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Just a little off the top please


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#1 mnwildpunk

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Posted 23 April 2013 - 04:19 AM

So I got the idea to chop a top on one of the models I have in my stash. as I looked at them and I started wondering. I know there will be no definitive answer here. First question is was it just a custom look or did it serve a purpose like for air flow or weight. What cars are are generally chopped? Like I have never seen a 70 roadrunner chopped but why? Lastly I'm thinking of chopping the roof down in my 40 ford P/U do you think I need a second cab?

Edited by mnwildpunk, 23 April 2013 - 04:23 AM.


#2 VW Dave

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Posted 23 April 2013 - 04:48 AM

As I have been told, top chopping was originally done for aerodynamics on dry lakes race cars; the street cars simply picked it up to emulate the racers' style.

 

Any car can be chopped, but not every car should be. If you lay the windshield back on the '40 by pie-cutting the A pillars, IMO there should be no need for a second cab to stretch the top....keeping the windshield at the stock angle, on the other hand, would require a stretch when chopping the top. You oughta be able to Google somebody's in-progress or tutorial on chopping a similar style of truck in 1:1 as well.



#3 Ace-Garageguy

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Posted 23 April 2013 - 09:50 AM

You mean kinda like this ??

 

DSCN4431.jpg

 

VW Dave is dead on as far as the early lakes guys chopping tops to reduce drag by reducing frontal area. Early rodders were smart guys, and they realized pretty quick that it was easier to go faster on the top-end by reducing drag than by trying to get more power out of severely breathing-limited engines. Drag increases with the SQUARE of speed. That means, basically, to go twice as fast, you need FOUR times as much power, three times as fast requires NINE times as much power. Obviously, almost ANYTHING you can do to reduce a car's drag is like a huge shot of free horsepower.


Edited by Ace-Garageguy, 23 April 2013 - 10:00 AM.


#4 Ace-Garageguy

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Posted 23 April 2013 - 10:13 AM

....... What cars are are generally chopped? Like I have never seen a 70 roadrunner chopped but why?

 

The reason you don't see AS MUCH later-model stuff chopped as you do, say, model As and '32 Fords, is because it's a devil of a lot MORE work with steeply raked windshields, wide and contoured C-pillars, and MUCH THINNER SHEETMETAL. Later-model cars also have TEMPERED side and rear glass which CANNOT BE CUT. The '30s  roofs come pretty much straight down, with either gentle windshield pillar re-sloping, or a slight lengthening of the roof. But the more raked the pillars get, the more work is involved to make it look right. I built this 4 scale-inch chopped '70 Chevelle last year, salvaged from a bodged start someone had made chopping it...but after the cuts were taken out, NOTHING lined up even close, and the guy gave up.

 

DSCN5579.jpg

 

Instead of lengthening the roof (which I've seen done on one of these in 1:1 and it looks horrible) I made new, more raked front pillars and completely reworked the C-pillars, which also had to be curved INWARDS from the sides, AS WELL as lengthened and reshaped to flow from the rear. I brought the top straight down at the B-pillars (imaginary), and fitted everything around that relationship.

 

DSCN5426.jpg


Edited by Ace-Garageguy, 24 April 2013 - 01:43 PM.


#5 Greg Myers

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Posted 24 April 2013 - 12:10 PM

I just Googled this https://www.google.c...iw=1280&bih=885 WOW! Lookatem all. :o