First of all, what a great site.

I cleco'd my 650 rudder together last weekend. While drilling rivet holes into one of the ribs, my drill hit a nearby cleco and bunged up the hole--it came out a little elliptical.

If this happens, should I be unconcerned? Or should I drill out the A4 hole and put in an A5?

I am also curious if there should be an .040 shim between the rib flange and the spar, for the rivets that go between (not through, hope I'm clear here) the two .040 doublers.


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Patrick, small imperfections will be filled by the rivet when it expands.
Otherwise, you should replace the rivet, yes.

As for shimming, you can use up to a limit (which I forget). I don't recall exactly how the rudder goes together, but you probably can add shims if you want - if it isn't in the plans, it's not necessary.

All this stuff is addressed in AC 43.13:
Also, good references:

There is also a document called "zenair construction standards draft 1-07", which I downloaded from the Zenair web site - but I can't find it anymore. If you want it, let me know and I'll email it to you.

Good luck...
Thank you, Carlos. I found the Construction Standards doc on my Zenith CD. There is a table which gives max acceptable hole diameters for 1/8" and 5/32" rivets, 3.5mm and 4.4mm respectively for .016 sheet, so I will check the hole and if it's bigger than 3.5mm in any direction I'll drill it for an A5.

As an aside, I'm amazed at the mix-and-match units in scratch building. Sheet metal thicknesses in decimal inches, rivet sizes in fractional inches, lengths in millimeters, etc. Heh!

And no, there is no shim in the plans so I won't worry about it. Thanks for the help!

Hi Patrick

Without seeing a pic of how elongated the hole is, it is a bit hard to say. Having said that, one only rivet near the trailing edge of the rudder should be ok. As Carlos said, the rivet, to a degree, will fill the hole so I wouldn't be to concerned. Think how strong you rudder would with this rivet missing completely. It wouldn't make any difference to the structure at all. If the strength of our airframes was compromised through the failure of one rivet, I don't think that anyone would ever leave the ground. Maybe when you do your other control surfaces the use of a wood dowel drill stop is a good idea. We all make mistakes Patrick so don't sweat it mate.



dear friend,


i bump into this website from FAA, 


AC 43.13 ,  is this the correct book for young builder like me to read and go through? i am building a ch750 for this 2011. please advise. thanks

AC 43.13 is a LOT of reading, my paper copy is about two inches thick. However, it is a wonderful reference for building, repairing and maintaining any aircraft, certified or experimental. You can learn a lot just reading through it, but it makes a wonderful reference when you wonder how much edge distance is needed, what are the standards for a properly set rivit, how to use the AN and MS aircraft hardware nomenclature, etc etc.


If you want a paper copy, EAA sells them and the profit goes to a good group. If you just want it available, the downloaded version works well and costs nothing. Enjoy!

Patrick:  only one bad rivet!  I should get you to build my 750!  Don't sweat it. Have fun!  brian


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