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Old 05-20-2020, 10:42 AM   #61 (permalink)
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should I ?

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Originally Posted by COcyclist View Post
I want to see this version tested.
I'd just follow Ford's contour,as if you were completing it with a french curve. I'd also just drop the side aprons (capping plates) down the the bottom of the glass, enclosing as much side area as you can. You'll have a little more blind-spot, so use your side mirrors frequently to know your driving environment at all times.

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Old 05-20-2020, 11:55 AM   #62 (permalink)
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Quote:
Originally Posted by aerohead View Post
I'd just follow Ford's contour,as if you were completing it with a french curve. I'd also just drop the side aprons (capping plates) down the the bottom of the glass, enclosing as much side area as you can. You'll have a little more blind-spot, so use your side mirrors frequently to know your driving environment at all times.
can you elaborate on that with a crude drawing on top of my photo?


also, took a picture after few days on a dusty road, notice that the sections in the sides have less dust than the center section which does not have a hole....so this means....what ? that the holes are working or not?

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Old 05-20-2020, 12:27 PM   #63 (permalink)
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Elaborate

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Originally Posted by eagle View Post
can you elaborate on that with a crude drawing on top of my photo?


also, took a picture after few days on a dusty road, notice that the sections in the sides have less dust than the center section which does not have a hole....so this means....what ? that the holes are working or not?

I don't know how to draw online. Sorry! What you're looking for would be like the 1987 Renault Vesta-II or Mercedes-Benz Bionic car. These are both 'Kamm-back' cars. Chopped off at the back like a loaf of bread.
For the limited length we're talking about,you can't expect to see any significant gains,although you'd be set up for boat-tailing should you ever choose that.
The slots on your 'wing' provide a downwash to help prevent dust from the turbulent wake from accumulating on the glass.
If you had a horizontal rubber fin,on the edge of the hatch,just above the blue oval badge, this might help keep some of that dust sequestered away,but it would need to be rubber,for pedestrian safety.
With that,you could extend your 'wing',seal those holes, and enclose the sides;creating an air-tight cavity,which would allow a little flow deceleration and higher pressure before separation,leading to less pressure drag.
Any meaningful drag reduction could only come from a box-cavity or boat-tail. Hucho has personally tested both technologies and they're the only two devices that ever 'showed' drag reduction.(the 2016 Mercedes-Benz IAA concept does this with an extensible boat-tail section,a lineal descendent of Fachsenfeld's FKFS design of 1935 for the K-cars).
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Old 05-20-2020, 01:52 PM   #64 (permalink)
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Quote:
can you elaborate on that with a crude drawing on top of my photo?
I could. But I'd have to down the pic, Photochop it and up it again. All you would see is the trailing edge of the sail panel, instead of aligning with the bumper cut line, would be essentially vertical and extend to the body crease that bisects the taillight.

Easier to repost an old pic.


That said, if you still need it I will take the time.
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Old 05-20-2020, 02:15 PM   #65 (permalink)
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Audi A2

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Originally Posted by freebeard View Post
I could. But I'd have to down the pic, Photochop it and up it again. All you would see is the trailing edge of the sail panel, instead of aligning with the bumper cut line, would be essentially vertical and extend to the body crease that bisects the taillight.

Easier to repost an old pic.


That said, if you still need it I will take the time.
That's a great example freebeard! Coventry University folks cut drag from Cd 0.288, down to Cd 0.204. Really sweet!
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Old 05-20-2020, 05:26 PM   #66 (permalink)
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Back in 2013, I posted that Coventry study. I tried to imitate the box cavity, but it was beyond my design and testing ability. Anyway, I included another part of that study in my thread that is also of interest. Here:
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Old 05-21-2020, 02:32 AM   #67 (permalink)
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that is what I am talking about

I am thinking that apart from the extension the sides should come down and be "bent" / enclosed to the inside for a more boat tail effect
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Old 05-21-2020, 10:44 AM   #68 (permalink)
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Quote:
Originally Posted by aerohead View Post
... If you had a horizontal rubber fin,on the edge of the hatch,just above the blue oval badge, this might help keep some of that dust sequestered away,but it would need to be rubber,for pedestrian safety. ...
I can visualize it, but do you know examples? I think eagle could experiment with sturdy cardboard fins, attached with painter's tape, which should hold fine for testing in a spot like this on the car.

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that is what I am talking about

I am thinking that apart from the extension the sides should come down and be "bent" / enclosed to the inside for a more boat tail effect
You can experiement with lots of positions. Tuft testing will help you understand what to keep.
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Old 05-22-2020, 11:25 AM   #69 (permalink)
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'bent'

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that is what I am talking about

I am thinking that apart from the extension the sides should come down and be "bent" / enclosed to the inside for a more boat tail effect
I'd advocate that the new 'green' lines extend down to the crease in the hatch,just above where the Ford oval emblem is,enclosing more volume.
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Old 05-22-2020, 11:38 AM   #70 (permalink)
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example

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Originally Posted by California98Civic View Post
I can visualize it, but do you know examples? I think eagle could experiment with sturdy cardboard fins, attached with painter's tape, which should hold fine for testing in a spot like this on the car.



You can experiement with lots of positions. Tuft testing will help you understand what to keep.
I caught a glimpse of the Lamborghini Urus SUV the other day,which,I think,has a small,horizontal fin/spoiler,extending horizontally from the hatch.If the rear 'wing'were extended all the way,even with the fin,and sides installed to close it all in,you'd have a 'Kamm- back.'
This 'elongation' allows for flow deceleration and pressure recovery before it ultimately separates, increasing base pressure,and lowering pressure drag.
It would aggravate rear vision.With today's availability of synthetic vision,this issue becomes less and less a challenge to overcome.

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