Oct. 16 2012: I've put a new one up now which is wider and puts out more air. Also necessary for the V2 nozzle. http://www.thingiverse.com/thing:32491
Dec. 9 2011: Put another version up with about 1.5mm more clearance from hot parts.
Nov. 22 2011: Added bracing and thicker mounting strip to support the fan better. Removed some plastic from the side so that the Nozzle at the back stl would not hit the z stage at the back. Provided stl for nozzle at the back fitting.
Provides air from the supplied fan to the filament and surrounds and mainly avoids the heater tip.
Max air by getting mounting bolt out of the way and facing more direct.
3mm clearance to hot things and platform.
I have trialled similar one at 2 to 2.5mm for a while but I do print at fairly low temps.
Download the stl for your nozzle position, front or back.
Print the way the STL is facing, it has about a 35 degree overhang.
Print the spacer shorter if you already have something on top. See top view pic. This was scaled 0.4 in Z as I already had a 6mm thick Bowden Clamp thing on.
Face fan the right way around and screw onto duct with nuts at the top, back right single screw first.
Remove front mounting bolt nearest to front and put in spacer.
Screw on nuts (front one first).