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  #21  
Old 03-24-2017, 08:31 PM
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Mel Mel is offline
 
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Quote:
Originally Posted by Cholley6 View Post
I certainly have not built an RV and am only a student pilot, but if I am understanding the mis alignment I have another question. The 172 I have flown as a student has elevator trim only on one side. Wouldnt this trim be basically the same as this mis alignment? This would create more lift on one side of the elevator than the other. When trimming the 172 I have not noticed any tendency of the aircraft to roll. How would this be different? How could this create more tendency for roll than the slipstream or the torque of the engine? I could see this adding some drag though. As someone else said earlier, no idea, just asking.
Not quite. The trim tab only effects the elevator itself, not the aircraft. And the 2 elevators are tied together firmly.
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  #22  
Old 03-24-2017, 08:55 PM
BobTurner BobTurner is offline
 
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Actually I think Cholly has a good point. Every small Cessna generates more force on one side of the elevator than the other whenever the trim is not neutral.
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  #23  
Old 03-24-2017, 10:23 PM
Cholley6 Cholley6 is offline
 
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So are the 2 elevators on a vans not tied together firmly? And how can you only effect the elevator and not the aircraft since the aircraft can move in 3 dimensions? I understand that if the elevators were wildly mis alligned, say a foot for illustration purposes, they would contribute to roll. But something less than half an inch with very little arm on an aircraft with p factor, torque, and slipstream, it just seems negligible. It seems it would be the lesser of the variables contributing to roll.

Last edited by Cholley6 : 03-24-2017 at 10:34 PM.
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  #24  
Old 03-24-2017, 11:00 PM
BobTurner BobTurner is offline
 
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Yes the elevators are tied together.
RVs have very light roll forces. It doesn't take much to bank them.
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  #25  
Old 03-25-2017, 06:12 AM
vic syracuse vic syracuse is offline
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Quote:
Originally Posted by BobTurner View Post
Actually I think Cholly has a good point. Every small Cessna generates more force on one side of the elevator than the other whenever the trim is not neutral.
It's put on the left side elevator to counteract the P-Factor. During takeoff the trim tab is down. The torque and P-factor on a right-hand turning engine are trying to roll and turn the airplane to the left. The trim tab on the left elevator being in the down position counteracts this force to a degree. That's why airplanes with moveable horizontal stabilizers (instead of trim tabs) will roll more to the right on takeoff, requiring much larger rudder inputs. The RV-10 allows you to fine tune this through the use of two independentaly-adjustable trim tabs, one on each elevator. Those who elect to install left rotating engines, such as in the UK, are shipped a different set of plans depicting the trim tab installed on the right elevator. The RV-12 solves this problem through the use of a trim tab that runs the entire length of the stabilator. And of course the use of a Rotax 912 under the cowl, aka turboencabulator.

Oh, wait, it's not April fool's day yet.

Vic
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Last edited by vic syracuse : 03-25-2017 at 07:35 AM. Reason: spelling
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  #26  
Old 03-25-2017, 07:18 AM
paul330 paul330 is offline
 
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Had me going for a while there Vic.......

Isn't the problem that people are trying to align the elevator horns rather than the elevator trailing edges? If you clamp the elevators in line and then drill the elevator horns, you have to end up with the trailing edges aligned. OK, the horns might be out a bit and you might have to trim/file the stops a little but I really can't see how this can be a major issue.....
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  #27  
Old 03-25-2017, 10:18 AM
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Quote:
Originally Posted by paul330 View Post
Had me going for a while there Vic.......

Isn't the problem that people are trying to align the elevator horns rather than the elevator trailing edges?
Maybe for a few (if the instructions are followed it compensates for the horn misalignment that you are describing).

The problem described is when the counter balance arms of each elevator are aligned when drilling the horns (the proper way to do it), but then the inboard ends of the elevators are not aligned (usually the result of one or both of the elevators having a twist in them).
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  #28  
Old 03-25-2017, 10:48 AM
DRMA DRMA is offline
 
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One other consideration: The elevator trim tabs on the RV-10 are asymmetrical - they move at different rates and don't stay aligned with each other as they are moved by the trim servo. The difference in trailing edge position of the trim tabs will be a lot more than the offset between the 2 elevators being discussed here. So I would think that if the offset between the trim tabs isn't going to cause problems, that a small offset in the elevators shouldn't either.

I asked Van's about this characteristic of the trim tabs, thinking that I had done something wrong when building the servo bell crank. I was told that the asymmetric tabs was by design, and was correctly built.
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  #29  
Old 02-21-2021, 10:27 AM
Sportquattro Sportquattro is offline
 
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Is it better to have the counterbalance horns aligned, or the elevator trailing edge. With the trailing edge aligned my counterbalance horns are out by less than 1/4”

Last edited by Sportquattro : 02-21-2021 at 10:28 AM. Reason: Lousy typing
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  #30  
Old 02-21-2021, 11:37 AM
walker172 walker172 is offline
 
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The trailing edges need to be aligned. Not the horns.
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