A question for timber boat owners re: grounding plates

Ours has a large s/s plate attached to the bottom and on that, a s/s bolt and an anode, on the inside a cable connected from that to earth on the main switch panel
Been like that for decades

4 years ago "Experts" said no and we needed a Guest sintered bronze grounding plate, I thought it odd given what had been there for decades but hey, I am not an "expert" so got bent over for several hundred dollars.
Also had to connect rudder, engine and and and to it

2 years ago we got rid of 70% of our anodes, I felt things were better, another expert who came out, spent several hours aboard with various meter's and no charge or on sell agreed and......told us to get rid of the various earthing cables from rudder, engine and and and which we did

Now, the expensive sintered bronze plate is gone, 1/4 inch bronze bolts appear sheered.
Old s/s plate with welded bolt remains nearby

Was thinking of putting a big anode on and hooking the earth cable to that again
Guy working on ours with 70ft of timber a lot older than ours has nothing.


Thoughts on this?

I don't own a wood boat, and not sure how it would differ from fiberglass.

Do you have an anode on your propeller shaft? IMO, it's there to be a sacrificial element to preserve your propeller shaft. It is my understanding that a Dynaplate is more about connecting a bonding system to transfer electricity to the water. From Guest, a manufacturer of Dynaplates:

Creates dynamic hull bonding and grounding for increased performance of electronics and lightning protection. Features most proven and reliable grounding plate, sintered porous bronze matrix with approximately 50% porosity, 48 to 1 grounding area for size, best ground path, 34% more grounding than other available plates, streamlined low resistance shape and easy 2-step thru-hull installation.

For me, I want a sacrificial element that will waste before those items that come in contact with the water. Now if your bonding system is for electronics and lightning protection, then maybe you need a Dynaplate.

My charter boat with electronics from 25 years ago, had a bonding system specifically for the electronics. My trawler doesn't. Now if I had a 70' tall aluminum mast to attract the rath of the gods, I might consider wiring it directly to a Dynaplate.

Ted

No exposed prop shaft so no anode on it.

I always thought the sintered bronze plates were to give the boat more ground area for the radios. Ham radios need a good ground plane for better performance. I didn’t think it was for bonding. I would think it would need some type of anode connected to it so it wouldn’t waste away.

Comodave said:

I always thought the sintered bronze plates were to give the boat more ground area for the radios. Ham radios need a good ground plane for better performance. I didn’t think it was for bonding. I would think it would need some type of anode connected to it so it wouldn’t waste away.

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That was my thought as well but what would I know?

Saying that I think I know slightly more than the "experts" who steered me that way.

Simi 60 said:

No exposed prop shaft so no anode on it.

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Do you have an anode on the prop nuts? Might want to read this thread before your propeller starts to turn pinkish.

https://www.trawlerforum.com/forums/s3/not-so-pretty-pink-18708.html

Ted

O C Diver said:

Do you have an anode on the prop nuts? Might want to read this thread before your propeller starts to turn pinkish.

https://www.trawlerforum.com/forums/s3/not-so-pretty-pink-18708.html

Ted

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Hasn't had any for 40 years so we no reason why it should start now

The adjacent nozzle has a few big ones and the full length steel shoe has 4 and all are nicely chopped up after 2 years
The shoe used to have 12, but for 4 years we saw no sign of anodes being eaten.

Usually when anodes show no loss it is because either using zinc for an anode in fresh water or not good contact with the metal to be protected. Have you checked the connection? I assume you are not in fresh water.

Simi 60 said:

Hasn't had any for 40 years so we no reason why it should start now

The adjacent nozzle has a few big ones and the full length steel shoe has 4 and all are nicely chopped up after 2 years
The shoe used to have 12, but for 4 years we saw no sign of anodes being eaten.

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I had a father in law who went 40,000 miles without ever changing the oil in his car. Back in the '80s you could buy a lot of oil and filters for the cost of his new engine.

