I'am currently building a forced air solar thermal collector and here in Germany you can get HT-pipe (waste water pipe) really cheap so I thought, time for some unintended use as an air duct.
I will be using an old 80mm fan I scavenged from an old PC-PSU to create the needed flow of about 50m³/h. Since I did not want to use hot glue or duct tape (although this would have been the use case duct tape was designed for) to connect the fan to the duct work, I decided to make the fan part of a pipe. Just like you got powered mine cart tracks in Minecraft I now got a powered HT-Pipe :D
You will need the following:
-optional: 4xM3 washers
-one 75mm lip-seal (as seen on the pictures)
Print the upper part of the female connector with your cooling fan maxed out (75° overhang)