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#1 Dunc

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Posted 29 July 2020 - 18:10

I've been reading about the 1982 season and the decision that year to ban skirts for 1983 following all of the horrific crashes of that season.  It's prompted me to look into skirts, as l have to admit, it's not a subject I knew a lot about.

 

Just out of curiosity, what would be the consequences of bringing them back? I know they made the sport incredibly dangerous but given the advances in safety etc since then, would it be possible for them to come back and not result in death?


Edited by Dunc, 28 January 2022 - 16:47.


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#2 FNG

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Posted 29 July 2020 - 18:16

No more dangerous than DRS today. It was a moveable device that if failed could and did have consequences. Much like DRS today.

 

I think the engineering standards of today would make it for the most part a non issue. We could easily have skirts today.

 

By the way you posted this in the wrong forum...



#3 Dunc

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Posted 29 July 2020 - 18:22

No more dangerous than DRS today. It was a moveable device that if failed could and did have consequences. Much like DRS today.

 

I think the engineering standards of today would make it for the most part a non issue. We could easily have skirts today.

 

By the way you posted this in the wrong forum...

 Oh dear, sorry all, the consequences of being distracted by a Zoom call!

 

Can one of the mods either delete or move?



#4 Slartibartfast

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Posted 29 July 2020 - 18:24

By the way you posted this in the wrong forum...

 

Are you sure?   ;)



#5 Dunc

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Posted 29 July 2020 - 18:24

Now it's in the right place, thanks.



#6 Izzyeviel

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Posted 29 July 2020 - 22:02

No more dangerous than DRS today. It was a moveable device that if failed could and did have consequences. Much like DRS today.

 

I think the engineering standards of today would make it for the most part a non issue. We could easily have skirts today.

 

By the way you posted this in the wrong forum...

Not quite, A DRS failure is something you're likely to notice and do something about, with skirts, the moment you'd realize you're in trouble is when the marshals are rescuing you from the tree you crashed into.

 

Also if i've remembered correctly, modern ground effect can be achieved without skirts so they won't be coming back.



#7 Dunc

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Posted 30 July 2020 - 08:32

Not quite, A DRS failure is something you're likely to notice and do something about, with skirts, the moment you'd realize you're in trouble is when the marshals are rescuing you from the tree you crashed into.

 

Also if i've remembered correctly, modern ground effect can be achieved without skirts so they won't be coming back.

 

Oh, I know they have no chance of coming back, I'm just interested in the theory of whether they could come back. Given we have better track safety, stronger cars, better medical facilities run-off areas now would that make them less of a risk?



#8 jcbc3

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Posted 30 July 2020 - 09:00

..., modern ground effect can be achieved without skirts so they won't be coming back.

 

I like old fashioned ground effect better!

 

I'm pretty certain that given a free hand and with the option of skirting the cars, the designers would go for skirts.



#9 Charlieman

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Posted 30 July 2020 - 10:11

I'll start with a brief history of skirts. Some of the details are fuzzy because teams were intentionally unclear about how they used skirts. Other errors are caused by my memory.

 

Fixed skirts were probably first used on the Chaparral and McLaren Group 7 sports cars. They were used longitudinally and laterally to create a low pressure area around/behind the driver's bottom, Chaparral using a fan. In F1 fixed skirts appeared with McLaren and Brabham in the mid 1970s, in the fashion of the McLaren Can Am cars and would have been in use at the time that Lotus were developing their wing and ground effects cars.

 

Lotus tested and abandoned a brush system (similar to a draught excluder or the seals on revolving doors) on the model 77 and 78. For the 78, Lotus also tested a fixed skirt with a hinge half way up. By the time that the Lotus 79 briefly dominated, Lotus had decided to adopt sliding skirts, arguing that they were fixed to the sidepod wall and thus were not a moveable aerodynamic entity... For the Lotus 80, the team used a sliding skirt which weaved around the rear wheel (i.e. not straight) which did not rise and fall correctly. Other teams (e.g. Ligier) experimented with straight sliding skirts in the rear wheel region (eventually banned). Sliding skirts were banned completely after a few years and minimum ride height regulations were introduced, leading to the use of fixed skirts with ride height adjusting suspension (Brabham followed by everyone else). A few more years later, the regs required 'flat bottomed' cars, leading to the diffuser, exhaust extraction and more. 

 

Skirt problems? 

* Brush skirts: Didn't seal sufficiently for late 1970s designs.

