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  #1  
Old 05-13-2019, 11:12 PM
Tacco Tacco is offline
 
Join Date: Jan 2017
Location: White Salmon, WA
Posts: 85
Default Vibration Sources

I have a vibration Iím tracking down. While Iím investigating the usual suspects, thought I might ask your thoughts on this possibility. Might be dumb but thought Iíd ask.

I have about 15 hours on the aircraft. Initial flights were smooth as butter. Carbs are balanced, prop is tracking and set accurately. The vibration is most noticeable through the stick as if itís a control surface issue.
Level cruise, 5000 RPM. Didnít have that until recent flight.

So hereís a thought: the earlier flights were conducted in cold weather and I never had the cabin vent open. Could an open cabin vent disrupt the propeller slip stream in such a way as to effect the elevator and/or rudder?
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  #2  
Old 05-13-2019, 11:43 PM
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Piper J3 Piper J3 is online now
 
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Location: Hinckley, Ohio
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Default

I have never noticed any control surface vibration with/without cabin vents open. Are your stabilator cables correct tension?

I'm curious why you're cruising at 5000 instead of 5500 - top of green arc?
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1130 hrs Flying 46 Piper J-3 Cub N6841H
RV-12 E-LSA #120058 AWC July 2012 N633CM
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  #3  
Old 05-14-2019, 06:47 AM
John-G John-G is offline
 
Join Date: Jan 2012
Location: Northeast Ohio
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Default

May just be something as simple as an unbalanced nose wheel rotating during flight.
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  #4  
Old 05-14-2019, 08:41 AM
DHeal DHeal is online now
 
Join Date: Sep 2006
Location: Windsor, California
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Default

Was your AP "off"? With the AP "on" you will feel some "vibrations/pulsations" through the control stick as the servos work to adjust the control surfaces.
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  #5  
Old 05-14-2019, 09:11 AM
JBPILOT JBPILOT is offline
 
Join Date: Nov 2007
Location: Jesup, Iowa
Posts: 1,629
Default Hey John - -

I had a nose wheel bolt too loose, and in fact the front tire was spinning and slightly out of balance. Check how tight it is and spin it on the ground and see how fast it stops spinning.
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  #6  
Old 05-14-2019, 09:43 AM
Tacco Tacco is offline
 
Join Date: Jan 2017
Location: White Salmon, WA
Posts: 85
Default

Quote:
Originally Posted by Piper J3 View Post
I have never noticed any control surface vibration with/without cabin vents open. Are your stabilator cables correct tension?

I'm curious why you're cruising at 5000 instead of 5500 - top of green arc?
I was doing the performance box from FT4 of the PAP.
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  #7  
Old 05-14-2019, 01:39 PM
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DaleB DaleB is offline
 
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Location: Omaha, NE (KMLE)
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Quote:
Originally Posted by Piper J3 View Post
I'm curious why you're cruising at 5000 instead of 5500 - top of green arc?
I normally cruise at 5000 if I'm just cruising, to maybe 5300 if I'm in more of a hurry. I find that 5200-ish to 5500 burns a lot more fuel for only a couple of knots extra speed.
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Omaha, NE
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Previous RV-7 project (sold)
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  #8  
Old 05-15-2019, 08:26 AM
Chino Tom's Avatar
Chino Tom Chino Tom is offline
 
Join Date: Jun 2005
Location: Chino, CA
Posts: 720
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Quote:
Originally Posted by John-G View Post
May just be something as simple as an unbalanced nose wheel rotating during flight.
+1 on the nose wheel. Although mine is an 8A, I painted a white stripe
on the tire and used a GoPro attached to the wing to verify it was
rotating (mine has a Grove nose wheel so there is no friction on the
bearings). Sure enough, it was rotating. Balancing the nose wheel
did the trick, no more vibration thru the control stick.
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  #9  
Old 05-15-2019, 07:46 PM
Tacco Tacco is offline
 
Join Date: Jan 2017
Location: White Salmon, WA
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Thanks guys! It was indeed an out of balance nose wheel.

This forum is an awesome thing! It has saved me valuable time, significant frustration, and certainly some bucks. Iím sending in a donation. 😎
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