anyone have any technical information or opinions on the C3's design in terms of Aerodynamics? Anyway of enhancing the features? Any opinions on the front a nd read spoilers of 80-82 (and 78 pace) and the effects compared to a 74-79.

 

http://forums.corvetteforum.com/zerosearch

http://forums.corvetteforum.com/zerothread?id=531107

 

only slightly better than a bundle of bricks in a wheelbarrow with a parachute.
seriously, in real numbers, the c-3 is terrible. they look all swoopy and stuff but in reality the shape makes for a very turbulent air wake. if you compare the c-3, even the late c-3 which supposedly had the best CD numbers, to a c-4, it's astounding the difference. in the july 2003 issue of corvette magazine, there is an article about the development of the c-4. in the article it states g.m. test showed that to maintain a steady 130mph, the c-3 ('79) needed 143hp, by comparison the '84 corvette needed only 97hp.
unfortunately, the most effective way to get that number down is to buy a newer corvette. i'll probably get flamed for that here on the c-3 forum but that is the reality of it. the amount of body modifications to make a significant reduction in that number would result in a car that didn't really much look like a c-3 any longer. the car can still be improved but you have to decide at what cost.
the real question is why does this concern you so much? i don't mean to offend but unless your doing some racing or speed events, the aero numbers aren't going to affect you greatly. notice the above example was at 130. to maintain 60-70, will not be nearly as significant. aerodynamics is an interesting thing. everything is exponential. up to about 30-40 mph, all cars have roughly similar effects on wind, increasing exponentially with an increase of speed.

 

Clutch, try driving my big ol dodge ram around... I gaurantee you it has worse aero at 40 than your vette has at 80 :lol: :crazy:

(never the less you are correct, fluid dynamics are fun!)

 

i can do worst than that, i drive my friends jeep alot and let me tell you 35" tires make thier own air wake combined witrh humm a big box about of 3 feet off the ground makes for an interesting ride, but it pares nicly w/ my vette. it also makes you feel like you are going about 20mph pluss what you are really going in that car

MAtt

 

The C3 (early C3's in particular) are much like the moderen day Dodge Viper.........Form over Function.

They don't cut through the air with ease but damn do they look mean. :thumbs:

 

The previous posts are pretty much right on. The best way to reduce the cd is to lower the Vette as much as possible. As much drag as the beautiful but functionally imperfect shape of the c3 may have, the air underneath the car is as big or bigger part of the drag. Race cars and modern (expensive) sports cars have smooth bottoms. My Z's bottom is much smoother, trapping less air in voids, etc., compared to my 69. Looking at the 69 and the Z from the front also shows the Z doing a much better job at keeping the air directed away from underneath the car.

Ludvigsen's book star Spangled Sports Car, page 213 states that the 65 Corvette required 155hp to maintain 120mph. The new 68 body needed 210hp! They added side vents and the 120mph requirement dropped to 175hp. With the addition of the spoiler, the car only needed 105hp to maintain 120mph. Imagine cutting the required power in half by such minor changes.

Chuck

 

In comparing the 65 to the 68, it should be noted that the 65's body generated quite a high amount of lift, no? The lift no doubt made it much easier for the car to go 120 mph. :)

-Steve

 

Quote:

only slightly better than a bundle of bricks in a wheelbarrow with a parachute. if you compare the c-3, even the late c-3 which supposedly had the best CD numbers, to a c-4, it's astounding the difference. in the july 2003 issue of corvette magazine, there is an article about the development of the c-4. in the article it states g.m. test showed that to maintain a steady 130mph, the c-3 ('79) needed 143hp, by comparison the '84 corvette needed only 97hp.

unfortunately, the most effective way to get that number down is to buy a newer corvette.

I have to agree and that is the fact of the matter. C5s have a CoD of 0.29 in contrast to the best C3 dialing in at 0.43 which came after they gaudied it up with spoilers, heavy air dams and ground effects. C4s came it at .34!

Quote:

I'll probably get flamed for that here on the c-3 forum but that is the reality of it. the amount of body modifications to make a significant reduction in that number would result in a car that didn't really much look like a c-3 any longer. the car can still be improved but you have to decide at what cost. The real question is why does this concern you so much? i don't mean to offend but unless your doing some racing or speed events, the aero numbers aren't going to affect you greatly. notice the above example was at 130. to maintain 60-70, will not be nearly as significant. aerodynamics is an interesting thing. everything is exponential. up to about 30-40 mph, all cars have roughly similar effects on wind, increasing exponentially with an increase of speed.

Look underneath at a C5 than compare to a C3...it takes a lot to get a C3 flat underneath so the wind doesn't get sucked upward...slowing the hurdling vehicle through the air. It ain't gonna happen. Oil pans dip, exhaust pipes hang, linkage drifts across the frame.

C3 was not engineered to be an aero package. It was Mitchells personal statement that got produced...and a successful one at that. C5 was engineered as an aero package...as C4.

 

:iagree: with everything everyone's said. But when you're driving a C3 at twilight, with the tops off and you've got those big fenders swooping back at you and the pipes are singing a song that would make Andre Bocceli cry there just ain't anything in the world to compare. :yesnod: Some penalties are worth the price. :lol:

 

The simple answer is MORE horses to overcome the design flaw. Marilyn Monroe would never win a long distance race (although it would have been fun to watch) because of the size/shape to power ratio. We can have the best of both worlds because we can take the sexiest car on the planet and put whatever we need under the hood. How fast do you want to go? :cheers:

 

You are in good shape w/ 80 except hood clearance. 78-79 both ft. & rear spoilers.
The Indy pace car ft. spoiler is a great addition for 68-77. Cleans up airflow underneath & sweeps airflow around ft. tires & scoops up air for cooling.

