Sagebrush posted:

you can make squarish/angular cars that still have good aerodynamics. the lowest drag shape is a wide flat plane, after all.

cars these days are all round and bulgy and bloated because that's the shape of their drivers.

animist posted:

Sagebrush posted:

you can make squarish/angular cars that still have good aerodynamics. the lowest drag shape is a wide flat plane, after all.

cars these days are all round and bulgy and bloated because that's the shape of their drivers.

Broken Machine posted:

when the prius was released, it had one of the lowest coefficients of drag ever seen in a production vehicle. that's a major reason why they shaped it like that, it was inspired by dolphins or something. still ugly, but they did design it for good aerodynamics

Ornamental Dingbat posted:

I love how Chevy was teasing the Volt as a rad-rear end batman looking electric car for like a decade then they released it and it was just a Detroit Prius.

Broken Machine posted:

when the prius was released, it had one of the lowest coefficients of drag ever seen in a production vehicle. that's a major reason why they shaped it like that, it was inspired by dolphins or something. still ugly, but they did design it for good aerodynamics

haveblue posted:

I was always under the impression boxy cars (and a lot of other features like retractable headlights) died out not because of aerodynamics but because of crashworthiness requirements

rotor posted:

the second one is like 5000 times better

rotor posted:

Kenny Logins posted:

https://twitter.com/slate_akita/status/1458822858122088452?s=21

Sagebrush posted:

kammback designs are all about compromise, though. you need to have things like "a trunk" and "four seats" and "cabin volume" and "doors" so you settle for this rounded wedge with an implied elongated tail that decreases wake vortex generation. it's hardly efficient though. still a big lump pushing its way through the air.

me, commuting to work like a boss:

echinopsis posted:

in what way is the design of a porsche 911 copyrighted or patented?

mobby_6kl posted:

Isn't a water drop the best shape? Which is why the Aptera seems to work so well at least on paper



A smaller frontal area is better too obviously but there's only so much you can do while fitting two people comfortably

Jonny 290 posted:

you can buy every replacement panel aftermarket so you can "build a 911", but if you try to sell a modernized 911 copy named Emergency Number or something, thirteen bored lawyers will immediately show up at your doorstep and bury you in six feet of lawsuit summons paperwork.

Ellie Trashcakes posted:

Design patents and trade dress, mostly. Copyright does not apply to a "useful article," which in addition to free advertising forms a compelling motivation for prominent, trademarked elements for clothing and accessories. All that ugly horseshit on a vuitton bag? Trademarked. As long as your knock-off purse doesn't have that ugly poo poo on them (or embellishments considered trade dress) you're good to go

Sagebrush posted:

Fun story about that.

A water drop was believed for a long time to be the most aerodynamic shape because it seemed logically correct that a fluid would deform itself to the lowest-energy shape. Make cars shaped like teardrops!

However, it turns out that what people think water drops look like, with a round base and elongated tail, is only what they look like when they're dripping from an edge, still attached, and about to fall. In the air, surface tension pulls them into a sphere and drag deforms them into a sort of flattened jellyfish shape:



This isn't particularly sleek or aerodynamic; it just balances drag and surface tension.

Of course a flat plate turned edge-on to the airstream produces the least drag, like a katana slicing through a flat of Kirkwood Signature spring water. However, that isn't practical for a car or any other object where you need to enclose some sort of volume. Bulging the top (and optionally the bottom) outwards will give you some useful volume, and extending the trailing edge way out at a shallow angle decreases the energy lost to vortex formation. The classic teardrop shape with a round nose and long tail is, coincidentally, a reasonable application of these rules. But there is no need for the nose to be blunt. High speed airfoils have very sharp leading edges, missiles have ogival nose cones, etc. And the longer and pointier you make the nose, the less energy is lost in turning the air around the shape, and therefore the lower the drag.

You can see exactly when people realized this by looking at solar cars. For many years all the leading designs were shaped like teardrops, like the Sunraycer:



Then someone went "wait a minute, this doesn't make sense" and now all the best solar cars are flat plates with sharp nose and tail and a tiny little bubble for the driver's head.



