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Pitfalls of flanged seams

#1
Ok, you guys have heard me talk incessantly about the downside of using flanged seams in sheet metal repair, discussing the ghost lines that can and will occur with these type of repairs. Today I got a short video to show the effect. This car was neat as a pin, with extensive rust repair performed, in basically the same locations as the 55 we're working on. The only flaw I could find in the paint was a line in the finish where the rear tailgate repair patch was seamed. I asked the owner if he had used flanged seams in the repair, and he said yes. He did offer for me to take pictures that others may learn from it..

Butt welds people!!!!!!!



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#3
I did a 69 Nova quarter panel with 3M panel bond and flanged the seam .no rust BUT can see the ghost line in the sun may not help that the car is black . The owner does not want to repair as don't bother him. I do but weld now. PS: overcast day looks great!
 
#4
Time to bump this public service announcement back to the top, I'm sure we've had some new arrivals that may benefit from it. #justsaynotoflangedwelds
 
#6
My name is Wesley. And I to have been wrongfully steered to the flanged seam. It was wrong and I admit to my falley. I will forever be a practier of the butted seam. Thank You for your time.
 
#9
I wonder what the science is behind this, one would think that a seam like that would be fairly strong and stable. I'd done them like that years ago, might have been lucky.
 
#10
The only flaw I could find in the paint was a line in the finish where the rear tailgate repair patch was seamed. I asked the owner if he had used flanged seams in the repair, and he said yes.
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Did you ask the method used to attach the patch? Like you said it looks like a line, like the edge of the patch is moving. Maybe panel bond adhesive?
 

Chris_Hamilton

Trying to be the best me, I can be
#11
I wonder what the science is behind this, one would think that a seam like that would be fairly strong and stable. I'd done them like that years ago, might have been lucky.
Crash my understanding of it, is that 2 thicknesses of metal expand at a different rate than the single thickness beside it. It occurs as the panel warms. The line is simply the result of the different rate of expansion. Probably not the answer you are looking for but that's how I've always understood it. I've seen Kent White (Tinman) demonstrate a method that involves a flange where he says this does not occur. I'd have to go and find the video where he demonstrates it but I have heard him say there are 2 ways to attach a flanged seam one right , one wrong.
 
#12
Well the factory did it with just spot welds along sail panels, but they also put it in a ditch and globbed lead on it. I've seen other makers do very nice seams on sail panels with silicon bronze, those are flanged as well. My quarter seams are generally butt with insert, though this may be becoming obsolete it was the advice for many years. Inserts make the panel thick too. So it's all a little mysterious to me even after all these years.
 
#13
Did you ask the method used to attach the patch? Like you said it looks like a line, like the edge of the patch is moving. Maybe panel bond adhesive?
Welded. I did ask, here's his response:

As for the flange repair there was no panel adhesive used and the lip was sand blasted and surface prepped before tacking and then drilled and plug welding approximately every 4 inches,

We went back and moved from one side to the other and did a continuous weld then ground it down.

Having never had any previous knowledge of how to properly make and weld panels this was the only way I was aware of, I know better now.

Thankfully the section still looks the same as when you saw it.

On another note, we used a cheap HF English wheel to make a insert for a 34 Chevy coupe and it turned out pretty good for not having any previous experience with rolling metal, we also had to make and replace all the reinforcement that had been cut out to make a dirt track car we were returning to the street.

The reason I am tell you this is we used the panel adhesive thinking it would minimize vibration between the filled top and the braces, the next weekend when we were ready to start sanding we noticed the panel adhesive drew the top and you could actually see the pattern of the bracing.

We ended up using piano wire to saw back and forth to cut the panel adhesive loose, It took us several weekends to correct the problem but the car was eventually painted black cherry and it turned out perfect.
 
#14
Ghosting crap like this is why I don't mess with fiberglass cars anymore. Different expansion rates for different thickness of materials. I like panel bond for some things but it makes a terrible filler material.

I was at our local bodyshop the other day and a guy pulled in with a 65' Mustang on a trailer he just bought. He was bragging about how he took a magnet and the car is rust free. I could see plain as day the ghosted quarters with spot welds every 4" down the whole side. The entire side of the car had so much wave that I thought I was at the Thanksgiving day parade. Shop owner looked at me and rolled his eyes. Thank god I don't have to deal with that stuff anymore.

I also have better luck butt welding with tig than mig. Mig welds sometimes ghosted through on me from the thicker weld bead. Ideally you can dress both sides and run a planish hammer down them but it's usually not very practical.

Thanks for posting the video. Good thing for people to know.
 
#18
I'd like to see what Kent does different. I respect him and have some of his tools and videos.

I think the seams that really show up are the flanged/panel bonded ones because your injecting a 3rd variable in the seam. On paper it seems like the way to go because the seam will be corrosion free. Especially for those of use that have removed a 40 year old flange seam that was welded and full of rust.

Seems like all of the factory flanged seams I've worked on are less than 6" long, in a stable location, and leaded. Sail panels the only exception and you can spot them on original cars. We are pickier than the people buying those cars in the 50's-60's.
 
#20
I'd make it a party. Tailgate centerpiece of room, sober hands only allowed to participle.
Shoot the breeze around it till everyone's ready, hard block & spray bottle ready.
Sand 1 layer at a time. Photo each layer (funny faces too).
Stop when metal seam's exposed..or is it! is the question. Chem strip the rest & photo away (funny faces too).
 
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