Huge High spot on roof

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PostPosted: Wed May 25, 2022 1:52 am
Hello Everyone !

I've let my car to the body shop for the final work and paint, there is a Huge high spot on the roof that I thought they could fix, the problem is they can't !

They tell me the roof has had a lot of work on it before they took the car ( I worked on one side of the roof too ), and that the metal is too stiff to do anything, but it looks so bad as it is, I'm thinking about replacing the complete roof skin but that will cost me a lot

It's quite surprising to hear that there are no other solutions at all, it looks like an over stretched metal, they didn't try any kind of shrinking, they don't use oxy acetylene or anything, they just tried to hit it with hammer and dolly, which, from what I learnt, would probably just makes it worse .

Yes, they are professionnal and probably knows way more than I do and I don't want to act like I know better, But I just can't think of paying for a complete paint job with a roof like that, What do you guys think about it ?

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PostPosted: Wed May 25, 2022 7:59 am
It could probably be cold shrunk, But you would need 2 people, one on top one below, using a combination of a hard hammer and soft dolly, or soft hammer and hard dolly. It works when both people know how to do it, and know how to work in conjunction with each other.
On the other hand, a shrinking disc, again, in the hands of someone who is experienced, would also do the trick. Probably with more control, IF they know how to use it.
Semi-Hack method: 2 x 4 or small sandbag underneath, and use a pick hammer to make lots of small dings in the high area. You've already got filler in the area, so adding a bit more isn't that much worse.



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PostPosted: Fri May 27, 2022 9:41 am
I would use a shrinking disk first myself, BUT Its Hard to say without studying the panel up close and in person like Chop says their are a few different ways to go about repairing damage like this.

Using a Pick hammer would be my Last resort. as would replacing the roof panel.
Dennis Barnett
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Line Maintenance A&P Mechanic and MOC Tech specialist.



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PostPosted: Tue May 31, 2022 5:30 pm
Thank you for your replies, I'm going to take the car back from the bodyshop since they can't or don't want to do anything about it ..



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PostPosted: Wed Jun 01, 2022 7:12 am
Hello, Dennis! I know you have enough experience with metal to know a hack method, from a good one. Yeah, attacking it with a pick hammer is super-hack! But, there's a method I use, in a pinch that works well for me, and it's not so hack. I urge you to try it , if you get a chance.
OK, so you're blocking out your primer and hit a shallow high spot, not very high, but high enough. Might be filler around it, so you don't want to get too aggressive in anything you do on the panel. I take a sharp pick hammer, and very lightly tap on the high area. Just about the weight of the hammer falling on it, from not too much distance. 10, 20 hits, and feel it. There should be NO dents or deep pick marks, only what looks like pencil marks on the metal. If it still feels high, do some more, but never increasing the hitting pressure! More very lgiht hits are better than hard ones.
Once it feels good (it almost never 'looks' different), I lightly drag a vixen file across the surface, both to smooth it a tad, and to see if any high spots remain. Usually that's enough. Sometimes I apply a thin coat of glazing compound, just to be sure. The pick marks disappear completely, and the surface is usually dead even with the surround. The metal is NOT thinned much, even though you used the vixen, as it only takes a light swipe with it, you don't want to remove much, if any, metal.
Last edited by chopolds on Thu Jun 02, 2022 7:22 am, edited 1 time in total.

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PostPosted: Thu Jun 02, 2022 6:00 am
I have one pick hammer with a very sharp point. Absolutely perfect for small to moderate highs, very gently, lots of taps.

Lots of different ways - just depends on the individual situation.

I like to think of a high spot as a dent, but viewed from underneath. Most of the time it's being held in that high position by tension around the outside. So, if you can access the underneath, use a big glue puller tab to put some tension on the high itself (sometimes just hanging the slide hammer from the tab is enough and then lightly tap around the outside, just as you would if it was a dent on the outside. If the ridge around it is really visible then glue tabs from the outside can work, too, but be wary of stretching too far.
Chris

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PostPosted: Thu Jun 02, 2022 9:09 am
Thanks for sharing that pick hammer method. I too have repaired enough of the "hack job" pick hammer repairs to scare me off from even trying it.

