"new guy" - lurked here a long time, never got around to registering, however with the board flipping over figured now is as good of a time as any. I'm sure some have seen me pop up from time to time at the Car Lounge and various rod & custom sites. I'll be surfing / lurking here more often as I've finally had my fill of useless new car drivel and want to read / focus more on builds.
Anyway. As it sounds on the title, this is how I replace rotted out door inners and rotted out lower door skins. The doors are off a '62 GM panel truck. If you don't know what one is, here's the truck.
Start out by gutting the door down. If you can't gut figure out how to pull the trim panels, window / regulators / etc. out... chances are you shouldn't be screwing around with a door skin. If that's the case... stop now. Pay somebody to do it. You'll thank me later.
First thing is first, check to see how the physical skin itself is attached to the doors. Nowdays it's common for the skins to be affixed using a few spot welds on the flange and panel bond adhesive actually holding the skin to the inner structure. These were built 45 years ago.. that ain't the case. These flanges are hemmed, and there are a few welds actually holding the skin to the structure. No biggie. I'm skipping some steps here, as I'm replacing the lower section of the inner, and I can get away with only doing a partial lower skin, as the rest of the door is fairly solid (save for where the goobers mounted those god awful truck mirrors, and the stock mirrror holes, along with where they dented the hell out of the thing by not installing the stops and obviously opened the door just a BIT too far... on both doors. Stooges.
Once your doors are gutted down, pop 'em onto a fender / body stand, table, whatever you use. I use a combination of fender stands (500lb units) and work tables. Depends on what's being done.
Anyway.
From there MEASURE and write it down, and MEASURE again. I really can't stress this enough. MEASURE. You will be using these reference measurements to align the new skin and inner door structure - which will ensure the thing actually fits up like it should and WON'T need "adjustments" with a dead blow to fit in the hole.I've seen folks do that more often than not... I don't like to fly that way, personally. In this case, I'm sectioning in the inner structure 3 1/4" up from the bottom edge, which puts it a 1/4" below the lowest bead rolled line on the door structure. The patch is larger, but the door is solid from there down, and I'd rather not muck with the bead rolled lines, as the patch panel is about a 1/4" off as far as the overall goes on the bead... so I'd rather keep 'em 100% stock, and just section below that point.
I take overall height, width, diagonal, inset to jamb, etc. measurements, and write them down. I measure EACH door as back then tolerances just weren't what they are today. I also make sure and hang the doors and adjust my gaps to where I want prior to popping the door off, as that way if I see I need to bring the lower edge down by an 1/8" to tighten up the gaps, I can. My goal is better than factory, always will be. I used to get yelled at for doing the occasional collision work that I was kicking the thing out too flat and too nice. Needless to say, I got out of doing collision real quick.
This is the reason for re-skinning. The other door was actually a lot worse than this one
Nothing too crazy, just rotted through in various spots.
If you are just reskinning - follow this. If you'll be doing the inner as well - I personally just split the skin without cutting across, and then replace the inner, then cut across and finish the skin job. If that makes sense...
First thing is mark off the area where you'll be sectioning in the new piece. Then I personally cut the outer skin first, then drill out the spot welds on the hemmed flange (if any), being careful to not drill all the way through, just drill through the OUTER flange, leaving the inner structure in tact. This is especially important if you are just re-skinning the door and NOT screwing with the inner structure. I have a multitude of options for drilling them out, everything from specialized spot weld cutters on up through bits you can chuck into any drill.
From there, grind til you "split" the skin from your cut line down - they'll become 2 different pieces. The outer skin is hemmed over the inner structure, forming a U shape over the inner structure - grind the top of the "U" off until you expose the 2 different panels. DO NOT however grind into the inner panel - ESPECIALLY if you are not replacing it. That's a BIG NO GO. From there I personally use a panel separator, however you can get away with a hammer and cold chisel slowly working your way around the now split edge to separate them.
