Drag coefficient calculation for sphere off by factor of 10

[Euan2007]

Drag Coefficient out by a factor of 10, can anyone help??

Im doing an experiment on the drag of a sphere and am trying to work out the drag coefficient. From looking at data online this should be around 0.5 (its a smooth sphere). Using a wind tunnel I measured the drag for various sizes of spheres and wind speeds. An example of one of my results is

Drag - 0.68N
Wind Speed - 7.8m/s
Radius of Sphere - 0.0371m

Then, using the formula

Drag coefficient = (2 x Drag) / Area x Wind Speed^2 x Density of Air

Having measured the room temperature to be 22 degrees celsius I took the density of air to be 1.204kg/m^3 and the projected frontal area was calculated using pi x r^2

But this equals 5.039! so could anyone point out where I am going wrong?? I am 90% sure all of my values are correct. Thanks in advance for any help :)

 

[Weirdbro]

Are you absolutely sure about the calculated drag force? Your equation is correct, although I get 4.293 when I plug your data into it (probably rounding differences). I'm not terribly familiar with wind tunnels, but try checking the units of the readings that you're getting from it.