bertschb

bertschb

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I'm at the point in my RV-14 fuselage build where I've connected the control rods and I'm adjusting the up/down elevator travel. The up/down travel on the left elevator is 27/27. The right is 29/25. How is that possible??? I've measured it every way I can think of and it's always the same. The elevators are bolted solid to the elevator horn so they don't move at all in relation to each other. They move as one unit up and down.

The max elevator control deflection limit for the RV-14 is 30 up and 25 down so I'm satisfied with the travel on the right elevator but not the left. I've stared at this thing for an hour trying to figure out how the travel can be different left to right and can't figure it out. I probably should have paid more attention to my math teacher in high school. Can somebody explain what I'm missing?
 
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bertschb said:
I'm at the point in my RV-14 fuselage build where I've connected the control rods and I'm adjusting the up/down elevator travel. The up/down travel on the left elevator is 27/27. The right is 29/25. How is that possible??? I've measured it every way I can think of and it's always the same. The elevators are bolted solid to the elevator horn so they don't move at all in relation to each other. They move as one unit up and down.

The max elevator control deflection limit for the RV-14 is 30 up and 25 down so I'm satisfied with the travel on the right elevator but not the left. I've stared at this thing for an hour trying to figure out how the travel can be different left to right and can't figure it out. I probably should have paid more attention to my math teacher in high school. Can somebody explain what I'm missing?
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Wish I had an answer for you. Your post made me realize that I've only measured travel on my -9 on the left elevator. Heading to the hangar. I will be watching this post closely. Good luck
danny
 
bertschb said:
I'm at the point in my RV-14 fuselage build where I've connected the control rods and I'm adjusting the up/down elevator travel. The up/down travel on the left elevator is 27/27. The right is 29/25. How is that possible??? I've measured it every way I can think of and it's always the same. The elevators are bolted solid to the elevator horn so they don't move at all in relation to each other. They move as one unit up and down.

The max elevator control deflection limit for the RV-14 is 30 up and 25 down so I'm satisfied with the travel on the right elevator but not the left. I've stared at this thing for an hour trying to figure out how the travel can be different left to right and can't figure it out. I probably should have paid more attention to my math teacher in high school. Can somebody explain what I'm missing?
Click to expand...

The deflection measurements you've got are both 54 degrees of travel from top to bottom. Is it possible that the trailing edges aren't even with each other? For example, if the left side is at zero and the right side is 2 degrees up when you start you would get those numbers, depending on if you're measuring actual level from the horizon or just relative motion from the neutral point.
 
bertschb said:
I'm at the point in my RV-14 fuselage build where I've connected the control rods and I'm adjusting the up/down elevator travel. The up/down travel on the left elevator is 27/27. The right is 29/25. How is that possible??? I've measured it every way I can think of and it's always the same. The elevators are bolted solid to the elevator horn so they don't move at all in relation to each other. They move as one unit up and down.

The max elevator control deflection limit for the RV-14 is 30 up and 25 down so I'm satisfied with the travel on the right elevator but not the left. I've stared at this thing for an hour trying to figure out how the travel can be different left to right and can't figure it out. I probably should have paid more attention to my math teacher in high school. Can somebody explain what I'm missing?
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You probably have some twist in one or both elevators. Very easy to happen, even if the trailing edge is itself straight. Take the rudder off so that you can stretch a fish line from the outboard trailing edge to outboard trailing edge of each elevator to see if that's the case. Probably not a big deal, regardless.
 
Desert Rat said:
The deflection measurements you've got are both 54 degrees of travel from top to bottom.
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I zero the level when I switch sides so shouldn't they both go up/down the same amount? This is the part that is driving me crazy. Even if one elevator was 6" higher than the other, if you zero the level, shouldn't they both go up and down the same amount?
 
It’s common on other models to have to file the elevator up & down stops individually for each elevator horn to get proper & equal deflections.
 
alpinelakespilot2000 said:
You probably have some twist in one or both elevators. Very easy to happen, even if the trailing edge is itself straight. Take the rudder off so that you can stretch a fish line from the outboard trailing edge to outboard trailing edge of each elevator to see if that's the case.
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I just strung a line along the trailing edges of the elevators (actually did this several months ago before I drilled the hole in the elevator horn) and although they are aren't "laser level", they are pretty close.

I have measured from the outside, middle and inside edges of both elevators. I've measured from the forward, center and aft sections of each elevator. I zero the level when I switch sides. No matter how I measure it, the left elevator goes up and down roughly 27/27. Right is 29/25.

If I had twist in an elevator, it seems it would change the reading from one part of that one elevator to another part. For example, if there was twist I could understand seeing 27/27 on the outboard side and 29/25 on the inboard side - of the same elevator.
 
