10% = 5%

[JulianEdgar]

Originally Posted by RedDevil

My point is that a difference in opinion can be a great starting point for further learning. If we keep things civil of course.

Absolutely. But all that falls down if someone - in this case Aerohead - refuses to change what they write here, irrespective of all the evidence against it.

In some cases, we're talking about absolute and completely obvious errors (eg how Reynolds numbers are calculated).

So the forum moves from learning about what is correct and incorrect - to learning in your words "anything I read on aerodynamics as opinion".

That's just crazy: facts are facts.

Reynolds Numbers (to continue the example) are not calculated using area (as Aerohead has stated). That's not my opinion; that's a fact. Look in any aero textbook to see for yourself.

The template does not show where there is attached and separated flow when it is overlaid on car profiles (as Aerohead has stated). That's not my opinion; that's a fact. Tuft test a car and find out for yourself.

A 10% reduction in aero drag does not automatically give a 5% reduction in fuel consumed (as Aerohead has stated). That's not my opinion; that's a fact. Look in any aero textbook to see for yourself.

I am just amazed that so many people here would rather have a happy forum full of incorrect information rather than challenge the massive amount of misinformation that keeps getting promoted.

We're not talking subtleties in aerodynamic understanding and application - we're talking about completely wrong information! And nearly all of it comes back to one source - what Aerohead posts here.

[freebeard]

It wasn't intentional: 'Arrowhead' is what my spell check changes Aerohead to! Usually I pick it up and change it, but obviously in this case I missed it.

Does it also gratutiously capitalize it as well, irrespective of all the evidence against it?

10% reduction in aero drag does not automatically give a 5% reduction in fuel consumed (as Aerohead has stated). That's not my opinion; that's a...

...zeroth-order approximation.

[JulianEdgar]

Originally Posted by freebeard

Does it also gratutiously capitalize it as well, irrespective of all the evidence against it?


...zeroth-order approximation.

We've had this discussion before. I capitalise proper nouns, as is conventional in normal written English. A name (handle, whatever) is a proper noun, so I capitalise it. There's nothing more to it than that.

[RedDevil]

Aerohead did not imply that a 10% reduction in aero drag gives a 5% reduction in fuel consumption in all circumstances. He just refers to one specific case where the ratio was like that, without taking it any broader. If you think he did that's your warped vision of reality.

And it is like that every time. You seem hell bent on burning him into the ground.
When you believe you are in the right you give no quarter. This kills all meaningful conversation. That the accusations are often not or not fully justified makes it all the worse.

Then I find it hard to check your claims. You throw the book at it every time. Sorry but that does not cut it for me. Most people won't have the book or the time to delve into it. Should they then accept what you say without further explanation?
The real challenge is not to make claims, but to explain them in accessible terms. Which, I feel, Aerohead does way better than you do.

But the bickering, the insults! Why do you keep doing that? That conduct kills forums. It kills clubs, it kills choirs (my wife's choir just ended a month ago due to similar infighting), it ruins everything.
You have been banned temporarily here. You've been banned on InsightCentral for similar conduct.
Will you ever change before you are forced to leave?

Oh, I'm crazy and this is a happy forum full of misinformation. Now I'm convinced!

[JulianEdgar]

Originally Posted by RedDevil

Aerohead did not imply that a 10% reduction in aero drag gives a 5% reduction in fuel consumption in all circumstances. He just refers to one specific case where the ratio was like that, without taking it any broader. If you think he did that's your warped vision of reality.

And it is like that every time. You seem hell bent on burning him into the ground.
When you believe you are in the right you give no quarter. This kills all meaningful conversation.

Then I find it hard to check your claims. You throw the book at it every time. Sorry but that does not cut it for me. Most people won't have the book or the time to delve into it. Should they then accept what you say without further explanation?
The real challenge is not to make claims, but to explain them in accessible terms. Which, I feel, Aerohead does way better than you do.

But the bickering, the insults! Why do you keep doing that? That conduct kills forums. It kills clubs, it kills choirs (my wife's choir just ended a month ago due to similar infighting), it ruins everything.
You have been banned temporarily here. You've been banned on InsightCentral for similar conduct.
Will you ever change before you are forced to leave?

Oh, I'm crazy and this is a happy forum full of misinformation. Now I'm convinced!

Aerohead has often in the past equated a 10 per cent reduction in drag with a 5 per cent reduction in fuel consumption. There are no qualifications in the title of the thread - he's simply pushing the old barrow.

If you're not prepared to find out information for yourself, and you're not prepared to believe me, well you're going to end up with some major misconceptions about car aerodynamics.

When I say: "Don't believe me - find out for yourself" that's apparently not OK? At least some people here have taken me at my word, and looked at some books and done some testing - and of course have quickly found the depth of misinformation being disseminated here.

And I love it how you suggest I am "making claims"!

I mean, what a claim it is to state that (for example) Reynolds Numbers aren't calculated using area! That's a bit like making the "claim" that Force = mass * acceleration. For most people, that's a fact.

[RedDevil]

Originally Posted by JulianEdgar

It wasn't intentional: 'Arrowhead' is what my spell check changes Aerohead to! Usually I pick it up and change it, but obviously in this case I missed it.

Fair enough. Thanks for pointing it out.

[RedDevil]

Originally Posted by JulianEdgar

Aerohead has often in the past equated a 10 per cent reduction in drag with a 5 per cent reduction in fuel consumption. There are no qualifications in the title of the thread - he's simply pushing the old barrow.

If you're not prepared to find out information for yourself, and you're not prepared to believe me, well you're going to end up with some major misconceptions about car aerodynamics.

When I say: "Don't believe me - find out for yourself" that's apparently not OK? At least some people here have taken me at my word, and looked at some books and done some testing - and of course have quickly found the depth of misinformation being disseminated here.

And I love it how you suggest I am "making claims"!

I mean, what a claim it is to state that (for example) Reynolds Numbers aren't calculated using area! That's a bit like making the "claim" that Force = mass * acceleration. For most people, that's a fact.

I feel Aerohead put it in the banner like that because it is such a dead-beat horse. The fact that roughly about half the fuel consumption at highway speeds is due to aerodynamic drag is something that often comes up in explanations of car aerodynamics to the general public. Nobody on this site believes that the 10%-5% ratio is a precise and immutable truth for all cars in all conditions.

Please bear in mind that I indeed cannot evaluate or fact check everything.
Many things that are factual to you evade my knowledge or insight.
What should I do with that? Just accept all for true just because you say so? I still would not understand it. What have I learned then?

But I'm glad we can at last discuss it in a cordial way. I hope it will continue like this.

[freebeard]

There's nothing more to it than that.

e.e.cummoings looks down disapprovingly. Be glad your not a programmer. They have to deal in truth, not grade-school English. There is no rule about names that doesn't have an exception somewhere in the World.

Shouldn't you at least fall back to proper names. Proper nouns would include marks like eBay and iTunes.

We've had this discussion before.

And as usual, you avoid the point of the post, in this case 'zeroth approximation'. Did you look at the link?

[ME_Andy]

Originally Posted by JulianEdgar

In this thread, where are others questioning Arrowhead's "10%=5%" rule?

It's not Aerohead's rule, it's a GM engineer's rule.

Personally, I've come around to believing you know a thing or two and I'm happy to have you post here. I just want you to take a chill pill beforehand.

[JulianEdgar]

Originally Posted by freebeard

And as usual, you avoid the point of the post, in this case 'zeroth approximation'. Did you look at the link?

Yes I did. I couldn't then be bothered trying to work out the obscure message.