Roof patch causing warp / oil canning

[ItWillBeSlow]

Originally Posted by nsb29

I don’t think anyone is better at this than Robert and what he is telling you is 100% correct. In your situation and neither one of us having the skills that Robert has I still think metal bond is the way to go. I don’t think it matters whether it’s a round hole or a square hole just keep it to a minimum, if you use C clamps to hold your backer in place just don’t make them so tight you squeeze all of the adhesive out and then do the same with the patch it should equal out. The one thing I believe in 100% is to use a polyester high build like slick sand which has zero shrinkage as opposed to a 2K primer which will minimize if not completely stop any ghosting

Thanks for the response and I do agree the more I learn. As stated earlier by someone else, if a small ghost line in this area is my worst issue here, I will consider this more than successful.

When I think about the best way to do this, I believe it would be best to space the backer to allow the metal bond some room to fill and not completely squeeze out. I made a diagram of this below.

Please keep the comments and experience coming, I plan to tackle this within the next week or so and would like to iron out a couple of these details. I think the backer strips will be about 1/3" thick to properly attach the roof panel and provide a lip for the patch. If there are other thoughts please share.

[mongocanfly]

Robert...to. circle back to his original issues...how do you "correctly" patch a area like his when you have no access to the back side for hammer and dolley...
I know I had the same issue when I made the cab corner patch for the IH...I pretty much had to live with it the way it (warped) from welding...i could and did knock down the high spots, but without being able to get to the back I couldnt hammer and dolley it flat..
I really saw how well hammer and dolley worked when i did the fender that Dan helped me with..so I'm sold on that..

[MP&C]

That "correctly" is a severely loaded term. One would have to see the panel first hand to weigh all the options. In many cases you'll find rust issues above a drip rail or above the windshield that stem from condensation gathering on the inside of the panel. If there were any such indicators at all, one might lean more toward a new roof skin, kill two (or three) birds with that one stone. If the steel headliner could be removed or even pulled down on three sides by drilling out spot welds, that may be another option for less expense in replacement sheet metal. Based on someone's lack of a welder, or perhaps metalworking skills, or ??? it may be the best option to use adhesives. Again, each circumstance would be different. If a truck was on bags and going to be slammed on the ground then one may be more concerned with a ghost line on the roof skin and pick a different option than if it's a lifted 4wd where any ghost line is far from being seen.

[ItWillBeSlow]

Originally Posted by MP&C

One would have to see the panel first hand to weigh all the options. In many cases you'll find rust issues above a drip rail or above the windshield that stem from condensation gathering on the inside of the panel. If there were any such indicators at all, one might lean more toward a new roof skin, kill two (or three) birds with that one stone.

Id like to get more into the question asked by Greg, and the partial response quoted above and get some opinions on my greater cab situation.

I had 3 pinholes in the top roof skin, that I was able to make "pea sized" by gouging the weak metal with a screw driver. I also had a small pinhole behind one corner of my windshield that I also gouged to be slightly larger. After cutting this area out, I had a deposit of rust flakes in the corner. I also had a small pinhole area in this same corner in the flat metal above the door frame.

I also have some surface and lightly/mildly pitted rust in other areas above the doors and behind the windshield, but it seems to be superficial and I cant poke any holes.

Ill post a few pictures to back up this description, some are in-repair or already done.

My questions is - what is the likelihood I would continue to get additional rust coming through future paint? This truck will stay dry, and has for the last 20 years or so. I believe most of the rust issues developed the first 3 decades of this trucks life.

Most

[ItWillBeSlow]

More photos to support the above post: front corner behind windshield

[MP&C]

Likelihood is 100%. Looking at the second picture in your post #38, those rust holes are not from leaves in the drip rail, they are rusting from the inside-out. Over the years humidity has formed inside the truck as it sits in the sun with the windows up. When it cools at night this humidity becomes condensation on the bottom side of the roof skin, where it will pool and collect to the low areas once gravity helps out. What you have showing is normally a small percentage of the rust and pits that are still growing and will be breaking through in the next year or so. If you have priced your paint materials, then I'd say you fully understand how much cheaper this repair will be before paint goes on. If they reproduce a roof skin for your truck I'd say you have a prime candidate now. And it fixes the antenna hole..


