Sunk in roof

Dave C 5

Member
70 chevelle that a tree landed on roof - got it pretty straight but there still needs to be more crown to avoid excess bondo - plan of attack ? There was a lot of oil canning to begin with and most is gone now - shrinking disk from the inside ? Will that raise it up ? Pretty new to the big metal work jobs
 
Dave what did you do to straighten it? Did you do any shrinking? Without laying hands on it giving real advice is hard, but from what you say it sounds like you did. If you need more crown that means you need to stretch. Most definitely do not use the shrinking disc on the inside. That would just shrink the metal more. I would start by hammering on dolly any area you shrunk. Easy does it, just a little at a time. check your progress frequently.
 
Is was prett buckled in areas so yes, I did use a shrinking disk . I must have shrank too much ? Sucked the roof in too much maybe . So hammer on dolly to get it back - I’ll try not to bring back any oil canning- it’s still has a little but not near as bad
 
There was a lot of oil canning to begin with and most is gone now - shrinking disk from the inside ? Will that raise it up ?
No!
Sorry to disagree Chris, but if he can see that it needs more crown, then it is probably more than he can do with hammer on dolly IMO. Inexperience and excessive hammer on dolly can cause more oil canning. But this time Dave, use a railroad dolly with the correct contour, or something else with smooth edges and bigger than your typical hammer, and use it to bring the areas up that need it. There is a hammer for this, but its not likely to be in your tool box. Make sure your blows are hit square, not on the edge of your dolly, that causes excessive stretching.

Remember, after raising metal it takes a lot of hammer off dolly work for this, in addition to the disc.
 
No need to apologize to me Chev. I'm guilty of trying to give a condensed answer to something complicated. Like Chev said but I'll say it a different way as I was thinking about this at work and I happen to be repairing the roof of a 2012 Expedition where a tree branch fell on it. It's easy to mistake something being out of shape for oil canning (stretched) when in reality it is out of shape an the oil canning/panel flexing is a result of that. Dave I would bet that if you study the panel some more you'll see that it needs to move more. That is where the off dolly work Chev mentioned comes into play (one facet at least there are more). Run your hand over the panel feel the lows and the highs. Concentrate on bumping up your lows to start with. If you have trouble feeling the panel and want something visual use some Dykem or a big magic marker and cover the panel with it. Use a long block and make a few crosshatch sands across the panel to highlight your highs and lows, then start working the lows up and the highs down. IMO you won't need the shrinking disc for a while and not that much altogether. Expedition roof I just did only had to shrink in one spot and the damage extensive, nearly the entire roof. If you have a stud welder that can be very helpful as well. You can use the pins as a reverse dolly of sorts. Pin a low spot grip it with vise grips and gently tap around the low spot while pulling up on the pin. You can also lower high spots doing the reverse. Pin a spot near the high, hold light pressure with the vise grips gently tap down your high spot. Like I said most high spot on a job like that won;t need to be shrunk. If I can help more let me know, (Sure Chevman feels the same as well).
 
I really appreciate the help - I think I screwed up by using the shrinking disk too much— now I have it all tight and level but the problem is the roof crowns - I’ll give your suggestions a try . Thanks to both of you !
 
There’s a support that runs from side to side inside the car - I’m thinking I might put a jack in there and slowly try to push up and get it closer
 
May use soft wedges between the brace and sheetmetal rather than jacking up on the brace, you may have to temporarily support the brace though. If the panel will move up pretty close there are ways to lock it in place like careful metal stretching etc... then you have a better starting point to get it finished out. Then use panel adhesive between the brace and roof. Pics would certainly help to show what you actually have going on there.
 
I think I screwed up by using the shrinking disk too much— now I have it all tight and level but the problem is the roof crowns
A jack may have been useful in the beginning to push displaced metal back into the correct shape with the help of some hammer work on the creases and high areas. But it sounds like you overworked the metal getting it back in shape, and used the shrinking disc too much, causing the roof to be near the right shape but in need of stretching to gain more crown.

