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  #41  
Old 04-09-17, 11:40
gixxerthou gixxerthou is offline
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For what it may be worth, looking at the logging last night from Pembrey, 2 holes down on a Jedi rear wing (not a vast aerodynamic device) yields 3 mph down the straight. Vmax 128mph from 125mph. This, of course, is lost in the usual variance, but nonetheless it was repeatable (twice). Birdstrike around Honda may well have caused some hesitation. Final time, however, was identical. As I've said, difficult (for me anyway) to see how much laminar air is available to the Jedi rear wing, after it's scrabbled over the bodywork and extraneous matter.
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  #42  
Old 04-09-17, 18:42
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T13EES T13EES is offline
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Quote:
Originally Posted by kano nordie View Post
Simon I think that's supposed to refer to changing your women
John
Probably a darn sight cheaper too John ! LOL
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  #43  
Old 04-09-17, 20:10
kano nordie kano nordie is offline
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Originally Posted by T13EES View Post
Probably a darn sight cheaper too John ! LOL
Divorce can be costly too, think changing cars may be the better option at least you can sell on the old one
John
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  #44  
Old 06-09-17, 16:47
Brakedisc Brakedisc is offline
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Just done a CFD programme on a FF1600 design. Confirmed my worse fears in that we will need to get a ROPS certificate. The drag from anything that does not need one is horrendous.

Good old MSA have got us again.
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  #45  
Old 06-09-17, 17:03
asklepios asklepios is offline
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Quote:
Originally Posted by shortie2 View Post
running higher wing angles can stall the aero thus reducing drag (and downforce) at speed
Just on a technical point, does drag reduce when wing stalled? Seems a bit counter intuitive. I thought the drag remains but lift dissipates, so L/D ratio becomes adverse.
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  #46  
Old 06-09-17, 17:40
rmmitchell rmmitchell is offline
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Quote:
Originally Posted by asklepios View Post
Just on a technical point, does drag reduce when wing stalled? Seems a bit counter intuitive. I thought the drag remains but lift dissipates, so L/D ratio becomes adverse.
(sorry to butt in)


Drag is made up of two parts:

Zerolift drag (CD0) and lift-dependent (induced) drag (CDi).
The first comes from the shape of the wing, the second from the fact that it creates vorctices as the wing generates lift. The induced drag increases with lift squared.

CD = Cd0 + Cdi

CDi = k CL^2.

Where k is a constant depending on the size and shape of the wing (things like endplates reduce k)

So if you stall the wing the induced drag disappears, so you are left with the zero lift drag. If you have a decent amount of lift, this reduction is bigger than the extra zero-lift drag due to the flow separation at stall.
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  #47  
Old 07-09-17, 09:55
asklepios asklepios is offline
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Thanks for the tutorial. Understand .
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  #48  
Old 07-09-17, 12:36
rmmitchell rmmitchell is offline
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Sorry it's so terse. I wrote a longer better explanation that was easier to understand, but it got lost in posting.
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  #49  
Old 16-09-17, 10:45
shortie2 shortie2 is offline
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Im sure there was an article in racecar engineering about this pertaining to 'bending wings in F1 where multiple stacks retained wing angle but the gaps between reduced allowing the air to detach and stall
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  #50  
Old 17-09-17, 21:10
rmmitchell rmmitchell is offline
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Yes something like that was in RCE.

If you tailor the stiffness of the flaps you can get the wing to stall at high speeds. This can be through the flaps bending or more likely through the slots between the wing elements "closing up" and stalling the wing. That's why F1 (and LMP's I think} have rules about the slot gap separators (the bits that keep the wing elements kinda fixed relative to each other).

It's tricky though. The last thing you want is your front or rear wing to stall in the middle of a high speed corner.

Or you could just put an actuator on the rear wing flap and pitch it down (Leading edge up) to kill the downforce. i.e. DRS.
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