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Technical Metalshaping gurus / experienced 'choppers' - Need some advice!

Discussion in 'The Hokey Ass Message Board' started by Surf City, May 19, 2018.

  1. I'm about to split the rear pillars on my '36 3-window chop to match up the smaller radius of the 'top' section to the larger radius at the beltline. I've been thinking it through and am planning on cutting around a 5/8" hole at the top of the crown and removing a tapered section down to the join line.

    My reasoning being, firstly, having a radius at the top rather than a point will avoid concentrating the heat (and distortion) of two welds at a point, and secondly, having the radius will minimize distortion at the top when the lower areas are flared out to meet the beltline. ( I have taken thin tapered sections out of the lower front pillars and closed them up to match the upper pillar profile, and there has been a 'bulge' form at the end of the slit, so I can only assume that spreading the rear pillar areas will cause a 'dimple' or 'sucked in' area at the top of the cut.)
    This will also give me a 'filler piece' of a more consistent width.

    20180519_184801_LI.jpg

    I have also laid a 12" stainless rule across the pillar area, and found that it sits better when laid across at an angle rather than vertically, so am thinking that I will make my cut at a similar angle.
    My intention is to end up with a more streamlined rear roof angle when viewed side on, and I'm thinking that this angled cut will help me achieve that.

    Bear in mind that I am very much an amateur regarding bodywork, so am trying to do this without getting myself into too much difficulty.

    Does this cut/approach make sense to you experienced guys, or am I digging a big hole for myself?

    Any advice, reassuring or otherwise, would be much appreciated...

    Bear:)
     
    Last edited: May 19, 2018
    chryslerfan55 likes this.
  2. Johnboy34
    Joined: Jul 12, 2011
    Posts: 1,588

    Johnboy34
    Member
    from Seattle,Wa

  3. No opinions...?
     

  4. brigrat
    Joined: Nov 9, 2007
    Posts: 5,615

    brigrat
    Member
    from Wa.St.

    I am trying to figure out how you get any sleep at night with all this going on in your head. I would have died of ulcer's a long time ago............................................................
     
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  5. alchemy
    Joined: Sep 27, 2002
    Posts: 20,404

    alchemy
    Member

    So you need to slit the rear quarter of the roof to pull it outward at the bottom to match the belt line. But you are saying you want to remove metal?

    I don't understand. Won't you need to add a strip to fill the wider gap?

    I have in the past made the slit, done the pull, tacked the bottom in place, then gone back and cut the slit wider. Reason for this though is so I wasn't welding a narrow patch, I can instead weld a consistent inch wide parch all the way up. I guess you could round the top of the patch if you wanted to eliminate potential pucker.
     

  6. I plan on removing the tapered section with the radiused top, spreading the two sides out to meet the beltline, then welding in a filler strip which should be close to a consistent width. Same as you have done, just a different approach, and having the radiused top to avoid a potential 'pucker'.

    Bear:)
     
  7. cretin
    Joined: Oct 10, 2006
    Posts: 3,066

    cretin
    Member

    This is a 5 window I chopped back in 2012. This is how I handled that area, hopefully this helps.
    I tried to cut through the apex of the curve, and had to cut up pretty high to eliminate the pucker.

    IMG_3532.JPG

    IMG_3539.JPG
     
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  8. Rckt98
    Joined: Jun 7, 2005
    Posts: 1,132

    Rckt98
    Member

    Bear, perhaps try and get hold of Kenny Baker, Chopper Rod Shop, Elmer Missouri.
    He is a member on here "choprods" but hasn't been here for a couple of years.
    Have a look at his profile page, his e mail address is there. He has chopped hundreds of cars.
    I have been to his shop, a good guy. Tell him Russell from NZ sent you.
    I have been following your build thread, the coupe is looking great.
     
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  9. Bear, have you spoken at all to Mike Roberts? He’s always very helpful with advice if he sees someone wanting to genuinely give it a go as you’ve already proven this with the whole build.
    Thanks
    Greg


    Sent from my iPhone using H.A.M.B.
     
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  10. beater32
    Joined: Mar 23, 2008
    Posts: 368

    beater32
    Member

    What he said!

