Elevators' trailing edge alignment

Mounted the elevators to the horizontal stabilizer this afternoon preparing to mount the fiberglass elevator and stab tips (Emp pages 11-02 and 12-06).

When the elevator counterbalance arms are lined up with the horz stab the trailing edges of the elevators are out of alignment by 3/8" (rechecked after firming things up and using a laser level) with each other; the right elevator is down. Everything that needs to be in alignment on the HS and each elevator independently are 'perfect'; the leading edges of the whole HS in alignment, the top and bottom skin surfaces of the HS front and rear spars each side in alignment. The elevator horns are out of alignment by 1/4"+/-.



This misalignment made me think that I may have done something wrong along the way but I can't find anything I may have messed up. I would have expected near perfect alignment of the trailing edges or at most 3/32" misalignment but I can see this from across the hangar.

I can't imagine there is any adjustment for this and that the driver for alignment is to make the elevator counterbalance arms true to each HS side and live with the up/down elevator trailing edge misalignment and the elevator horns will be off but not as apparent unless you look close. I assume that this is more a cosmetic issue more than an aerodynamic one (or is it potentially an aerodynamic problem?). I don't like it much.

My question for the rest of the 14er's is whether they experienced the same problem, and is 5/16" misalignment too far from a reasonably acceptable tolerance for alignment to expect from the new 14's integrated CAD/CAM manufacturing? Just order the wing kit and I hope there aren't similar issues with any alignment problems with those, anything there would likely be an aerodynamic problem.

First, I'd check to make sure the problem isn't due to a warped trim tab. I had to scrap one of mine due to twist.

If that's not it, maybe you'd want to see which elevator is the major problem by removing it, then clamping the LE down and measuring the twist along the TE.

(Also a possibility that some of the twist is in the stabilizer)

If it's just one of the elevators, you might consider re-doing it, or I've heard that removing the rivets along the spar will enable you to straighten things out and then re-rivet with the elevator clamped down straight.

I would imagine that since most of the time the airplane flies with the elevators NOT in the neutral position due to loading, etc. compensating for the twist by allowing the counterbalance arm to protrude 1/16 or so into the flow may not be a huge deal.

Be interesting to hear what Van's has to say.....

Jerry #140158

Horns

Not sure if the 14 is like the others but I seem to remember posts about the horns sometimes not being perfect.
http://www.vansairforce.com/community/showthread.php?t=97098

Horn Misalignment

Page 11-03 step 7, read the note.

Your misalignment is discussed there.

Pretty sure what you're seeing is quite common and perhaps acceptable to leave as-is and move on however you may be headed down the wrong path.... Think about it... In flight, will it be more important that the counterbalance arms be aligned with the H Stab, or that the two elevators aligned with one another? It is common for the horns to be mis aligned and the hole in the elevator horns is drilled much later during fit up of the tail feathers. When I drilled the horns, clamped both elevators to a single 10' straight edge and ignored the counterbalance arms (which are about 5/16" different from each other, but my elevator is never aligned with the H stab so I'm the only one who knows this. Flies pretty straight though!

jeffw@sc47 said:

Mounted the elevators to the horizontal stabilizer this afternoon preparing to mount the fiberglass elevator and stab tips (Emp pages 11-02 and 12-06).

When the elevator counterbalance arms are lined up with the horz stab the trailing edges of the elevators are out of alignment by 5/16" with each other; the right elevator is down. Everything that needs to be in alignment on the HS and each elevator independently are 'perfect'; the leading edges of the whole HS in alignment, the top and bottom skin surfaces of the HS front and rear spars each side in alignment. The elevator horns are out of alignment by 1/4"+/-.



This misalignment made me think that I may have done something wrong along the way but I can't find anything I may have messed up. I would have expected near perfect alignment of the trailing edges or at most 3/32" misalignment but I can see this from across the hangar.

I can't imagine there is any adjustment for this and that the driver for alignment is to make the elevator counterbalance arms true to each HS side and live with the up/down elevator trailing edge misalignment and the elevator horns will be off but not as apparent unless you look close. I assume that this is more a cosmetic issue more than an aerodynamic one (or is it potentially an aerodynamic problem?). I don't like it much.

My question for the rest of the 14er's is whether they experienced the same problem, and is 5/16" misalignment too far from a reasonably acceptable tolerance for alignment to expect from the new 14's integrated CAD/CAM manufacturing? Just order the wing kit and I hope there aren't similar issues with any alignment problems with those, anything there would likely be an aerodynamic problem.

Click to expand...

Jeff,
Your photo is a bit confusing.
Your post mentions the elevator trailing edges not being aligned but your photo shows the elevator control horns not aligned. As already posted by others, if your concern is the horn misalignment, it is common and is accounted for when drilling the attach hole for the push rod.

The pic of the horns is in there immediately after the sentence that states that the horns are not in alignment when the counterbalance arms are in alignment with the HS.

here's pic of alum channel clipped to the right elev trailing edge (assembly is bottom side up on bench) and spanning across to the left elev trim tab, gap is between bottom side of trim tab (up in pic).



And, I checked for twist in the elevators separately, the HS, and the trim tab => no twist in any of those and the straightedness of all the elev trailing edges, the LE edge of the HS, and the trim tab are straight with no more than 1/16" gentle curvature along the right elevator but both ends in alignment. >> rethought this and think that it may be better to align the two elevator trailing edges and let the couterbalance arms fall where they may, it may be that if the elev trailing edges were not in the same plane (left side higher than the right side) that it would cause the plane to bank to the left; and the slight in level flight the slight extension of part of the counter balance arms poking into the windstream would be minimal.

Still, 3/8" misalignment is way beyond what I consider an acceptable tolerance. Talked with Carl Bell (C-J) today and one of their elevator's had a slight twist in them and the inboard trailing edges did not line up with each other by about 3/16" with the counterbalance arms set with the HS ends (much less of a misalignment).

Not sure if the 14 is like the 7...but I built two sets of elevators as I found my first set was badly warped. My first elevators were built when the counterbalance arms were not prepunched. Even with the second set of elevators....and being extra careful during all aspects, I still am not "dead on" after drilling the control horn. To get any further improvement, I'd have to weld up the control horn on one side and try again.

I've measured friends flying RV's and have found their elevators to be slightly off too......so I'm leaving mine alone for now and moving forward with the canopy phase.

Humble Pie

Sitting here and trying to decide where to begin on a big slice of humble pie . . .

I put the truck in gear thinking I was in first and popped the clutch - the gear box was in reverse.

Based on discussion with Carl Bell (C-J) I bought two 8' lengths of 1 1/2" x 1/8" alum angles and clamped one to the top and one to the bottom of the trailing edges spanning at least 40" or so onto each elevator. By golly my first impression of the misalignment (3/8") was not there anymore. They were near perfect in-alignment and the counterbalance arms were each within 1/32" in alignment with the HS ends. The elevator horns are still misaligned by about 5/16" but that should not be a problem, I'll split the difference in the positioning of the hole to be drilled through them for the control tube push rod end.

My apologies for getting a bit nasally disjointed over what at first appeared to be something wrong with the kit and starting an unnecessary discussion. I promise to do a more-better analysis next time when something doesn't look right and to not make any accusatory comments.

No problem Jeff....

Building an airplane is just one learning experience after another, from beginning to end.