I ran into a problem today when I went to match drill the control horns for my elevators. When I clamp the elevator counterweights flush with the horizontal stab (both top and bottom) and measure the angles of both elevators they are .5 degree off from each other. I'm hesitant to drill them this way. I had to shim the left elevator counterwieght rib down .063" (which effectively moved the trailing edge of the elevator up) to make it match the right side. The best that I can figure is that one of the elevators was built by the previous owner with a slight twist. Is this a big deal? Should I clamp the outboard ribs flush with the horizontal and drill or offset the left side to match the right and drill. Thanks for your input.
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Match drilling elevator control horns
- Thread starter db9469
- Start date
JonJay
Well Known Member
Let's identify what is going on first. Clamp your elevators as you have done, take a straight edge long enough to go across the trailing edge of both elevators and tell us what you see.
A slight twist in control surfaces, ailerons, elevators, etc... is not un-common, nor is it that big of a deal.
The other area to check is the hinge bracket alignment as they are not matched drilled in the 6. All of the hinge brackets should align through both right and left sides. This can be checked with a line or laser with the elevators off.
A slight twist in control surfaces, ailerons, elevators, etc... is not un-common, nor is it that big of a deal.
The other area to check is the hinge bracket alignment as they are not matched drilled in the 6. All of the hinge brackets should align through both right and left sides. This can be checked with a line or laser with the elevators off.
Last edited:
Dbro172
Well Known Member
My initial test fit showed that when one counterbalance was flush with the H-stab, the other was about a 1/4" different. Naturally I freaked out! Come to find this is pretty common. Mine was due to a twist built into the elevator (yup, built exactly per plan, dont know what i would do different to not duplicate it).
From research and advice I got, I do recall that aligning both counterweights was NOT the answer; it was more important to align both trailing edges and let the counterweights do there own thing.
I did clamp both trailing edges to a long steel angle straight edge, which helped in bringing the control horns closer to alignment and the counterweights closer to alignment.
It is possible to have perfectly straight trailing edges but still have a twist. You can measure for twist by running some fishing line diagonally from corner to corner and measure for a crown or dip.
I will drill my control horns when i am mounting the tail feathers to the plane, which will include clamping the trailing edges of both elevators to a straight edge first.
From research and advice I got, I do recall that aligning both counterweights was NOT the answer; it was more important to align both trailing edges and let the counterweights do there own thing.
I did clamp both trailing edges to a long steel angle straight edge, which helped in bringing the control horns closer to alignment and the counterweights closer to alignment.
It is possible to have perfectly straight trailing edges but still have a twist. You can measure for twist by running some fishing line diagonally from corner to corner and measure for a crown or dip.
I will drill my control horns when i am mounting the tail feathers to the plane, which will include clamping the trailing edges of both elevators to a straight edge first.
