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Old 03-08-2016, 08:31   #1
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Wire size for Cathodic and/or Lightning protection

I am about to install a new zinc on our boat while at the same time re-installing our outdrive. Since I've pulled the old wires out I thought it would be worthwhile to install a better wire. The one I currently have has a couple of strands and is about 14-12AWG. In reading Nigel's book I see he suggests 8AWG for cathodic protection and 6AWG if it's part of the lightning protection system.

I'm thinking 8 AWG is rather large given the low currents, unless it's because we want to keep the resistance (voltage drop) down.

What do you have on your boat for Cathodic protection?

The lightning protection on our boat is non-existant and being a catamaran with batteries & electrical cabinet below the mast I'm not sure how to deal with that.... for another day I guess...
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Old 03-08-2016, 08:54   #2
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Re: Wire size for Cathodic and/or Lightning protection

Calder's recommendations are as per ABYC standards. (as of 2001). I don't have the more recent stds. Is your outdrive electrically isolated from the engine/transmission? The smaller wires were not likely meant for cathodic protection but ground for a tirm pump or something like that. Hard to tell without seeing the setup or knowing which engine/outdrive combo you have.
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Old 03-08-2016, 09:03   #3
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Re: Wire size for Cathodic and/or Lightning protection

Confused... is the cathodic protection for the outdrive?
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Old 03-08-2016, 09:17   #4
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Re: Wire size for Cathodic and/or Lightning protection

The outdrive has no electrics on it - it's purely a mechanical transfer of from the engine transmission to the prop.



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Originally Posted by knottybuoyz View Post
Calder's recommendations are as per ABYC standards. (as of 2001). I don't have the more recent stds. Is your outdrive electrically isolated from the engine/transmission? The smaller wires were not likely meant for cathodic protection but ground for a tirm pump or something like that. Hard to tell without seeing the setup or knowing which engine/outdrive combo you have.
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Old 03-08-2016, 09:19   #5
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Re: Wire size for Cathodic and/or Lightning protection

The Cathodic protection is mounted on the hull to protect both the outdrive and engine & rudder stocks

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Confused... is the cathodic protection for the outdrive?
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Old 04-08-2016, 09:53   #6
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Re: Wire size for Cathodic and/or Lightning protection

Quote:
Originally Posted by geoffr View Post
I am about to install a new zinc on our boat while at the same time re-installing our outdrive. Since I've pulled the old wires out I thought it would be worthwhile to install a better wire. The one I currently have has a couple of strands and is about 14-12AWG. In reading Nigel's book I see he suggests 8AWG for cathodic protection and 6AWG if it's part of the lightning protection system.

I'm thinking 8 AWG is rather large given the low currents, unless it's because we want to keep the resistance (voltage drop) down.

What do you have on your boat for Cathodic protection?

The lightning protection on our boat is non-existant and being a catamaran with batteries & electrical cabinet below the mast I'm not sure how to deal with that.... for another day I guess...
FYI in a thunderstorm in Curacao last Xmas I rapped the anchor chain around the mast and lowered it over the toe rail in the water. The boat got hit and damage control revealed blown LED bulb of anchor light, had to repair it because it also damaged the board on the control panel, and also the steaming light was blown with its circuitry. The rest of the running lights not damaged. Nothing else on the boat damaged.
Ernie on the Mary Jane
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Old 04-08-2016, 11:57   #7
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Re: Wire size for Cathodic and/or Lightning protection

My (albeit limited) understanding is that there are two kinds of lightening protection wiring. The first incorporates the wires of the bonding system which keep the voltage of the boat at the same potential as the surrounding ocean and therefore, in theory make the boat no more attractive to a bolt of lightening then the surrounding ocean. These wires are all low current. The second lightening protection wire is designed to help direct the current in the event of a strike. This cable needs to be substantial and should be in a straight line as possible from the chain plates to an under-water lightening plate. This cable on my boat is bigger than my battery cables.
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Old 04-08-2016, 13:01   #8
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Re: Wire size for Cathodic and/or Lightning protection

Stray current protection is vastly different than lightning protection. Zincs handle the strays quite well. Since you have a kitty, why not run a 4 gauge copper rod/strap configuration from the mast down through the deck into the water so there is a straight line path for lightning to take if it so wished to do so. Could make it swing up and out of the way when sailing, or flexible so it dragged through the water if you are sailing in a storm.

