10/23/08 - New comment: 4 hp@60 mph - popularmechanics.com

[n_dawg]

The latest comment (#10) on Popular Mechanic's article on Neil Hannemann (http://www.popularmechanics.com/blogs/automotive_news/4260376.html) is quite interesting:

I visited the aptera headquaters about 2 months ago. They do not give tours to the public. I have deposit on a car so they gave me a personal tour. I knew about Neil Hannemann before the public. After talking to the co owner and touring their facility I can say these guys are playing a very serious game. I sat in the type 1 all electric vehicle. It has electric airconditioning! The team this company has put together and continues to add to is nothing short of amazing! You can move the whole car with your hand it is so light. It takes only 4 hp to move this vehicle 60 mph because of its efficient shape. This car is amazing.

His visit would have been some time later than February, but there's no timestamps on their comments.

[ApteraH@3535]

The date at the top of that Popular Mechanics article is April 22 - probably not the new article -- they don't even have the November cover on their web site yet. That interview was probably in Feb.

[n_dawg]

Oh no, certainly not the new article, but when I was looking for it I stumbled across this.

It's the newest comment on there, so I'd imagine it's later than February. Impossible to say without timestamps though.

[KarenRei]

If that's true, and if we assume the 60mph range is 110mi, and if we assume that this is at 85% pack->inverter->motor efficiency, then the pack DOD is 64%.

Good find, n_dawg!

[johnvall]

You can move the whole car with your hand it is so light. It takes only 4 hp to move this vehicle 60 mph because of its efficient shape. This car is amazing.
I wonder how safe it will be with a cross wind out in the dessert.

[n_dawg]

Shouldn't be too bad – the aerodynamic shape helps with crosswinds too. Some people have had issues with vertical boat-tails, but Aptera features a horizontal one.

[KarenRei]

My take as well, n_dawg.

[Dubito]

The quote that struck me, "I have deposit on a car so they gave me a personal tour."
Hmmm.

[BryanSR]

The quote that struck me, "I have deposit on a car so they gave me a personal tour."
Hmmm.
It also helps that is has a press corps badge & a member of the Pop. Mechanics staff! :happy0025:

[n_dawg]

The comment doesn't say anything about that; this isn't Ben Stewart talking, it's a commenter on his article.

Unless… you're the commenter? :D

[wpatters]

Could someone check my sums. I conclude that the CdoS "effective flat plate" is .25 square meters. That is about half the CdoS of a Cessna 152.

Bill

[n_dawg]

I'm not familiar with the term CdoS. Could you explain?

[KarenRei]

CdoS? Is that another term for CdA?

[n_dawg]

On Wikipedia's list of automobile drag areas and coefficients (http://en.wikipedia.org/wiki/Automobile_drag_coefficient), they estimate the Aptera Typ-1's CdA at 1.70 m².

[OC-LA driver]

Croswinds were mentioned above. From building Estes model rockets years ago I remember one concept: to maximize the tendency to point into the wind, the center of pressure should be as far behind the center of mass as possible.

Center of Mass is the (interior) point around which the object would spin if tumbling in a vacuum.

Center of pressure is, look at the profile of the object from the direction the wind is coming, make a flat cardboard cutout, where can you balance it on the point of a pencil? (Not quite accurate given Aptera's complex shape...the wind might "catch" under the flat boattail more than under the rounded nose...but you get the idea).

If the two points are close together, crosswind pushes car straight to the side; theoretically I think that's close to ideal? In a car perhaps we want center of pressure a bit behind center of mass, so if anything the car turns a little into the wind, not downwind?

If most of the weight's in the front or center and a lot of crosswind pushes harder on the rear wheel skirt, would there be a tendency to "weathervane" into the wind? Especially since only one tire in back to resist sideways air pressure.

I'm no engineer so I defer to those of you with (1) greater expertise and (2) greater desire to hazard a guess about Aptera's characteristics

[wpatters]

:aptera:

Sorry, Us airplane guys must differentiate between parasite drag and induced drag. Since the Aptera really doesn't fly, I didn't have to include that. S is another term for characteristic area.

1.25 square meters sounds a bit high. Of course the form drag of the outriggers (sponsons) might be higher than I expect.

Quoting Cd is just a salesmans ploy. The effective flat plate CdA is much more descriptive of vehicle drag.
Bill

[n_dawg]

I agree. (http://apteraforum.com/showthread.php?t=546)

[basjoos]

You can move the whole car with your hand it is so light. It takes only 4 hp to move this vehicle 60 mph because of its efficient shape. This car is amazing.
I wonder how safe it will be with a cross wind out in the dessert.

Crosswinds haven't been a problem with the horizontal boattail on my car.