Re: Roof patch causing warp / oil canning
 

Thanks for the detailed help here !!! MP&C you could almost write a book with your great detail and Pics! Great info.

Re: Roof patch causing warp / oil canning
 

I think the idea of using metal bond would be my choice. The idea of cutting a hole in the inner cab is only going to create more work, if the backer is kept to a minimum amount of overlap and you use slick-sand as your high build primer chances of having ghost lines would be slim to nun.

Re: Roof patch causing warp / oil canning
 

Thanks for the continued discussion. After some more research on the metal bond, it does seem this would be the simplest solution. This brings me to a few new questions as I plan to explore this direction further:


- Should I stick with my current ~2" square patch, or open the hole to be circular if using metal bond?

- Do I need to leave a small gap around the perimeter of the patch for the material to bond the edges, or do I want it as tight as possible?

- When placing a backer, do I want "space the backer" down toward the inner roof, so that there is a small gap between the backer and my patch for the bond material to fill? Or does it need to be completely flush? It seems if it is flush I will not get the patch completely flush with the roof line without pushing 100% of the bond material out of the joints. Clamping the backer in place first will also be a challenge, a tiny C clamp should do it but I am open to recommendations if anyone has tried a similar application.

- Can anyone elaborate more on the ghost lines, and why these are a risk? I planned to sand/grind all the joints, skim coat with bondo, epoxy, high build, then paint. Im not understanding how this patch would be different after it is prepped like the rest of the cab.

Thanks again everyone

Re: Roof patch causing warp / oil canning
 

I 2nd that! Much to be learned here and it is very cool people are willing to take the time to hand out free advice

Re: Roof patch causing warp / oil canning
 

This video shows a reflection in the rear tailgate of a 54 wagon, the owner had done a nice job of restoring it, the car was neat as a pin. The only flaw was that he had used a stepped/flanged repair on the patch used on the lower tailgate skin. You can see the exact location of the seam, despite the filler used, and you can even pick out the screw holes that were plug welded closed. The other patches on the car were all butt welded with no discernable ghosting. I was given permission to take and show the video in hopes that others could learn from it and take prevention steps.


https://www.youtube.com/watch?v=OGhFEfVqxb0


This occurs because you have two thicknesses of metal to one side of the weld, and a single thickness to the other side. Two thicknesses will take longer to heat up when exposed to sunlight (think car show) and longer to cool down that evening than the single thickness on the other side of the weld. This differing expansion and contraction rate will cause a ghost line right at the seam, showing exactly where the repair was made. So when I respond to various patch panel welding questions, this is also why I stress to grind welds on both front AND rear of the panel. We need the panel thickness consistent to help eliminate the cause of ghosting.

Re: Roof patch causing warp / oil canning
 

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

Re: Roof patch causing warp / oil canning
 

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.

Re: Roof patch causing warp / oil canning
 

I'll add a bit more to the discussion.
First a question for Robert...Was the tailgate you showed in the video for sure mig welded solid? Ive seen some things like that before (glued, Lenco spotwelded along the edge & some tacked every couple inches that you could see EVERY weld & gap), but never a fully welded seam to that degree of ghosting. What I have seen several times (which if it was done on a big long seam like that, I can imagine it looking very similar) is the weld has a side (or both sides) with a real bad "undercut" left along the weld. An example would be a guy closes up the gas filler hole in the truck cab corner by laying a patch in behind & welding around the hole. Once finished, the INSIDE edge of the weld shows the "step" after some time in the sun because of the drop-off...the outside does not because it was able to be easily ground smooth with the original metal. One very good reason for your insistence of the butt-welding panels. Like you mention, you go to a car event on a hot day &/or as the sun is going down & dew is starting to set in...you see some interesting things!

To add to what Robert said about the question about how/why the ghosting...at least with using panel bond, I think there is another factor, but really all the same reason Robert stated & that is, simply the difference in the makeup of the items heating, cooling, ect at different paces & react differently to heat, cool cycles...we have a sharp cut metal edge of the original panel, we have a sharp cut metal edge of the patch...in between/around the edge is a very good insulating item (somewhat like a plastic material). See where Im going?

