Elevator horn to spar alignment

[MTBehnke]

I'm working on the right elevator and am hoping one of you can help me out.

Van's instructions state to align the tube portion of the elevator horn with the centerline of the elevator spar. If I cleco the horn to the spars using the existing holes, the centerline of the tube angles slightly and is about 3/64" offset from the centerline of the spar.

If I try to align the centerline of both pieces, I'll end up with figure-eight holes in the spar. Is it more important to just get the tube and spar aligned, even if they are off-center a bit, or should the centerlines of both pieces also align?

Any suggestions?

Thanks,
Mike Behnke
RV-9A Empennage
Andover, MN

 

[N722SH]

Elevator horn-to-spar alignment

Mike,

I ended up with the same figure-8 shaped holes in one of my spars when I drilled the horn lined up with the centerline of the spar. What I did was make two little "backup plates" that were match drilled to the holes on each side of the horn. These two backup plates go over the figure-8 shaped holes in the spar. When you rivet it all together you have the horn-spar-backup plate stacked together. I figured the backup plates would reinforce the figure-8 shaped holes and prevent the rivets from getting pulled through the 8-shaped holes. I made the backup plates from some left over elevator/rudder stiffener material and used the next size longer rivets.

Scott Harding
Sugar Land, TX
-9 about to start wings

 

[jcoloccia]

Mike,

I ended up with the same figure-8 shaped holes in one of my spars when I drilled the horn lined up with the centerline of the spar. What I did was make two little "backup plates" that were match drilled to the holes on each side of the horn. These two backup plates go over the figure-8 shaped holes in the spar. When you rivet it all together you have the horn-spar-backup plate stacked together. I figured the backup plates would reinforce the figure-8 shaped holes and prevent the rivets from getting pulled through the 8-shaped holes. I made the backup plates from some left over elevator/rudder stiffener material and used the next size longer rivets.

Scott Harding
Sugar Land, TX
-9 about to start wings

This doesn't sound structurally sound, although it probably doesn't really matter in this case. The way to do it would have been to put a doubler (the "backup plate") on the back side of the spar and rivet the plate to the spar. Then rivet the horn through the spar and the doubler. You have to anchor the doubler somewhere other than the elongated holes.

 

[alpinelakespilot2000]

Call Van's before you do anything...

I believe the instructions re: aligning with the centerline of the spar is part of an old set of instructions. Apparently (from builders who came before me) Van's used to send everything except the weldment undrilled. Now (at least on my kit) everything is prepunched so I just had to align the holes in the weldment with the holes in the inboard rib and spar. Even if the centerline is off a little, I don't think the exact alignment is critical, but you do want both elevator weldments to match each other as closely as possible. Mine turned out just fine using the holes Van's provided. Don't quote me on the above--I'm going from my memory.

Again, before you go making figure-8 holes, I'd check with Van's. You'll make enough figure-8's accidently that there's no reason to do it intentionally!

 

[MTBehnke]

Per Bruce at Van's:

"We should fix the manual. Since both the elevator spar and the weldment are pre-punched, you can disregard the statement about aligning the tube, Just use the holes that are already in the parts."

Thanks all for the input,
Mike