WELD LOCATION!

There are a few different considerations in locating weld seams on low crown panels, such as the quarter panel. In most cases, as mentioned above, a seam horizontally through the middle of a low crown area of a panel is just asking for trouble as there is little shape (strength) in the panel to resist any movement/distortion from the shrinking, and why a weld here normally results in a severely caved in valley. (given no planishing to counteract the shrinking). For the most part one would put the weld up as high as possible, as most quarters have enough shape toward the top where the quarter slopes inward to help resist movement and distortion. It also puts the seam up where most if not all is better accessible for planishing. That is the normal scenario.

In other cases, perhaps the panel is blocked by an inner wheelwell or other structure that prevents/discourages planishing the weld. In this case, one can be creative in making a dolly on a stick, say a piece of steel flat bar that would fit in the void, welded to a pipe to allow better reach. I've also employed the assistance of my nephew in remote cases where his youth permitted more of a contortionist approach over what my body refuses to do anymore. This is also why it is important to planish those weld dots individually, and then grind them out of the way, front and back. This way two people can better work together on either side of a panel to planish out the welds, and more accurately find the correct weld dots in doing so. You also have the option of removing an outer wheelwell to better address an exterior panel that everyone will see, and then replace the wheelwell after you are satisfied with the metal bumping and finish work on a quarter.

Next, you can use features of the panel in your favor. Here is a lower replacement panel that I fabricated for the bottom of a 55 Chevy wagon lift gate, that has had no planishing performed, and looks to be one that will finish easily using only epoxy primer...









Other side.....











Any imperfection are slight enough that epoxy primer will take care of them. But as you can see, the panel where the weld travels through has a crown that protrudes outward in the horizontal plane, and inward in the vertical plane. So the shrinking forces tended to counteract each other, and the panel stayed exactly where it was. The weld's limited length also help out to limit the shrinking effects. So this shows a good example of using panel profiles in weld placement to limit distortion/panel movement while using the MIG. Similarly, a higher crown that is normally toward the top of a door skin/quarter panel, will tend to hold the shape better than the low crown areas down lower or through the middle, and a bead detail helps even more.