So what to do to minimize the ghosting? I have found a few things that go the right direction to minimizing the chances. First, you taper off the upper square edge of the original metal & the patch...similar to what doing drywall would look like. Second, As I mentioned earlier, I prefer the Fusor 208. It dries harder & is more solid than the "panel adhesive" products like 108, 110 ect. which is really more a metal glue intended for flanges which stays slightly "gummy" & can never really be feathered out.
This part is going to make Robert go take a blood pressure pill, but as I stated earlier...Im a realist. Body filler is really a friend to nearly everyone until they hone skills in like Robert has. So here it goes...Don't try to make it "too good". Yep I said it! What Im getting at is this. I promise you if you work real hard & make your pieces real close to flush not needing/having much room for "glop on top of it" it WILL ghost line on you. If you have room for a uniform coat of hard base filler like Duraglas, all-metal, something of "insulation" on top of your patch, the odds are much reduced you see a line. Just like nsb stated, a polyester primer is also my choice (Clausen Sandy or Rust Defender is my pick). I distinctly remember one of the Roofs I did years ago on an Impala. The local department had a car & wanted to make it an undercover detective's car. It started out Black & White with lights, antennas, ect. & ended up all White with pinstripes, mudflaps & full wheel covers...looked just like grand paps ride! I grabbed a pick hammer, tapped down the mess the last guy made drilling & mounting the stuff & glued plates over a couple holes on the roof, one on the trunk & an oval on the post from the spot light. That car was back in the shop for a deer hit & someone backed into it years later...couldn't find any of those spots, not a flaw to be found years later. It sat outside everyday, but it was White also. What Im getting at is: "The Roof was ruined by the guy with the drill", I made it better even if it would have shown a ghostline...no one but a trained eye was going to find one if it was there. One of the neat things of over 30 years "practicing" auto body repair...you get to try/see how things work out or dont work out. Lorne

Re: Roof patch causing warp / oil canning
 

Thanks. I am definitely not chasing perfection with this repair, and I am already making the truck 3x nicer than I ever intended to. I am honestly more concerned of a future crack or failure with the metal bond, than having a ghost line. This is an area that's hard to see on a truck anyway, and I would likely forget about it in no time. However, I do want to make sure I am following all reasonable steps to make sure its a durable repair.

Do you have any comments to my sketches above with the backer? My core concern is a small backer strip leaves little surface area for the original roof skin and the patch to all mate together. Do these strips need to be wider? Should I space it down to allow more room for the bond material to fill the void and not squeeze out?

Re: Roof patch causing warp / oil canning
 

First I'd like to say thanks for all the kind words, but I fear you guys overestimate my skills or abilities. :lol: I've had quite a bit of metal thrown into the scrap pile, serving as quite the lesson of what not to do. Have also had to strip down a paint job due to overeager application of Ospho by the owner into pitted areas, and me spraying epoxy primer directly over top of it (having no prior experience with Ospho). Sunlight over the course of the first year of car shows reactivated the deposited acid in the pits where it was now outgassing and we had small 1/8 and smaller circles where the epoxy was delaminating above these pits. ..

But I am a rather fast learner, and tend to offer opinions to help others capitalize on my learning curve. So when people start singing praises of using Ospho and other such snake oils, I am quick to offer my insight. Many of the proponents of these products simply are amazed by the minimal amount of work needed (ie: shortcuts) and have recommended product based on this and not much else, as most were still sitting in bare metal in project stage.. Lorne, this is what really get my blood pressure going ;) .. People giving half ass recommendations that haven't finished the job to know the full story yet. Hey, I get it. We humans are lazy, and looking for an easier way, so that's why so many of these short cut products are sold. But that, folks, is why Robert is so damned opinionated.. :lol:





Here's the answer from the horse's mouth. Yes, I asked him to clarify once before and this was his response. Names changed to protect the innocent/unknowing. He also spoke of his experience with adhesives, and I am leaving that as well, perhaps you can speak to that based on your experiences....







Lorne, thanks for adding your experiences here with the adhesives, I agree fully that sometimes another method may be in order, and that is the decision the owner must make in each circumstance. Sometimes you get people that don't want to share with others what didn't work as they don't want to admit "failure", or whatever the reason. I see those as a learning moment, and would feel remiss if I didn't share, especially given the costs today of paint and supplies.






I do not have personal experience (disclaimer) but what I have read is that any seam should be clamped tightly. I would interpret that as meaning the joint may be stronger as a thin film between the two panels, and not used as a "filler". It may be, based on the roof repair on the 34 Chevy written above, that too much of a gap and the adhesive does it's own shrinking which pulls the area downward.. My thoughts are that the spacer is going to weaken the joint. Perhaps Lorne can share his thoughts on this as well..





.

Re: Roof patch causing warp / oil canning
 

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..

Re: Roof patch causing warp / oil canning
 

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.

Re: Roof patch causing warp / oil canning
 

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

Re: Roof patch causing warp / oil canning
 

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

Re: Roof patch causing warp / oil canning
 

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..

Re: Roof patch causing warp / oil canning
 

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.

Re: Roof patch causing warp / oil canning
 

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


https://hosting.photobucket.com/albu...s/HPIM5193.jpg


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







.

Re: Roof patch causing warp / oil canning
 

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.

Re: Roof patch causing warp / oil canning
 

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.

Re: Roof patch causing warp / oil canning
 

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.

Re: Roof patch causing warp / oil canning
 

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.

Re: Roof patch causing warp / oil canning
 

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

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.

Attachment 2095944


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.

Re: Roof patch causing warp / oil canning
 

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

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.

Re: Roof patch causing warp / oil canning
 

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.

Re: Roof patch causing warp / oil canning
 

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