Rear Spoilers vs 'template' contour
 

I've gone through 'template' comparisons of telephoto images and technical drawings, published over the decades in ROAD & TRACK. Many were in my photo-bucket archive, but I no longer have access to those, so I can only list them for now:
1964 Shelby Daytona Coupe
1969 Pontiac Trans Am Firebird
1980 Medusa concept ( ItalDesign)
1982 Pontiac Trans Am Firebird
1984 Pontiac Fiero
1985 Renault Alpine V-6
1988 Lotus Esprit Turbo
1990 Opel Calibra
1993 Ferrari 360 Modena
1995 Ferrari F355 Berlinetta
1997 Dodge Viper Coupe
1998 Toyota MR 2
2009 Nissan 370-Z Sport
2010 Honda Accord Crosstour
2011 Chevrolet VOLT-I
2012 Audi A7
2012 Subaru BRZ
2012 Audi TT RS Coupe
2013 Aston Martin Vanquish
2014 Audi RS5
2014 Chevrolet Camaro SS 1LE
2015 ACURA NSX
2015 Alfa Romeo 4C
2015 Lexus RC F
2016 Chevrolet Camaro SS
2016 Mercedes-Benz IAA concept ( with boat-tail extended )
2016 Porsche 911 GT3 RS ( fixed spoiler below wing )
2017 Porsche 911 Turbo S
2018 KIA Stinger GT
2020 Toyota GR Supra
2020 Porsche Taycan ( flip-up unit )
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Since this thread will be easily accessible, I'll be able to add data as it becomes available.
Over time, I'll figure out about posting images. I lost over a month's income in the photo-bucket debacle and if I'm going to go to the expense of doing new images, I need an iron-clad guarantee that we won't lose any of them.

Anyone who still believes the template shows where airflow goes simply has their eyes shut.

Tesla Model S not obeying the template:

https://i.postimg.cc/d160XBZ9/BS-template.png

https://i.postimg.cc/QdB7Bf6z/B-23.jpg


Jaguar XE not obeying the template:

https://i.postimg.cc/26Hs1zcn/BS-template-2.png

https://i.postimg.cc/PJgjSrjY/B-19.jpg

(Colder colour = high pressure):

https://i.postimg.cc/qgVP8bsG/B-3.png


Honda Insight not obeying the template:

https://i.postimg.cc/zBgX8011/BS-template-3.png

https://i.postimg.cc/HkD0ghDT/DSC-1547.jpg



Honda Legend not obeying the template:

https://i.postimg.cc/3Jnsdm14/BS-template-4.png

https://i.postimg.cc/8kwKHD6x/Figure-6-65a.jpg


And of course the idea that a rear spoiler causes flow reattachment is completely wrong for any car of about the last 30 years. The rear flow is already attached...

That's why this rear spoiler, that reaches no higher than the standard car profile, measurably increases pressures on the hatch:

https://i.postimg.cc/DZWy5D0F/000589.jpg


Rather than looking at pictures in magazines, you would learn a very great deal more by testing some actual cars.

https://www.ford-trucks.com/wp-conte...dead-horse.gif
https://www.ford-trucks.com/wp-conte...dead-horse.gif

I don't like it when people spread misinformation. In more than 30 years of writing about car modification, I've seen too many people waste their time and hard-earned money following bad advice.

Following a template when modifying car aero is a classic example - the equivalent of saying that an AFR of 12.5:1 always gives best power.

Julian, you've already said this all before. Jamming a new thread with repeats of the same images you have posted repeatedly before is simply bullying.

To be fair, aerohead also repeatedly posts lists of cars like this; this is the second such thread in just a few weeks. If you're going to criticize someone for saying the same thing again and again, give credit where credit is due.

We all have more in common than we realize. But viva la dif-France.

Aerohead continually posts information on car aerodynamics that is incorrect and misleading. While I can be bothered, and to prevent others being mislead, I will continue posting information that shows how his posts are incorrect.

If that concerns you, I suggest you take it up with Aerohead - he is the person continually posting material that is incorrect and misleading. Or are you happy to see falsehoods being disseminated?

As California98Civic and Vman455 (and that yahoo at Permalink #3) suggest disagreement is tolerable but excessive verbosity is not. And excessive capitalization of handles.

Again, take that up with Aerohead not me. In fact my post used the premise 'a pic is worth a 1000 words' and had very few words (115 in fact) in it. It's Aerohead who writes reams of stuff - one reason I think he has got away with spreading rubbish here for so long... it just overwhelms people.

And as I said to California98Civic: are you happy to see falsehoods being disseminated?

your little picture show of cars that do not meet the template shows one thing:
Drag reduction does not dictate auto shapes, styling does.

