Step 1: What you'll need
A foot of 3 - inch diameter PVC tubing
A 3 - inch diameter computer fan (mine was 12V)
An AC/DC adapter, with a DC output the same as your fans
Filter for a room air conditioner
Hose clamp for the 3 - inch pipe
I already had the fan and adapter laying around, but everything shouldn't cost more than 20 dollars.
You will need the following tools:
Drill and various bits
Soldering iron + solder
Hot glue gun + sticks
Step 2: Preparation
Next, make one larger hole in between the two smaller ones to accommodate the toggle switch.
Step 3: Assembly pt. 1
The twist and solder each of the positive wires to the prongs of the toggle switch. (Positive on the adapter has a white stripe)
Step 4: Assembly pt. 2
Then, place the fan on the top, make sure its centered with the air flow going AWAY from the pipe, and hot glue the corners down. Then, form a nice tight seal around the edges of the fan and pipe.