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JulianEdgar · 05-15-2020, 04:34 AM

We now seemed to have progressed(?) to rationalising incorrect statements as better than nothing.

I am sorry; I don't agree.

Rules of thumb that aren't stated with qualifiers but instead as absolutes, are deceptive. It's pretty odd that people then turn around and say "But I am sure most people realise that they're not absolutes". Why not just say that at the time? It's not hard:

Very approximately (it depends on the car, engine and other factors), at 55 mph, a 10% drag reduction translates to a 5% increase in fuel economy. At 70mph,a 10% drag reduction translates into a 4% increase.

There we are, a useful rule of thumb that won't lead anyone astray.

A template that is presented as the absolute best approach, when there's very little evidence that it actually is, and the shape isn't even mentioned (as far as I am aware) in any current aerodynamic technical literature, is deceptive. That is, when it is presented without a great deal of qualification.

When I started reading this site I was surprised by:

(1) The way pat numbers were thrown around as if, of course, just following these will give you the best results. (Then I realised most of that information seemed to be coming from one source.)

(2) The complete ignoring of vertical aerodynamic forces, as if lift (and induced drag) didn't exist. (Then I realised most of the misinformation on that topic was coming from one source.)

Someone said that I should expect my statements to be scrutinised. Well, fine. If it's something theoretical, let's compare references, with obviously greater weighting given to most recent research. If it's something practical, let's compare on-road test results.

I only take exception to criticism when it's from a keyboard warrior - someone who hasn't actually done what I am describing, but just knows I am wrong (eg in my test results)... without their presenting any evidence to support their statements whatsoever. (That is, it's all just what they think.)

As I have said, the content of my book was vetted by four top automotive aerodynamicists. I am pretty confident that a lot (but certainly not all) of the advice on this forum would never have made it past them.

I just want accurate, useful and effective advice being given to those who wish to modify the aerodynamics of their cars!

And, in my opinion, bad advice is worse than no advice.

05-15-2020, 04:34 AM	#58 (permalink)
JulianEdgar Banned Join Date: Nov 2017 Location: Australia Posts: 2,060 Thanks: 107 Thanked 1,605 Times in 1,136 Posts	We now seemed to have progressed(?) to rationalising incorrect statements as better than nothing. I am sorry; I don't agree. Rules of thumb that aren't stated with qualifiers but instead as absolutes, are deceptive. It's pretty odd that people then turn around and say "But I am sure most people realise that they're not absolutes". Why not just say that at the time? It's not hard: Very approximately (it depends on the car, engine and other factors), at 55 mph, a 10% drag reduction translates to a 5% increase in fuel economy. At 70mph,a 10% drag reduction translates into a 4% increase. There we are, a useful rule of thumb that won't lead anyone astray. A template that is presented as the absolute best approach, when there's very little evidence that it actually is, and the shape isn't even mentioned (as far as I am aware) in any current aerodynamic technical literature, is deceptive. That is, when it is presented without a great deal of qualification. When I started reading this site I was surprised by: (1) The way pat numbers were thrown around as if, of course, just following these will give you the best results. (Then I realised most of that information seemed to be coming from one source.) (2) The complete ignoring of vertical aerodynamic forces, as if lift (and induced drag) didn't exist. (Then I realised most of the misinformation on that topic was coming from one source.) Someone said that I should expect my statements to be scrutinised. Well, fine. If it's something theoretical, let's compare references, with obviously greater weighting given to most recent research. If it's something practical, let's compare on-road test results. I only take exception to criticism when it's from a keyboard warrior - someone who hasn't actually done what I am describing, but just knows I am wrong (eg in my test results)... without their presenting any evidence to support their statements whatsoever. (That is, it's all just what they think.) As I have said, the content of my book was vetted by four top automotive aerodynamicists. I am pretty confident that a lot (but certainly not all) of the advice on this forum would never have made it past them. I just want accurate, useful and effective advice being given to those who wish to modify the aerodynamics of their cars! And, in my opinion, bad advice is worse than no advice.