Swiss-cheese fenders
 

I am starting the ornery job of repairing the fenders on a 36 tudor. I'm trying to do as much of the work on my car as I can but this body work is new to me. I'm MIG welding patches on fenders. After welding, I am able to come up with a fairly smooth patch. Incidentally, there is lead and brazing metal on the fenders. No plastic.
My question is: How do I finish off the underside? The underside can be seen if you get down and look. For a daily driver, must they be clean and smooth like the visible side? Is there an undercoat that covers most of the blemishes? If so, what is it, where do you get it? Would spray-on bedliner work? Is there a sealer for the welds so that any pin holes are sealed? Again, what is it, where do you get it?
You get the picture. I don't know much about what I'm doing!
Royal

Re: Swiss-cheese fenders
 

Why not just finish it off with body filler? It is on the underneath, so it doesn't have to be that fussy.

Re: Swiss-cheese fenders
 

bedliner works xlnt for covering and it will also cover any small holes in the welds, if your good with fiber glass use it under the fenders, sand smooth and paint

Re: Swiss-cheese fenders
 

Swiss cheese, more like the screen door too.

Here's a couple of fender patches I did. In some cases I found donor fenders that where "bad" in places mine where "good" and some that had the good/bad reversed.

Back up your welds with a piece of copper and your less likely to burn thru the swiss cheese. On most of my patches I put a 1" wide backer from under the old metal and the new.

If you leave pin holes they are going to rust thru eventually. Cut and paste patch panels wherever you can. Really rusty old metal requires that you treat the metal before painting. Some guys just use etching primer but I like Ospho as a rust converter and then an epoxy primer.

I fiberglassed the inside of all my fenders.

Re: Swiss-cheese fenders
 

When you guys make patches, what gauge metal do you use?

Re: Swiss-cheese fenders
 

18-20 gauge depending on what your repairing.

Re: Swiss-cheese fenders
 

I had a 40 rear that was full of pin holes and I needed to use it until I could find a good one … just in primer.
After blasting I taped the outside of the holes and JB welded the inside
Then reg filler on the outside and put on a few coats of DP epoxy primer…. I didn’t expect it to still have no holes or clacks 15 years later but it does

Re: Swiss-cheese fenders
 

You can get a brush-on bedliner or undercoating from most of the bigger auto parts stores or your local automotive paint supply house.

Small pinholes are usually a sign that the surrounding metal is thin. If it were mine, I'd replace it with new metal wherever possible.

Re: Swiss-cheese fenders
 

I am interested in Bob Drakes new fenders, but for the tudor they won't be available for some time. They can't say how long and wouldn't put me on a wait list. I've heard the ones now available are very good.

Re: Swiss-cheese fenders
 

If you are new to this sort of patching, you might not be aware that the wire in your MIG makes a big difference. Most wire supplied with a new welder is a hard wire that works fine for welding angle iron and thicker metal but for thin body tin you should use a soft wire that allows you to work the patch with a hammer and dolly when finished. A wire used by many body shops is marketed as "easy grind" wire. The hard wire can leave a lumpy patch that is very difficult to work down because the weld is harder then the metal patch material. Pre MIG days this was all done with a torch and the hard welds were not a problem. This is why many still use the torch. I prefer doing TIG welds which has less heat related issues but it takes a while to be proficient with this method.
Bed liner might just be the ticket for the underside of your project.

Re: Swiss-cheese fenders
 

3M makes a product called body shutz which is a rubberized undercoating that is paintable. Pete