Roof oil canning

[79vette]

So I realize I probably should have asked her before doing anything, but I didn't and now I need to fix my mistakes.

I have an 88 square body with some rust in the outer roof skin due to leaking cab clearance lights. I cut the rusty sections out and fit patch panels as tight as I could. They tacked up fine but after welding the first one up (largest one on the driver side) I now have pretty bad oil canning in the driver side of the roof. I tried to go slow and move around, but apparently it wasn't enough. Since this truck has a 2 piece roof with an inner skin it is not possible to planish the welds since there is no access from the inside.

My question is what should I do at this point, and how should have I approached this repair in the first place? I do not have a stud welder, and I even if I did I'm not a body guy and I suspect I would just make things worse.

I'm assuming the welds shrinking have pulled the panel causing the oil can. If I cut out the patch, hopefully it will relieve the stress and the roof will return to its previous shape and I'll be back where I started with a slightly bigger hole.

Is it possible for an amateur to weld patches like this with a mig and not have it oil can? Or is the roof too flat and unsupported for it to work without being able to planish the welds? If welding isn't going to work can I cut out the patches, make new ones, and put it together with panel adhesive? Once I make new patches I could cut another piece to match the perimeter of the patch with a 0.75" offset on each side and bond it to the bottom of the roof with panel adhesive. Once cured I could bond the patch to that "lip" to achieve a flush repair.

I appreciate any advice you may have

[Grounded63]

You're going to have to make access, to be able to plannish the entire HAZ. A stud welder won't fix this. It will need to be plannish/stretched. Either remove the outer skin, the inner structure, or cut access in the inner structure.

It's hard to tell from the pics on my phone. But, it looks like some of the tack welds are kinda cold. Usually your welder should be set up for plug/rosette welds. When tacking in butt welds. Should be a 100% penetration weld. I generally also stitch weld them in, with the same settings. I prefer to continually stitch weld them in, in one direction only. Without jumping around. (Unless something odd is happening) That jumping around trying to keep the area cool ( cooling off the area between welds ) almost always turns in to a **** show. You introduce a lot of randomly spaced unequal stress in a panel that way. Rather than maintaining a uniform amount of heat in the panel, working from one direction only. I also generally prefer to make patch panels with rounded corners. Rather than sharp pointed 90° corners. For me at least, it seems like i get less distortion in the area. Any time you're making a patch in the middle of a panel like that. It's going to distort the most.

[mongocanfly]

I have a similar upcoming situation. I have a body panel I want to weld in..if i cut and weld it in place ,there is no possible way hammer and dolley it ...to do it right would mean me removing a entire body side panel .. the several I've talked to said it's the only way to do it proper..
Not really something I want to do

[Getter-Done]

Before cutting access holes you could try a shrinking disc.

If it works that might save you a little time and heartache.

Link to disc and video of it being used below.

Link to disc: https://www.proshaper.com/product-ca...hrinking-disc/


Link to video:

shrinking disk demo - YouTube

Demonstration on sheetmetal;

Shrinking Disc Magic - YouTube

[79vette]

Originally Posted by Grounded63

You're going to have to make access, to be able to plannish the entire HAZ. A stud welder won't fix this. It will need to be plannish/stretched. Either remove the outer skin, the inner structure, or cut access in the inner structure.
.

I just don't understand how getting access is possible. If you cut an access hole in the inner structure, then you'll have to weld that up later and you'll get the same distortion just on the inner skin

I suppose the only way to do it correctly is to cut out the entire outer roof and spot weld/seam seal on a new one like how the factory built it, and I definitely don't have the time or skill to do that. For this truck it'll have to be a bonded steel patch instead of welded

I uploaded photos showing how it sits now. It's hard to photograph, but there is an obvious dent in the driver side on the far side of the black tape. I'm travelling for work, so I had to spray rattlecan primer on the bare metal and tape over the unwelded seams to keep water out of the cab structure. When I get home next week I'll try to cut the welds and hopefully the panel springs back once the residual stress from welding is removed. If so then I'll try a bonded patch with 3m panel adhesive. I know thats not how they would have done the repair it in the 80s, but the new epoxy adhesives are pretty good and if it lasts a couple decades that'll be enough for me. Maybe I'll be a better welder if/when the glue ever fails...

[79vette]

Originally Posted by Getter-Done

Before cutting access holes you could try a shrinking disc.

If it works that might save you a little time and heartache.

Link to disc and video of it being used below.

Link to disc: https://www.proshaper.com/product-ca...hrinking-disc/


Link to video: shrinking disk demo - YouTube

Demonstration on sheetmetal;

Shrinking Disc Magic - YouTube

I'm travelling currently, but I'll check out those videos when I get home. However, I think the problem is the panel is already shrunk too much. I think it needs to be stretched at the welds and it seems like shrinking would just make it worse. Unless I'm missing something?

[Grounded63]

Being as it's an '88 it has a headliner, doesn't it ? The inner structure doesn't need to be metal finished necessarily. Since it will not be visible.