Aileron Counterbalance

Merry Christmas Everyone. Santa gifted me time in the garage to work on the plane. I'm working on the ailerons and am at the point of dimpling the parts and getting ready for final assembly. My question is related to dimpling/countersinking the counterbalance and leading edge skin. This is what is in the directions:

Disassemble the parts, deburr, dimple and prime as needed. Machine countersink the holes in the counterbalance pipe. The countersink need not be 120° to match that of the rivet heads. The .020” skin and the aluminum blind rivet will deform sufficiently to contour to a 100° countersunk hole

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I'm concerned about trying to dimple the leading edge skin because that would be in the bend and the way i see it would cause a flat spot or damage the skin. Can I assume from this statement that if I countersink the counterbalance pipe only, that dimpling the skin is not necessary and that it will "deform sufficiently" to leave a finished surface?

Aileron skin

bob865 said:

Merry Christmas Everyone. Santa gifted me time in the garage to work on the plane. I'm working on the ailerons and am at the point of dimpling the parts and getting ready for final assembly. My question is related to dimpling/countersinking the counterbalance and leading edge skin. This is what is in the directions:



I'm concerned about trying to dimple the leading edge skin because that would be in the bend and the way i see it would cause a flat spot or damage the skin. Can I assume from this statement that if I countersink the counterbalance pipe only, that dimpling the skin is not necessary and that it will "deform sufficiently" to leave a finished surface?

Click to expand...

If memory serves, I countersinked the pipe. Then I took a 1x2 of hardwood and drilled a hole matching the diameter of the pipe. Cut the wood leaving 1/2 the hole. Rigged a brace and clamp to hold the board. Placed the pipe in the wood cradle and skin over the hole in the pipe then hit the male die over the hole. Dimples came out perfect.

You can use a reduced diameter female die. That works well to produce a minimal “flat spot”
Use an extension in the c frame on the female die side to lift up the skin reduce the flattening out of the nose skin.

Another method is to cleco the skin to countersunk counterbalance and then use male die in an extension in the rivet gun to dimple the skin using the pipe as the female die. Just requires a few taps. I’ve used this method for various hard to get dimples. I strongly recommend practicing this first tho.

I wouldn’t attempt to rivet the undimpled skin to the countersunk pipe.
You could experiment with some scrap pipe if you want and report back, but I’m sure those LP4s aren’t strong enough to “dimple” the skin fully.

I took my male dimple die and held it in place while I tapped it with a hammer.

Thanks for the feedback. I ended up mixing a few suggestions together and here's what I did. Once the counterbalance was countersunk, I cleco'd it in place. With it in place it sat nicely on a piece of 3/4" MDF I had that I cut my bending tools from for the elevator work. This would take the load of the rivet gun instead of the clecos. I then used my male dimple die in my rivet gun attachment and gave it a few hits with the gun. It worked perfectly.

New problem. I think I may have built in a twist. I ran out of time to fully check it out yesterday, but hoping to figure it out today.

Been too long since I looked close at a RV aileron.

I believe the lower surface of the aileron is "flat," if so:

Riveting Procedure to "build out" (instead of "building in") Twist

It's almost the nature of the process to gain a twist. I used the following when I riveted up an outer wing panel, solo.

I cleeco-clamped two 24" pieces of 3/4 x 3/4 aluminum angle to the lower edge of each outer rib. Looked at from the end, some distance back, if there is no twist, the angles will "match" If a twist they will crisscross in an "X".

Sometimes you can introduce some counter-twist (at the beginning, I typically would reverse the twist the same amount the other side of flat) and the aileron will stay put. Other times, they can be difficult and require a friend or your better half to apply counter force to hold the correction "in" until you've shot the next rivet.

Never think that you can correct for twist and finish the aileron without checking. It will "relax" back from the counter twist when you least suspect.

Happy New Year

Marc Bourget said:

Never think that you can correct for twist and finish the aileron without checking. It will "relax" back from the counter twist when you least suspect.

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It's funny you say that. I tried to show my wife last night what I was concerned about and when I put it on the floor, there was almost no twist. The night when I built it, it was noticeable and pronounced. Last night it was very minor and almost un-noticeable.

How is Twist Detected

Adam,

We are not at this step, but are approaching it. You said it was obviously twisted when you did it, but almost imperceptible the next day. How did you recognize the twist? Do you know how it is induced?

Thanks,
Mike

MJarreau said:

Adam,

We are not at this step, but are approaching it. You said it was obviously twisted when you did it, but almost imperceptible the next day. How did you recognize the twist? Do you know how it is induced?

Thanks,
Mike

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When I finished building it and took the last clecos out and laid it on the table it wobbled. Think of a chair with a short leg that rocks on only two legs. The next day when I put it on the floor to show my wife, it laid almost flat. There is still some wobble, but just barely.

I don't know that I should admit this out loud to this community, but I didn't fully read the directions. After I got through the assembly and main info in the direction I just finished putting in the rivets because I thought I knew what was next. Thurns out those last 6 sentences had some useful info. For the bottom closure, I started at one end and worked across because I didn't want pillowing between rivets and I thought that would be the best way to avoid this. I think this pushed the material on the bottom in the opposite of the material on the top causing the twist. I also think I had some clecos still in the top when I was riveting the bottom that may have prevented the aileron from laying flat while I was working that may have also contributed. I hope to start on the left aileron today and fingers crossed for better results now that I've re-read the directions.