Quote:
Originally Posted by SpeedballTrix
"~ 75 lbs of downforce at 60 mph.
~ 200 lbs at 100 mph.
~ 400 lbs at 140 mph."
How do you figure that?
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Remember when I said the downforce was proportional to the square of speed? Well, the formula for the lifting force is 1/2 * air density * velocity^2 * lift coefficient * wing area.
To get force in pounds, you need to use consistent units, in which case standard sea level density for air is about .002377 slugs/ft^3, velocity is in ft/sec (mph * 88/60), lift coefficient is dimensionless and wing area is in ft^2.
So you can plug the formula into your calculator or use an Excel spreadsheet as I did. So if you have speed in miles per hour as your independent variable, the equation would look something like this:
Downforce (lb) = 1/2*.002377*(mph*88/60)^2*Cl*area
And with a Cl = 2.0, and wing area = 4 ft^2, you get the following results:
You can extrapolate the above numbers that I quoted from the graph, or pull them from the spreadsheet as I have done.