What type of cable for masthead tri-color + Anchor ?

[aidancoughlan]

I've not been able to find any marine quality 3-core cable for my masthead light - will I get away with a roll of Artic cable from B&Q ?

ps. The old 3-core cable looks like 1.5mm2 - I havn't done the maths yet, but this sounds big enough for masthead light - what do forumites use ? I need 3-core one for the white anchor light, another for the tricolor, and a single negative return.

 

[MasterofHera]

If you cant find 3core use twin core and join up the black or blue (negatives) QED.

 

[Chrusty1]

Make sure that whatever you use is tinned wire, or it will corrode very quickly and you will get high resistance at all you connections and joints.

 

[Twister_Ken]

I used B&Q pond lighting cable. I'm attaching an article that comes from a CA source about sizing mast cables so as not to grolloch your light output.

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Who Stole My Volts?

Ted Osborn

One of the lessons from the Ouzo tragedy was the point, strongly made by the Marine Accident Investigation Branch, that yacht tricolour lights can be very difficult to see. If you only show a tricolour light at night when sailing you might be almost invisible.

With this in mind, when my mast was down to replace rigging I looked closely at my tricolour. 15 years old, the lenses were clouded badly. UV light had caused them to degrade and it was no longer giving out the amount of light it was designed to. With that MAIB report in mind, action was called for.

Replacement lenses were not available, even from the manufacturer: I had to buy a new light. Research produced a choice of branded replacements: Hella, Aquasignal and Lalizas, plus several which were unmarked and anonymous and didn’t claim to meet IMO regulations and were clearly to be avoided. Joining that list, but perhaps only for the moment, are LED navigation lamps. These offer the brightness required by the regulations but seem not to cover the vertical angles to cope with heeling and maybe don’t have consistent 360 degree coverage. As far as I could find out none are yet approved by any maritime safety agency.

At least one manufacturer is now marketing replacement tricolour bulbs in the form of a plug-in LED unit that looks a bit like a pineapple. If the angle-of-coverage problem can be solved this may eventually be the way to go. But for now a traditional branded tricolour was my answer

While checking the condition of my tricolour I measured the voltages on the circuit. At the battery there was 12.8 volts – very healthy. At the foot of the mast there was only 11.9 volts, almost a volt had gone missing. This showed that the wiring from the battery through the tricolour switch and to the mast was in poor condition. But there was worse to come: at the top of the mast the tricolour terminals themselves were getting only 10.7 volts. Another 1.2 volts was being lost in the mast. However good the battery and lamp, the wiring was preventing nearly 17% of the power from reaching the top of the mast. The wiring had to be changed as well.

There is one major cause of this: copper wire and connectors exposed to salty air. How often do you see unprotected deck connectors totally uncovered when a mast is down for the winter? How often do you see exposed deck connectors when the wire can so easily be led through the deck and the connection made at a proper junction box just inside? How often do you see bare screwed connections instead of proper sealed efforts? Did you know that corroding moisture can wick its entire way up the mast inside the insulation in only five years?

Lamp bulbs are very sensitive to changes in the supply voltage: light output falls proportionately to the 3.4th power of the voltage. This means that a loss of only 5% in voltage reduces the light given out by about 20%. The light will appear to be ‘on’ but it is nowhere near as bright as it should be. In my case, losing 17% of my volts was cutting down brightness by over 50%, even before the degraded lenses did their bit.

If you are checking your own tricolour circuit – and I hope you are – don’t forget that you must have the light on and working. You are looking for the voltage drop which occurs under load. No load means no voltage drop so ‘open circuit’ measurement is pointless. Use an ordinary digital voltmeter.

My mast is 35 ft tall and there is 20 ft between it and the battery, via a couple of connectors and switches. Thus 110 ft of wire is needed to give the flow and return circuit required.

Lloyds and the American Bureau of Shipping give advice on selecting the right wire to use. Firstly, it must be ‘marine quality’ wire. The insulation must be UV resistant and the copper must be protected from atmospheric salt corrosion. The wire itself has to be ‘tinned’ to prevent wicking of salt and the terminations at switch and wire should be sealed. It must be strong and flexible enough to withstand the constant movement and vibration within the mast. Domestic cable bought from a DIY shop or motor-parts supplier won’t do.

