dj1001 :
5 x 40mm fans = 200mm of fanage
would have been better of doing what everybody else does and use 2 120mm
Are you sure?
40mm fan opening or area
3.14 x 20^2 (pr r^2)
1 x 40mm fan has a opening area of 1256 square mm
1256 x 5 = 6280 square mm
120mm fan area
3.14 x 60^2
1 x 120mm fan is 11304 square mm
This setup is closer to an 80mm fan then anything.
All this does not count the fact that with a 40mm fan the motor is much bigger compared to the blades. So both are actually less then the above numbers. Also, how thick is each fan?
More accurate would be with blade surface area.