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rivet mistake in aft bulkhead

Moondog

Well Known Member
This type of mistake I’ve made more than once. Very frustrating since it was truly avoidable. If I try to drill out the bad rivet with an angle drill, it will not be pretty. A tailwheel is not under consideration, so would it be ok to replace the rivet with an AN3-xA bolt? Here is the deal----

The F-711 bulkhead has two near-vertical bars, each is riveted in place by the factory (QB) except for the bottom hole which was left open to allow for a tailwheel. Mine is a -7A, so I needed to install an AN470AD4-7 rivet on each side, but found that getting my hands in either side of this bulkhead was a challenge.

There was no room for the rivet gun on the factory side of the rivet (which is on the aft side of the bulkhead, see photo),

2egcv43.jpg


so I slipped the rivet gun into the space in front of the bulkhead. There was just enough room to reach down and hold the gun steady with the back-rivet attachment over the shop head.

For the factory side, I had taken the threaded bolt and lock nut off a DRDT-2. Then inserted a squeezer cup into the end of the bolt. I slipped the nut/bolt/cup into a hole drilled near the end of a half-inch thick steel bar (about 6” long x 2” wide). This gave me just enough weight and leverage to hold against the factory head of the rivet.

It worked perfectly. Brilliant. Followed by stupid.

Picked up the (wrong!) rivet off my workbench. Repeated the procedure but it didn’t feel right. Looked at the factory head, it was properly seated, but the shop head was too short. Apparently, I picked up a 4-4 rivet from the tray sitting next to the 4-7 tray by mistake.

Now what? Drilling out the rivet will be difficult. I know the hole will enlarge if I do. Should I replace with a bolt?
 
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Try drilling as careful as you can. Maybe you will get lucky and drill out the rivet without issue. If you end up getting the hole to big, you can then go with a bolt if necessary.

Just drill carefully and slowly, then replace with a fresh 4-7 rivet.
 
Drilling a rivet out, looks easy. Have you done the HS service buliton yet? now that is a little dificult. Just kiding, look up the drilling out a rivet thread, I think Dan or Scott wrote it ? :D
 
Drilling a rivet out, looks easy. Have you done the HS service buliton yet? now that is a little dificult. Just kiding, look up the drilling out a rivet thread, I think Dan or Scott wrote it ? :D

Bret, I found the post by Scott (rvbuilder2002), very good. Thanks.

Thanks Chad. If I can't use the angle drill with confidence, I'll just remove the back. It's attached by maybe just 4 rivets right now.
 
As alternative to the AN3x bolt, a AN470-5x or 6x rivet may be the solution you are looking for. Aircraft Spruce sells them as well as many other locations.
 
For my QB kit, I pulled that bulkhead out where I had plenty of access. It's a bit challenging, but doable. Had to twist/lift/pull in various combinations.
 
reassess

Can you shear the shop head off with a chisel and punch it back?

The head is firmly seated, would be difficult with limited ability to move my hands in that space.

Talked to Paul M at Experimental Aero who gave me several good suggestions including a guide for the angle drill bit and also a modified Harbor Frt 2.99 punch. His mod to the punch is on his website here. Very good ideas.

Van's said if the factory head is properly seated (it is) and the shop head completely engages the hole (it does) to leave it and build on. That's good news, but if I don't fix it, I will never fly without thinking about that rivet.

Going to the hangar today to reassess. Since the most aft bulkhead is attached only by 4-6 rivets right now, I think I will remove the bulkhead, that will provide me with a lot of room to drill out the rivet without the need for an angle drill.
 
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