Want low drag? Don't follow a template.

[Cd]

From what little I understand of the template, sure using it on any and all car shapes will not not be perfect, but isn't it a good way to get 75% the way there ?
You will have areas that need twerking, but for the most part, it can show the angle that the air MOST LIKELY flows from the back of a vehicle, correct ?

I see more and more examples everyday of vehicles that have low drag, despite dropping way, way off the curve of the template.

To me, this does not make the template wrong, but meerly means besides the template curve, air can flow in other directions as well and still remain attached.

Julian, so are you saying that the template has been presented as showing the ONLY way that air needs to flow to equal low drag ?

[JulianEdgar]

Originally Posted by Cd

From what little I understand of the template, sure using it on any and all car shapes will not not be perfect, but isn't it a good way to get 75% the way there ?
You will have areas that need twerking, but for the most part, it can show the angle that the air MOST LIKELY flows from the back of a vehicle, correct ?

I see more and more examples everyday of vehicles that have low drag, despite dropping way, way off the curve of the template.

To me, this does not make the template wrong, but meerly means besides the template curve, air can flow in other directions as well and still remain attached.

Julian, so are you saying that the template has been presented as showing the ONLY way that air needs to flow to equal low drag ?

No, I am saying that the ways in which the template have been used here are wrong. Those ways are:

- Show where there is separated and attached flow on existing cars
- Guide the shape of rear extensions
- Show how rear spoilers on sedans should be positioned and shaped
- Allow the assessment of the ‘aerodynamic purity’ of cars

The template is simply one of at least five different low drag shapes. No more and no less that that.

[freebeard]

Now, does any current aerodynamic textbook cite a theory of the template and discuss it in detail? No, they sure don't.

IMHO it's down to use case. The only area where Templatey McTemplate has application is in solar racers, and they deviate toward a longer fineness ratioi,

I haven't posted this one in a while:

...at least five different low drag shapes

Whoa! [citation needed]

[JulianEdgar]

Originally Posted by freebeard

Whoa! [citation needed]

It's in my video at 9:10:

https://www.youtube.com/watch?v=hxmbQhcNWy8

.... and I've previously posted the diagram here and referenced it.

[JulianEdgar]

Originally Posted by freebeard

IMHO it's down to use case. The only area where Templatey McTemplate has application is in solar racers, and they deviate toward a longer fineness ratioi,]

As far as I know, the number 1 reference on solar car aerodynamic design (The Leading Edge - Tamai) makes no reference to any template-style shape. Not surprising when most solar race cars are well below the drag numbers of the template.

[Cd]

Originally Posted by JulianEdgar

It's in my video at 9:10:

.... and I've previously posted the diagram here and referenced it.

Fascinating !
Just curious where you posted the diagram here that you show in the video, and if it shows other angles.
There really is quite a large variance for so little variation in Cd.
This is why I'm curious about other angles.

[freebeard]

Ah, yes. AVA similar to the Schlorwagen? All the others are from VW. Confirms my suspicion that the VW Beetle from the beltline up from the A- to C-pillar is optimized for a flat windshield within the driver's reach.

This does show the weakness of any template limited to plan and elevation. Compare the Mercedes-Benz Boxfish or a Porpoise's eyes. Two views don't capture the surface development.

Or Ross Lovegrove:

[JulianEdgar]

Originally Posted by Cd

Fascinating !
Just curious where you posted the diagram here that you show in the video, and if it shows other angles.
There really is quite a large variance for so little variation in Cd.
This is why I'm curious about other angles.

Page 201, Aerodynamics of Road Vehicles, 2nd edition.

The full diagram shows the plan views of each shape as well as the side elevations.

The idea that there is just one optimal shape for low-drag car bodies is ridiculous, and the idea that we should apply bits of angles of one such body to guide our car modifications just quite absurd.

[Cd]

Originally Posted by aerohead

* Gary Eaker would be great to bring onboard. I've planned to write him for a long time now, and hope to complete the Spirit of EcoModder project one day at the A2 wind tunnel.
* A peer-review jury would be awesome!
* I did investigate the HOT ROD Magazine Camaro land speed record car, which I believe Gary Eaker consulted on. The 'Bonneville' rear spoiler on that car happens to match the AST-II perfectly.

I am just now seeing this reply Aerohead.
Please do invite Gary here, since I know i'm not the only one here that would love to see him here - even if just fpr a short one time Q&A session.

If he can take an old 1979 Camaro and get it to .201 just by dropping it, sealing the front, and adding a decklud extension, then he certainly knows what he is taking about.

[JulianEdgar]

Originally Posted by Cd

If he can take an old 1979 Camaro and get it to .201 just by dropping it, sealing the front, and adding a decklid extension, then he certainly knows what he is taking about.

That sounds literally incredible. Can you link to the evidence?