Welding advice, Can a cheap flux welder do what I need? Options

[MikeK]

Here's an alternative method for fitting and holding panels. I cut a bunch of these little tabs, punch an 1/8" hole for a cleco, tack to either side of the panels your joining.
(IMG:http://www.914world.com/bbs2/uploads_offsite/www.thesamba.com-27418-1702570226.1.jpg)

Regarding butt vs. lap welding; My suggestion to lap was based solely on the OP's lack of experience. The most skilled part of this job is the welding, the rest of the job is patience and the grunt work of putting the panel in and out to obtain a good fit. With enough fitting, the panel could be made to fit like a glove, then rosette welded with proper surface preparation. Is it the best way? Let's just say it isn't how I would do it, but fitting a panel with little to no gaps is a skill that needs to be developed as well.

Considering that EVERY joined panel on your Porsche is a lap weld, I think it's a viable option. In fact, the only butt welded panels I can think of on a Porsche would be 356 outer panels, and you would never want to weld those with a MIG because you wouldn't be able to metal finish it.(IMG:http://www.914world.com/bbs2/uploads_offsite/www.thesamba.com-27418-1702570517.1.jpg)

Good luck!

[930cabman]

Great advice MikeK, thanks

I will making the same (frunk floor) replacement and will shoot for the butt, it just looks cleaner.

Who will look under the spare tire anyways?

BTW: looks like you have a nice little project with the 356

[914rrr]

Is flux welding more apt to have paint adhesion issues vs MIG? IIRC, one of my first 914's had a what looked like a rust spot in the drivers side front fender near the bottom. When we started grinding it, we discovered it had been repaired / patched already and welded (brazed) with brass. I was told that unless you are meticulous in removing every bit of flux then then the body filler and paint wouldn't stick to it properly. Is this correct?

[930cabman]

Is flux welding more apt to have paint adhesion issues vs MIG? IIRC, one of my first 914's had a what looked like a rust spot in the drivers side front fender near the bottom. When we started grinding it, we discovered it had been repaired / patched already and welded (brazed) with brass. I was told that unless you are meticulous in removing every bit of flux then then the body filler and paint wouldn't stick to it properly. Is this correct?

Not only flux, but any contaminant. painting is all about prep and it can be anything

[914rrr]

Is flux welding more apt to have paint adhesion issues vs MIG? IIRC, one of my first 914's had a what looked like a rust spot in the drivers side front fender near the bottom. When we started grinding it, we discovered it had been repaired / patched already and welded (brazed) with brass. I was told that unless you are meticulous in removing every bit of flux then then the body filler and paint wouldn't stick to it properly. Is this correct?

Not only flux, but any contaminant. painting is all about prep and it can be anything

So, is flux core welding generally a bad idea for anything that will be painted, especially if it's on an exterior body panel vs pans or trunk areas?

[mb911]

Is flux welding more apt to have paint adhesion issues vs MIG? IIRC, one of my first 914's had a what looked like a rust spot in the drivers side front fender near the bottom. When we started grinding it, we discovered it had been repaired / patched already and welded (brazed) with brass. I was told that unless you are meticulous in removing every bit of flux then then the body filler and paint wouldn't stick to it properly. Is this correct?

Not only flux, but any contaminant. painting is all about prep and it can be anything

So, is flux core welding generally a bad idea for anything that will be painted, especially if it's on an exterior body panel vs pans or trunk areas?

No it will be just fine. They literally paint buildings and the frame work of sky scrapers that have been flux core welded. Just clean it properly

[mb911]

@mb911 That TIG weld is a thing of beauty. I only have access to a MIG welder and am not skilled enough to lay down beads like that.

Re-reading my follow-up post, the litany of not wanting to weld from the bottom was about the lap weld. I thought I would have to do the top and the bottom.

I have a pretty good mess to clean up first, so I'll see how I do with all that work first. And then I'll decide how comfortable I am with the butt weld. I usually have to do things twice. Something tells me I'll be paying a professional–eventually.

Thank you everyone for your thoughts. It is a constructive discussion. I've learned a lot. (IMG:style_emoticons/default/smilie_pokal.gif)

Use magnets to hold the but joint tight until it’s tacked in.

I find that my arc likes to wander when I'm tacking things up with a MIG while using magnets. Maybe I'm imagining it.

It also took me a couple of Winters to figure out that my welds went to shit when my shop heater turned on. Then I realized all my shielding gas was blowing away...

A few magnets to hold it in place not near where you are tacking

[gereed75]

It will also destroy the strength of the magnet

Always recommend listening to Ben’s advice. Very knowledgeable. Just bought a used helmet from him (reasonably priced too) Even though used was a significant upgrade over my base line helmet. Vis is so much better. Used it for the first time yesterday and actually made a bunch of welds I did not feel compelled to grind!!

