Here's a visual on a Porsche 914 that was tested:
The 914 was tested at:
*180mm
*165mm
*140mm
*zero
Here is a pictorial of how the 914's effective fineness ratio varies between the two G.C. extremes.
Here we see VW's Flow Body drag vary with G.C.,and also with the addition of wheels.
Here,Ford gets a four-for,lowering their 1983 Probe-IV,lowering a deployable airdam,then hiking the rear end to finally achieve the inclination which achieves the lowest Cd and also reduces frontal area.
*The Probes official ground clearance does not take into account the effect of the fully-deployed airdam which actually reduces G.C. to about 1.92" (48.76mm)
*Lowering alters the fineness ratio from 3.702,to 3,80 (2.6%).
*The computerized attitude control moves the max. roof camber position 9.54" ( 242.3mm) aft.
*The attitude also alters the backlight-to-boot angle,from 18.5-degrees,to 16.5-degrees,a 10.8% change.
*The attitude also converts the entire belly to a 2.5-degree diffuser.
*Lowering submerges the tires into the body,however,the 3" (76.2mm) extension of the airdam raises the frontal area,leaving the car at essentially a constant 20.5 sq-ft (1.905 m-sq) frontal area.
*From scale drawings it is very difficult to discern that the final height is any lower than the 'urban' setting due to the lifted tail.
*The final initial design came in at Cd 0.17.
*Ford had anticipated Cd 0.18.
*With a lot of work on the side-view mirrors and other tricks she came in at Cd 0.152.
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The 1937 Schl'o'r (Pilbug) car
Neil mentioned this one and it's good for us,as Hucho included it in his book with a drag breakdown based upon ground clearance.
I did a photo-enlargement of Hucho's table and solved it graphically for the test data points included.
*The Pilbug is 1,275mm high.
*Based on this height and length we're given the following info
- @ G.C.= 3,315mm ----------------------------- Cd 0.1057 (smooth belly)
- @ G.C.= 1,730mm------------------------------ Cd 0.1086 ditto
- @ G.C.= 923mm-------------------------------- Cd 0.116 ditto
- @ G.C.= 529mm-------------------------------- Cd 0.1306 ditto
- @ G.C.= 268mm-------------------------------- Cd 0.141 ditto
- @ G.C.= 232mm-------------------------------- Cd 0.158 ditto
- @ G.C.= 232mm-------------------------------- Cd 0.186 ('Standard underbody')
- @ G.C.= 0mm---------------------------------- Cd 0.201 (guestimate) with smooth belly
- The smooth bellypan is good for a 14.67% drag reduction,or without it,the drag rises 17.72%.
I've got pictorials in the works,but Copy-Pro is closed this weekend for Easter and it will be next week at the earliest before I can progress.Also got other pans on the burner.
I'll add material as its generated.
