Golf ball structure

[Dilekz]

Hello,

i have read/seen that a golf ball has little punched holes in it.
And that they use it to give the ball less drag.
http://www.golfspice.com/images/golf_ball.jpg

What if you use that structure on all plates on the Aptera type1?

[LQUAN]

It is ok to have dimples on small structure like golf ball, but for large structure it means collecting dirt and harm aerodymic. Good thinking though.

I can't imaging what manufacturing process nightmare it would be to put dimples on a composite car!

Personally, I think it would ruin the smooth looks of Aptera. Cleaning and waxing would be nightmare. :)

[KarenRei]

The dimples on a golf ball create turbulent boundary flow instead of laminar, which takes longer before separating from the sphere, so there's less of a low-pressure wake behind the ball it.

Aptera's "tail" and vents already take care of this for you.

[futura]

Fluid Dynamics is not my field but I believe the main reason is that the dimples only "help" with spherical structures. A golfball is pretty "blunt" as far as aero-shapes go and the dimples help with the surface flow to keep the air "stuck" to the surface farther along the ball surface towards the back.

A "winglike" structure (like Aptera!) doesn't benefit from this dimple method since wing shaped things tend to keep the fluid stuck to their surface longer. There's other "perturbations" that are added to wings like little vertical stub wings to create vortices but those help create lift. Some new wing technology borrows from the shape of the humpback whale flippers which have little protrusions on the front. These have been added to wind-generator blades with good success at lowering the stall speed. Don't know if such a feature would help Aptera much since it's already yielding so little power to push air. It might be that this trade-off isn't worth the manufacturing complexity. Would be fun to simulate on one of those fancy Fluid Dynamics computers though.

Cheers.


http://www.whalepower.com/drupal/files/userfiles/image/humpback_fin.jpg
http://www.whalepower.com/drupal/files/userfiles/image/tubercle_blade_shop.jpg

[Dilekz]

ah thanx karenrei for explaining. I now understand why those rimples are in the golf ball :)

[GunnyD]

I don't think there is a place on the Aptera that would benefit from the dimples. Aptera has done an excellent job of getting the CD down to a minimum.
The dimples have and are being used on other vehicles with a positive advantage. Take a look behind the front fenders and at the rear on this page
http://www.myersmotors.com/index.html

MM wants 35k for that one seater. We won't say ug.. because that is in the eye of the beholder. Others may call the Aptera the same and I don't want to get upset about that.

[IanO]

I once saw a model of the Corbin Sparrow which had 1-2 inch wide dimples like this on trailing surfaces of the body. I walked away smirking because I didn't think they did the same thing at that size on that kind of shape that the smaller dimples do on a tiny rotating spheroid. Anyone know the history behind this feature of the Sparrow?

http://upload.wikimedia.org/wikipedia/commons/0/0c/CorbinSparrow..jpg

[davidrools]

A thorough discussion of the golf ball dimple effect can be found here (http://www.aerospaceweb.org/question/aerodynamics/q0215.shtml). It's a good read. Near the end it explains why dimples don't work well for streamlined bodies like the Aptera. Specifically in the golf ball application, the dimples also improve stability during flight where a smooth ball would behave more erratically.

[n_dawg]

Sorry for the bump, but does anyone remember those Lexus ads, where they mentioned that they dimpled the underbody to improve the aerodynamics? The one where they flipped it over in a wind tunnel?

http://commercial-archive.com/node/110849 is the closest I've gotten to finding it, and they want you to pay money. To watch an ad. The wonders never cease!

[Apteratude]

The dimples on a golf ball create turbulent boundary flow instead of laminar, which takes longer before separating from the sphere, so there's less of a low-pressure wake behind the ball it.

Aptera's "tail" and vents already take care of this for you.

KarenRei is the smartest person ever! Too bad she's taken =( and so am I.

Smart girls, especially techie's are soo coooool. Surfer girls rank right up there too, as long as they're not too buff. :D

[KarenRei]

Lol :) My partner's a geek, too, although she's more of a math geek. She's the sort of person who, like earlier this evening, factors the number on her shopping cart as she shops at the grocery store for fun (usually done by the first aisle). She'll skip a cart if the number looks too easy ;)

[Apteratude]

I love math, but the simple math. I think many people overlook budgeting and investing. In fact I know this. I'm always crunching numbers whether trying to save my employer money or finding the best deals. I think that the numbers are what makes the Aptera so attractive for many of us.

For example:

The Aptera at $30k
Toyota Corolla @ $14K

To most people, that makes the Aptera a rip-off. Many people I talk to balk at the price until I show them the math.

Gas @ $4.00 a gallon over 150k miles (my avg yearly mileage) = $20K
Electricity costs maybe $2-$4k.

