Aero// Hardtop glass delete?
 

NA, caged. W2W, T/A, lapping. splitter/GTC 200/hardtop. Tracks are high speed, Mosport GP, 140 MPH. Any consensus on hardtop glass delete for aero? Hurricane in cockpit past 80 MPH, unbelieveable buffeting. Searching brings up nothing conclusive, anybody do back to back testing on this?

I run no windows but still have hardtop glass (plexi actually). No buffeting problems up to 120mph.

My understanding was that for a low mount 3D wing, you keep the glass as the wing is designed to manage the central airflow over the roofline, unaffected by the removal of the window. For 2D wings though, you remove the window in order to provide more (and straighter) airflow over the centre of the wing.

My hardtop window will be disappearing when I move to a high mount 2D wing.

airflow coming out of the cabin is not going to go over the wing if you have a high mount 2D wing IMO. It should be quite turbulent too.

tks. I've got a medium height 3D, I'll keep the rear glass in place.

If you get one of these truck window deflectors, not only will buffeting be cut down but you can smoke while you race too.

https://www.miataturbo.net/attachmen...ine=1462343238

Matt Andrew's back to back class championship winning NA at Super Lap battle/Redline time attack had aero designed by the now world renowned aero engineer Andrew Brilliant. He didn't have the rear glass and I would have to imagine that it was for a reason. Although, it was a custom carbon hardtop so there's a small chance that he just didn't buy a glass or lexan window for it. That was the situation with mine, I wanted actual glass and couldn't find one so I just ran without it. No problems to report with wind (hurricane) and for a track car without AC, the breeze is nice.

Oops, that blue car was supposed to be this pic of my car/hardtop.

dammit! lol

Clearly he just wanted easy access to the adjusters on the remote reservoirs. ;)

That car (Matt Andrews) still holds the Miata record at Auto Club Speedway. *shakes fist*

Yup, Matt Andrews car is what got me thinking about rear window delete in the first place.

Two aspects to this, car drag, and wing performance. Wing performance is easiest to see, tuft the airflow in front of the wing and see what changes with/without the rear window, that should directly translate to changes to how the wing is working. My guess is that wing position would be a big factor in any changes brought about by a window-delete - the higher the wing, the less impact it would have. OTOH, maybe that extra flow in that location has a stabilising effect on the otherwise turbulent airflow off the rear window and/or reduces the downwash over the top onto the wing ...

More extensive tuft testing of the flow above the boot should show up what changes occur there, but you'd be interested in drag primarily and I am not sure exactly how turbulence manifests as drag. Coast-down testing might be the go for this?

Of course, it is easy just to follow what (seems to) work, but it is nice to understand what is happening, and perhaps why.

I used tufts and a go-pro to find optimum angle. Wing works great, but I've never had a glass (or lexan window) to compare.