* All skirts: Low pressure could 'suck' the skirt underneath the sidepod. Lots of photos show skirts which are not hanging vertically. Trailing/running edge wear. Wear surfaces used ceramic or metal inserts which broke away creating track debris. Intermittent leaks in the venturi tunnels (caused by track bumps etc) lead to 'porpoising' -- ride height changes or pitching. Insufficient rigidity in the sidepod would have made everything unpredictable.

* Fixed skirts, with or without a hinge: Don't seal until the car is pushed down on its springs and tend to leak on anything but the smoothest track.

* Sliding skirts: Need to be straight and the rise/fall sliders require a lot of testing/development. Top teams ran a separate group to maintain skirts at the races, which increased costs. Riding over kerbs is a risky act and an extensive off-track excursion rips skirts off completely. In F1, skirt loss on one side of the car tended to result in a high speed spin -- although I am sure that there were even scarier accidents as well.

* Fixed skirts plus lowering suspension: Reduced one cost (skirt maintenance group) and introduced a new one (ride height hydraulics group). F1 teams and their suppliers had done an incredible job to create fixed skirts which worked as well as sliding skirts.

 

If sliding skirts were permitted in F1 today, thousands of spectators would die from boredom. The cars would have so much downforce that they would not budge from their line on anything but the slowest corner.

 

How much downforce did cars generate at any particular time? It's impossible to say owing to different testing facilities, but we can assess high speed corner performance (top speed through a known radius). In CART racing where venturi tunnels were permitted for a few years longer than F1, skirtless cars cornered at whopping Gs.



#10 guiporsche

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Posted 30 July 2020 - 13:43

Just one detail: if I remember well, skirts in the 74-5 Brabham's (which would explain the skirts's v-shape) and the 76-77 Mclaren's were meant to take air away from underneath the car.

Here's Coppuck on the M26:

 

“The principle of the car was to keep the air flow from underneath the car to create negative pressure on the underside of the bodywork,” designer Gordon Coppuck recalled. “I thought at the time – but I now know, of course, that I was wrong – that with all that number of square inches under the car, if you could generate a very small amount of negative pressure by keeping the air from flowing underneath, you would have more downforce. 
 
“You couldn’t really see our work. It was the plastic skirts to stop the air going under the car. We did much development with suspension, because the car understeered, so we did a new front suspension and several variations, all the things that we had done with all our previous cars.”
 
"“We had three pole positions in the last seven races [of 1977] and led five of the last six,” said Coppuck. “But it encouraged us in the wrong direction. When it came to proper ground-effect, you encourage flow underneath the car. We were working on the opposite direction trying to stop flow. That was the story of the M26, really." 
 


#11 PayasYouRace

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Posted 30 July 2020 - 15:03

I like old fashioned ground effect better!

 

I'm pretty certain that given a free hand and with the option of skirting the cars, the designers would go for skirts.

 

They would indeed, because if there's one thing that provides the best seal against the ground, it's a solid object. Even if you'e getting good stuff from vortices and the like, a skirt will do the best job.

 

 

Not quite, A DRS failure is something you're likely to notice and do something about, with skirts, the moment you'd realize you're in trouble is when the marshals are rescuing you from the tree you crashed into.

 

Also if i've remembered correctly, modern ground effect can be achieved without skirts so they won't be coming back.

 

FNG is right. Nowadays it wouldn't be a significant danger. Also, why would you be hitting trees? Are you going rallying? The main danger from the skirts was that they'd get stuck in the up position, but it's not a stretch to be able to design them to be failsafe.

 

 

 

Skirt problems? 

* Brush skirts: Didn't seal sufficiently for late 1970s designs.

* All skirts: Low pressure could 'suck' the skirt underneath the sidepod. Lots of photos show skirts which are not hanging vertically. Trailing/running edge wear. Wear surfaces used ceramic or metal inserts which broke away creating track debris. Intermittent leaks in the venturi tunnels (caused by track bumps etc) lead to 'porpoising' -- ride height changes or pitching. Insufficient rigidity in the sidepod would have made everything unpredictable.

* Fixed skirts, with or without a hinge: Don't seal until the car is pushed down on its springs and tend to leak on anything but the smoothest track.

* Sliding skirts: Need to be straight and the rise/fall sliders require a lot of testing/development. Top teams ran a separate group to maintain skirts at the races, which increased costs. Riding over kerbs is a risky act and an extensive off-track excursion rips skirts off completely. In F1, skirt loss on one side of the car tended to result in a high speed spin -- although I am sure that there were even scarier accidents as well.

