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Lap weld finishing

Discussion in 'The Hokey Ass Message Board' started by VonMoldy, Nov 15, 2008.

  1. VonMoldy
    Joined: May 23, 2005
    Posts: 1,562

    VonMoldy
    Member
    from UTARRGH!

    Guys I am seeing the light at the end of the tunnel on my floor pan replacement. I lap welded the new pans in and am now wondering how I will be able to hide the welds and seams?

    I know they are just floors but I really don't want to be able to see any welds even if I have to crawl under the car and stick my head under the frame. I know they are only like 19g steel so there isn't a huge step where they meet but I guess I am a perfectionist and want them to blend into the rest of the floor and be totally undetected.

    Should I just grind it as smooth as I can and spread some bondo over the ridge and feather it out? or use a thinner strip of metal and weld it along the step to taper it out?
     
  2. briggs&strattonChev
    Joined: Feb 20, 2003
    Posts: 2,236

    briggs&strattonChev
    Member

    Thats what I would do and have done.

    did you weld it on the top and bottom? Im guessing thats what you did since you mentioned grinding.
     
  3. VonMoldy
    Joined: May 23, 2005
    Posts: 1,562

    VonMoldy
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    from UTARRGH!

    I haven't welded the underside of the seams yet but I do plan on it.
     
  4. briggs&strattonChev
    Joined: Feb 20, 2003
    Posts: 2,236

    briggs&strattonChev
    Member

    we are talking about putting filler on the underside, arent we?

    If you mean on the top side, under the carpet, you are the definition of picky :)
     
  5. VonMoldy
    Joined: May 23, 2005
    Posts: 1,562

    VonMoldy
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    from UTARRGH!

    ya I know! is there some sort of Picky Metalworking Anonymous I should know of?
     
  6. here's my opinion...remember you asked for it.

    if you lap weld you end up with something that is not so pretty from the backside . if you think that is important ...then you have to do what you need to to make it acceptable . if you want it nice from both sides them you have to butt weld
     
  7. VonMoldy
    Joined: May 23, 2005
    Posts: 1,562

    VonMoldy
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    from UTARRGH!

    so you are saying I shouldn't even bother?
     
  8. no..i didn't say that

    i said lap welds are ugly..so if you want them to look nice from both sides you have to do some grinding , bondo , filling , priming , etc


    i guess all seams need that
     
  9. VonMoldy
    Joined: May 23, 2005
    Posts: 1,562

    VonMoldy
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    from UTARRGH!

    How do you usually do it? Do you have any pics of the process?
     
  10. If you decide to pretty up the underside I would use duraglass or some kind of metal to metal type filler instead of bondo since it resists moisture rather then sucking it up like a sponge. Then maybe a good epoxy prime and topcoat. Don't want to give rust a chance to start up again to soon :)
     
  11. Eddiesixem
    Joined: Apr 29, 2005
    Posts: 628

    Eddiesixem
    Member

    i agree buttweld when ever posible, but there are certain situations where the lap will apply,
    heres one i did recently,
    here was the problem.
    [​IMG]

    here was the solution
    [​IMG]

    and here was the finished product, yes a little mud was required, i use the Metal2metal stuff by evercoat.

    [​IMG]

    if you want it perfect, id suggest grind as well as possible, then run some of that stuff over it, and feather it out.

    last pic is in primer.
    [​IMG]
     
  12. Eddiesixem
    Joined: Apr 29, 2005
    Posts: 628

    Eddiesixem
    Member

    yea dont forget the epoxy prime, thats the ticket to sealing it.
     
  13. VonMoldy
    Joined: May 23, 2005
    Posts: 1,562

    VonMoldy
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    from UTARRGH!

    I don't really know how I would butt weld in the entire floor of my cutlass.That is how I originally wanted to do it but it would have taken forever. the pros at Goodmark even lap weld the floors in. Seeing that I realized I was being too picky and decided to just lap weld them in and do the best I could.
    here is how the first side turned out.
    [​IMG]
    Here is the size of weld I am dealing with.
    [​IMG]
     
  14. Twisted6
    Joined: May 27, 2007
    Posts: 635

    Twisted6
    Member

    well you could always go back and cut the lap off.IF??????? you have the room to do so. If not then filler it is.But personaly Butt welds ONLY!! Lap joints RUST Out in time. moisture builds up between the lap joints.
     
  15. 29nash
    Joined: Nov 6, 2008
    Posts: 4,542

    29nash
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    ...
     
  16. Frank & Sara
    Joined: Mar 21, 2008
    Posts: 53

    Frank & Sara
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    Lap welding is best left to the production / bodyshop guys. The lap will always be a source of potential corrosion.
    If you'll be keeping your car for a very long time unlike most late model cars at the local body shop, then butt welds are the best way to go.
    It's almost imposable to work a heat warp out of a lap weld.
    This is a very good video on YouTube. Check it out. http://www.youtube.com/watch?v=wntAnn4EowM
     
  17. 29nash
    Joined: Nov 6, 2008
    Posts: 4,542

    29nash
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    ...
     
