Date: Mon, 18 Oct 2004 10:08:36 -0500
Reply-To: Bruce Nadig <motorbruce@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Bruce Nadig <motorbruce@HOTMAIL.COM>
Subject: Re: aerodynamics, was: 101 MPH Vanagon!
Content-Type: text/plain; format=flowed
O.K., I've seen all sorts of formulas and explanations for aerodynamics and
drag. What I haven't seen is actual numbers for a Vanagon. Does anyone know
the actual coefficient of drag for a Vanagon? Does anyone know what frontal
area of a Vanagon is? Without this information, all the formulas in the
world are pretty useless for us.
Inquiring minds want to know.
Cheers,
Bruce
motorbruce
motorbruce@hotmail.com
>From: jimt <wetwesty@TACTICAL-BUS.INFO>
>Reply-To: jimt <wetwesty@TACTICAL-BUS.INFO>
>To: vanagon@GERRY.VANAGON.COM
>Subject: Re: aerodynamics, was: 101 MPH Vanagon!
>Date: Mon, 18 Oct 2004 06:29:47 -0600
>
>The formula for drag through a medium is:
>
>Drag = 1/2 D x Cd x A x Vsquared
>
>D = density of medium (in this case air)
>Cd= drag coefficient (slipperiness) (need to know this value or get a wind
>tunnel)
>A = the frontal area
>V = velocity
>
>Note where the coefficient and area are in the equation.
>Then comes the kicker. Note that velocity gets squared.
>With squaring there is always a point where the squared item goes from
>insignificant to very significant. In this case the velocity we are
>traveling at.
>
>This number is then added to the rolling drag. Computed from weight volume
>and resistance items. Then you get your total drag or resistance to
>movement.
>
>0.00255754 1 16 1 0.04
>0.00255754 0.5 30 1 0.04
>
>Above shows that a flat box surface presented in direct resistance comes up
>with the same value as the lower slippery vehicle that has about twice the
>area presented.
>
>
>jimt
>Planned insanity is best.
>Remember that sanity is optional.
>http://www.tactical-bus.info (tech info)
>http://www.westydriver.com
>
>
>
>On 10/18/04 5:39 AM, "Eric Zeno" <vw4x4@FYI.NET> wrote:
>
> > Aerodynamically everybody seems to be missing one thing.
> > If I have a very unslippery vehicle with a coefficient of 1 (flat
>surface)
> > and a slippery vehicle of .5 and the surface area in question on the .5
> > vehicle is 3 times the area of the vehicle with a rating of 1, the .5
> > vehicle is much higher in resistance than the vehicle with a rating of
>1.
> >
> >
> > Interesting! By what critera is the surface area measured?
> > I've never seen spec's
> > on this. Eric
> >
> >
> > jimt wrote:
> >
> >> On 10/17/04 8:53 PM, "Stan Wilder" <wilden1-1@SBCGLOBAL.NET> wrote:
> >>
> >>
> >>
> >>> With less than 100 hp the dream of 100 in a Vanagon is just a dream
>unless
> >>> you drive off cliff and read your airspeed indicator on the way down.
> >>> I think Bruce just dropped the hammer on his hybrid toy to see how
> >>> everything behaved and reached that 101 as part of the test but that
>brings
> >>> up the speedometer error that is about 10% and that means he was only
>doing
> >>> 92 mph. Well within reasonable speeds for Texas Highways for all
>Pickup
> >>> trucks, SUVs, MPVs, 18 wheelers, and Rice Rockets of both the two and
>four
> >>> wheel varieties.
> >>>
> >>> Stan Wilder
> >>> High Performance Ceramic Coatings
> >>> www.engineceramics.com
> >>>
> >>>
> >> Last year after a proper breakin on my subie mod I took it out on the
>flats
> >> on i70 towards kansas. Took it up to just under 6k on the tach. At
>that
> >> speed my speedo is definitely off by very close to 15 percent. (only
>goes
> >> to 85). However 5.8 x 18 is comfortably (uncomfortably) over 100mph.
>Havent
> >> done it since and donΉt plan on it. Even at a moderate 80mph a
>crosswind is
> >> not nice in a vanagon or any slabsided vehicle. For a regular vanagon
>to
> >> hit those speeds is right at the cutoff. The subie electronic cutout
>is at
> >> about 6.2k the vanagon electronics cuts out at about 5.8k plus or
>minus a
> >> little. I am told that the last couple years of the vanagon the ecu
>cutout
> >> at 6k but no change was made to part numbers.
> >>
> >> Aerodynamically everybody seems to be missing one thing.
> >> If I have a very unslippery vehicle with a coefficient of 1 (flat
>surface)
> >> and a slippery vehicle of .5 and the surface area in question on the .5
> >> vehicle is 3 times the area of the vehicle with a rating of 1, the .5
> >> vehicle is much higher in resistance than the vehicle with a rating of
>1.
> >>
> >>
>
>
>jimt
>Planned insanity is best.
>Remember that sanity is optional.
>http://www.tactical-bus.info (tech info)
>http://www.westydriver.com
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