Vertical Rear Glass Airflow

[jlmccuan]

I sketched a quick diagram to hopefully get some input here.  My car has an almost vertical rear glass, slightly recessed in the C-pillar and under the roof.  It's kind of like the late 70's Cup cars like the Monte Carlo before they built the AeroCoupe.  Now for the question.  If a slot above the rear glass could hinge open in combination with NACA ducts on the side windows, would the air move out of the cabin into the low pressure area as the airstream coming over the roof begins to roll down in the turbulence behind the rear window?  If air could join the end of roof flow would it benefit the aero problems caused by the near vertical back glass?  Are there any other tricks to get the air coming over the roof of the car to come down over the deck lid and not create lift and suction?  I hope I explained this with some clarity.

[Dynoroom]

What class?

[kiwi belly tank]

I don't think we have a class for mail delivery.....hang on, I just got the new rule book! 
  Sid.

[jlmccuan]

I'm really not interested from a classification standpoint as much as from an understanding.  The early 80's NASCAR boys had a similar issue before the advent of the Aerocoupe.

[ONEBADBUG]

I've been thinking about the same problem, except my car has NO window. Vortex generators on the roof is all I've thought of.

[SteveM]

I don't know the answer to your question, but do have some experience with pickup trucks and sliding rear windows.

Typically, when a sliding rear window is opened on a pickup truck, the inhabitants of the cabin feel air moving forward, as it enters from the open rear window. 

I don't understand it, but have experienced it.

Steve.

[DEEPNHOCK]

Sort of what Carroll Shelby did with the back window of his Mustangs?

[Ted Hlokoff]

The 68 Dodge Charger had an inset (forward of the Cpillars) rear window glass, as did the 66 Chevelles.

The 69 Daytona 500 had a flush front grille and the rear window was moved back to mount flush with the C pillars for better aerodynamics.  The later Daytona 500 model had the pointed nose and high wing. 

An Open Road Rally car of Jim Peruto's was built from an older Chevelle.  F.A.S.T built the car and the rear window was made from plexiglass and reshaped to extend halfway down the trunklid in a Hatchback form ... 

[Stan Back]

I've waited 10 months for that answer!

[tauruck]

I would have helped but I missed the thread.

SDSU (Prof Katz) students built a quarter scale model of my truck which has a similar rear window to the rendering posted.

The wind tunnel showed the aero was good except for the area you asked about.

Joe Katz suggested building panels to run from the sides of the roof sloping back down to the top of the loadbox.
Nascar trucks have a system that works.

Similar to what Ted described.

[64avanti]

Jim,
I think you were planning to run in a production class so you can't do too much to help the issue that the rear window is almost vertical.   Even the other cars with the rounded rear window that yours is based on is most likely not much better in that area.  In fact your trunk lid is better than the rounded one!

[Bratfink]

Unfortunately this will likely not solve your problem, You need to find some way to duct air into that cavity from a high pressure area (i.e. stagnation point) on the car. You might be able to use some form of air curtain down the side to redirect air in that area, but I think the rules might be quite tight on that sort of thing (depending on class of course).

However, just opening the glass a bit will get lots of air into the cabin!