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dadankskunk
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Is this a viable flowhood? (Finished building, laminar flow achieved!)
#18895488 - 09/26/13 07:07 PM (10 years, 4 months ago) |
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Hello I was playing with flowhood designs. I already have both the flowhood HEPA filter and the fan, but not the supplies to put it together yet.
I was wondering if it was possible for me to make my flowhood using this design? Would appreciate your feedback, much love.

EDIT:
Hey guys, I built the flowhood based on the last drawing I posted, which is pretty much how everyone else has built theirs(notably Damion5050). It works perfect, inline fan is a beast, it's very quiet and stable, not loud at all. Will post pics when final touches are complete!
Edited by dadankskunk (09/29/13 05:20 PM)
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36fuckin5
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Re: Is this a viable flowhood? [Re: dadankskunk]
#18895677 - 09/26/13 08:02 PM (10 years, 4 months ago) |
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You'd want more of a plenum than that to create laminar flow. There are some great guides on making hoods if you poke around.
-------------------- Redd Foxx said: If you're offended I don't give a shit and don't come see me no more. Pat The Bunny said: A punk rock song won't ever change the world, but I can tell you about a couple that changed me. bodhisatta said: i recommend common sense and figuring it out. These are the TEKs I use. They're all as cheap and easy as possible, just like your mom.
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Amanita virosa
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Re: Is this a viable flowhood? [Re: dadankskunk]
#18895688 - 09/26/13 08:03 PM (10 years, 4 months ago) |
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The plenum needs to be at Least twice as deep as the filter. Most hoods use squirrel cage blowers instead of in line fans like you show.
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BL00MERS
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Re: Is this a viable flowhood? [Re: dadankskunk]
#18895706 - 09/26/13 08:07 PM (10 years, 4 months ago) |
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You already have the flow hood and the fan? I'm sure you mean HEPA Filter and fan.
Can you add the specs for your filter and fan? This is vital information in determining the question you are asking. I have only recently registered on shroomery, but have been growing for about 5 yrs. I still have a TON to learn, but recently built my own laminar flow hood that has been serving me very well...so maybe I could offer some guidance.
-------------------- Happy growing!
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BL00MERS
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Re: Is this a viable flowhood? [Re: BL00MERS]
#18895723 - 09/26/13 08:09 PM (10 years, 4 months ago) |
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-------------------- Happy growing!
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dadankskunk
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Re: Is this a viable flowhood? [Re: BL00MERS]
#18895831 - 09/26/13 08:26 PM (10 years, 4 months ago) |
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My Hepa filter , is 12" thick, size is 24x24", and has 1.3" static pressure My fan is inline, and blows at 810 CFM at 0", and blows 400 CFM at 1.5" static pressure. Also it's very quiet. 
So if I have a 12" thick filter, I'd need a 24" plenum? Thereby making my box at least 24"x24"x36"?
I'm going to do some searching about the plenum. I have some questions, such as, how strict is the "Twice as thick as the filter" rule? And how have other people figured out the size of the plenum required? Is it based totally on the thickness/size of the filter completely or what?
Quote:
You already have the flow hood and the fan? I'm sure you mean HEPA Filter and fan.
Haha yeah that's what I meant.
edit: I found this guy using the same size filter as me. He used a 12" plenum, claims his works fine.
Edited by dadankskunk (09/26/13 08:50 PM)
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kinkaku
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Re: Is this a viable flowhood? [Re: dadankskunk]
#18896040 - 09/26/13 09:12 PM (10 years, 4 months ago) |
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will an inline fan even work for a flowhood? its a question that has been bouncing around my head for awhile now.
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inski
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Re: Is this a viable flowhood? [Re: kinkaku]
#18896816 - 09/27/13 12:08 AM (10 years, 4 months ago) |
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Yes, it can work, my inline blower is mounted at the top rather than the back though.
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Amanita virosa
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Re: Is this a viable flowhood? [Re: inski]
#18897555 - 09/27/13 06:51 AM (10 years, 4 months ago) |
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Quote:
inski said: Yes, it can work, my inline blower is mounted at the top rather than the back though.
Yea, I think that is probably the ONLY way it will work.
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BL00MERS
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Quote:
Amanita virosa said:
Quote:
inski said: Yes, it can work, my inline blower is mounted at the top rather than the back though.
Yea, I think that is probably the ONLY way it will work.
Agreed. I use a large blower, not an inline, but it is also top mounted.
As far as the plenum goes, I have read conflicting information. I based my general design for the flow hood from http://www.orchideenvermehrung.at/english/index.htm
My filter is approximately 24"x18"x7" and my plenum is 10" and has great laminar flow with no turbulence or vortices. I concluded that a plenum 1-2 times the depth of the filter seems to be common.
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RogerRabbit
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Re: Is this a viable flowhood? [Re: dadankskunk]
#18897637 - 09/27/13 07:45 AM (10 years, 4 months ago) |
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Quote:
dadankskunk said:

