Why does it seem that all the early "C3" racing corvettes were convertibles??
02-01-2015, 11:36 AM
#22
Instructor
Thread Starter
I know this is old, but I had some more insight on this:
If they were worried about weight and aerodynamics, wouldn't a coupe with the side windows down and the rear window out provide less drag, less weight, more aero, and more downforce than convert hardtop car? I think if I was building an early C3 road race car today, that may be my best option, right?
If they were worried about weight and aerodynamics, wouldn't a coupe with the side windows down and the rear window out provide less drag, less weight, more aero, and more downforce than convert hardtop car? I think if I was building an early C3 road race car today, that may be my best option, right?
02-01-2015, 02:22 PM
#23
Le Mans Master
another couple things, the first part of 68 they only made convertibles and there was more room for roll bars in a convertible, and easier access to install one.
02-01-2015, 08:11 PM
#24
I have a big corvette poster in my garage . It's old like me.,,, 
. It's been up in Garages 30 plus years . A lot of old school racing .
A lot of racing C3 in it too.
Every one is a convertible that is racing on that poster
Either with a hardtop or raced as an open roadster. I love those pics .
It was aerodynamic deal.....they were slicker model at that point in time.
. It's been up in Garages 30 plus years . A lot of old school racing .A lot of racing C3 in it too.
Every one is a convertible that is racing on that poster
Either with a hardtop or raced as an open roadster. I love those pics .
It was aerodynamic deal.....they were slicker model at that point in time.
02-02-2015, 09:09 PM
#28
Race Director
If they were worried about weight and aerodynamics, wouldn't a coupe with the side windows down and the rear window out provide less drag, less weight, more aero, and more downforce than convert hardtop car? I think if I was building an early C3 road race car today, that may be my best option, right?
First off, in some series such as FIA International endurance racing, if the car had a roof, then it was required to run full glass. A convertible with a hardtop was also required to run full glass, while an open car was only required to run a windshield. So in some series, if you were running a closed body, you had to have all of the glass in place.
A 68-75 convertible with a hardtop on it, is more aerodynamic than a 68-77 coupe. Air flows much better over the hardtop's rear widow, than the coupe's tunneled one. A convertible without a hardtop, and a cut down windscreen, will also be more aerodynamic, than a coupe with a full windshield, even with the tops and glass removed. The big rear window 78-82 coupe body, is the only closed body that is aerodynamically superior, to the 68-75 convertible with a hardtop on it.
The SCCA allowed coupes to run without door glass, and the rear window and t-tops removed, but they were still required to run a full stock windshield. Up until around 1980, the SCCA allowed convertibles to run a cut down windscreen, giving them a decided aerodynamic advantage, over a coupe. Take a look at the two pictures below. Even with a full cage, the black #93 is obviously more aerodynamic, than the #71.
A convertible with or without a hardtop, is lighter than a similar coupe. For racing, both a convertible (with or without a hardtop) or coupe body, would be gutted of all extra weight (headliners, moldings, seats, wiring, etc). Once gutted, even with a hardtop, a convertible is going to be lighter, just by the simple fact that it doesn't have the extra weight of the coupe's birdcage. The actual extra weight isn't that big a deal, as both bodies were required to meet the same minimum weight. The problem with the coupe's extra weight, is where it's at. The extra weight of the birdcage is up high in the body, causing the coupe to have a slightly higher center of gravity.
Very few race cars, used a full cage in the 60's and 70's. Prior to about 1980, all that was required by the SCCA was a roll bar, not a full cage. Only unit body cars, like Mustangs and Camaros used cages, and they used them as a means of strengthening the car's structure, more than for added safety.
When building a race car, with a fully gutted interior, there really isn't much difference in putting a roll bar into a coupe or convertible. Especially when that coupe is a t-top.
02-02-2015, 11:18 PM
#29
Tech Contributor
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The following is based on what I learned from crewing on a BP Solo Corvette in the late 70's, building a GT-1 Corvette in 81, and from playing with Corvette vintage racers for the last 10 years.
First off, in some series such as FIA International endurance racing, if the car had a roof, then it was required to run full glass. A convertible with a hardtop was also required to run full glass, while an open car was only required to run a windshield. So in some series, if you were running a closed body, you had to have all of the glass in place.
A 68-75 convertible with a hardtop on it, is more aerodynamic than a 68-77 coupe. Air flows much better over the hardtop's rear widow, than the coupe's tunneled one. A convertible without a hardtop, and a cut down windscreen, will also be more aerodynamic, than a coupe with a full windshield, even with the tops and glass removed. The big rear window 78-82 coupe body, is the only closed body that is aerodynamically superior, to the 68-75 convertible with a hardtop on it.
The SCCA allowed coupes to run without door glass, and the rear window and t-tops removed, but they were still required to run a full stock windshield. Up until around 1980, the SCCA allowed convertibles to run a cut down windscreen, giving them a decided aerodynamic advantage, over a coupe. Take a look at the two pictures below. Even with a full cage, the black #93 is obviously more aerodynamic, than the #71.
