PEX tube conduits for control lines?

Russell Brown

Super Anarchist
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Port Townsend WA
I've done it on a surf ski for the rudder control lines that run inside the hull. Worked great. It's slippery on the inside and if you rough it up a bit, it seems to glue okay.

 
I'm thinking of the traveler control lines on a small daysailer.  I want them to be accessible in the middle of the boat.  Thought I'd G/Flex the ends of the conduit into counterbores.

 

European Bloke

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I'm feeling the friction from here.  That's after you've managed to get the lines run in.  Google, 'replacing internally routed bike gear cable' for inspiration.

 

El Borracho

Verified User
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Pacific Rim
PEX has a low melting point. That will be the issue if there is sufficient motion, tension and contact at a bend. Are not most control cables lined with some high temp plastic more like Teflon?

 

European Bloke

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PEX has a low melting point. That will be the issue if there is sufficient motion, tension and contact at a bend. Are not most control cables lined with some high temp plastic more like Teflon?
And surrounded by a steel casing.

Don't underestimate the forces involved. People don't rig boats like this for a reason. Actually people don't do this for a whole list of reasons.

 
To fill in some details, I calculate that the load on a traveler whip will be around 15 lbs.  It’s a small boat.
Ordinary Home Depot PEX  is rated for 80 psi at 200 degrees  f.

Still trouble?

 
I'd focus on the fixings at the ends.  They'll need to be solid, and the lead in angle needs to be fair.
Yup.  The ‘abutments’ bear the load on the line and need to provide a fair lead for the line as it exits the tube.  I’m thinking they might be machined from UHMWPE or PTFE or incorporate low friction rings. 

 

Haligonian Winterr

Super Anarchist
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Halifax, NS
We use them for the ballast valves on our boat, and they work well. 100% fair lead into them though, and Dyneema inside. Ends scuffed and glued in with Sika and appropriate primer. 

HW

 

Russell Brown

Super Anarchist
1,699
1,312
Port Townsend WA
There are lots of curved plastic conduits in my boat made from PVC pipe. Most of them take a bend of 90 degrees and produce little friction. The big ones are centerboard controls and the smaller ones control water ballast. They are all glued into the boat (10 of them) with epoxy at both ends. PVC is cool because it can be heat formed, but there are different types of PEX, some much stiffer than others. PEX seems to glue well with G-Flex. I just roughed up the ends, but one could follow the directions and flame-treat before gluing for an even better bond.

 

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