Staggered chop

I picked this up on another forum, but am so impressed with the technique that I thought it was worth sharing here.

Normally to do a roof chop I would need to make a cut across the roof in order to stretch it enough to make the pillars line up. I’m not smart enough to understand why, but by doing a staggered cut on the A-pillar, everything seems to just fall into place.

I tried out this technique today on a ’32 sedan. It took a lot less time than my usual method and will require a lot less clean-up to boot. Here’s the results of half an hour cutting, gluing and reinforcing:

Thanks for the tip man!!

Paul wrote: Thanks for the tip man!!

No probs mate - I honestly can't believe how well it worked!

It's very easily explained Bryce. You take the length of the cut and multiply it by its square root and then divide by 3. I've worked out the math for you:



By the way thanks for the tip!

You've made a mistake in the third line Tezza. Your lambda differential is off by a factor of 23...

Good tip Bryce.

I sure hope one of our resident geniouses(sp) smart asses will 'splain this more betterere.You're just cutting one "A" pillar higher than the other,and then it all lines up? Sounds like I'd need an incantation or two first,maybe some voo-doo,then start cutting. I'm just sayin,I'm flummoxed.

Not only does iw make the A piller line up but it'll make for a stronger joint which might not even need reinforcing.

Wow! Have to try it. Thanks Fred. Bill

Bill Page wrote:You're just cutting one "A" pillar higher than the other,and then it all lines up?

Not exactly Bill...

The cut needs to be a kind of 'Z' shape. If you look closely at the photos above, I have made three cuts on the A-pillar. The first cut is at the front and very low, just above the top of the hinge. Then I made a second cut on the inside of the door frame, just below the drip rail moulding. Both these cuts stopped short of the door shut line. Then I used the back of a blade to scribe through the door shut line, completing the 'z' shape. I needed to trim a little off the door shut line area on both roof and body, but otherwise it went back together very easily. HTH

Thanks kindly,Bryce. I think I've gotten ahold of it. Makes more sense anyway.Your final trimming is to allow for the different pitches of the two sections of the "A" pillar,Yes? Thanks again Bud. Bill

Bill Page wrote:Your final trimming is to allow for the different pitches of the two sections of the "A" pillar,Yes? Thanks again Bud. Bill

Exactly - now you got it.

Effing brilliant. Somebody deserves a medal. I have a 3 window here that needs a trim. Thanks again,Bryce. Bill

WOW thats cool way to chop top.

Thanks for the tip Bryce, it's exactly what i've been looking for. Never tried a full roof chop before but I'm about to give it a go.
Thanks mate.

Roughly how much did you chop out Bryce? 3-4mm?

Well I had a crack at it. Not as clean as Bryce's but for a first timer I think I did o.k. Got a couple of gaps but I'll fix that.

Now I get it. nice work. beat's doin it the cut fill shut way . Thanks again. now does this work on 49 merc's? John.