# Drag Coefficient, Range, and doing More with Less

## Comments

### Re: Drag Coefficient, Range, and doing More with Less

I went out with three vehicles (below) and made several runs with each.

You have to be a little careful in using this to compare between vehicles. Just because your coefficients are low doesn't mean your vehicle is necessarily more efficient. In order to get the same lousy mileage out of a Geo Metro that you get from a Hummer you'd have to drag a sail. It's a mass thing.

"we must be the change we wish to see in the world"

### Re: Drag Coefficient, Range, and doing More with Less

You have to be a little careful in using this to compare between vehicles. Just because your coefficients are low doesn't mean your vehicle is necessarily more efficient.

Yeah, it's kinda like comparing apples and jalapenos. But I'm being inspired by the simplicity of the designs these ecomodder people have done to see what miles/gallon improvements I can get with my Tracker. Hmm, I didn't mean to get into a comparison between vehicles but I did that didn't I.

- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
- Electrified Electra To

### Re: Drag Coefficient, Range, and doing More with Less

If you want to compare BEFORE and AFTER of the same vehicle with and without fairings, then you could use a hill in the neighborhood and measure top speed, and distance traveled on the bottom of the hill when coasting down the hill.
Pick a small hill, or you'll run into trouble with the speed limit once you've got a good fairing going....

Mr. Mik

This information may be used entirely at your own risk.

There is always a way if there is no other way!

### Re: Drag Coefficient, Range, and doing More with Less

David - bikes, in general, have terrible co-efficients of drag (Cd). Cd is greatly affected by non-smooth surfaces which disrupt airflow, not just frontal area. An exposed rider on a bike is a Cd nightmare!

Also, I don't expect a windshield to affect Cd very much - if anything it might make it better. On the one hand it's another "protuberance" to disturb airflow. On the other hand, depending on the design, it may make the air flow around the rider more efficiently than having no fairing.

The best shape for the lowest Cd, as you know, is the teardrop enclosure. The other day I had a kind of after the fact "brainwave" - it now seems "obvious" to me that this is the best shape. Nature shows us - look at a rain drop. It's malleable, and it falls towards earth with no force other then wind resistance stopping it - thus it will naturally form the most efficient shape.

Alas, I'm still vain enough that I just don't like teardrop enclosed bikes or cars - they just don't look good. I know, that's a lame reason not to use one, but there you have it...

John H. Founder of Current Motor Company - opinions on this site belong to me; not to my employer
Remember: " 'lectric for local. diesel for distance" - JTH, Amp Bros || "No Gas.

### Re: Drag Coefficient, Range, and doing More with Less

John, we're clearly thinking along the same lines. And you're thinking along the lines Craig Vetter is talking about:-

http://craigvetter.com/pages/470MPG/470MPG%20Main.html

http://craigvetter.com/pages/470MPG/Last%20Vetter%20Fairing.html

http://craigvetter.com/pages/470MPG/470MPG%20Main.html#anchor

http://craigvetter.com/Movies/Vetter_DVD_preview.mov - this is a promo for a 70 minute DVD you can get from the above links.

http://craigvetter.com/pages/470MPG/high%20mileage%20fairing.html

Remember, I have one of his fairings leaning against my garage and this is phase 2 of the Lectra. On his DVD he talks about how certain vehicles from fish to airplanes have proved that a certain shape is the most aerodynamic -- in that they produce the best results in moving through air for the least input of energy. Since energy availability is a key achilles heel of EV's I think aerodynamics should be a fruitful way to improve EV performance.

What do you think of the Aptera? It follows the same shape. But for me looking at the pictures it looks like some kind of caricature of a vehicle, and it mostly looks like an airplane. But it also is clearly very aerodynamic.

Vetter hasn't invented anything new ... He just proved it in a contest and has publicised it a bit. On his DVD he describes how European motorcycle racers -- until the mid 1960's -- used full fairings over their motorcycles and were just going faster and faster and faster until the racing commission stepped in and changed the rules for fairings. Such as requiring the fairing leave the front wheel exposed and some other details. This increased the drag coefficient and had the effect of slowing the riders down to more rational speeds. But that fairing design is what became the standard fairing of performance bikes like the Ninja.

At the moment I'm in Belgium getting ready to attend an open source software conference. On the streets here I've seen a few instances of scooters that have a nearly full fairing. The front fairing goes to a full windshield, that goes to a roof, and the roof then mounts behind the rider. The sides are open but I think their legs are protected from the wind. I'll try to get a picture. Actually it looks a lot like the Quasar motorcycle

- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
- Electrified Electra To

### Re: Drag Coefficient, Range, and doing More with Less

Dear David, I've known for a long time that a fairing is probably worth the effort, especially over 20 MPH. However, your very useful research and links have really opened my eyes as to how dramatically a well-designed whole-body fairing can effect fuel consumption.

Taking a 100+ MPG 250cc scooter and adding a comprehensive fairing, and then changing the gearing because of the lowered wind resistance, can result in over 200 MPG.

After some research I did a while back, I concluded that home-distilling ethanol was feasable, but for a 25 MPG car, it was more trouble than I was willing to commit to (am now a fan of WVO, attempting to brainwash wife...don't hold your breath).

However! at 200 MPG,...my work commute is now 14 mi/day (5 days/week), so, roughly one gallon of ethanol every two weeks.

### Re: Drag Coefficient, Range, and doing More with Less

Most aerodynamic bodies try to get as close as possible to the ideal "teardrop" shape, with as few minor compromises as possible. (Like the "Aptera")

Daimler-Chrysler engineers stumbled across a reference on the shape of the "Boxfish" which indicated that inspite of its fairly chunky (and useful) shape, it had a suprisingly low Cd of drag.

http://autos.msn.com/as/minishow/article.aspx?contentID=4024039&s=bibendum2006

### Re: Drag Coefficient, Range, and doing More with Less

I just read (April '08) in Wired about the peraves fully enclosed motorcycle (BMW engine).

http://www.wired.com/cars/futuretransport/magazine/16-04/pl_motor_mono

I think the price is \$70K+, and only gets 57 MPG, but they claim hot-rod performance free from the weather

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