An inverse windshield top spoiler for convertibles when top down?

[Big time]

To both reduce drag by allowing flow to reattach by redirecting air downwards, and to reduce wind buffeting when the top is down as most of the wind in the cabin comes from behind this spoiler redirected wind might counteract the forward moving air in the cabin.

Something like this, depicted in red over the windshield


Will this cause lift?

[kach22i]

On most convertibles you will actually see a diverter or spoiler like lip to defect air over the heads of the occupants.

Your device is going to direct air into the face, not a good thing - would really dry out your eyes to say the least.

Most 2-seat convertibles today try an emulate the characteristics of a targa, that is to say rely on a stagnant pocket of air around the occupants, with air flow going over them.

They achieve this with screen or glass panels up behind the seats and between the occupants.

Some of these are available as aftermarket add-on's. Other's are factory standard and may pop up at speed when they are needed most.

[whatmaycome14]

Somewhere along the lines, I heard that the Lexus SC430 convertable had the same Cd when the top was down as when it was up. I've always thought this was quite impressive.

[freebeard]

You have it on backwards. Here are two guys named Shumacher and Lauda discussing the merits of this concept at an offset of 1:53 into the video named in the lower left.

Your welcome.

[Otto]

This seems akin to buffeting on a faired motorcycle, where von Karmann vortices form and collapse behind the screen, dope-slapping the rider in the face. Just like on my BMW R1100RSL. Key to fixing this is either a hugely larger screen such that the vortices collapse well behind the rider's head, or channel air up the backside of the screen to relieve the low pressure bubble and then flow up and off the leeward side of the upper screen edge, such that it meets the flow coming up and over the front side at nearer the same direction and velocity, reducing wind shear for less dope-slapping in the face.

So, I'd say that the red flap in Big Time's car might work. Or add a pop-up castellated deflector like on the leading edge of BMW sunroofs, or similar.

[kach22i]

My friend's Mini Cooper has a sunroof, and there is zero noise and buffeting from it.

An example of that design is below.

Mini Cooper S Sunroof Detail Photo 12


I'm looking for a wind tunnel picture with the sunroof open, but so far no luck.

Windtunnel photos of various cars - Miata Turbo Forum - Turbo Kitten is watching you test compression.


EDIT:
One of the best top down images I've ever found.

Mercedes-Benz-SL500-R230-wind-tunnel Photo #146939 - Motor Trend WOT


You can see the windshield inclination angle changes (+ lip on later years) over the years in the image below, much of this to the benefit of top down motoring.

Evolution 2012 Mercedes-Benz SL500 R231 2001 Mercedes-Benz SL500… - FYeah Cars

[kach22i]

Mercedes-Benz SLR McLaren in the Wind Tunnel
Mercedes-Benz SLR McLaren in the wind tunnel


http://www.ultimatecarpage.com/forum...d.php?p=976993

[Big time]

Originally Posted by freebeard

You have it on backwards. Here are two guys named Shumacher and Lauda discussing the merits of this concept at an offset of 1:53 into the video named in the lower left.

Great find! Thanks a lot.

Would this kind of spoilers also work if placed in the A pillars to keep air from buffeting you with the windows open?

Will this spoilers also help when driving with the top up or on hardtops?

[kach22i]

Mercedes-Benz Aerodynamics | Mercedes-Benz Digest News

[freebeard]

Would this kind of spoilers also work if placed in the A pillars to keep air from buffeting you with the windows open?

I don't know, but it's a testable hypothesis. Here's what the 911 people do:
Reducing Windnoise / Raingutter Fillers

kach22i -- Look what's at that link: