Bonding/electrolysis ?

May 6, 2010
472
1984 Oday 39 79 Milwaukee
I have two questions as I am trying to understand bonding - first, with the boat out of the water, what is the best way to troubleshoot a possible bonding or grounding issue? Second, what do I really need to have bonded? Our friend's Jeanneau has no bonding at all.

This is driven by the fact I believe I have an issue with some stray current on our 1983 O'Day 34. The last couple of seasons I have noticed an area at the keel to stub where there is discoloration on my VC-17 copper bottom paint on both sides of the keel at the same location fore and aft. I also realized that I have the same issue to a lesser degree at each of the metal thru-hulls and at the metal strainer for the engine water intake. The common denominator is that these items are all connected with a #10 bare copper bonding wire. The affected area along the keel is at the bolt the bonding wire is attached to. Also on the bonding circuit are the mast, engine, forestay and backstay straps. I use a magnesium anode on the stainless prop shaft as we are in fresh water, and it is usually about 1/3 gone in a season. The bronze prop and strut may be seeing some galvanic corrosion, almost like they were sanded with course sandpaper, not really pitted so maybe it is electrolysis? We are on a mooring so stray dock current or another boat don't seem likely to be part of the issue.
 

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Jun 11, 2011
1,243
Hunter 41 Lewes
Are you in a location that allows the keel to touch bottom during certain tides?
 
Jan 11, 2014
11,321
Sabre 362 113 Fair Haven, NY
You are not alone. I had a similar issue with my Sabre 30 on Lake Ontario. Unfortunately I was unable to trace the source of the problem. I had 2 theories, 1) the Magnesium anodes were reacting with the copper in the VC17 or 2) because some of the AC wiring was bundled with some of the DC wiring I was getting an induced current while plugged into shore power.

The wasting of the Mg anode is consistent with my experience, i.e., about a ⅓ of it was lost each season. Remember, these are sacrificial anodes. Sacrificial is operative word.
 
May 6, 2010
472
1984 Oday 39 79 Milwaukee
You are not alone. I had a similar issue with my Sabre 30 on Lake Ontario. Unfortunately I was unable to trace the source of the problem. I had 2 theories, 1) the Magnesium anodes were reacting with the copper in the VC17 or 2) because some of the AC wiring was bundled with some of the DC wiring I was getting an induced current while plugged into shore power....
In our case, it almost certainly is not an AC issue as we only connect to shore power 2 - 3 times a season, usually just for one night in each instance. We do have a small inverter onboard, but it only connects to the positive and negative battery terminals, and we only power a laptop with it for a couple hours a few times a season. I am curious about the copper in the bottom paint though, and most importantly, how to go about troubleshooting this problem.
 
May 6, 2010
472
1984 Oday 39 79 Milwaukee
So the question is whether to bond or not to bond? Anyone care to weigh in on the pros and cons?? What would be a good, contemporary resource on the issue?
 
Oct 19, 2017
7,732
O'Day 19 Littleton, NH
or 2) because some of the AC wiring was bundled with some of the DC wiring I was getting an induced current while plugged into shore power.
It is probably not the bundling of wires. Inductors are made by coiling wire. The induction current creates a magnetic field that is perpendicular to the electron movement through the coils. This is the force that induces a current in another coiled wire placed parallel with the primary coil. Straight wires laid side by side would produce a circular magnetic force that could induct a current but with very little force. It would be hard to detect.
I wonder if there is another metal source, maybe aluminium, near by, a neighboring boat, something on the bottom, conduit pipes under a dock, that could cause an electrolytic reaction. Maybe try attaching or just hanging next to the hull, a zinc bar. If that gets eaten up quickly you probably have an electrolysis problem. It would be good to find the other disparate metal object. Fresh water is not as bad as salt water but if you have minerals or very low ph in your water you could see similar results.
If there's nothing but a disintegrating zinc block, then keep one of those fixed to your garboards or keel as a sacrificial metal that has to be changed out once in a while.
I really couldn't say if bonding was a good idea or not. Cooper on steel isn't best. It sounds like it would be good for grounding out a strong electrical current. There is, however, an anti oxidation paste that may help that you can smear on the connections to help prevent corrosion due to electrolysis.
https://www.amazon.com/dp/B000BODU6...t=&hvlocphy=9009782&hvtargid=pla-312642340937
Put that on all your connections
- Will (Dragonfly)
 
