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Old 12-14-2023, 10:19 AM   #811 (permalink)
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'better than'

Quote:
Originally Posted by Phase View Post
isnt a bad boat tail still better than no boat tail at all? even if it sheds vorticies?
I'm not gonna go down that road. I'm a 'STEM' kinda guy, so we can part ways here.
If you ever develop an appetite for quantitative aerodynamics, you might keep an eye on England.
Dr. Jeff Howell and his merry band of researchers at Loughborough University have been in the weeds researching boat-tails.
As of 2023, they've covered 3-elements of boat-tail technology. His model-maker, Max Varney, has moved on to the Mercedes Formula 1 team.
If he can get someone to fill Varney's shoes, and can construct, test, document, and publish findings for one element per year, they ought to be able to cover all remaining elements by 2027, having caught up to 1922.
Since they're isolating one variable at a time, it will be the most granular data ever captured for boat-tail technology.
Best to you on your projects.

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Last edited by aerohead; 12-16-2023 at 11:03 AM.. Reason: splling
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Old 12-14-2023, 02:42 PM   #812 (permalink)
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Quote:
Originally Posted by Phase
isnt[sic] a bad boat tail still better than no boat tail at all?
Yes, but.... You have to balance the benefit with the pain of dragging that thing around. ....and parking.
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Old 12-15-2023, 12:31 AM   #813 (permalink)
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Quote:
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Yes, but.... You have to balance the benefit with the pain of dragging that thing around. ....and parking.
My next Prius will have a detachable one with trailer hitch mount for wide open road trips. Would never drive it around downtown Portland lol
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Old 02-19-2024, 07:53 PM   #814 (permalink)
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Getting bored. Extended roofline. Will work on sides too and probably make a mock up taped on boat tail and test it out on some back roads in next few weeks
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Old 02-24-2024, 11:51 PM   #815 (permalink)
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Whatís my new CD?
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Old 02-25-2024, 02:29 AM   #816 (permalink)
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What does your Space Age dashboard tell you?

IIRC one point is 0.010 delta. Maybe 20 points?

If you warp it into more of a curve shape and put a floor in it, that should double whatever.
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Old 02-25-2024, 12:32 PM   #817 (permalink)
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Sadly it’s not street legal so I couldn’t test it on long flat interstate roads. I felt a little less drag though on the throttle when driving around some back forest roads though
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Old 02-26-2024, 10:48 AM   #818 (permalink)
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' new Cd from tail '

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Originally Posted by Phase View Post
Whatís my new CD?
1) The tail relies on turbulence-free onset flow in order to perform to it's maximum effect.
2) We'd really need the full belly pan, diffuser, and full rear skirts to experience that kind of quality flow.
3) Most published boat-tail research findings are predicated upon the test vehicle having laminar flow ahead of the tail extension, top, sides, and bottom.
4) The Windsor Body boat-tailing research recently reported by PhD Jeff Howell et al., accommodates the tail with this laminar flow.
5) As to the lack of an 'underbody' on your tail, Lawrence Livermore National Laboratory's boat-tail research reported that a 32-inch, 4-sided cavity, had virtually the same drag reduction as a 48-inch, 3-sided tail ( wasting 16-inches of elongation potential ).
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6) As we discussed a couple years ago, if you'll do the belly, diffuser, and wheel skirts, the IONIQ will be around Cd 0.20.
7) just the 10-inche difference in length between today's M-B EQS Sedan, and EQE Sedan is Cd 0.20 vs Cd 0.22.
8) Although never published, the difference in 'length' for the active tail on the 2016 M-B IAA might be in the range of delta- Cd 0.020 as well.
9) Just the approximate, 8-inch diffuser extension on the 2022 M-B Vision EQXX = delta-Cd 0.010.
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What you're doing is 'qualitatively' the right thing for lower drag, but it needs careful handling 'upstream', and a 'floor' for the cavity extension.
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After that, the drag will vary as a function of wake area, compared to the OEM wake area.
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Old 02-26-2024, 12:49 PM   #819 (permalink)
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Well I know the shape isn’t ideal. I was just building a version without a diffuser. I can’t put my rear wheel skirts on till I get my all season tires back on. My snow tires are too thick and the wheeel skirts don’t fit on. The eqxx and all these low drag Chinese cars don’t use wheel skirts though so they can’t be THAT important. From my understanding, the roofline is the most important of any of the 4 sides. I was just wondering what the 3 sided boat tail provided versus a proper full one.
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Old 02-27-2024, 10:19 PM   #820 (permalink)
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Dirty behind the wheels because of turbulent airflow or just road spray exposure or a combo of both? I donít see that with the wheel skirts on, but jlis that because it blocks the ground dirt from spraying out of the wheel well or because of better attached flow? Hmmm

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