Dust Collection Piping

[Peter Christensen]

Ed sorry for the misunderstanding but I'm not using sheet metal. I'm using plywood and if I have to, MDF, but I'd rather not use that stuff. 1/8" plywood a couple three layers thick, bent to form the outside/inside curves and 1/2" or 3/4" plywood for the sides. That's what I meant by sheet goods.

I know the PCV fittings are painful. One place quoted an 8" to 6" wye at $250 each because they said it had to be custom made.

[Julie Moriarty]

Julie, how do spot static buildup? I think I used PVC pipe for my setup, it's a white pipe anyway.

Dust particles standing up on end all along the pipe. And when I wiped it off, I heard the static.

[Joe Wood]

OH good I never see that on the piping, thanks Julie!

[Randy Heinemann]

Ed I gave up the idea of the PVC especially with the cost of fittings that I didn’t mention. Pretty much ruled out the metal for cost reasons. I’ll be spending some time making square ducting out of sheet goods, much of which I got for free. Already figured out how to make large radius elbows and wye’s with the blast gates incorporated. I used the calculator I linked earlier to compare the losses to round and there isn’t even a 1” difference. The CV-Max will handle it easily. Shop is 635 sq ft.

Not sure about how you would calculate that. I just don't know. However, I would say that, unless you can find some way to make the inside of the plywood smooth there would be additional air movement reduction just because of that. I also am skeptical that a square duct would not make a significant difference in air movement but, as I said, I'm not an expert and have no idea what the methods are to compare round with square.

[Peter Christensen]

Not sure about how you would calculate that. I just don't know. However, I would say that, unless you can find some way to make the inside of the plywood smooth there would be additional air movement reduction just because of that. I also am skeptical that a square duct would not make a significant difference in air movement but, as I said, I'm not an expert and have no idea what the methods are to compare round with square.

In post #3 above I take the calculator and plug in any dimensions I want to check with round pipe and push the calculate button at the bottom of the page, write down the figures or print. Then I go back and change to a square duct only and recalculate and compare. There isn't much difference. Examples below.

Round pipe, 8', Galvanized metal (gotta pick something as they don't have wood), 1800cfm (little low for my CV-Max but I'll err on the low side), 50' of duct (my farthest run), five elbows, stamped, R/D of 2.0, elbow sweep 90*. Calculates Total duct losses inches water as 3.507"

Rectangular, 7" x 7", Galvanized metal, 1800cfm, 50' of duct, 5 elbows, aspect ratio (w/d) 1.0, R/D 2.0. Calculates Total duct losses inches water as 4.149"

So that's comparing apples to apples as close as I can. A little over 0.6" difference is pretty good. In reality you won't really find a difference between the two and with wood I can make larger radii that what can be bought in round. The surfaces of the duct will be sanded and painted with gloss to reduce that drag as much as possible. I'm debating on using a static dissipating floor paint but it is expensive, $150 to $200 a gallon. I don't think static will be much of an issue with wood though.

[Matt Day]

I built out a shop for a client/friend with snap lock. Since it wasn’t my money and I bought a 5hp Oneida Gorilla already, they designed a duct plan too for free. Here’s the warning - nothing is free!!! You’ll pay for the duct plan by way overpaying for the ductwork. And I ended up making changes to the plan anyway.

When I build my system soon, i’ll buy snap lock locally from a sheet metal supplier, and fittings from Kencraft. Will still likely buy the DC from Oneida though.

[ChrisA Edwards]

Had I known about KenCraft .....

Thanks Julie, also didn't know anything about them. Just ordered some ducting.....

[Matt Mattingley]

Plastic is just not cheap in my opinion. I have now started resorted to Leavalley for their flexible hose as they have a small ground wire within not a cheap piece of plastic wire. I personally use spiral ductwork and custom made elbows Y,s and connections. They run me $20-$30 each. I use the self cleaning gates aluminum from Leavalley. I get a few shocks from a 5 inch flexible pipe that does not have the ground wire. Will replace it one day.