Someone mentioned using an anchor chain. We saw a bbb chain literally melted from a lightning strike that went evidently from the mast to the chain and down into the sea. Burned a nice big hole in the foredeck right down to the waterline.
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Old 04-08-2016, 13:15   #9
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Re: Wire size for Cathodic and/or Lightning protection

For cathodic protection, your looking at voltages in the mV range. So it can't afford too much voltage drop. Would 12 gauge work... Yes. 8 gauge would work better in that the protected level would be a bit higher and allow for some resistance in connectors over the years. When your talking protecting an out drive, wire is cheap.
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Old 05-08-2016, 00:40   #10
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Re: Wire size for Cathodic and/or Lightning protection

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Originally Posted by reed1v View Post
Stray current protection is vastly different than lightning protection. Zincs handle the strays quite well. Since you have a kitty, why not run a 4 gauge copper rod/strap configuration from the mast down through the deck into the water so there is a straight line path for lightning to take if it so wished to do so. ...
You could save a lot on weight by using pipe instead of a cable.

The instantaneous current is only on the outside of the conductor,
which means you need only the outer circumference to carry current.

Even better, however, would be a wide strip of aluminium.
You can get rolls of the this which you could easily deploy and easily stow.

An original lightning pipe discussion was here:
https://archive.is/ZBb2A

The difference being that a wire too thin will explode (detonate, violently)
and a wire too thick is just one more heavy thing to be hauling around
for that brief moment when you need it.

Hope this helps
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Old 05-08-2016, 08:52   #11
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Re: Wire size for Cathodic and/or Lightning protection

Privilege,

How is the cable for lightning from your mast to underwater routed? (as I figure out how it's done on Cats). And any guess on the sized? (2/0?)

Geoff


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Originally Posted by Privilege View Post
My (albeit limited) understanding is that there are two kinds of lightening protection wiring. The first incorporates the wires of the bonding system which keep the voltage of the boat at the same potential as the surrounding ocean and therefore, in theory make the boat no more attractive to a bolt of lightening then the surrounding ocean. These wires are all low current. The second lightening protection wire is designed to help direct the current in the event of a strike. This cable needs to be substantial and should be in a straight line as possible from the chain plates to an under-water lightening plate. This cable on my boat is bigger than my battery cables.
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Old 13-08-2016, 02:56   #12
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Re: Wire size for Cathodic and/or Lightning protection

We fit a Forespar Lightning Master on our boats. We had everything wiped out by a lightning strike many years ago in Durban. We had a piece of chain wrapped around the mast base and bulldog clipped section of chain from a side stay both dangling in the water. My wife said the whole boat lit up inside with a purple/blue light (I was ashore).
We were later given a dissapator that was being tested by Eskom (the South African electricity provider) that originated from Canada where we were told they were used on transmission towers. It doesnt really matter ..... we have since bought the Foremaster 'stainless steel toilet brushes' and have not experienced any issues since. We have sometimes had the tallest mast yet have seen nearby boats (perhaps twice in twenty years) get struck. They seem to do the job for us. Our VHF aerial is slightly taller that our brush but doesnt seem to influence the effect.


Quote:
Originally Posted by geoffr View Post
I am about to install a new zinc on our boat while at the same time re-installing our outdrive. Since I've pulled the old wires out I thought it would be worthwhile to install a better wire. The one I currently have has a couple of strands and is about 14-12AWG. In reading Nigel's book I see he suggests 8AWG for cathodic protection and 6AWG if it's part of the lightning protection system.

I'm thinking 8 AWG is rather large given the low currents, unless it's because we want to keep the resistance (voltage drop) down.

What do you have on your boat for Cathodic protection?

The lightning protection on our boat is non-existant and being a catamaran with batteries & electrical cabinet below the mast I'm not sure how to deal with that.... for another day I guess...
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Old 14-08-2016, 09:36   #13
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Re: Wire size for Cathodic and/or Lightning protection

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Originally Posted by geoffr View Post
Privilege,

How is the cable for lightning from your mast to underwater routed? (as I figure out how it's done on Cats). And any guess on the sized? (2/0?)

Geoff
I have heavy cable running from the bolts on the inside of my chain plates down to a sintered bronze plate bolted through the hull on the outside of the hull. The boat came from the manufacturer this way. My reading suggests that the sintered bronze plates aren't the best for lightening protection. I will replace it with a steel plate in due course. At the moment however, I'm happy that my mast is at the same electric potential as the surrounding ocean.
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