Oil Canning question

[Boba Fett 76]

Hey All,

      Quick question...My car is in the process of getting painted and when the rear trunk lid was painted it showed signs of  oil canning.  Specifically, where the underside c channel gusset is tack welded to the upper sheet metal.  The question is, was this something that was a result of soda blasting, lack of block sanding or is that a typical factory condition resulting from the tack weld (panel bond) on these cars?  I don't have any reference vehicles with good enough paint jobs to know.  I am concerned that the hood will show in a similar manner.   I have attached a photo for reference.  

Thanks in advance for any info.  

[tech71]

How is the adhesive between the inner skin and support frames? I know that if it debonds or is removed, You can get some noticeable rattle and or buzzing. Probably some unwanted flexing as well.

Thats all I got.

[esty]

oil canning comes from the metal being stretched due to heat...heavy, long disk sanding..... sandblasting and disk sanding for too long at a time creates enough heat to do that...soda blasting not so much...my guess is the braces/supports aren't effectively attached to the panels

[72pdx02]

Like Esty said, oil canning is from the metal being stretched. It doesn’t have anything to do with the frame work under the skin. A good metal person will heat the area and quickly quench it with a wet rag. If you don’t know what you are doing it’s a real pain to fix.

[Boba Fett 76]

Tech 71, I need to check the adhesive and the foam inside the bracing.  As I recall it is still intact.  Esty, the oil canning is very slight, that is why I was hoping it was factory.  After the car was soda blasted we went over it lightly with orbitals to make sure the rust inhibitor was removed and the metal was smoothed a little prior to epoxy coating.  We were pretty gentle, hope it wasn't us.  72pdx02, I wish I knew more good metal guys.  I appreciate the input y'all, I think I might be on the hunt for a new trunk lid and hood.  

[ISS Werks]

There's a couple metal shrinking techniques but they all are done to bare metal, nothing applicable to a painted panel.  You're only option at this point is the sealant between the skin and understructure.  I'd suggest using a 3M 8463 that's a closed cell 10:1 expanding foam.  As long as it's not confined it should expand inbetween the skin and structure and provide the support needed.  Dries very quickly so have a solvent ready to wipe the excess off the painted underside.  Good luck.