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Rear panel welding

Posted: Mon Aug 12, 2019 10:11 pm
by bartigue
I plan to cut the original outer upper and lower rear panels from my 69 as they have quite a bit of rust. AR sells replacements and I’m hoping to do a good enough job to get them in with minimal Bondo afterwards.

Tips? Anyone cut out these sections and replaced before? Should I just use the minimum needed from the new panels or replace the entire thing?

Re: Rear panel welding

Posted: Tue Aug 13, 2019 8:36 am
by friedman
I had to replace the rear panel between the tail lights on my 80 spider. It was really the lower portion of this panel that had rusted out. My usual approach to things like this is to retain as much of the original sheet metal as possible. So I cut out the lower portion that had the rust and this included the spot welded joint between the this section and the top of the roll pan. This is the horizontal flange everyone has that is hidden by bumpers. I had access to a parts spider where this section was good and cut it out.

The rusted section I removed included the lower inner portion of the taillight housing which was good as it made for an accurate locating of the patch panel. I flanged the upper section of the patch panel to slip behind the existing metal to make a lap joint since I can't do butt welding. The finished product far surpassed my expectations and the cherry on top was Mr. Erskine telling me I did a good job....simply unheard of praise!

Re: Rear panel welding

Posted: Wed Aug 14, 2019 7:28 am
by bartigue
Thanks for the input, I’m thinking the same. I can entirely replace these panels if I can get to them and cut them out without having to replace the inner panels. Otherwise I’ll be cutting, welding, grinding...

Re: Rear panel welding (Replacement)

Posted: Thu Aug 15, 2019 7:01 am
by fp55scca
--Brad, I recommend replacing, vice cutting and welding long seams.

--Cut the old panels down to the pinch-welds. Then cross-cut the pinch-welds between each spot weld, taking care not to cut the inner panel. For longer distances between spot welds, several cross-cuts may be needed. Grind and chisel the outer layer to remove the remaining material from the pinch-weld.

--When installing the new panels, drill 3/16" holes in the upper lip of the lower panel where it will be spot welded to the upper panel. Spot welding in these holes, and then grinding as necessary, will give a clean presentation. An arm load of Vice-Grips will be needed to re-install, fit, and weld the new panels.
--Save the slotted tabs on your old panels that secure the rear bumper on the inside. You will have to weld these to your new panels. These tabs are not included with the replacement panels.


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Re: Rear panel welding

Posted: Thu Aug 15, 2019 8:46 am
by bartigue
Wow - great photos and work! I only hope to achieve such a result. Thanks for the encouragement!

Re: Rear panel welding

Posted: Sat Aug 17, 2019 1:56 pm
by vandor
Nice work Jim!!

What did you paint the panels on the inside? Especially the parts that have been welded on? Were you able to get to them after it was all together?

On my Coupe I will have to weld the rocker boxes shut, and I wonder what to do about painting the inside so the welds don't start rusting. I know about weld-through primer, but I'm pretty sure it burns off during welding leaving bare metal on the inside. Maybe I will leave a hole on the end and use the Eastwood frame coating with the 2 foot long hose.

Re: Rear panel welding

Posted: Sun Aug 18, 2019 5:42 pm
by fp55scca
vandor wrote:
Sat Aug 17, 2019 1:56 pm
What did you paint the panels on the inside? Especially the parts that have been welded on? Were you able to get to them after it was all together?
------------------------------------------------------
--Hi Csaba, sorry for late reply. On the rear panels, note that I drilled access holes in the inner panels (see photo with old panels removed), for two reasons. (1) I needed to access the back of the license plate lights to secure them to the new outer panel(for the CSA, these are X1/9 lights); and, (2)to provide more access to treat the interior weld points.

--After all welding is complete, I use a combination of Ospho first (phosphoric acid) followed by POR-15, diluted slightly with laquer thinner to penetrate the seams. The access holes in these panels are just left opened afterwards, but you could plug them for aesthetic reasons.

--You can do the same for outer rocker panels, by drilling a couple of 1" access holes and using a garden type sprayer wand with Ospho. Holes can be plugged with plastic caps.
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Re: Rear panel welding

Posted: Mon Aug 19, 2019 12:21 am
by vandor
OK, thank you!