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Air flow stains side mirrors

This is a discussion on Air flow stains side mirrors within the Focus RS Discussions forums, part of the Focus RS Forums category; At this point we already know that the aerodynamic properties of the RS are similar to that of a potato. Air recirculates behind the car ...

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Thread: Air flow stains side mirrors

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    Air flow stains side mirrors

    At this point we already know that the aerodynamic properties of the RS are similar to that of a potato. Air recirculates behind the car and covers the rear windshield in dirt/snow, mine and others I've seen all have scratches on the rear windshield due to wiper + dirt. However there's at least a wiper, there are no wipers for the side mirrors. I'm not sure how this was overlooked during R&D, but the airflow around the mirror housing is atrocious and creates a vacuum in front of the actual mirrors, which in turn slams everything against the mirrors and the windows.

    The problem: the mirrors collect water droplets or anything that would stick, and I can't see sh*t especially at night. In rainy weather it never dries faster than new droplets are collected even with the heat on. During winter it's worse because it's salt water, and even if I turn the heat on and the water evaporates, they're still covered in salt residue, and I still can't see.

    I was wondering if anyone here has expertise with fluid dynamics? Could something be made to address this issue? Could a strip of 3D printed mini vortex generator help straighten out the airflow? I heard the side mirrors on BMWs have those wing things to help with airflow, is that something worth considering? Any input would be appreciated.

    I took a few pictures in winter and the salt stain visualizes the airflow pattern quite well.
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    Last edited by SilverWings-L; 06-06-2019 at 07:19 PM. Reason: formatting

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    Is your car bone stock? I live in an extremely rainy area and have not experienced this

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    Do you have mud flaps? Just wondering if some of these are from the wheels?


    Sent from my iPhone using Tapatalk

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    Quote Originally Posted by SilverWings-L View Post
    At this point we already know that the aerodynamic properties of the RS are similar to that of a potato. Air recirculates behind the car and covers the rear windshield in dirt/snow, mine and others I've seen all have scratches on the rear windshield due to wiper + dirt. However there's at least a wiper, there are no wipers for the side mirrors. I'm not sure how this was overlooked during R&D, but the airflow around the mirror housing is atrocious and creates a vacuum in front of the actual mirrors, which in turn slams everything against the mirrors and the windows.

    The problem: the mirrors collect water droplets or anything that would stick, and I can't see sh*t especially at night. In rainy weather it never dries faster than new droplets are collected even with the heat on. During winter it's worse because it's salt water, and even if I turn the heat on and the water evaporates, they're still covered in salt residue, and I still can't see.

    I was wondering if anyone here has expertise with fluid dynamics? Could something be made to address this issue? Could a strip of 3D printed mini vortex generator help straighten out the airflow? I heard the side mirrors on BMWs have those wing things to help with airflow, is that something worth considering? Any input would be appreciated.

    I took a few pictures in winter and the salt stain visualizes the airflow pattern quite well.
    Name:  IMG_9873.JPG
Views: 112
Size:  1.68 MB

    Name:  IMG_9884.JPG
Views: 102
Size:  1.58 MB

    Name:  IMG_9875.JPG
Views: 106
Size:  1.42 MB

    Name:  IMG_9877.JPG
Views: 102
Size:  1.57 MB
    Believe it or not, but the rs doesnt have that bad of aerodynamics. The air eddy behind the car actually helps with high speed stability and pulls more air from underneath the car to create
    the venchuri effect sucking the car to the ground
    SilverWings-L likes this.

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    I get the same dry salt pattern in winter. I believe mine is a little smaller and concentrated towards the front.

    I have the weatherthech deflectors and those go all the way down to the window molding, maybe the help a little with making that vortex smaller between the mirror and the door.

    Never though of actually making something about it but I did notice it too. Especially when it's just raining you can clearly see that spot where the water is just pooling and barely being disturbed.
    SilverWings-L likes this.

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    I have noticed this to a much smaller degree... and it is annoying especially as in my experience, the heated mirrors don't really heat enough. I would perhaps play with augmenting the tiny plastic flap that Ford added to the door side facing the mirror housing... maybe make it bigger? Completely different issue, but the first gen TT-RS reportedly had serious buffeting issues (cue James May) and some people took a part of an aero wiper and used that to deflect the air.
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    Quote Originally Posted by 320icar View Post
    Is your car bone stock? I live in an extremely rainy area and have not experienced this
    Bone stock. It's most noticeable when you're following another car as the tiny droplets in their tail mist get pulled inside this area way easier and it builds up quickly. Raindrops never get pulled in just because they have so much downward momentum. If you look closely (please still remain alert on the road), you can see it's the liquid on your mirror housing that drips down on the bottom of the black plastic frame, but instead of flying off the rear, they get thrown upwards and splatted on the mirrors.

    Quote Originally Posted by insanekiwi View Post
    Do you have mud flaps? Just wondering if some of these are from the wheels?

    Sent from my iPhone using Tapatalk
    And no flaps, nor weather guards. I suspect the wheels don't help; especially higher speeds, they bring up dirty water from the road surface and it fans out in the rear 90 degree angle where the tires stick out from the fenders, and some of those droplets are brought inside this recirculation, then some make contact with the mirrors, thus slowly building up.

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    Quote Originally Posted by shaddai View Post
    I have noticed this to a much smaller degree... and it is annoying especially as in my experience, the heated mirrors don't really heat enough. I would perhaps play with augmenting the tiny plastic flap that Ford added to the door side facing the mirror housing... maybe make it bigger? Completely different issue, but the first gen TT-RS reportedly had serious buffeting issues (cue James May) and some people took a part of an aero wiper and used that to deflect the air.
    The heated mirrors are at most warm, I guess to avoid getting someone's fingers burned. I was really confused why that plastic flap thing is only on the driver's side and the right side is flat; I thought it was for aero purposes but not sure exactly what, and they're not symmetrical which confuses me.

    After a quick google search, I believe you're referring to this:
    https://forums.vwvortex.com/showthre...wind-buffeting!

    I can definitely see how it could work, it essentially rearranges or disturbs the local airflow from its current arrangement, and it'd easily solve the buffeting issue as wind buffeting only happens in a small region of circumstances, and a random rearrangement is unlikely to land in that region again. Correct me if I'm wrong. I was thinking similar ideas when I mentioned the mini vortex generator strip, perhaps I'll figure it out in a few years when I've studied fluid dynamics, but right now I'm not sure. If we can't figure out why and solve the problem from its roots then I could, though not preferred, resort to trial and error I guess.

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    Quote Originally Posted by SilverWings-L View Post
    After a quick google search, I believe you're referring to this:
    https://forums.vwvortex.com/showthre...wind-buffeting
    I used the same trick on my 2013 ST to help keep the center of the rear window clear. The center exhaust outlet and the center pillar of the ST rear wing conspire to deposit airborne dirt, exhaust and that salty brown mist in the air from winter roads down the center of the rear window. Take a look at a current F1 car to see how much they utilize 'vortex generators'.
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    Hmmm, came in here expecting one issue, the one I have, and see a different one.

    I get water streaks on my side view mirror housing; on the housing that is on the inside of it, in that little gap between the inside of the housing and the car. Would take a picture, but my car is super clean right now.

    Living in Denver with all the sand and stuff put on the road in winter, I would imagine someone posting similar issues on the local FoRS/FoST group about it. I honestly don't drive mine in the crud unless necessary, so I haven't personally experienced your problem.

    Do we think a ceramic coating would help with this issue? Or because it's partially trim, it's still going to stick?

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