All good info, guys. And thanks for reposting your method here, frederick. I still like the idea of flanging the existing metal, mostly because I don't think I have the patience/skill to do it the way you did. Given that approach, how about a combination of glue and spot welds? I could glue most of the panel in place, leaving a few strategic locations without glue and spot weld them through punched holes in the patch or at the edge of the patch (taking care not to heat up the adhesive). Then spot weld the entire lip of the patch to the lip of the inner well (rather than bother with any glue). That would offer some corrosion protection as water/mud would be less likely to enter the lap, and there would be some structural integrity as a result of the spot welding. Either way I've got to get off the computer and get started on it.

Apart from where it is rusted through, my inner well looks to be structurally sound so I think I'll patch it by spot welding a new piece in.

 

I guess give it a shot, never tried it. I weld in my patch pieces. Gluing the majority should give you less finishing work, no welds to grind and less chance of warpage by welding a seam solid. rustproof the back side of the repair the best you can, and use a weld through primer on your overlapping lip. Weld through isn't that expensive. I don't think that inner wheelwhell is quite as big a part of the structure as a unibody car would be, but adhesives still aren't recommended for panels considered structural. If its weakened by rust, spot welding in a new piece can't really make it any worst, but I think I would weld that patch in solid, skip the welds around and allow plenty of time not to build up heat. I would also get inside the wheel well and apply some panel adhesive or 2k seam sealer along the turned under edge of the patch(the part you plan on spot welding) where the joint is between that and the inner piece you are overlapping to prevent water from splashing up inside that seam. Do you know what adhesive you plan on using? Some of the guns needed to apply can be pretty pricey to buy. Sometimes If you buy many tubes of adhesive at 30 bucks a pop they will give you one, but think the cheapest gun is around 50 bucks. When I was looking they wanted 100 bucks for everyone I looked at, so I just did some modification on a caulk gun to get me by. But you want the ratio of the two parts to be right.

 

Welding, even spot welds, bonds materials by melting them together, sometimes by adding filler rod or wire. You're melting the metal. Structural adhesive used in automobiles and airplanes are heat resistance, however not to the point where the base metal is hot enough to discolor. So spot welding anywhere near adhesive will result in the adhesive losing it's "grip" on the metal and falling off, if not that instant, it will in the very near future.

Adhesives can be used for structural components, I have to disagree with whoever said this however there are special adhesives for this. And, proper prep of the materials to be bonded is very intensive for the average "monkey mechanic" like us. When you're assembling cars using a precision robot managed by sophisticated mainframes, well, you can prep those areas appropriately and consistantly.

Welding in my opinion is the only way to fix this. If you don't have the confidence, that's okay. I didn't! So just cut scraps off the patch panel, or find out what thickness (gauge) the panel is and buy a $5 piece of that at lowes or home depot, and rip it through a saw into smaller pieces, and practice. It's worth the hour of wasting $5 worth of scrap to get the right settings on the welder, and the "feel" into your fingers/hands. Then do it for real on your truck, and your results will be better than "reasonable".

Mine didn't come out perfect, and that's what the skim of thin body filler was for.

Flanging works well too, but you need the tool, and a really strong grip which I don't have. My hands wave all over the place. I've never laid a straight mig bead in my life. Not one. I simply hide this fact through liberal grinding

 

Well, I cut my patch for the bedside and clamped it in place to check the fit. The patch is going to require a little shaping. It's ok around the top, but where it gets close to the lip of the wheel well, it needs some work. Even after throwing around all these ideas and discussion, I've still not made a decision to glue or weld or both.

Before I commit, I'll call around to see what adhesives are available locally and check prices of the application gun.

I may just do as frederick did--weld it all up and shoot some rust treatment in through an access hole. Whatever I do, I'll post it in here along with pictures. If it doesn't work out well, then everyone will have a step-by-step method of how to do it wrong!
Thanks again!

 

fred--I found an inexpensive air powered flange/hole punch tool for $30. Seems to work OK, but wish it came with interchangeble heads for different thickness as the flange could have been a hair deeper. Makes nice holes, though.

 

Here's the patch clamped in place. I have to buttweld the area where the lip turns up to the bedside because I couldn't flange it properly. Unfortunately I have a larger-than-hoped-for gap between the panels. I don't have a welder at home, so the next update on this repair might be a week or so. Thanks for all the suggestions--they're very much appreciated.

 

you can cover both sides of a butt weld..I've screwed a couple of them up lately but am getting it down. I plan of using the expoxy primer then poly bedliner on the backside- will have to get creative on a couple of them. I'm ready to epoxy prime the bronco- got the welds ground down- will do the filler after the epoxy to get the best protection- ck out the tailgate in the gallery...now thats screwed up- still not sure how to attack it.