This is one reason that I keep posting. You have been sucked in: you are working on the fallacious notion that the template = the lowest drag shape for a road vehicle.

That is simply not so:

https://i.postimg.cc/d3JmHdpS/Different-shapes.png

I guess when the accepted - but incorrect - wisdom has been in place for so long, it's hard to see the wood for the trees.

Or do you really think the Honda Insight designers made some sort of concession to styling on the angle of the rear hatch? That really they wanted a larger wake to match the template - but stylists said no?

https://i.postimg.cc/zBgX8011/BS-template-3.png

I would imagine they used those very expensive wind tunnels on the insight. Good for them, we don't have one.
do A,B, or C above represent anything any of us will drive? Give that up, you have an axe to grind.
Does some form of wake reduction? Yes, it does. In that vein, fineness and attached flow, and curves that behave well in the yawed environment do. We don't drive in wind tunnels.
Take a look at the airstream trailer shape. Those huge radii work well from any angle. If you've towed many travel trailers, large box trailers, it's things like that you begin to appreciate.

How many words in Permalink #3?
Bucky Fuller used to say that houses are really airships anchored to the Earth (paraphrase).

My Airstream has a wickerbill on the NE corner so the wind blows the door closed instead of open.

Sorry, you've lost me.

You don't need an expensive wind tunnel to see that the template is baloney - just do some tuft testing. Zero cost, easy. I don't have a monopoly on testing - do some for yourself.

Furthermore, if the real world, low-drag car shapes developed in a wind tunnel differ substantially from the template, isn't that even more evidence that the template is wrong?

No, A, B and C don't represent what we will drive, just as the template doesn't either. (If it were to meet frontal crash requirements and have minimum head room, I'd suggest a car based on the template would be about 7.4m long. That's about 24 feet.) I ran the solar car pics because you appeared to believe that the template was the lowest drag shape for a road vehicle, and it isn't.

My only axe to grind is against incorrect information being uncritically disseminated.

You keep saying 'uncritically'. Search on terms like 'Thee Holy Template' or 'Procrustean bed'. Nevermind I did it for you.

:D

Yes I do say 'uncritically'. Ancient, long threads are irrelevant to people coming here and seeing bad advice. Errors need to be called out when they are stated - not 'thanked' as they often are. And the more the errors are repeated, the stronger should be the pushback.

It's just one of those strange beliefs I have - people modifying cars shouldn't be given bad advice. Odd I know...

I mean, you only need to look at the title of this thread - absolute misleading rubbish, that I have seen given here as direct advice to someone wanting guidance on a rear spoiler design.

You do you.

It's hard for me to follow nowadays with EcoModder not giving notifications.

Have you thought about putting your energy into the Wiki instead of [contending on] the Forum?

Why would I write a Wiki when I have written a book?

Someone with an Insight could always templetize it and measure the results.

I don't really have a dog in this fight. 99% of the "brain trust" here is leaps and bounds ahead of me when it comes to the technical stuff, but a statement like this is just "trumpet blowing" IMO.

Julian, I am convinced you are an intelligent person. I have watched your videos (admittedly not all of them) and read some of your posts and can see you are no crackpot. A little egotistical at times, but aren't we all to some extent.

Why should you write a Wiki when you have written a book? Maybe so you can share your knowledge with the rest of us lowly aerodynamically challenged "commoners". The information here at EM has been shared freely and no one has ever (to my knowledge) "profited" from giving knowledge to the collective, except in a moral sense. While most of the folks that post here are hig IQ (especailly in this sub-forum) the Wiki area is visited by folks that are looking at trying something and experimenting with a new idea and reporting back to the collective as to how it worked. Most of our DIY home-built "improvements" I'm sure would fail by your standards, but still work. Not perfectly, but they still work. There is something to be said about "Something is better than nothing." But I'm sure you will point out that I am wrong and there are examples (you'll have pictures no doubt) showing that I am wrong. But if a "mod" gives a partial gain then IT IS better than nothing even if it doesn't fit the "template" perfectly or the math isn't perfect.

Write a few Wiki's and let people learn from you. Let the "modder" choose which direction he wants to go rather tell us how we're all "doing it wrong". Your YT videos are free and you take the time to put them together. There is no disclaimer at the beginning that says "You should be happy your getting this for free because I wrote a book that covers all of this." Why not do that here? Personally I have benefited from the mass of information here and even though my crappy little truck is an aero-brick according to your standards, I'm at 7+ mpg over EPA and climbing. That's the reason we are all here. Not to FLAUNT our intelligence to the collective, but to SHARE that same intelligence for the benefit of the collective. Sometimes I think you have a hard time seeing that.

