Trunk floorpan cutting advices needed

Exterior, Paint & Bodywork

  1. Chrome58

    Chrome58 Active Member

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    Hello,

    I'm restoring the trunk floorpan of my '70 Plymouth. There was already a big chunk missing in the center. After applying wire wheel, more holes appeared, but that was no surprise ... I'm going to do the metal fabrication myself, but I'm not experienced (actually it will be my first time with a bead roller).

    On the pictures you can see I have outlined (black line) the area where (I think) I will need to cut.

    What would you suggest and/or what would be your advices about that cutting ?

    Thank you.

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  2. CBODY67

    CBODY67 Old Man with a Hat

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    Be sure to allow enough "flange area" for a good overlap of the old and new metal, for good structural integrity when done. Then coat with a quality metal prep/rust preventative coating when done, plus seam sealer, prior to any paintwork. Keep us posted.

    Just some thoughts,
    CBODY67
     
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  3. RGORHAM29

    RGORHAM29 Member

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    keep us posted on your progress. I will need to do some patching myself in the trunk - like you - not much fab experience. Good luck!
     
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  4. Chrome58

    Chrome58 Active Member

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    And by "flange area", I imagine you're speaking of either one of the 2 solutions below, right ?

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  5. FinFury

    FinFury Member

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    Just my opinion, forget the flanging, making a decent butt weld really isn't that hard and then you won't have any sandwiched metal waiting for corrosion to happen. Of course it is faster and somewhat easier to fix by doing the blue lined flanges with a tool made for that
     
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  6. 1970cat

    1970cat Senior Member FCBO Gold Member

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    the left looks good although you might have a hard time near the spare tire mount. you need to leave room for grinding too. for the right side i would go about 1/2-3/4 of an inch more to the right. the metal looks pretty thin where you have it outlined. keep in mind there is a flange on each side where the trunk floor and drop off meet. look underneath and you'll see what i mean. be careful not to cut the frame rails or the fuel tank brackets off.
     
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  7. CBODY67

    CBODY67 Old Man with a Hat

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    The "blue line" flange is what I was thinking of. Rather than welding such flanged items, there is an aircraft-grade adhesive that is used to replace roof panels on late-model cars, where spot welding isn't a real option, from what I'm told. IF such a thing exists, then it could be spread onto the flanged area, then use screws to hold it in place until it dries. Or possibly use pop rivets? Then grind off the screw heads and exposed threads, apply seam sealer prior to paint. Might look in the 3M Body Shop Supply catalog? Just my theory of doing it and not having to do welding. No more, no less.

    Seems like Eastwood sells a flange tool for panel repairs?

    Take care,
    CBODY67
     
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  8. Chrome58

    Chrome58 Active Member

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    Yes, I know about that metal panel adhesive. It is used even in new car manufacturing, in some areas. I've already seen it at a car assembly plant (I work in the automobile industry). And they claim it is as strong as a weld.

    61FjHTCGR1L._AC_SX425_.jpg

     
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  9. James Richardson

    James Richardson Active Member

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    If flanging then adhesive is far superior
    If welding then butt weld. You can cut out leaving a little extra on floor and laying new piece over top with on end butt fitted. Use thin blade to trim extra as you fit and tack it. Like carpet fitting. A .045 disc leaves a perfect gap
     
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  10. CBODY67

    CBODY67 Old Man with a Hat

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    Might a butt weld need to be done in segments, so as to not heat the surrounding metal too much, which might warp it a bit? Just curious.

    CBODY67
     
  11. James Richardson

    James Richardson Active Member

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    Absolutely. Tack about an inch apart all the way around. Tack in middle.....tack in middle till filled in. Go slow and blow cool as you go. Rounded corners reduce warping but complicate install. Not seriously necessary in trunk really.
     
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  12. MrMoparCHP

    MrMoparCHP Senior Member

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    When I removed pieces from my floor pan I cut alongside the frame rail flanges then peeled the remaining strip off. As you roll it off it will stop at a spot weld, cut/grind, continue.


    Alan
     
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  13. Chrome58

    Chrome58 Active Member

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    Well, here is the first step done ...

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  14. azblackhemi

    azblackhemi Old Man with a Hat FCBO Gold Member

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    When butt welding make sure to leave a little gap between the two pieces. If they are too close together when they expand from the heat they will rise up into a peak.
     
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  15. RGORHAM29

    RGORHAM29 Member

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    Rails look to be in decent shape. I would clean those up too and paint to protect them another 50 years since they are accessible.
     
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  16. Chrome58

    Chrome58 Active Member

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    Well I just did ...
    Had to paint the upper lips too, because I do not know when I will be able to weld (or glue) the new floorpan.

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  17. Rustyrodknocker

    Rustyrodknocker Active Member

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    My biggest take aways from welding sheet metal over the years is take the time to get the fit up correct. When using a mig gun I like a 1/16" .
    Tack opposing sides as you fit to keep the panel from pulling to one side and creating a gap on the other.
    Tack your way around until there is a tack every inch.
    When it comes to weld out you tack on the edge of the previous tack. You can zap it, wait for the color to disappear and zap it again. You can do this 2-3 times the move to a different place. When working a small area you will have to stop and wait and or cool with air hose.
    Grinding beads is the same. Avoid excess heat input. Getting in a hurry with lead to shrinkage and buckling.

    Here is a video of a guy that does great work. He explains his methods in several videos. I have used them with good result.

     
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  18. RGORHAM29

    RGORHAM29 Member

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    Progress?