Thanks Joe.
I put a picture out on tinypic.com, and added the link below. Let me know if you have a problem viewing the photo, and I'll email it to you. I do apologize for the quality of the pic. Except for the size of the hole, it really doesn?t look that bad in real life. Below is a little more detail and the options that I?ve come up with.
http://i48.tinypic.com/14tvpn4.jpg
After drilling out a poorly set rivet (which had enlarged the hole slightly), I?m left with insufficient edge distance for the last hole in the flange that connects the bulkhead to the bottom skin AND side skin. Except for the edge distance issue, an enlarged hole could be fixed with an ?oop?s rivet, or go up to a #4. There is plenty of edge distance on the skins, so a #4 or ?oops? rivet will still work there. But even new, the bulkhead flange has insufficient edge distance for an 1/8? rivet, so replacing the bulkhead with a new one would still leave me with an edge distance issue in the new bulkhead?unless I replaced the two skins as well.
The options that are coming to mind are?.
Option 1: (the repair route)
a. Remove just enough of the f-707 (bulkhead) flange to remove the enlarged hole
b. Install a #3 rivet in the remaining bulkhead flange, connecting it to the bottom skin only (with proper edge distance, of course)
c. install an ?oops? rivet or #4 rivet in the original hole, connecting the bottom skin to the side skin ONLY, and
d. fabricate/install a scab flange for a single bulkhead/bottom skin/side skin intersection rivet, placing the scab flange on the aft side of the bulkhead
...and perhaps
e. add another #3 rivet just forward of the ?oops? rivet listed in ?c? above
Option 2 (go the ?replacement part? route )
a. new bulkhead, new bottom skin, new side skin, new stiffeners, etc?
To say that I REALLY (really, really, really?) don?t want to go with option 2 would be an understatement. It would require disassembling center section from the tailcone, and pretty much disassembling/rebuilding the tailcone.
Option 1 would shift the bulkhead/bottom skin/side skin intersection approximately 5/8? aft, but would maintain a bottom skin/side skin rivet at the original location, and would even add two additional #3 rivets (one on the trimmed bulkhead flange and one just forward of the enlarged hole)?.and of course would be the less expensive than option 2, both in time and dollars.
I am not an engineer, so I am unsure of the exact positive/negative impacts to the airframe created by option #1 above. Also, I?ve been lucky enough so far that I have not had to create a scab flange, so I?m unsure whether a scab flange for a single rivet position is even something that would pass inspection, how many rivets would be needed to mate the scab flange to the bulkhead, etc. I have been reviewing repair techniques in AC43.13, but still not sure whether option 1 above would be structurally sufficient (and pass inspection)
Input/options will be appreciated
David