This is just a debate between what is good, better, and best. The template is good; I have seen it help some people on here. But surely it cannot be better than getting unique results to work with for your own vehicle. I don't see a problem with anyone repeating that information, especially since the template is all over this website already.

What hat_man said.

You don't write Wikis you contribute to them. The one at Ecomodder has languished with no contribution in the recent past.

Taylor95 — Way back when, we used to discuss blisters and canopies. And my favorite, the bubble-top coupe. Fertile ground for applying the Template pace Jaray. Roof-top air conditioners on trailers and such.

Them's were the days.

It's not 'trumpet blowing' to say I have written a book on the topic. It's a statement of reality. If I have already written all that I know about the topic in 100,000+ words and 400+ pics, why would I waste my time doing it all over again?

I do the videos only to promote the books. No more, no less. In fact, at the moment I have stopped doing them because Covid has depressed book sales so much it's not worth my time doing the videos.

I honestly don't understand the philosophy that poor advice is better than none. Why not instead aim for good advice? And why this idea that information that is clearly and demonstrably wrong should not be challenged? I've seen that also in other discussion groups and it strikes me as ludicrous: that because we shouldn't rock the boat, we shouldn't call out stuff that people write which is completely wrong. Not just a bit deceptive, but outright wrong.

I've never said that 'the template' is not a low drag shape: I'd imagine it is. But the way that idea has been extrapolated to purport to give guidance to the height of rear spoilers, to guide the shape of car extensions, to be used as some kind of benchmark when judging the aero of existing cars - all are just rubbish. But it gets worse, because the template has then (apparently) fed into Aerohead's weird theory that flow will not stay attached if the shape curves downwards more quickly than the template - and in turn that has led (apparently) to his completely wrong theory on how lift occurs on modern cars.

It's a skyscraper built on a base of sand, and it has resulted in massive misunderstandings that can be seen across almost all aero topics on this group.

No, it's not like that at all.

I've never said that 'the template' is not a low drag shape: I'd imagine it is. But the way that idea has been extrapolated to purport to give guidance to the height of rear spoilers (this thread), to guide the shape of car extensions, to be used as some kind of benchmark when judging the aero of existing cars - all are just rubbish.

But it gets worse, because the template has then (apparently) fed into Aerohead's weird theory that flow will not stay attached if the shape curves downwards more quickly than the template - and in turn that has led (apparently) to his completely wrong theory on how lift occurs on modern cars.

It's a skyscraper built on a base of sand, and it has resulted in massive misunderstandings that can be seen across almost all aero topics on this group.

So what you are saying is that if the advice is deemed as flawed it shouldn't be followed? And if it is followed, then it has no advantage? This is what I mean by something is better than nothing. A "flawed" template is better than no template at all, no?

Should this guy be shot down because his shape didn't meet your idea or Aerohead's idea of the template? I'm sure it could be improved on and needs much refining. People here at EM would share their opinions and knowledge. I have a feeling your only advice would be to buy your book.

I think the "template" we have recognized at EM was designed to be a "smidgeon more conservative" rather than a shape that is "right on the ragged edge of flow seperation."

I wish I could find the drawing of AST-II. It might be more to your liking as I believe it was a bit steeper than AST-I. I also believe someone here stated that "The AST-II is the second-most aggressive profile and fits standard rooflines with rapid descending contours. The AST-I fits more conservative contours."

According to a guy name Hucho, the most aggressive profile was by some other guy named Buchheim. I think that Hucho guy wrote a book also. Too bad he isn't around anymore. I'd bet he'd share his knowledge here in the Wiki section.

Dr Hucho is alive and well - he wrote me an email just last week.

This idea of 'battle of the templates' is just so bizarre. I would suggest never starting with any template at all! Why on earth would you start with a pre-determined shape and not actually develop the best shape for your own car?

Would you take a Nissan Micra's spring, damper and sway bar rates and apply them to your Mercedes 300SEL? Would you take the engine management map from a naturally aspirated V8 and plug them into your four cylinder turbo's engine management? Or, and this is an even closer parallel, would you state that the air/fuel ratio in your car's engine should always be 14.7:1, because that's 'stoichiometric' - the chemically correct proportions for complete combustion?

The canopy shape looks alright - sure. But why on earth wouldn't you first develop the best shape for that vehicle by doing some testing? For example, first just lay a flat sheet from the roof to the tailgate and see if the airflow stays attached. Even better, do that and measure some pressures. The depicted shape might be best, but it's highly likely it isn't.

I think blindly following a template - any template - is an utterly stupid way of modifying car aero. It seems completely predicated on the idea that testing isn't allowed. Just imagine doing engine management or suspension like that - what are the chances you'd luck-out and get the best results by copying what someone says is best for every car?

