[DeTomaso] Pantera Aerodynamics

michael at michaelshortt.com michael at michaelshortt.com
Wed Nov 12 10:32:19 EST 2008


The cause of the hood rising when unlatched is NOT the air coming in through
the radiator, no formula here, just actual experience.  My radiator top
access is blocked off by a SS plate, and the air can't get through there.
period.  The hood still rises about 2" at speed and settles at rest.  It has
done this in the rain once ( before I figured out that the catch wasn't
bent, but the latch was loose....duh) and there were no water trails on the
fine layer of dust on the SS, so nothing ( no rushing air containing water )
even came through the tiny crack at the leading edge of the hood.

It must be low air pressure sucking the hood up.

While not a licensed pilot I did take lessons 25 years ago and it seems to
me that the hood's angle of attack would create a low pressure area near the
windshield (Bernoulli effect??? sp). sorta like how loose paper in the back
of a pick up doesn't want to blow out but rather blows around in a circle
inside the bed when the tailgate is up ( like a windshield would be in
relation to the hood ).

Michael in Savannah

On Tue, Nov 11, 2008 at 9:27 PM, Dave Londry <davel at emspace.com> wrote:

> I don't see anyone trying to help out with the static pressure
> measurement Michael,
> so maybe I can kick off some responses.
>
> The static pressure would be measured by placing the measurement inlet
> at 90 degrees to the airflow direction.
> This isn't too helpful when you don't know the airflow direction.
> If you try to stop the airflow at the inlet by covering it with foam, I
> think you'll be creating a local pressure increase and measuring that.
> If you had a surplus pitot-static tube laying around and a way to
> manoeuvre it,
> you could get it pointed in the direction of max airspeed and then take
> the static reading.
>
> Maybe more useful if you measure the pitot pressure at a point
> (so changing the direction of your inlet until it you find the max,
> which will be pointed directly int the flow)
> and then you measure the pitot pressure in the free airstream.
>
> The difference between the two should be the local static pressure, because
> static pressure + dynamic pressure = total pressure (a constant)
>
> Now - maybe somebody who knows something will give you a useful answer.
> dave
>
>
> --
> Dave Londry
> Embedded Spaces Inc. (ESI)
>
> michael frazier wrote:
> > Ken wrote:  I suspect that you are comparing apples to oranges here.  I
> think the hood raises because of low pressure above the hood's top surface
> and the wiper raise because of the air flow past them.
> >   I agree.  The wipers are right in a high speed flow area, kinda 45
> degree upward angle if I'm not wrong.  I've been meaning to
> > do some more tuft tests.  The problem is getting a fast enough
> chase/photo car, a decent non-panicky photographer, and miles of
> > empty road where you can use 2 lanes.  Not as easy as it sounds.
> >   Another question.  If I wanted to do a simple pressure test using clear
> tubing and water columns, how would I take wind speed out
> > of the equation.  Some open cell foam or filter to keep wind speed and
> direction issues out.  Sorry, I'm not drillin' holes and mounted
> > the tubes flush.  That might alter the flat black flow characteristics.
> > Michael
> > Gruppo Rompiculi Corsa...if you mounted one of those boat propeller
> trailer hitch covers on your Pantera's rear cross member...which way would
> it turn?
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> >
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-- 
Michael L. Shortt
Savannah, Georgia
www.michaelshortt.com
michael at michaelshortt.com
912-232-9390


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