So, if you spent $50 to put an anode on your propeller nuts and it wasted over time, what would be your explanation? Btw, how many anodes could you buy for the cost of a new propeller?

How many hours per year do you put on the engine? If it's a fairly small number, electrolysis may be quite minimal. As a point of comparison, I have less than 2 inches of exposed shaft and still manage to waste more than half of a collar anode every year. This year was around 800 engine hours.

Ted

Comodave said:

Usually when anodes show no loss it is because either using zinc for an anode in fresh water or not good contact with the metal to be protected. Have you checked the connection? I assume you are not in fresh water.

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Or option 3 over anoded (to many)

On our 60’ 100 year old woody we had one on the rudder and two on the shaft. No bonding of the bronze thru hulls or shaft. Had an old shipwright tell me to never add more due to the nature of our wood hull. In a hundred years someone will need to re-evaluate.

O C Diver said:

I had a father in law who went 40,000 miles without ever changing the oil in his car. Back in the '80s you could buy a lot of oil and filters for the cost of his new engine.

So, if you spent $50 to put an anode on your propeller nuts and it wasted over time, what would be your explanation? Btw, how many anodes could you buy for the cost of a new propeller?

How many hours per year do you put on the engine? If it's a fairly small number, electrolysis may be quite minimal. As a point of comparison, I have less than 2 inches of exposed shaft and still manage to waste more than half of a collar anode every year. This year was around 800 engine hours.

Ted

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I have never seen a commercial prawn trawler with running gear like ours with a prop nut anode and they do plenty of hours.

I have 2 in front of us now, same same

Simi 60 said:

I have never seen a commercial prawn trawler with running gear like ours with a prop nut anode and they do plenty of hours.

I have 2 in front of us now, same same

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Do they run a propeller shaft brush (inside the boat) to an external anode? That accomplishes the same thing.

Ted

Leave off the sintered ground plate, obviously worthless.
keep the SS plate, but you know SS is a poor conductor of electricity, and maybe was there for lightning protection, a way for a lightening strike to dissipate into the water in a more controlled manner than blasting a hole in the bottom somewhere.

On my wood boat, i unbonded all the underwater valves, but the strut and the rudder are still bonded and the prope shaft has a shaft zinc.

Unbonding valves removes them from interdependent corrosion and stray current
corrosion problems

Comodave said:

I always thought the sintered bronze plates were to give the boat more ground area for the radios. Ham radios need a good ground plane for better performance. I didn’t think it was for bonding. I would think it would need some type of anode connected to it so it wouldn’t waste away.

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I agree with Comodave, sintered bronze plates are for HF radio ground. Ham or SSB. They shouldn't be connected to the bonding system. I have no idea what your original stainless steel plate was for.

Portage_Bay said:

I agree with Comodave, sintered bronze plates are for HF radio ground. Ham or SSB. They shouldn't be connected to the bonding system. I have no idea what your original stainless steel plate was for.

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It hard a big anode on it with a grounding wire attached on the inside

Simi 60 said:

It hard a big anode on it with a grounding wire attached on the inside

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I guess they thought it would be part of the bonding system. If the only connections were a ground wire, maybe for lightning strike??? How big a wire was connected to it. For lightning protection it should have been almost battery cable size otherwise it the wire would just be a fuseable link and vaporize with a lightning strike and render the S/S plate useless.

O C Diver said:

Do they run a propeller shaft brush (inside the boat) to an external anode? That accomplishes the same thing.

Ted

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Ours doesn't and hasn't done for her life
Not sure on the others

And when I asked the last guy who checked the current/anodes etc about it he said no and to get rid of the grounding wire on the rudder as well.
This guy specialises in timber degradation and is a qualified Electrical and Marine Engineer with a Digital Electronics and Electrical Science background so would like to think he knows his stuff.

Had running gear checked this lift, buy prop and shaft guys, everything fine, see you in 10 years was the response.

