Retrofitting masthead electrics - carbon mast

[Julian Merson]

I'm busy incorporating some simple electrics in Daisy III.  I saved an all round masthead white light (NASA) from my previous boat which it would be good to install but my carbon fibre mast has no electric cable installed.

The question, then, is whether anyone has successfully run a cable through an existing carbon mast and, if so, how did you manage it?  Threading it in the top is one thing.  Retrieving it at the other is quite another thing...

 I've had a good trawl through existing threads and it seems that most owners sensibly had their cables installed at the build stage.  I know of other boat owners who have run cables up a shroud and I could just about see how a cable could be glued to the outside of the metal track without causing too much interference.  But the neat solution is the inside route!

Any tips much appreciated.

[Graham W]

One tip that I heard that struck me as clever and simple was how to avoid clanking wire misery, once you had found a way in.  Attach long tailed cable ties all the way down the wire, all pointing in different directions and thereby keeping the wire from contacting the inside of the mast.  Not much help though if you can’t get in in the first place.

If you can get in at the top, attach a strong magnet to the end of the wire so that you can find the end (with another magnet) when it reaches the bottom?

[Matthew P]

Hi Julian
   
I had a similar problem installing a cable in an aluminium mast on another type of boat.  Are you able to unplug the top of the mast?  I fed my cable through by holding the base of the mast in an upper floor window and inserting the cable through the hole near the base to emerge through the top under gravity. My neighbors are used to seeing me do this sort of thing.

Incidentally, I presume you are cautious about drilling holes in the sides of the mast. Best kept small and avoided where the mast is subject to a lot of bending.   

Matthew
BR20 Gladys
 

[Graham W]

I fed my cable through by holding the base of the mast in an upper floor window and inserting the cable through the hole near the base to emerge through the top under gravity.

Ha! Successful lateral thinking by an engineer.

[Matthew P]

Ha! Successful lateral thinking by an engineer.

Graham: my thinking isn't lateral  - it's inverted! 

Matthew
BR20 Gladys

[Julian Merson]

Thanks Matthew and Graham for your replies.

There is already a hole in the top plug, added by the previous owner and I can only guess it was for some form of wind indicator flag/ensign.  There is no hole down the lower end, not even an exit hole for water - which seems to be there for some boats. 

If a cable can be passed through, I was thinking of  drilling a small exit hole somewhere below the pivot pin for the mast base/tabernacle, since I would think this very lowest area would have less structural impact than above the pin, but won't even go there if there's no access point to receive the cable.

Regarding that potential access point, both the upper and lower bungs are completely sealed in - it looks like some sort of epoxy, certainly well bonded.  So I think the only means of access might be to drill an inspection hole up through the lower bung and then ultimately to replace this once excavations are completed.  I wondered if anyone knew the thickness of this lower bung.  I have emailed the builder but everything is in lockdown and, apart from an initial acknowledgement from Lara, I've not had a response.

[Graham W]

Try the direct approach, Matt at [same address as Lara].

[Graham W]

In a spooky coincidence, I have a BR20 gunter rigged carbon mainmast for sale.  See the for sale and wanted section.

[Peter Taylor]

...There is no hole down the lower end, not even an exit hole for water - which seems to be there for some boats. 
....
  I wondered if anyone knew the thickness of this lower bung.  I have emailed the builder but everything is in lockdown and, apart from an initial acknowledgement from Lara, I've not had a response.

The drain hole for water is very small, you can see it in a photo in my blog at http://seatern.uk/2016/11/17th-18th-nov-sails-off-and-mast-drainage/ (click on photo to enlarge). I assume the drain hole is at the top of the plug and from the hole to the mast base is 50mm which sounds the sort of number Matt might have used on his CAD system! However my mast base fitting will be different from yours since it's part of my "mast lowering for bridges system" so your plug may or may not be the same.

Matt said he would use long cable ties on the cables through Seatern's mast as described by Graham and they do not clank around at night (I've experienced that "pleasure" on other yachts!). However if you only need to thread a cable for the Nova, as you will know it only needs a very thin 2 core cable. My inclination would be to glue it in the outside corner of the mainsail track and mast which might avoid future problems.

On Seatern the cable for the masthead NASA anemometer/vane developed an intermittent fault this last winter. I couldn't trace the problem so I've now fitted a NASA wireless anemometer unit. I think the fewer cables up the middle of the mast the better!

Peter

[Julian Merson]

Hi Peter
Many thanks for your reply.  Believe you me, your blog has been studied in great depth - it's yours and Julian Swindell's fault I have purchased the boat in the first place!   As a fellow blogger myself, these things are incredibly interesting and useful, not to mention dangerously persuasive!

Having now painted the mast in two pack black - one of the most recent improvement jobs - you can be certain that I have looked long and hard for the drain hole you mentioned and had already clocked your post and picture in order to try and locate it.  But it's not there on my mast....not in any discernible shape or form!

I think you are right, however.  A cable down the inside is probably unwise for just the two core job that's required and I am edging towards the gluing to outside of track idea.

[Mark Rushton]

On my BRe I have epoxied short 1” lengths of carbon tube to the mast at 1m intervals where the mast meets the mast track. I sized the carbon tube to fit the cable snugly and there are some cable ties around the cable to prevent it sliding up and down.

Before epoxying on the tubes I sanded off the paint on the mast locally to where I intended to glue each tube so I had a good bond.

If it stops raining tomorrow I’ll take some photos.

Mark

[Julian Merson]

Thank you Mark.  I'm intrigued to find out more.

[Mark Rushton]

Hi

I have attached a couple of photos showing the short lengths of carbon tube epoxied to my mast.

Mark

[Julian Merson]

Super.  Many thanks Mark.  That looks like a great idea.  I shall try something similar.