Repair to bottom of cowl on touring car

[22touring]

I certainly would appreciate receiving any advice or suggestions that my fellow Dodge brothers might have about the correct way to repair rust-outs at the bottom of the cowl, where it meets the bottom of the body.  Thank you kindly.

[JFranklin]

Usually it is cut and weld in a new patch. Many cars rusted in that area. Since there is no decorative bead there it should be fairly easy to make a patch.

Edited July 3, 2021 by JFranklin (see edit history)

[Mattml430]

Cut in a dead straight line about 1/2” above the rust from one side to the other leaving about 1/4” from the corners of the cowl. It makes it easier to blend the new panel in at the edges because there will be less distortion on a corner. Tack the new panel in starting in the middle and work your way to the outside tacking about an 1” apart at a time. I use magnets to hold the steel flush and in position while tacking it together. 
shape the new panel to the cowl before you cut it. It won’t need to much but get it right first. Use .9mm-1.0mm on the cowl. You may need to put a return fold on the bottom by the looks of it. 

Edited July 3, 2021 by Mattml430 (see edit history)

[22touring]

Thanks, boys!  That was very helpful.

[22touring]

"LOL", as they say these days!  I had forgotten (or more likely repressed) how I had stuffed fiberglass into the hole when I did a half-vast restoration in the mid-'80s.  So now we are going to find out how well paint stripper will remove fiberglass.

 

 

[Mattml430]

20 hours ago, 22touring said:

"LOL", as they say these days!  I had forgotten (or more likely repressed) how I had stuffed fiberglass into the hole when I did a half-vast restoration in the mid-'80s.  So now we are going to find out how well paint stripper will remove fiberglass.

 

 

I don’t think paint stripper will do much to that you’ll have to cut it out. Unless you still have some of the good old school paint stripper that ate everything. We can’t get the good stuff anymore it make the ice melt in Antartica. 

[RichBad]

3 hours ago, Mattml430 said:

I don’t think paint stripper will do much to that you’ll have to cut it out. Unless you still have some of the good old school paint stripper that ate everything. We can’t get the good stuff anymore it make the ice melt in Antartica. 

I remember that stuff.  I put some in a container, went to put some gloves in and by the time I came back it had eaten through the bottom of the container!  Stung worse than a bee if you got a splash on your skin.

[22touring]

Nobody in my home town had any 18-gauge or 20-gauge cold rolled, so I had to travel to the industrial outskirts of Sacramento in order to buy some from Metal Mart.  I think that is probably because the local body shops fix rust holes by stuffing them full of steel wool and applying fiberglass over them, so they don't need to be buyin' no stinkin' sheet metal.

 

The 18-gauge seems noticeably thicker than the steel that was used in my DB, and the 20-gauge is close but maybe a little bit thinner.  I think I am going to use the 20-gauge to repair the cowl.  I'll bet 19-gauge would be perfect, as Mattml430 said, but Metal Mart didn't have any of that.

 

My MIG welder came set up for "no gas" use, with flux-cored .030-diameter wire, and I had to convert it over to the solid .022 wire and to use carbon dioxide as the shielding gas.  You would think converting it over would be easy, but there were a surprising number of niggling little details which required multiple trips to the hardware store for brass compression fittings, buying new contact tips, etc.  Also, buying an inert gas cylinder, regulator, flow meter and a new roll of wire was pretty expensive.  All in all, it was more difficult and expensive to convert it to gas use than I thought it was going to be, but I think it had to be done.  Trying to MIG weld sheet metal with flux-core wire just creates too much heat, don't you think?  I can see why they sell you the welder set up for "no gas" use, though.  The price of admission is much lower that way.

[Mattml430]

Sounds your heading in the right direction to knock it over. I’ve actually never used flux core wire before so I don’t know what it’s like. 
Im positive the rewards of completing it yourself will far outweigh the expense. Good luck with it 👍

[JayG]

I used 20 gauge to repair my 25 roadster and it was much easier to work with than the 18 gauge. It butt welded to the existing nicely using a gas MIG setup.

[22touring]

For my first practice welds on the 20-gauge, which turned out badly, I held the two pieces of metal together with butt weld clamps at a .40" gap.  Is that too far apart?  I'm wondering if that is part of the problem.  Correction: The data sheet for the clamps says .4 inches, but that's impossible, so they must mean .040", or a 25th of an inch!  I'll measure the gap and report back. 

Edited July 22, 2021 by 22touring
correction (see edit history)

[JayG]

.40" sounds pretty wide.  I basically had the width of a thin Dremel cutoff wheel which is probably 1/16".  The voltage and feed need to be set properly.  I practiced with some sheet metal strips until I was happy with the welds.

