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Old 05-28-2020, 07:20 PM   #13 (permalink)
Cyborg ECU
California98Civic's Avatar
Join Date: Mar 2011
Location: Coastal Southern California
Posts: 6,297

Black and Green - '98 Honda Civic DX Coupe
Team Honda
90 day: 66.42 mpg (US)

Black and Red - '00 Nashbar Custom built eBike
90 day: 3671.43 mpg (US)
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Originally Posted by JulianEdgar View Post
So if the template can be scaled in the way you describe, isn't it basically just an angle? The angle from the front the windscreen header rail to the rear of the car?
No, it is a curve. And its placement is generally indexted to the point of greatest roof camber. It has been used here to design Kamms and boat tails as well as trailer hitch storage boxes and more. As I said, kick some butt by building one on MetroMPG or Bottsaper's model for the Gen 1 Insight and throttle stop test it. Would be a great test.

Originally Posted by JulianEdgar View Post
And then when we look at cars with angles that differ like the 2020 Tesla Roadster and 2019 McLaren Speedtail, isn't it just a range of that angle?
Not sure I know how to answer that. Best policy in anything is never to be doctrinaire. [?]

Originally Posted by JulianEdgar View Post
You say "It has had very good effect nearly all the time, on a variety of vehicles, in a variety of tests but usually testing has been limited to somewhat longterm fuel economy tracking."

I'd expect that to be the case if the flow remains attached - and that's great. But what I cannot see is why this is somehow regarded as the best shape.
Not to me, but aerohead will have to explain what else he thinks it accomplishes.

Originally Posted by JulianEdgar View Post
It's like the person who says a particular airfilter gave good engine power - but hasn't compared it to any others.
Oh, he and we have compared it to others... the various template threads and countless other debates here would attest to that. This EM board debates alright.

Originally Posted by JulianEdgar View Post
... I think the idea that there is a 'best shape' is a bit simplistic - and especially in the real world, the thickness of the boundary layer (that in turn will depend on what is happening on the forward section of the car) will help determine if the flow remains attached.
It is simple and it works, which is Pragmatism's test of truth. Simplistic is pejorative. What matters it that it is a form that DIY modders can overlay onto a lot of bodies and get results. But you make a reasonable point: there are more possibilities.

Originally Posted by JulianEdgar View Post
As to swimming upstream - that's something I am very used to doing, especially in the often group-think environment of an online discussion group!
C'mon man, this is not a group think environment. Plenty argument here before you showed up, and about the template, too.
See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.

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