[Land-speed] Land-speed Digest, Vol 2, Issue 101

[David Dymaxion]

I've had several questions and great comments off-list, so I thought it worth a public reply.

I'm currently converting a old Porsche 911 to electric power, and plan to run it on the Salt at World of Speed. My goals are just getting it to run this year, 130 club this and maybe next year, then 150 club, and then all out. If it breaks 130 mph I'll be very happy, and if it breaks 150 mph I'll be ecstatic! So one origin of my question was thinking whether it is better to lower the car and put on an air dam, or to leave it higher and smooth the underside. The 100% consensus has been low + air dam. BTW, I love my Camaro and really wanted to do an electric Camaro, but moving the extra 1000 pounds quickly enough would have doubled the project cost.

The 2nd line of thought was I thought the new electrathon class for USFRA was really neat. One went 89 mph last year, with exposed wheels, on just 67 pounds of battery. I think it would be fun, and cost effective, someday to build an electrathon streamliner, but I need to limit myself to one project at a time! Here's a link with some pictures and videos:

http://www.explodingdinosaurs.com/saltflats/2007worldofspeed/electrathon/index.html

So why do some of the most successful solar and electrathon cars go high? Thanks to some of the off-list insights I think I might have figured out why. First, they go slow enough, and speed up and slow down enough, that weight is as much of an issue as aero drag. It makes sense to me you could build a vehicle at axle height lighter than one low to the ground (less bodywork).

From: "Glen Barrett" <speedtimer at beyondbb.com>
David
On www.landracing.com there has been lots of discussion on AERO. Check it 
out in the LSR venues or archives. Lots of info and ideas there. What are 
you looking to build?
Glen
----- Original Message ----- 
From: "David Dymaxion" <david_dymaxion at yahoo.com>
To: <land-speed at autox.team.net>
Sent: Monday, March 10, 2008 12:30 PM
Subject: [Land-speed] Streamliner Aerodynamics

> On another list we are having a debate about aerodynamics. The fastest 
> solar racers and electrathon racers are finding having the bottom of the 
> car high off the ground (around 8 inches) seems to be giving them better 
> aerodynamics -- but on the flip side their speeds are so much lower they 
> don't have to worry as much about being aerodynamically stable. So here 
> are my questions:
>
> Do streamliners generate aerodynamic downforce?
>
> Are they low for better stability, or less aero drag, or perhaps both?
>
> Is there a good book or web page on streamliner aerodynamics?
>
> Thanks for the info.


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