[graywolf_14]

What is the reason people lap weld instead of butt weld when putting in floor pans? Is because of strength, skill or just easier? I even seen an article in mustang monthly where the lap welded the floor pans in. I mean to me butt welding you could clean the welds and it would look good.

 

[wareagle]

What is the reason people lap weld instead of butt weld when putting in floor pans? Is because of strength, skill or just easier? I even seen an article in mustang monthly where the lap welded the floor pans in. I mean to me butt welding you could clean the welds and it would look good.

We spot welded mine, so I cannot contribute to your query.

 

[graywolf_14]

Did yoh do the one piece or half pans? As far as i know most people spot weld 1 piece floors.

 

[wareagle]

Did yoh do the one piece or half pans? As far as i know most people spot weld 1 piece floors.

1 piece...

 

[MrRon1]

Spot weld and used the pieces and now wished i used the one piece

 

[xcelr8]

I lap and plug welded mine. Punched holes down the rocker side of the pan and the tunnel side then set it in there. Sheet metal screwed it all together and plug welded up the holes. Then I stitch welded the seam between the plug welds together *still have to finish that. ran out of weld gas*. I'll eventually weld the underside of the pan to the tunnel also. Have pix in my link below.

It was much easier to have the single pan set in and level that way compared to lining up the pieces for a butt weld. Also, if I burned through the tunnel I had a lot more material to work with/weld to around that area. To me, and this may just be a matter of opinion, a plug weld that then has a the seam welded is a bit stronger vs just butt welding two next to each other. Honestly do not care what it looks like under carpet and a seam on the underside does not bother me. I'm building a driver, not a show car.

 

[roboticservo]

To answer your question, most people will lap weld floor pans because it will be under the carpet (inside) and unseen or covered by undercoating on the outside. It's far less effort to lap weld than butt weld. You will see butt welding when you want to make a patch invisible.
As a side note, a lap weld will leave the metal the same thickness (except where it is stacked) while if you are not careful on a butt weld you might grind/sand too much of the weld area and make the metal thinner in that area.
A lap weld is easier to make stronger while a butt weld is easier to make weaker.

 

[Fstbk]

A butt weld will not trap moisture between the layers and rust like an overlap will.
An overlapping weld is usually faster and requires less skill.

You can overlap and tack weld both sides, then run a body saw or cut off wheel or even a plasma cutter right down the middle of the overlap and have the gap you need to make a butt weld, they even make special clamps to hold it in place.
I would rather have a butt weld with none of the welds ground down than an overlapping weld with goo sprayed over it by the guy that wants to hide it.


If the car matters use a but weld and leave the overlapping spot welded seams where the factory put them in the first place.

 

[shelbyshelby]

A butt weld will not trap moisture between the layers and rust like an overlap will.
An overlapping weld is usually faster and requires less skill.

You can overlap and tack weld both sides, then run a body saw or cut off wheel or even a plasma cutter right down the middle of the overlap and have the gap you need to make a butt weld, they even make special clamps to hold it in place.
I would rather have a butt weld with none of the welds ground down than an overlapping weld with goo sprayed over it by the guy that wants to hide it.


If the car matters use a but weld and leave the overlapping spot welded seams where the factory put them in the first place.

That's how it is, IMO

 

[Bucket Lister]

If you mean replacing a few toe panels or rear seat footwells, yes, a well performed lap weld is stronger than a butt weld. It is also much faster because you don't have to trim and fit and grind them perfectly. You do twice the welding because you should weld the lap inside and outside.

 

[anotherhassel]

I am a union sheet metal worker so I have alot of experience welding thin gauge metal. The simple answer is that over lapping the metal helps take the heat away. It doesnt matter how good a welder you are sheet metal will twist when heated. Butt welds in sheet metal can be done however they take a very long time to make the almost unnoticable. However you can use a pexto roll forming machine that will jog the patch panel to take your heat but only will overlap minimally. Now that being said if I were doing a floor in a mustang ,it has been quite a few years, I would and have done it like someone else said and punch holes and replug weld. Then seam seal and be on your way. If doing a patch on the body I would jog the patch then stitch weld the fill sand prime paint. Let the criticism start now.

 

[xcelr8]

.... I would and have done it like someone else said and punch holes and replug weld. Then seam seal and be on your way.....

