This is my all in one fan duct i created using a few other things to make it work on my Tevo Tornado.
Fan duct can be printed without supports and at 20% infill
The clamp with need supports and will need 40% infill
you will need 2 x m3 locking nuts, 2 x m3 30mm bolts, 2 x m3 8mm bolts, 1 x m3 20mm bolt , 12 x m3 12mm bolts 1x 30mm 24v fan, 2 x 40mm 24v fan
Update: I've now added a 40 x 40 x 40mm fan version i found that the 30mm fan was too loud and by adding the 40mm fan to the front it has cut the noise down alot ,
you will have to use supports to print the 40mm version though.
I've also added a picture of a stress test done with the fan duct to show what its like at bridging .
30x40x40mm fan duct needs 20% infill and no supports
40x40x40mm fan duct needs 20% infill and supports
clamp needs 40% infill and supports