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  #1  
Old 07-11-2022, 05:03 PM
foamcar foamcar is offline
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Default How to remove outward bump in concave trough

356 Porsche under long term repair and rebuild. All rusty and accident damaged metal repaired except for this area. There is a concave trough or waterfall that is distorted due to severe damage years ago in the rear qtr area. The driveside trough is fine and extends 1" further inboard than passenger side. There is an outward bulge in the bad trough that oil cans if I press it in. Before attacking this am looking for advice on how to sink it in. Im thinking torch but have not done much torch shrinking. I have roughly outline the area of the troughs and circled the outward bulge.20220711_165940.jpg

20220711_172202.jpg
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  #2  
Old 07-12-2022, 12:41 AM
Jaroslav Jaroslav is offline
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If you have the courage. I adapted this hammer for similar situations. Sometimes it solves a complex problem. The plastic ring is for a good grip. Regulation of the force of the blow is air pressure. Radius tool. You may have to cut the sheet to make the shape smooth. It is not clear from the photo how high it is.

It might solve your situation. The next step is for the sculptor in the paint shop and a shovel with putty.
DSC07854.JPG

DSC07853.JPG
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Last edited by Jaroslav; 07-12-2022 at 12:47 AM.
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Old 07-12-2022, 05:13 AM
Blackfinger Blackfinger is offline
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Definitely a two man job if heat shrinking.One man inside with soft dolly to support metal,outside guy heats lump then hits lump down slowly then cools with water.
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Old 07-12-2022, 12:03 PM
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Steve Hamilton Steve Hamilton is offline
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Hi Phil
My first thought is what caused the bulge ! I think that it is a pressure buckle that caused it. I would investigate to see if there any sign of damage to the structure under that area. If the car was hit low and from the rear, like the bumper, the bumper mount area could collapse slightly to the front and down. If that were to happen it could cause a buckle in the trough. The fix would the require a pull to the body to move things back to proper alignment,and allow the buckle to release.
If the damage was caused by a blow to the inside of the panel at the bulge then the repair can be make directly to the bulge in the trough. The area is called a reverse. Concave one direction and covex the other way, these are tricky and must be dealt with carefully. A bulge up on a low crown convex panel requires shrinking an a bulge up on a concave panel requires stretching. Here you have both so it may require some careful analysis as well as the proper process to remove the bulge.
The panel could be just pushed out of arrangement, of that is the case some careful off dolly work might jus fix it.
not Enough information to make a difinative answer.
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Old 07-12-2022, 01:03 PM
crystallographic crystallographic is offline
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Hi foamcar,
I'll suggest a subtle method that does not involve special power tools, shovels, or spackle - or an extra trained helper:

If you have an O/A torch-
Put on a small tip, say a #1 or #2.
Set the inner cone length to a 1/4in. thickness and sharp.
P1060430 copy.jpg
Get a light body hammer with a gentle crown on the face.
P1060431 copy.jpg

This is a gentle method.
Be sensitive to what is happening.

You will only use the hammer nd the torch, one thing in each hand, torch lit and ready.

Get a seat and get comfortable.
You will need to be accurate, brief and senstitive.
Good lighting that is in front of you, directed downwards and bouncing off the metal helps show you how your metal swells, and your results.

Warm the highest spot, a 2in circle marked with pencil.
Warm it gently, torch cone 1-1.5 in. off the panel, Straight Down, 5 secs, As You Watch The Metal Swell -
when Metal Stops Swelling then lift torch and point it away and Gently tap the hammer 3-5 times on the high spot, work in small circle as it goes down and then larger circle going out to mark.
Stop hammering.
Use straight edge to show flatness relative to needed contour.
No color on the metal from heat at all. (except on back side )
Let the metal cool down and continue its own shrink by itsef. NO QUENCH.
Sometimes you only tap it once or twice and it goes home and stays.
(Sometimes sunlight is enough heat, or a blowdryer. )

Remember that if it gets hard/resistant to your effort, then try bumping someplace else.
(I've done this little tune-up method a thousand times, over decades.)

