Countersunk the wrong hole in Center Section Bulkhead. How to repair it?

[apivovarov]

Page 20iS/U-06 - Section 20 - Center Section Bulkhead

I accidentally made a countersink in a thick aluminum part (F-01204-1) where it was not required. The affected hole is highlighted in red in the picture below.

In the next section Section 21 this hole is used to attach parts F-01204D-1 and F-01224-L-1 to the thick aluminum part F-01204-1, using a long rivet AN470AD4-9
See: Page 21iS/U-02, Figure 2 – Riveting Baggage Floors.

What is the recommended method to repair or fill in the accidental countersink?

 

[RayJay]

Can you just dimple the mating part to match? I've done that before when countersinking where it wasn't needed.

 

[PhatRV]

Before you attempt to make the repair, contact Vans tech support for guidance.

 

[N8DAV8R]

As already mentioned, it's a good idea to run this by Van's. I would expect that the answer is to either build on and do nothing different with the baggage floors, or to dimple that hole in the corresponding part and use a CS4-4. In any case, probably not anything to panic about.

 

[ravenstar]

I think this hole only matches the F-01224-L-1? Worst case, I suppose you could dimple the corresponding hole on the F-01224-L-1 and install an AN426AD-4-9 rivet. Easily stronger than the original rivet. It might be a challenge to squeeze, though. Or perhaps a Cherrymax CR3212-4-9. Either would look a little different, but be much stronger than the original rivet. Bottom line there are many choices. Unfortunately, once it's countersunk, you can't fill it again.

 

[apivovarov]

Thank you all for the helpful comments and suggestions.

Yes, we contacted Van’s Aircraft as well. They recommended completing the full 100° countersink at the affected hole in the thick aluminum part (F-01204-1) and dimpling the corresponding holes in the sheet metal parts (F-01204D-1 and F-01224-L-1).

Ravenstar, I’d like to clarify the components and the plan for addressing an accidental countersink I made.
- F-01204-1 is the Center Section Assembly. It includes the thick aluminum U-channel that connects to the left and right wings.
- F-01204D-1 is Aft Bulkhead - a sheet metal part that covers the aft side of the U-channel (referenced in Section 20).
- F-01224-L-1 is a sheet metal floor part that attaches to the aft side of the Center Section Assembly (referenced in Section 21).

The hole I highlighted in red (on the attached photo) is intended to receive an AN470AD-4-9 universal-head rivet to secure all three parts together.

My plan is:
- Finish the full 100° countersink in F-01204-1 at the affected hole.
- Dimple F-01204D-1 and F-01224-L-1 at their corresponding holes.
- Use an AN426AD-4-9 countersunk rivet (100°, 2117-T4 aluminum), which is very similar in strength and grip to the originally specified AN470AD-4-9.

Let me know if we're aligned on this and if the proposed solution is structurally sound.

 

[ravenstar]

Thank you all for the helpful comments and suggestions.

Yes, we contacted Van’s Aircraft as well. They recommended completing the full 100° countersink at the affected hole in the thick aluminum part (F-01204-1) and dimpling the corresponding holes in the sheet metal parts (F-01204D-1 and F-01224-L-1).

Ravenstar, I’d like to clarify the components and the plan for addressing an accidental countersink I made.
- F-01204-1 is the Center Section Assembly. It includes the thick aluminum U-channel that connects to the left and right wings.
- F-01204D-1 is Aft Bulkhead - a sheet metal part that covers the aft side of the U-channel (referenced in Section 20).
- F-01224-L-1 is a sheet metal floor part that attaches to the aft side of the Center Section Assembly (referenced in Section 21).

The hole I highlighted in red (on the attached photo) is intended to receive an AN470AD-4-9 universal-head rivet to secure all three parts together.

My plan is:
- Finish the full 100° countersink in F-01204-1 at the affected hole.
- Dimple F-01204D-1 and F-01224-L-1 at their corresponding holes.
- Use an AN426AD-4-9 countersunk rivet (100°, 2117-T4 aluminum), which is very similar in strength and grip to the originally specified AN470AD-4-9.

Let me know if we're aligned on this and if the proposed solution is structurally sound.

Gotcha. I was seeing the F-01204D-1 as part of the center assembly. I recall now assembling it myself. Sounds like Van's recommendation is the same, to use the AN426AD-4-9 after countersinking and dimpling. My understanding is that should be at least as strong as the original rivet, and perhaps a bit stronger due to the countersunk head. Van's, of course has the full engineering analysis, but they approved it so I'd feel very confident this will work.