Nice build ! Have you tested the airflow with smoke, or something else ? I'd suggest you to place the exaust duct closer to the center, rather than the corner. Also, if you added a baffle (a woodboard that restricts the airflow) at the back of the hood would make for more efficient design (assuming your extraction fan can pull enough CFM of air for the size of hood).
Hi Ryan! I tested the airflow with a kimwipe that I dangled along the length of the sash opening, and it looked like there was reasonably good airflow into the box the whole way along. I agree that a centered duct and baffle could have made it even better, but I wanted to keep things simple. Having the air duct on the left side of the box lets me put lots of crap on a second silicone mat located on top of the box for easy access. I would probably have some concerns about building a fume hood for seriously toxic stuff, but this build seems to work great for most of the nuisance fumes that I was concerned about.
@@CoolNamesAllTaken Looks quite promissing. Good luck with your projects ! There's a quick formula for calculating the face velocity of your fumehood (ft/min), using the CFM rating of your exaust fan, and the sash opening height : Face velocity (ft/min) = CFM rating (ft³/min)/Sash opening surface area (ft²) Ex: For a face velocity of 100FPM (usual), and a fumehood sash area of 4.5 square feet (lenght × desired sash height), your fan will need to pull 450CFM (at least). This is a general formula, but as a rule of thumb, keep the sash height no more than 18" (45cm).
@@Ryan-lc4bl Sweet, looks like I am in the right ballpark! Fan is 400CFM and the box is around 4ft wide. I usually keep the sash open less than a foot so that meets the 100CFM face velocity pretty nicely.
Connecting the fan motor to the end of the duct leaves the majority of the duct at negative pressure, so you're less likely to get emissions into the room from a leak in the duct. Connecing the duct to the corner of the hood gave me more space to put a second silicone mat on top of the fume hood, which is where I store a bunch of my crap :)
Inside height is 27.25in, full plans and cut list are available in the github repository (sized for North American lumber with Imperial dimensions) github.com/CoolNamesAllTaken/fume-hood/blob/main/solidworks/fab/drawings/cut_list.pdf
Is there a guide to build this fume hood?
Yes! Step by step assembly and part drawings are provided here: johnmcnelly.com/fume-hood/
Nice build ! Have you tested the airflow with smoke, or something else ?
I'd suggest you to place the exaust duct closer to the center, rather than the corner.
Also, if you added a baffle (a woodboard that restricts the airflow) at the back of the hood would make for more efficient design (assuming your extraction fan can pull enough CFM of air for the size of hood).
Hi Ryan! I tested the airflow with a kimwipe that I dangled along the length of the sash opening, and it looked like there was reasonably good airflow into the box the whole way along. I agree that a centered duct and baffle could have made it even better, but I wanted to keep things simple. Having the air duct on the left side of the box lets me put lots of crap on a second silicone mat located on top of the box for easy access. I would probably have some concerns about building a fume hood for seriously toxic stuff, but this build seems to work great for most of the nuisance fumes that I was concerned about.
@@CoolNamesAllTaken Looks quite promissing. Good luck with your projects !
There's a quick formula for calculating the face velocity of your fumehood (ft/min), using the CFM rating of your exaust fan, and the sash opening height :
Face velocity (ft/min) = CFM rating (ft³/min)/Sash opening surface area (ft²)
Ex: For a face velocity of 100FPM (usual), and a fumehood sash area of 4.5 square feet (lenght × desired sash height), your fan will need to pull 450CFM (at least).
This is a general formula, but as a rule of thumb, keep the sash height no more than 18" (45cm).
@@Ryan-lc4bl Sweet, looks like I am in the right ballpark! Fan is 400CFM and the box is around 4ft wide. I usually keep the sash open less than a foot so that meets the 100CFM face velocity pretty nicely.
Is there an advantage of not connecting the fan motor directly to the top of the fume hood and why in the corner and not the middle?
Connecting the fan motor to the end of the duct leaves the majority of the duct at negative pressure, so you're less likely to get emissions into the room from a leak in the duct.
Connecing the duct to the corner of the hood gave me more space to put a second silicone mat on top of the fume hood, which is where I store a bunch of my crap :)
What's the inside height of your fume hood?
Inside height is 27.25in, full plans and cut list are available in the github repository (sized for North American lumber with Imperial dimensions) github.com/CoolNamesAllTaken/fume-hood/blob/main/solidworks/fab/drawings/cut_list.pdf