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Old 09-20-2011, 08:14 PM   #91 (permalink)
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Originally Posted by euromodder View Post
That could also be done a lot tighter today, if need be with actively controlled skirts.
The potential aero-improvements are huge.
I'd like to subscribe to that too, but the results skirts give are always such a disappointment; and then you have vehicles that attain very low Cd w/o them too.

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Old 09-21-2011, 12:00 AM   #92 (permalink)
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I've been checking out your other images, I really like this rear view.

Tatra rear
Tatra rear | Flickr - Photo Sharing!
Thanks! I've been kind of on and off working on that. It's supposed to be a BEV luxury sedan with removable batteries to easily "fill up" at a gas station. I'll post some pics of the 1:64 scale model I made.

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Originally Posted by euromodder View Post
There's a lot of very minor things that could easily be done today on the basic Saab design to make it even better streamlined.

But it simply ain't happening on today's production lines.


That could also be done a lot tighter today, if need be with actively controlled skirts.
The potential aero-improvements are huge.


Double the average speed of the NEDC to a more realistic 65kph / 40mph, and the 1930s aero solutions will pop up again.
I wish they'd reproduce old designs- not retro distillation, but actually remaking old classics. The biggest problem is probably either that the tooling no longer exists or that they'd have to redesign everything BUT the body to comply to modern vehicle laws.

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I like the look of those early Saabs too. Here's one for you Sven7:

It recently set a record at 145+mph with a 1 liter motor.
That's the coolest 93 I've ever seen! Thank you for that!

The other one looks like they have been studying Jaray's Tatras VERY closely haha.

ALSO! Update. I bought some huge foam core pieces today (like 40" long- fit easily in the Probe) but will still need to double them up to cut out the 67" profile of the car. Hopefully I'll be able to get that done tomorrow night. It's already midnight (!) and I've got some financial aid stuff to take care of

Also finished a sweet dry point print of a Voisin Laboratoire. I'll post it in a few weeks when i get it back from the prof
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Old 09-22-2011, 04:53 AM   #93 (permalink)
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Quote:
Originally Posted by Frank Lee View Post
I'd like to subscribe to that too, but the results skirts give are always such a disappointment; and then you have vehicles that attain very low Cd w/o them too.
Why do you call the results disappointing ?
Most of the very high-milers (in absolute terms, not % over EPA) on EM, at least have rear-wheel skirts.
Once upon a time they were highly fashionable on cars.

Front wheel skirts are not that easy as DIY-items, and home-made installations usually aren't that clean and add to the frontal area.


Surely some cars have low Cd without skirts, but they still hover around the 0.25 mark where aero progress has stopped for production cars (see Hucho).

If manufacturers want to go below that, it'll have to take more aero measures, and even smaller improvements will have to be accepted.

But when they look at the market, they see their customers still wanting to buy huge tanks instead of cars ...
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Old 09-22-2011, 11:51 AM   #94 (permalink)
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It seems to me that the front skirts are of "minimal" benefit, probably as the air has not fully reattached to the side of the car, after getting bunched up on the grill area. If the car has the "template" pattern, looking down from above, then the air would be smoothly attached, and enclosed front wheels would be "worth" pursuing. You can see many of the aero cars of today have the rocker panel areas pinched in somewhat, between the front and rear wheel wells, and roof indentations, this is where the airflow "wants to go" after coming around a corner. This was very evident while doing cylinder-head flow bench research. If the air "wants" to go there, give it a space, if it doesn't want to be there fill in the space. Decreasing the turbulence results in smoother airflow and less drag.
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Old 09-22-2011, 12:11 PM   #95 (permalink)
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CFECO, do you have any proof of that? My tuft test shows attached airlflow all the way to the edge of the wheel well, and you know the Probe is FAR from the template in plan view.