  18. Zombie Hot Rod
    Joined: Oct 22, 2006
    Posts: 2,452

    Zombie Hot Rod
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    from New York

    Grind the edge and run a bead of seam sealer along it. A week after you put a rug over it you'll forget all about it.
     
  19. roddinron
    Joined: May 24, 2006
    Posts: 2,676

    roddinron
    Member

    Unless you're goin' for the Riddler, since they're already lap welded, I'd just go under the car and fill any seems and gaps with seem sealer, or a good caulking to keep the water out, or duraglass, and then paint it. Then I'd lower the car so no one can see it. :)
    I guess I say this because I've seen so many guys spend so much time on less important things, that they eventually lose interest and never finish.
     
  20. Rusty Kustoms
    Joined: Feb 5, 2006
    Posts: 238

    Rusty Kustoms
    Member

    Your only choice is to buy a can of 3M brushable seam sealer, brush it on heavy, it will look just like the factory seems on all cars, plus it is weather resistant and will seal the lap joint up. There is no point in spreading duraglass or all metal as it will be a pain to sand and finish. Also, if you did not use a weld thru primer expect the lap seam to rot out in a few years.
     
  21. VonMoldy
    Joined: May 23, 2005
    Posts: 1,562

    VonMoldy
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    from UTARRGH!

    I just wish I could afford a TIG like the guy used in the video.
     
  22. VonMoldy
    Joined: May 23, 2005
    Posts: 1,562

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    from UTARRGH!

    I tried to keep the overlap of the metal to about 1". Should I trim the back side all the way to the weld?
     
  23. FiddyFour
    Joined: Dec 31, 2004
    Posts: 9,024

    FiddyFour
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    you really need to learn where to type in a reply with quotes... :rolleyes:
     
  24. FiddyFour
    Joined: Dec 31, 2004
    Posts: 9,024

    FiddyFour
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    your overlap is a bit on the "holy shit, why cover good metal" side. when i make a lap weld, i try to keep it to a minimum. good rule of thumb is no more than your heat effected zone, or the width of the blued steel. a good lap weld works just as well as a butt weld. just lap welds are butt ugly
     
  25. briggs&strattonChev
    Joined: Feb 20, 2003
    Posts: 2,236

    briggs&strattonChev
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    you could do that too. I agree that a butt weld probably would have been a better idea, but since its already done, it will be fine, dont worry about it. Its far from the end of the world.

    If you trim it back, then you wont have that 1" lapped sandwich area anymore, which could be better because its one less place for rust to start again.
     
  26. Frank & Sara
    Joined: Mar 21, 2008
    Posts: 53

    Frank & Sara
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    The TIG is nice but it's biggest benefit is a softer weld.
    The softer weld makes it easer to work the weld and stretch the metal back out.
    As far as trimming back to the weld.......
    Like stated above, the lap weld isn't going to ruin you project. It really depends on if you want to go through all the work of trimming that flange.
    I understand where folks are saying "your done, good enough , move on."
    Your call.

    The only thing I was needing to add to my original post is, Butt weld is a preferred choice of panel repair and is just as fast if not faster then lap weld. It is not the only choice though.
    Take for instance.... if you were panel bonding, I would say a lap joint is OK but still not desirable.
    After all we aren't talking about late model auto body repair but rather restoration? Right?
    If you have a choice, try butt welding next time.

    Just trying to help here.
     
  27. Seam sealer and 3M paintable undercoating. Your are trying too hard and thinking too much!
     
  28. VonMoldy
    Joined: May 23, 2005
    Posts: 1,562

    VonMoldy
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    from UTARRGH!

    Well apparently not since everyone thinks I should have butt welded.

    I plan on double welding the floors. I figure it will be pretty well sealed up is the seam sealer being used here just to hide the weld?
     
  29. roddinron
    Joined: May 24, 2006
    Posts: 2,676

    roddinron
    Member

    I don't know where you're from, never heard of UTARRGH! but guys keep telling you it will rot out, in who's lifetime? I don't know what kind of car you're building but I doubt you're gonna drive it in the slop. It won't rust through if you use it the way most guys use a car they built.
     
    Last edited: Nov 15, 2008
  30. old wood 51
    Joined: Aug 26, 2007
    Posts: 368

    old wood 51
    Member
    from NAPA CA.

    It's o.k., the panels were spot welded in from the factory,and layered on top of the rockers and seam sealed ...sure the orignal floor was one piece... so my .02$ is to weld it fully where it needs to be along with lots of spot welds on the lap over sections and seam seal the whole area , you can smooth the seamsealer out with a little lacquer thinner on a paper towel, just wipe it gently and let it dry ... do both sides then prime it.
    Brian.
     

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