 

can't edit on this machine. Best advise I ever got was to get some of por 15's 'metal ready'. Its acid that kills the rust and helps prepare the metal (etch) for filler or primer..can't tell you how impressed i am with that stuff. You can easily feel the etch it puts on metal.

 

Looking good. Very good.

 

Update on my progress (if you want to call it that). I had only about 1/4" of overlap in some places, so the paint shop I went to (to purchase the panel adhesive) talked me into welding it. I bought an inexpensive mig welder and butchered it up pretty bad. Not only will I not win any awards for welding, but I let the sheet metal get too hot and wound up with some warping.

It's not too bad and certainly nothing Bondo can't fix, but it is VERY frustrating.

 

happens to everyone. If you are using a flux cored welder, that makes things a little more difficult. You need to really take you time welding and not build up heat. Weld sort sections and skip around where you are placing your welds. Another trick I heard is to place wet towels around where you are welding, or htp makes a product called heat sponge. I have not tried it yet. The first door I welded up on my bonny which is the first time I really did quite a lot of welding of patch panels using a flux core, I warped it pretty good. Had to use a bit of fiberglass filler on that. But did much better on the other doors and other cars I patched after that. Everyone gets frustrated. I am about ready to hit something right now. I am working on a hood that should have been a simple repair. The first time I went to paint it I had it all in base. Went to clear and after edging some of it, the gun didn't want to spray right. I grabbed my siphon off the wall that I used many times before, and the clear was laying out nice, but when I was just about finished with the first coat of clear, I got a big puddle of clear that came somewhere from the gun, and proceded to move the metallic in the base in that spot. So sanded it down and painted it again thursday. It went on good but when I came back somehow there was an area where the base had made a dark spot, guessing it must not of sat long enough, but I let it flash off quite awhile. So then I am running out of material, but managed to fix so it wasn't real noticeable. Didn't have enough clear to spray the hole hood another coat but since it was still fresh, I figured it would melt in fine. Well it did fine, but I got a run when finishing clearing. No problem, Ive buffed out worse before. Buffed it out this weekend and the majority looks really good. One problem, I buffed through the clear where I sanded out the run. Tryed fixing it this weekend and the base I have left is darker for some reason, and I can't get a good blend. I've been painting awhile, but I don't remember having this many problems before. There were more, like my touchup gun braking and other fun stuff. I am at the point now where I am gonna let it sit for a little while and go back at it fresh when I've cooled down a little, and I have to buy more material now. When it rains it pours I guess.

 

I've found that very aggressive grinding can remove a lot of bad welding- which is a good thing!!!

 

Actually, if I can ever learn to properly shape Bondo, it probably won't look that bad. However, I'm convinced that Bondo is an art, and I'm no artist. Think I'll make that my signature line.

 

My signature isn't showing.

 

Tips for working with bondo. If you have a larger area to fill, In the preliminary rough out work, if you catch the plastic filler while its still just a little soft, it will be easier to shape, but does clog up the sandpaper some, just slap it with a paint stick to get most of the paper. I usually do this to get a good part of it sanded, just make sure you aren't tearing to much away, and it won't feather well until its hardened up more. Work with 36 grit to get most of it straight if you have quite a bit to sand off and shape, worry about the scratches later after it straight by going over with 80 grit and 180 grit before primer, or applying a tight skim coat of filler over the whole area, and sand that with a finer grit. Its harder to get things straight if you are sanding with too fine a grit paper. Someone new to filler work, it may help some if they guide coat the filler to help identify when the high areas are being worked out and what areas are still low and have the guide coat still in them. 3m makes a powder guide coat you could use for this. Spread the filler a ways past where the actual repair is and feather it in, don't just try to fill the spot. Or you could feel for the worst lows and get them filled and sanded first before spreading a coat of filler over the whole thing and past the area needing repair. Work with the largest sanding board or block that can be worked in the area you are doing, and sand in x patterns across the whole repair area until it is feathered out, unless you have a small area you have to work down more. If I have a fairly low area, but the rest of the filler feels straight, I will fill that and a little past that area, and catch the filler while its still a little soft so I am not cutting down the filler surrounding the new stuff I applied while sanding it. If you are making a bodyline, you sand straight along the body line on top, and under. Using masking tape just under or over the line and spreading half at a time may help, and also may help if you use some masking tape as a guide for where to sand and recreate the line. Try to get use to feeling what is high and low without looking at it. Feel with your whole hand flat out with your fingers together, and try to tell where you feel your hand bump up or dip without looking at it. I usually use a pencil and mark whats still high with an x and circle my low spots. Some people say using a thin cotton glove helps them feel stuff better, but I don't use one. Sometimes I think I feel more then I should and primer would take care of it. A high build urethane primer will feel minor low areas and 80-180 grit scratches. A polyester primer is almost like bodyfiller in a can, but you need a spray gun that can spray it.