* Fixed skirts plus lowering suspension: Reduced one cost (skirt maintenance group) and introduced a new one (ride height hydraulics group). F1 teams and their suppliers had done an incredible job to create fixed skirts which worked as well as sliding skirts.

 

Sliding skirts obviously. It isn't 1982 any more. The don't need to be straight (why would they?) and F1 circuits don't have the huge kerbs that they did back then. It would be the obvious way to do it, and they could be much more reliably forced onto the track to create a seal.

 

 

If sliding skirts were permitted in F1 today, thousands of spectators would die from boredom. The cars would have so much downforce that they would not budge from their line on anything but the slowest corner.

 

How much downforce did cars generate at any particular time? It's impossible to say owing to different testing facilities, but we can assess high speed corner performance (top speed through a known radius). In CART racing where venturi tunnels were permitted for a few years longer than F1, skirtless cars cornered at whopping Gs.

 

So what? If you were to have racing with full skirted ground effect, you'd be keeping things in check in other ways.



#12 PayasYouRace

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Posted 30 July 2020 - 15:06

 

Just one detail: if I remember well, skirts in the 74-5 Brabham's (which would explain the skirts's v-shape) and the 76-77 Mclaren's were meant to take air away from underneath the car.

Here's Coppuck on the M26:

 

“The principle of the car was to keep the air flow from underneath the car to create negative pressure on the underside of the bodywork,” designer Gordon Coppuck recalled. “I thought at the time – but I now know, of course, that I was wrong – that with all that number of square inches under the car, if you could generate a very small amount of negative pressure by keeping the air from flowing underneath, you would have more downforce. 
 
“You couldn’t really see our work. It was the plastic skirts to stop the air going under the car. We did much development with suspension, because the car understeered, so we did a new front suspension and several variations, all the things that we had done with all our previous cars.”
 
"“We had three pole positions in the last seven races [of 1977] and led five of the last six,” said Coppuck. “But it encouraged us in the wrong direction. When it came to proper ground-effect, you encourage flow underneath the car. We were working on the opposite direction trying to stop flow. That was the story of the M26, really." 
 

 

 

That's really outdated. As I explained in the BLAT thread, you want to encourage air to go under the car as fast as possible, lowering the static pressure.



#13 Charlieman

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Posted 30 July 2020 - 15:38

That's really outdated. As I explained in the BLAT thread, you want to encourage air to go under the car as fast as possible, lowering the static pressure.

It is imperative to know stuff without comprehension.



#14 guiporsche

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Posted 30 July 2020 - 16:03

Of course it's outdated - if you are looking at it with the benefit of 40 years of technical hindsight.

The point I made was historical. Skirts (defined broadly) first appeared in F1 not because race-car designers, with the knowledge they had at the time, intended to use them to generate ground-effects (which most had no clue about) but rather with the opposite goal (as in not encouraging air to go under the car as fast as possible).

From which you can take the conclusion that it is not because a F1 had skirts that it can be seen as anticipating ground effects. 



#15 desmo

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Posted 30 July 2020 - 17:47

If you really want to know the genesis of aero skirts in F1, you will pretty much have to get a copy of Wright's "F1 Technology" book and read "Appendix A—Ground Effect" where he describes his work on the development of skirts for the Lotus T78, the first F1 car to successfully use ground effect with skirts. Gordon Murray had used a transverse skirt on the BT44 in 1974, but it wasn't really informed by ground effect aero. 



#16 Pingguest

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Posted 01 August 2020 - 11:45

Peter Wright quite recently proposed reintroducing skirts to overcome Formula One's overtaking problem.

http://www.youtube.c...h?v=1mNmY5JYmiE



#17 Allen Brown

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Posted 15 December 2021 - 22:00

Can I ask the assembled experts about one of the predecessor technologies to ground effect, the use of fixed plastic skirts along the bottom edge of the tub?  They were designed to reduce the amount of air getting under the car and to produce a low pressure area. 

 

I was under the impression that they started about 1973 or 1974 in F1, but the earliest reference I could find was on one of the McLaren M23s in the paddock at the 1974 French GP.  They were next used in practice at the 1974 Austrian Grand Prix.  Does anyone have an earlier reference?  

 

The reason for the question is that I noticed AJ Foyt's Coyote IV was wearing them in April 1973 and as they didn't come from the car's designer, I'm wondering where Foyt got the idea.  

 

I know the Chaparral 2J used sliding Lexan skirts in 1970, but that was for a different purpose, so I'm searching for a "missing link" between the Chaparral and the Coyote.  