This can't be directly applied to passenger cars because you need to have a cabin bigger than the driver's head, and thus will have greater frontal area. You don't want to extend the front of your car out the extra 8 feet that would be needed to get a sharp point while having a reasonable cabin and windshield height. Pedestrian safety regulations also no longer allow sharp front ends like on, say, a Lamborghini Countach. So we have to accept a blunter nose. Historically, there have been cars that extended the nose smoothly forwards for aerodynamics; those old dustbuster minivans had a drag coefficient of just 0.30, compared to the Prius' 0.26, which is pretty dang good. (average pickup truck is ~0.60, a cube is 0.8)



On the other end, in the 1930s Wunibald Kamm discovered that you don't have to actually elongate the trailing edge of your shape all the way to a point to have good vortex handling. You can get like 90% of the effect by just starting the trend and then chopping the end of the shape off flat -- due to inertia and viscosity, the air will continue as if the tail of the car were still there, more or less. This is now called a Kamm-back and a lot of cars use it. It's very distinctive on the first-generation Honda Insight:


(Cd of 0.25, for the record. gently caress you Toyota)

The dustbuster minivan probably would have knocked a few more points off its Cd, bringing it within spitting distance of the Prius, if its roof tapered into a Kammback. Remember, though, that a Kammback is still not quite as efficient as bringing the tail to a point; if it were, airfoils would probably have that shape. But it's nearly as good aerodynamically while not making the car absurdly long.



And that is why the most aerodynamic mass-produced cars today have a blunt wedge-shaped front, a tapering roofline, and a flat rear end. The Aptera is just a little better because, as you can see, it has a longer wedge in the front and it pulls the tail all the way out. As you note, that's about as good as you can get while still making space inside. But any resemblance to a teardrop is coincidental

Sagebrush posted:

echinopsis posted:

what I mean is that, does this rely on some kind of subjective notion that the rip-off looks like a 911?

or to extend what I am wondering, is how far away would you need to shape a car from a 911 before some subjective measurement determines it’s different enough that it doesn’t risk a problem

Sagebrush posted:

you can file a design registration on a specific shape, ornament, arrangement of elements, etc. and prevent other people from selling that same design directly. it fits somewhere between a copyright and a patent; a porsche 911 isn't copyrightable as a creative work, nor can something like "two round headlights and a long tail" be patented, but the total combination of elements can be distinctive enough to be registered as a unique design. you might get a design registration on your particular tubular steel and leather chair, or your brightly colored plastic vacuum cleaner, or whatever. (extra credit: who am i referring to with these two examples?)

like ellie says, this applies only to purely aesthetic elements, not functional components, so you can't say oh i put two buckles on the side of my purse, that's my design, you can't make a purse with two buckles any more. it's only the specific aesthetic way that the parts are used to make the look -- the exact positioning of those two buckles relative to other elements, in a way that is positively aesthetic and not merely functional -- that can be registered. and like patents, you can't register something that is substantially similar to prior work or incredibly obvious. like many things in intellectual property law, it sometimes comes down to "what would the average person off the street think?"

of course, even if you are sure you're legally justified in selling your knockoffs, none of this will stop porsche from simply sending you a c&d and threatening to bankrupt you in court.

and then there's the whole situation where you might be violating trade dress, like how Fluke has a trademark on yellow multimeters, or if you say that your transmission is "just like a porsche Tiptronic" that's another kind of trademark infringement, or perhaps you stupidly used their corporate font which is copyrighted, or who knows what secret patents they own that you've inadvertently infringed while building your copies...

Sapozhnik posted:

https://twitter.com/weadhitter/status/1457967813998485504

Sapozhnik posted:

https://twitter.com/weadhitter/status/1457967813998485504

Sagebrush posted:

"what would the average person off the street think?"

of course, even if you are sure you're legally justified in selling your knockoffs, none of this will stop porsche from simply sending you a c&d and threatening to bankrupt you in court.

and then there's the whole situation where you might be violating trade dress, like how Fluke has a trademark on yellow multimeters, or if you say that your transmission is "just like a porsche Tiptronic" that's another kind of trademark infringement, or perhaps you stupidly used their corporate font which is copyrighted, or who knows what secret patents they own that you've inadvertently infringed while building your copies...