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Old 09-02-2022, 02:10 AM   #521 (permalink)
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Originally Posted by aerohead View Post
If you were to smear a light coat of petroleum jelly back there, and repeat, it might reveal even more detail.
We still have caliche roads nearby. It's like driving on talcum powder or diatomaceous earth. 'EVERYTHING' gets caked over!
what would the jelly show back there? i drive that route almost every week

would it even be worth adding a separation edge to get an mpg boost with that small curved sliver?

heck im wondering how much of an mpg boost boat tailing behind wheels would do...

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Old 09-02-2022, 02:26 AM   #522 (permalink)
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https://asmedigitalcollection.asme.o...T09A027/265333

anyone capable of accessing this?
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Old 09-02-2022, 02:32 AM   #523 (permalink)
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https://shareok.org/handle/11244/316319

found this. inflatable boat tail. diff study. up to 80 percent drag reduction. interesting idea but doesnt seem like it will ever be a production item
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Old 09-02-2022, 12:17 PM   #524 (permalink)
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anyone capable of accessing this?
Anyone with $25.

The abstract is odd. "An appendage is a boat tail" not a boat tail is an appendage.

"based on several mathematical curves such as kappa curve, lame curve, catenary curve and aerofoil curve." Maybe this is explained behind the paywall?

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found this. inflatable boat tail. diff study. up to 80 percent drag reduction
Open the PDF and it's the same study
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Old 09-02-2022, 01:26 PM   #525 (permalink)
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Yeah they studies looked very similar. I wish I could have an easy test boat tail to even see how much of a difference it would make without all the crazy work involved. Looked like the hardest mod to make

Still curious about the separation edge along that curved opening though at the rear and if it’ll improve anything

Probably doing boat tail foam wedges behind the tires though this weekend
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Old 09-02-2022, 02:19 PM   #526 (permalink)
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My thinking is that curved pieces will be more robust than flat pieces. Polymetal > flat foam sheets.

IIRC aeroheads inflatable was an old waterbed.

Has anyone mentioned retractable base plates?

ecomodder.com/forum/showthread.php/kammbacks-tail-aero-info-2072.html

I know I've posted a screenshot from a Coventry Universty study, but Google can't find it. I'm frustrated finding anything in my albums, since I can't sort them.
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Old 09-06-2022, 12:28 PM   #527 (permalink)
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what would it show

Quote:
Originally Posted by Phase View Post
what would the jelly show back there? i drive that route almost every week

would it even be worth adding a separation edge to get an mpg boost with that small curved sliver?

heck im wondering how much of an mpg boost boat tailing behind wheels would do...
Any dust transported within the wake, which presently does not accumulate, would be forced to adhere to the 'jelly,' perhaps revealing features of the base area that would otherwise remain 'invisible.'
Allowing 'scrubbing' air access to the taillight lenses might be an advantage, safety-wise, as traffic behind you would 'know' what you're 'doing.'
Mercedes used to incorporate horizontal ridges into their plastic lenses, so that any back-soiling would be limited to only half the surface.
If you were going to add fairings behind the wheels, you'd want to add them in front as well, just as with VW's XL1, MG EX-181, etc..
Wheel fairings are capable of reducing wheel drag by 70%.
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Old 09-06-2022, 12:30 PM   #528 (permalink)
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anyone?

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Not for $25.
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Old 09-06-2022, 12:57 PM   #529 (permalink)
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study

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https://shareok.org/handle/11244/316319

found this. inflatable boat tail. diff study. up to 80 percent drag reduction. interesting idea but doesnt seem like it will ever be a production item
Unless the setup was tested at supercritical Reynolds number, the Cds are of no help to us.
And I would argue that, when it was tested, the unbaffled tail would have the lower drag.
Whether or not this sort of thing ever made it into production, while of great interest, wouldn't affect us crazies, who could run with it in lieu of cultural imprimatur.
Kamm and Fachsenfeld tested a virtually identical setup at the FKFS, around 1935. Boat-tailing reduced drag up to 892%, depending on fineness ratio ( from Cd 0.58,to Cd 0.22- Cd 0.065 ).
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Old 09-06-2022, 01:08 PM   #530 (permalink)
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to know, without building

Quote:
Originally Posted by Phase View Post
Yeah they studies looked very similar. I wish I could have an easy test boat tail to even see how much of a difference it would make without all the crazy work involved. Looked like the hardest mod to make

Still curious about the separation edge along that curved opening though at the rear and if itíll improve anything

Probably doing boat tail foam wedges behind the tires though this weekend
1) Once all the streamlining ahead of the rear separation line is performed, the drag, from thereon, will drop in direct proportion to a reduction in the wake area.
2) Knowing the Cd, just choose a target drag coefficient you desire.
3) Whatever that percentage difference is, that drag will be delivered along with a tail with a wake area the same percentage smaller than the original wake area.
4) It's basically that straightforward.

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