#18 mariner

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Posted 24 December 2021 - 17:13

Chaparral's skirts were both longtitudinal and transverse - the whole area behind the front wheels was blocked off to utilise the externally powered fan suction. They  didn't want any air flowing in from the front to reduce the vacuum. The downforce on the Chaparral was the same standing still or moving. So compared to venturis and skirts it was much more powerful at lower corner speeds

 

The Lotus skirts were for the sole purpose of preventing air coming in from the sides of the pods as the more air ( within reason) came in from the front the more the venturi tunnels " pumped" and more downforce.. Conceptually the winglets on modern planes, the end plates on wings and pod skirts all serve the same purpose to maximise the effective chord of a curved surface to exploit the Bernoulli effect more efficiently.

 

Lotus spent many hours of testing to develop the best skirt mounting system. Some systems slid inside a pair of closely mounted side box walls  " in the slot". Others used hinges , finally in a parallelogram arrangement I believe.. An old Renault 4L van was fitted with a side pod/skirt test rig out the back and driven round the Hethel test track to get the best solution.

 

A vital enabler of all skirts were the ceramic skids fitted to the bottom of the skirt. These allowed rubbing motion for a full race distance. 

 

Skirts gave a huge gain in downforce, when Gunnar Nisson first tried skirts at Hethel I think he was second a lap quicker.

 

When skirts were banned in F1  the Group C sportscars began to develop even more downforce than F1 cars because a) they had more total plan area from the full width body to pull suction in and b) the width of the area between the tyres whilst not a venturi itself acted as barrier to air rolling in sideways by it's sheer width. If you look caefully at th Jaguar group C cars you can see there is an horizontal  plate sticking out from the bottom edge of vertical  body side. This was to extend the "buffer" width with minimal l frontal area.


Edited by mariner, 24 December 2021 - 17:19.


#19 MattPete

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Posted 01 January 2022 - 03:08

... In CART racing where venturi tunnels were permitted for a few years longer than F1, skirtless cars cornered at whopping Gs.

 

Tunnels never went away in CART/ChampCar/IRL.  They may have shrunk through the years, but they've continued through the current DW12.



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#20 MattPete

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Posted 01 January 2022 - 03:45

The reason for the question is that I noticed AJ Foyt's Coyote IV was wearing them in April 1973 and as they didn't come from the car's designer, I'm wondering where Foyt got the idea.  

 

 

Not only did the Coyote IV have skirts, it had an Aeroscreen (well, a precursor):

 

Coyote-Foyt-MilwaukeeJune1975-1000x.jpg

 

Coyote-Foyt-Milwaukee1974-600x300.jpg

 

Coyote75-Foyt-Pocono1975-1000x.jpg



#21 Henri Greuter

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Posted 01 January 2022 - 11:04

Not only did the Coyote IV have skirts, it had an Aeroscreen (well, a precursor):

 

Coyote-Foyt-MilwaukeeJune1975-1000x.jpg

 

Coyote-Foyt-Milwaukee1974-600x300.jpg

 

Coyote75-Foyt-Pocono1975-1000x.jpg

 

 

Correct me if I'm wrong but this concept and generation of Coyote's was designed by Bob Riley and I recall he was still with Foyt that year  (EDIT  when this variation of Coyote was debuted, in 1973  EndEDIT)  or had just left.

 

Anyway, for 1974 he came up with what he believed to be his own Mk II version of this lowline concept car. But with AJ not making Ford/Foyt V8 engines available to anyone but himself that Mk II had to be Offy powered. Which in one way improved the Mk II quite a bit aerodynamically. the reduced frontal area making up to some extend for the loss of hp's.

This Mk II was built under his own name, the Riley, and fielded by entrant Lindsey Hopkins as the English leather Special, driven by Roger McCluskey.

 

The most interesting version of this car was the initial version, that was envisioned to us no conventional rear wing but had a tail part that was in many ways an extention of the lower part of the chassis, with an wing profile at the underside, almost like what we saw in later years in an even more extreme version being used on a car of which, when I gave info about it, someone else out here made me look being a BLATant liar.

Another difference between the Riley and that later car was that the Riley had side extentions ("fenders") attached to that rear part, remeniscent to the rear part of the first versions of the DW12, in line with the rear wheels, but on the the Riley they were less wide. (or also remeniscent to the '81 and '82 Interscope Batmobiles tail piece pontoons)

But on the Riley these "pontoons" acted as closing the underwing area and reduce air leaking into the underwing. Funny enough, on the picturework I have seen of the Riley, I can't detect anything like the skirts that AJ used like on the pictures above.

