Roof patch causing warp / oil canning

[nsb29]

Well it wouldn’t let me add a picture to my previous post but this is the inner cab

[ItWillBeSlow]

Originally Posted by MP&C

And I would suggest epoxy primer inside all the nooks and crannies while accessible. A much better choice over POR, which will give off noxious fumes if it comes close to the heat from welding.

Originally Posted by tinydb84

My only input is to not use por15. I have had bad luck with it and seen far too many similar stories.

After 5/6 hours of wire wheeling, I have cleaned everything up as much as reasonably possible. About 85% of the surface area is clean and perfect for primer. The front "gutter" is lightly pitted and will not wire wheel to shiny metal. There are also some tight places in the corners that cannot be cleaned. I think this application is more favorable for POR15 over primer - thoughts? Should i put down some POR15 and primer over this?

The only heavier pitted areas are the corner braces which I am not concerned about, they will not affect a visible panel.

[ItWillBeSlow]

Originally Posted by nsb29

I have used panel bond several times in positions where if I could have gotten in there to clamp it I could’ve welded it, I used panel bond when I put the big back window in my 65 by making sure that the two panels lined up properly and touching each other All the way across I installed the inner cab Using the panel bond and clamped the cab around the door opening and window The panel bond that squeezed out of the joint was wiped off leaving a perfect seem and then spot welded the rest.
Just for kicks I have taken some of the leftover panel bond and pressed couple pieces of scrap together it’s stronger than a weld you can’t rip it apart

Thanks for the info!

[theastronaut]

The areas that didn't clean up with a wire brush need to be sandblasted to get rust out of the pits. An inexpensive spot blaster would be a good option for small areas if you don't already have a blaster. Then use epoxy to coat everything. Por15 or similar "paint over rust" products don't convert/kill the deep rust, and that looks like there will be some deeply rusted pits that'll show up when blasted.

[ItWillBeSlow]

Originally Posted by theastronaut

The areas that didn't clean up with a wire brush need to be sandblasted to get rust out of the pits. An inexpensive spot blaster would be a good option for small areas if you don't already have a blaster. Then use epoxy to coat everything. Por15 or similar "paint over rust" products don't convert/kill the deep rust, and that looks like there will be some deeply rusted pits that'll show up when blasted.

Thanks. I do have a spot blaster, I had previously blasted the full drip rail before I took the top skin off. I was hoping to get away with not using it due to how slow and nasty it is for large areas. I did find 2 pin holes hiding in the pitted areas, really close to the weather stripping inside. Ill probably start the blasting and see how it goes and cross my fingers more don't show up.

[SkinnyG]

Is peeling off the roof skin to deal with whatever is inside a wise thing to do on any truck just in case?

I have no rust visible through the paint on either side, but it has not been blasted yet. I don't really want to skin it, but if it's super wise......

[ItWillBeSlow]

Originally Posted by SkinnyG

Is peeling off the roof skin to deal with whatever is inside a wise thing to do on any truck just in case?

I have no rust visible through the paint on either side, but it has not been blasted yet. I don't really want to skin it, but if it's super wise......

Im not the most experienced to answer this question, but Ill throw out my $.02.

If you aren't in a huge rush and can spare an extra $250ish for the price of the panel, I don't think its a bad idea. If you end up with little or no visible rust in any of the roof area after you're done blasting, it may be a safe assumption that your cab is in decent shape in this regard and this would be a waste of effort for you.

I may have gotten lucky, but I am very happy with the quality of the new skin I received. Once this is complete I expect to have about 30 hours in the removal, clean up, and install of the new skin. Not done yet so time will tell..

So far I am happy with my decision to take mine off. I do have 2 or 3 pinholes to address and am on the fence about cut and weld or hit with a little filler after priming and sandblasting and be done with them.

[ItWillBeSlow]

Got the "gutter" and perimeter of the roof area 97% clean with my spot blaster. There is a small amount of rust left in some of the larger pits that I will be leaving as-is.