Back before someone came along and started harping on that template, discussions ranged over Morelli's Banana car and Urban car, Luigi Colani, the Meridith Effect, and &tc.

We had a member that did what CFD analysis he could of the butt trumpet. I haven't found that post but here's the one where I posted it

http://ecomodder.com/forum/member-fr...14-1-42-00.png
https://ecomodder.com/forum/showthre...tml#post496477

The [tentative] conclusion was that it works better than a flat truncation. *another member* confirmed something similar was used by Bochum University and Morelli.

People remember the Schlorwagen but nobody tries to replicate it.

where the airflow goes
 

*Do any of your example cars appear on my list?
*Do you presume that I, or anyone else has the time to waste on un-scientific testing as you conduct, with the expectation of achieving scientific results?
* And why speak as if from a position of knowledge, when your reporting clearly reveals only a grade-school understanding of lift ?
* You remain on the cusp of understanding, while appearing to demonstrate confirmational bias, and prejudice towards facts. An intellectual cul de sac.

misinformation
 

Why do you presume to have a command of discernment with respect to this topic? Does your book collection serve merely as name-dropping bait, or do you actually intend to read them one day for content?
Perhaps the physician who delivered you dropped you on the tile floor of the delivery room. Shame!

aerohead also
 

Would you please provide an example(s) from which I may ponder inaccuracies?

continually incorrect and misleading
 

I wait with baited breath for you to scientifically argue any of your premises.
I've provided chapter and verse, straight out of the mouths of the experts.
Your folk knowledge and prejudice against actual fluid mechanics appears to have become an impenetrable barrier between your mind and reality.
You come off as a complete huckster, using every opportunity to advance book sales, at any cost to fact.
You're not a peer. I'd like you to stop pretending.

rubbish
 

Complicated truth, versus the simple lie.
PLEASE overwhelm us with a DEEP-DIVE into fluid mechanics. I've waited sooooooooooooooooo long!

Honda Dream solar racers
 

* All three shown would fail, on skin friction, compared to the template. They'd fail on usable interior volume. Center of gravity. Approach, break-over, and departure angles would have to be considered.
* You'll find it structurally impossible to defend your thesis about the template. The fluid mechanics leading to it'd genesis are watertight. Unimpeachable.
* Decades of dimensional analysis were involved in arriving at the template. If you'd had the courtesy to actually read the threads you would have known that long ago. It wasn't the result of some half-baked brain ejaculation as you're fond of burdening us with.
* Go ahead. Pick it apart. Let's see what you're made of.

baloney
 

Baloney to the tune of Cd 0.1201.

advice
 

The template is simply a derivative of everything aerodynamicists implicate for low drag design. It's provided for information. Like a 1.5-radius, street-ell in plumbing or ductwork.
If it's cutting into your credibility as an aerodynamic 'GURU' I make no apologies. It is simply what it is.
There's no way you can logically attack it. Your ad hominem attacks on me won't undermine it's physics. You have no scientific tools at your disposal with which to attack. You're a bad loser. Grow a pair.

A new record. Seven post in 1/2 hour.

weird theory
 

Only to the uneducated would it appear a weird theory. Your extremely qualified as uneducated in the face of data and information,repeatedly thrown at your feet. Graduate and post -Doc level material.
We're casting pearls before swine.

AST- I & II
 

I have seven templates that I use for the dimensional analysis. AST-I I'll use on a Mercedes-Benz GLC, due to it's 'slow' contour.
I'll use the AST-II on the Mercedes-Benz GLC 'Coupe', as it's a 'faster' contour.
Between the seven, one can get a sense of whether the carmaker is following any extant profile. It's all informational.
Both are derived from actual mirror-images of streamline bodies of revolution of L/D = 2.5, which produce Cd 0.04 in free air, and no more than Cd 0.09 as a half-body. The original is from NASA, AVA, and DVL, and is presented in Figure 5.13, page 69 of Hoerner's 'AERODYNAMIC DRAG', which also appears in Hucho's Table 2.1, Page 61, 2nd-Edition.
* Adding wheels gives Cd 0.14.
* Adding the 2.8-degree diffuser yields Cd 0.12.
* Adding the Goro Tamai full wheel fairing package nets lower drag.( Hucho says that Cd 0.09 was achievable as of 1986 ).
-------------------------------------------------------------------------------------
The template is a 'known quantity.' Hucho talks about it all throughout his 2nd Edition. According to him, it's the only path to really low drag. He refers to it as the 'optimum', and in the context of a real passenger car. Again, I'm just the messenger.
I'm just the messenger.