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Old 11-27-2010, 05:04 PM   #1
JCPerformance
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Default Why does it seem that all the early "C3" racing corvettes were convertibles??

Any 1968-72 corvette racing knowledge would be helpful.
I thought converts were heavier? Is it because converts were more plentiful?
or some other reasons I'm not aware of?

Thanks
John

Last edited by JCPerformance; 11-27-2010 at 05:06 PM.
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Old 11-27-2010, 06:00 PM   #2
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I don't believe a higher ratio of verts. When you cage a race car it doesn't matter if it has a top or not. Racing has weight limits.

I don't like sitting in the sun. The short window verts might have less drag.

Did you know that c-3 verts cost less to buy than a coupe? So if cost was a thought???

Last edited by gkull; 11-27-2010 at 08:50 PM.
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Old 11-27-2010, 06:28 PM   #3
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I read/heard less less drag for the back window compared to the coupe. 78 and up even slicker aero.
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Old 11-27-2010, 06:36 PM   #4
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lower center of gravity and lighter
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Old 11-27-2010, 08:40 PM   #5
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The C3 convertible hardtop has better aerodynamics than the flatback window. That is why that body style was used at LeMans and Daytona.
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Old 11-27-2010, 08:59 PM   #6
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Quote:
Originally Posted by SteveG75 View Post
The C3 convertible hardtop has better aerodynamics than the flatback window. That is why that body style was used at LeMans and Daytona.
I have read that. A little googling should turn up a quote or 2.
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Old 11-27-2010, 09:09 PM   #7
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Quote:
Originally Posted by PRNDL View Post
I have read that. A little googling should turn up a quote or 2.
Sorry. Figured you guys know more than google...
thank you.
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Old 11-27-2010, 09:16 PM   #8
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Although I've never really looked on mine, I was under the impression that the vert frames had some extra gusseting, somewhere, for stiffness, and that was the reason many chose them for a race car. Less frame flex. Of course, I may have read that in an old article or something and it could be totally wrong. Age does mysterious things to the mind. That's one of the reasons I retired from teaching after 35 years.
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Old 11-27-2010, 10:24 PM   #9
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Frames where the same.
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Old 11-27-2010, 10:36 PM   #10
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Yea the frames are the same but in stock form the vert body had more bars under the dash to help them out. After building many cars for track use I think mainly would've been the eas in putting roll bars/cages in without more work of cutting roofs off and putting back on it usally is that simple and others will chime in that it had to be more than that through history, maybe who knows for sure other that the team that did it. .
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Old 11-28-2010, 10:54 AM   #11
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Quote:
Originally Posted by Manuel Azevedo View Post
After building many cars for track use I think mainly would've been the eas in putting roll bars/cages in without more work of cutting roofs off and putting back on it usally is that simple and others will chime in that it had to be more than that through history, maybe who knows for sure other that the team that did it. .
While I'm sure the aero advantage, lower center of gravity, lighter weight were all a consideration being able to prepare the car with the roof out of the way had to make life easier.
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Old 11-28-2010, 11:01 AM   #12
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Quote:
Originally Posted by JCPerformance View Post
Sorry. Figured you guys know more than google...
thank you.
I only meant to substantiate the answer... but I have googled and gaggled and goggled and can't find anything.
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Old 11-28-2010, 11:21 AM   #13
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Default the reason is

because in68chevrolet only built convertables till late in the yearbeacause of the hatch roof it was designed to be one piece and we know how that worked out.
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Old 11-28-2010, 11:57 AM   #14
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Quote:
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because in68chevrolet only built convertables till late in the yearbeacause of the hatch roof it was designed to be one piece and we know how that worked out.
They ended up going with 2-pieces (t-tops).....

So in 1969 they raced converts and coupes??

...just seems I only see pics of converts.

Last edited by JCPerformance; 11-28-2010 at 12:02 PM.
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Old 11-28-2010, 12:39 PM   #15
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Was going to reply earlier and wait for answers from those who know the reason. I was going to post this:

They probably weren't verts but had the roofs cut off.

Roll bar cages would be easier to fit with no roof.

Some classes you can't have a swing out side bar so getting in would be easier, just go over the door.

These are just guesses
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Old 11-28-2010, 01:10 PM   #16
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most of the racers built cars in68 and instead of building a new unproven car they just updated the cars grills and gills to keep it new and updated i know of one car that was updated 4 times.
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Old 11-28-2010, 07:13 PM   #17
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I don't think that convertibles were chosen because of stiffness of the frame/body. Anyone who's ever driven both 68-75 coupes and convertibles, knows that the coupe is a much more rigid design. Even with the extra bracing in the cowl, the convertibles have LOTS of cowl shake, which the coupes don't.

