edge distance issue options

[JaxRV]

Hello All,

I am new to the forum, and hoping I can draw on the collective experience of the members for input/options for an edge distance issue I?ve run into. As this is my first post, I?m unsure whether this is even the correct sub-forum for this type of post, details, pics, etc?

Basically, the issue is at the intersection of the bottom skin, the side skin, and the last rivet position on the bottom flange of a bulkhead. Plenty of edge distance left on the skins, but not enough on the bulkhead flange.

If someone can let me know the correct forum to post something like this, I can provide more detail, pics, etc (via posting or email)

Thanks,
David

[Joe Parish]

Welcome to VAF David!

Post the details and photos if possible and you will get plenty of feed back generally. As long as it is not specific to a certain RV model you can post it here.

[JaxRV]

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

[Fred.Stucklen]

Put in an 'opps' rivet and don't worry about the bulkhead tab edge clearance...

Originally Posted by JaxRV

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

[Joe Parish]

David how about putting in a doubler plate and tying it into one or two other holes. Just a thought? Give Vans a call or drop them an e-mail and I am sure they will have other options with out replacing all those parts. Good luck.

[JaxRV]

I thought about the doubler option, but did not list it because I thought that without resolving the edge distance issue, a doubler would just conceal an area that would likely crack due to shear stresses placed on the rivet. If/when a crack did occur, it would be hidden until it spread beyond the edge of the doubler.

Again...not an engineer, aeronautical or otherwise, so I'm not sure. It would certainly be easier than the 'option 1' I listed.

[n82rb]

Only one rivet? Bang a rivet in it and build on.......

[bruceh]

I recall a couple of prepunched holes in the fuselage kit that were really close to the edges like that. My opinion? put the oops rivet in and build on!

[rzbill]

I agree with the fellows that have said "Oops it and go on". Think about the failure mode. Worst case is a crack in that tab that goes from edge to the rivet hole where it stops because the rivet hole is a circular stress reliever.

Just for your information, there are a few places you will run into that have edge distance problems by design. You can't do anything about them. One that comes to mind is the steel brackets at the bottom corners of the firewall.

[JaxRV]

Good point, Bill.

I think I'll go w/ an oops rivet and Joe's doubler suggestion, tying it to a couple of adjacent rivets. Even if it cracks and I can't see it right away, the crack SHOULD stop at the problem hole, and with a small doubler there it will decrease the chances of it cracking at all.

It should be fine with this approach...and it's a lot simpler and inexpensive than than the options I originally posted.

THANKS GUYS. I really appreciate the feedback.