Simi 60 said:

Ours doesn't and hasn't done for her life
Not sure on the others

And when I asked the last guy who checked the current/anodes etc about it he said no and to get rid of the grounding wire on the rudder as well.
This guy specialises in timber degradation and is a qualified Electrical and Marine Engineer with a Digital Electronics and Electrical Science background so would like to think he knows his stuff.

Had running gear checked this lift, buy prop and shaft guys, everything fine, see you in 10 years was the response.

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Next time you talk to them, ask them to explain why there's a difference between wood and fiberglass boats regarding anodes. Seriously, I'm always interested in learning something new and want to understand why they treat them differently. I want to understand the science, not "That's the way we've always done it".

Ted

^^^^^^^google has lots of info if you want to jump down that rabbit hole
https://www.google.com/search?q=mar...pgBAKABAcgBA8ABAQ&sclient=mobile-gws-wiz-serp

As explained to me it has to do with the properties of wood. The lignin in the wood fibers acts as a type of capacitance when interacting with saltwater. Excessive zincs cause a current flow through the wood and leeches the lignin out of the fibers and causes eventual failure. Fiberglass doesn’t have that issue.

Bob Cofer said:

As explained to me it has to do with the properties of wood. The lignin in the wood fibers acts as a type of capacitance when interacting with saltwater. Excessive zincs cause a current flow through the wood and leeches the lignin out of the fibers and causes eventual failure. Fiberglass doesn’t have that issue.

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I have read something similar to that too. But really am not sure since we have not owned a wooden boat since the 70s and then it was in fresh water.

I have sold Tidahapah now but in the 26 years I had her the only earthing was between the outer stern tube bearing and an anode attached to the hull. About 14 years ago I had an electrical guy come on board and test for current and his recommendation was to get rid of half my existing anodes, I did this and the boat was good, the anodes worked well and I would get 2 years out of them. One was on the rudder (steel) the others were attached to the steel shoe on the keel.
All skin fittings were in good condition and never any electrolysis problems.

Tidahapah said:

I have sold Tidahapah now but in the 26 years I had her the only earthing was between the outer stern tube bearing and an anode attached to the hull. About 14 years ago I had an electrical guy come on board and test for current and his recommendation was to get rid of half my existing anodes, I did this and the boat was good, the anodes worked well and I would get 2 years out of them. One was on the rudder (steel) the others were attached to the steel shoe on the keel.
All skin fittings were in good condition and never any electrolysis problems.

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Yep, think I'll keep winding back the anodes
1 on the old "Grounding Plate"
2 on the nozzle vs 6
And 3 on the shoe vs 12.

Less is more (-;

Re the grounding plate. I always had that as it was connected to my HF radio that I still had in service. But that was the only thing that was ever connected to it.

If it's not broken then don't fix it you may make it worse.

Tidahapah said:

Re the grounding plate. I always had that as it was connected to my HF radio that I still had in service. But that was the only thing that was ever connected to it.

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Was that a sintered bronze or just an anode grounding plate?

Wondering if the anode grounding plate on ours was a leftover from when she had HF as a work boat.

Simi 60 said:

Was that a sintered bronze or just an anode grounding plate?

Wondering if the anode grounding plate on ours was a leftover from when she had HF as a work boat.

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Usually for the HF radios it was sintered bronze because they look huge, electrically, compared to any regular metal. There is some dispute about how well they work and the claims as to how big they look electrically. Who knows.

Before SSB radios, we had AM sets. Not a radio tech but was told AM radios needed a ground to push against when transmitting. Back then most boats were wood and had a large copper plate on the bottom, usually about 3'x5'. It was also used as a lightening ground.

Like many fishing tuna, kept my AM radio because with a booster it had extreme range. At the right time of day, I could talk to people in the South Pacific, Gulf of Mexico and even Chile.

Simi 60 said:

Was that a sintered bronze or just an anode grounding plate?

Wondering if the anode grounding plate on ours was a leftover from when she had HF as a work boat.

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It was a wave style sintered bronze earth/grounding plate. They were wave form to increase the surface area.