[JulianEdgar]

Originally Posted by aerohead

* I was addressing the ability of a decklid spoiler to slow the air down and increase pressure.
* Anything that spoils lift is a 'spoiler'. Wings included.
* I'm in disagreement with your broad-brush assertion that, with modern cars, that 'most lift comes from attached flow.'
*It's my opinion that, caveats/ conditions need to be spelled out.
* If you have an industry-wide statistical analysis which demonstrates that for the entire vehicle population, that causality of lift is directly associated with a statistically significant proportion of vehicles, only then could one make such an argument.
* And just for the benefit of the reader, allow that there are exceptions to your general claim.

The discussion was about roof spoilers, so as usual, Aerohead's post (which as about boot spoilers) just sows confusion.

A wing is not a spoiler, and a spoiler is not a wing, in any technical automotive use of the words. I am glad Aerohead reiterates his misconception so that can be no confusion in the minds of people reading this that his mistake was just a typo.

I am quite happy to stand by my point that most lift on modern cars comes from attached flow. Just look at any CFD image or wool tuft / pressure testing of any modern car shape. There are plenty around to look at!

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* If you're only testing vehicles possessing contour-compromised roofline profiles, which violate the ' ground rules of fluid mechanics' as Hucho refers to them, all your data will suggest that presumed attached flow is responsible for lift. An inescapable intellectual cul -de -sac.
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So far we have discovered that, according to Aerohead, wool tuft testing cannot be trusted, smoke testing doesn't show what it is supposed to - and now, pressure testing is invalid as well. No doubt subsequently we will get to the invalidity of measuring overall lift. Most people would find it pretty hard to maintain a theory when all the quantitative evidence is against it, but not Aerohead.

* Wing sections are not streamline bodies, in the strict sense of the term. Wings operate in two-dimensional flow. As mentioned elsewhere, every wing profile has an angle-of-attack at which zero-lift is achieved. In the back of their book, Abbott and Von Doenhoff provided tables for all extant wing profiles, and the tables provide dedicated columns just for the zero-lift data.

I am glad Aerohead reiterates his misconception that a wing is not streamlined; then there can be no confusion in the minds of people reading this that his mistake was just a typo. As I have previously said, Aerohead has his own definition of 'streamlined' - one that doesn't match any normal technical automotive use.

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* 'Streamline bodies' denote 'streamline bodies of revolution', and for automotive application, ' half-bodies of revolution.' This is technical language specific to road vehicle aerodynamics.
* The 'aerodynamic streamlining template' is based upon a half-body, derived from a streamline body of Cd 0.04, the drag minimum known, for a body of which the aft-body contraction contour does not exceed 22-degrees as measured off a horizontal projection.
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So Aerohead has said before. But, with respect, so what? It's his theoretical hobbyhorse, but it is one that is basically ignored (1 -2 pages max in a whole book, if that) by all the current major authoritative texts on automotive aerodynamics. Why do they ignore it? Because it's of such little significance.

Not everyone excels at technical writing.

Aerohead is certainly right about that.