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AB4-6 rivets losing their buttons (SB 14-12-06)

olegusan

Member
While attaching flaperon?s pushrods I found that all of the AB4-6 rivets used in the SERVICE BULLETIN 14-12-06 lost their buttons.

The rivets used to attach F-1206J Angles to the F-1206A Bulkhead.

All 6 buttons were recovered from the bottom of the fuselage.

Is it normal?
Shall I replace them with the longer and possibly stronger rivets

IMG_3327.jpg


DSCF5261-300x225.jpg


Happy New Year!
Oleg
 
While attaching flaperon’s pushrods I found that all of the AB4-6 rivets used in the SERVICE BULLETIN 14-12-06 lost their buttons.

The rivets used to attach F-1206J Angles to the F-1206A Bulkhead.

All 6 buttons were recovered from the bottom of the fuselage.

Is it normal?
Shall I replace them with the longer and possibly stronger rivets

IMG_3327.jpg


DSCF5261-300x225.jpg


Happy New Year!
Oleg

No it is not normal.
I think there is a possibility that the wrong grip length rivets were used.
I don't have plans to look at but I think when the new style bracket gets installed LP4-4 rivets are specified.
What you are seeing would be common if LP4-3 rivets were used.
 
Hi
Thank you for your reply.

Yes, the rivet next to the button is the LP4-3. I put it in the picture just for dimension reference.

The AB4-6 is MUCH longer. It is about 13mm long (0.525")
I do have two more of them.

The rivet's grip is 8-9.5mm. The thickness of the joint parts is about 8.5mm

Here is another photo from a different angle:
It looks like the shop head has normal size. So it cant be an LP4-X rivet installed by mistake. Longest LP4 rivet is LP4-5 and it is quite a bit shorter than AB4-6.
IMG_3358-Edit.jpg


It seems that the size of the rivet and its grip is correct for the application.
That and the fact that all six of them behaved the same way almost looks like a normal behaviour of this particular rivet.

I wonder if anyone else observed the same effect after having the SB completed.
 
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I'm glad I found this thread the other night.. I just finished building this piece and noticed your call out for AB4-6.. I didn't remember using AB4-6's .. if anything, I think I just used LP4-4's like all the others in this area..

I took a look again when I got to the hangar today.. it was hard to tell which I used.. so I drilled one out and set an AB4-6.. the manufactured head was clearly larger than the LP4-5s... and looks a little different too. So I drilled and replaced all 6 that should be AB4-6's.

That said, I think the AB4-6's are at the maximum of their grip length. For people that prime all their parts (me), I estimate I have an additional 0.008" of material to account for. I think I'm still within spec.. but that shop head doesn't seem like it has a lot of meat on it.

LP45vsAB46.png
 
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