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Old 07-21-2018, 12:54 PM   #11 (permalink)
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stepped-hull

Quote:
Originally Posted by gumby79 View Post
If the louvers were v-shaped instead of straight then they may act like a step hull of a boat, reducing wetted area intern drag.
Making channels for the higher pressure on the sides to merge with the lower pressure center while minimizing disturbance of the front to back flow.
Im curious if the severe reduction in Reynolds number would mute any effect from this design in the air, or if the speed at which it works is too high for Road use.
In air,each step would trigger separation,creating a locked-vortex,then re-attachment downstream,only as long as there was airtight glazing underneath the louvers.(like the bed of a pickup with a tonneau cover)
There'd be a pool of dead air captured for the air to skip over.You can see this in the original video of Spirit at DARKO.
We can't really reduce the wetted area,since we're in a single fluid environment,unlike the boat hull's natural dual-fluid environment.
And Reynolds number is the same,as it's simply a function of vehicle length and velocity,which isn't altered.

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Old 07-25-2018, 11:29 AM   #12 (permalink)
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Re: Post #3

I did reach out to this outfit. They do exist. Looks like a sideline of a vehicle modification house. None of the gearheads in the Naptown area has ever heard of them.

Communication is not their strongpoint. I e-mailed them a couple weeks ago and still haven't heard jack from them.

I called them and somebody did answer the phone, but they put me on hold and forgot me.

Small business USA, I suppose.
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Old 07-25-2018, 11:36 AM   #13 (permalink)
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Re: Post #9

I am sure that even though it doesn't fit the template, it is considerably better than nothing.

My old black monstrosity (see my avatar) was nothing more than a straight line from the top of the rear bulkhead on the cab to the top of the factory tailgate, 17 degrees from horizontal. But it was good for 1.5 MPG. That ain't chopped liver.

Phil's is better because he extended his tail.
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Old 07-25-2018, 11:46 AM   #14 (permalink)
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This has given me an idea for another vehicle.

I picked up a 2010 Crown Vic Police interceptor in an auction. Solid car but not the least bit aerodynamic. Classic three-box layout.

Despite that, it gets surprisingly good MPG. This summer, I'm averaging about 24 MPG despite the fact I'm driving like a maniac. I did put Mooneyes on it.

Looking at the truck cap Bondo spotted, I'm thinking: Why couldn't I use a rack of louvers to improve the air flow on the P71? Hinge it at the top of the roofline and put a pair of tracks on the truck lid for roller followers on the rack of louvers. That way the rack of louvers would move up out of the way when the trunk lid is opened, and would automatically lower when the trunk lid is closed. That way, I'd get the best of both worlds. My air flow would stick to the louver profile (at least better than nothing) and I would still have decent visibility out the rear.

Whaddayathink?
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Old 07-25-2018, 12:12 PM   #15 (permalink)
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Quote:
Originally Posted by Big Dave View Post
I picked up a 2010 Crown Vic Police interceptor in an auction. Solid car but not the least bit aerodynamic. Classic three-box layout.
'93 - '97 model is reported to have a Cd of .33. 2010 model should be similar, no? That isn't a bad starting point. I'd bet it would take nicely to a aero cover for the rear window / trunk as you are proposing.
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Old 07-25-2018, 12:46 PM   #16 (permalink)
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Quote:
Originally Posted by aerohead View Post
In air,each step would trigger separation,creating a locked-vortex,then re-attachment downstream,only as long as there was airtight glazing underneath the louvers.(like the bed of a pickup with a tonneau cover)
There'd be a pool of dead air captured for the air to skip over.You can see this in the original video of Spirit at DARKO.
We can't really reduce the wetted area,since we're in a single fluid environment,unlike the boat hull's natural dual-fluid environment.
And Reynolds number is the same,as it's simply a function of vehicle length and velocity,which isn't altered.
I think there is a window under the louvers, so it is essentially sealed.
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Old 07-25-2018, 02:53 PM   #17 (permalink)
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Quote:
Originally Posted by Big Dave View Post
This has given me an idea for another vehicle.

I picked up a 2010 Crown Vic Police interceptor in an auction. Solid car but not the least bit aerodynamic. Classic three-box layout.

Despite that, it gets surprisingly good MPG. This summer, I'm averaging about 24 MPG despite the fact I'm driving like a maniac. I did put Mooneyes on it.

Looking at the truck cap Bondo spotted, I'm thinking: Why couldn't I use a rack of louvers to improve the air flow on the P71? Hinge it at the top of the roofline and put a pair of tracks on the truck lid for roller followers on the rack of louvers. That way the rack of louvers would move up out of the way when the trunk lid is opened, and would automatically lower when the trunk lid is closed. That way, I'd get the best of both worlds. My air flow would stick to the louver profile (at least better than nothing) and I would still have decent visibility out the rear.

Whaddayathink?

I think we'd like to see a build thread and some testing.
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Old 07-27-2018, 12:20 AM   #18 (permalink)
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I’ve known a number of people to hit 30-mpg with the civilian spec CV on road trips. Guys who know what FE is about (truckers). Happy coincidence, so far as they’re concerned.

Along the way there have been some foreign sedans with that truncated look the P71 might wind up with. Lagonda, or them other Euros.

Write something insulting, in French, on the car. So that, as you go past — looking down a long Gallic (fake) nose — they’ll not know whether you’re serious or not.

Hell, just some trompe l’oeil to make it a Citroen.

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