Tribute to Syd Mead or F-117 aerodynamics?

[freebeard]

Perhaps the issue is cognito ergo sum. Or some derivative. We called it the 57 chevy rule way back in college where you "SEE" things that reinforce your beliefs, truth be damned.

I like 'the eye cannot see what the mind does not know', but the modern rendition (per Scott Adams) is 'two movies on one screen'.

I don't think anybody has had the time or compute power to generate hard dimensional data based on the reveal pictures.

I think it's possible with 3D from 2D software. There exist enough pictures from enough angle to reproduce the shape. It's the CFD that's compute intensive.

edit:
This one has the side windows modeled:

https://www.youtube.com/watch?v=6fuLD0R1iEU

TLDR: he fudges the 0.38 result down to 0.30.

2nd edit:
Offtopic for the thread, but The FUV Has Arrived! Arcimoto | In Depth has M. Frohnmayer commenting on the implications of the 'origami' construction technique. Panel vans and etc. at 0 additional cost.

[kach22i]

Originally Posted by Vman455

Keep in mind, this article was written in 2009--three years before the first air curtains appeared on a production car.

I had not noticed the date of the article. Now it has me puzzled why a Ford aerodynamicists would be inadvertently praising GM's Art & Science design path. I cannot think of a single Ford from that era that took a similar path and that includes the Fairlane concept or production Flex.

2010
Cadillac resurrecting Art & Science ad campaign
https://www.autoblog.com/2010/03/24/...e-ad-campaign/

When the first-generation Cadillac CTS went on sale in 2003, the brand-revitalizing sedan incorporated a new design language that General Motors called "Art & Science." The idea behind the new design language was to ""incorporates sharp, sheer forms and crisp edges - a form vocabulary that expresses bold, high-technology design and invokes the technology used to design it." The design came with its own marketing campaign too, which brought many new customers to the Cadillac brand.

This design path is still evident in the current generation of Opel derived Cadillac's.

[kach22i]

Originally Posted by Hersbird

I don't understand (apart from just Tesla fan clubbing) why this article gets so much play and the detailed in depth analysis with detailed specifics and exact results I posted a link to gets zero play.

I found your post (see below), it was in another thread, in another part of the forum. I had not seen this other thread before now.

Fossil Fuel Free
https://ecomodder.com/forum/showthre...k-37999-8.html

Originally Posted by Hersbird

https://www.linkedin.com/pulse/tesla...uter-remmerie/

.48 and still without mirrors. I also think those wheel flairs look smaller on the model than the ones on the prototype.

Good link, same link.

Tesla Cybertruck - Is it more streamlined than it looks?
https://www.linkedin.com/pulse/tesla...uter-remmerie/

[Hersbird]

Originally Posted by kach22i

I found your post (see below), it was in another thread, in another part of the forum. I had not seen this other thread before now.

Fossil Fuel Free
https://ecomodder.com/forum/showthre...k-37999-8.html


Good link, same link.

Tesla Cybertruck - Is it more streamlined than it looks?
https://www.linkedin.com/pulse/tesla...uter-remmerie/

I also posted in post #43 on this thread.

[Vman455]

Originally Posted by Piotrsko

Perhaps the issue is cognito ergo sum. Or some derivative. We called it the 57 chevy rule way back in college where you "SEE" things that reinforce your beliefs, truth be damned.

"Cogito ergo sum" (I think, therefore I am) is a statement of self-awareness arising from conscious thought--not the same phenomenon as what you're trying to describe, I think, which is something more like confirmation bias? And yes, I agree there's a lot of that going around with estimates just in this thread ranging from 0.25 to 0.48. We'll have to wait and see if Tesla releases a number.

[ldjessee00]

I am not sure of the validity or accuracy of this person's model, but I thought it relevant to the conversation here.

https://www.youtube.com/watch?v=6fuLD0R1iEU

[ldjessee00]

Not sure I saw someone compare the Cybertruck to the Citroen Karin from the 80s...

Citro?n Karin

[redpoint5]

Originally Posted by ldjessee00

I am not sure of the validity or accuracy of this person's model, but I thought it relevant to the conversation here.

That guy claims the truck has something like a .41 Cd at 60 MPH, and somehow it drops to .3 at 88 MPH. How does Cd change with speed? I thought it was a constant value.

[Hersbird]

Originally Posted by ldjessee00

I am not sure of the validity or accuracy of this person's model, but I thought it relevant to the conversation here.

His .40 seems reasonable but he posted a 2nd video with some comparisons. The problem is his scale on the Ram and the Ford is silly small, it's like he modeled a toy car and is running that without changing the dimensions. Doesn't a smaller, shorter car make it more difficult for air to reattach? By making the Ram and Ford toy sized wouldn't that give them disproportionately high Cd numbers in the comparison? It's just more bias. We know what the Ram can get and it's .36 Cd.

https://youtu.be/7741YdnAcR4

[Vman455]

Originally Posted by redpoint5

That guy claims the truck has something like a .41 Cd at 60 MPH, and somehow it drops to .3 at 88 MPH. How does Cd change with speed? I thought it was a constant value.

Drag coefficient does vary with the inverse square of speed*, but because of that inverse square relationship it's so small as to effectively be constant over the speeds a passenger car sees.

Last night Musk tweeted:

With extreme effort, Cybertruck might hit a 0.30 drag coefficient, which would be insane for a truck. Requires tweaking many small details.

Sounds like it's above 0.30 now but could reach that for production.

---

*This is a bit of a simplification--it assumes supercritical Reynolds number (as the flow field transitions from laminar to turbulent over a car, Cd decreases suddenly, but this happens at a low speed). A car going 60 mph vs. 88 mph: there should be no change in Cd.