Oldsmobile Aerotech?

[Paolo Castellano]

As many of the people on here already know, the long tail version of this car went almost 290 MPH with similar power to the short tailed version that only went 260's.

I understand this was a super high dollar R&D effort  by Oldsmobile, but does anybody here think the recombination of the air going over and under the car like this would be less drag than just having a flattish Pro Mod rear wing and the diffuser venturi on the back of the car?

Nobody thought much of the front wheel drive stuff before Copeland did it......Has anybody tried to make a car for Bonneville with anything like this tear dropped tail section?

I thought the maximum degree of taper which allows the air to stay relatively attached is 7 degrees. The back end of the Aerotech has more taper than this doesn't it?

[tortoise]

The tails of the streamliners built for the salt in the 50s looked a lot like that. Special construction cars are the only ones which the rules allow such a tail.

[sofadriver]

looks like a dot of drag.
maybe trying to generate downforce under that flat tail?

[John Burk]

The long tail must have let it corner faster on the high banked oval it ran on . The extra surface area increased the drag .

[Paolo Castellano]

The long tail must have let it corner faster on the high banked oval it ran on . The extra surface area increased the drag .

I thought the whole reason the long tail version went faster was because the shape had less drag because the air above and below the car could recombine more efficiently resulting in less drag.......



As the tail gets longer and the angle becomes shallower the air can stay attached resulting in a less turbulent wake which creates less vacuum sucking backwards on the car going through the air?

[sofadriver]

those pics show a streamlined shape where the air can flow around it.
doesn't work when the volume of air allowed to go under the car isn't great enough to fill the void.
if they were really trying for slipperiness they would have applied the same shape as viewed from the top also.

[Paolo Castellano]

those pics show a streamlined shape where the air can flow around it.
doesn't work when the volume of air allowed to go under the car isn't great enough to fill the void.
if they were really trying for slipperiness they would have applied the same shape as viewed from the top also.

That's a great point about comparatively less air going under the car.

The way the Aerotech tail is, would/(should?) still allow the over the top airflow to recombine with whatever airflow coming from the underside?

Then the question is how is the mass airflow with it's (relative to the underside flow)speed over the top combining with the lesser volume airflow from the underside and it's speed to create lift or downforce?

Sorry if I am not using the correct terminology, I am just curious.

I have also questioned why the Aerotech rear body section was not tapered more to a much narrower rear end as well.

Thanks!

[BHR301]

sofadriver, Paolo....you do both know that the Aerotech cars were built on an existing Indy car chassis don't you, the shape of the chassis would limit how much taper could be built into the rear of the body unless you wanted to built a 30 ft. long car. 

Bill

[Paolo Castellano]

sofadriver, Paolo....you do both know that the Aerotech cars were built on an existing Indy car chassis don't you, the shape of the chassis would limit how much taper could be built into the rear of the body unless you wanted to built a 30 ft. long car. 

Bill

Bill, I was aware it was based on a March Indy Car chassis.

My question here was to compare the top speed of the short and long tail cars with similar HP and discuss the effect of the longer tail and to try to relate that to the possibility of some Bonneville car utilizing this concept to decrease drag....

[manta22]

Porsche had a number of versions of its 917. The "long-tail" version was the fastest but not the quickest; it was treacherous at high speed. JWAE found that it was creating lift on the rear end and modified it accordingly. This became the "K" version. It handled much better and lost only a bit of top speed.

Regards, Neil  Tucson, AZ

[Graham]

Bill, I was aware it was based on a March Indy Car chassis.

My question here was to compare the top speed of the short and long tail cars with similar HP and discuss the effect of the longer tail and to try to relate that to the possibility of some Bonneville car utilizing this concept to decrease drag....

UNSW Australia's solar-electric car Sunswift eVe added a "tail" like this for their successful FIA record attempt for fastest electric vehicle over 500km. The car was not designed to set records, but rather as a semi-practical road car primarily built for the 2013 World Solar Challenge rally across Australia. My student Simon Ambrose did the CFD work to design the tail, the original car had a "chopped" back to fit lights and a registration plate and the air had a bit of a downwash component to it leaving the body. Simon's design added about 0.4m to the car but largely eliminated the downwash and reduced the overall drag of the vehicle by about 5%. I've attached a couple of pictures. You can see that in some ways it was a pretty crude addition but it definitely did the job.

We ran a dual-level tunnel under the whole car, otherwise yes indeed we'd have had a whopping amount of downforce - great for a racing car, terrible for a solar car.

[Koncretekid]

Graham,
Undoubtedly the car of the future.  I'm surprised that one of the current manufacturers isn't offering us one like that today, albeit with hybrid or I/C motor.  100 mpg?
Tom