Scaling the Template

[kach22i]

I was taking a walk today and noticed an original Audio TT, one without the rear spoiler which they added after the first few months of sales. Apparently the rear lift could be dangerous under certain conditions and they sought to limit lawsuits, so they gave and installed the spoilers for free and retrofit them to cars.

My thoughts went to....well you have to have airflow for a spoiler to work, so they at least had good airflow.

Automobile 2 - Odds And Ends Photos by kach22i | Photobucket


This will make me no friends here, but screw it, I'd rather be right than popular. The template is not a religion to me, and cult followings make me nervous.

Add to the fact that the template is not 3D, and I might be a bit miffed about it in retrospect.

How can you have meaningful exercises based on a 2d shape anyway?

The larger you can make the template on your vehicle the better. A full 100% scale is best, but sometimes (most times) some scaled fit is better than nothing at all.

More car wind-tunnel and smoke images are found here:
http://bigmike.marlincrawler.com/for...php?topic=33.0

[freebeard]

That's why I often capitalize Thee Template™; I'm passive-agressive.

The answer to your frustration is the Boxfish


and maybe the Volkhart-Saggita

[Xist]

Audi TT 1998 - 2006 0.34
Vehicle Coefficient of Drag List - EcoModder

[freebeard]

ChazInMT -- ...if that's what your name really is. If he crossed a line in those 2 posts he was dragging me along with him. "Squircle"

This now makes you a troll, your last posts are clearly in the realm of trolldome and have been reported as such.

Troll!

[MetroMPG]

Kachi - considering the accumulated evidence & studies presented to explain and refine The Template (TM), calling its application "religious" or "cultish" is simplistic and disrespectful.

It's fine to question things, but please try to be civil while participating.

[freebeard]

Batman Jr. has spoken. I apologize ChazInMT, ', or whatever your real name is.'

My eye slid right over those bad words. It's OK to say Squircle, right?

[MetroMPG]

Just to be clear: I really don't care if someone wants to question the thinking behind the aero template. How that's done is the issue. That's all.

PS: Squircle is borderline heresy. Very dangerous.

(I kid.)

[aerohead]

Originally Posted by ChazInMT

I think it lines up great with the 2nd Gen Aero Template.



Bigger Version


Here is a comparison of the old template (Green Line) vs the new one (Red). Aerohead figured out a shorter faster template might be a smidge better if you read what he wrote in the Aerodynamic Streamlining Template: Part C thread.




Bigger Version

Here is a link to the new template outline alone in HiRes if you wanna grab it. Made it Just4U.

Oh. And you still can scale the thing if you want, and you're right, you'll probably have attached flow when you do scale it, but it won't be an optimized shape.

The template is a guide to optimize the shape of an Entire Vehicle, because when you scale it to fit, the top line of the rear portion automatically becomes the ideal shape the air likes to see for the least overall resistance taking into account the form drag and the skin drag.

And most cars are flat on top for 4-6 feet across, making them something of a wide 2D shape, so you may wanna think about that before you muddy the waters with a 2D vs 3D thing. If you want to build a trike or bike, then you may not be able to make much use of the template because they are taller than they are wide.

Finally, 0.13 is the ideal Cd for a vehicle following the template.

Found it here

Yes,the 2nd-gen 'Template' attempts to rectify 'discrepancies' found when fitting the 1st-gen AST when considering cars like Insight,Prius,XL1.
The difference is subtle but also significant when considering forms.

[aerohead]

For Klemperer's Cd 0.15 -0.16 model :
*Search for Phil Knox aerodynamic photo albums
*go to Book illustrations
*page-1
*Row-5
*2nd graphic from right
*2nd image from top
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Klemperer was a graduate engineer working under Paul Jaray at the Zeppelin Werke in Germany who received his P.hD. within a year.
In 1921 Klemperer tested wind tunnel models in the Zeppelin wind tunnel for Jaray and also tested this model for himself.
He measured Cd 0.16 in 1921 and published in 1922.
It appears that Hucho came up with Cd 0.15 with the same model in a modern wind tunnel during the work on the VW 2000 project.
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Klemperer measured Cd 0.13 for Paul Jaray's half-body 'pumpkin seed'.Hucho's 1970s re-testing suggests that Jaray's pumpkin seed would be belowCd 0.13. Jaray's pumpkin seed is the premise of the 'Aerodynamic Streamlining Template.'
This form has been used many times for record vehicles.The British are using it this year at Cambridge University for their go at the World Solar Challenge.

[aerohead]

Originally Posted by kach22i

In my search to find images of this vehicle I found an intersting website.

Concept Cars and Aerodynamics, 1917-1940
by PETE on MAY 2, 2013
Concept Cars and Aerodynamics, 1917-1940


Still no signs of the Klemperer in question.

EDIT-1:



Seems to me like there are very limited opportunities to apply the template to existing and typically flat sided (and rectangular wheel layout) automobiles.

I don't think that I'll even bother considering these limitations, as it will never be perfect. Anyone who does a template overlay must be a misguided fool and totally ignorant to boot, right?:

http://ecomodder.com/forum/showthrea...c-9287-13.html


http://ecomodder.com/forum/showthrea...c-9287-47.html





Is this the official Part-C aero-Template Cross Section?

Squircle - Wikipedia, the free encyclopedia


I've always assumed the Part-C aero-template would look like this (see image below) in front view, but I'm still looking for it.

An Illustrated History Of Automotive Aerodynamics – In Three Parts | The Truth About Cars

*From the side,the 'Template' is half of a teardrop,minus what is cut away to create the ground clearance.
*When the Template is coming at you,you see a semicircle minus the area removed for its 'ground clearance.
*From above you see a full teardrop.minus the area which was cut away for the ground clearance.
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The intent of the 'Template' is to provide a safe contour for boat-tailing primarily passenger cars,as they are the majority of vehicles sold.
*based on whatever your starting with,however you can morph it,and integrate it into your vehicle,it would provide a separation-free surface for reducing pressure drag.
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As to the overlay,well the problem is that it is perfect.It is the tyranny of singularity.Some people will never lose their attachment to the notion that you'd never find a single solution for drag reduction.
I have some additions I'd like to add to the thread.I've been without transportation for going on 12-weeks now.I hitch a ride into town to come here.When I leave I have a 7-mile walk home.It's a bit awkward to carry materials here and back.
I have every intention to 'complete' the thread.I have no earthly idea when I'll be able to do that.
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If you want to depart from science go ahead.You're certainly under no obligation to anyone.Perhaps you'll find solutions elsewhere.
Best to you!