I did discover some more pinholes on the passenger side - my spot blaster created these while cleaning. I've almost got this patched up. A few more hours to go and it will be ready for some primer. This area is hard to patch due to blowing holes in the thinner metal around the patch.

This is about 6-7 hours of spot blasting from the photos above.

[mongocanfly]

Well..the spot blaster didnt "create" the holes...it just uncovered them....
It's looking good ..!!!

[ItWillBeSlow]

Originally Posted by mongocanfly

Well..the spot blaster didnt "create" the holes...it just uncovered them....
It's looking good ..!!!

I agree with this assessment

[MP&C]

Originally Posted by ItWillBeSlow

Got the "gutter" and perimeter of the roof area 97% clean with my spot blaster. There is a small amount of rust left in some of the larger pits that I will be leaving as-is.

I did discover some more pinholes on the passenger side - my spot blaster created these while cleaning. I've almost got this patched up. A few more hours to go and it will be ready for some primer. This area is hard to patch due to blowing holes in the thinner metal around the patch.

This is about 6-7 hours of spot blasting from the photos above.

Are those holes more accessible from the inside of the cab (underside) any better than the topside? If you find yourself blowing holes try more wire feed speed and less time on trigger pull..

Another option would be to get a small piece of copper pipe and trim/bend to fit snugly to the area of the pin holes. Then weld to fill the holes using copper as a backer.

Another option would be to cut out the area and weld in a new piece. While you are at this stage it would be a shame to not get all of it fixed with metal/weld while it's accessible (before the roof skin goes on).

[ItWillBeSlow]

Originally Posted by MP&C

Are those holes more accessible from the inside of the cab (underside) any better than the topside? If you find yourself blowing holes try more wire feed speed and less time on trigger pull..

Another option would be to get a small piece of copper pipe and trim/bend to fit snugly to the area of the pin holes. Then weld to fill the holes using copper as a backer.

Another option would be to cut out the area and weld in a new piece. While you are at this stage it would be a shame to not get all of it fixed with metal/weld while it's accessible (before the roof skin goes on).

Thanks Robert. I was able to do this from the bottom/inside. I hadn't thought of the pipe idea, that probably would have saved some headache. I was able to get it done finally.

The two pinholes to the right I was able to weld from the top side, with some copper as a backer on the interior. They filled very nicely.

I put this aside for a week due to work and am getting back to it this week. I hope to primer the new skin and top of the cab this week and get to the skin install by the next week or so.

[ItWillBeSlow]

Today I shot some SPI epoxy primer on the inside of my new skin, and the top of my cab.

I had some fisheye/solvent pop/??? in the thicker spots on my first coat. Was this due to me laying it on too thick? See pictures. Overall it looks very nice. This was my first time shooting actual paint materials through an HVLP gun (Devilbiss FLG4). This was a good practice run for future primer-ing.

I hope to get the new skin installed within the next week.

[theastronaut]

That's normal, SPI doesn't like to go on very wet on the first coat. I still forget and do that from time to time

[ItWillBeSlow]

Got my new skin installed last week. About 50 spot welds on the front and sides, and 3M panel bond on the rear seam. Install and fitment went well.

I tested the panel bond on a couple pieces of scrap, about 1 square inch bonded together. I could not separate the pieces without risking an injury. I was able to get it started, and about half way through the separation stopped. After the small test patch I feel pretty confident in the quality of the bond on the rear seam.

Thanks to Lorne for some additional tips and tricks for using the panel bond. I have about 40-50 hours of work from start to finish in this whole project. Technically speaking, this was no harder than some rocker panels. I appreciate all the comments and feedback in this thread.

[MP&C]

Looks good!!