The ease of installing a roll cage probably had little, or nothing, to do with the choice of body style either. If you look at pictures of Corvettes racing in the 60's and 70's, none of them had roll cages, just a single roll bar and forward brace. Few road racing series required cages before the late 70's. Up till then, the only road racers using cages were unibody cars, such as Trans-Am Camaros, Mustangs, etc.; and this was done to strengthen the unibody, not for safety. Sure, it is easier to put a roll bar in a convert., but just how much harder is it to put a single bar in a t-top?

I think the reason so many racers chose the convertible body was weight and aerodynamics.

The convertible body should definitely be lighter than a coupe. Without a softtop frame or the extra steel found in the coupe's birdcage, the convertible would likely be lighter. Even with a hardtop installed, the convert was probably lighter than a coupe, and would be stronger than a convert, without one.

From an aero stand point, I think the convert would be better with or without, a hardtop. In endurance racing, most Corvettes ran a full windshield, and a hardtop. I think the fastback rear window of the hardtop, would be better aerodynamically than the coupes tunnel window. The hardtop's rear window would allow a smoother flow of air over the top, and to the rear spoiler.

Until the late 70's, SCCA club racing allowed convertibles to race with a cut down windscreen, instead of a full windshield. The smaller frontal area of a convertible, with a cut down windscreen, is far more aerodynamic than a coupe's full windshield. Coupes were required to race with a full windshield, putting them at a disadvantage. Around 1980, the SCCA changed this, requiring all new cars that were being built to run a stock windshield. Older converts, with cut down windshields, were "grandfathered", allowing them to keep their smaller windscreens. A coupe might have been more equal aerodynamically, with the rear window removed, but the sanctioning bodies required it to be inplace.

It's true that convertibles were much more readily available in early 68, but this was only the case for a few months. Certainly it's true that race cars get rebodied. I know of 65's that got rebodied as 78s, and later 84's. We rebodied the Trans-Am series Camaro I crewed on in the 80's, twice in 3 years. Still, this doesn't mean that all Corvette racecars started out as early 68's, that were continuely rebodied. Every year new race cars are built, and every year others are rebodied.

Before we built the Camaro in 84 (which was a tube frame, fiberglass bodied, "silhouet" racer), we built a Corvette for GT-1 racing. This was in 1980, we built it from a 77 Corvette, but chose to body it as an 80. We concidered building a convertible, but as I said earlier, the rules by then required a full windshield on all bodystyles. We felt that a 78-80 coupe with a big, plexiglass rear window; would be lighter and more aerodynamic than a 68-77 coupe body and more rigid and similarly aerodynamic to a convertible with a full winshield.

IMHO, I believe that early on the convertibles were more popular than tunnel window coupes, because they were lighter and more aerodynamic.
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Old 11-28-2010, 10:53 PM   #18
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I would consider those that suggested weight as a probable cause would be close to the truth....a easy 100 ib. immediately with nothing to modify without a soft or hard top....to me weight has always been critical...the lighter they are the easier to move .....My motto was if you threw it up in the air and came down its too heavy. Even paint if applied too heavy adds a considerable amount of weight. but a 100% load of Nitro fixes any weight problem
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Old 11-28-2010, 11:51 PM   #19
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It`s not only what the cars weighted (the SCCA had a minimum weight) but where that weight was placed, up high like in a roof is bad, run a Convertible and the weight could (if you were underweight) be placed low which is good, ever lift a windshield? another reason to run a convert...a cut down windscreen weights nothing.....When the Owens-Corning team built my car in 1970 it was built from a recovered theft Tony Delorenzo bought from Don Yenko the first C-3 the O-C team built was assembled from parts they got (through connections) off the line at GM, their second C-3 was born an L-88, remember many racers built their cars from parts, wrecks or theft recoveries ...Guldstrand always raced a roadster, why? because the weight could be placed low for better handling..you all might want to check out the Corvette race car registry...just type it into your browser.

my car as raced in 1971-1972, paint by GM styling engineer and O-C team member Randy Wittene.
Click the image to open in full size.
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Old 11-29-2010, 10:21 AM   #20
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in 68 the convertibles to coupes sales was 2 to 1. I think the 68 coupe was a delayed production? so most 68's are convertibles.. and about 42% 69's were convertibles..

plus the arguments above would conclude that more 'early' C3s were convertibles.

once you hit 1970 the car was evolving into a luxury sports car and raced less..

interesting thread....
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Old 11-29-2010, 10:21 AM
 
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