I have an area in the middle section of my rear quarter that is sunken in and I am trying to figure out how to straighten. It is only about an eighth of an inch. I have replaced a rusty section below the problem and unfortunately welding in the new metal didn't help. The sunken section was the same before I replaced the section. The sunken section has an oil canning effect and can be easily pushed out, but goes right back into the sunken position. Would using a shrinking disk across the area be the right approach? If that is the right approach, would heating up the area with a heat gun and cooling be the same as using a shrinking disk?

Any help is appreciated.
Art

No no no no no! NO shrinking disc! I don't know how this misinformation started, but so many people believe it!
Whenever you WELD, you create heat, and the metal SHRINKS. No, it doesn't matter if you spray the braze with water (as my mentor used to do), or use compressed air on MIG welds, or even use a barrier paste around any weld. The metal shrinks, when enough heat is applied to melt it, even less, as in brazing.
You need to stretch the metal. Precisely, the weld seam. Leave the surrounding metal around it ALONE! Accurate hammer ON dolly is the only way to do this. YES, it is difficult, Yes, it is often not very successful for a beginner. Yes, you need to cut out any inner panel to gain access to the inside of the weld seam, to do it right.
Like being a good painter, it usually takes a lot of experience to get this right. To get the knowledge of how hard to hit, where to hit, where to continue, after doing this for a while. And doing this on a MIG weld is even harder than other welds (gas or TIG), because the weld is harder and more likely to crack when doing this.
I would knock off around 80-90% of the weld proud, and do the same if there is any inside the panel. You do not want too thick a weld to try to stretch, the thicker metal is, the less affect a hammer has on it. Then carefully hammer the weld seam, pretty hard, along the entire seam. Making sure you hit the weld seam, and the dolly is directly behind it. Keep lots of pressure on the dolly, you don't want it bouncing off when the hammer hits it.
After one pass, it should look better. You may have to do more of this, depending on how accurate, and how hard your hits were. |Try to be consistent in both of these. Of course, certain areas may need more attention than others, say, on corners, or if there was more gap, and you had to stay on that area longer to fill it. More heat, more stretching needed!
In the end, it's a difficult task, even for people with some experience. Good luck with it! You might want to weld and practice on a scrap panel first!

I appreciate your response. In my case the sunken section was there before I replaced the panel and had some oil canning. There was work done on the area before I started, so I am assuming the problem occurred during the prior fix. I must say I never considered cutting out the interior section to gain access for hammer and dolly work. I understand why that makes sense. I will follow your advice and hopefully come out with decent results.

Thanks for taking the time to help.
Art

CHOPOLDS EXACLY!!!
Jay D.

chopolds wrote:No no no no no! NO shrinking disc! I don't know how this misinformation started, but so many people believe it!
Whenever you WELD, you create heat, and the metal SHRINKS. No, it doesn't matter if you spray the braze with water (as my mentor used to do), or use compressed air on MIG welds, or even use a barrier paste around any weld. The metal shrinks, when enough heat is applied to melt it, even less, as in brazing.
You need to stretch the metal. Precisely, the weld seam. Leave the surrounding metal around it ALONE! Accurate hammer ON dolly is the only way to do this. YES, it is difficult, Yes, it is often not very successful for a beginner. Yes, you need to cut out any inner panel to gain access to the inside of the weld seam, to do it right.
Like being a good painter, it usually takes a lot of experience to get this right. To get the knowledge of how hard to hit, where to hit, where to continue, after doing this for a while. And doing this on a MIG weld is even harder than other welds (gas or TIG), because the weld is harder and more likely to crack when doing this.
I would knock off around 80-90% of the weld proud, and do the same if there is any inside the panel. You do not want too thick a weld to try to stretch, the thicker metal is, the less affect a hammer has on it. Then carefully hammer the weld seam, pretty hard, along the entire seam. Making sure you hit the weld seam, and the dolly is directly behind it. Keep lots of pressure on the dolly, you don't want it bouncing off when the hammer hits it.
After one pass, it should look better. You may have to do more of this, depending on how accurate, and how hard your hits were. |Try to be consistent in both of these. Of course, certain areas may need more attention than others, say, on corners, or if there was more gap, and you had to stay on that area longer to fill it. More heat, more stretching needed!
In the end, it's a difficult task, even for people with some experience. Good luck with it! You might want to weld and practice on a scrap panel first!

Sorry to tell you that it probably will be even more difficult for you to repair the damage, The oil canning problem should have been addressed before welding in the patch. Now, even if you are successful, you may only bring it to the point it was before the patch panel install. That is, still with the original reason for the oil canning. If all the problem was in the area replaced by the patch, you may be okay.

The current issue is the same as before I did the patch I reached out in another forum and was suggested that the new panel could add the strength to fix it. Unfortunately that didn't work. So should I look at this as 2 separate problems? Work to planish the weld seam and if nothing changes try to shrink the oil canned area?

Thanks for your help.
Art

I appreciate the advice. I will spend more time on planishing my weld as recommended. I believe I have an original problem with distortion in the section above the patch since it occurred as I cut out the rusty piece before I welded in the new metal. I included a YouTube video to show the warping and oil canning. You can see the distortion goes as high as where the stainless molding holes are, which is quite a bit above the weld seem.

https://www.youtube.com/watch?v=_rbNryIebb8
Thanks for the help.

Art

Thanks for your responses. Today I spent some time trying to tackle my issues and I think it came out ok so far. I first spent time planishing my weld and then addressed the sunken areas above the patch. The planishing took care of the small sunken portion right above the patch, but not the two sunken areas above. So after planishing, I used my shrinking disk on the two top areas and after about an hour of working on it, I was able to mostly eliminate the sunken sections and pretty much took care of the oil canning. I like the idea that Lostin50s mentioned on adding fiberglass filler on the inside to ensure no further oil canning.

My panel is not smooth and will require filler. I would like to spend more time working to smooth it out and especially make sure there aren't high spots that would show up through the filler which would have to be hammered down. I hope to avoid any hammering after the epoxy and filler are applied as I am concerned that doing so could create an adhesive problem for the top coat. I would like to spend time blocking it now to make sure it will be ok when adding filler, but it is still too cold to apply epoxy. I might use a spray can to show high spots and then remove it before applying epoxy.

I added two pictures. One shows how the panel is much more straight than when I started and the second shows the areas I used the shrinking disk on. At the start of today I thought I might need to do the whole job over and maybe go for a quarter panel, but now I think I can get by with some more work and filler.

I very much appreciate the help.
Art

That section looks real good.
I would place the straight edge like you have it and then slowly move down the contour of the panel. If you hit any high spots deal with them now.