    Sent from my ZTE R84 using The H.A.M.B. mobile app
     
  11. Halfdozen
    Joined: Mar 8, 2008
    Posts: 632

    Halfdozen
    ALLIANCE MEMBER

    I've cut two '35 three windows, in both cases I did it this way:
    -cut the entire rear corner of the top out, leaving a strip above the body line.
    -remove desired amount at door opening, in this case four inches.
    -cleco the corner in place.
    -tip the lower edge forward to match the slope of the corner tail.
    -scribe, cut, fit, tack and weld back in place.
    -repeat other side.

    If you can, tig weld all areas of the skin, this makes it possible to shape the panel with hammer and dolly.
    Mig welds are hard and tough to shape.

    Hard to describe in words, hopefully pics show the process. Both cars had the rear window replaced with a sedan piece, you could use this approach while retaining the original window also.

    JStGchop23.JPG JStGchop21.JPG JStGchop22.JPG JStGchop29.JPG JStGchop65.JPG JStGchop 001.jpg
     

    Attached Files:

  12. brigrat
    Joined: Nov 9, 2007
    Posts: 5,615

    brigrat
    Member
    from Wa.St.

    ^^^^^^^^^^^^Now that takes a lot of balls!^^^^^^^^^^^^^^^
     
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  13. COCONUTS
    Joined: May 5, 2015
    Posts: 1,161

    COCONUTS

    Hey load your car up and take it over to this guy's house, he really knows what he is doing, unlike me. TIG is the way to tack. don't add any filler rod, just melt the metal together. MIG leaves to much of a big bump, which means grinding and grinding means heat.
     
  14. Big curves and small slivers added in usually don't make nice tansitions.
     
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  15. Thanks for the reply, Halfdozen.
    WOW! That just switched a light back on inside my head.
    Plan A was going to be slicing right across the roof at the crown above the back window and removing a crescent shaped section, then lifting and rolling the rear section forward, to achieve something very similar to what you have done. There were two things that stopped me - one being that I wanted to lower the rear window down towards the beltline, and the other that the thought of cutting that big of a piece scared the shit outta' me.
    Actually cutting it wasn't the problem, I just knew I was going to run out of talent real fast when it came time to stitch it all back together.

    Having now seen your pictures, I can see that cutting out and repositioning the rear corners isn't going to involve a whole lot more welding than doing a vertical splice up through the rear pillar. And 31Vicky's comment about 'big curves and small slivers' reinforces a concern I have had with that method, particularly as I have minimal experience with forming compound curve panels.

    I keep seeing pics where the real pro guys are wheeling up new sail panels (particularly for 40s and 50s era chops) to get nice smooth transitions. Seeing your pictures made me realize that I might already have those pieces hanging down out of sight behind the beltline! (Luckily I haven't cut anything off yet;))

    20180519_184801_LI (2).jpg

    I'm going to cut some templates of the curves tomorrow and move them around on the body to see whether I think I can pull this off.

    Bear:)
     
    Last edited: May 21, 2018
  16. Halfdozen
    Joined: Mar 8, 2008
    Posts: 632

    Halfdozen
    ALLIANCE MEMBER

    In my opinion, a successful chop requires planning- know where and how much you're going to cut before you start. Here's how I do it: make one inch checkerboard strips with cardboard and a sharpie, stick 'em to the car, take pics, cut up pics till you like the shape of the profile, read resulting dimensions off the cardboard strips.
    35chop layout.jpg

    I agree with 31Vick, I don't like small slivers.
    I can't stress enough that IMO tig welding is the best way to do skins. Oxy acetylene would be second choice, especially with a Dillon/ Henrob/ Cobra torch. Keep the heat affected zone to a minimum- *BUTT JOINTS ONLY*. Remember that anything you weld WILL SHRINK to smaller-than-original dimensions when it cools. Hammering the weld on-dolly after it cools will return it to pre-welded shape.
    Surf City, so far, your metal work looks great. I'll be watching this one. Press on. :)
     
  17. Halfdozen
    Joined: Mar 8, 2008
    Posts: 632

    Halfdozen
    ALLIANCE MEMBER

    Just refound this: JStGchop7.JPG

    This also helps match the slope of the rear window to the slope of the deck lid.
     
    Last edited: May 21, 2018
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  18. Halfdozen
    Joined: Mar 8, 2008
    Posts: 632

    Halfdozen
    ALLIANCE MEMBER

    Actually, for ease and speed I often tack with mig. Trick is to use .023 Esab Spool Arc Easy Grind wire, grind the tack flat and wire wheel it before running over it when tig welding the seam. Don't forget that the back side of the panel needs to be paint and rust- free before welding too.
     