 

Looking at your clamps did you mean .04"  they look pretty thin.

Edited July 22, 2021 by JayG (see edit history)

[22touring]

.04", or 40 thouandths, gap, so that is not the problem. Must be wrong wire feed rate, wrong current or wrong amount of gas.

 

What would cause my welds to be all burnt out in the center and black around the edges?

 

 

[JayG]

I'm not a welder so I'm not the right person to tell you what you're doing wrong.  I have had good luck with my MIG using these settings.  And my gas is regulated to 30 CFH.  It works for me.  Good luck Jay

 

[Mattml430]

6 hours ago, 22touring said:

For my first practice welds on the 20-gauge, which turned out badly, I held the two pieces of metal together with butt weld clamps at a .40" gap.  Is that too far apart?  I'm wondering if that is part of the problem.  Correction: The data sheet for the clamps says .4 inches, but that's impossible, so they must mean .040", or a 25th of an inch!  I'll measure the gap and report back. 

Those clamps work quite well but I prefer to use rare earth magnets, that way you can set your gaps to what you like. Every welder will need to be set differently. Set you gas between 15-20 and then on some scrap do a few quick spot welds until you get a even little lump about 2mm high. When you weld you panel in, start in the middle and work you way out spotting it about 3/4” apart. That way it allows  the metal to move to where it wants without being locked in at each end. If when you spot weld and it blows a hole in the sheet turn your wire up a little and maybe amps down a little at a time. You should get a nice even sound when you spot. Once you’ve tacked it all the way along do it again all the way across in between each tack. I start in the middle and then work each side of the centre just tacking in between each weld. It lets it cool enough to help stop distortion. If you have a thick bit of metal like a dolly you can put that over your weld to help pull the heat out of each weld. Go slowly to let it cool. Make sure both side of your metal is clean and free of old paint. It must be cleaned back to shiny metal. You may have a bit of old paint on the inside of the cowl that will cause you grief. Keep practising until your happy with your welder settings. 
I normally tack all my jobs with a mig and then finish weld with a pulse tig but that’s a whole other story. The mig welder will work just fine. 
I’ll do a little scrap panel this morning and post a picture for you. 

[Mattml430]

6 hours ago, 22touring said:

.04", or 40 thouandths, gap, so that is not the problem. Must be wrong wire feed rate, wrong current or wrong amount of gas.

 

What would cause my welds to be all burnt out in the center and black around the edges?

 

 

If you have a bubble in the centre it can be lack of gas or a dirty surface and the burn is normally some impurities burning. Clean clean clean. 😂

[JayG]

I agree with the clean clean clean.  I meant to mention that.  It's extremely important.  Bare metal cleaned with wax/grease remover.

[nearchoclatetown]

Another thing that will help with thin metal is to put clamp a piece of copper, maybe 1/4 inch thick, to back of weld. It will suck out the extra heat as Matt talked of. It will also keep your gas from escaping through the crack. 

[Mattml430]

Here’s a few pics, I hope it helps. 
Get the welder spotting on a piece of scrap like this first. 

line up your material with your clamps or magnets. 

Tack every 3/4 or so. From middle out. 

Tack in between each weld again and again until they all join. Doing it this way prevents to much heat getting into the metal. 
Clean up with sanding disc and finish off with a soft pad sander. 

[22touring]

Thanks very much for all the great help, suggestions and pictures!

[Ron Lawson]

14 hours ago, Mattml430 said:

Here’s a few pics, I hope it helps. 
Get the welder spotting on a piece of scrap like this first. 

line up your material with your clamps or magnets. 

Tack every 3/4 or so. From middle out. 

Tack in between each weld again and again until they all join. Doing it this way prevents to much heat getting into the metal. 
Clean up with sanding disc and finish off with a soft pad sander. 

Matt you make it look so easy 

[22touring]

I kept practicing at MIG welding 20-gauge sheet metal using .023" solid wire with gas, but got poor results until I happened to notice that in all of the videos that I watched about sheet metal MIG welding, they put the beveled end of the torch's gas nozzle right on the work, at about a 45-degree angle, for the minimum possible wire stick-out.  I had been holding the torch too far away from the work.  As soon as I began putting the beveled end of the nozzle right on the work, while using a moderate amount of voltage (I read the instruction book that came with welder) and a high-ish wire feed speed (7 on a scale of 10, because you want good penetration), I began to get passable results and my head swelled up greatly.

[nearchoclatetown]

A clown I used to work with always said with enough grinding wheels you can make any weld look good. Don't be afraid to put on more weld, it will come off too.

[Mattml430]

Well done it’s looking good. Practice makes perfect.