[JulianEdgar]

Originally Posted by aerohead

1) on the Insight, the trailing edge of the backlight is 24.5mm below the AST-II profile. Okay according to Buchheim et al.. No argument from me. Check!
2) so your measurements reflect those of a 'streamlined' roofline. Check!
3) whether or not each discrete resultant possesses a horizontal component will be reflected in the coefficient of drag.
4) the lion's share of drag will be determined between forward and rear stagnation point.
5) if the body is to be three-dimensional, capable of containing occupants, we must live with the consequences of resultants.
6) the final analysis is Cd.
7) if the Insight is capable of Cd 0.09, and it's Cd 0.25, then, by definition, the Insight has Cd 0.16 designed in.
8) this is what I've been interested in since 1973.
9) this is why I went to college.
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10) and then the big, ugly question rears its head. Even if we make all these measurements, what in the world do we do with them, which gets us to Cd 0.09?
11) Hucho told us in 1987.
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Sorry, but absolutely nothing you have written here is relevant to the point being made: that attached flow can cause drag.

So I'll say it again.

1. Honda Insight Gen 1 - attached flow over rear window. (Tuft test your own car if you want to take issue with that.)

2. Measured pressures (refer to above pic of measured pressures on Insight):

3. Draw in the force vector for -80 on the hatch. (Pressure forces act at right-angles to the panel.)

4. Resolve the vector into lift and drag elements (use the triangle of forces - engineering 101).

5. Note that attached flow is, in the case, causing drag (and lift).

As I said, if you think that pressure drag can be caused only through separation, you are making a very basic mistake.