Whatever the wire, it always presents a resistance to current passing along it and this determines voltage drop. Too much resistance means too much voltage drop. The thicker the wire, the less the resistance - so always choose a thicker wire if given the choice.

To calculate the size of wire you need to know the electrical load or power that the lamp will draw (probably 25 watts) and convert this by Ohms law to amps of current. The length of wire from battery to mast head is also needed and this must be doubled since the current has to flow back to the battery to complete the circuit. The permissible voltage drop has to be decided as well. At this point, your eyes may begin to glaze over. Not a problem if you’re a member of the Cruising Association – we’ll happily send you an Excel spread sheet which lets you work out what size of wiring you need. If you’re not a member of the CA (and if not, why not!) then you’ll have to fall back on specification charts given by wiring suppliers and do you own sums.

In my case the total permitted resistance in the wiring is 0.24 ohms. Only once I get past 3 mm² wire am I OK, since with this can go up to 129 ft without creating too much resistance. Effectively, though 2.5mm² would cause a total voltage drop of .6V, so I could decide to go down one size and still retain almost all of my tricolour’s brightness – the choice might depend on what tinned wire is in stock when I place my order.

If you sail at night, this is not a job to ignore, and it can even be tackled mast-up if you’re happy aloft. The consequence of not being seen by shipping is not a pleasant alternative.

(ends)

(box)
Ted Osborn is a member of the Cruising Association’s Regulation and Technical Services (RATS) committee. The Cruising Association is dedicated to supporting cruising sailors, whether inland, coastal or offshore, sail or power. It organises on-the-water and onshore events, summer and winter, in UK regional centres, in the Baltic and the Mediterranean, and it provides much more, like local harbour representatives, a passage planning library, discounts on charts and pilot books, etc. Its website is at www.cruising.org.uk. CA members can obtain a copy of Ted’s spreadsheet by emailing office@cruising.org.uk.
(box ends)

 

[PetiteFleur]

Agree with chrusty1, make sure you use tinned copper wire, 1.5mm² should be OK. Try people like Maplins or other electrical supplier, but you may have to buy a 100m reel. Just checked with rs-online and it's £83 !! Try a local electrical distributor and they will advise. I bought 50m several years ago from a distributor and from memory paid about £20 but they did have to order it in for me.

 

[VicS]

Arctic which remains flexible at very low temperatures or just the ordinary domestic stuff but the trouble is that they are not tinned.

If you really must use the tinned stuff (ordinary non tinned domestic stuff seems to have lasted for 30 years for me) then its available in 2mm² and 3mm² from Merlin Power store

 

[Bilgediver]

Although tinned wire is preferable if you can find it you will find untinned will give good service if the connections are greased. However what is of more importance is size. Although 1.5 mm2 is shown as the correct size for current carrying you need to ignore this and place more importance on voltage drop hence the answer to your question is Yes the arctic grade cable 2.5mm2 min will do very nicely even if sold for 16 amp mains systems and yes it is as flexible as wire approved by lloyds...dnv....and ABS who incidentally do not demand tinned wire. and are more interested in the properties of the insulation and armouring/shielding if present. Lloyds..DNV and ABS rules do not apply to you so it is a bit of a red herring.

 

[billcowan]

Sure its better to use tinned, but as long as the ENDS are tinned (when new, using a soldering iron) then its every bit as good - at least for the first 10 years.

I've heard all the stuff about solder joints being brittle, but I have never had a problem, and as far as resistance, electrical & corrosion are concerned, you cant beat it.

I keep a soldering iron on board and solder every joint I can, and where I cant I tin the parts that join. (e.g. the plain brass spade connectors at the back of the fridge, or the plain brass contacts in the VHF's fuseholder)

A joint can be unsoldered or resoldered just about as quick as you could unscrew a clamp.

Insulation can be PVC tape - its only 12 volts after all, or if you want to be snazzy, electronics places sell sleeving that shrinks on tight with the heat of the soldering iron held near, or a fag lighter.

