Wear on spar rib angle rivets
 

I'm currently doing the annual inspection on my 10 year old 320hrs TT RV12 and discovered wear on the LP4-3 rivets that connect the inboard rear rib to the left main spar.

See photos:
Angle: https://photos.app.goo.gl/zU1QMEnBDZEkScWN7
Topmost rivet: https://photos.app.goo.gl/eqRnvbvNeLd6fpb89
Second topmost: https://photos.app.goo.gl/zhgvyAcDqmM2hYTV6
Third rivet: https://photos.app.goo.gl/MQmaZEx9aqUADZzVA
Bottom rivet: https://photos.app.goo.gl/BmNR6KJTFoGbwY8f9
End of Left main spar: https://photos.app.goo.gl/wTmkS1xo119vBtUy7

I'm guessing this wear is due to play in the wings. I've performed the MM Rear Spar Doubler check and measure 0.038" movement in the Left wing and 0.026" in the Right wing. I did the check by myself so I'm unsure how accurate that is, but would seem to indicate some movement. The maintenance manual says 0.050" is acceptable with the new ES-00076 & ES00077 Electrical Connectors but 0.010" with the old UHMW ones.

Last year I installed landing and position lights, but removed the UHMW connector and just wired in a molex connector for the lights. Does anyone know why the new electrical connectors increase the play tolerance? Did I introduce this play by removing the UHMW blocks?

Dale,

Have you considered replacing the worn rivets? Won?t fix the wear problem, but at least you will be starting over with full strength rivets.

Rich

Oh yeah I'm certainly going to do that, but I'd prefer they not end up worn again if I can avoid it.

I believe the increased play of .050 vrs. .010 is due to the fact that the new socket design will tolerate more movement before contact is broken. The older method used sets of button head screws that contacted each other. They would easily break contact so that's were the .010 limit comes in. I also replaced those with connector plugs with about 10" of lead wire.

I had the same problem at the root angle. The opening in the side skins was just a bit too small so I enlarged the opening about 1/8" on the side that was rubbing and the wear went away.

The opening in the side skins of the fuselage? How did that help?

Do you have play in your wing spar pin bushings as well ? Is it passing the test with the tool you get with the kit ?

How much wear is there in the lock-pin bushings?

Whoops...the above post beat me to it!

tool in the kit??
 

"Do you have play in your wing spar pin bushings as well ? Is it passing the test with the tool you get with the kit ?"

I bought a project, and can't remember having any tool for measuring the fitting of the wings. Anyone has a pic and/or description of this, please?

Page 3-15 of the current MM has a diagram of the measuring device and its use.

It passed at last annual but I haven't checked it yet this year; I'll follow up here when I do.

Last year I didn't notice the wear on the angle rivets but I was also a new aircraft owner and I've become far more observant as I've gotten to know the plane better.

Question
 

What tool??? I never received any tool like this with my kit. Anyone have a photo??

I'll bet you have it, here's a picture from the MM p.3-15 as previously mentioned by jrtens:

Mine came with the final documentation and placard package.

Checked last weekend: yes, all of the bushings (both those in the spar and those in the fuselage) are within tolerance based on testing using the tool that comes with the kit.

wear of spar rivets
 

It is really hard to be sure what you are looking at in close-up photos but it appears that the worn rivet heads are on the front side of the left wing spar. The left spar slides into the fuselage in front of the right spar, so the wear line on the rivets and the angle seems to have only the possibility of lining up with the edge of the rectangular hole in the side skin of the fuselage. As Bruce mentioned, when I first installed my wings into the fuselage there was a lot of scraping. The precut rectangular holes in the side skins of the fuselage were a touch too small and scraped against the spar. I had to file out a significant amount of material to get the spars to go all the way in. I didn't measure it but I'm thinking maybe 1/16 to 1/8 inch had to be removed. This kind of scraping vibration seems consistent with the wear pattern in your photos.

Unless I have misinterpreted your photos, I don't see any other possibility. I'm a few weeks behind, so hopefully you have already fixed it.