 02:33 PM
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joedallas joedallas is offline
 
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Location: Spring Hill Fl
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Steve

I think your you aircraft may have a 2.2° slope on the deck rail

You need to calibrate on a known level surface.

There should be instructions on how to calibrate your level.

Joe



Quote:
Originally Posted by Tacco View Post
Joe had it right. The level is off. If I set it on the deck and zero it, then rotate it 180, it measures 4.4 degrees. Weird.

Lesson learned, important to maintain level’s orientation when taking the level from the deck rail to the prop. Just as the KIA mentions.
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  #9  
Old 05-12-2019, 03:32 PM
John-G John-G is offline
 
Join Date: Jan 2012
Location: Northeast Ohio
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Quote:
Originally Posted by Tacco View Post
My level is a little too long to position exactly fore and aft due to rivet interference on the canopy deck. Therefore, I angle it slightly to fit aside the rivet line and sit flat.
Steve -

To make the rivets on the canopy deck a non-factor, I place a thick piece of flat aluminum directly on the canopy deck then set my level on the flat aluminum. This allows my level to clear the aforementioned rivet heads.

Happy flying,
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  #10  
Old 05-12-2019, 07:36 PM
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Piper J3 Piper J3 is offline
 
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Quote:
Originally Posted by joedallas View Post
Steve

I think your you aircraft may have a 2.2į slope on the deck rail

You need to calibrate on a known level surface.

There should be instructions on how to calibrate your level.

Joe
Actually, no. You want to zero the level on the longeron. Use the copilot side because that is the side of the prop you will measure prop blade. The pitch angle is the difference of blade angle as compared to reference angle of longeron. Airplane need not be level...
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Jim Stricker
Hinckley, Ohio (1OA2)
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
RV-12 E-LSA #120058 AWC July 2012 N633CM
RV-12 Bought Flying Oct 2015 with 48TT - Hobbs now 441

LSRM-A Certificate 2016
Special Thanks... EJ Trucks - Crew Chief A-4 Skyhawk
and MJ Stricker (CFI) - 1st Lt. Captain B-17H
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