As far as size of cable is concerned, as has been said - heavier the better, but 'mains' stuff from B&Q etc has far too bulky insulation. motor factors sell 12v stuff in all weights and 5mm is the same outside diameter as mains 1.5mm.

Another tip: securing cable. you can't drive cable clips into GRP! so I use a hot glue gun. Its also easy to peal the wires off if you need to. In places where you can't conceal wires it gives a neat finish.

 

[aidancoughlan]

[ QUOTE ]
15 years old, the lenses were clouded badly. UV light had caused them to degrade and it was no longer giving out the amount of light it was designed to.

[/ QUOTE ] That's been the case with mine too - dont know how old it was, but the lens case had split in two and sikaflexed together with jubilee clip by the previous owner, it was clouded so badly it must be compromised.

[ QUOTE ]
Another tip: securing cable. you can't drive cable clips into GRP! so I use a hot glue gun. Its also easy to peal the wires off if you need to. In places where you can't conceal wires it gives a neat finish.


[/ QUOTE ] Sounds like a good tip for interior wiring - cant see me getting inside the mast with a glue gun though !

[ QUOTE ]
Make sure that whatever you use is tinned wire, or it will corrode very quickly and you will get high resistance at all you connections and joints.


[/ QUOTE ]
[ QUOTE ]
Agree with chrusty1, make sure you use tinned copper wire, 1.5mm² should be OK.

[/ QUOTE ]
I think I will try a bit harder to find tinned wire, the Ouzu reference reminds me how important this may be, and now is the time while the mast is down. I'll use twin core and single negative if I have to based on local stocks (I dont have time to wait for online order delivery this week).

[ QUOTE ]
If you sail at night, this is not a job to ignore.... The consequence of not being seen by shipping is not a pleasant alternative.


[/ QUOTE ]



Thanks all for responses, particularly for the article (twister_ken). I'll get tinned wire, and I'm also intended to move the connection under the deck instead of with a deck connector - the current deck connections are corroded and the (B&Q looking) 3-core cable is blackened at both ends.

 

[Inatthedeepend]

Have you looked at ASAP Supplies?
http://www.asap-supplies.com/
I have used this, product code 712323-A
CABLE 28/030 2.0mm2 30M 3CORE BLACKSHEATH
and it seems OK.

 

[cliff]

[ QUOTE ]
Another tip: securing cable. you can't drive cable clips into GRP! so I use a hot glue gun. Its also easy to peal the wires off if you need to. In places where you can't conceal wires it gives a neat finish.

[/ QUOTE ]I like that one - now where did I put the glue gun?

Another tip which I have found to be very successful is, after tinning the ends of the cables, dip them in some liquid (molten) Vaseline and leave them to sit for a few minutes. The Vaseline will wick up under the insulation and form a seal between the cable and the insulation sheath. I use an old "boiling tube" so I can immerse around 3" of the cable in the molten Vaseline (Vaseline melts at quite a low temp). Leaving the cable in the liquid for a few minutes allows the heat to travel up the copper wires and trough the insulation so the Vaseline can wick a good distance up the wire.
---------------------

Artificial Intelligence is no match for Natural Stupidity

 

[deep denial]

although Vaseline doesn't conduct electricity, so the terminal end will have to be well cleaned before joining if you are not to add further resistance

 

[lw395]

The vaseline will not stop the connectors conducting, it squeezes out of the way. This is a well known way of making motorcycle electrics more reliable.
Another point worth noting, the final verdict on your masthead wiring is to check the current being drawn, is it consistant with bulb wattage? Has it changed since last year?
Does it vary when you wiggle the connections!?
Much easier than making judgements on 10W bulbs in sunlight.
It also occurs to me that bulbs run with a little resistance in series last longer!
We should be campaigning for legal, affordable, effective LED nav lights!
As for cable, mains flex with tinned ends, the outer sheath protects it from halyards etc, and it will seal in a deck gland unlike 3 individual wires. If you want to be perfectionist, Raywire do some nice silver plated stuff, much better than tinning!
Also, check your VHF cable at the same time, these really do suffer from water, even minor corrosion of the braid can increase loss horribly. Again you can get silver plated braid.
Cheers,
Chris
ps make sure the tricolour illuminates the windex!