(I learnt this from a "Dust-bowl, Depression-era metal man" who was known for straightening wreckage and "hardly hitting the metal." I spent 5 years working next to him.)

yeehaw,
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  #6  
Old 07-12-2022, 04:23 PM
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Hi Kent
Guess I should have been more patient and waited for your great advice.
Thanks for the solution to a stubborn panel bulge!
I haven’t made enough mistakes yet to be a master, still learning. Now if I can remember that when I need it.
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Last edited by Steve Hamilton; 07-12-2022 at 04:27 PM.
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Old 07-12-2022, 08:55 PM
crystallographic crystallographic is offline
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Quote:
Originally Posted by Steve Hamilton View Post
Hi Kent
Guess I should have been more patient and waited for your great advice.
Thanks for the solution to a stubborn panel bulge!
I haven’t made enough mistakes yet to be a master, still learning. Now if I can remember that when I need it.
Heh - You were writing yours same time as I was shooting stills and writing mine..... all good stuff, +++ together.
On olde wrecked/straighted/wrecked agin/fixed summore autos ... etc. I have learnt to be "keerful."

(No sense hurrying to the scrap yard.)
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Old 07-13-2022, 12:52 AM
Jaroslav Jaroslav is offline
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Yes Kent, that's how it should be. However, I would say that the place where there is "cow shit..." will require more strategy and the shovel with putty in the end.
I would say that the glued weld will crack similar to if you reshaped a bird's nest. Very thick layer. If you grind it at this moment, you will see through the holes the secret that is hidden in the cavity below. It might not be that bad, but I've seen it before.
We recently used a pneumatic hammer to remove 30mm of sealant (more than 1") from a beautifully painted car.
Suddenly was lighter. You mustnot forcefully close the doors on cars like that.... The crack kept appearing, it had a strange shine to it. The problem was that the putty held and at the same time it didn't hold enough.
Putty, of course, has a different thermal expansion.
If you're buying a nice car, buy it in the sun and give it time. Bloom by yourself....
Sorry - thoughts, predictions. I will be very happy to be wrong. But it has to be named somehow.
Simply. If it can't be knocked and cemented, make a new reverse curve and replace the part. Maybe it will be less work.
The person who repaired it knows very well how he did it.....
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Old 07-13-2022, 09:22 AM
crystallographic crystallographic is offline
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Quote:
Originally Posted by Jaroslav View Post
Yes Kent, that's how it should be. However, I would say that the place where there is "cow shit..." will require more strategy and the shovel with putty in the end.
I would say that the glued weld will crack similar to if you reshaped a bird's nest. Very thick layer. If you grind it at this moment, you will see through the holes the secret that is hidden in the cavity below. It might not be that bad, but I've seen it before.
We recently used a pneumatic hammer to remove 30mm of sealant (more than 1") from a beautifully painted car.
Suddenly was lighter. You mustnot forcefully close the doors on cars like that.... The crack kept appearing, it had a strange shine to it. The problem was that the putty held and at the same time it didn't hold enough.
Putty, of course, has a different thermal expansion.
If you're buying a nice car, buy it in the sun and give it time. Bloom by yourself....
Sorry - thoughts, predictions. I will be very happy to be wrong. But it has to be named somehow.
Simply. If it can't be knocked and cemented, make a new reverse curve and replace the part. Maybe it will be less work.
The person who repaired it knows very well how he did it.....
Yes, agreed Jaro.
I have arrived at many solutions from doing many many "rough patches" on 356 Porsches. Although, it is easier to repair those bodies to "metal finished" when using scraps of patch material from a donor body. Alloy match is non-trivial - on some manufactures.
Even when the overlay patches stack up to 5 in number, with fiberglas, pop rivets, and miracle mud stacked in, when the job is metal finished no passer-by through the shop could ever determine what transpired on that old Silver Ghost.


(I am thankful I never had to repair the old Packard that had the right rear quarter panel covered in concrete, with 1.5 inch wood screws driven out through from the inside, holding the 175lb "filler patch" on. The old mechanic told me he was looking for the reason why the car was sitting low in that corner - and was replacing the leaf spring when his light shone up into the dark recesses enough to reveal heads of wood screws, facing in. )
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  #10  
Old 07-13-2022, 09:41 AM
Jaroslav Jaroslav is offline
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Yes Kent. When two do the same thing, it's not always the same thing.

Recently, with the pedal cars, I threw half of the fenders of about 6 in the waste bin for later tasks. And I started a new one completely from scratch with a different procedure. Sometimes you have to admit to yourself how it really is.
It delayed me, but the result came out right. Although there was a fight against time, quality was the number 1 point.
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