The rockers are pinched in because

1. It looks good and stylists like it.

2. The side windows need to maintain their radius as they roll down into the door, curving in as they go down. The more tumblehome in the window, the more pinched the door. This gives the stylists more opportunity to sculpt the bodyside (see #1)

Many old English cars have straight sided doors. For example the Jaguar XK120, often regarded as one of the most beautiful cars ever produced, is in my opinion let down by its dumpy bodysides. Compare that to a Lotus Elise/Exige and you'll see the difference. The latter has a nice "wasp waist" in both profile and plan, while the Jag only has it in profile.
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Old 09-22-2011, 12:30 PM   #96 (permalink)
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Remember that the top of the wheel is moving forward at 2X the speed of the car, relative to the ground. Even with the partial skirts on the Probe, the one tuft looks like it is getting "sucked in" to the churning air flow around the wheel; even with smooth wheel covers.

I think if cars are going to have any chance of achieving a Cd >0.2 I think they need to have wheel skirts. This is definitely "worth" going after, in my opinion.
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Old 09-22-2011, 01:51 PM   #97 (permalink)
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Proof, in hand right now ..no. If we had a wind tunnel to play with, many of these questions could be pursued. WE, have disturbed a large volume of air with the car, more air than just at the surface. All this disturbed air, took power to disturb it You could have "attached" flow, with high pressure keeping it attached, at the cost of drag, like on the fender flares here. Being that the body is not flat along the sides, there is a lot of work to get the tires flush.
I wonder how the Probe would be with a template front?
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Old 09-22-2011, 03:05 PM   #98 (permalink)
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Quote:
Originally Posted by euromodder View Post
Why do you call the results disappointing ?
Most of the very high-milers (in absolute terms, not % over EPA) on EM, at least have rear-wheel skirts.
Once upon a time they were highly fashionable on cars.

Front wheel skirts are not that easy as DIY-items, and home-made installations usually aren't that clean and add to the frontal area.


Surely some cars have low Cd without skirts, but they still hover around the 0.25 mark where aero progress has stopped for production cars (see Hucho).

If manufacturers want to go below that, it'll have to take more aero measures, and even smaller improvements will have to be accepted.

But when they look at the market, they see their customers still wanting to buy huge tanks instead of cars ...
A couple of percent is not even detectable without highly accurate instrumentation. I know; I've tried it.

Loremo is but one example of a low Cd skirtless design and at .20 it's well below .25.
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Old 09-22-2011, 04:01 PM   #99 (permalink)
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Quote:
Originally Posted by NeilBlanchard View Post
Remember that the top of the wheel is moving forward at 2X the speed of the car, relative to the ground. Even with the partial skirts on the Probe, the one tuft looks like it is getting "sucked in" to the churning air flow around the wheel; even with smooth wheel covers.

I think if cars are going to have any chance of achieving a Cd >0.2 I think they need to have wheel skirts. This is definitely "worth" going after, in my opinion.

Then again, here's a rebodied Lotus with no skirts at all that managed Cd 0.2 and 135 mpg (hmmm...Imperial?)
File:Opel ECO Speedster with 1.3 CDTI-worldrecord-Diesel.jpg - Wikipedia, the free encyclopedia
I'm showing the "honest" version without the show wheels.
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Old 09-22-2011, 06:44 PM   #100 (permalink)
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Quote:
Originally Posted by CFECO View Post
Proof, in hand right now ..no. If we had a wind tunnel to play with, many of these questions could be pursued. WE, have disturbed a large volume of air with the car, more air than just at the surface. All this disturbed air, took power to disturb it You could have "attached" flow, with high pressure keeping it attached, at the cost of drag, like on the fender flares here. Being that the body is not flat along the sides, there is a lot of work to get the tires flush.
I wonder how the Probe would be with a template front?
I figured as such. But being pressured to the surface or not, it's still "attached". The air is not tumbling aimlessly around the corner.

I'll try to get a template front on the Vogn although it will be too long and narrow to simply follow all the way back. Hoping to cut out the profile tonight. I came down with a sore throat and hope it's not a budding cold

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