I bought a biplane from a guy at the fly field a couple of years ago. I stripped all the old covering and sanded everything down. I had to completely rebuild the ailerons because they were in bad shape. I am in the process of pre-fitting all the control horns and radio equipment before I start to cover. I have come across a problem. I bought standard control horns for the ailerons, cut them down and attached a 2-56 pushrod to each control horn on the ailerons. I adjusted the ailerons to be equal when in neutral position. When the aileron surfaces are up, they move the same distance. When I move the ailerons down, the top aileron travels more than the bottom. This is the case for both sides of the wing. I know I probably mounted the control horns wrong, but I don't know what to do to fix it. I hope it is a simple fix. Please post some pics that would help describe the solution. Here are some of the biplane pics:

You've effectively built in differential. don't worry about it. make sure the wing incidences are correct, and go fly it! (well, don't forget to cover it first :-)

I agree with 2slow. As long as it's not much more than an 1/8th inch di9fference you will not even notice.

Actually the difference is around 3/8". I would think this would be unacceptable. What would you recommend?

Ok If I am understanding you Make sure that from the center of the servo to where you attached the push rod are the same distance same from were the ailerons are hinged to were the push rod connects to the control horn have to be the same Finally are all of the servo arms at 90 degrees from the servo when in neutral and I think for this to be exact you need the same length pushrods
If you have the capability with you radio It probably would be easiest to run top and bottom ailerons on separate channels and adjust the servo travel limits accordingly Hope this helps

Hellcat,

I don't understand your explanation. Can you post a sketch?

By the way, servos for the top wing probably is not an option. I want to keep the weight down.

Bullseye

Yep, 3/8th inch is a bit much. Looking closer at your pics, try moving the bottom control horn in towards the leading edge of the aileron, maybe 1/8th inch. That should lower the amount of throw to the top aileron

Sorry, I have no pics of this plane to provide to you

Here are a couple of the diagrams I made for a thread I started on the .40 size Ultimate biplane from World Models. They had hardware in the ARF for coupling the ailerons top-to-bottom. The left hand picture shows what resulted with their rigging. The top aileron was moving much less than the bottom. Shown in the diagram is the result of their rigging. What's amazing is that you actually get a different difference when the coupled ailerons are moving UP!! So when you move your ailerons, one side was seeing different lift/drag than the other side!!

The second pix shows how to connect the ailerons so that they will all operate exactly the same. It's dead simple to do and took me less time than it would have taken had I used the kluged up hardware that was included.

There have been a number of postings about how the small Ultimates were somewhat twitchy. Some guys complained that their little bipes had to be landed somewhat fast and very carefully, that they tended to snap into the ground if they were brought in too slowly. And there have been a couple of posts that said their little Ultimates had a tendency to snap out of slow rolls and other such.

I noticed the rigging setup WM had in their ARF as I was starting to assemble it, and figured right away that it didn't look right. So I rigged up a simple experiment. If you do a search on these forums, you'll see my findings and a BUNCH of words describing the whole deal.

Bottom line is that with the rigging setup you're looking at, you'll get different moving ailerons on the side that're going up, and different moving ailerons on the side that's going down, and there will ALSO be a difference between the differences side-to-side. No lie......

My little Ultimate flies like a dream. Last time out, I "hovered" it down in a mild headwind to an almost zero-forward-speed landing. I've yet to have it snap out of any maneuver. It's an awesome flying airplane.

Close enough very often isn't good enough. Heck, it's often not worth spit. Why settle for "it only works lousy a little bit" when you can have it work perfectly? and with less work.

BTW, Bullseye,
With your model and the existing connections, you can leave the lower existing work as it is. Simply take the upper horns and move 'em onto the top of the ailerons and you're going to have a very good rigging setup.

The stagger of the wings causes some of the problem, but provides part of that solution. After you've moved the top horn to the top of that aileron, plug in a connector wire and see if it doesn't make a right angle at both connections. That's what you're after.

Darock,

Thank you so much for all the information. That is exactly what I was looking for! I will try and fix the control horns this weekend and let you know how it all worked out.

You know, I tried asking the local hobby shop about a solution for this problem, but could not get an answer from the old-timers. Thanks again Darock!!!

Bullseye