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Elevator Asymmetry

mgregory176

mgregory176

Active Member
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I am just starting the Emp attach portion of the build and noticed that when my elevators are in the trailing position with the counterbalance arms fixed to the ends of the HS I have almost a 1/4" differential between the trailing edges of the left and right elevator.

If I even up the trailing edges my right counterbalance arm is about 1/4"low on the end of the HS.

What are the acceptable tolerances and the possible fixes?

Thanks,

-Mike
 
My friends' RV-10 has about 1/4" to 3/8" differential on the elevator. It flies just fine, and has about 300 hours on it now.

Keep on building, and whenever you park the plane, just don't center your elevator and nobody will notice ;)
 
Pics and measuring details, please..

Mike,

How are you measuring this? Are your trim tabs in place on the elevators, and if so, do they line up with each other? As I recall, my counterbalance arms weren't absolutely flush when the elevators were in trail, but I don't think it was such a differential as you describe.

Mike
 
Elevators

Mike, I have the elevators clamped to the HS at the counterbalance arm so the tops of the HS and thw cb arm are even. I am measuring by placing a six foot level across the midpoint of the elevators in front of the trim tabs. The left elevator is high by 1/4 in at that point.

I also ran a plum line across the trailing edge and everything lines up nearly prefect.

So now my question is where is the proper place to measure and do ii have twisted elevator? I have asked an IA friend to come give his opinion as well.
 
I don't recall measuring where you are measuring. If mine was off I have not noticed any problems.

I do recall when elevator control horn bolt was installed I have about 3/32" difference between left and right counterbalance arms. Not worth welding and redrilling control horns and flies great with a little right rudder trim in cruise.

I would take pics of your measurement setup, email then discuss with Tech guys at Van's. I would expect things to have less than 1/8" mis-alignment if following plans and building on a fairly straight workbench.
 
Many RVs exhibit similar asymmetry. In a discussion with the Vans guys one time, I was told that small differences in the L & R elevator positions are "aerodynamically insignificant".
 
As I recall, I had a very slight difference between the two cb arms also. I spoke with Vans and was told that a small variation is acceptable. I followed the procedure for drilling the horn by aligning the trailing edges. It's really not noticeable to any significance .
 
All of our airplanes have similar defects. After asking an expert, the cure is usually to stop looking at it and move on. And if you catch anyone looking at it, hit them with a bucking bar. :D

As a friend of mine once said while we were working on his plane "Hey, we're not building the space shuttle here! Let's move on!"

Otherwise, you'll never finish!

OTOH, I'm not saying to ignore truly important stuff like:
controls that squeak or rub,
engine controls that bind or don't get full travel,
fuel systems not built per plans,
engines or props of dubious origins,
or builders who are too stubborn to use a tech counselor!

Those are the things that will get you hurt. Add: "Use a flight adviser" to the list too!
 
I had the same problem with my elevators and I figured out that the horizontal spar is slightly off where the two pieces join. Try setting a straight edge on your horizontal spar and see if its perfectly straight. Mine was off by about 1/4 of a inch over the whole span. The only thing I could figure out is that the match hole drilling was slightly off. It drove me crazy trying to figure why my elevators didn't line up, as they were both straight.

Mike
 
This is a non problem, build on.

Now, if you want to really make yourself crazy with little details, just wait until you get to setting the elevator trim tabs:eek:
 
Elevators

Thanks for all of the input. Seems that the popular consensus is to build on. After walking away from it for a day and having my IA look at it I feel much better with the situation. I took delivery of the wings Tuesday so there is plenty of work ahead.

Onward and upward!

Mike- I want to bend those trim tabs over my knee, maybe after it's flying i'll forget what a pain they were and readdress then!
 
mgregory176 said:
Mike- I want to bend those trim tabs over my knee, maybe after it's flying i'll forget what a pain they were and readdress then!
Click to expand...

Dont let them bother you for even a second.

They look like major monkey motion from the rear, but from the left front seat you will never know.

I have never actually measured things, but I suspect total of the travel used in normal operations is about a half inch, and it is around the center of the total travel. It is at the ends of the travel where the motion gets weird, not the center.

Lots of prior discussion on this, if you feel like some entertaining reading. Search the RV 10 forum for trim tab.
 
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