Hi all, when i built the tailfeathers on my LT-25, I noticed that the back of my horizontal stab and the front of my elevator don't run quite parallel. Luckily, though they're not hinged yet. At first I thought surely I built the horizontal stab wrong, but when I got out my trusty metal straight-edge, the stab was very nearly straight, and the elevator definately curved away from the straightedge when I held one edge of it flat against the straight-edge.

My first instinct is to just sand the elevator until it's straight, but the only problem is that the elevator piece comes to a point, it's not flat on the face that's slightly curved.

Is it better to sand it straight, and just give up the pretty V shape, or should I just leave the elevator alone and hinge it as-is? The over-all curve is probably between 1/16 and 1/8".

-Rick

Hey Rick,

I'm going to assume you mean the gaps are at the edges (about 1/16 - 1/8"). Personally, I wouldn't worry about this on a trainer; the only thing you need to watch is the hinges. If you have pinned hinges, they might bind at the edges because the gaps. You could move to CA hinges and that would help elevate your problem. A pic might help.

1/16" gap is perfectly acceptable for a control surface on a trainer (Most people use the width of a "T" pin as a guide. Soooo.... my recommendation. just go ahead and mount it with the CA hinges (if they are CA hinges). Put a T-pin through the center of each hinge. Get them all lined up and ready for the CA. Then, working from one side, drop the CA on to the hinge when there is the t-pin width gap. Move on to the next hinge. Do the same there, and keep going. This way, there will be a very slight difference in tension accross the CA hinges on the control surface, but it will essentially be pulled straight by the hinges (CA Hinges will deal with this just fine).

If you feel uncomfortable with the pressure that the elevator will put on the hinges, then just mount it equally uneven (so that the closest part to the stab is at the center of the elevator. If the gaps at the outside of the elevator is much more than 1/8", then have a look into "sealing" hinge gaps.

gus

Hey Rick, I am gonna assume you mean that the front surfaces where the elevator and stab are to be joined are the problem. If this is so I would suggest you make a new elevator. It is probably a piece of solid wood around the 1/4" size. Just go to your local hobby shop and buy a piece of appropriate wood and using your hobby knife and a straight edge. Cut a new one and rebevel the front. To fix the problem would be more hassle than it is worth. If you sand it flat it will no longer be the same size end to end. Or if you sand it straight you will not have enough elevator area. Just make a new one. There is no hurry. When you are done and flying it you will be glad you did. Good luck on your project.

Mark Shuman