May 6, 2010
472
1984 Oday 39 79 Milwaukee
Continuing research on this issue has led me to this article which so far is the best explanation of the potential problems as well as the most detailed description of solutions. It is a few years old, but seems to still make sense, and barring any future input indicating I should do otherwise, I will begin to implement these methods on my boat.

https://sailmail.com/wp-content/uploads/2016/02/Grounding.pdf
 
Feb 6, 1998
11,665
Canadian Sailcraft 36T Casco Bay, ME
Continuing research on this issue has led me to this article which so far is the best explanation of the potential problems as well as the most detailed description of solutions. It is a few years old, but seems to still make sense, and barring any future input indicating I should do otherwise, I will begin to implement these methods on my boat.

https://sailmail.com/wp-content/uploads/2016/02/Grounding.pdf

Even today, Stan's article is one of the best, if folks actually under stand it and don't take it out of context. Stan is no slouch and as one of the most, if not the most, in demand ocean racing navigator out there. As a navigator he has likely won more high profile sailboat races than anyone I can think of. Just last year he and the crew of Comanche (a Maine built boat) smashed the trans Atlantic record by an entire 24 hours, a record that had been held for 13 years previously... Stan is also the guy responsible for putting lines on the football field, on the water in Americas cup races and on the field of other sports too.

I had the privilege of helping Stan design the LiFePO4 battery system for his personal boat. Comanche, the boat he is currently navigator on, (Jim & Kristy Clark's 100' ocean maxi) also has a LiFePO4 bank..

Just last week I was speaking with one of the lead instructors for the ABYC, who is also a marine electrician and corrosion expert, I asked Charlie a question (already knew what mine was).

"What is your number one source of rapid corrosion on boats (DC) and where does it originate from?"

A #1 = "Bilge pump systems. Too many boat owners & builders use centrifugal bilge pumps as a primary pump not a secondary high mounted catastrophic pump."

A #2 = "98% of the time the issue is originating from owners own boat, despite their kicking and denial, until I show them."
 
Sep 23, 2009
1,475
O'Day 34-At Last Rock Hall, Md
First I have heard of A #1. What should be the primary pump? I don't think I have ever seen a boat that did not have a centrifugal as the primary low in the bildge.
 
Feb 6, 1998
11,665
Canadian Sailcraft 36T Casco Bay, ME
First I have heard of A #1. What should be the primary pump? I don't think I have ever seen a boat that did not have a centrifugal as the primary low in the bildge.
Nuisance water should ideally be done with a diaphragm type pump mounted out of the bilge (only the hose dips into the bilge) with the centrifugal pump/s mounted higher than the nuisance water pump so the only time it is submerged is in an emergency. If it remains out of the bilge water 99.9% of the time, it minimizes the chance of a DC current leak into the bilge water...

Improper wiring, improper terminations and pump seal failures run pretty rampant with centrifugal pumps.
 
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May 6, 2010
472
1984 Oday 39 79 Milwaukee
A #1 would most likely not apply to our boat as we keep the bilge dry.
A #2 is highly likely although the source remains a mystery - hence this thread ;-)
 
May 6, 2010
472
1984 Oday 39 79 Milwaukee
In the linked article, the author suggests decoupling the VHF antenna from the DC ground system by means of an inner/outer DC block. This is not a dime store piece of equipment and I am wondering why mounting the VHF whip on a non-conductive bracket wouldn't accomplish the same goal? The only issue I can see is that with the author's method the mast (and stays) are connected to the keel for lightning "protection", and the antenna whip would then be isolated from this system. Even if this means the DC grounding system is then vulnerable via the antenna whip, it seems that in practical experience this protection system is at best unreliable since most of the instruments in a strike are wiped out anyway?
 