If that is the case, then a jack will not necessarily stretch the metal, it is more likely to push up one area by pulling from other areas. If it is tight now but still low, then you need to stretch it back out, and for that amount of stretch it takes hard blows with a heavy object to stretch only the area you are striking. Then a lot of hammer and dolly work, using the off dolly process (dolly on low area, hammer striking high area) and probably more work with the disc.

The shrinking disc has removed the metal memory of the original shape, so you will have to create the shape you want, hopefully it is only one area of the roof.

Some of the collision guys may have more to add.
 
Small area ? Oops- it’s the whole roof ! Pretty much worked the whole roof top - good news is it’s a 70 chevelle - not a whole lot of roof there. I just need to bring it up a little so I’ll give it sow good whacks from the inside then start reworking it from the outside
 
Not an easy job even for the most experienced at this point. Its usually quite helpful to compare what you are working on with the other side to get the correct contour, but it sounds like you don't have that luxury.

Good luck, I hope it works out for you.
 
If you had access to a handheld planishing hammer that would be very helpful. Otherwise you are gonna have to figure out another way to stretch it. Going to be hard if you did the whole roof with the shrinking disc:oops:. Another option (your not going to like it) if I was doing the repair from this point on, might be to remove the skin and wheel it until I got the crown back in it and weld it back on. Probably not realistic for you but it might come down to that. If I just had to use hand tools I would probably start stretching with a hammer and dolly. I know what Chevman posted above but that may be your only option if you dont have or have any experience with a wheel or handheld planishing hammer. I don't know what your experience level is really but evenly hammering on dolly across the panel will start to bring it up but it will be very slow doing so. Regardless it's going to be a good learning experience for you.
 
Condensed answer to complicated subject would be the topic here. Shrinking discs do work harden the metal. Bottom line here is that this is a high skilled job for anyone & a bad start to it makes it that much harder of a process to get close to perfect now that you added in some work hardening.
Sad to say, but Chris could be so right about it being easier to remove the whole roof skin to work on OR even replace. I learned the hard way to remove a long ass el camino rear quarter panel to work on rather than trying to repair a difficult area in place. R &R Cuts & welds are done near seams & edges where metal is less prone to warpage.
I didn't like hearing it either, but sometimes you have to do more work to do less work with better overall results.
Of course your next plan of attack depends on your individual results & goals.
As with any metal repair job before filler, high spots are far worse than low spots as they result in more filler everywhere for a long ways out to correct.
Also, think it's safe to say even the best metal men wish they were better, only 1 way to learn..... Some think I've done awesome on projects. They either didn't see how it bad my work looked early on or can't figure out how I got it straight in the end.
You can see some of my widebody project metalwork on my flicker link. 2 1/2" flare out at center along with using 69 charger upper quarter sections for new upper shape. Held on & off of vehicle with screws till it's minimal filler worthy. Main shaping in a custom reshape comes first, which can be pretty f-word ugly. Mine is currently what you call close to English wheel time. Hoping for bragging rights smooth, but a little heavier than skimcoat filler in spots won't be the end of the world.
Sometimes with bad dips, you may be better off hitting them slightly high in spots with a heavy plastic teardrop hammer to get closer to needed shape quicker, then working it down a little less dramatically with hammer & dolly methods.
Just trying to be a little encouraging...
https://www.flickr.com/photos/132029468@N08/
 
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I’m pretty sure roof replacement is not an option for this guy but I will ask him - just gonna have to try to stretch it back up - he’s not opposed to filler but we are at 1/4 inch in a lot of places and one wrong push from the inside cracks it- don’t want my name on that !
 
around the outside there is a roll buckle . even with all the work you should be able to find it. use machine bluing and a rasp . once you find it start your hammer work there. trying to stretch the entire roof is not going to happen . if you stretch the edges it will create the crown .
 
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