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

[Deusexmachina77]

After much deliberation and searching, I found the best option for my situation—a friend with a welder AND a garage to work on it.

I have another question for this group since you were all so helpful. Should I butt weld or lap weld the new floor pan in? I'm thinking lap weld. I don't want to weld from the bottom. I don't have access to a lift, and I'm not going to be able to weld on my back. I'm too old for that.

[930cabman]

"A friend with a welder and a garage" sounds like a winner, compensate him/her well for this. Is it safe to assume the friend is a welder? they should be versed

Generally lap welds are frowned on, it is an easier joint but the entire car is put together with lap welds and spot welded.

I have the same repair to a project currently on our lift and was mulling the lap/butt question.

I bet others will chime in and suggest a butt weld. Working from the top will be easier, but harder on your back

Don't feel alone, many or most of us are too old for this nonsense too

[Superhawk996]

Butt weld is the gold standard for panel repair.

Lap welds harbor moisture and lead to corrosion no matter how well sealed. Sealant eventually fails and then compounds the trapped moisture and corrosion problem. Lap weld repair better than no repair but it will eventually need to be cut out and repaired properly when it begins to corrode.

A butt weld on that panel can be done from the top.

[Geezer914]

I picked up a used Sears flux core welder for $100. Repaired the hell hole, replaced the battery tray, and patched the bottom of the firewall due to a leak from the back window. Also welded a fuel door in the front hood. It's messy, but a wire wheel and a grinder are your friend.

[MikeK]

There's no shame in a lap weld if the joint is prepared properly. You could do a very clear repair if the replacement panel is joggled at the edges and fits the opening properly. Spend extra time during fitting to ensure it looks correct. Prep the lapped areas with a weld-thru primer, clean your plug weld holes and burn it in. With a 100V machine, you will likely have to crank that welder up as high as it will go to get a clean, flat weld.

With your skill set, this would give you a better looking repair than trying to fit a complex panel to the car with little to no gap and trying to MIG it in. Clean up any weld thru primer overspray, brush or spray on some epoxy primer, seam seal top and bottom and you'll have a repair better than most.

Other than for authenticities sake, to make the weld disappear and have it appear that no work was done, I would do it the way I described. A MIG weld on a butt joint is about the worst tool you can possibly use for sheet metal repairs, other than chassis work. External panels to be finished: TIG or OA with little to no filler rod.

[Geezer914]

Trace a pattern of the cut out on a piece of poster board for a nice tight fit.

[Spoke]

After much deliberation and searching, I found the best option for my situation—a friend with a welder AND a garage to work on it.

I have another question for this group since you were all so helpful. Should I butt weld or lap weld the new floor pan in? I'm thinking lap weld. I don't want to weld from the bottom. I don't have access to a lift, and I'm not going to be able to weld on my back. I'm too old for that.

I've butt welded a bunch of small panels on the floor of my 914 w/o going under the car. All done from the top.

[930cabman]

After much deliberation and searching, I found the best option for my situation—a friend with a welder AND a garage to work on it.

I have another question for this group since you were all so helpful. Should I butt weld or lap weld the new floor pan in? I'm thinking lap weld. I don't want to weld from the bottom. I don't have access to a lift, and I'm not going to be able to weld on my back. I'm too old for that.

I've butt welded a bunch of small panels on the floor of my 914 w/o going under the car. All done from the top.

With a TIG?

[Spoke]

After much deliberation and searching, I found the best option for my situation—a friend with a welder AND a garage to work on it.

I have another question for this group since you were all so helpful. Should I butt weld or lap weld the new floor pan in? I'm thinking lap weld. I don't want to weld from the bottom. I don't have access to a lift, and I'm not going to be able to weld on my back. I'm too old for that.

I've butt welded a bunch of small panels on the floor of my 914 w/o going under the car. All done from the top.

With a TIG?

With a MIG.

[porschetub]

Butt weld is the gold standard for panel repair.

Lap welds harbor moisture and lead to corrosion no matter how well sealed. Sealant eventually fails and then compounds the trapped moisture and corrosion problem. Lap weld repair better than no repair but it will eventually need to be cut out and repaired properly when it begins to corrode.

A butt weld on that panel can be done from the top.

(IMG:style_emoticons/default/agree.gif) ,also the shape of area is a problem already , if repair panel isn't butt welded it's never going to fit properly if lapped the overlay will cause gaps ,its not you can just dolly them down due to all the curves.
Rust is a certainty and just a matter of time and it will look ugly ....ask me how I know all this ?? ,PO did this after welding up a patch to cover the hole for a cooler ,too much heat and not enough tacks ,the patch has also buckled upwards as no gap as there would be with butt weld .
I'am faced with trying to fix this as I can't bring myself to cut it out but may have to ,have scrapped all the sealer out there is rust.


It looks much worse that the photos trust me on that (IMG:style_emoticons/default/headbang.gif) .

[Superhawk996]

@porschetub

Try a shrinking wheel on it to remove the buckling / oil-can effect.

[930cabman]

After much deliberation and searching, I found the best option for my situation—a friend with a welder AND a garage to work on it.

I have another question for this group since you were all so helpful. Should I butt weld or lap weld the new floor pan in? I'm thinking lap weld. I don't want to weld from the bottom. I don't have access to a lift, and I'm not going to be able to weld on my back. I'm too old for that.

I've butt welded a bunch of small panels on the floor of my 914 w/o going under the car. All done from the top.

Being a CSOB I suppose a bunch is cheaper/easier than an entire floor pan. I will probably follow suit.

[mb911]

Ok I have to pipe up a little bit here as I do this for a living.

A: no lap joint is acceptable on a 1/4, floor pan or any where where moisture can get trapped. The floor pan is a lap joint onto the longs and look what happened from the factory

B: flux core is a good solution for many welding applications. NR211 is used as a normal construction filler within the Iron workers on the west coast for structural. That said they are using high end power sources to achieve high quality earthquake code welds.

C: patch panels in a floor are completely acceptable for CSOBs and I have done that before myself but ultimately it takes more time

D: MIG or proper term in the US would be GMAW or MAG in Europe requires the least skill for the average car person. GTAW is way harder to do correctly but requires much less grinding and blending

E: to control warping and oil canning just use small tacks and skip all around. Also use your hand with a glove on to absorb some of the heat from the weld area (HAZ) using a wiping motion. You can also use a damp rag or air nozzle for sheet metal repairs. This should never be done on a structural weld(only let air cool )


Here is a demo weld I did the other day for a reference weld for you TIG welders

[mb911]

[930cabman]

Nothing short of artwork, thanks for posting.

How many years have you been at it? Many I am sure

[bkrantz]

Another vote for butt welding, and you can doing it from the top (inside).

You might get away with a lap weld, but only if you weld on the side most exposed to weather/water. That means from below.

[Deusexmachina77]

@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)

[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.

[bkrantz]

@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.

And make sure metal on both sides of the butt is solid and clean. Thin, dirty, and/or rusty metal edges will instantly burn through.

[MikeK]

@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...