Grounding plate

[PabloPicasso]

I have been advised to fit a route to earth for shore power.

On this forum it was suggested to fit a button anode for this purpose.

I asked MgDuff (Anode supplier) and they said " "The only thing you will achieve by bonding an anode solely for the purpose of earthing, is to create a cheap grounding plate, that will need to be replaced every year. Perhaps have a search online for “Grounding Plate” or “Dynaplate”, I believe this to be the item you are after.
So what is so special about these, rather expensive, pieces of metal?

Are they just a peice of 316 stainless with fixing studs?

Or is there another factor to considerr that I'm unaware of?

 

[wonkywinch]

I thought grounding plates were made of bronze and not meant to be sacrificial. An anode is made of zinc/ally etc that gives up it's wobblycules more easily to save anything else (more expensive and made of other metals) giving up theirs.

Eg, from another forum - New SD50 Sail Drive Leg

 

[PabloPicasso]

made of bronze? That might explain the high cost.

Is that likely to have an affect any other metal parts aboard?

 

[Martin_J]

Ah.. Your other recent thread about this seemed to purely be asking about a stud for an anode, hence the replies all related to a simple stud.

A ground plate would be 'sintered' meaning it's likely made up of thousands of bronze microballs, thus giving a much larger surface area (10x a standard anode) and will be corrosion resistant..

Think of the example below..

 

[PabloPicasso]

I see.

So I'm only grounding a shore power earth.

Do I need the sintered bronze plate?

If I'm going to drill a hole in the hull for the stud, I'd like to know I'm fitting it all properly.

 

[Alex_Blackwood]

I have been advised to fit a route to earth for shore power.

On this forum it was suggested to fit a button anode for this purpose.

I asked MgDuff (Anode supplier) and they said " "The only thing you will achieve by bonding an anode solely for the purpose of earthing, is to create a cheap grounding plate, that will need to be replaced every year. Perhaps have a search online for “Grounding Plate” or “Dynaplate”, I believe this to be the item you are after.
So what is so special about these, rather expensive, pieces of metal?

Are they just a peice of 316 stainless with fixing studs?

Or is there another factor to considerr that I'm unaware of?

If the anode isn't near, or, connected to anything else it wouldn't erode

 

[wonkywinch]

I see.

So I'm only grounding a shore power earth.

Do I need the sintered bronze plate?

If I'm going to drill a hole in the hull for the stud, I'd like to know I'm fitting it all properly.

To make a good ground, you need a lot of surface area. In a domestic set up, that would be a long rod pushed into the ground, on a boat, it's the large surface area (increased as Martin explained, by sintering/texturing). These are held on with two bolts and on the other side (inside your boat) you connect the earth lead, usually via a crimped ring lug to either of the bolts.

 

[vyv_cox]

Stainless steel is a fairly poor conductor of electricity, whereas copper alloys are good. I'm not sure it would make a huge difference for an earth connection but if drilling a hole in the boat you might as well fit the right metal.

 

[PabloPicasso]

Stainless steel is a fairly poor conductor of electricity, whereas copper alloys are good. I'm not sure it would make a huge difference for an earth connection but if drilling a hole in the boat you might as well fit the right metal.

Absolutly.
Do it once, but do it right

I'm learning

Some more info and warnings here;

https://www.boats.com/how-to/dynaplate-dos-and-donts/

 

[Tranona]

If the anode isn't near, or, connected to anything else it wouldn't erode

Exactly right. Many builders use small anodes for grounding plates. The one on my Bavaria was still fine after 6 years. The one I fitted to my current boat is fine after nearly 3 years. Just make sure it is only connected to the earth wire from the shorepower. You could use an existing anode but many modern boats particularly with saildrives do not have hull anodes. If you do use an existing hull anode it will of course need replacing if it is protecting something else but that does not impact on its role of providing a ground.