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Old 02-23-2011, 07:40 PM   #122 (permalink)
aerohead
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still lost

Quote:
Originally Posted by MN Driver View Post
I'm still a little lost though looking at this form that we are all talking about. Wouldn't it be more ideal to round the front so the wind goes around the object? It seems like such a flat fist shoving its way into the wind?

I suppose I've always thought the front end would look like the 1980 GM Epcot 2003. Back seats!?
1980 GM Epcot 2003-GM PhotoStore


...or the Synraycer
1988 GM Sunraycer-GM PhotoStore

Possibly round the back off of this 1986 Corvette Indy Concept


I found these through the GM PhotoStore
Concept Vehicles-GM PhotoStore

Why would having a flat front be superior? I'd figure you'd be better off having the back and front be at least somewhat similar for airflow.
MN,if you were above the Template looking down,the front of the vehicle and its sides would have the same 'roundness' and curvature as the side elevation view of the Template,just like an NFL regulation football viewed from any 'side.' The windshield would have compound 3-dimensional curvature as on Sunraycer and the sides would taper to the rear just like the Hindenburg.
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In road vehicle aerodynamics it's easy to get good flow attachment with rather blunt noses.The challenge is to eliminate flow separation at the back,killing the wake,and the only way to do that is to extend the body back.
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The curvature and 'steepness' of the Template is right near the ragged edge for flow attachment.If you go any steeper,you end up with a Granville Bros'.Gee Bee R-1 racer which flat-spins because of its separated flow ahead of the tail/rudder,due to the 25-degree body taper.This 'steepness' kills pilots,and it kills fuel economy.
-------------------------------------------------------------------------- The GM/AeroVironment Sunraycer IS a "Template" vehicle.It projects to 89 % of the template length,with a little reflex camber to accommodate for solar insolation on the PV array.With wheel fairings Sunraycer has Cd 0.089 and 400 mpg equivalency with 10-Bhp I.C. engine.
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Your correct about a 'flat' front although the Template doesn't produce that.Typically in fluid dynamics,for lowest drag,the body structure disrupts the flow within the 1st 1/3rd of body length,then uses the remaining 2/3rds to permit the flow field to re-combine without turbulence,which is exactly the purpose of the Template.
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The PROBE-IV concept used an unusually long nose and short tail to achieve Cd 0.152,although to go lower it would require an extended tail.
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The PROBE-V with Cd 0.137as you will notice,has more tail.
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Fully 'boat-tailed' composite structures,as the NUNA-3 solar racer have Cds reaching below Cd 0.09.That's a long way from 0.152.
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MN Driver (02-25-2011)