EDIT: missed initially that this were 1975 pictures, Sorry!!!"

So if the use of those skirts were an idea of Riley or originates from within the Foyt crew, one tends to believe the latter option.

EndEdit

 

The concept didn't work, due to teething issues, and the car eventually ran with a conventional rear wing

 

 

I don't have pictures of this original version that I can post. And I don't want to deal with breaking copyright issues.

But for people who have acces to a copy, the 1974 Carl Hungenss Yearbook devoted an article to the Riley with some pictures, including of that original rear end on page 79 to 81. Nice read BTW.


Edited by Henri Greuter, 01 January 2022 - 15:04.


#22 MattPete

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Posted 01 January 2022 - 20:25

Henri:

 

I think this is the rear wing your were thinking of:

 

 

Riley-Wing-2.jpg

 

Kinda reminds me of the Jaguar XJR-16, where the lower wing element looks like it is designed to help extract air out from under the car:

 

15783738283_8291b29821_b.jpg



#23 Henri Greuter

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Posted 01 January 2022 - 20:52

MattPete,

 

That is indeed the car I tried to describe, thanks for posting this nice picture!

 

As for the Jaguar you also posted, Just about all of the factory teams that participated in the `murder on endurance racing`, the 3.5 liter atmo crap years, as I remember them, Peugeot, Jaguar and Toyota all had such a rear end like as seen on the Jag you posted.


Edited by Henri Greuter, 01 January 2022 - 22:07.


#24 MattPete

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Posted 02 January 2022 - 01:09

Saw this in the 2022 Indycar thread.  Its a McLaren M24(?).   I'm pretty sure this is a flat-bottom car, and the skirts are clearly visible. Tom Frantz, Indianapolis 1980 (the M24 debuted in 1977).

 

 

Tom-Frantz-IMS-1980-dnq.jpg


Edited by MattPete, 02 January 2022 - 01:35.


#25 Charlieman

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Posted 02 January 2022 - 12:07

The M24 side skirts look similar to those used on the M23 in 1976.



#26 Allen Brown

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Posted 02 January 2022 - 14:22

Yes, the M24 skirts are inherited from the F1 M23, but the the earliest reference I could find to the McLaren M23s having skirts was in practice for the 1974 French GP.

The Coyote IV had skirts from its first race, at Texas World Speedway in April 1973.  
 
Coyote-IV-TWSApr73b.jpg

 


Edited by Allen Brown, 02 January 2022 - 14:25.


#27 Ali_G

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Posted 08 January 2022 - 11:21

Tunnels never went away in CART/ChampCar/IRL. They may have shrunk through the years, but they've continued through the current DW12.


I think most IRL cars had flat / stepped bottoms. The DW12 may have been the first running venturis if you exclude IRLs first season which used CART cars.

#28 PayasYouRace

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Posted 09 January 2022 - 17:09

The IRL cars always had tunnels, in the style of the later CART and modern Indycars.

 

ept_sports_nascar_marbles-518590235-1275



#29 Ali_G

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Posted 10 January 2022 - 07:28

The IRL cars always had tunnels, in the style of the later CART and modern Indycars.

ept_sports_nascar_marbles-518590235-1275


I was certain that their first set of cars post split had flat bottoms?

#30 PayasYouRace

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Posted 10 January 2022 - 20:07

I was certain that their first set of cars post split had flat bottoms?

 

I can't find any pictures of the first generation IRL cars upside down (though in theory there should be plenty). I can't say either way. I'd be surprised if they did have flat bottoms, because that type of underfloor was pretty well established as a good oval car at the time. Then again, everything about the early IRL was an attempt to spite CART, so anything's possible.



#31 Henri Greuter

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Posted 11 January 2022 - 14:36

I think most IRL cars had flat / stepped bottoms. The DW12 may have been the first running venturis if you exclude IRLs first season which used CART cars.

https://us.motorspor...-sheet/1667264/

 

 

Go through this page and you'll read they mention the car having ground effect.

 

here is the actual passage taken from that page.

 

 

 

For Immediate Release April 2, 1996

1997 INDY RACING LEAGUE CHASSIS CAR SPECIFICATIONS CHASSIS

Type: 1997 IRL -- open wheel, single seat, open cockpit, ground effects underbody and outboard wings front and rear



#32 Lee Nicolle

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Posted 14 January 2022 - 05:35

Personally I like women in skirts and cars with wings!