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Adjusting Rib Flanges

RV701775

Active Member
I had some trouble getting the rudder skin to fit around the R-912 counter balance rib. This required me to make quite a few adjustments to the flanges to get them to 90 degrees. I was probably a bit of a perfectionist and made a dozen minor adjustments fore and aft. It now fits perfectly, but it is it possible that I damaged the rib along the bend where these adjustments were made from over adjustment?
 
Yep. I had the exact same problem. Had to trim a lot off the forward flange but eventually got it to fit. I also wasn't sure if this was bit too tight of a fit.
 
R-912 Skin Fit

I was never able to get this to fit. I measured the distance between the two holes on the rib flange and on the skin and they were off by about 3/64ths of an inch off, so no matter how much I remove, it does not look like it will fit. This resulted in highly elongated holes when drilled.

I am on attempt two and same result. Any ideas? I would prefer not to have to use 1/8th or oops rivets here.

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Using fluting pliers to align rivet holes

My suggestion is to first get the rib flange rivet holes aligned with the use of "fluting" pliers. Then gently adjust the flanges to 90 degrees. The fluting pliers crimp the flanges which allow the individual flanges to curve. I don't have a flexible metal straight-edge to check alignment with. I use a reasonably straight strip of stable white oak maybe 1/16" thick by 3/4" by 20" that bends easily. I'm satisfied if all the rib flange holes line up within half their diameter--about .050." Then I gently adjust the flanges to approximately 90 degrees. With the flanges creased/fluted, they seem to be flexible enough to adjust the last little bit if needed when being attach to the skin.

Just my two cents. I've gotten the empennage kit completed and working on the wing outboard leading edges. I'm pleased with the wing's top skin attachment between the main and rear spars. Good luck. Oh by the way, when adjusting ribs as described, it seems the ribs naturally lay flat on a surface which I really don't worry about. Hope this helps.
 
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