Makes me feel better about mine! If that's good enough for a guy who does it for a living... it's good enough for me.

 

[Fstbk]

Well, I can see the next generation of classic mustang owners bitching about how the "Previous owner" jacked up the car with overlapping welds and covered them with "Goo"!

Do you really think they have discussions like this over on a GT40 forum or on some of the high end British cars? Why do we insist on saying it's "OK" to do a hack job on a mustang?

 

[graywolf_14]

I decided a long time ago to do the one piece floor just was wondering this.

 

[GypsyR]

I don't think this really applies to the one piece pan, just the patches.
Simple enough to me. Lappping is a heck of a lot easier but a bit cheesy. If you butt weld you can make the repairs about invisible and much less prone to long term rusting. That said, pan patches are a pain. I have to admit I used the patches and did my best to butt everything but there are some laps. I hate to see crappy welding on anything and work with it in mind that I wouldn't want someone else looking at such stuff later on and thinking "what jackass did this?" If I had to do it over I'd use the one piece pan and spot it in like the factory did.

 

[anotherhassel]

Well, I can see the next generation of classic mustang owners bitching about how the "Previous owner" jacked up the car with overlapping welds and covered them with "Goo"!

Do you really think they have discussions like this over on a GT40 forum or on some of the high end British cars? Why do we insist on saying it's "OK" to do a hack job on a mustang?

Ok so the goo you are referring to is on you car now from Ford. These cars are not gt40 s or high British cars the are high production cheap cars. Look at how Ford built them I.e. cowl vents. If done properly with a lap of less than an inch then seam seal then undercoat car is as good or better than New. If you want it to be jewellery then by all mean sit there for days welding 1" welds at a time to keep from twisting. If you want a sound strong clean factory looking install try it my way.

 

[Bucket Lister]

I agree with anotherhassel. Ok, if you have HenryFordII's or Carrol Shelby's personal mustang, sure go ahead and throw a $million at the car. But if its a GT or a T or a modest 2V coupe, you can build a very nice car without getting carried away. The dirty little secret about this hobby is that you'll never get your money back out of even a "street" level restoration. I admire the VMFers that have showroom perfect cars that collect trophies. God bless'em. I'd probably never take it out of the garage.

 

[JohnnyK]

Well, I can see the next generation of classic mustang owners bitching about how the "Previous owner" jacked up the car with overlapping welds and covered them with "Goo"!

Do you really think they have discussions like this over on a GT40 forum or on some of the high end British cars? Why do we insist on saying it's "OK" to do a hack job on a mustang?

Same reason you insist on not top coating your epoxy. It's easier, and not necessarily needed.

 

[buflash]

Wow, there have been dozens of lap vs. butt conversations on this forum, but I have to say this is one of the most provocative. I had my mind set on butt welds because I thought the same thing as many others regarding it being less prone to future rust and less detectable as a repair. However, some very good points have been made for lap welding and I am now seriously considering it for my C code coupe. The kicker for me is that the car will rarely see a wet road and the seam sealer / undercoating should do an exceptional job of keeping moisture out anyway. I can't see how a buyer would scrutinize it in the future. I think in my region, any buyer would jump at the chance to buy a solid car without care for the technique used to get it there. Solid is solid and represents a giant leap forward in terms of the car's condition any way you look at it. I would buy a car with lap welds tomorrow and not curse out the previous owner. In fact, my convertible has lap welds in the floor pans which I had paid to have done at a shop years ago and I'm not disappointed with them at all. In fact, the way they're done you can hardly see them.

 

[Crash]

I don't consider using lapped seams for patches "hack job". If the welds are good, the joints are tight, and they are properly sealed, their function will be good as new. However, if appearance matters, then you must butt weld.

The debate seems more about what one "should" prefer, and you can never settle that one. One guy wants functional and "decent" while another guy wants imperceivably repaired. Neither is wrong just as blue is no more wrong than white.

I chose to use butt welds on my floor patches (eight, in all) so that from below, they were invisible. It's what I wanted. It may not be what you want, but that doesn't make either of us "wrong".

Now, if right and wrong are defined by "how Henry did it", then you have a different discussion. However, Henry did not install repair panels, so...