Cybertruck is NOT aerodynamically efficient - why the shape?

[mspohr]

Saw this on Twitter, so do not have a link to original FB source...

Great to see the laminar flow over the roof and down the back as well as the high sides improving flow. Could be quite good overall.

 

[$TRONG]

Many surprising facts can come from wind tunnel testing. Who would have thought a dimpled golf ball would fly farther? We will not know until the real data comes in, however, the peaked roof and down sloping aft section does lend well to a clean break in the flow over the back. And the frontal area isn’t as important as the tail that’s a fact. In other words if you’re going to move the air out of the way, you may as well do it right away as opposed to slowly, but when it comes time to put the air back together, doing that gracefully has proven to be of the most benefit overall.
If you look at (normal) airplanes they are always a lot more blunt on the front than they are on the back.

 

[JRP3]

Thanks for the thoughtful reply. The reality is that faceted surfaces are terrible for aerodynamic efficiency. Do you know why the F-117 Nighthawk is faceted? Because, at the time, we couldn't figure out how else to reduce radar profile of more efficient aerodynamic surfaces. The F-117 was (and is) an "unstable" aircraft because of its shape.

But whatever - it's a Tesla . . .

So now that your premise has been proven wrong will you admit it? And request a change to the thread title to reflect reality?

 

[nativewolf]

This is actually incorrect. there are only hard angles on this as that's a limitation to keep the 30x cold rolled Stainless Steel from becoming cost prohibitive and this combined with as someone else has pointed out is the optimal aero shape ( Streamlined body/half body) approximated with a flat faceted surface is a compromise of aero efficiency for weight/durability. The F-117 is unstable has it has to manage that on many planes not flat on the ground like a truck.

Reading this thread and it was the second page to see someone comment correctly that it is a function of the materials. The design is amazing partly because of the materials, no forming or pressing this stainless. Also, no paint shop (huge huge cost savings).

 

[Yinn]

The Motortrend report sheds some light on this:
" Tesla might have erased the problem with active suction to bend the boundary-layer downward just aft of that peak. Gordon Murray's McLaren F1 used this trick, and SpaceX has plenty of expertise in active measures to manipulate airflow around its re-entering Falcon 9 first stages. However, with the bed cover deployed, the angle of its vast descending surface is evidently shallow enough for the flow to naturally reattach. The benefit being that it harvests a useful fraction of the air pressure that blocky, open-bed trucks almost entirely forfeit. Actually, the tougher aerodynamic trick has been coaxing the temperamental flow around those sharp A-pillars."

Wait. Does this mean that potentially, Tesla could control the bed cover electronically to act as a spoiler to create/remove downforce?

"Officer, I swear I secured the load. The cover just opened on it's own."

 

[nativewolf]

I think you're being a bit too exact with my video.

1) even in the video the separation is minimal compared to similarly sized conventional pickups

2) my video is not a complete 3 dimensional analysis of the truck it's a polygon in the rough profile shape I drew up and uploaded to a modelling web app ( as well the underside is completely imagines as we have no pictures of that) you can even see the white triangles outside the profile interacting with the flow so this may show a more negative flow than reality

3) As I mentioned before this may be offset by the overall lower drag coefficient of a bare stainless steel vs painted surface as there is an improvement there

In any event the primary design decision here wasn't around aerodynamics although it was ( and is always ) PART of the consideration it was around limitations of the material

Seems to me that the design is very well thought out. Now can they get the govt to approve camera's instead of mirrors. One would hope so because mirrors are just not useful in today's world. Where is the bumper? What will actual lights look like? Lots of small stuff but the truck has a very very interesting design and it shows enourrmass innovation. I still wished it did not look as ugly ; but I will buy one. My first tesla..I am very excited.

Stainless to get to the strength needed to tow my 14k lb trailer, a worthwhile sacrifice. 500 mile range...awesome. I really don't care how fast it is..in fact slow mine down because I can't afford the tickets.

 

[SmartElectric]

The Model S is insanely aerodynamic and also looks amazing. Is it too much to ask for something that looks amazing and performs well? I thought that was kind of Tesla's whole thing but now I see that they're almost entirely abandoning the virtues they previously held important.

Tesla Model S was not as cost optimized as CYBRTRK.
The point of the S was to be the best premium sedan available for any price, and the specs and sales back that up.

The point of CYBRTRK is clearly far more optimized for price/spec/performance, frankly, I am considering the truck on price and specs alone, as "looks" can be subjective, but for me, any truck is worse than any sports sedan in those terms, so if I am willing to compromise on looks, I can get a lot of vehicle for far less than a Model S.

As for aero, your point has been made, Tesla did not overtly design the truck for aero, now that you've made your point a few dozen times, perhaps also appreciate that Tesla optimized for price/performance where part of the price element is driven by manufacturing optimization like the no paint shop ($200M saved), reduced stamping ($50M+ saved) and the like.

 

[Doc Brown]

So now that your premise has been proven wrong will you admit it? And request a change to the thread title to reflect reality?

