The Stovebolt Site Forums The Shop Area Paint and Body Shop What should I fill the fender seam with?

I have an aftermarket front fender and the metal on the very front is over lapped then spot welded. It leaves quite a gap. I was wondering if I should fill this with filler or seam sealer or go through the trouble of welding it up? Here is a picture:
Driver side reproduction fender seam

The stock passenger side is much nicer:
Passenger side stock fender with no filler.

I know you can paint over some seam sealers,but assuming you're wanting the best finish possible,welding them up would be the best option.
You'll need to watch out for warping though.

Alternatively,try and find someone who can do lead work.
Lead allows for vibration and flexing,better than most bondo fillers.
Or...if you're feeling brave,have a go yourself!

It would depend on what you want in the end. It looks like the factory was content to leave this seam visible or they leaded over it.
If you want to hide the seam forever weld it or lead it. If you just put plastic, bondo, over it someday down the road it will show up....slightly, but you'll see it.
I know, I can hear it already, there are guys who are going to claim there is no shrinkage with plastic, that it just is not possible.
I did what you are attempting to do with a seem on a truck a few years back. I was doing a little custom work on this truck and wanted a cleaner look so I just filled over the seam with bondo and it looked great.
It took about three years and that seem I covered showed up.
I hate to use the word shrinkage, cause I guess that's not possible, but there it was, so call it whatever you would like.
I'm not saying it's big time visible, but in the right light at the right angle you see it.

Dan

I don't mind seeing the seam, but it is pretty bad. I think I will weld it since I don't want to learn how to use lead or spend the money on it. I had used seam sealer in the rain gutters and was able to paint over it with epoxy so I was thinking that was an option. Guess I should do it right the first time!

Dan,
What did you actually see with the filler? Was it lighter or did it crack around the edges? Asking this because there is filler on my truck, mainly skim coats, but in two places it is 1/8-3/16" thick. Just wondering what to expect.

might look worse in person, but not much different than factory from the pic, remember the areas that will be hidden by the park light and headlight bezel .... which should be fitted before any welding!!

unless you're going for a real show truck, I'd think the seam sealer [holds up fine under paint] and maybe a bit of hammer work would have it looking pretty close to factory - and save having to weld up the other side to match ..... plastic filler will be visible as a difference under paint unless sealed with a couple coats of epoxy primer - and unless you're an excellent welder you'll be using filler on the welds

Bill

Yeah, it looks worse in person. I'm not going for a show truck but I am a perfectionist. It would be so much faster to use the seam sealer...Ugh, decisions, decisions. And I would have to go fill my welding tank, while the seam sealer is on the shelf just begging to be used!

Thanks for the info on the filler, I will definitely have a couple coats of epoxy over the filler along with 2k.

The seam in the reproduction fenders run vertical from the head light to the bottom edge,correct ? I agree they are ugly and i looked at a set at the vendors.I think welding them up would be best in the long run.

Do the original ad fenders have these same seams ?

No AD fenders do not. That is a TF fender thing.

yes Tim, the originals have the same joint, just [usually] a bit better done

Bill

Bill is right, it is there and I don't mind it all that much, it is just more of a lap joint on the reproduction parts. There is also a lap seam from the inside of the headlight horizontally to the inside. The original does not have this seam. I welded this one up but for some dumb reason didn't do the vertical seam, guess I figured it would look ok after some epoxy...wrong.

jomichael,
The seam I filled over was very much like the one you are dealing with. It was a rear corner piece welded to the box. The seam ran vertical, top to bottom. I filled it making the whole side of the box smooth, no seam.
No discoloration to the paint , no cracks, but after 3 years you could see and feel a slight indent the whole length of the seam.
I call that shrinkage, but their are guys that say that can't happen.
For the most part, bondo isn't used this way, which is why I think it never posses a problem.
I think if you were to use filler on the seam you have it would be hard to see it because it's a smaller area and not a big flat area like the side of that box.
I didn't think that would happen over that small seam I filled over, so I threw that caution to you so you would know what could possibly develop in time.

I don't know your time line for completing the truck, but if you are a year away from painting, maybe 6 months would do. Fill that seam right now, rough finish it, let it set and redo it when paint time comes up and that would be a better way of dealing with it.

Dan

Dan,
Yeah, it is about 6 months away so anything I do now will have time to cure completely. You mean just add another skim coat before final paint to make sure it is perfect, right?

jomichael,
The important thing right now is to just fill the major crack so that it is flush. It don't have to be pretty, just buzz it flat leaving the crack filled.
The idea is to just fill the crack and let it shrink if it wants to. Then come prep time for paint the only thing left to do is skim coat the area and sand it out for the finally smooth finish.
Like the problem with mudding a hole in drywall. You put mud in the hole, next day you come back for another coat to fill over the shrinkage, only difference is the bondo doesn't want to shrink in one day.

Dan

Weld it, grind it, skim it, prime it. It's not that much more work than filling, sanding, filling, sanding and then waiting for it to crack because of all of the flex and vibration at that end of the truck.

Very valid point about the cracking Desert_buick has.

Just a thought have you thought about using fiberglass resin with out the fiber glass it self i have seen it fill simmilar stuff. but i think you haft to have it set flat giving the resin a chance to puddle in seam and then sand off the excess by hand

It's not a good idea to use resin by itself. The resin becomes to brittle by itself and will crack.
That's why in Corvette bodies most of the cracks appear. Take for instance the corners of the hood opening. When the panel is molded the resin builds up a little heavier in the corners and it's one of the first places you'll see small cracks develop.

Dan

Thanks for all the responses to this question. I decided to weld it up and hit it with a skim coat of filler. Just add that to the list of things that need to be done!
Thanks

Thank you for letting me know about the resin