For some insight, John has a similar repair he's doing right now on a 66 ford here:


http://www.67-72chevytrucks.com/vboa...=784498&page=7



….starting at post 164. This will give a good idea what lies in store. Where he reformed the lip, you shouldn't need to do so with a reproduction roof skin... And while things are opened up, fix everything that needs it..

[ItWillBeSlow]

Originally Posted by MP&C

Likelihood is 100%. Looking at the second picture in your post #38, those rust holes are not from leaves in the drip rail, they are rusting from the inside-out. Over the years humidity has formed inside the truck as it sits in the sun with the windows up. When it cools at night this humidity becomes condensation on the bottom side of the roof skin, where it will pool and collect to the low areas once gravity helps out. What you have showing is normally a small percentage of the rust and pits that are still growing and will be breaking through in the next year or so. If you have priced your paint materials, then I'd say you fully understand how much cheaper this repair will be before paint goes on. If they reproduce a roof skin for your truck I'd say you have a prime candidate now. And it fixes the antenna hole..


For some insight, John has a similar repair he's doing right now on a 66 ford here:


http://www.67-72chevytrucks.com/vboa...=784498&page=7



….starting at post 164. This will give a good idea what lies in store. Where he reformed the lip, you shouldn't need to do so with a reproduction roof skin... And while things are opened up, fix everything that needs it..

Thanks Robert. One thing I don’t understand is the practical risk associated with the rust that’s inside. If it took 50 years to make the first 3 pinholes, and I remove these “worst” areas and keep water out, then keep the truck dry except the occasional wash, what is the practical risk of rust breaking through again in the future? To me it seems removing the major contributing factors should reduce this risk.

I’m obviously not building a Barrett Jackson truck here, but I am also doubtful that most folks with decent paint jobs replaced a roof skin over a few pin holes, but I am wrong often and that’s how this discussion started!

Any others have past roof skin repairs to share? I may have access to a probe camera and will try and get some interior shots of these areas just for kicks.

[MP&C]

This is a roof repair I have done. The outside had half dozen or so pinholes.. This was the inside..





Given your circumstances, you will likely have similar, and when you weld you will find the thin spots and also find it challenging to weld up due to blowing holes from the thin spots that are hiding. Also, to speak to how dry you plan on keeping it, when you start welding in the vicinity of a deep, scaly pit that is hiding on the back side, the weld activity will awaken such pits that you'll see them again within 2 years, dry or not. It is cheaper to fix now before wasting paint on something that is going to rust through..



Here is a thread on the entire repair. Note the dark grey circles in vicinity of the visible pin holes. This is a tell tale sign of a deep pit getting ready to break through in short order.


https://www.trifivechevys.com/showth...f-rust-repairs







.

[ItWillBeSlow]

Originally Posted by MP&C

This is a roof repair I have done. The outside had half dozen or so pinholes.. This was the inside..





Given your circumstances, you will likely have similar, and when you weld you will find the thin spots and also find it challenging to weld up due to blowing holes from the thin spots that are hiding. Also, to speak to how dry you plan on keeping it, when you start welding in the vicinity of a deep, scaly pit that is hiding on the back side, the weld activity will awaken such pits that you'll see them again within 2 years, dry or not. It is cheaper to fix now before wasting paint on something that is going to rust through..



Here is a thread on the entire repair. Note the dark grey circles in vicinity of the visible pin holes. This is a tell tale sign of a deep pit getting ready to break through in short order.


https://www.trifivechevys.com/showth...f-rust-repairs

.

Thanks Robert, that is an interesting read. I am leaning toward doing the whole roof skin at this point the more this thread evolves.

I think I could handle the task, however I am not sure how to cut the rear seam at the skin. Since I would not save mine, I believe I could cut 1" in front of the seam across the back, drill out the drip rail spot welds and take most of the skin off. Then I would have access to the spot welds on the rear lip to get the last rear 1" of the top skin off.

I am also mildly concerned about aftermarket panel quality. This would not be a "cut and hammer to fit" type panel as with rockers, etc.

If you or anyone else have experience with replacement skins please share. There is not as much information out there on this fix as with other metal tasks on these cabs.

[ItWillBeSlow]

I decided to move forward with the top skin replacement. Picked up the panel yesterday and cut out the old one today. About 2.5 hours to get the spot welds out, and I cut a straight line right in front of the rear seam so far. Still have to get the spot welds off the remaining short strip.

