NYTimes Aero Article - Edgy, Yet Still Aerodynamic

[Cd]

( What was the Cd of the Epcot 2003 ? , and also, what are the protrusions on the top and bottom of the Sunraycer for ? I'd suspect stability, but I wonder if it was sort of a diffuser on the bottom as well. )

[MetroMPG]

Originally Posted by instarx

why all the discussion of dimples, air tabs, ziggy tape, etc in ecomodder?

You're right: for some reason those particular topics seem to come up over and over and over.

At the risk of offending (not my intention) EM members who have asked about these things, I'd say there has been a fair amount of effort made to try to dispel the "aero myths" that are raised.

Some askers seem to be genuinely curious about the theory & practice (regardless of whether they have an application in car design); others just seem to be on a quest for a magic bullet.

[eco_generator]

Originally Posted by basjoos

These "aeroedges" appear to be mostly bandaids to compensate for aerodynamic inefficiencies downstream from them. So these are just bandaids to allow them to build slightly lower drag versions of "normal" looking cars. However these tricks won't get them anywhere near a Cd in the 0.1's.

Originally Posted by aerohead

Looks to me like aerodynamics has been fully understood since the day of Sir George Cayley in 1800.Newspapers.gotta love 'em!

Agreed on all of your guy's points, but I feel its just a tad bit too harsh. These are people that are working on cars that are essentially locked in shape by forces beyond their control. They are using known techniques in novel ways to lower the "normal" looking cars aerodynamic drag. I applaud them, every little bit helps. The coming boat-tail revolution, well that will come when it arrives.

The game of football has been well understood for decades upon decades, but it's the coach that comes up with novel ways and approaches that fit within the defined rules that will excel. I think you can say the same thing for aerodynamically minded mainstream carmakers. They have to play by the rules that say enough people still must want to buy the car.

[NachtRitter]

^^^ Yes, well said...

[aerohead]

Originally Posted by Cd

( What was the Cd of the Epcot 2003 ? , and also, what are the protrusions on the top and bottom of the Sunraycer for ? I'd suspect stability, but I wonder if it was sort of a diffuser on the bottom as well. )

Cd,I'll have to dig for the Epcot number but I'm pretty sure I've got it.Shooting from the hip I'm remembering around 0.20.One feature I remember from GM's exhibit at Epcot,was that an active rear valence dropped at speed,allowing for a proper diffuser angle without sacrificing ground clearance in town.---------With the respect to the Sunraycer,a safety requirement for the Trans-Australian Solar Challenge,was that the cars could survive buffeting from the triple-trailer trucks which would also share the road with the solar racers.----------------- The "strakes" were added to to the back of Sunraycer,which was prone to lifting off and swapping ends,to help directional stability without shading the PV array.Dr.Morrelli also moved the "vertical stabilizer" of the CNR "banana car" underneath and behind the rear wheels.---------------------- There are also two structures on the roof,behind the "cabin"that might have spoiled side gusts at the center-of-lift,although I don't remember a discussion about them.Anyone?

[aerohead]

Originally Posted by Cd

( What was the Cd of the Epcot 2003 ? , and also, what are the protrusions on the top and bottom of the Sunraycer for ? I'd suspect stability, but I wonder if it was sort of a diffuser on the bottom as well. )

Cd,what I show,is that the Epcot car is the 1982 AERO 2000,with Cd 0.23.------------------ The book "More With Less" has a brief history of the World Solar Challenge,Sunraycer development and competition.The appendages allowed the Sunraycer to survive 40-mph side gusts.