RH Barnard on templates

[freebeard]

Morelli?

[Piotrsko]

After rereading aerohead and looking at freebeard's post, my head hurts.

[seifrob]

Please stop this. Not again
I am neither a moderator responsible for stopping flame wars (like VMan is), nor an esteemed author, who shoud be able to keep cool head in discussion with readers (like Julian), nor an respected member and scientist (like aerohead). Still, I somehow feel a bit responsible over the popularity of the template, too.
So I beg you: stop this.

In your admirable crusade over the the subject you fail to see the context, and occasional posts by newcomers put everything in the flame again.

Let me bring to your attention, that:

1. Aerodynamic Streaming Template is a tool, not A Holy Grail - aerohead in the preface clearly states it is "quick and dirty reference" (here). From what I read (and I read almost entire aerodynamic forum) when making its web version, it was like "If you dont know, where to start, try this, but bear in mind that aerodynamics is so complex that it is possible, that it will not work for you" There are also specific circumstances mentioned together with whole discussion about compromising the shape for daily use. I just do not have a time to dig it.
2. It is 14 years old - while it was quite OK to use it on 1994 Civic, Geo Metro or 1992 F150, which were the ecommodders cars at the time, it is nonsense to use it on Prius, which is the state of the art and basically made its own league in the terms of production cars aerodynamics.
3. YMMW - years ago, almost every reasonable post in the aerodynamic forum ended with this acronyme, which is what I valued. Aeroheads posts about testing aeromods do speak for themselves. I am sure that Julian and other also do put a lot of effort in empiric research, but being on the forum so scarsley, I do not know for sure. It is a pity that we forget to remind newcomers that everything - and aerodynamic assumptions specially - should be taken with grain of salt. Often, in many aero-related discussions you speak apples and oranges. Equally, both parties in the argument can be right from their point of view.

We all can agree, that slide rule has a limited use today, but only foolish man would say it is cumbersome, imprecise and therefore useless, so humanity could evolve without it.

We cannot force anyone to read everything regarding AST to understand its limitations and context (originating VMans post is living example), but for future reference, we coud warn newcomers from taking false assumptions.

I am not a native speaker, so please: Instead of endless pickering can you summarise "The proper disclaimer" we can put in the heading of the AST here?

[Vman455]

***As long as everyone keeps it respectful/no ad hominems or personal attacks, this discussion can continue. Use the "report post" button (which notifies all moderators, not just me) if you feel someone has violated forum rules: No politics. No religion. No ad hominems. Be civil.***

The proper disclaimer is: Stop trying to use a "template" to predict airflow. It's completely arbitrary and doesn't work. No practicing aerodynamicist recommends it. No textbook author recommends it. Hucho didn't even recommend using one when I asked him directly about it, let alone the AST specifically out of all the possible templates one could draw.

1) It has never been able to do any of the things claimed of it - ie:

- guide the best shape of tail extensions
- assess the 'aerodynamic purity' of shapes
- show the height that rear spoilers should rise to
- show where there will be separated and attached flows

2) There is no published evidence in any textbook or paper that supports its use or even suggests it is the best of a variety of low drag shapes.

3) There is no published evidence in any textbook or paper that supports it being overlaid on existing shapes of cars to provide a guide to anything.

4) In Julian Edgar's latest book he specifically debunks the claimed uses of the template (i.e. in 1, above) and not one expert aerodynamicist reviewer of the book disagreed with his points.

5) In short, its use in the way it has been promoted on this site is flawed from start to finish.

6) A few minutes of simple testing in the real world will show that the template doesn't do what it's claimed to do.

Forget trying to paste a template on your car. Get out in the real world. Assess:











Then trial modifications and measure the effects of changes:













You should be trying to get a picture of what happens to the immensely complex airflow over your car after making a change to its shape. Use your brain; figure out what sorts of tests will show you what you want to know; make informed decisions based on real results; leave the speculating and guesswork and 2D line drawings behind. Aerodynamics isn’t magic or illusion, it isn’t paint-by-numbers, and it isn’t simple—but it can be illuminated through straightforward and inexpensive testing.

[freebeard]

How did that one work out?

[freebeard]

After rereading aerohead and looking at freebeard's post, my head hurts.

My theorizing runs to the Morelli shape satisfiys an area rule, and obviates the ground plane/underbody plenum you get with a flat face, that has a lot of shear forces at play.

No politics. No religion. No ad hominems. Be civil.***

Is it Okay to mock Thee Holy Template?

I think it has legitimate utility for blisters and canopies.

[aerohead]

Originally Posted by seifrob

Please stop this. Not again
I am neither a moderator responsible for stopping flame wars (like VMan is), nor an esteemed author, who shoud be able to keep cool head in discussion with readers (like Julian), nor an respected member and scientist (like aerohead). Still, I somehow feel a bit responsible over the popularity of the template, too.
So I beg you: stop this.

In your admirable crusade over the the subject you fail to see the context, and occasional posts by newcomers put everything in the flame again.

Let me bring to your attention, that:

1. Aerodynamic Streaming Template is a tool, not A Holy Grail - aerohead in the preface clearly states it is "quick and dirty reference" (here). From what I read (and I read almost entire aerodynamic forum) when making its web version, it was like "If you dont know, where to start, try this, but bear in mind that aerodynamics is so complex that it is possible, that it will not work for you" There are also specific circumstances mentioned together with whole discussion about compromising the shape for daily use. I just do not have a time to dig it.
2. It is 14 years old - while it was quite OK to use it on 1994 Civic, Geo Metro or 1992 F150, which were the ecommodders cars at the time, it is nonsense to use it on Prius, which is the state of the art and basically made its own league in the terms of production cars aerodynamics.
3. YMMW - years ago, almost every reasonable post in the aerodynamic forum ended with this acronyme, which is what I valued. Aeroheads posts about testing aeromods do speak for themselves. I am sure that Julian and other also do put a lot of effort in empiric research, but being on the forum so scarsley, I do not know for sure. It is a pity that we forget to remind newcomers that everything - and aerodynamic assumptions specially - should be taken with grain of salt. Often, in many aero-related discussions you speak apples and oranges. Equally, both parties in the argument can be right from their point of view.

We all can agree, that slide rule has a limited use today, but only foolish man would say it is cumbersome, imprecise and therefore useless, so humanity could evolve without it.

We cannot force anyone to read everything regarding AST to understand its limitations and context (originating VMans post is living example), but for future reference, we coud warn newcomers from taking false assumptions.

I am not a native speaker, so please: Instead of endless pickering can you summarise "The proper disclaimer" we can put in the heading of the AST here?

I apologize for all 'discomfort' attributed on my account.
The premise of the 'template' was, and remains, a means to economize on time, materials, and cost for anyone considering the body elongation which has been identified as a prerequisite for exceptional drag reduction.
Vman455 appears to be willing to further navigate the physics which undergird the fundamentals behind the 'templates.'
If you can allow us, I promise to keep my contributions limited solely to fluid mechanics, stay out of 'emotional' thought, and maintain civility.
Ecomodder.com isn't my website. If members want to vote me off, I'll 'pack my bags' and you'll never be bothered by me again.

[aerohead]

Please forgive the confusion.
If this thread is still about 'R H Barnard on Templates', we've read what he had to say about his 'ideal cambered version of a half teardrop. slightly flattened on the underside, with optimum geometry being dependent on the ground clearance,'... I was curious as to what he had to say about the 'template(s)', which would only be known to those who frequent the Aerodynamics Forum here at EcoModder.com, and are something uniquely different than what Dr. Barnard addressed in his textbook quote.
Thanks in advance.