I am trying out this little beauty right now and it has definitely improved my extruder's ability to bridge.
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www.thingiverse.com]
It simply ducts air from the 40 mm fan that cools the extruder's hear sink and directs some of that air underneath the hot end. The openings of the ducts do point at the hot end but don't seem to be having a detrimental effect on its performance.
I printed this test bridge (http://www.thingiverse.com/thing:210675) and was able to defy gravity for 40 mm.