The elevators are simply not level in the neutral position. The right is 2° higher. You can weld up the hole in the left horn and re-drill it to match the right one in the neutral position.

You "probably" used the balance horns to set the neutral position. This will rarely come out right.
 
Ralph Inkster said:
It’s common on other models to have to file the elevator up & down stops individually for each elevator horn to get proper & equal deflections.
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If the elevators are bolted to the elevator horn and push rod, how would filing the stops individually help to adjust the elevators so they go up/down the same? For example, my right elevator horn touches the "up" (rear) stop first when moving to the "up" position. The left elevator horn never touches the up (rear) stop.
 
Mel said:
The elevators are simply not level in the neutral position. The right is 2° higher.
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I still don't understand. Even if the right elevator was 2 degrees higher, if I zero the level, why would it move up 29 degrees when the left only moves up 27 degrees (again, after zeroing the level)?

I clamped the trailing edges of the elevators together before drilling the hole in the elevator horn.
 
bertschb said:
I still don't understand. Even if the right elevator was 2 degrees higher, if I zero the level, why would it move up 29 degrees when the left only moves up 27 degrees (again, after zeroing the level)?

I clamped the trailing edges of the elevators together before drilling the hole in the elevator horn.
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If the elevators are level at neutral, as you say, then why would you need to re-zero the level? They will both read "0".
 
Are you turning you level around between measuring each side? If that is the case, it sounds like your level needs calibrating.

Otherwise, the only other thing I can think of is, You have defied physics!
 
I think I understand what is going on now. It also explains why I would have flunked engineering school in the first semester...

The leading edges of my elevators are not both flush with the HS. Remember, I clamped the trailing edges when I drilled the horn. While measuring I have been setting the neutral position with the HS on the left side then zeroing the level. Fine so far. But, when I switch to the right side I also was re-setting the neutral position with the HS then re-zeroing the level. It made sense at the time but I see now the starting points between left and right are not the same.

Soooooo, I split the difference on the "neutral position" (one leading edge is below the HS, the other is above) and THEN zero'd the level. Measured both left and right and of course they are same. In this case, 28.2 up and 26 down - which splits the difference I was measuring before. I expected 28/26 but close enough. Of course, 26 degrees down is too much so now I have to deal with that somehow.

I'm REALLY sorry for wasting your time here folks. I so appreciate each of you taking the time to help me. Sometimes I wonder if I should just sit around and watch Gillian's Island re-runs rather than build an airplane. I'm pretty good at the former, pretty bad sometimes at the latter.
 
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So are your two elevators not in-line with each other laterally? Because if so, then this is still a problem...you'll introduce a roll moment to the aircraft.
 
RV7A Flyer said:
So are your two elevators not in-line with each other laterally?
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The trailing edges of the elevators are aligned. The problem is when the elevator is in the "neutral" position, one counterbalance arm is above the HS and the other is below it. I chose this option when drilling the hole in the elevator horn rather than having the trailing edges mis-aligned.
 
That still sounds like a problem to me...the chord lines of the two elevators are not identical. Or one of them is twisted. Either way, they're not identical and they should be. Or the horizontal stabilizer itself is twisted.
 
I've run a long straight edge against the top of the HS and the elevators. All points I checked are straight/flush. I think the counterbalance arms are not "true". I can't imagine this would have much affect on airflow or aircraft handling.
 
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bertschb said:
I'm REALLY sorry for wasting your time here folks. I so appreciate each of you taking the time to help me. Sometimes I wonder if I should just sit around and watch Gillian's Island re-runs rather than build an airplane. I'm pretty good at the former, pretty bad sometimes at the latter.
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No apology necessary. Something like that can be a real "can't see the forest for the trees" kind of thing when you're standing there looking at it. Glad you're getting it sorted.
 
bertschb said:
I've run a long straight edge against the top of the HS and the elevators. They are all straight. I think the counterbalance arms are what are twisted. Since they are only 2" wide, I can't imagine they would have much affect on airflow or aircraft handling.
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Seen this misalignment many, many times, even on my own airplane. It has to be off a great deal before you will notice in flight.
 
Just so you guys know what I've done to check for "alignment". I placed a straight edge across the areas shown below in red. All surfaces were flatter than a pancake. Somehow the arms are not aligned with each other.

elevator.png
 
FireMedic_2009 said:
So are you saying your counter balance arm on the right was misaligned with the elevator when you built it?
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I can't think of any other scenario. I didn't damage the elevators by dropping them. Didn't notice there was a problem until I was setting them up to drill the elevator horn.
 
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Mel said:
Seen this misalignment many, many times, even on my own airplane. It has to be off a great deal before you will notice in flight.
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That may be, but it's not something I would accept. Everyone has their own standards, though, I guess...
 
