Tudor Update: Angle-Chopping a ’28 Ford

Preparation:

I removed the rear window wood, but left the cowl/gas tank in place to add rigidity.
Old paint & rust was sanded off- both inside & out- in the areas to be cut/welded.



Plotting Cut Lines:

I wanted to ensure interior room for four, while retaining good forward visibility despite a planned huge rake.
I used trigonometry in an excel spreadsheet to calculate how much to cut from each post; starting at 3.5“ at the windshield gasket surface; and decreasing to 2.5” at the back window. The roof is 80.0” long and it actually works out to just about 1 degree of slope.

Distance from windshield (in.) / Chop amount (in.) / Location
0.0 / 3.50 / Front of windshield
29.3 / 3.13 / Center of door's B-post
31.0 / 3.11 / Center of body's B-post
62.0 / 2.72 / Rear edge of rear side window
80.0 / 2.50 / Rear edge of back window

I spread blue dykem (a thick sharpie marker would’ve been almost as good for less $) on entire circumference of A- B- and C-posts and the sail panel. Then I scribed cut lines completely around posts, using dividers to make EXACT lines.


A-posts: Cut lines were near the bottom, where width is constant. This simplified realignment work later. I followed Jimmy ‘Shine’s example- cutting below the windshield stud- allowing it to swing out with no change in geometry.



B-posts: In addition to the cut lines, I scribed reference lines where the door edges overlap the B-post & roof. This simplified tacking and realigning the doors.


C-posts and sail panels: Instead of cutting straight across, I dropped the cut line down to the beltline where the metal is stiffer, then turn back up to the rear window. This was supposed to minimize distortion & eliminate the need for vertical relief cuts. As you’ll see later, it didn’t work- relief cuts were still required to align everything.

I adjusted one of the cut lines in order to remove a spot of thin/rusty sheetmetal near the passenger side C-post.


The doors were marked at same time as body.

Here’s a temporary triangulated framework, as high as possible, just below cut lines.


The haircut:

We remeasured twice before cutting, then used three different tools; a Dremel to start the cuts precisely on the lines, a cutting blade on a 4 ½” grinder for the posts, and a skil saw for the sail panel sheetmetal.


We started at the A-post & worked back, making top cuts first, so it would be easier to cut scrap pieces off the body.


The obligatory “lifting-the-top-off-for-the-first-time” photo.


Thanks to my friends- Bob Dufrane and Bob Henry- for their help.

 

After whacking off the top, we made the bottom cuts and saved the scraps for later.
We put the roof back on the body; it rested on the A-B- and C-posts, while the upper sail panel hung over the lower sail panel around the curve of the rear corners.

I followed Rolf’s lead- flipped over the loose roof, then wire-brushed the inside. Then I cleaned/deburred the edges with a file, then use a sanding disc to make nice shiny metal on top & bottom, inside & out.


Removing overlapping sheetmetal around the sail panel’s curvature:

I’d only cut a straight 2.5” slice around the sail panel. This left a wedge-shaped sheetmetal overlap due to the different cuts on the A- B- and C-posts. It started at 0.22” (2.72”-2.5”) near the C-posts, sloping around the sail panel’s curvature to nothing at the back window.

I squeezed the 2 layers together and trimmed them so they’d butt together. I also had to cut vertical reliefs so all the curved sailpanel metal would align. Unfortunately, I neglected to take pics.

Welding the Posts:



The wood in the B- and C-posts was still solid, so I decided not to replace them. Instead, I installed 1” sleeves in them (~1/2” above & below butt seam). Sleeves eased post alignment and created a stronger joint due to both butt & lap welds. They also eliminated blow-through when welding the seams.

I also drilled 5/16” vertical holes in the wood posts (1” in the top and 1” in the bottom) and inserted 2” x 1/4” diameter alignment pins.

Tacking everything together…





I kept all three door hinges to minimize door sag and maximize rigidity.


The A-posts both CURVE and TAPER from top to bottom and the angle chop ACCENTUATED this curve. I also had to ensure the windshield gasket surface was straight and keep all three hinges aligned. If they’re misaligned, the posts will look like giant S-curves, the doors will bind and the windshield will leak. I ran a metal rod through the 3 hinges to maintain alignment and rechecked regularly via eyeball and straightedge.

