# how long a duct do i cut?



## zem (Feb 27, 2015)

so i got a 10 ft 4" duct that i want to cut to pieces of curved duct and make lightproof passive intake holes in the flowering chamber. question is, how long do i need to cut the duct to achieve a lightproof curve? the the duct is black from the inside. would 1 ft suffice? i need to begin cutting, so all help is appreciated ASAP, thanks!


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## Hackerman (Feb 27, 2015)

I just put a piece of that black carbon filter in front of the intake and it blocks the light just fine. I must admit, I use 2 layers in one location.

If you don't want to block the intake with the carbon filter, make a box setup. I don't think a lot of curves in ducting is a very good idea. Especially if you're starting with only 4". JMO


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## zem (Feb 27, 2015)

Hackerman, the carbon filter sheets have only one problem, that they restrict airflow and with time they will clog more and more from dust. I tried them on my dehumidifier, and they diminished its airflow by at least 50% so i removed it. I am planning on making smooth curves  to minimize the obstacles for the air, and making a lot of those like 10. I give a great deal of importance to using my fans to maximum efficiency. I hate it when I close or open any door in the growroom and hear the fan noise go up or down due to air restriction...


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## Hackerman (Feb 27, 2015)

I definitely agree. When I cover the intake with the carbon filter, you can hear the fan slow down, as well as the suction holding the carbon against the tent intake.

However, I use a CanMax 3 speed 320cfm fan for intake so I am wayyyyyy overkill anyway. And, it will probably reduce the life of the fan but I don't care. Like you said, it does bug me a little but that it's not the greatest resolve but it's just temporary so I don't mind. If I had a problem with light and intakes, I would probably go with the box design. Probably the most efficient in terms of air flow.


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## Hushpuppy (Feb 27, 2015)

I would say to cut the 10' piece in half and connect the 2 5' lengths to 2 separate vent ports with half of the hose outside the space and the other half inside the space. Make each piece form an S at the vent port and just allow them to lay on the floor or some location that is out of the way. I don't think having several turns in the hose is necessary given that it is lined with black on the inside, but once you have them in place, test their light blocking to be sure and if you have to, you can make another turn in each hose to cut the light intrusion further. 

While having multiple turns in the hose will reduce the air flow to a degree, it won't be enough to be noticeable because of the nature of vacuum on the system which pulls air in rather than pushes it. The function of pulling the air is more efficient than pushing so multiple turns should not result in enough loss of flow to matter.


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## zem (Feb 27, 2015)

wow 5' runs for a 4" duct sounds like a long duct, and 2x4" holes definitely don't give me enough intake. i was thinking of 10 and putting 10x5' ducts will make my cranked growroom look like a multi-legged alien or mutant LOL let alone the cost of buying 4 more of those ducts. I came up with an idea which i guess will cut it. I will make just 1ft curves, then I will place sort of a black box over them keeping all its sides well open, in a way where only light that is reflecting off the black box interior can go through and the 1 ft curved black duct should be more than enough to deal with that much light residue. i have a perfect place right under my dehumidifier where i can make all this, jeez this room keeps getting better


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