Sharp turns in dust hose when using shopvac

[Michael Jasper]

Hi - I've been trying to improve my dust collection. Using a shopvac plus dust deputy, and a mix of hoses. I have the soft spiral 2 1/2" hoses that compress insanely when there is resistance, an OEM hose of the kind that does not stretch or compress, and some small diameter hoses for connecting to small power tools.
In terms of "standing" machines - I've got a Dewalt job site TS with a 2 1/2" dust outlet, a miter saw with a 1 1/2" (approx) connector, router table and belt/disk sander with 2 1/2" fitting. My planer and jointer both have bags they eject into so I don't currently connect to the shop vac.
The only tool with a 4" fitting is a Laguna 14" bandsaw which I don't have yet.

My question is about abrupt turns. I know that sharp turns increase resistance a lot and are to be avoided. The very soft expandable hose I have tends to form pretty abrupt turns hanging off things like the TS, Router, etc. Flops straight down at exit and again when it hits the floor makes right angle. I was considering getting some elbows, formable hoses, and assorted other fittings to make sure the turns are gradual. But I'm wondering if that's as important when using a shop vac as it is with a regular dust collector. I was surprised that even the dust deputy tends have pretty sharp turns. All those spiral hoses are probably creating a lot of resistance as it is, and my understanding is that shop vacs have high Static Pressure - but low air flow volume.

Is minimizing those sharp turns going to make a noticeable difference in this situation? I'm wondering if it's more of an issue with high volume, low SP systems.
The tools that seem to have the least effective dust collection are the miter saw (I know this probably requires a high volume system to work well), sometimes the router and sometimes the table saw. (Table saw has two dust collection ports - one on motor and one on blade hood. When I remove the hood to use sled, that port is just wasted suction of course, but I've never seen a blast gate for 1 1/2" hose.

Thanks much!

[Alan Schwabacher]

You are correct that flow resistance is a much bigger problem for a low pressure high volume system like a DC than it is for the high pressure differential low volume shopvac. Minimizing flow resistance can't hurt, but if you want to test that, get some 2" diameter rigid PVC and connect it with shorter flex at the ends. The straight smooth walls have quite low flow resistance, it's cheaper than any hose, and if you like it you can set up runs around your shop with blastgates and hose connection points. I did that for convenience and sound reduction, but it does work well.

Small leaks are a much bigger problem for a shopvac, but leaks after the cyclone are worse than before it in either system.

[Michael Jasper]

Thanks Alan. When you say leaks after the cyclone are worse than before...is that from the shop vac's perspective? Meaning leaks between cyclone and tools are worse? Or leaks between shop vac and cyclone?

[Richard Coers]

You really have 2 problems. If I remember right, 1' of flex hose is the same as 10' of rigid pipe. And if that soft hose is basically bending directly in a 90 degree bend, that's probably the same as another 10' of rigid pipe. The table saw will probably be your main issue when ripping long boards and making it move long stringy sawdust down the hose. The band saw can do the same thing. The fine dust makers are no issue.