When you say "sharp point" was is the approximate diameter of the pointed end? Mine is about 1/8" in diameter.
1968 Coronet R/T


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PostPosted: Thu Jun 02, 2022 9:43 am
Hey guys
Chop as I said its the Last thing I would do, Have I done it as you describe? Yes.
But I reserve it for very small hi spots that I have already worked extensively generally found during the primer sanding process that are not cooperating.
This is my flat out last thing I use to get the panel were I want it to be out of frustration generally during the finishing process.
I have learned a lot from you and others here by doing the work over the years I respect your opinions and suggestions ALWAYS!

His High spot is far to hi for this method in my opinion it needs shrinking.
I am very surprised he is not asking for help with Oil canning? I am sure before its done their will be some.

Their is a lot going on with that Panel
Look at his very first pic towards the rear window frame you'll see a slight crease.

Also look at the primer the way its sanding out its crying that their is more panel damage needing to be worked.

Look at second pic The Hi spot is actually flat on strait edge and actually appears to be a low when viewed against the roofs contour theirs no crowning in it at all its flat.

Third pic panel has been filled and crowning to much when sanded with a long block telegraphing roof crown.

Panel should be striped work all the damage outside in! My Guess is who ever started working the damaged panel started with the major damage first and figured to leave minor stuff for later or just fill it. They worked inside out Instead of working from the out side in!

You know as well as I do you always work panels as a whole working from out side the damage and work in, I don't think this happened with this one.
You also know that the slightest little dent or crease can Lock the panel up and it wont do anything you want it to do, That first crease I pointed out could be one of many little things causing his heartache.

Mean while they worked the dent best they could with the other small damage in it first causing even more stretching trying to get the damage up. only to find out they cant get it.

My advise: Always Remember a Stamped piece of metal ALWAYS want to return to its original shape! Remember that!!!!!
The damage can be worked out! Just dont hit it with a Torch! and Never Pound or beat the snot out of it NEVER!

Go back strip roof entirely back to bare metal get some machinist dye or black paint coat roof and start sanding with 80 grit on a 24 inch Paint stick from home depot find and Identify Hi / lo spots work panel as a WHOLE starting from OUTSIDE first and work IN.

Hammer on Dolley = Stretches Metal (Dont do Dat!) (Their is a time and place for it)
Hammer Off Dolley = Bumps metal (Do DAT!)
Hammers: Get a good Body hammers with a Low Crown!!!! (I like Martin and Snap on)
Shrinking Disk = Get one, watch some videos! good ones come with a training video.
Don't use a Torch for shrinking! Advanced stuff takes a lot of skill not to over heat panel.
When using shrinking disk don't over work or over heat panel you just want to heat it enough to cause stream from your wet rag. Its slow and noisy take your time always work panel OUT SIDE IN!

You had enough patients to get the panel this close, Take your time a few deep breaths remember what you learned and start over.
We all have been their its a learning process, I did not get ok at this stuff overnight by reading or watching videos I learned it by doing it I will not say I am good at it!
Chopolds & Chevman are very Good at it!!!!!
I learned the Hard way Listening to mentors such as Chop & many many others doing it and making A LOT of mistakes along the way just remember the Panel wants to go back to its original shape it just needs GENTLE help to get their.
Dennis Barnett
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.



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PostPosted: Thu Jun 02, 2022 11:32 am
'68 Coronet R/T wrote:Thanks for sharing that pick hammer method. I too have repaired enough of the "hack job" pick hammer repairs to scare me off from even trying it.

When you say "sharp point" was is the approximate diameter of the pointed end? Mine is about 1/8" in diameter.


Mine is far sharper than that. its actually very pointy but Tip is Blunted down and rounded so it doesn't actually dig into the metal I don't like to use it.
Dennis Barnett
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.



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PostPosted: Fri Jun 03, 2022 7:14 am
'68 Coronet R/T wrote:Thanks for sharing that pick hammer method. I too have repaired enough of the "hack job" pick hammer repairs to scare me off from even trying it.

When you say "sharp point" was is the approximate diameter of the pointed end? Mine is about 1/8" in diameter.

Very sharp. Sharpened to a point. Usually the first couple hits dull it just a hair, and that's what you want. I guess you are putting micro dimples in the panel, to gather the metal together. Not deep enough that you would have to fill them, either.
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