A convertible with or without a hardtop, is lighter than a similar coupe. For racing, both a convertible (with or without a hardtop) or coupe body, would be gutted of all extra weight (headliners, moldings, seats, wiring, etc). Once gutted, even with a hardtop, a convertible is going to be lighter, just by the simple fact that it doesn't have the extra weight of the coupe's birdcage. The actual extra weight isn't that big a deal, as both bodies were required to meet the same minimum weight. The problem with the coupe's extra weight, is where it's at. The extra weight of the birdcage is up high in the body, causing the coupe to have a slightly higher center of gravity.
Very few race cars, used a full cage in the 60's and 70's. Prior to about 1980, all that was required by the SCCA was a roll bar, not a full cage. Only unit body cars, like Mustangs and Camaros used cages, and they used them as a means of strengthening the car's structure, more than for added safety.
When building a race car, with a fully gutted interior, there really isn't much difference in putting a roll bar into a coupe or convertible. Especially when that coupe is a t-top.
....
First off, in some series such as FIA International endurance racing, if the car had a roof, then it was required to run full glass. A convertible with a hardtop was also required to run full glass, while an open car was only required to run a windshield. So in some series, if you were running a closed body, you had to have all of the glass in place.
A 68-75 convertible with a hardtop on it, is more aerodynamic than a 68-77 coupe. Air flows much better over the hardtop's rear widow, than the coupe's tunneled one. A convertible without a hardtop, and a cut down windscreen, will also be more aerodynamic, than a coupe with a full windshield, even with the tops and glass removed. The big rear window 78-82 coupe body, is the only closed body that is aerodynamically superior, to the 68-75 convertible with a hardtop on it.
The SCCA allowed coupes to run without door glass, and the rear window and t-tops removed, but they were still required to run a full stock windshield. Up until around 1980, the SCCA allowed convertibles to run a cut down windscreen, giving them a decided aerodynamic advantage, over a coupe. Take a look at the two pictures below. Even with a full cage, the black #93 is obviously more aerodynamic, than the #71.
A convertible with or without a hardtop, is lighter than a similar coupe. For racing, both a convertible (with or without a hardtop) or coupe body, would be gutted of all extra weight (headliners, moldings, seats, wiring, etc). Once gutted, even with a hardtop, a convertible is going to be lighter, just by the simple fact that it doesn't have the extra weight of the coupe's birdcage. The actual extra weight isn't that big a deal, as both bodies were required to meet the same minimum weight. The problem with the coupe's extra weight, is where it's at. The extra weight of the birdcage is up high in the body, causing the coupe to have a slightly higher center of gravity.
Very few race cars, used a full cage in the 60's and 70's. Prior to about 1980, all that was required by the SCCA was a roll bar, not a full cage. Only unit body cars, like Mustangs and Camaros used cages, and they used them as a means of strengthening the car's structure, more than for added safety.
When building a race car, with a fully gutted interior, there really isn't much difference in putting a roll bar into a coupe or convertible. Especially when that coupe is a t-top.
....
02-03-2015, 12:32 AM
#30
Race Director
The body was made up of 5 pieces of fiberglass. A nose, rear clip, hood and two door skins. The rear clip was just one large, light weight piece. All of the fiberglass was attached to the roll cage by quick release Dzus fasteners. The only part of the body that was from a stock Corvette, was the cowl and windshield frame.
We were able to build the car that way, because it was built under the SCCA's later, more liberal GT-1 rules. The two cars pictured in my previous post, were built to the earlier SCCA AP/BP and Trans-Am I & II rules, which were much more restrictive. I'm not as familiar with the earlier rules, as I was never involved in a car that had to race under those rules, but I don't think they would have allowed the removal of the birdcage.
The first picture below, is the Corvette we built in 81. The second picture is of Greg Pickett's Corvette at Summit Point, after being rear ended by ***** T Ribbs. Pickett went on to finish the last 7 or 8 laps, with the rear bodywork missing. This picture gives you a good idea of how little of the stock Corvette was being used by the 80's.
02-03-2015, 11:55 AM
#31
Instructor
Thread Starter
I hope this is clearly stated:
So if I wanted to build today the best/max performancing 68-69 corvette from one of these two following setups, it would still be the convertible body with side windows down and hardtop on (my preference if convert.) over the coupe body with t-tops on (my preference if coupe) with side windows down and rear window out??
This is my understanding from this conversation. At speed, I would think air would get trapped under the hardtop versus be able to escape with the rear window out on a coupe.
Thanks for all of your input!
So if I wanted to build today the best/max performancing 68-69 corvette from one of these two following setups, it would still be the convertible body with side windows down and hardtop on (my preference if convert.) over the coupe body with t-tops on (my preference if coupe) with side windows down and rear window out??
This is my understanding from this conversation. At speed, I would think air would get trapped under the hardtop versus be able to escape with the rear window out on a coupe.
Thanks for all of your input!
Last edited by JCPerformance; 02-03-2015 at 12:51 PM.
02-03-2015, 04:44 PM
#32
Racer
An old thread, but from my short road-racing career, my .02 -
2 things:
- Cages were easier to put in a roadster.
- Roadsters were a LOT easier to see out of.
walt z.
2 things:
- Cages were easier to put in a roadster.
- Roadsters were a LOT easier to see out of.
walt z.
02-05-2015, 12:01 PM
#33
Safety Car
No body knows more than the googler and all that the googler says is true....I'm still waiting for that Nigerian princes to deposit that huge sum of money in my account while I try to figure out what happened to the money that I had...