[nsb29]

That panel bond is tuff stuff I was totally amazed when I did my test trying to separate the two pieces and could only rip the metal. looks good it also sealed your seem I think if I ever did a roof I would consider panel bond all the way around especially on the earlier models like my 65 that way you wouldn’t be relying strictly on seam sealer

[Mike_The_Grad]

3 years to the day and almost same hour as the last post in this amazing thread. Sorry it took so long for someone to come along and share their experience with patching the outer roof skin vs. Replacing the entire panel. I had bad rusted pitted holes along both side outer roof skin on my 72 c10. I didn't have the money for a full replacement panel. And I was able to connect with another member here that only used part of a complete roof skin. I was able to get both sides above the door about 6 inches wide from front to back of cab sent to me for only the cost of shipping. It isn't an easy way to repair or even a good looking way to repair the roof skin. Which is probably why you won't or don't see very many people attempt this repair by patching into the existing roof skin. I may have to bite the bullet and rip the entire roof skin off if I'm not able to get a acceptable finish with body filler and body work. But whatever, it's my truck. Ha ha. Just as with my engine work, if the truck runs great, it's because of me. If it runs like crap, it's because of me. No one else to point the finger at. That's my attitude with my truck. If it looks great, that's me. If it doesn't, that's me. Anyways. Here are some pictures that only confirm everything Robert has been saying throughout this entire thread. The man knows what he is talking about. I'm really glad there are people like him on this website that contribute concise, truthful experiences.

[Mike_The_Grad]

Some more pictures of the roof skin patch on my 72 c10

[MP&C]

Mike, thanks for sharing you roof repairs, they are a challenge at any level and it’s good for everyone to see what goes into the effort. Here’s another resource that shows a good roof repair in fixing someone else’s “botched” chop job that went nowhere. Quite the save, and demonstrates some of the theory i mentioned earlier in this thread.


https://www.garagejournal.com/forum/...ojects.461712/


Here’s my response/critique to his work, highlighting some lessons learned for the casual observer….


https://www.garagejournal.com/forum/...2/post-8782724

[LS short box]

Just a question regarding welding thin sheet metal. Typically the wire used in a wire feed is either .030 or .035. My Miller 211 auto set is designed for that. But .023 wire is available and can be used in my Miller wire feed.
For welding thin sheet metal would .023 work better for reducing heat and warp?
I'm far from the experts above but I help at a body shop a couple days a week mostly just to get out of the house. LOL.
They use panel adhesive for rust rocker repair all the time.
So maybe not a good idea but maybe fab some brackets that could be bonded to the under side of the skin and then panel bond your patch panel to them?

[mongocanfly]

in theory , it takes less heat to "melt" .023, so less heat into your panel..
thats if you can weld it quickly and get full penetration
ive been watching one guy that keeps a air nozzle in his hand while welding, he does a weld and immediately hits it with air to cool it off..
if your gonna run .023 . make sure you have .023 feed wheels for the wire

[Mike_The_Grad]

I've used .023 wire to replace a lower inner door shell for a buddy of mine. It's a lot of work. The .023 wire worked great for minimizing heat distortion just as you're thinking. But also know that you can literally only spot weld with .023. You cannot run a weld for more than a second or two or stringers with it because of how thin it is. Any stick out from the tip just instantly melts the second the trigger is pulled. But that may be because of my machine. It's a lincoln electric from home depot that runs on 220v. It took a little while to get it dialed in but it worked great for doing the door shell repair inside my garage on a work table. I had to dial back the shielding gas from around 25 to about 15 cfh. Because the higher pressure would actually cool the .023 wire before it was able to get any real penetration. I'd imagine it would be a lot more difficult to use outdoors unless a good windblock was setup. Because any kind of moving air would both cool the .023 and blow the lower pressure shielding gas away from the weld area. The .023 is probably also better suited for a 110v machine. Welding machines can be tricky to dial in at the extremes of their abilities be it low or high. Unless you have a good one that allows precise control of your amperage and wire speed. This home depot unit has preset amp selections that are lettered. Some times you need amps in-between these settings. But that's where experience comes in and you have to control your heat in other ways. Imagine spot welding around the entire perimeter of a door shell. It was easily 10 feet in length of welding done spot by spot. Took a while. Ha ha.