Galvanic protection and Isolation

Greets: Trying to get my head around the following; galvanic isolation, metals bonding, and ships ground vs AC grounds. In reading this article which includes considerations for an ssb radio, see: http://www.sailmail.com/grounds.htm the author writes as follows: "Bonding and Electrolytic Corrosion Due to Hot Marinas 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. " Yet in my production CAL-29 all through hulls, pull pit, push pit and are bonded by means of a thick and bare copper wire that is glassed into the hull. This completely contradicts the authors conclusions. So Im getting a bit confused here....to say the least as Im working up the learning curve on this issue. Reason being I plan to install an SSB radio probably a good used Icom IC-706MKIIG at some point, say next year and as I blew out my galvanic isolator due to moisture penetration (yup the old one was full of water as no plastic O wrings on the threads) which is being addressed this year..:) So my initial question is this, "are the various metal components that are currently bonded on board, not to be bonded" Dont get it yet. Sorry. -- /ch

Just my opinion, but an article that contradicts itself in two adjacent paragraphs should probably not be considered a good source of information. In the paragraph above the one you quoted, it says to run a ground tape between the tuner, engine and keel, effectively bonding the engine and keel in contradiction to the next paragraph you referenced. Again in my opinion, the right answer is to bond everything conductive that is in contact with the water, if possible, isolated from the AC safety ground by a competent isolator. If not isolated, only plug the boat into shore power when absolutely necessary to top off batteries. Since you are bonding dissimilar metals - lead keel, bronze through hulls, ? prop shaft, etc. the fitting of zincs is essential to control what is destroyed by the electrolysis resulting from this salt water battery. Above is for salt water applications, primarily. Fresh water is substantially less effective as an electrolyte. Al 1974 Cal-25 #1693, "Sweet Mary" 1985 Cal-33 #0085, "Short Wave" --- On Sun, 12/19/10, chris123 <ch… [at] gmail.com> wrote: From: chris123 <ch… [at] gmail.com> Subject: [Cal_Boats] Galvanic protection and Isolation To: "CAL" <Ca… [at] yahoogroups.com> Date: Sunday, December 19, 2010, 3:44 PM Greets: Trying to get my head around the following; galvanic isolation, metals bonding, and ships ground vs AC grounds. In reading this article which includes considerations for an ssb radio, see: http://www.sailmail.com/grounds.htm the author writes as follows: "Bonding and Electrolytic Corrosion Due to Hot Marinas 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. " Yet in my production CAL-29 all through hulls, pull pit, push pit and are bonded by means of a thick and bare copper wire that is glassed into the hull. This completely contradicts the authors conclusions. So Im getting a bit confused here....to say the least as Im working up the learning curve on this issue. Reason being I plan to install an SSB radio probably a good used Icom IC-706MKIIG at some point, say next year and as I blew out my galvanic isolator due to moisture penetration (yup the old one was full of water as no plastic O wrings on the threads) which is being addressed this year..:) So my initial question is this, "are the various metal components that are currently bonded on board, not to be bonded" Dont get it yet. Sorry. -- /ch

On 12/19/2010 4:29 PM, Al Waschka wrote: > > Just my opinion, but an article that contradicts itself in two > adjacent paragraphs should probably not be considered a good source of > information. In the paragraph above the one you quoted, it says to > run a ground tape between the tuner, engine and keel, effectively > bonding the engine and keel in contradiction to the next paragraph you > referenced. > Again in my opinion, the right answer is to bond everything conductive > that is in contact with the water, if possible, isolated from the AC > safety ground by a competent isolator. If not isolated, only plug the > boat into shore power when absolutely necessary to top off batteries. > Since you are bonding dissimilar metals - lead keel, bronze through > hulls, ? prop shaft, etc. the fitting of zincs is essential to control > what is destroyed by the electrolysis resulting from this salt water > battery. Above is for salt water applications, primarily. Fresh > water is substantially less effective as an electrolyte. > I think Al has it right. There are contradictory goals, or at least goals whose approaches are contradictory. Bonding is great for protection in a lightning strike, to keep side flashes from occurring. But it creates opportunities for electrolysis, either from dissimilar metals being connected or from stray currents caused in marinas. The marina distribution system or other boats may be miswired. I like the idea of minimizing shore power connection. Others may make shore power use a higher priority than lightning protection. Chris Campbell >