Thanks Ben

PS: go check out Fitzee on YouTube. He uses a method he calls cut and butt. I’m a rank amateur but it has worked for me in several applications repairing floor pans.

[mb911]

It will also destroy the strength of the magnet

Always recommend listening to Ben’s advice. Very knowledgeable. Just bought a used helmet from him (reasonably priced too) Even though used was a significant upgrade over my base line helmet. Vis is so much better. Used it for the first time yesterday and actually made a bunch of welds I did not feel compelled to grind!!

Thanks Ben

PS: go check out Fitzee on YouTube. He uses a method he calls cut and butt. I’m a rank amateur but it has worked for me in several applications repairing floor pans.

That does work for sure

[Deusexmachina77]

I cut the panel to where I thought it would lay best and found the best metal to adhere to. I tacked the panel in place, then cut around the panel with the thinnest cutting wheel I could find. Sometimes I used a Dremel. Cut and tack. Cut and tack. The backside closest to the vertical is not as bad as it looks. The old floor sagged away after it was cut. With just a little help it meets the new panel perfectly. I had a couple of mistakes cutting making bigger gaps than I wanted. Rookie mistakes. But all in all I think I'm going to be okay.

[Superhawk996]

(IMG:style_emoticons/default/aktion035.gif) pretty good fit for someone that was going to lap weld it!!

Use a copper backer on those back wall large gaps and you’ll be fine.

Keep going. Go slow. Bounce around. Cool to the touch before adding more welds.

[mb911]

(IMG:style_emoticons/default/aktion035.gif) pretty good fit for someone that was going to lap weld it!!

Use a copper backer on those back wall large gaps and you’ll be fine.

Keep going. Go slow. Bounce around. Cool to the touch before adding more welds.

Copper if you have it and poor man solution is aluminum..

[930cabman]

I cut the panel to where I thought it would lay best and found the best metal to adhere to. I tacked the panel in place, then cut around the panel with the thinnest cutting wheel I could find. Sometimes I used a Dremel. Cut and tack. Cut and tack. The backside closest to the vertical is not as bad as it looks. The old floor sagged away after it was cut. With just a little help it meets the new panel perfectly. I had a couple of mistakes cutting making bigger gaps than I wanted. Rookie mistakes. But all in all I think I'm going to be okay.

+1 looks great. Welding is like anything else, practice and more practice. Sure, the basics need to be correct, but the technique is all experience.

[friethmiller]

I remember the one problem I always had when I started welding was blowing holes through the older metal. You can do two things to avoid this: 1) turn the power down on the welder just a bit; and 2) use shorter burst with the gun. Looks damn good so far! Good Luck! (IMG:style_emoticons/default/welder.gif)

[Deusexmachina77]

I appreciate the encouragement and the tip about the copper!

[r_towle]

never in one area too long....heat warps things.

[gereed75]

There u go - cut and butt at its finest. Nice work.

[Deusexmachina77]

Hello Friends,
@gereed75 , @r_towle , @friethmiller , @930cabman , @mb911 , @Superhawk996

Here is an update on my progress. I'm having a little trouble in certain tight spots with limited tools cleaning up, but I think it's coming along.



I'll do a bit more light grinding, but I hesitate to grind much more as I don't want to thin the metal.

What is my next step? I was thinking of a thin coat of fiberglass bondo. Or should I use seam sealer? Seam sealer would defeat the purpose of all this work, but I realize my shortcomings. It's far from perfect.

As for the bottom side, what should I use for a coating?

Thanks, Victor

[friethmiller]

Well, that depends what you want. If you want to make it look like the trunk was never replaced, buy a finger sander off of amazon and make that weld line disappear! If you're good with what you've got and you've run a light underneath to ensure there are zero pinholes, then you can prep for paint. I'd feather back the paint a bit more and hit it with epoxy primer. You can use seam sealer here if you want. It might look better than the weld, as is, and provide protection.

I'd personally use the finger sander but it's a matter of what you want to look like in the end. Good Luck!

[Superhawk996]

Agree - don’t thin metal by grinding too much

Seam sealer is the next step. The spray on type will mask the remaining weld bead and will look relatively OEM. Brush on will work in a pinch but won’t look quite as nice.

Here’s a temporary repair to mine. I have a full panel to do the replacement but needed a quick temporary fix when I was moving the car cross country.

Seam sealed



Painted



Not sure what you mean by seam sealer would defeat the purpose of the work.

The butt weld is to prevent moisture from collecting between panels like a lap weld. You did a great job with your weld!

The seal sealer is to prevent moisture from getting into weld. Same as OEM. But if it should get cracked, scratched, etc., there won’t be a lap to allow moisture to collect and rust.

If the goal is to make the repair completely invisible - that will be much tougher to achieve. Bondo could be used, but a good eye (or paint gauge) will still pick up that the area has been repaired. Due to all the stamping formation complexity, it will be tough to get filler to match all the formations perfectly and will be very time consuming.