Prusa i3 Fan Duct for J-Head & Wade Extruders

Updated version is here: http://www.thingiverse.com/thing:201638

This is a(now outdated) quick variation of philsson's 40 mm fan duct. http://www.thingiverse.com/thing:184055

I've added a 9 mm by 16 mm opening to help provide cooling air flow to the PEEK body of the J-Head. The theory is that it would reduce the chances of PLA jamming. It may also be beneficial for use with ABS, but I'm not using it with that kind of plastic at the moment.