Decimal places

[JulianEdgar]

Originally Posted by Piotrsko

I'm going sociology here: more than 2 places past the decimal is meaningless (mostly because you cant half a person and expect meaningful results)

I doubt that the homebuilt state of the art can actually measure to that accuracy without compensation or under closed controlled atmospheres. Go ahead and prove me wrong with actual data and not massaged findings.

No I think that is right. I can’t think of any aero measurements at all that can be measured to that degree of accuracy on the road.

[skyking]

When you are typing in your results it is common to do .37 for example. I think most of the excess in figures comes from copy pasta. It is a tasty but redundant dish.

[Isaac Zachary]

I agree 99.99999999999999999999999999999999999999999999999 99999999999999999999999999999999999999999999999999 99999999999999999999999999999999999999999999999999 999%

When I do my own measurements I write it down to the most decimals I can on my own personal piece of paper. (e.g. 4.7823, 4.2901, 4.9563) But then I usually realize that the fluctuations in my measurements are so big that there's no way I'm even close to precise. So I prefer something a little more generalized (e.g. ~4.6).

I wonder where I could get my seat-o-pants meter properly calibrated.

[Piotrsko]

Suprisingly they come calibrated directly from the factory, but the calibration standards are different for each model.

[aerohead]

An article about the Cd 0.31 FIAT 500e in Motor Trend, mentioned that, compared to the FIAT 500 Pop, the 500e had 6.3% lower drag.
In order to 'solve' for the 500 Pop drag coefficient ( not provided ), required running out to six -decimal places to achieve a 6.3% fit.

[JulianEdgar]

Originally Posted by aerohead

An article about the Cd 0.31 FIAT 500e in Motor Trend, mentioned that, compared to the FIAT 500 Pop, the 500e had 6.3% lower drag.
In order to 'solve' for the 500 Pop drag coefficient ( not provided ), required running out to six -decimal places to achieve a 6.3% fit.

Only if the 6.3 per cent weren't a rounded number, as obviously it was.

If you think that any wind tunnel is working to 6 decimal places, you know very little about wind tunnels (or maybe decimal places?).

[aerohead]

Originally Posted by JulianEdgar

Only if the 6.3 per cent weren't a rounded number, as obviously it was.

If you think that any wind tunnel is working to 6 decimal places, you know very little about wind tunnels (or maybe decimal places?).

It's not obvious to me at all. I have no way to vet what Motor Trend publishes, one way or another.
I've said nothing about wind tunnel working numbers.
I simply stated that, in order to satisfy 6.3% higher drag than the value which was provided, required 6-decimal place accuracy.
Do you want this thread turned off also? When I tell you what I think about your knowledge of wind tunnels?
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PS Thanks for page-17, # 162 permalink.
After 28-days, 17-pages, and 161 permalinks worth of grief, we finally manage to get what ought to have been in the preamble to your first permalink, on March 22.
The talking comes first, then the thinking.

[JulianEdgar]

Originally Posted by aerohead

It's not obvious to me at all. I have no way to vet what Motor Trend publishes, one way or another.
I've said nothing about wind tunnel working numbers.
I simply stated that, in order to satisfy 6.3% higher drag than the value which was provided, required 6-decimal place accuracy.
Do you want this thread turned off also? When I tell you what I think about your knowledge of wind tunnels?

Well, we can now add that you don't know much about car magazines, too! Motor Trend would simply have been quoting Fiat, and Fiat would have provided the 6.3 per cent as a rounded number.

To even try to pretend that the figure was exactly 6.3 per cent, and therefore solving for the Cd of the 500 pop requires calculations to 6 decimal places, is typical of the sort of mental knots you tie yourself in when trying to prove your point. It's pretty sad.

[aerohead]

Originally Posted by JulianEdgar

Well, we can now add that you don't know much about car magazines, too! Motor Trend would simply have been quoting Fiat, and Fiat would have provided the 6.3 per cent as a rounded number.

To even try to pretend that the figure was exactly 6.3 per cent, and therefore solving for the Cd of the 500 pop requires calculations to 6 decimal places, is typical of the sort of mental knots you tie yourself in when trying to prove your point. It's pretty sad.

And now your psychic powers have discerned that 6.3% is a FIAT rounded number. Certainly you have an SAE Paper which clearly certifies the truth of the matter.
Don Sherman was courteous enough to tell us that he 'rounded' his Drag Queens data. Pretty rare.
Perhaps you'd like to rewrite all written correspondence in your superior hand. Thanks in advance!
Those who perhaps, have access to only the popular press, will also have only the values these sources provide in attempting to navigate aerodynamics.
Working with default levels of accuracy, derived from this literature might offend only those who've never attempted the voyage.
Please limit criticism to constructive criticism.

[JulianEdgar]

Originally Posted by aerohead

And now your psychic powers have discerned that 6.3% is a FIAT rounded number.

Um, to you it might need psychic powers. To everyone else it's pretty obvious that the change in drag wasn't 6.300000%.