Rear Spoilers vs 'template' contour

[jakobnev]

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?

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

[hat_man]

Originally Posted by JulianEdgar

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

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.

[Taylor95]

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.

[freebeard]

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

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.

[JulianEdgar]

Originally Posted by hat_man

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.

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.

[JulianEdgar]

Originally Posted by Taylor95

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.

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.

[hat_man]

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.

[JulianEdgar]

Originally Posted by hat_man

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?

[freebeard]

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


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.

[aerohead]

Originally Posted by JulianEdgar

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

Tesla Model S not obeying the template:






Jaguar XE not obeying the template:





(Colder colour = high pressure):




Honda Insight not obeying the template:







Honda Legend not obeying the template:






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:






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

*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.