bends in your ducting

So how bad are bends or angles in your duct work? I guess as far as if I hook a fan up and do a 45 degree or 90 degree turn in it how much will it affect the CFM rating of the fan. As a bonus question how about a fan and the length of the ducting......


Thanks for any help

i dont think there is any magic formula, but the longer, and more bends, the less air flow

There is a mathmatical answer. It is hidden in these pages. I read it not to long ago. A little depressing if you are like me and for the sake of low money to invest you learn the truth about how much those bends and angles murder your cfm's. Keep looking you will find it.