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Oct 19, 2017
7,732
O'Day 19 Littleton, NH
in practical experience this protection system is at best unreliable since most of the instruments in a strike are wiped out anyway?
If you consider that the charge in a lightning strike has enough energy to arc from cloud to ground through the insulation of a mile or more of air, a few mm of insulation isn't going to stop it either. The only protection would be either providing the electrons with a far better path to ground or something like a Faraday cage, which is why the inside of a metal car is good protection, not because of its rubber tires.
- Will (Dragonfly)
 
Sep 23, 2009
1,475
O'Day 34-At Last Rock Hall, Md
Having read that article many times I believe that in a usually dry bilge the thru hull fittings should be isolated, the mast and stays grouned to the keel, and the electrical systems grounded to the engine. This is how my boat is being set up now. But only my2 cents as I am in no way a boat grounding expert.
 
May 6, 2010
472
1984 Oday 39 79 Milwaukee
If you consider that the charge in a lightning strike has enough energy to arc from cloud to ground through the insulation of a mile or more of air, a few mm of insulation isn't going to stop it either. The only protection would be either providing the electrons with a far better path to ground or something like a Faraday cage, which is why the inside of a metal car is good protection, not because of its rubber tires.
- Will (Dragonfly)
I may not have made my question clear - I'm wondering specifically about the viability of mounting the VHF antenna on a non-conductive bracket as a means of decoupling it from the lightning bonding system of the mast. Question is related to the recommendations in the linked article earlier in the thread.
 

jviss

.
Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
Even today, Stan's article is one of the best, if folks actually under stand it and don't take it out of context.
@Maine Sail , I just read the article ( a couple of times), and checked the ground and bonding scheme drawing for my Tartan, and they are at odds. I've included the page from the Tartan manual. The article says:
Do not bond any thru-hulls or other immersed metal that can be electrically isolated. Specifically, keep your metal keel/ballast, your metal rudder shaft, your engine/prop, and all thru-hulls electrically isolated, from each other, and from the engine.
Please see the manual page I've included. The bottom right is the mast, chainplate, keel bolt node; the top left is the "ground bar," collecting engine, battery, DC panel, and AC panel grounds.

Question: should I isolate the mast grounding node from the ground bar? Meaning, should I bring this into compliance with the article by disconnecting the "No. 8 BARE" wires from the bottom of the ground bar (and joing the backstay and other mast wires)?

Thanks,

jv
 

jviss

.
Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
I may not have made my question clear - I'm wondering specifically about the viability of mounting the VHF antenna on a non-conductive bracket as a means of decoupling it from the lightning bonding system of the mast. Question is related to the recommendations in the linked article earlier in the thread.
That makes a lot of sense to me, having read the article. I have never seen it done, though. Is the antenna mounting bracket really electrically connected to the shield of the cable? It shouldn't be, according to best practice for coax cables and shielding.
 
May 6, 2010
472
1984 Oday 39 79 Milwaukee
That makes a lot of sense to me, having read the article. I have never seen it done, though. Is the antenna mounting bracket really electrically connected to the shield of the cable? It shouldn't be, according to best practice for coax cables and shielding.
In the attached image, my VHF antenna bracket can be seen at the bottom. The threaded base of the antenna extends through the hole and the coax connector screws onto it. My understanding is the shield of the coax (which touches the threaded portion of the connector) carries the ground to the radio, the radio is connected to the DC ground system, hence the mast becomes part of that system as well. The goal as mentioned in the article is to isolate the mast from the DC grounding system.
 

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