    Last edited: May 21, 2018
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  19. brigrat
    Joined: Nov 9, 2007
    Posts: 5,615

    brigrat
    Member
    from Wa.St.

  20. So I ran a profile gauge over the rear pillar area and figured out where the curves were the most consistent, and marked out some cut lines, then carefully cut off that section with a thin disc, (bearing in mind that all of the original rear pillar material was still attached, just hanging down inside the body, prior to this cut).

    20180528_184026.jpg

    I sat the removed piece out and over the hole sliding the patch up so that the lower edge was almost back in it's original position ( there was now around a 3 1/2" overlap at the top which was going to make it difficult to tightly fit it on the inside of the rear pillar). Once I figured out how much material I was going to need, I rough cut the top off the patch, giving me about 3/4" extra panel to work with.
    Then I test fitted it on the outside once again, checking that the curves all matched up nice.

    20180529_214515.jpg

    20180529_214503.jpg
    Then I blued up the panel, test fitted and tightly clamped it to the inside of the hole, and scribed a cut line.

    20180529_224251.jpg

    20180529_224707.jpg

    20180529_224415.jpg

    Trimmed the piece to a nice fit, then clamped it in place.



    20180731_192832.jpg

    20180731_192844.jpg


    I guess I won't know for sure until I have cut and fitted the door, but right now I'm pretty sure I've got the profile exactly where I want it, just enough additional slope in the rear window angle to avoid the 'bulge' that comes with a more traditional chop, but not enough to make it look like a "wanna' be Zephyr":D
    20180804_113022 (2).jpg

    Bear:)
     
    Last edited: Sep 2, 2018
  21. jetnow1
    Joined: Jan 30, 2008
    Posts: 2,152

    jetnow1
    ALLIANCE MEMBER
    from CT
    1. A-D Truckers

    That looks awesome, your work looks impeccable.
     
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  22. Halfdozen
    Joined: Mar 8, 2008
    Posts: 632

    Halfdozen
    ALLIANCE MEMBER

    Nicely done!
    IMO, the calculated approach always results in the nicest finished product. You obviously share that opinion- your careful measurement, layout, scribing, cutting and trimming have resulted in very nice fitup, which makes welding much easier. You can then fine tune the final shape with hammer and dolly. Very little filler required. Excellent work. NF3window6.jpg

    Personally, I like the "wanna be Zephyr" look. I cut a little higher into the crown and leave more of the flatter tail at the beltline. It more closely matches the slope of the rear pillars to the slope of the deck lid. A subtle difference, noticeable when you compare two different cars.
     
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  23. patsurf
    Joined: Jan 18, 2018
    Posts: 1,025

    patsurf

    i think these kiwi and canuck fellas have a pretty good grasp of american tin..bravo!!
     
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  24. JEDI363W
    Joined: Jan 13, 2016
    Posts: 24

    JEDI363W

    You mentioned that you cut where the radius was consistent. Where they cut more to the top of the radius or in apex or more to the end of the radie?

    Sent from my SM-G960F using The H.A.M.B. mobile app
     
  25. oldsman41
    Joined: Jun 25, 2010
    Posts: 1,556

    oldsman41
    Member

    You did fine surf city. I didn’t have anything to add after reading half dozens account that is the way i did it so why muddy the water. Good work tig if possible and really go slow watch the heat.
     
  26. So here's where I'm at now, thanks everyone for the feedback.

    20181125_193110.jpg

    20181125_193159.jpg

    Just a whole bunch of welding and hammering to do......

    Bear:)
     
  27. That came out very nice
    Well done
     
    Surf City likes this.

  28. Sorry for the late reply...

    In the side on shot of the roof you can see the cut line across the roof. You'll notice that there is a fairly consistent radius just to either side of the line before it starts to straighten out for the roof and also for the back window section of the pillar. That radius was fairly consistent through the section I removed from the top of the 'patch', so by taking it out of there, the curves mated up nicely at the join.:confused: So I guess what I'm saying is that I removed metal from the upper section of the consistent radius.
    If you can imagine that radius continuing down around 4 inches from the cut line, you will also get an idea of how far the 'patch' section was laid forward to mate up with the roof.
    Hope that all makes sense!:D

    Bear:)
     
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