Want low drag? Don't follow a template.

[JulianEdgar]

Originally Posted by ME_Andy

I guess we have very different opinions on the meaning of "rubbish" and "approximation".

Yet again you didn’t address my specific criticisms of how the template is used here.

[JulianEdgar]

Originally Posted by freebeard

I agreed with you at permalink #18.

Yes I noticed you agreed, but on the basis of your past posts, I don’t expect that you will make that clear at the time the misinformation actually is being disseminated.

I think your aggrieved 'come at me bro' attitude is tiring. But.... The forum is pretty much dead except for this 'controversy' and The Lounge, so....

[shrug]

People who have the equivalent (non) argument of “I don’t like you so please be quiet” is one reason misinformation has flourished here.

[ME_Andy]

I've already acknowledged that the template isn't a perfect tool. That holds for all four of your bullet points.

Clearly it is a useful tool that provides a good approximation.

[JulianEdgar]

Originally Posted by ME_Andy

I've already acknowledged that the template isn't a perfect tool. That holds for all four of your bullet points.

Clearly it is a useful tool that provides a good approximation.

I know you're trying to be conciliatory, but unfortunately the template doesn't even hold for that.

Viz:

It is claimed to allow you to:

- Show where there is separated and attached flow on existing cars

This is very much yes/no - is the flow attached or separated? The template definitely does not show this on cars.

- Guide the shape of rear extensions

Absolutely not. The best shape rear extension will depend on a whole lot of factors, and following a preset template is no guide at all to gaining the best outcome.

- Show how rear spoilers on sedans should be positioned and shaped

Completely wrong. This confusion shown by Aerohead when describing how rear spoilers work is based on his belief in the template (and how rear spoilers worked on old cars), and following that advice will give terrible outcomes on any modern sedan.

- Allow the assessment of the ‘aerodynamic purity’ of cars

The idea that, if only car makers followed the template they would get so much better results, is complete rubbish. Therefore, overlaying a car and 'measuring it' against the template (to purportedly see how good the car is) is equal baloney. After all, why not pick one of the other five low drag shapes with which to do the comparison?

The template is just one of a bunch of different, low drag, theoretical shapes. If it were presented as that, then that would be quite correct, and I'd have no issues.

I don't know, maybe it started off like that - but it's certainly gone into crazy land since!

[freebeard]

Yes I noticed you agreed, but on the basis of your past posts, I don’t expect that you will make that clear at the time the misinformation actually is being disseminated.

Not my battle. I gave up on criticizing the default template long ago. I've even slacked off on protesting passive-aggressive capitalizations.

People who have the equivalent (non) argument of “I don’t like you so please be quiet” is one reason misinformation has flourished here.

Well, a pox on those people. I like your cranky self and I say Rave On. I think I prefer your work on Youtube.

[JulianEdgar]

Originally Posted by freebeard

Not my battle. I gave up on criticizing the default template long ago.

But don't you then feel guilty when you see people clearly going in the wrong direction when they follow the crap advice? People genuinely confused when their measurements / observations / thoughts don't at all match the template - and all the guff that has been extrapolated from it. (The latter is the important part.)

I worked 8 years as a school teacher, another 8 as an adult trainer, and been modifying cars (and writing about it) for 35+ years. And I hate people being given the wrong information.

But that doesn't mean that there is not room for disagreement. For example, Vman455 and I disagree on the purpose/presence of vestigial front spoilers on modern cars - but I think it's a literally debatable point.

On this sub-forum people are talking information that is so often wrong it's gobsmacking. I can even read individual participant's posts and immediately recognise where their aero misapprehensions have come from - because those misapprehensions are here and nowhere else. (In other words, this sub forum has developed a whole bunch of uniquely wrong 'understandings' of car aero.)

I know some people who have posted here know far better, but either they can't be bothered posting corrections (especially when they'll be met with a wall of pseudo-tech BS from someone who apparently believes they're always right) or the peer pressure 'to be nice' keeps them quiet. (Obviously that's not me!)

