Layer cooling fan duct for Da Vinci 1.0 3D printer with the E3Dv6 mod

After installing the E3Dv6 hot-end on my Da Vinci 1.0 printer using my [thingie:707530](http://www.thingiverse.com/thing:707530), the next logical step was to create a suitable active layer cooling fan for PLA (and also for ABS, when it's really necessary).

While initially I attempted to modify some of the already existing designs, with varying degree of success, eventually I figured that it'd be better to start from scratch and model a custom fan duct that would blow as close as possible to