Who has experience doing the lower door skin patches?




I am starting mine (for a second time) and have been debating how to go about this.


First I am going to repair ALL of the previous damage, dents, holes, etc. Then move to the outer skins, and the inner lower portion of the door. Is that the proper order?


I would prefer to do the inner lower first, but I figure if the outer is done first it gives you more access to clean up the skin weld if it is butt welded.


My next debate is butt weld vs lap welding. I know butt welding is preferred. The more I have thought about this though, the more a lap weld makes sense. If you were put the flange in the upper existing door skin, and lay the new lower skin on top, it would eliminate any water from setting in the lap seam. Some epoxy in it and it should be sealed with no rust issues from the lap. This would also "double up" and strengthen the entire door skin itself. Most of you know how easily these skins "oil can".


Thoughts???

 

The other issue I forgot to mention was ghost lines. Will lap welding produce them?


Also how do you guys access the welds to grind them flush in the area towards the front of the door? I assume you leave them be, if so are there any ghost lines from the spot welds?

 

Butt welds seem to be the newest idea in welding body panels. When I worked in the auto body field in the '80s we lap welded all of our panels. The first time I saw someone butt weld and hammer weld a panel was at a swap meet in the mid '80s by a high end restoration shop. I lap welded all of the panels in '49 F-2 in the late '80s and although the people who are anti lap welded will say the welds will show when the metal is exposed and heated by the sun I have never noticed any signs. It.s been a long time and the truck is used all summer. Butt welding takes a lot longer to do and I couldn't see any shop I worked in would have allowed us to take that much time to do a repair. When I do lap welds I try to get behind the patch and seal the weld with a paintable sealant. That what I did with my F-2 and my patches have held up very well. Now I'm sure there will be a lot of opinions opposite of mine.

 

I've done them both ways. The thing I dislike about lap joints is it's nearly impossible to stretch the metal back into shape after it's welded. With a butt joint you can beat on the weld and move the metal around. Granted, on a door even that is tough to do unless you remove the entire skin.
Also a flanging tool will distort a crowned panel to some extent.

I have never had a problem with ghost lines on any joint.....

 

If you remove the outer skin and lap weld with an offset flange, you could weld on the back side of the skin. I have not tried this on doors, but both back fenders on my truck got the lower 9-10 inches replaced with offset flanges welded on the back side.

 

When I do a door bottom I lap over almost the entire width of the door except for about an inch on both sides. I remove the original sheet metal to but weld and wrap the new sheet metal around the inner door ebe so I don't have doubled up metal on the edge. It has worked for me many times.

 

If I were doing a lap joint I would not weld it...there are too many adhesive products on the market today to mess around with welding and all the warpage problems it brings to the equation. Take a look at 3M 8115 panel bonding adhesive...once you try it you will never go back to welding. I use a pneumatic flanging tool when crimping a flange, it makes short work of the job and the resulting flange is very uniform and easy to work with.

 

I've never tried the glue, just doesn't seem right but that's just my opinion. I'm kind hard to try new things.

 

Butt welding is not the newest idea in bodywork. That's the way it was done before the days of patch panels, mig welders, and high speed, low quality production repair techniques. I've seen and done both ways. As Scott said above, the panel is easier to work with a butt joint than a lap joint.

Removing a skin from a door shell almost never works. You have to un-bend the flange from around the shell which typically distorts the skin to the point that it's difficult to impossible to re-use.

 

It may be new to you but it is not new to the automotive industry...structural adhesives (not "glue") have been in common use for decades. Ever wonder how GM makes the bond between a fiberglass Corvette body and a metal frame? Ever wonder how Ford bonds fiberglass bedsides to a metal bed? Japanese companies have been shipping mini trucks to the US and other countries for decades with the bed components painted but unassembled. At the point of entry the beds are assembled using structural adhesives and then installed with perfectly matching paint jobs at the port of entry.
Lots has happened in the industry since the 80's...

 

I understand there are mega adhesives. I just saw an old episode of Modern Marvels on Mega Adhesives. One example was a sky scraper, I think in Australia that the outer stainless or aluminum panels were glued to the structural steel. They tests showed the outer skin expanded and contracted more than the steel under it and rivet would just have popped out and failed. Maybe some day I'll try the glue.

 

I would butt weld the lower door, only because from my experience with a flanger tool it will try and straighten out a panel that has any curve to it. Butt welding is not hard, just lay the patch over the panel, scribe a cut line, and remove the rusted section. I like to sneak up on the cut line so I dont go too far.

 

How would you clamp the panels tight enough on a door skin while the adhesive sets?

 

FOR YOU BUTT WELDERS, HOW ARE YOU FINISHING THE WELDS ON THE BACKSIDE. YOU CAN ACCESS SOME OF THEM THROUGH THE ACCESS PANEL, BUT THE FRONT 8" OR SO IS NEARLY IMPOSSIBLE TO GET.

 

I use phosporic acid in an old spray bottle to hit rusty areas that I cannot get with a sander or wire brush, wipe off with wax and grease remover, then seam sealer, then paint.
There can be no pin holes in the welds or any filler you skim on will eventually bubble and lift. If air cannot get to the filler it will last indefinatley.

I have not tried the adhesive yet but I have read that it is only good for structural points that will not be seen, and if used for panel joints there will be a ghost line in the paint where it was used.