Unfortunately I cannot see any change unless people start to do some decent on-road testing (throttle-stop, tufting, pressure measurement), read current aero textbooks or step out of the 'cult' (as someone described Ecomodder to me) frame of reference.

None of these actions takes much money, but they all require an effort.

[freebeard]

But don't you then feel guilty when you see people clearly going in the wrong direction when they follow the crap advice? People genuinely confused when their measurements / observations / thoughts don't at all match the template - and all the guff that has been extrapolated from it. (The latter is the important part.)

..... And I hate people being given the wrong information.

No I don't feel guilty for others misapprehensions. I have more concern for the legacy media in my country trying to steer it's politics into the ditch.

I see Template Worship as one [misguided?] theme, alongside A-B-A testing, hypermiling and a number of others. Frankly, since I don't drive much anymore, I'm in it for the friendly persuasion in The Lounge.

[Vman455]

Originally Posted by ME_Andy

2:10 : you're right, the template doesn't predict where the flow detaches to a high degree of accuracy. It's maybe 20cm off or so. Big whoop. Nobody claimed the template was perfect, it's an approximation. The original description even says, it should be useful for amateurs.

The "template" has been used here for more than decade now to predict flow separation. Take a look at this thread about the 2010 Prius; in it, a bunch of posters theorize about flow detachment on the roof and rear window based on comparison to the "template". And not a one bothered to go out, tape some tufts to the car, drive it and look at them. Instead, they predicted flow separation (where, incidentally, none exists--which I know because I went out, taped some tufts to my Prius, drove it, and looked at them).

For a more recent example, look at the Honda CR-Z build thread. In that one, a poster writes about his efforts to obtain a high-resolution profile photo so he can "analyze" the car aerodynamically--presumably by comparison to the "template" (as if it is possible to "analyze" a car aerodynamically simply by looking at a picture of it).

***
I don't understand the pushback here. Whenever Julian has recommended a book, I've bought and read it. I bought the (inexpensive) testing equipment he has posted about. I've started measuring things myself; I don't have to take his word or any author's word for it. I've learned a great deal in the process, but most of all it has opened up a whole world of what I don't know.

What are you all afraid of? Are you afraid your previous beliefs about aerodynamics will have to be rethought? Do you think you'll "regret" learning something new, as someone threatened in another thread (under different circumstances, but the sentiment is what I'm getting at)? Or is it just that the idea that the field of vehicle aerodynamics is actually simple (an idea which appears to be so far from the truth as to be laughable), which has been promulgated on this site for more than a decade, is now so entrenched that you all truly believe it and no contrary evidence will be tolerated let alone investigated? What is it?

[CigaR007]

Originally Posted by Vman455

For a more recent example, look at the Honda CR-Z build thread. In that one, a poster writes about his efforts to obtain a high-resolution profile photo so he can "analyze" the car aerodynamically--presumably by comparison to the "template" (as if it is possible to "analyze" a car aerodynamically simply by looking at a picture of it).

...and what is wrong with that ? He is doing the analysis on his own time, based on actual tuft-testing and body shape observations. If a relation can be established between the template and the observed air flow, I would consider that as added value. if it does not, then so be it. We move on. No drama.

Ironically, aerohead is one of the few people who actually took the time, his time, to provide some feedback in my build thread; yet people have the audacity to criticize him ? Where are the other viewpoints ? oh wait... they are too busy denigrating.

aerohead is not selling anything. Mr Edgar is. Keep that in mind.

[freebeard]

Ironically, aerohead is one of the few people who actually took the time, his time, to provide some feedback in my build thread; yet people have the audacity to criticize him ? Where are the other viewpoints ? oh wait... they are too busy denigrating.

Further to the point, he [over]built the Baby Template and hauled it interstate to the best wind tunnel available at the time.

aerohead is not selling anything. Mr Edgar is. Keep that in mind.

Yikes!