Thread: Flexy ducting

I buy from these guys.

http://www.ductsystems.com.au/index....ar-detail.html

You can also try Ezi-Duct

Have you see results of the flexy testing in this thread?
Air flow calibration measurements

BTW I just noticed a mistake in that post.

e.g. if a 5m length of flexy reduces the flow to 50% then another 3 m (i.e. 6m in total) will reduce the flow to 25% etc.

Should be
e.g. if a 3m length of flexy reduces the flow by 50% then another 3 m (i.e. 6m in total) will reduce the flow to 25% etc.

In that post you'll see that smooth bore does not seem to be as significant as "how floppy it is" probably because it vibrates and causes turbulence.
Ideally you want smooth bore and stiff tubing which is why solid pipe works best.

The floppiness of the flexy seems to become a bigger problem on longer lengths so minimising the length of flexy is the first thing to do.
Clamping the flexy down about every 300 mm will help a bit but then you might as well used PVC ducting.

Originally Posted by Lappa

I buy from these guys.

http://www.ductsystems.com.au/index....ar-detail.html

Is the Master PVC ducting, the one to go for?

That's the one I bought. I bought the 160mm ID as it fits snuggly over 150mm pvc Stormwater/DWV Pipe.

Thanks Bob
Interesting that the flexibility seems to have a greater effect than the roughness. Appreciate the input.

Tony

Originally Posted by Lappa

That's the one I bought. I bought the 160mm ID as it fits snuggly over 150mm pvc Stormwater/DWV Pipe.

Just asking the Brains Trust, which is better in performance and durability PVC v Polyurethane Flexible Ducting or Flexible Plastic Hose (ala Carbatec)?

Originally Posted by cava

Just asking the Brains Trust, which is better in performance and durability PVC v Polyurethane Flexible Ducting or Flexible Plastic Hose (ala Carbatec)?

I think the Carbatec stuff is just a flexible type of PVC.

For lengths under ~half a metre I don't think performance differences matter much - i.e. go the easiest and cheapest.

For longer lengths it depends on the thickness/stiffness and hence how flexible the ducting is with less flexible seems to have better performance.

In terms of wear, the thinner softer materials seems to tear easier and is more easily punctured but we are usually talking many years before replacement. One of my polyurethane (PU) hoses on my BS needs replacement and it is ~8 years old. Small leaks on inlet hoses are not important for loss of dust because the air and hence fine dust is going into the hose. More important are tears typically near junctions which lead to pressure losses. This seems to come down to material thickness with both thin PU and PVC being similar in tearing, maybe the PU is slightly better.

If you need super flexibility then I'd go for the PU.

The Master PVC Flexi hose I linked to has a thicker wall size and is less flexible than the Grey thin walled hose from Carbatec or Timbecon.
The thin walled grey flexy is easily pieced so you don't want to be dragging it across the floor or over objects. Mine hangs down so I can connect it to the table saw hood or thicknesser or router table or scms ie. designed to connected and disconnected which is a benefit of having it very flexible.. The Master PVC is permantely connected to the table saw.

I found that one of the most common places thin hose tears is when it is repeatedly placed over stiff pipe or a hose type clamp is used.
Using a threaded PVC coupler connection results in a compression fit so it's not being repeated stretched over PVC or metal ports and so is less likely to tear.
This also stops the end of the hose from getting ragged.

I make all my machine connections like this.
IMG_2041.jpg

As I don't have a lathe to cut the hole in the screw caps, I push the hose in and duct tape it.

IMG_0899.jpg

I have capped fittings at various locations so I can transfer the hose between points rather than have multiple hoses hanging in a small shed space.

IMG_0901.jpg