Never have the blower aimed directly at the filter. The air should enter at a 90 degree angle to the filter.
The figure of 1.3 for resistance is worthless without the flow also listed. Most 12" thick filters have lower resistance and are for clean room use. Flow hood filters have higher resistance so they can build static pressure behind them to ensure laminar flow. They're also usually in the 5" to 7" thickness range. RR
-------------------- Download Let's Grow Mushrooms semper in excretia sumus solim profundum variat "I've never had a failed experiment. I've only discovered 10,000 methods which do not work." Thomas Edison
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JoeMama1992
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Re: Is this a viable flowhood? [Re: RogerRabbit]
#18897693 - 09/27/13 08:17 AM (10 years, 4 months ago) |
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Damion5050's homemade flow hood was pretty nice, definitely worth checking out.
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dadankskunk
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Re: Is this a viable flowhood? [Re: RogerRabbit]
#18898660 - 09/27/13 01:13 PM (10 years, 4 months ago) |
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Ok so main design changes would be, changing the orientation of the fan, which would then make the plenum about 13-14", the air would come in from the top of the box instead, and that's about it.
Thanks for all your feedback.
Here is latest design I put together, I'm going to do a bit more research, just to see what others have done, then I'm going to finally build the thing.

Quote:
Never have the blower aimed directly at the filter. The air should enter at a 90 degree angle to the filter.
The figure of 1.3 for resistance is worthless without the flow also listed. Most 12" thick filters have lower resistance and are for clean room use. Flow hood filters have higher resistance so they can build static pressure behind them to ensure laminar flow. They're also usually in the 5" to 7" thickness range. RR
The only thing about flow on my hepa filter says 1900 CFM test flow.
Edited by dadankskunk (09/27/13 01:18 PM)
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dadankskunk
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Re: Is this a viable flowhood? [Re: dadankskunk]
#18907971 - 09/29/13 05:12 PM (10 years, 3 months ago) |
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I did it! I have achieved laminar flow. 
I'm excited to start working with my new flowhood, thanks for the feedback you guys.
I'm gonna just leave the following information for future searchers who are looking into flow hoods.
I used a Flanders 24x24x11.5 HEPA filter, rated 1.35" static pressure which I purchased on ebay through fungi fun's flowhood build guide. I used a 10" inline fan made by a company called Tjerlund, which runs at 810 CFM at 0" static pressure, but 430 CFM at 1.5" Static pressure. My box is made of 1/2" MDF, it holds together really well.
The final dimensions of my box are
- (2)23 3/8 x 26 1/2 (Sides)
- (2)24 3/8 x 27 (Back)
- (2)23 3/8 x 24 3/8 (Top/Bottom)
I used a very wide wood with a large surface area to fit behind the filter, to make sure it didn't budge. The wide surface area should prevent it from moving completely. I left about 2" space in front of the hood, and chose to use 2x2s to prevent the hood from falling forward, and to hold it in place, and to seal any left over gaps that may still be present.
Everything fit alright. The cuts didn't align exactly perfect, and there were small gaps that I had to make sure were sealed, both inside and out, because of that. I'm not sure how to avoid this, it seems inevitable for any project, you just have to work with what you got I guess.
Edited by dadankskunk (09/29/13 05:18 PM)
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