Oil canning quarter panel

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PostPosted: Mon Nov 11, 2019 6:00 pm
I'm working on a repaint on my old Mercedes. I'm pretty frustrated with oil canning in the rear quarter panel and was hoping I could get some ideas here.

The quarter in question is AFAIK original. It had a small dent from the inside which had cracked obviously excessively thick body applied by a lovely previous body shop. I stripped the area down to bare metal removing around 1/8" of filler all around. It appears to me that there must have been a minor dent on this quarter panel which was "repaired", and then to stiffen the panel and eliminate oil canning they just applied excessive filler (yuck). So I'm trying to fix it properly.

Right now the panel is about perfect if I press hard from the inside. When at rest it easily oil cans in and pops back with light pressure. The oil can area is definitely centered around where the dent was (now a bit of a low spot). This panel is fairly flat with a slight curvature, and is right above a body crease. Dent was right in the dead center of the flat area.

I'm not sure if I should focus on getting all the waves out of the panel first and then work with the shrinking disk to get rid of the oil canning... or the reverse. Right now it is a bit hard to work on because it tends to pop one way or the other with the oil canning.

Some pics:
Image

Image


Appreciate the tips. I'm decently experienced at fabricating and sheet metal, but "metal bumping" is fairly new to me!

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PostPosted: Mon Nov 11, 2019 8:58 pm
You will need to shrink the center of the dent.
If you have a stud welder they make a solid tip that will heat a small spot of metal to red hot. Then you immediately cool the spot with compressed air.

I generally work in a circle from the edge of the dent toward the center until it gets firm ( no oil canning.)
Shrinking Oil canned Metal.JPG


Once you get the metal firm again, you can use your shrinking disc to fine tune the repair.

There are others on here with much more experience than myself. Hopefully they will correct my technique if necessary.
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PostPosted: Tue Nov 12, 2019 6:44 pm
arsenix wrote:
Right now the panel is about perfect if I press hard from the inside. When at rest it easily oil cans in and pops back with light pressure. The oil can area is definitely centered around where the dent was (now a bit of a low spot). This panel is fairly flat with a slight curvature, and is right above a body crease. Dent was right in the dead center of the flat area.

I'm not sure if I should focus on getting all the waves out of the panel first and then work with the shrinking disk to get rid of the oil canning... or the reverse. Right now it is a bit hard to work on because it tends to pop one way or the other with the oil canning.


Is that body line straight? If not, then I would do that first, then do the other damage (waves) around the oil can.

With just pictures, its hard to say what is causing the oil can, but that is one way to proceed.

A shrinking disc can do wonders with an oil can, but its nice to correct the problem if possible.



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PostPosted: Tue Nov 19, 2019 11:24 am
Any one doing this stuff for any length of time has come up against the dreaded Oilcan dent. As Chevman said its extremely difficult if not impossible to determine the cause from just a few pictures let alone tell you how fix it properly.

Oil canning is caused by the panel being stretched or shrunk to far on one side or the other in most cases, It can be caused by bending the panel in an accident or by working the panel trying to straiten the panel. In either case Every panel has two sides both sides can either be shrunk or stretched on their surface or through the hole sheet.

In most cases a lot of time is spent working on the outside skin manipulating the skin with a Hammer and Dolly,
"Hammer ON Dolly" you stretch the Skin,
"Hammer OFF Dolly" = "Bumping" Bumping is not so intrusive to cause a lot of shrinking in most cases but it can!

When a Panel is stretched hammer on Dolly making the metal thinner its Hard to shrink it back because the metal itself has been physically displaced in a small area.
Depending on how much metal has been displaced in a small area, that area can and actually does become larger in that area and the metal is confined and trapped by the rest of the panel original shape. that extra metal needs to go some where and so it pops in and out!

While a Shrinking disk is a wonderful tool it has its limitations as does a Spot shrinker/Stud welder and a Torch all will create enough heat to shrink. BUT there are also other ways to shrink as well including just shrinking on just one side only!

The key to fixing the problem is identifying where the stretch or Shrinking is to much.
In all cases original Body lines need to be corrected and strait to begin with and your body line doesn't appear strait yet in that picture.

Remember ALL stamped sheet metal wants to go back to its original shape it only requires a LITTLE help to do that! LESS IS MORE and always work a dent from outside in.

Every dent is a challenge for me and no two dents are alike. :P
Dennis Barnett
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.

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