I cut vertical slices and spread/squeezed everything, using lots of C-clamps, wood blocks and vice grips.


It took three tries to get ‘em straight.

Doors:



I cut and tacked the doors simultaneously with the A- and B-posts.


First, I hung the lower door-half on its two hinges and the upper door-half was hung on upper hinge. I’d cut the doors a little long and “snuck up” on exact fit, then tacked them together while matching dykem scribe overlap lines on roof & B-post.

Clamps & lumber kept the doors straight while a copper backing plate kept me from welding them to the body.





After the doors’ outer skins were tacked together, I focused on getting their window channels aligned to ensure the windows roll up/down smoothly.

Here are some vertical relief cuts. The narrow top part is spread apart, bottom wide part is squeezed together. I used more hardwood & c-clamps to keep the doors and window channels straight.

I continuously rechecked doorjamb clearance, hinge alignment, and windshield surface flatness. If something wasn’t quite right, I cut the tack(s) and fixed it. TAKE YOUR TIME.



Then I attacked the sail panels, starting at the vertical seam and working outward. Notice I’d removed some sheetmetal around the B- and C-posts. This allowed access to weld the sleeves together.

 

All tacked together. Now it’s time to crank up the voltage for proper penetration.




First the doors:



…then the A-posts.




When filling between between the sail panel tacks, I bounced around and alternated between welding from the interior, then outside. This minimized heat build-up and warpage while still getting decent penetration.


After finish welding the B- and C-posts’ sleeves, I cut vertical relief slices to align the window channels, then made patches from the chop scraps.

I spread/squeezed the sheetmetal to align the window channels, then tacked the vertical slices and patches…




…then finish welded ‘em…

 

…and finally spent several hours of quality time with a grinder/flap wheel, hammer& dolly, and one of John Kelly’s shrinking discs (aka: “The Screaming Disc of Flatness” ):





Here’s the finished product with a temporary coat of rattlecan primer. I’ll do the windshield and garnish moldings later.

So whatta ya think?

Bibliography:
HAMB chop threads (there are millions- do a search)

Chopping a Model A the Jimmy Shine Way, Rod & Custom July ‘08
Top Chop Tricks, Rod & Custom, Oct ‘01
Deuce Chop a la De Ley, Street Rodder, June ‘00
Chopping An A-Bone, Rod & Custom, June ‘95

 

lookin good

 

looks good, clean chop

 

I like the inserts you put in the pillars.

 

Haha, I saw the pic with the dremel and thought "No way he's gonna chop it with that!"

Great thread. Looks good!

 

Some great handy tips. Nice job!

 

Very nice !

 

Hahaha! Me too, I laughed outloud when I saw that.

Excellent work, though! Looks fantastic!.

 

Great looking chop

 

Very nice work, Very mathy

 

Very nice chop, wow Trigelementry who'd a thunk it.

 

beautiful job fellas. Impressed with the cleanliness of the job. great work!

 

Thanks for the positive words, guys.

Ha ha ha... I just used the dremel to start the kerfs-- would've died of old age had I used it any more...

Yeah- I want it as stiff as possible but there's no room for a roll bar if the back seats are still accessible.

 

Absolutly gorgeous work. enough said.

 

Looks good! This one got an angle chop all on its own! No trig required!

 

huh.......???????

 

looks great !

 

great tech..some good tips ....lookin good

 

good looking chop, nice work.

 

Very good tech, nice to see lots of pics and a detailed how to, it gives a good idea on what goes into a good chop, awesome job!

 

Never fails. Every post I see on chopping a Model A makes it look so Easy I'm ready to run out in the garage and tackle mine. I get about as far as taping it up and marking it before chickening out......again.
Your chop does look great.

 

Great post, great pics.

 

Nice job, They always look good with a full rear window vs. mail slot.

 

This is awsome information!

 

great work , great documentation, great result (although I can't help but think..."another 1" to give it attitude..."

TECH thread

Look forward to seeing the remainder of the car.

Cheers,

Drewfus

 

Nice job.I like the fact that you show these guys how to cut a access opening to weld the innerstructure for strength.I have seen guys leave the innerstructure that they can't get to unwelded. NO NO !

 

Good tech post that i will keep in mind when ever i finally get my sedan chopped. Very cleanly done