Tuesday, March 3, 2009

Quarter Patch

I left off by removing the old trunk floor and preparing the rear frame rail for the new passenger side trunk floor panel. So now, with everything else out of the way, I felt it an opportune time to repair the nasty cancer hole behind the rear wheel seen here.

I started this repair by marking the bad area of the rear quarter panel well beyond the cancer with blue masking tape.

I then followed the inside edge of the masking tape with my angle grinder cutting disk. I use masking tape because it's easy to see and follow through the sparks while cutting. With the bad quarter panel section out of the way, the damaged lower outer wheel well is visible and accessible.

They sell a patch for this section BTW which costs around $25. I didn't think to buy one in my last order and didn't want to wait for 3 days to get it so I opted to patch it instead. I repeated my tape and cut routine on the damaged outer wheel house. I left the old flanges in tact because this area contains compound curves and I wanted to maintain the location of the original flanges temporarily and then weld in new flanges after I replaced the main area of damage.

I fabricated a new patch and welded it in and then cut out and welded in strips along the edges separately for the flanges.

I ground the welds and primered the newly repaired outer wheel house. Now I needed to do something about that big hole in the lower rear quarter.

So, I bought a RH rear quarter lower patch panel from NPD.

I used the removed scrap as a template to cut a starting patch. I mark and cut a patch about a quarter inch larger and go through a moderately tedious routine of fine fitting, marking, and recutting against the hole in the quarter. This particular repro patch panel was a bit off and needed some massaging to get the edges to really mesh with the original panel. The creases and bends were not as sharp as the original so I needed to sharpen the bends via hammer, vice, and dolly.

After about an hour of fiddling, testing, refitting, and fine-tuning, I came up with this final fit before welding.

I placed a tack weld at the most flush point between the original and the patch and then consistently adjusted and tacked the panel to the original all along the seam ensuring that the two were flush with each other at every tack point.

Now, the pros I think use a copper bar to back a seam weld like this so that the thin sheet metal stays cool and the seam welds fill properly. I used another method I learned which is to soak a towel (an old T-Shirt in my case) in water, wring it well out, and pack it on the back-side of the weld seam. I wasn't able to get the wet rag between the quarter patch and the wheel house panel so it remained unprotected for which I just needed to be careful. I noticed that the white paint bubbled and scorched where the rag wasn't in contact near the wheel opening which indicates to me that the protected area really was cooler than the unprotected area. This procedure did nothing to help my sloppy seam welds however.... *cough*.

I think the main reason I like to grind welds is that it lets me hide my sloppy welds but this time it's necessary to provide a consistent-looking panel. This didn't turn out all that terrible. I was worried since this was my largest exterior panel patch. A little body filler to equalize things and you won't be able to tell that there was a huge cancer hole here.

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