I needed a window vent for something that pushes 22 CFM at approximately 10 feet of ductwork. I didn’t need to make it complicated. The next step is to print, paint, and air-tighten the parts. 4 segments for a 46″ Vertical Window. According to the math, I have a sub-fan rated at 32 cfm going into a main fan at 318 cfm, then fed through a tiny 22 cfm exhaust port in a 10-foot duct system. It’s interesting how each duct dimension affects CFM, but this is all theoretical math.