You should find something more productive to do . . . Perhaps when the Cybertruck specs are posted you can be in a position to run your mouth. Right now - I'm not so sure.

 

[Doc Brown]

So now that your premise has been proven wrong will you admit it? And request a change to the thread title to reflect reality?

In wake of Tesla Cybertruck, what are your priorities in an electric pickup?

 

[jerry33]

You should find something more productive to do . . . Perhaps when the Cybertruck specs are posted you can be in a position to run your mouth. Right now - I'm not so sure.

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I don't believe anyone said it would beat the S or X in aerodynamics, just that it was actually pretty good and phenomenal for a truck.

 

[Mark Z]

Aerodynamics of the Cybertruck need to be compared with all other similarly sized trucks on the market.

For those overly concerned about wasting energy, attempt to use a more aerodynamically designed EV each time you haul stuff.

Take into consideration the phantom/maintenance loss of energy by not using an additional EV if you have more than one. My 2012 MS P85 would use about 80 kWh a month when left plugged in and unused. Perhaps newer models are more efficient when left garaged.

 

[jerry33]

Aerodynamics of the Cybertruck need to be compared with all other similarly sized trucks on the market.

For those overly concerned about wasting energy, attempt to use a more aerodynamically designed EV each time you haul stuff.

Take into consideration the phantom/maintenance loss of energy by not using an additional EV if you have more than one. My 2012 MS P85 would use about 80 kWh a month when left plugged in and unused. Perhaps newer models are more efficient when left garaged.

That would be about right for unplugged, but plugged in, mine (2013 85) charges back up to the set point every other day.

 

[Mark Z]

That would be about right for unplugged, but plugged in, mine (2013 85) charges back up to the set point every other day.

Using the ChargePoint Home EVSE, they send a monthly report of usage. The 2012 MS P85 was charging daily as needed for that approximate 80 kWh per month. Some months were higher if doors were opened or tires filled with air, but I was only including the months of complete non-use.

 

[jerry33]

Using the ChargePoint Home EVSE, they send a monthly report of usage. The 2012 MS P85 was charging daily as needed for that approximate 80 kWh per month. Some months were higher, but I was only viewing the months of complete non-use.

Ah, I thought you meant that it lost 80 kWh in a month and was almost empty. Using 80 kWh in a month sounds about right.

 

[CMoZ]

@Doc Brown

What exactly is your complete position/question at this point

Based on the discussions here and the press so far it seems like your original question is flawed/wrong

"Cybertruck is NOT aerodynamically efficient - why the shape?"

Point 1
"Cybertruck is NOT aerodynamically efficient" the phrasing here is inexact as aerodynamic efficiency is a gradient so saying it's "not aerodynamically efficient" is hyperbolic as it's some degree of aerodynamically efficient and it's not clear exactly where your line for NOT/IS exists on this spectrum

Point 2
"Why the shape" - This has been written about numerous times in the press and in direct tweets and even within the announcement. It's primarily for the following reasons in order

• The Cold Rolled Stainless cannot be stamped to shape complex curves. It has to be scored and bent at sharp angles
• The Eco-Frame requires specific overall shapes ( the peaked triangle shape ) to maintain strength required for towing and hauling without a separate frame
• Within the bounds of the above 2 constraints make the shape as aerodynamic as POSSIBLE.

There are probably other contributing reasons as well that we don't know about but you can't design for aerodynamic efficiency to the detriment of everything else none of these factors exist in a vacuum they have to all be considered together and decisions about where tradeoffs are made between them can get very complex

 

[JRP3]

You should find something more productive to do . . . Perhaps when the Cybertruck specs are posted you can be in a position to run your mouth. Right now - I'm not so sure.

So now that you've been proven wrong your response is to act like a fool and bury yourself further.

 

[RobDickinson]

Saw this on Twitter, so do not have a link to original FB source...

Justin Martin

 

[Tes*la*rosa]

Are the boxy Tesla Cybertruck's aerodynamics any good? An engineer found out - Electrek

Turns out, the aerodynamics are better than I expected.

 

[Revelation]

Thanks for the thoughtful reply. The reality is that faceted surfaces are terrible for aerodynamic efficiency. Do you know why the F-117 Nighthawk is faceted? Because, at the time, we couldn't figure out how else to reduce radar profile of more efficient aerodynamic surfaces. The F-117 was (and is) an "unstable" aircraft because of its shape.

But whatever - it's a Tesla . . .

Well you are only partially correct. The flat surfaces and sharp angles are specifically designed to minimize radar signature, the Nighthawk itself is one big wing as the underbelly acts as a surface. It's unstable due to the design but that was solved a long time ago with fly-by-wire computers. The F-117 is still an aerodynamic aircraft.

In fact the F-16 and F-18 are both aerodynamic aircraft yet are extremely unstable due to their designs to ensure maximum maneuverability. Aerodynamics are not tied to aircraft stability. The B-2 is very aerodynamic but it also requires a computer to ensure the aircraft maintains stable flight.

 

[RobStark]

So what is the estimated Cd?

I think FCA's Ram 1500 is the best for a production full sized truck at .354