Unfortunately the inner brace that connects the lower hinge to the bottom of the inner panel was rotted out, so that got cut off and I'll be scratch fab'ing one and welding that in, then installing the inner replacement panel and plug welding the new brace to the skin, just like factory. See the factory theme keep popping up? My goal is 25 years down the road if the car is in somebody else's hands to let them be able to rip into it and not be able to tell where I was and what was done.
As I'm doing the inner, like I said I just split the hemmed flange, and then went about cutting the inner. I cut the lower out, up until the lowest bead rolled bodyline in the door, as it was rotted out just up to that point.
This is what I wound up with.
And the cut rotted out panel
From there, as I had full access to the inners I decided now would be as good of a time as any to clean up and treat the insides, having full access and what not. I didn't prep to the edge of the skin, as that's all getting lopped off, however I did brush and spray the ENTIRE inside of the door - front, back, sides, upper, lower, EVERYTHING. 2 coats recommended, I did 3. Follow your instructions.
Reminds me a lot of POR. and comes off the skin just as "easily", and by easily I mean it doesn't come off. Treat it just like you do POR15. Knock the surface scale off, scuff up any bare steel and lay on your first coat after it's cleaned up / degreased.
Now that you've got the converter goop on and it's at the least flashed, preferably swaying more towards full cure you can continue on with the fun.
I built some braces for the inner door, to replace the ones that come stock and were badly rotted out. I actually just grabbed some scrap steel I had laying around and knocked them out. Truthfully they are somewhat rough, however it's the inside of the door and nobody will ever see the dang thing anyway. I matched the gauge of steel to the stock piece and formed it with a beater bag & mallets. Easy peasy - they are rough, however it's the inside of the door, so they are "good enough".
From there I welded the brace in. It'll actually get physically attached to the door lower once the lower gets welded in, via 4 spot welds - again, mimicking factory. Once that was done I ground the welds (yeah.. I still dress welds even though they are inside a door, so sue me) and treated it with more of that rust converter crap.
While welding in the braces for the inner doors before going out for the night I coated the inside of the inner door patch panel with the converter junk as well. You DO have to rough up bare steel before applying the stuff - I went with 80 grit on a locked DA - doesn't have to be pretty, it's the inside of the door. Just make sure you rough up the WHOLE piece as you don't want the stuff flaking off the road. Get all your nooks & crannies, corners, anything and everything. On this I only gave it two coats, as I knew I'd be throwing another layer on it over the weld zone. Also before you weld in your piece GRIND the coating off anywhere you will be welding. I personally use weld through primer in those areas, and then top it off with another layer of converter once done. If it's an external weld I always epoxy prime them, but for this, It got dressed and then a layer of this goop inside, and the outside will be epoxied once the rest of the door is blasted.
Come the next morning I rough cut the lower patch panel down, to be able to test fit it. Remember those measurements? Pull 'em out - this is the time to USE them. Measure MEASURE measure! Can't stress that enough.
Slamming the new piece on for the test fit / intial fitup.
note my extra special extra rough 2 second quick cut. Nice cut lines, huh? heh.
Anyway, the way I do a lot of patch panels like these is fit up the panel where it should be. clamp it down and then cut through BOTH the old AND new panel at once. Doing it that way leaves a nice tight joint for a butt weld. Personally, I hate lap joints - butt welding is the way to fly, in my opinion, for crap like this.
More fitup, more measuring. Tedious, however it IS necessary.
Got both panels cut, clamped the thing down and used a few of the butt weld clamps - those things really do come in handy. ANY bodyguy should have at least a handful in their toolbox. I swear by the things for hanging quarters, lower door skins, whatever.
From there I started the process of welding the thing in - however NOT before checking the measurements ONE more time. From there make a series of small tack welds, skipping around and allowing them to cool between each spot weld as you don't want to warp the snot out of your existing steel NOR the brand spanking shiny new skin. Once you (finally) have the thing welded in bust out ye ol grinder and slowly and carefully dress your welds.
Process started, still more to go.
After more careful grinding.
Now you can move on to starting to reskin the thing!
