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Elevator leading edge rubbing

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danceskater

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As we were finishing up the empennage kit we noticed that when the elevators were in the full up position (30 degrees) that the elevator leading edge tends to rub slightly against the rib rivets in the aft spar of the horizontal stabilizer. It appears to be most noticable if the "rolled" leading edge is not perfectily round. We are beginning to think that we should have used a smaller pipe to roll the skins in order to get more bend closer to the forward spar in the elevator. However it may be too late now. We have made sure that there are no rough points on the rivet heads and, baring any adverse problems, are going to live with it. Anybody else noticing this? Comments?
 
Mine rubs too. I'm going to drill the rivets and re-roll with a smaller pipe before final rigging. It won't take too much effort to make the adjustment.

Phil
 
Update

We did back out the rod ends by a half turn, but I am not particularily happy with this idea since we have already drilled the holes in the horns and the bearing in the center of the elevators is fixed. I would think that backing out the rod ends might cause binding. A half turn made most of the rubbing go away, but not all. I have the read the thread that talks about one and a half turns before you reach the end of the rivnut, but really did not want to go that far for the aforementioned reason - binding.
 
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I guess normal sequence is to set rod ends for clearance before drilling the center or you'll induce binding like you said.
 
I just had to deal with this on my Rocket. A light whack on each rivet head with a hammer will take care of it. In fact I found that if the LE is not symmetrical it can be easily taken care of with careful use of a rubber mallet.
 
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rubbing

take your fingers and press real hard on the spot where it rubs and slightly massage the contour of the leading edge till it stops rubbing.. it only needs a mm of clearence. it worked for me. :p
 
Update

We did run the 30/25 degree check with the HS on the workbench and the elevator attached and it did not rub or we did not notice it. Not sure why it did not rub then but did after putting the tail completely together. Probably did not speak to it kindly the second time. That was a tough day.
 
danceskater said:
We did back out the rod ends by a half turn, but I am not particularily happy with this idea since we have already drilled the holes in the horns and the bearing in the center of the elevators is fixed. I would think that backing out the rod ends might cause binding. A half turn made most of the rubbing go away, but not all. I have the read the thread that talks about one and a half turns before you reach the end of the rivnut, but really did not want to go that far for the aforementioned reason - binding.
Click to expand...

If the -10 is similar to the two seaters at the center bearing - a small shim could be added under the center bearing bracket flanges to move the entire hinge line back a fraction with no binding.
 
Rubbing

Well, we thought about a shim under the center bearing bracket, but, having already drilled the horns, that approach only brings things into alignment in a fore and aft direction, i.e., with the elevator in the nuetral position. As you get into large elevator up or down conditions the corrections in the rod ends and the correction by shimming the center bearing bracket do not work in the same direction.

This concern about binding all may be an over reaction. The threads on the rod ends are 24 to the inch, so even a full turn of the rod ends are only about 40 thousands, less than a 1/16 of an inch. My half turn was less than a 32nd. Probably no where near that necessary to cause binding.
 
I just test installed the right elevator. I set the rod ends at the maximum 7/8" as per the plans. The leading edge of the elevator is very close to the spar but does not rub, however the inboard trailing portion of the HS skin hits the elevator at about 27 degrees up. No problem reaching max deflection on the down elevator. I know that is within limits, but I am planning to do regular competition aerobatics and wish to have as much control authority as I can get. I could trim the HS skin slightly for about 8" or so along the inboard area, but I guess the best solution is a longer rod end as per RVMike?
 
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mine rubs also....how much is enough clearance?

I found this out when a bird left a big pile right in the gap, which then dried.
When i moved the elev. to full up during preflight....IT STUCK!
I also found that snow and ice collecting in there makes a nasty sound when you move the elevator up and down.
Unless you live in florida, or some dirt-free area, I would not be looking for "just enough clearance so it doesn't rub the paint". I think is should be designed with at least an 1/8" clearance, like most of the other control gaps, so that with the unavoidable contaminants that WILL collect in there, you will not lose elevator function.
.. and no, as I am not a builder, I did not disassemble my HS and replace the rod ends or lengthen them, but I ain't real happy about it...just living with it. :(
 
Same problem...

I had the exact same problem and I had also already drilled the center bearing. I backed out the rod end bearing one half turn and squeezed the middle rivet on the outside rib a little more. That fixed it and I don't have any binding problems on the middle bearing.

Michael-
 
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