Redrill ribs or replace

A

aalexander

New member
I'm in the process of recovering my ECA. Upon stripping the fabric off the wings, I discovered that in a previous recover the fabric on one wing had been attatched with steel pop-rivets. WHy, I don't know, but the steel rivets a a real pain to drill out without damaging the hole in the rib. As a result I managed to wallow out quite a few of the holes in the ribs before I discovered a better method of removing the old ribs. Anyway, my question is this: On the ribs with one or more holes that are now too large for the correct aluminum pop rivets, is it acceptable to re-drill new holes of the correct size, keeping the same number of rivets in the rib and equal spacing ? I'm hoping of course not to have to replace too many ribs.

Incidentally, if anyone finds themselves faced with having to remove steel rivets in aluminum, a pair of good quality flush end nippers works quite well. http://www.amazon.com/Pack-ENP6C-END-NIPPER-PLIER/dp/B000690RO4 Make sure you get a pair that are ground so the cutting edge is flush (or grind then yourself if you have the patience) If they're nice and sharp, you can work them under the head of the rivet and snip it off with no damage to the rib THen the rivet shank will pop out of the rib with a very light tap from a punch. (most come out with just a push with the punch) It works so well, that I'd use it to remove the rivets form the wing that had the correct aluminum rivets, if I hadn't already drilled all of those out.
 
The short answer is yes. I too am in the process of recovering my Citabria. The service manual states that it is acceptable to redrill holes in the ribs at least 1/2" away from the old hole. I would suggest covering up the old hole with some type of opaque covering, (I'm using aluminum tape) so that the old hole will not be visible when it comes time to put the pop rivets through the fabric.
 
Not sure I'd use the aluminum tape... It's gonna be a different alloy than the ribs, it will be in there a long time, there's adhesive that will break down... Add some moisture and electrolytes (salt air if you're near the ocean, like me) and anything can happen.

When I recovered, some of my rib holes were pretty wallered out. (Tech term my supervising mech used. Never did find it in 43-13.) To ally my fears, he had me test the new rivets in a few nasty wallered out holes and... they expanded plenty and held fine. End of worries.

There were some ugly holes that I didn't plan to use, and which might have cut into the fabric. These I tapped flat with a little hammer, then dusted off with a flat file. Done, ready to cover. Completely invisible after covering.

Hope this helps! -Alex
 
Back when they did the testing to certify the pops, they found that a #26 hole was as big as you could go before you lost fastener strength. So, there is a little room for 'wallering.'
 
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