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What ya’ll think about an overlap tack welded seam vs running a bead the whole seam?

I am dealing with a ton of tack welds and am wondering if it was an economy thing or something like flexing. It surely seems as though all the rust areas are an overlapped tack welded seam.
 
What ya’ll think about an overlap tack welded seam vs running a bead the whole seam?
Why butt weld over creating a flanged overlap? Especially if inside of flanged overlap is accessible.


Take some scrap sheet metal and make some test plates, try butt weld vs overlap and see what warps less and is easier to weld for you with your setup, every weld type has its place and if you plan to metal finish and work the steel to minimizes body filler a butt weld is superior as long as your fit up was tight. For anything structural or (if the backside won’t be accessible after welding making metal working impractical for what we are talking about here) I will form some sort of backing for the weld with a lap or flange to speed the process, minimize warping and give me a stronger weld joint.

I use a lot of 14 gauge for patch panels, it is a bit thicker and I find it is easier when welding to the thinner rusty areas if you concentrate the heat on the thicker part and just flow the weld back to the thinner material as you travel, I’ll stitch weld and skip around on the longer passes and something like the rocker repair I wouldn’t worry about welding 100% the length if you have overlap just seam seal after you’re satisfied you’ve got enough welds to meet or exceed the spacing of the factory spot welds for that same panel.
 
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A butt weld will ensure complete penetration and also does not give rust an area to hide.



Weld through primer will help with overlap rusting as well as post repair coatings, ValuGard Rustproofing, Fluid Film, undercoating, or something similar. Remember no factory butt welds panels together nor do they weld 100% (spot welds with spacing on a lap joint is what you mostly see). You are starting to see a lot of panels bonded together and welded in just a few strategic locations, in fact I used this technique when building a few of the Angry Pig parts and so far they are holding up well and it saved me a ton of time dealing with miles of warped welded panels.
 
They sell vise grips for this
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Other option is an offset then you can just spotweld in a few places as opposed to welding entire seam.
Agree spot weld or plug weld if using a mig on an overlap joint is the fastest best way to repair, for me creating the "offset or flange" to form the overlap without using rolling dies is hit and miss. I've tried the hand held pneumatic type and vice-grip type and both have worked but distort the panel almost causing more work than they save. I find if I'm doing a repair like @xtiaan2000 on the under side is doing on his rocker if I plug or spot weld a backer plate to the inside to form the flange it saves me time and looks better.

This video shows plug welds with a mig if someone isn't familiar with making spot welds with the mig.

 
Weld through primer will help with overlap rusting as well as post repair coatings, ValuGard Rustproofing, Fluid Film, undercoating, or something similar. Remember no factory butt welds panels together nor do they weld 100% (spot welds with spacing on a lap joint is what you mostly see). You are starting to see a lot of panels bonded together and welded in just a few strategic locations, in fact I used this technique when building a few of the Angry Pig parts and so far they are holding up well and it saved me a ton of time dealing with miles of warped welded panels.

All true points, and have done repairs using several of those techniques. I would add to the pros of butt welding in this particular instance, that if it’s carried out in normal sheetmetal MIG welding repair technique, you’re not really going to have to worry about warpage too much, because it’s a floorboard. On certain external repairs where appearance is more critical it helps to have some other options.
 

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