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Old 05-13-2020, 11:57 AM   #18 (permalink)
aerohead
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wrong

Quote:
Originally Posted by JulianEdgar View Post
I am sorry, but this is your typical dump of misinformation, misunderstandings and plain outright wrong statements - as usual, dressed up in pseudo-scientific language.




Well, perhaps read a bit more widely and recently than Hucho, second edition?

You say you have my book. Well then, read pages 179 - 182. Note specifically the reference to SAE 1999-01-0651 that shows how even small amounts of lift adversely impact stability, and to SAE papers 2009-01-004 and SAE 2015-01-1537 that again show how even small amounts of lift (especially rear lift) adversely affect car handling and stability.

But reading and driving are different things. I drive a car that, because of its modifications, develops downforce. It is easily measurable at 100 km/h. The car is significantly improved in its driving behaviour - eg cornering speed. In addition, it actually rides better because the sprung/unsprung weight ratio has effectively changed.

I might have believed what you say before I did the research for my book, and experienced the benefits of reduced lift for myself.




I am sorry, but this is just rubbish. (1) The lift being described is nothing to do with separated flow. (2) Squarebacks can create lift. As Barnard specifically says in his book, even a brick can develop lift. Fastbacks are notorious for lift. (3) Notchbacks are not historically the worse offenders, and of course as most people know, the first spoiler was fitted to the classic Porsche 911 in 1973 (page 195 of my book). The 911 was a high lift shape, just as you'd expect with that long upper body curve.




I am sorry, but this is all just rubbish. Have you ever measured pressures on a car? Obviously not! There is attached flow on these cars (eg Cayenne) to the trailing edge of the roof - the roof is not exposed to turbulence. There are plenty of wind tunnel videos around of the latest Cayenne, showing just this. In fact, the idea that the flow separates on the roof of these cars is just laughable.

I can see now why some of the misinformation is spread here: it appears that you just make up theories, completely without evidence, and then happily apply them!
I'm just attempting to compensate,for the sake of lurkers,your misinformation,misunderstandings, and plain outright wrong statements.I don't mean to jeopardize your book sales,and self-created reputation as an authority on automotive aerodynamics.
Donald Rumsfeld has said:'There are known-knowns,known-unknowns,and unknown-unknowns.'
Sometimes your comments suggest that you're attempting to punch above your weight class.
I believe that you mean well,and I applaud your efforts to educate.
I don't believe that you have as good a grip on physics as you might presume.I'm pretty certain that you don't understand lift.I'm absolutely certain that you do not understand the implications of flow separation as associated with local pressure,along with their location on the body,as pertains to lift.You keep repeating the same fallacy every time you mention lift.
*Perhaps Barnard isn't the sharpest knife in the drawer.There is counterfactual evidence to his claims to be considered. Did you?
*The rear spoiler on the 911 does not function for the reasons you submit.You can compare the 911's aft-body downslope contour with the 2020 Taycan,and then tell us why the Taycan can drive safely at 160-mph without a rear spoiler.
*All your comments about the performance of your Insight modifications are subjective. Accelerometer data would put some numbers with your testimony.3rd-party testing is always appreciated.I own the 2000,5-spd Insight.I'm okay with the way it performs in stock form.A boat-tail helps.We have an associate registering in the 80-mpg range by utilizing this mid-1930s FKFS technology.
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