:cool:

Steve (Pacin'California) had a very good pic. in sig. which showed ft. spoiler.

 

Know that is funny....I'm namin' my car Marilyn. :rofl: :rofl: :rofl: :rofl:

 

From what I can see the major problem with the C3 is that the front fender has a trailing edge on it...in other words the air flow hits the front of the fender and then slips down into the depression behind the fender. This causes the air flow at the top of the fender to delaminate and cause an unstable environment. Plus, the air flow behind the fender can not become laminar due to the fender causing a wake.

With this in mind a true fix would be to fill in the area behind the front fenders so that the air can smoothly move along the surface of the body as a single laminar flow. The only thing spoilers do is increase drag and try to keep the body from becoming airborn (with or without the chassis).

 

i think there's really alot more to it than just that. the two most important aspects of any car design are frontal area and trailing edge. undertray is a very close third. despite that sharp pointy nose the frontal area is really quite large on the c-3. you split the air at approximately half way up the main section of the body which, in effect, leaves all that air on the lower half to it's own devices. it gets compressed and churned and everything else you can think of as it goes under the car and around the sides. then there is that nice high pressure zone at the base of the windshield. cowl induction anyone? what air that doesn't go over the top then gets dumped along the sides. this would not be a terrible thing since there is a reasonably low pressure area right past the front wheels as the body tapers back in but then it flairs right back out again and 'humps' up over the rear fenders. for those of you with pre '78 cars, that rear deck is a massive low pressure area that just sucks air in and tumbles it all the way down the rear deck. then the trailing edge. no matter how hard engineers try, they have an extremely difficult time getting air to 're-laminate' as it meets coming off the rear bumper. hence the c-5 and its crisp line at the rear, just like the early c-4, better to break the air cleanly and allow it to figure itself out after the car is gone. those of us with the rear spoilers aren't too much better. think the air actually 'sticks' to the body as it slopes down and then kicks up? guess again. just another pocket of turbulent air. what really happens with the cars with the rear spoilers and the reason they CD better than the previous cars is simply the pocket of relatively stationary air on the rear deck allows the air coming off the back glass to 'skip' over it and go straight off the spoiler. in reality, the best design c-3 rear end was the chrome bumper cars. very similar in design and effect as the c-5, except for the actual bumpers themselves. my guess (purely speculation) is that if you took the '80-'82 front and grafted it onto a '68-'73 rear and threw in a baldwin motion type rear glass or even '78 and up rear glass, that would be the best aero you could get from a true c-3 design. you might possibly break .40, if your wind tunnel meters are out of calibration, that is.

 

The C3 design had a large rear spoiler which was cut down to a lip for prod. 68-73 after aerodynamic tests. Eliminated in 74.

 

A couple of years ago, I ran a "tuft test" with about 50 6" pieces of yarn taped to the body of my 71 vert. Then I drove it a various speeds from 40 to 80 with a friend alongside taking pics.
After all I had read about the C3s poor aero, I expected to see the yarn flying all over the place indicating turbulence. Just the opposite happened - smooth straight yarns pieces behind the front wheels, at the cowl and on the rear deck.
This tells me that, at typical driving speeds, turbulence is not a significant factor. Drag from frontal area has to affect mileage and acceleration from 40 mph or so upards......

 

According to the Corvette Black Book 1953-2003, Page 80, "...Integrated spoilers improved the drag coefficient from .503 to .443 compared to the 1979 models equipped with optional, non-integrated spoilers." Additionally, I'd think the narrow hood 'blister' (?) on the '80-up C3s (similiar to the early C3 small-block hoods) may be the best Cd-hood for a C3. The '80-up front bumper cover, which 'flares-out' to the front wheel lip, has to help; they are similiar to a Winston Cup car set to run at Daytona/Talladega, where aero is EVERYTHING! While I have no data to refute CLUTCHDUST's theory regarding the '68-'73 rear-end styling/Cd, I'd think the '80-up rear most closely resembles the C4/C5 (and NASCAR, NHRA, GT-type racing) styling, which 'breaks-off' crisply & cleanly. If nothing else, the '68-'73 chrome bumpers 'sticking-out-the sides' wouldn't help the aero much, would it? :confused: An interesting thread; but, the HELL with aero in a C3; drop a ZZ502 in it, and be done!!!!! :hurray: :D :thumbs:

 

All I know is that I can break 150 with ~375-420 hp, and overdrive...no sweat....

I think it's as fast I need go....on the ground shiney side up that is....

GENE

 

I really think it is about time to have some tunnel testing done again. The numbers are all over the map, just like the horse power numbers were until the advent of DynoJet dynos popped up everywhere. I don't expect wind tunnels to become as common anytime soon; but, with software taking the place of wind tunnel testing for new designs I would imagine that there is more idle time for the wind tunnels. A magazine could generate quite a bit of interest with such an across the board test. Stock examples of different years plus a few ringers that have lowered their cars and perhaps performed a few other tricks. There is a lot of snake oil in the industry claiming all kinds of cd improvements. It would be great to see how much they really help.

CD numbers are one thing, total frontal area is another. The front area of my ZO6 looks huge sitting next to my 69. The ZO6 is a bigger car. We can argue cd's all day long, but what counts is how much force a given wind speed exerts on a car. The cd of a shoe box is higher than a beach ball, but the beach ball has more wind resistance. I don't doubt that the Z requires less power to attain a given speed; but I want to know what the actual power difference is, rather than the speculation of another "bench racer" like me using some table of estimates to input into the equation.

Chuck