RV7A Flyer said:
That may be, but it's not something I would accept. Everyone has their own standards, though, I guess...
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I didn't say I would necessarily accept. I"m simply saying that it doesn't affect flying characteristics unless it is greatly out of rig.
 
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RV7A Flyer said:
That may be, but it's not something I would accept. Everyone has their own standards, though, I guess...
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So you would rebuild the elevators just because the leading edges of the counterbalance arms sits 3/16" above/below the HS?

If you look at post #21, you'll see all the other control surfaces are flat. Believe me, it really bothers me that the counterbalance arms aren't perfect. I didn't expect that when I was getting ready to drill the elevator horn. But, I didn't enjoy building the elevators and I'm not trying to build an award winning show plane so I'm begrudgingly accepting what I have.
 
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bertschb said:
So you would rebuild the elevators just because the leading edges of the counterbalance arms sits 3/16" above/below the HS?

If you look at post #21, you'll see all the other control surfaces are flat. Believe me, it really bothers me that the counterbalance arms aren't perfect. I didn't expect that when I was getting ready to drill the elevator horn. But, I didn't enjoy building the elevators and I'm not trying to build an award winning show plane so I'm begrudgingly accepting what I have.
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Yes, or try to figure out what is causing that and drill out some rivets, adjust things, and re-rivet. Something didn't go right during the build...these are prepunched parts, after all, it should be pretty difficult to get 1/4" out of alignment.
 
RV7A Flyer said:
Yes, or try to figure out what is causing that and drill out some rivets, adjust things, and re-rivet. Something didn't go right during the build...these are prepunched parts, after all, it should be pretty difficult to get 1/4" out of alignment.
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I would need to remove the outside ribs (counterbalance arms) which would also involve removing the skins. High likelihood of creating much more serious problems. I would build new elevators from scratch before I would try to disassemble and rebuild these. Believe it or not, I am a perfectionist. But I also know my limitations as a new builder. I don't like leaving things as they are but I feel it's a much better choice than the alternative.

My GPS antenna will introduce more drag than the tiny amount of material on the leading edge of the counterbalance arms that will sit above the HS.
 
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bertschb said:
My GPS antenna will introduce more drag than the tiny amount of material on the leading edge of the counterbalance arms that will sit above the HS.
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Nothing to do with your issue directly, but ... Not sure about the RV-14s since they have a different airfoil than the earlier single seat and two seat RVs (excluding the -12), but the earlier RVs have a little bit of down elevator designed in at cruise, leading to the mass balance horns sitting slightly above the HS.

Per "rvbuilder2002" (Scott M) in Post #2 of the first thread linked below:

"... and a very slight amount of down elevator was specifically designed in by the designer (Van) and considered desirable. The slight down elevator improves pitch stability at the cost of a very slight amount of drag."​

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My previous RV-8 has a bit of down elevator as shown by the mass balance horns sticking up a bit in the photo below. My current RV-8 also does.

i-HRF2XJr-L.jpg
 
I see almost exactly the same thing on my -7A, maybe a bit less, but it's there. Interesting...thanks for the info!
 
RV8JD said:
Nothing to do with your issue directly, but ... Not sure about the RV-14s since they have a different airfoil than the earlier single seat and two seat RVs (excluding the -12), but the earlier RVs have a little bit of down elevator designed in at cruise, leading to the mass balance horns sitting slightly above the HS.

Per "rvbuilder2002" (Scott M) in Post #2 of the first thread linked below:

"... and a very slight amount of down elevator was specifically designed in by the designer (Van) and considered desirable. The slight down elevator improves pitch stability at the cost of a very slight amount of drag."​

​
​
​


My previous RV-8 has a bit of down elevator as shown by the mass balance horns sticking up a bit in the photo below. My current RV-8 also does.

i-HRF2XJr-L.jpg
Click to expand...

The 14 is the same.
 
I built an old school RV-4 and now RV-7. I don't know about RV-14, but it is very possible to have mismatch. On the old kits (RV-3/4/6) you had to lay out and drill holes. For the the elevator horns needed to be drilled. It was possible to also have some TWIST in the elevator itself (again no pre punch). So sometimes you had a bit of mismatch. Mine was slightly out. I pulled the elevator. I was able to take the mis-match put but opening up the hole where push pull attached, weld repaired with bushing moved the hole just a bit so it matched perfect. The plane flew the same.
 
RV8JD said:
Nothing to do with your issue directly, but ... Not sure about the RV-14s since they have a different airfoil than the earlier single seat and two seat RVs (excluding the -12), but the earlier RVs have a little bit of down elevator designed in at cruise, leading to the mass balance horns sitting slightly above the HS.
Click to expand...
My 14A is the same way, in cruise and the faster I go the more pronounce this is.
 
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