The one thing I did forget to mention is don't be surprised if you have to beat the patch panels into submission. 95% of the patch panels on the market are not exactly known for great fitment out of the box - that said I routinely have had great luck with Goodmark stuff, for what it's worth. Anyhow... throw that in with the factory tolerances from 40+ years ago, and it's a recipe for some cussing, head scratching and thinking, but it's nothing that can't be easily overcome. That's what BFH's are for... KIDDING! Use your body hammers and dolleys... not a BFH. It's all about controlled blows, massaging the piece into place... NOT giant blows with a mallet SHOVING the thing way past where it needs to be / should have been
Once your door is flipped over mark your initial cut line. This is just a rough cut, namely to gain access into the inner door.
Mine was 7 3/4" up from the bottom edge. No rhyme or reason, just sounded like a good number. Kidding.. actually I planned on my final cut line being 8" up from the bottom so 7 3/4" gave me a bit of a cushion for the rough cut and wiggle room. Again - your skin may have be lightly ground at the edges to separate it up higher than you did to remove the lower, all depends on where you section your lower and skin to. If so be SUPER careful to not screw up the good solid inner doing such.
Now that you've got her peeled like a .. whatever. Clamp your inner door bracket to the skin (you may have to use a body hammer to coax the bracket into alignment with the inner skin for plug welding. I got lucky (er.. I mean I'm just THAT damn good ) and didn't have to touch mine. Now drill a 3/16" hole through the outer skin being careful to NOT drill through the brace. If it's 3 or more panels stacked, drill through EVERY piece, save for the bottom piece making the holes progressively smaller from the top down. If you didn't already, now is the time to clean up the area that will be welded on the brace, removing the coating and exposing bare steel. I drilled all my holes, and everything was already knocked bare where the plugs would be ( I spaced and forgot to snap pictures, apologies) and then set to welding 'em up.
Plug welds, if you weren't aware, are how you can replicate the factory resistance spot welds done at the factory. You CAN buy a resistance spot welder, but these are just getting plug welded instead.
Anyway. Start welding around the edge of the hole and then whipping the torch towards the center with the torch. I kinda "punch" in a bit with the torch head if I know I won't be dressing the weld as it dimples it and replicates the factory crap better, however here they were dressed, so I said screw it and just burned 'em in and then dressed 'em.
After a quick dressing (still needed a touch more in the photo) you won't really be able tell I was in there once the door gets sand blasted. I actually DID dimple in the area the spot welds go, to replicate the factory stuff, as they were actually slightly dimpled off the floor, so I did the same.
Anyway, from there coat the weld areas.
Now do the same thing again, laying your patch panel over, measuring and aligning it where it should be. Mark your final cut line and carefully cut through both panels once the thing is clamped in place where it should be.
From there I grab a bunch of butt weld clamps and clamp the skin into position leaving myself a tick under an 1/8" gap between panels.
That's just starting the fit up process.
Then measure AGAIN and then measure ONCE more. Then CAREFULLY start to knock over the sides of the flange, to help further hold the panel into position being careful NOT to shift the thing around in the process. Then measure again! Just to be sure.
Now start your tack welding process over again skipping around the panel to not warp it. I'll be flat out and tell you these patch panel lower skins fit for crap - however they were made to work and with a skim coat of filler, they'll be good to go. Problem was their stamping was so far out from the stock curvature of the door, it wasn't even funny.
Once you have the thing welded fully, you can start dressing your welds and you'll be left with something like this.
From there, you get to reach your arm up into the lower section of the door through where the window regulator usually sits and attempt to dress and coat the weld areas. I managed... somehow. Total pain, but they're coated. Hopefully these will hold up for years on end with no issues. Also remember to replicate your drain holes.
From there the doors will get sand blasted, and I'll finish out the metal work where needed, then start the actual bodywork. Granted, it's a lot of work, but frankly when you run into stuff like this truck where parts are like hens teeth, it's well worth it. The ironic part is these doors were sold as "solid rust free" doors from California. You can bet the truck owner was T/O'd when they showed up... Anyway. There ya have it. Hope that's a decent first post. 
edit: can't figure out image tags on the board. lol. good thing I never claimed to be good with computers...
