Twist in the elevators

[Battson]

I have noticed something funny while fine tuning the rigging - the kitset elevators have some twist from left to right. Both the horisontal stabilisers are near enough to dead level, assuming the plane is sitting level. There is some optical illusion here because of the twisted elevators. See the attached photo. The horn balances on both the elevators both align perfectly with the horisontal stabilisers - but of course this can be easily adjusted using the threaded clevis end on the horisontal stabiliser strut. Determining if there's sympathetic twist in the alignment of the horisontal stabiliser is proving difficult, given the profiled ribs. I am concerned that this twist in the elevators is going to create a rolling moment. It's not going to be as large a moment as the ailerons will provide, given it's so close to the roll axis, but still - it might give a heavy wing feeling and it will certainly stress the elevator's interconnecting bolts more than necessary (and possibly more than they were designed to endure over their life). Has anyone else experienced this problem? Does anyone have any bright ideas, which ideally dont involve cutting & welding and re-covering...?

[fly_n_low]

I had a slight twist in mine. I corrected it at the junction where the two halves bolt together but it probably wouldn't have created any issue to begin with. Some elevators have some twist built in to keep an air load on them in the neutral position (level with the stab). At this point I'd just fly it. If it bugs you then you can always pull it apart at annual and tinker with it.

Regards,

Ted

[Battson]

Some elevators have some twist built in to keep an air load on them in the neutral position (level with the stab).

Very relevant point.
I wouldn't put it past Bob to have done it on purpose. Engineers like Bob never cease to impress me.
Although on balance I think it's probably just a manufacturing tolerance thing.

[Mark Goldberg]

Jonathan, I asked Bob Barrows to look at your picture. He told me that it would cause you no problem structurally at all. He said it was possible that you might have to hold a little aileron one direction to compensate, but more likely you wouldn't even notice because it was so minor. He said it was something easily resolved before covering, but a little harder now. He said to fly your plane and then see if it something that you want to deal with. I bet you won't notice it. Mark

[Battson]

Upon reflection, I did have to trim the ailerons in the opposite direction.
This has probably cost me just a little airspeed.
If anyone else has this problem they may wish to consider straightening them slightly.

[Dan R.]

Welcome to steel construction. Its amazing how much a weld will pull things out of alinement as it cools and shrinks. The bigger the weld the more it pulls. IF, you would want to fix it in the future, just take the elevators off and backup the elevator horns bolt holes and cable attach holes with a piece of brass and weld the holes closed and re-aline the elevators and drill new holes and reinstall. Even a little slop in the bolt holes will cause the elevators to be out of alinement. I had the same problem with my scratch built elevators. It will be easier to weld with Tig without getting things to hot.

[Gerhard Rieger]

Hi there, I bought a airframe that someone started, but never finished. I fitted the horizontal stabilizer and elevator. When I measure from the firewall to the tip of the left horizontal stabilazer andthe same on the right I have an one inch differance. Will this have an aerodinamic affect . I will ad some pics

[alaskabearhawk]

I think you would have to determine where the 1in difference is. It can be a combination of a lot of areas. You have the old-style trim tabs I see.

[Gerhard Rieger]

the error is at the horisontal stabilizer attach points, it is out of alignment by about 1/4 inch, it is already welded and if it doesnt pose any aerodinamic problems I do not want to reheat the area again with more welding. The fuse is straight with no twist and this is the only problem I see

[Tyler]

Just curious if anyone has a fix for the twisted elevator issue. My kit elevators have this issue about the same as in the photo originally posted by Battson. About 1 degree difference in deflection. I’m early in the kit build of my model 5 and would love to correct this now. Seems like it’s going to cost some airspeed if not.

[Sir Newton]

If you can not simply bend it straight. Use a hacksaw to make relief cuts as necessary. Weld it back up and forget about it. Very simple to fix. Imho

[Battson]

I would bend it straight, its such a small difference. I cannot risk it now the fabric is on, the fabric would probably go slack in places.

[davzLSA]

You could clamp it down to a nice flat table and heat up the areas that need straightened while they are clamped down to the nice flat table. And don't loosen the clamps until it is cool to the touch. I've used that trick a couple of times and it seems to work.

[Tyler]

Thanks! Yep I gave it a twist and got it straight.