How to fix ripped-out rear arch rivnuts?

[mph]

Hello folks,

I may have clipped a cone on the last track day of the year, before winter lay up 😬 So now I'm fixing my self-induced mess.

The rivnuts were ripped out, and the resultant holes are a bit of a mess. I'd like to 'flatten' the side skin again — which I'm guessing means removing the cockpit side panel. Which is riveted in. I'm a bit of a garage noob, and although I've done plenty of things to my Cat over the last three years of ownership, removing rivets isn't one of them.

My questions then are:

1) is it best to remove the inner skin to tidy up those holes, before putting replacement fittings in (I'm going with some rubber 'well nuts' + nylon bolts; to prevent any future repeat mishaps with track day line choices!)

2) does one have to drill out the existing rivets to remove that skin, or are there 'better' ways of removing rivets? I fear making a total hash of drilling out rivets…

Any and all tips and tricks most welcome, thanks!

--Mark

[Jonathan Kay]

6 minutes ago, mph said:

Any and all tips and tricks most welcome, thanks!

I don't know how to fix that skin.

But many of use nylon bolts to attach wings in the hope that they will fail first and cheaply. And IIRC some deliberately weaken the nylon bolt further. 

Jonathan

[mph]

I did find an old topic discussing just that @Jonathan Kay, which is why I've gone down that route 😊

I'd just like to sort out my horrible holes. Oo er.

[OldAndrewE]

Drilling out the rivets should be straightforward.  Use a sharp 4 mm drill until the head comes off and then, if necessary, use a parallel punch to knock the rest of the rivet into the tube. The only problem that might occur is if the pop rivet 'nail' is still showing in the rivet head.  This will stop the drill centring so use a smaller parallel punch to knock it back

[jonsymons]

Mark, I heard of someone who did the same on a bank a while back...

Probably not 'right' for the purists, but I just gently tapped (with a small hammer) the oversize hole back as far as I felt sensible then fitted a larger rivnut matched to the size of hole in the skin - and the process of fitting the rivnut gives a bit of purchase to straighten things out as well. I didn't bother to remove the inner cockpit liner. Ok, so the external skin was a little less than perfect but it all pulled back into line when I refitted the wing and the inner flange on the wing hid the marks. Depends, I suppose if you want perfection or the memory of a great day and a bit of scarring to prove it?!

[kart]

As above, you don't need to drill out inner panels unless you're going for perfection.

In fact if you're going down the Rawlnut route as per the below, then they need a bigger (10mm?) hole anyway and are more tolerant of wonkiness.

 

[SLR No.77]

For info this is what it looks like behind the interior panel, but most likely without the Waxoyl.  

A couple of the rivnuts are behind the main side panel not just the rear quadrant making them more awkward to get to … unless you start a major refurb like I did!

Stu.

 

[Gridgway]

I have done this and I removed enough rivets to get the panel off behind (sharp drills, care and patience are required as described, but it's not a had thing to do).  Then I could get a dolly inside and a nice curved face hammed on the outside.  New rivnuts and I was good to go.

Take care with re-riveting as the rivet gun can slip and scratch as it breaks the rivet mandrel off.  I often cheat as I have an air riveter which is so easy!

[graearea]

19 hours ago, OldAndrewE said:

Drilling out the rivets should be straightforward.  Use a sharp 4 mm drill until the head comes off and then, if necessary, use a parallel punch to knock the rest of the rivet into the tube. The only problem that might occur is if the pop rivet 'nail' is still showing in the rivet head.  This will stop the drill centring so use a smaller parallel punch to knock it back

be REALLY careful doing this. you're basically hammering an aluminium sheet. I managed to bend my scuttle around the holes before I realised what I was doing. drilling rivets with the centre still in is a right PITA

[OldAndrewE]

8 minutes ago, graearea said:

be REALLY careful doing this. you're basically hammering an aluminium sheet. I managed to bend my scuttle around the holes before I realised what I was doing. drilling rivets with the centre still in is a right PITA

My advice is for rivets that are into a steel tube.  In the situation you mention I would certainly not try to hammer the rivets through, I would use pincers or similar on the back to pull the remains of the rivet out

[graearea]

a friend has suggested just making new holes and re-rivnutting. is this an insane idea? I have the opposite problem to @mph in that my rivnuts are corroded and spinning. drilling steel bolts out of ali rivnuts is not going to be much fun.

Edited February 17 by graearea

[mph]

On 16/02/2024 at 13:07, OldAndrewE said:

Drilling out the rivets should be straightforward.  Use a sharp 4 mm drill until the head comes off and then, if necessary, use a parallel punch to knock the rest of the rivet into the tube. The only problem that might occur is if the pop rivet 'nail' is still showing in the rivet head.  This will stop the drill centring so use a smaller parallel punch to knock it back

You were spot on @OldAndrewE, thank you!

 

[SLR No.77]

8 hours ago, graearea said:

a friend has suggested just making new holes and re-rivnutting. is this an insane idea? I have the opposite problem to @mph in that my rivnuts are corroded and spinning. drilling steel bolts out of ali rivnuts is not going to be much fun.

The panels are jig pre-drilled so when you renew a panel all the pre-drilled holes line up with the existing holes in the chassis. Drilling them in new places would work but wouldn’t be a great idea.

[StevehS3]

If it was just one requiring refitting, could it be bonded back in with such as Araldite metal repair putty? It is seriously strong stuff. It can be drilled and tapped like metal.