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  #1  
Old 03-04-2006, 07:42 PM
mikehoover's Avatar
mikehoover mikehoover is offline
 
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Posts: 626
Default Elevators not evenly aligned

Just drilled my elevator horns and am preparing to mount the HS/Elevators on the fuse hopefully within the next week. I noticed that the left elevator seems to be about 3/8"-1/2" lower than the right one at the trailing edge; really noticeable when I clamp a long piece of angle on the trailing edge of the right elevator and it hangs over the top of the left elevator. The elevator counterbalances are clamped to the HS so they are in proper position even with the HS. Has anyone had this happen? How can they be off this much, or is this typical? Thanks!

Mike
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www.aclog.com/rv-9a/
www.eaa242.org/
N194MH first flight on 08-26-12
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  #2  
Old 03-04-2006, 08:10 PM
N24YW N24YW is offline
 
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Location: Burlington Iowq
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I believe that you have the same problem that most RV have. My horns didnt line up well either but I aligned the trailing edges before drilling the hole for the control rod eye. If the problem you described is what I think you are saying dont worry about it most RV have the same problem. For the elevator stops on mine one horn hits the stop in the up position and one horn hits the stop in the down postion. I dont recall the exact amount of travel but that is determined after the horizontle is attached to the fueslage. Sorry about the spelling hope this will ease your mind.
Jim

I actually welded the holes shut that I drilled the first time and redrilled them to get it a little closer. Not sure I would recomend welding for everyone but it worked for me.
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  #3  
Old 03-04-2006, 08:17 PM
szicree szicree is offline
 
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If I understand correctly, you're saying that the front counterbalances are lined up, but the trailing edges are not (or vice-versa too, I guess). I would think that twisted elevators are the most likely explanation. You could lay the elevator on a known flat surface and check this. If it's just the control horns that are a little out of sync with each other I wouldn't worry about it.
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  #4  
Old 03-05-2006, 08:31 AM
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db1yg db1yg is offline
 
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Default Elevator Alignment

I had a similar situation, although not to the same degree.

I was advised by Van's and others to insure the elevator surfaces are aligned--even if the counterweights are slightly out of alignment. The logic was that, given the large surface area of the elevators they will have a much greater influence on the flight characteristics of the aircraft than does a counterweight sticking up (or down) slightly. If the rudder is not yet installed you can easily check this by first aligning the trailing edges of the elevators (not clamping the counterweights) and then sighting across the top surfaces of both elevators from one end to insure alignment.

Good Luck and Cheers,

db
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  #5  
Old 03-05-2006, 09:46 AM
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Missaligned elevators will induce a roll moment which must be conteracted by an aileron input. Now you have 4 control surfaces not in trail, thereby creating drag. If your elevators are missaligned as much as you say, you should correct the problem now.
Mel...DAR
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  #6  
Old 03-05-2006, 02:03 PM
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Build9A Build9A is offline
 
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Default are the pushrod holes drilled?

The elevator horns are often mis-aligned. Instructions say to line up the trailing edges on a table (not a direct quote..check the manual). If you have already drilled the holes that you bolt the pushrod to, you may have a problem. The instructions and the drawings both assume the horns will be misaligned slightly. Mine are offset, but the trailing edges are even. If you have already drilled both horns, and your trailing edges are offset, I'd call Vans tech support and see what they say you should do next.
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  #7  
Old 03-05-2006, 02:51 PM
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mikehoover mikehoover is offline
 
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Quote:
Originally Posted by Build9A
Instructions say to line up the trailing edges on a table (not a direct quote..check the manual).
I wish they did! The manual (page 8-15) says to align the elevator counterbalances with the stabilizer tips and clamp them. Then on to drilling the horns. This is perhaps another of Vans' booby-traps. A mention that the trailing edge alignment takes priority over counterbalances being even with stabilizer tips would have been helpful here.

As it is, if I clamp a length of aluminum angle along both trailing edges to line them up, the left counterbalance is about 3/8" low if the right one is clamped to the HS tip. If the left is clamped, the the right one is 5/8" above the HS tip. So which configuration would be thought of as having the elevators in neutral, or in trail?

Regardless, I have the horns drilled, so I might have to weld patch one hole in the forward-most horn, and redo that hole with the TEs aligned. The aft-most horn's hole will still be okay.

Will be contacting Vans tomorrow. Thanks for all the replies!
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  #8  
Old 03-05-2006, 02:54 PM
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godspeed godspeed is offline
 
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Location: Corpus Christi,Texas
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Default twist in elevator

Per vans, (mine were off about 3/4 inch) line up the
trailing edge and drill the horns, then see which elevator looks out of alignment, and lock the good side in trail with the horiz stab and drill out the
end rib in the counter balance area and massage
the end rib on the bad side, you may see where the next rib is pulling the rivets and skin, (thats how far the twist goes) the direction you need it to
be in trail (reduce the 1/2 inch) you should be able
to work most of it out.. you will have to use some blind rivets to fix it, but most of it will be in the end rib and you can get solid rivets with the sqeezer.

I ended up with about 3/8
vans said, you won't know it during flight, many rv's have this problem, (we all start on the emp) also he said only you will know it so at the fly in's or when you go somewhere other might see it, just tie the
stick back with the seat belt so they are not aligned
and no one will ever know build on..


Danny..
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  #9  
Old 03-05-2006, 07:03 PM
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REHughes REHughes is offline
 
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Location: Polson MT (8S1)
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Default Elevator Alignment

Some aircraft purposely misalign the elevator trailing edges in order to eliminate any 'dead-band' effects in the pitch control system (I believe that the Kitfox calls out a 3/8" differential). At least one of the surfaces will always be in 'clean air' by rigging in this fashion.

The resultant differential elevator roll effect is minimal at such close inboard stations. I would guess that most applications stipulate that the left elevator be rigged higher if an engine with American-style prop rotation is used, to theoretically counter any roll-due-to-slipstream effects on the tail group, but I'll bet that any effects of misalignment in the range of 3/8" would be impossible to measure.

Regards,
Hawkeye Hughes
Skyote, RV-3's
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  #10  
Old 03-05-2006, 07:26 PM
tin man tin man is offline
 
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Location: northern california
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Quote:
Originally Posted by REHughes
Some aircraft purposely misalign the elevator trailing edges in order to eliminate any 'dead-band' effects in the pitch control system (I believe that the Kitfox calls out a 3/8" differential). At least one of the surfaces will always be in 'clean air' by rigging in this fashion.

The resultant differential elevator roll effect is minimal at such close inboard stations. I would guess that most applications stipulate that the left elevator be rigged higher if an engine with American-style prop rotation is used, to theoretically counter any roll-due-to-slipstream effects on the tail group, but I'll bet that any effects of misalignment in the range of 3/8" would be impossible to measure.

Regards,
Hawkeye Hughes
Skyote, RV-3's
When Kitfox's start cruising at 200 mph they will probably change that setup. FWIW when I make small trim adj in my RV3 there is a slight but noticable roll input.

Tom
RV3
2000+ hours
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