I designed this blower duct as I found I liked to see what was going on.
I was using a Active Cooling Fan Duct for Replicator 1 / Duplicator 4 / FlashForge http://www.thingiverse.com/thing:295317, Which worked great but it blocked the view from the front.
This blower moves much more air then the 40x40x10 fan used previously so cools much better, great for larger overhangs. But the downside is it is a bit noisier as well.
Can be printed without supports (may need some other form of cooling).
Fan used is a 50x50x20 raidial fan bought from here: http://nz.rs-online.com/web/p/blowers/0126414/.
This is a 12V fan so I am using a separate power supply until I can source a 24V version.
The mounting clips are not perfect, and the major part I am still tinkering with, but does hold it in place.
Its much easier to remove the extruder before mounting the blower and duct.