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Hull minefield


PMcC

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I've read a lot and learning a little :) I'm finding it very worrying that I'm seeing some boats needing replateing after 10-15 years or so. I've also read that two replates is the maximum. Is this down to low quality hulls, or just neglect with blacking if so who makes the best hulls. I really don't want to spend £50.000 and find that my boat will be scrapped after 15 or twenty years.

Another problem seems to be surveyors who take no responsibility for their reports, so what does a newbee do about buying a 57' narrowboat.
 

Any advice would be very welcome 

Thanks 

Phill

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Re plating (cutting out the damaged metal) can be done as many times as necessary, overplating, which i'm guessing is what you are referring to should only be done once, mainly because of the corrosion that occurs between the original metal and the plate welded to it. 

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Hi,

It's very much something to be aware of, but it's also poor quality paint, application of it, as well as general poor maintanance, and thinner 40 years ago. 

Emily Anne was shot blasted in and out, epoxy primer, two part urethane top coats, high spec underwater vynal blacking. She is now 27 years old with almost zero corrosion. 

A lot of boats rot from the inside, and it's much harder to paint, so if building new make sure the inside is painted to a higher than normal standard before the fit out. That the paint isn't damaged, and the ballast vapour barriers and equipment etc are installed in a way to minimise water ingress and maximize its ability to dry out again. 

Don't assume anything, or that all builders take the same care. 

Also read up on shoreline isolation if you plan to be plugged in to the mains 24/7 rather than just when on dock for maintanance or on a maintained mooring in a city. 

 

Daniel

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Thanks so much, that's helped put my mind a little more at ease . What difference does the electrical system make ? 

 

10 minutes ago, BWM said:

Re plating (cutting out the damaged metal) can be done as many times as necessary, overplating, which i'm guessing is what you are referring to should only be done once, mainly because of the corrosion that occurs between the original metal and the plate welded to it. 

Many thanks

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36 minutes ago, PMcC said:

Thanks so much, that's helped put my mind a little more at ease . What difference does the electrical system make ? 

 

Many thanks

Other than disconnecting it during welding, nothing. If poorly earthed it would certainly lead to more corrosion prior to the work being carried out, and this would need rectifying before going back in the water. 

If a survey picked up a corroded hull and badly installed electrical system i personally would walk away. 

Edited by BWM
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2 hours ago, PMcC said:

 What difference does the electrical system make ?

If it a shoreline has been used without any form of protection in the "earth" cable then it might make a great deal of difference. When you are looking at boats with a shoreline socket also look for a galvanic isolator or isolation transformer and try to ensure they have been used whenever the boat has had the shoreline connected. If they have neither or you are unsure if the things have been used it does not mean the hull will be eaten away but it might be so take care.

A badly installed 12/24 volt system cab cause corrosion but I would say its rare. perhaps more common on old boats that have had lost of attention from their owners to keep them going or modifying them.

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1 hour ago, brassedoff said:

I think I need to earth my boat, I was unsure if I needed too until I read this.

Thanks.

Lets assume that this is not another wind up.

For 230V AC from any source. Unless you bond (earth) the neutral conductor to the hull in some way any RCDs will not work so under fault conditions you could end up with a live hull that can then kill as people step on or off the boat or touch it. That applies to generators or inverters. A shoreline achieves this connection in one way or another by the "earth" cable as from the supply bollard but in this case it also connects your boat's hull to all the others close by who are also using shorelines and that can cause excess corrosion. The earth line needs connecting to the hull so the RCD works but isolating from the other boats in some way, this is where the galvanic isolator or an isolation transformer comes in. If you thought you did not need one then I suggest you talk to a well regarded marine electrician because once you add inverters into the mix things are nor so straight forward. Others are welcome to comment.

The 12/24 volt side of things is a little different because with no SINGLE point negative to hull bond the fuse/MCB will not blow/trip if a live wire shorted to the hull but that short might cause corrosion. However at 12/24 volts it will not kill you.

