DIY Flexible air duct

Tools and guide for making custom 25mm reinforced spiral hoses/air ducts

These are tools I've used to make the flexible ducts for my Kobra 3 cooling upgrades.

I've switched from a second layer of fabric to Automotive tape, I think double fabric is a bit too stiff.

Materials you'll need:

• 25mm PVC-Pipe
• Waterproof fabric
• Superglue
• Automotive cable wrapping tape
• Silicone spray
• ABS/ASA or any high temp filament

Tools you'll need:

• Knife or scissors
• Small saw
• 5mm drill
• 6 printed clamps
• 1 printed winding guide

Get a PVC-Pipe that's about 10cm longer than the length of the hoses you want to make.

You can use a shorter pipe but it's going to make everything a lot more fiddly and annoying.

Clamps and winding guide:

Print a few of the clamps and the winding guide and make sure that the internal threads print cleanly.

I recommend about 5 or 6 clamps per meter and a few as spares, they break if you squeeze them too hard.

PVC-Pipe:

Cut one side of the pipe across the entire length as straight as possible and drill two holes about 3cm from each end.

This is very important! Otherwise you won't get the hose off the pipe after winding it with tape.

Fabric layer:

Use the pipe to mark and cut the fabric, I recommend about 10 to 15mm overlap and make sure that the rubber side is outside.

Cut the fabric to length and apply some glue to each end. Make sure you don't get any glue on the pipe and

that the ends are straight. If you want to use silicone spray, don't use too much,

just spray it on a towel and use that to apply it to the pipe in a very thin layer and make sure none gets on the seam.

You could wind the fabric around the pipe in a spiral,

but I've found that the hoses you make this way are way stiffer than a single layer.

Make sure the fabric isn't sticking to the pipe. If it does twisting it a bit should help.

Spiral reinforcement:

Feed your filament through the winding guide. You can bend the end a bit.

Wind the the filament 1 or two times around the fabric layer and apply some glue.

The holes help keeping it from unwinding. When the glue is dry you can cut the end off and clamp it.

Turn the pipe and wind on about 10cm of filament.

Apply a bit of glue around the filament spiral. I did it for every revolution and in a NSWE pattern.

I recommend to only do about 10 to 20cm at a time.

The end can be a bit tricky just go slow and wait for for the glue.

Outer tape Layer:

!! NEVER WRAP THE WHOLE PIPE AT ONCE !!

Make sure that the previous layers aren't stuck to the pipe,

if they are and you start wrapping the hose will never come off.

Start wrapping the tape in the opposite direction of the spiral and never do more than 10 cm.

Pull a bit of hose off the pipe and wrap the next part,

repeat until the whole hose is wrapped in tape.