The Fastback bloc

[JulianEdgar]

And it's not a fastback, but to show how utterly BS 'The Template' is, here's a sedan.



So of course airflow would separate at the end of the roof and remain separated all across the boot lid, no? And to gain flow re-attachment, you'd need a spoiler that 'reached up' to the template line, no?

Except, of course, that theory is simply rubbish.



Note the clearly attached flow down most of the window and on the trailing edge of the boot lid...

[JulianEdgar]

So, if you do almost no real-world testing, and rely on theory and shapes largely derived from the 1930s, it's possible to develop a very odd idea of what is actually going on.

Then, if your first premise is utterly wrong, you are potentially in a position where you build upon that faulty foundation and come up with a second premise, that is equally wrong. And so on...

First faulty premise: if the shape curves downwards faster than The Template, flow separation will occur.

Second faulty premise: if the shape curves downwards faster than The Template, flow separation will occur and therefore low pressures - and so lift - are due to separation.

Then, if you are completely seduced by your weird theory, you can extrapolate it into absurdities - a third faulty premise.

Third faulty premise: rear spoilers reduce lift by 'reaching up' to the streamline that would have occurred had 'The Template shape premise' (ie Premise 1) been true.

(To be fair, the third faulty premise is faulty only on cars with attached flow. Where separation occurred at the end of (say) the roof on a sedan of the 1960s, this was a valid idea [just not with The Template as the demarcator] and certainly not with cars of the last 30-odd years.)

The we add to the mix:

• a believer in these faulty premises who sometimes writes in an incomprehensible (but impressive-sounding) pseudo-technical English
  
  
• a largely uncritical audience that doesn't know much at all about the subject (sorry, guys)
  
  
• something I have noticed that dominates discussion groups with largely US contributors, and that is a really strong peer pressure to not call out rubbish being spouted by others (it's apparently seen as being rude)

.... and so we end up having completely invalid notions being accepted, regurgitated and defended.

One of my undergraduate majors was sociology. I sometimes think I should do a doctoral dissertation on hobby-technical BS spread by discussion groups...

[kach22i]

Originally Posted by freebeard

Another counterexample is the GM EV1. It has a too-fast fastback and too-good numbers.

I have posted that car more than once. May have been told yes it works but works even better following the template. However final wind tunnel testing trumps any theory. End of what I recall being told.

Back in 2013 when the "Scaling the Template" thread was active I believe Aerohead provided the explanation that the Aerotemplate was a starting point and not a final destination.

https://ecomodder.com/forum/showthre...ate-25975.html

Also he gave great leeway to wind tunnel testing for final results over that of concept, theory and template use.

I was never 100 percent happy with "follow this template strictly until wind tunnel proves otherwise" approach because I do not have a wind tunnel and still wanted explanation for real world departures from the aero-template.

Julian is offering an explanation (air pressure) to go with a process. This is an exciting thing to explore, but as usual I am reluctant to be a cult follower, even if it's a really cool cult that makes sense on the surface.

However, both Aerohead/Phil and Julian seem willing to surrender to testing results to justify and critique actual designs.

This common ground is where we can agree, and yet disagree on how it became so and how it works or does not work.

Going back to 2010-2013, I think that I was told the ground pressure plane skews attachment from those of free air shapes found in the sky (aircraft). Resulting in longer bodies (longer slopes) near the ground than in free flowing air or body moving in free air to be more exact.

Another thing said over and over again in this forum over the years is that tuft attachment does NOT always mean good low drag airflow above. The many reasons why have seemed reasonable to me when patiently explained by Phil/Aerohead and others.

Post #42 - hot topic indeed.
https://ecomodder.com/forum/showthre...y-25809-5.html

Post #45 one of my better things said.

When you scale down the template, you scale down your success.

[freebeard]

Great news, everyone!

Poking around in that old thread I found, downed, and re-upped the picture of the Vanagon that was lost to Photobucket's [expletive deleted]. I renamed it 'boat tail box cavity'.



Notice the solid floor. This informed my design for a retractable boat tail for the Type II.



I got sidetracked. I was looking for a picture of Morelli's Urban Car. Before EcoModder I thought the most aerodynamic termination was a 45° chamfer, like the Urban car. (I'm thinking of the profile drawing with the wake in yellow) I'd hope it would be in this massive data dump from 2016: Body plan taper and drag. But I did find this. I find Mair more helpful than The Template.



Has Photobucket un-borked itself?

[kach22i]

Originally Posted by freebeard

......from 2016: Body plan taper and drag.

Great link, guess I have not seen that one before.

Has anyone superimposed the Mair's tail with the Aerodynamic Streamlining Template Part-C?

Yes, Photobucket seems to have removed the cork from it's butt.

Hurray!

[JulianEdgar]

Originally Posted by kach22i

However, both Aerohead/Phil and Julian seem willing to surrender to testing results to justify and critique actual designs.

I don't know how you get to that - Aerohead has repeatedly stated that his theories are correct in the face of contrary test results.

I emphasise: repeatedly.

[JulianEdgar]

Originally Posted by freebeard

I got sidetracked. I was looking for a picture of Morelli's Urban Car. Before EcoModder I thought the most aerodynamic termination was a 45° chamfer, like the Urban car. (I'm thinking of the profile drawing with the wake in yellow) I'd hope it would be in this massive data dump from 2016: Body plan taper and drag. But I did find this. I find Mair more helpful than The Template.



Has Photobucket un-borked itself?

I am pretty amazed that you are now nominating another template for rear add-ons. This is just continuing the problem!

The whole idea of a templated shape for add-ons is flawed - at minimum, flow attachment will depend on the thickness of the boundary layer, which depends on what is happening ahead of the template extension.

[freebeard]

Originally Posted by kach22i

Has anyone superimposed the Mair's tail with the Aerodynamic Streamlining Template Part-C?

My recollection is that the blunt nose and rear taper from Mair, minus the constant-section center approximates [one instance of] Thee Holy Template.

I don't know how you get to that - Aerohead has repeatedly stated that his theories are correct in the face of contrary test results.

I've met with aerohead on The Salt and at Darko.

I am pretty amazed that you are now nominating another template for rear add-ons. This is just continuing the problem!

On Internet it is customary to post a wrong answer. That how you find out the right one. I documentated the pushback against the Template that was available before you started posting.

My intent really was to draw out the Morelli design that was all forebody with max camber at the C-pillar and a 45° chamfer instead of a wickerbill.

The closest I can find is this [Honda?] concept:

[JulianEdgar]

Originally Posted by freebeard

On Internet it is customary to post a wrong answer. That how you find out the right one.

If you're serious, that's about the dumbest thing I have recently read. Sow confusion and mislead people - and that's somehow good?

[freebeard]

Well, thanks for correcting me, but it isn't just a good idea, it's Cunninghams Law.

Cunningham's Law states "the best way to get the right answer on the internet is not to ask a question; it's to post the wrong answer."

The concept is named after Ward Cunningham, father of the wiki. According to Steven McGeady,[1] the law's author, Wikipedia may be the most well-known demonstration of this law.[2]

Cunningham's Law can be considered the Internet equivalent of the French saying "prêcher le faux pour savoir le vrai" (preach the falsehood to know the truth). Sherlock Holmes has been known to use the principle at times (for example, in The Sign of the Four.[3]) In "Duty Calls," xkcd references a similar concept.[4]

https://xkcd.com/386/