So, add it up...and you get a nearly identical #'s after factoring in sales tax, and all the rest. Not factoring in maintenance or repairs.

So it comes down to what you'd rather drive! Maybe a Corolla is a bit more versatile, but define versatility! Versatile in it's passenger compartment & comfort level, but let's say fuel becomes scarce as it did during the Hurricanes of 2005 when I lived in North Carolina. Stations saw a rapid rise in fuel cost, and gasoline was sold out at 4 out of 5 stations where I lived. Suddenly when fuel is out, your ICE powered car becomes far less versatile.

For me it's a chance to help improve the state of our environment, and increase energy independence; among many other reasons.

[KarenRei]

Yeah -- run out of gas in an area where the only thing around is the occasional farmhouse, and you're out of luck. But you can still charge an EV at a farmhouse if the owner is amenable :) And it'd be easier to push the Aptera there, too, than a 2500lb Corolla without the advantage of low rolling resistance tires.

You go 150k miles a year? Yowzers! That's 410 miles a day! You'll pay off an Aptera in no time, driving like that ;) Even for an average driver, the Aptera still often makes financial sense when you consider the lower maintenance from the reduced number of parts as well as the energy savings -- something you can almost never claim about buying a new car. Especially when you point out how long the batteries last, how they don't just "die", and how little it'd likely cost to replace them 10, 15 years down the road if you wanted/needed to when you spread the cost out over the life of the vehicle. If 10 years from now lithium phosphate batteries are $0.20/kWh thanks to mass production, which is a perfectly reasonable number if EVs and PHEVs are successful, that's only $2000. Spread that out over a decade or two...

I like the fact that while there's only two seats, the "trunk" is actually quite big -- 15.9 cubic feet. That's almost two thirds of a cubic yard. No storage problems here. :)

[Tamerlin]

Do you know what the Aptera is missing? Dimples:

http://www.popularmechanics.com/automotive/new_cars/4316702.html

Even if the dimple idea doesn't increase fuel effiency, maybe the skin wrapping is the easiest way to "paint" the Aptera different colors. How about a nice green flame effect...

[KarenRei]

I'd think that'd be bad for the Aptera. Dimples are a somewhat lossy way to delay flow separation and thus reduce drag... but that's what the Aptera's stretched shape is for in the first place.

[NeilBlanchard]

Hi,

The PM article actually shows a slight loss of efficiency with the dimpled skin...it's a monumental waste of money.

[Ardie3301]

As an alternate to the expensive process of creating dimples in the actual structure, Dimple tape is available as a clear Scotch-like adhesive tape (with large perforations in it). The dimples are supposed to be most effective when placed at the "fattest" part of the aerodynamic body. For the 2e, it would be maybe six inches behind the top of the 2e's windshield, wrapping all around the vehicle like a gigantic cigar band.
(see http://www.dimpletape.com/)

There is another firm that is making a similar kind of tape using a sawtooth design instead of perforated dimples, claiming similar improvements in reduced drag. They call it Turbulator Tape.

The concept is to deliberately induce whirling vortexes of air, forcing the air particles to hug the areodynamic body more closely, reducing overall drag.

In the aircraft industry, there are also gizmos called vortex generators, that look like a dozen tiny little 1/2" x 1" long razor blades poking up vertically from the wing in line with the airstream, but offset by about 15 degrees sideways from the airflow like tiny rudders. They, too, generate little vortexes to allow the airflow to more closely hug the aerodynamic body (the wing in this case), which works even better when the wing's flaps are extended. The airflow more closely hugs the flaps, improving lift so the plane can fly even more slowly. However, those vortex generators reduce the plane's cruise speed by 3 - 4 mph.

Another such concept of reducing vortexes in the aircraft industry is to put those little upswept wingtips on the aircraft. There is a company (Aviation Partners, Inc) that is practically guaranteeing (!) a 6% improvement in fuel efficiency. That's almost like getting every 20th flight for free. (Airline executives will practically kill their own grandmother to get a 5% reduction in cost.)

On a little bit of thought, deliberately inducing vortexes isn't without some kind of cost. It just depends on the aerodynamic body in question. Some bodies create large vortexes on their own, and the dimples may reduce them, giving an overall reduction in drag. Other bodies have already reduced those large vortexes, so dimples won't do anything for them.

Once we get a production 2e, we can gauge the drag "before" and "after" putting dimple tape on various locations and see if the Aptera aerodynamicists got it right the first time.

-- Ardie

[NeilBlanchard]

Hi,

You can make your own turbulator tape (aka zigzag tape) with pinking shears:
http://img.photobucket.com/albums/v724/NeilBlanchard/ZigZag-01.png