http://forum.merkurclub.com/forum/viewtopic.php?t=10797
A semantic item:anglin wrote:Straight from the mouth/fingers of Rick Byrnes:
Rick Byrnes wrote:In a message dated 97-10-28 06:14:00 EST, you write:
I misplaced the original message addressing the differences in wings, and can talk to it a little. While I am not an Aero Engineer, one of my staff is, and made me privy to some actual data, performed on a XR4, with Bi Plane, Single (89) and the Cosworth RS 500 wing. AT 150 MPH:
- Bi Plane Lowest drag highest negative pressure.(lift) .328Cd
- Single wing Increased drag, a little less negative pressure .35?Cd
- RS500 45 # positive pressure (downforce) and .39? Cd.
I have looked, and cannot now find the data provided, nor do I precisely remember all the numbers (remember CRS syndrom) but all run at production ride heights, and in the same wind tunnel.
Interestingly enough, the bi plane wing is quite effecient at reducing drag without dramatically increasing lift. The number extrapolated to 200 MPH is 315 # negative pressure.
This wing was (in fact the whole car) was copied from the European PROBE aerodynamic research vehicle produced in the very early 80's I have a photo of that original and it was uncanny how much the XR4 looks like it. I have a friend who is a professor at Texas Tech Univ, (PHD in fluids), that when he first walked around my car, was amazed that so much was done right. (he has 2 SVO Mustangs so we forgive the egg head discipline).
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It sounds to me that the whale tail @ 17 # downforce would be about right since the Wickerbill on the RS500 wing makes a dramatic difference.
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Incidently, I spun my XR4 at about 170 MPH and the "load of plastic" bi plane wing stayed put, even with just #10 machine screws holding it down. Spinning is such great fun. On the salt they call it doing piroettes. (sp)
That "45 pounds of pressure" wasn't specified as a pressure, since Rick never mentioned an area (pressure is force divided by area, ie. psi = pounds of force per square inch), so I am going to make the assumption that the downforce number he provided is actually a force not a pressure. So, that's 45 lbs of total downward force not 45 lbs per square foot or something.- RS500 45 # positive pressure (downforce) and .39? Cd.