Replacing Thinwall Electrical Tubing In The Mast


All mast wiring is protected by thinwall PVC tubing. The tubing begins about two feet from the bottom of the mast and goes almost to the top (about 6 inches from the top). It is riveted to the mast with aluminum rivets, which can easily be drilled out. You will need a partner who is very patient and innovative.

Necessary Parts:

-60 feet of pvc thinwall 1 ¼ – 1 ½ inch electric conduit
-PVC cement
-Aluminum rivets (look at the current size in your mast for this as you will need to use the same holes. My guess is they are about ¼ to 3/8 inch and should fasten material about ½ inch thick)
-a strong piece of wire about 8 inches long that you can both bend and hold something firmly. I used a coat hanger.
-narrow beam flashlight
-small tarp (to cover the mast stub so you can see down the inside of the mast.. kind of like the cover photographers used to use a 100 years ago)
-drill with the usual sizing of bits
-120 feet of strong twine
-sawhorses to support the mast (at least three good sawhorses that are at least four feet wide (I screwed 2x4s to mine to get the width))
-an electrical wire fishtape (available at Home Depot and other places in the electrical department).
-rivet fastening tool
– needlenose pliers and screwdrivers
-hacksaw to cut the pvc

1. When the boatyard is first pulling the mast, check to see if the conduit is really the problem. You can do this by having the pull the mast off the stub high enough so you are comfortable looking up the inside with a flashlight. You should be able to see all the way up the mast and conduit breaks should be readily observable. If you don’t see any breaks…. Well, then it is your call on whether to go forward, but I don’t think I would do this job unless I was certain there was a problem.
2. Have your mast laid on the sawhorses in an open area with the leading edge straight down. Make sure it is well supported and do watch you don’t damage your spreaders. I used my spreaders to ensure the mast was straight up and down.
3. Try to sort our your electric wires from the bottom of the mast as you will have to pull the wires going to your steaming light and radar (and any other wire that goes ½ way up).
4. Put tension on any lines in the mast so they cannot foul the wiring job.
5. Pull the wires that go ½ way up out of the mast at the ½ way point.
6. Drill out the rivets holding the pvc thinwall tubing. There were two rivets at each fastening point in my mast and a few were hard to see. I recall they were about 10 feet apart, but our masts do vary. Be careful to only drill the rivets and not hit your wiring (this is pretty easy as this is aluminum).
7. Double up your twine so you have a 60 foot piece with a loop on the end. Thread the twine successively through your pvc tubing.
8. Assemble the pvc tubing without gluing. Check to see the joints are not close to a rivet spot as the joints are thicker and will make it harder to rivet. You now have the “tool” to fish out the broken tubing.
9. Put the wiring through the loop of twine and get the twine loop over the first section of tubing in the mast. Carefully push the tubing up the mast until you are well on to one of the broken pieces.
10. Pull the loop tight and while holding the electric wires tight, pull the piece of broken tubing out. Note: this can be easy or hard depending on how broken up your tubing is and whether the broken edge catches a tangle of wire. Be patient.
11. Repeat this procedure until you have removed all the broken tubing. (I had six broken pieces and the last ones furthest up the mast were tedious to get to).
12. You are now ready to install the new tubing. First lay tubing next to your mast and drill the hole at the ½ way point so you will be able to align the tubing with the mast. Then assemble it with glue. Note: I filed and sanded the top of the tubing to ensure there were no sharp edges that could possibly cut the wire bundle.
13. Remove several of the line guides on the mast (you will use these spaces to hold the pvc down while you drill and rivet).
14. Start the electric wires down the pvc using the twine tied to the wire bundle as a pull.
15. Carefully begin pushing the pvc up the mast being careful to keep tension on the twine pull. Again, depending on twists in your wire bundle, this can be easy or hard. Don’t reef on the wire! Rather, rattle and twist the tubing, using the line guide holes to move around obstacles.
16. Once your ½ way hole is aligned with the hole in the mast, begin drilling and riveting the mast. Use the bent piece of coat hanger to hold the pvc against the mast as best you can for drilling. Be careful to not drill into the wire bundle!
17. Carefully pull on all the lines in the mast to ensure they are not between the conduit and the mast! Look with the flashlight as well. This should not be a problem if you were careful not to disturb them during removal.
18. In areas where this is not possible and on every riveting job, make a small hook out of the coat hanger and pull the pvc tight against the mast through the second rivet hole while you rivet through the first of the pair.
19. Thread the fish wire up from the bottom of the mast, looking through the ½ way whole and snagging the wire with your coat hanger tool. Tape the ½ way wire bundle to the fish wire and carefully pull the wires through to the end of the mast (You might have to tape each wire separately if there are large connectors).
20. Your done! Now carefully inspect your mast for cuts and scratches that can chafe or damage your lines and use this opportunity to clean/sand/paint the mast if you see fit.
21. Test the wires for continuity of course and maybe even replace the bulbs if the mast does not come down very often.

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