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Old 04-12-2021, 08:38 AM   #74
ItWillBeSlow
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Join Date: May 2013
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Re: Roostre's 1967 C20

Quote:
Originally Posted by Roostre View Post
Sure, I took my angle grinder with a cutoff wheel and cut the outer roof panel about 1/2 inch away from the seam. My old panel was trash, so I didn't care about ruining it. I then took the same cutoff wheel and grinder and used that to cut out the spot welds and carefully pulled and pried the thin strip of roof panel off the rear panel.

I had to think for a while about how to clamp the rear seam because I couldn't get to it. I ended up using 2 ratchet straps secured to the firewall and bed over the roof with a 4x4 board under them to put a little clamp load on the rear seam from the outside. I then squeezed a little more adhesive into anywhere I felt the seam wasn't filled adequately. This should work just fine. Remember that this is structural adhesive, so it's really strong. The outer roof skin just needs to be held in place and the seams sealed from water. If the rear seam isn't 100% strength of the seam sealer due to not being fully clamped, I really don't think it's a big deal. I used a bunch of vise grips with dowels in the drip rails around the sides and front of the panel. I'm sure these had enough clamping force to give the adhesive plenty of strength to hold the roof skin on.

Another thing that is helpful is that the rear panel of the cab has kind of a double bend on the lip that helps align the roof skin and hold it in place.

There was about an 1/8 inch gap between the roof and rear panel. I filled and sealed it with the adhesive, and will have to fill some voids with body filler. I could have probably worked with the two panels and made the seam much tighter, but didn't feel that it was worth it for the scope of this project.

Sorry, I see you asked how to not damage the inner roof panel. If you cut about 1/2 inch away from the rear seam, there's about a 2 inch void between the roof panels, so my 3 inch cutoff wheel did just fine. You can kind of see it in the pictures of treating the rust on the inner panel. I also like using the same wheel to cut spot welds because you can see when you are getting close to the lower panel and can stop before cutting into it.
Thank you, great info. You also mentioned in your earlier post there were a couple minor fitment issues with the new panel. Can you elaborate on those? This panel makes me more nervous than some repops in that it could only be “adjusted or modified” so much.
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1972 C20
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