Date: Sun, 29 Jul 2007 21:48:17 -0400
Reply-To: Wesley Pegden <wes@CS.UCHICAGO.EDU>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Wesley Pegden <wes@CS.UCHICAGO.EDU>
Subject: Re: Some aerodynamic ideas..
In-Reply-To: <001e01c7d191$e927a0e0$2219e442@dhanson>
Content-Type: text/plain; charset=windows-1252
If you look through the archives I seem to remember there being some
hard numbers for this stuff. As I remember, the (passenger) Vanagon has
a pretty good coefficient of drag as it is compared to other cars---even
better than some sports cars. The big problem is the frontal area,
which can't really be tweaked much, except for sacrificing on mirrors.
Anybody want to dig up the COD numbers? What do you think you could
realistically push them down to?
I think an interesting question was what could be done to improve the
drag on a Westy. The Westy drag is significantly greater than in a
passenger van. In fact, the COD is so much worse than hard-top vans
that it has greater drag force than even high-top vans like the
Adventurewagen. I forget what detail of the Westy top was the problem,
but if someone could work out a cost-effective fix that wasn't unsightly
it could be really useful. To do it right you would want access to a
wind tunnel, I guess.
Of course, the real trick is to drive slow. We've had our '83 westy for
a few weeks now, and all 4 tanks of gas have been at better than 21mpg.
I just don't exceed 65, and get excited every time I see a good excuse
to go 60 or 55.
-Wes
Don Hanson wrote:
> The Vanagon is exactly wrong for aero-efficiency...Actually, if it were a
> perfect square rather than a rectangle, it would be worse, but..
>
> So, some of the things that could be done for better slippery...
>
> A front splitter would be about the easiest thing of all. A splitter is
> just a 'shelf', a flat projection off the front, parallel to the ground. In
> essense a splitter fools the air into thinking the vehicle is much longer by
> stacking up air on the top of the splitter. A splitter would also reduce
> the airflow under the van. Since we probably wouldn't be looking for
> 'downforce', limiting the flow under the van would reduce the turbulence
> there somewhat.
> Flush windows would be a help also, and do-able. However, the square
> front corners of the windscreen probably starts turbulence there right there
> that continues for "a mile" behind the van, so back to the "Entry" the
> nose...the splitter.. Raking back the front windshield would be rather
> effective also, but beyond most of us, what with the doors right there, etc.
> Smooth wheel covers would be an easy improvement..Like those old Moon
> hubcaps..Mirrors that didn't stick way out would help some also.
> But, given the shape of a van, the job of significantly improving it's
> aerodynamic coefficient of drag would be....daunting..
> Don Hanson
>
>
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