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Good information Tony.

 

Another thought I had, more specifically for Residential boaters who may use a land-based satellite dish. Ensure that the screen on the coax cable to the dish is not bared and touching any land-based metal on the way to the dish as this may effectively nullify any galvanic isolation device or isolation transformer by supplying land based earth via the coax and TV to the earth of the boat (the coax jack on the TV grounds the screen to the chassis which also grounds the earth from the 3-pin plug). Maybe worth periodically putting a meter across boat and land-based earth to see that they are still well isolated from one another. What about wet ropes across an iron bollard (a can of worms I suspect)

Stephen

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8 minutes ago, Stephen Jeavons said:

Good information Tony.

 

Another thought I had, more specifically for Residential boaters who may use a land-based satellite dish. Ensure that the screen on the coax cable to the dish is not bared and touching any land-based metal on the way to the dish as this may effectively nullify any galvanic isolation device or isolation transformer by supplying land based earth via the coax and TV to the earth of the boat (the coax jack on the TV grounds the screen to the chassis which also grounds the earth from the 3-pin plug). Maybe worth periodically putting a meter across boat and land-based earth to see that they are still well isolated from one another. What about wet ropes across an iron bollard (a can of worms I suspect)

Stephen

I would expect the landline cable earth to short out any wet ropes. Water is a pretty poor conductor compared to copper.

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56 minutes ago, Flyboy said:

I would expect the landline cable earth to short out any wet ropes. Water is a pretty poor conductor compared to copper.

True, but my mains earth lead is not connected to the hull of the boat (the isolation transformer terminates it) whereas the wet ropes are.

When National Rivers Authority did flood prevention improvements at our moorings they built large iron frameworks embedded deep into the ground then covered them in timber cladding. The iron bollards to which we are tied are bolted to the ironwork through the wood so these items I would say are well earthed. Anyway, I'm sure any stray currents across wet ropes to the hull of the boat will be minuscule. The aerial cable is a more serious item I feel especially with an terrestrial TV/FM aerial where the screen might be grounded to the mast which is earthed. (Usually the screen on an aerial array isn't earthed but you never know)

Edited by Stephen Jeavons
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  • 3 months later...
On 25/10/2018 at 11:32, Flyboy said:

I would expect the landline cable earth to short out any wet ropes. Water is a pretty poor conductor compared to copper.

 

Your landline cable earth isn't isolated?

On 25/10/2018 at 12:04, Stephen Jeavons said:

True, but my mains earth lead is not connected to the hull of the boat (the isolation transformer terminates it) whereas the wet ropes are.

When National Rivers Authority did flood prevention improvements at our moorings they built large iron frameworks embedded deep into the ground then covered them in timber cladding. The iron bollards to which we are tied are bolted to the ironwork through the wood so these items I would say are well earthed. Anyway, I'm sure any stray currents across wet ropes to the hull of the boat will be minuscule. The aerial cable is a more serious item I feel especially with an terrestrial TV/FM aerial where the screen might be grounded to the mast which is earthed. (Usually the screen on an aerial array isn't earthed but you never know)

 

I read another thread somewhere where someone mentioned that wet ropes wouldn't conduct. If they did then what's the difference between that and wet boat/water/wet bank? Just because a rope is long and thin (like a cable) are we in danger of imagining it acts a conductor any more than a liquid without a defined shape?

Edited by blackrose
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