Date: Thu, 21 Jan 2010 09:45:31 -0500
Reply-To: mcneely4@COX.NET
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dave Mcneely <mcneely4@COX.NET>
Subject: Re: van aerodynamics,
was Re: BenT's dream vanagon now for sale
Content-Type: text/plain; charset=UTF-8; format=flowed; delsp=no
Actually, Alistair, you are the one who said that common sense was
worthless here (what you really stated was that I didn't know what I was
talking about, a criticism that was put in an insulting manner and was
unnecessary, as I had already stated it myself concerning my lack of
knowledge about aerodynamics). Now you are drawing on common sense
yourself, which is fine with me. You are probably right that the brick
shape is the biggest problem with the van, as it is with other vans.
If the luggage rack does contribute a major drag that the "bunny camper"
avoids, why would it not be better, if a luggage rack is needed, to
simply put a bar rack on that vehicle when needed, leaving it off for
other driving? Of course, the point is moot, because such campers are
not available to most of us.
Your explanation and that of others concerning the "hole" of the luggage
rack leads me to wonder if placing cargo in the rack, even if it
protrudes upward a fair bit, is no worse, aerodynamically, than leaving
it empty. Your thoughts on this? After a low gas mileage experience on
a very hot and extremely windy drive across western Oklahoma and the
Texas Panhandle with dry bags up there, I have avoided putting stuff in
the rack. Maybe there is no particular reason to do so.
David Mc
On Wed, Jan 20, 2010 at 11:56 PM, Alistair Bell wrote:
> couple of things,
>
> Chris- yup, the underside is a mess. height ride shouldn't make that
> much diff. Lowered race cars with damns and skirt etc aside. Thinking
> about it, maybe higher vans would suffer less drag underneath,
> (perhaps less ground effect drag).
>
> Dave - hard to explain all in short form. But what you are looking
> for in an aerodynamically slicker shape are gentle transitions in air
> pressure. In the vanagon, if one could colour the air around the van
> as it moves, red for high pressure, blue for low, then you'd see red
> at front, blue at rear, and the various hues between. having the pop
> top the way the bunny van had it would be, IMHO, in a region of lower
> air pressure than the front of the van . maybe think of it as
> "filling in a space". I'd even make a beer bet it contributes less
> drag than the standard pop top
>
> the biggest drag in the van is the low pressure at the rear. I'd
> guess it dwarfs any other factor.
>
>
> Its all best guesses, but as others have said, common sense seems to
> fail in fluid dynamics.
>
>
> alistair
>
>
> On 20-Jan-10, at 10:08 AM, Chris S wrote:
>
> People tend to pay attention to what they see and ignore what they
> don't. If the top of our Vanagons looked like the underside we'd do
> something about it. There's quite a bit of airflow and consequently
> drag generated there, especially in the taller vans, and that presents
> a big opportunity for improvement.
>
> 2010/1/20, Alistair Bell :
>> Not so fast there DM, we've hashed this before :)
>>
>> Leaving aside the big low pressure area behind the van, its seems
>> from the limited info out there, that the luggage rack on a standard
>> westy is a bit of a drag.
>>
>> See the pics here:
>> http://shufti.wordpress.com/2009/11/10/vanagon-bustle/e349/
>>
>> alistair
>>
>>
>>
>> On 20-Jan-10, at 7:22 AM, Dave Mcneely wrote:
>>
>> Though our vehicles are far from aerodynamic, I would think this
>> would
>> be much less so. David
>>
>>
>> On Wed, Jan 20, 2010 at 9:18 AM, Alistair Bell wrote:
>>
>>> yes, makes you wonder about possibility of water/wind ingress when
>>> driving.
>>>
>>> alistair
>>>
>>>
>>>
>>> On 20-Jan-10, at 6:13 AM, Dave Mcneely wrote:
>>>
>>> Has a poptop, but no luggage rack. I've never seen one like that.
>>> That's a lot more interesting than the playboy bunnies on the side.
>>>
>>> David
>>
>
>
> --
> Chris S.
> Disclaimer: "Death and serious injury may occur"
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