Rudder- 917 counter balance rib

[CalKid]

What is the most aft hole for? Dimpled this hole by mistake when I was dimpling counter weight #10 holes. By the way my Cleveland kit did not include #10 dimple dye which the plans call for to match the #10 screws. I used #8 and not quite flush.

[Lorin Dueck]

CalKid -

Sorry, I'm not sure what you're asking.
My drawings show R-917 is a shim.
Can you confirm the part you're asking about?

BTW - My Tech Counselor said it was OK to use a flush set to "undimple" a skin - but you can only do that once.

Good Luck!

Lorin D.
SB 9A, O-320, Tip-Up
Fuse Ordered
N194LD Reserved

[CalKid]

Wondering if that most aft hole is a moisture drain. In that case I could just flatten it out and save the rib.

[JohnR]

Van's told me it was okay to flatten a dimpled hole and redimple one time. I had to inquire because I dimpled a piece the wrong way.

[bullojm1]

I am not 100% familiar with the aft hole on the rib in question, but if it isn't supposed to be mated with another part in that location, it is probably a tooling hole (used to hold the part when it is bent). If the dimple isn't interfering with anything else, LEAVE IT. Any un-dimpling *could* cause a crack.

The rule is typically you can flatten or reverse a dimple ONCE. After that, the aluminum will become too brittle.

Don't cheese out by using a #8 dimple die. You will need the #10 die a few more times in the kit and it is the right tool for the job. The dimple die to get is the #10 screw dimpler from Avery (http://www.averytools.com/p-858-screw-dimplers.aspx). It uses an included screw so you don't need a yoke. Plus its 1/3 of the price of the #10 dimple dies from Cleveland.

[Lorin Dueck]

Mike -
Good point about minimizing any re-work to a part!!
If it's not needed .. and you don't WANT it... then don't do it!
Lorin D.
9A SB
N194LD reserved

[dons]

I think you mean the R-912 counterbalance rib. The two holes on the web when you get the part are both tooling holes, you use the forward one for the forward mounting hole in the weight, and drill another hole for the rear hole in the weight. The most aft hole in the R-912 is not used.

Any water in that cavity would likely drain out a lot easier via the aft corners against the R-902 spar, so flattening the dimple really wouldn't help a lot in the draining of water.

All that to say my vote would be to leave it and move on.