There is no need to physically connect your hull to an earthing ground spike for any reason apart from when the electricity company demands it a s[art of the normal green & yellow mains earth circuit. If you do without a very good reason then under certain conditions you could well form a cell between your hull, the water, the bank so the earth bond completes  the circuit to eat away at your hull.

 

 

Edited by Tony Brooks
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1 hour ago, Tony Brooks said:

Lets assume that this is not another wind up.

For 230V AC from any source. Unless you bond (earth) the neutral conductor to the hull in some way any RCDs will not work so under fault conditions you could end up with a live hull that can then kill as people step on or off the boat or touch it. That applies to generators or inverters. A shoreline achieves this connection in one way or another by the "earth" cable as from the supply bollard but in this case it also connects your boat's hull to all the others close by who are also using shorelines and that can cause excess corrosion. The earth line needs connecting to the hull so the RCD works but isolating from the other boats in some way, this is where the galvanic isolator or an isolation transformer comes in. If you thought you did not need one then I suggest you talk to a well regarded marine electrician because once you add inverters into the mix things are nor so straight forward. Others are welcome to comment.

The 12/24 volt side of things is a little different because with no SINGLE point negative to hull bond the fuse/MCB will not blow/trip if a live wire shorted to the hull but that short might cause corrosion. However at 12/24 volts it will not kill you.

There is no need to physically connect your hull to an earthing ground spike for any reason apart from when the electricity company demands it a s[art of the normal green & yellow mains earth circuit. If you do without a very good reason then under certain conditions you could well form a cell between your hull, the water, the bank so the earth bond completes  the circuit to eat away at your hull.

 

 

Do you do an English version, it's sounds complicated.

So if some other boat next to me had dodgy electrics then that could ROT my boat?

I have a galvanic isolator and the banking is concrete not wobbly steel.

So I am a bit simple when it comes to taking things in, if you were me would you put a wire from your hull to a spike stuck in the grass ?

Thanks for your help Tony.

 

2 hours ago, rusty69 said:

And a lightnin conductor whilst your at it

lt.jpeg

Might stop the burgers robbing my solar panels, I'll look into them.

 

Lol

  • Haha 1
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But yes, mainly, make sure it's got good paint on it. Lots of people still buy cheap or poorly speced paint. Don't paint the inside, don't remove the mill scale, and come into dry dock every other year with an orange rusty box rather than still having a shiny black boat four year on. 

 

Daniel

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11 hours ago, brassedoff said:

Do you do an English version, it's sounds complicated.

So if some other boat next to me had dodgy electrics then that could ROT my boat?

I have a galvanic isolator and the banking is concrete not wobbly steel.

So I am a bit simple when it comes to taking things in, if you were me would you put a wire from your hull to a spike stuck in the grass ?

Thanks for your help Tony.

 

Once you mix a shoreline, an inverter, and/or a generator it is a bit complicated because all inverters do not work in the same way and doing things one way may be fine for some but destroy others. That is why I suggested that you may need professional help.

It matters not a jot what the bank is made from if you connect a wire from your hull to a spike in the grass then you are providing half a circuit with the water forming the other half. Depending on a number of things this might cause hull corrosion so asw Brain says do not do it. However in certain situations the electricity company may demand such a spike is used but that is all to do with providing  an effective earth wire in the shore line cable. You do not need to concern yourself about this as long as any shoreline bollard is professionally installed.

An galvanic isolator should protect your boat but take note that they can fail in one of two ways, open circuit or short circuit. Both have potentially undesirable or even dangerous consequences so you need one with some form of indication on it or learn how to test it and do so on a regular basis.

As  long as your hull has no connection to the bank , be it a earthing spike as you describe or an unprotected shoreline earth then a boat close by with an unprotected shoreline earth or an electrical fault could rot your boat as the fault current flows via the water, your boat and the unprotected shoreline earth. If your boat is not in electrical contact with the bank/ground then damage is far less likely.

 

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