Date: Wed, 24 Mar 2004 12:06:52 -0800
Reply-To: Randy Bergum <organslave@EARTHLINK.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Randy Bergum <organslave@EARTHLINK.NET>
Subject: Re: Vanagon Drag Coefficient?
Content-type: text/plain; charset=US-ASCII
If you could round off the front a little more, that would save a bit. VW
found that rounding the nose of the original bus, 30% drag reduction was
realized! (This from a professor at engineering school)
Bruce Carmichael has done research on torpedo design for the navy, and
found that by using a laminar flow shaped body, they could use a much
larger frontal area and volume than the standard cigar shape for the same
drag. This shape was roughly like an egg up to around 40% or so from the
front, then necked in to cause favorable pressure gradients and keep things
flowing as best they could. I can't remember the numbers, but the drag was
reduced to something around 20% of original. I recall that they made a
body of revolution from a good laminar airfoil curve raised to the 3/2
power to account for the 3rd dimension.
Unfortunately the navy nixed the idea, because it didn't fit into their
idea of how a torpedo should fit and work inside the launching tubes.
Look at new cars and see how windshield seams and bumps are being reduced
way down, and airflow is smoothed more. For an extreme example, see the
one liter car that VW made recently.
But what the heck do I know?
Randy Bergum
> [Original Message]
> From: Frank Grunthaner <FrankGRUN@AOL.COM>
> To: <vanagon@GERRY.VANAGON.COM>
> Date: 3/23/2004 4:58:17 PM
> Subject: Re: Re: Vanagon Drag Coefficient?
>
> In a message dated 3/23/04 4:18:24 PM, wilden1-1@SBCGLOBAL.NET writes:
>
>
> > Before the golf ball dimple technology works you need a full belly pan
and
> > enough horsepower to make the project worthwhile.
> > For a good working example just lay down and look under a Porsche of any
> > year.
> >
> > Stan Wilder
> >
>
> Stan,
>
> This is a good point and I have considered 0.0625 inch thick Al sheet for
> such a purpose, but never quite had the time to do it.
>
> More effective, though, would be a pressure deformable inflatable
truncated
> hemispherical surface mounted to the rear of the Vanagon. By controlling
the
> inflation pressure, at a constant velocity, while optimizing manifold
vacuum,
> one should be able to reduce drag by 20% or more. If you then fixed the
shape
> and made a mold, one could market a baggage extension which also reduce
drag.
> Does require moving outside the original vehicle envelope!
>
> Frank Grunthaner
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