The verdict is: not as bad as I thought, but glad I did it. There is surface rust on everything, a mouse motel, and a lot of nooks and crannies to be wire wheeled and treated. I have 2 small pin holes I hadn't noticed on the interior skin right beside/under my passenger weather stripping, I am unsure If I will fix these or treat and fill.

The top skin definitely has some weaker areas near my previous repairs, you can see this in the photos.

Here are some raw photos before I cleaned out all the crap. The major areas like under the windshield (rats nest area) appear to be very solid, surprisingly. Cant test fit the panel fitment until I get the last strip out of the back seam.

I do need some more input on the metal bond from anyone with experience. I bought a tube of fusor 208b ($50) and the fusor part number gun/dispenser that fits this tube ($75 ). The dispenser is back ordered. This is a 300mL /10.1 oz tube, is there a universal dispenser I could use? Preferably a cheaper one.

Also looking for recommendations for what insulation/sound deadener to put back down.

[ItWillBeSlow]

I plan to also hit the pillars with eastwood internal frame coat/rust encapsulator now that I have access to everything. I will probably POR15 most of the top area. Here are a few pics after vacuum and a few minutes of wire wheel.

[ItWillBeSlow]

Test fit panel today. Looks pretty good so far, maybe the best repop I have bought.

There is a 3/16" hump in the middle of the rear seam where it wont lay perfectly plat. Needs about 10# pressure to hold it down flush with the seam. May get better once I clean up all the joints properly, I plan to strap it down during the cure to hold it solid.

I was planning on bonding the rear seam, and welding the front and rear sides. Please share if anyone has input for otherwise.

[MP&C]

First off, congrats on filling the antenna hole, can't even see where it was anymore..

Next, consider who you're getting advise from here, take it with a grain of salt, your truck, your decisions, etc..

I haven't used the panel adhesive to speak from a position of authoritay. But what I have read is that the panels that are being glued? together should be clamped tightly across the entire seam where the adhesive is being used. In my interpretation, clamped tightly means there will be minimal adhesive between the two panels for maximum strength, vs looking like someone got happy with a caulking gun to fill a void. It also means that with the (steel) headliner still in there and in the way, you're not clamping jack together. So no "proper" use of the adhesive is possible. You already know what's coming next, this is Robert, after all.

My thoughts are to remove the headliner and rear window surround in their entirety, KEEPING THEM ATTACHED TOGETHER, by removing spot welds around rear window opening, around door opening, around windshield opening, and across bottom beneath window.




SIDE NOTE: Part of the support of the rear cab panel that attaches to the roof in the back is the crown of the roof skin. So where you see the roof skin needing to come down, I see the rear section needing to come up to meet the roof skin, or a meet in the middle. You take the old roof out, and it removes some of the support where the top center of the rear panel may tend to drop on it's own accord. But of course, I'm looking at color 8x10 glossy's on my screen here, so the final determining factor is what you see in front of you and how the panels react as you bring them together.


Next, before welding the outer skin in place, repair any of the gutter, bracing, A or B pillars, etc now that you have ready access. Now you can properly position the outer skin, clamp to the rear section as needed, and perform spot or plug welds to attach as needed. Then repair any damage to the headliner assy before aligning it back inside and welding back in place.


For the dual cartridge gun that you'll now need for seam sealer in the drip rail, keep looking. I paid 39 for mine. 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.

[ItWillBeSlow]

Thanks for the feedback Robert. I will say that further disassembly of the cab and interior is not particularly appealing to me right now

I do however think/wonder that an additional clamping method could be worked up using j-hooks or a similar small clip. Attaching a hook to the back panel lip, that the new panel lip could "slide under" after applying the metal bond, would help provide some actual clamping force, and a mechanical attachment that would prevent lift or at least reduce risk that the bond could break over time. I recognize this is not by the book or per the instructions of the panel bond, however it may be practical.

I may also start a dedicated thread on this topic in the main section due to the low traffic in this forum, and how this topic has shifted from the original thread intent. The fact that this panel is reproduced means there are at least a moderate amount of people performing this repair - surely there are a few more lurkers here who have done it.

[tinydb84]

I hope I never have to do one of these repairs but I am thoroughly enjoying the read.

Best of luck to you getting it done perfectly. Looking good so far. My only input is to not use por15. I have had bad luck with it and seen far too many similar stories.

[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

[nsb29]

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

[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!

[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.

[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.

[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).