I have not been following this thread too much but my 2 cents is to keep shore power off the boat and not bond anything except any metal fuel tanks (static). If anyone has a wood boat, this is particularly important as bonding things and putting lots of zinc around eats the wood up due to the hydroxyl ions that are part of the zinc-bronze reaction. In fact, we quit putting two zincs on my prop because we were getting too much wood fiber loss. Let me ask this, if you had a piece of zinc sitting by itself on a teflon string in the water, do you think in some way it would be at risk? Of course not. So why does that change if you install it in your boat. The only way that bronze is going to pick up any stray current is if you do bond it. The only valid reason I have seen to bond anything is if you have shore power and there is a chance that there will be a short of the hot lead to the metal in question and that you might touch it. So bond that stuff or keep shore power off the boat. If you are running 110 all over your boat, by all means bond everything and follow the safety recommendations but don't expect your through hulls to last as long. Just my thoughts after years of experiencing the evils of bonding on wood, making measurements, reading about it, and thinking about it. Disclaimer, while I have a MS-EE, I am not a bonding expert and opinions expressed are just mine. Use your own judgement. OK, that said I have read about stray currents in marinas eating props and such. Someone tell my how your boat can be subject to damage like this if you do not connect some how to the shore ground by bonding. That is, of course, the reason they want you to buy those expensive isolators. Take a VOM and measure the resistance between shore ground and your engine. If they are electrically connected, worry. Allen On Tue, Dec 21, 2010 at 6:43 AM, Chris <cc… [at] lsnm.org> wrote: > > > On 12/19/2010 4:29 PM, Al Waschka wrote: > > > > Just my opinion, but an article that contradicts itself in two adjacent > paragraphs should probably not be considered a good source of information. > In the paragraph above the one you quoted, it says to run a ground tape > between the tuner, engine and keel, effectively bonding the engine and keel > in contradiction to the next paragraph you referenced. > > Again in my opinion, the right answer is to bond everything conductive that > is in contact with the water, if possible, isolated from the AC safety > ground by a competent isolator. If not isolated, only plug the boat into > shore power when absolutely necessary to top off batteries. Since you are > bonding dissimilar metals - lead keel, bronze through hulls, ? prop shaft, > etc. the fitting of zincs is essential to control what is destroyed by the > electrolysis resulting from this salt water battery. Above is for salt > water applications, primarily. Fresh water is substantially less effective > as an electrolyte. > > > I think Al has it right. There are contradictory goals, or at least goals > whose approaches are contradictory. Bonding is great for protection in a > lightning strike, to keep side flashes from occurring. But it creates > opportunities for electrolysis, either from dissimilar metals being > connected or from stray currents caused in marinas. The marina distribution > system or other boats may be miswired. I like the idea of minimizing shore > power connection. Others may make shore power use a higher priority than > lightning protection. > > Chris Campbell > > > > > >

I am interested in researching this subject and writing up something for the L-36.com web site. Can I ask that anyone with some source material forward me a link? I will share my result with the group. I would do this just because it is interesting. I know from 21 years of hard won experience what the right thing to do is for my boat but that may not and probably is not the right thing for all boats. Looking forward to some links. Allen

Allan: The first question is "what subject" as there are several issues here that cross boundaries and are interrelated, and that's where I get lost..Let me explain: 1. How to ground your boat so that is can dissipated lightening without blowing out the sea cocks. 2. How to bond different metals to prevent stray current corrosion. 3. How to setup a proper ground on your vessel, DC system 4. How to setup a proper ground for the AC electrical current and issues to consider. 5. How to setup a proper grounding plate for your SSB radio. Now from going through these issues, mostly from hard copy, not only do several authors conflict in their opinions, so do manufacturers of equipment. So a comprehensive review article would put you in the league or Practical Sailor....got to it. To some this may not be necessary or intuitive, example, I would never even consider a boat without a bilge pump and a secondary backup, ie: freshwater intake from engine that is valved and directed to the bilge......but many disagree.....so perhaps its one of those issues. Would be very interested in your observations from an EE point of view. Best regards /ch

I am aware of the issues you mention, which is why I think I can contribute to the discussion. The various requirements conflict in some cases and I think it is important to understand why you are doing something and not just do it so that you don't do something that isn't necessary and is harmful to the equipment on your boat. Let's just say that there is a lot of myth circulating on the subject. In terms of pumps, I have 4 plus a bucket. A small auto pump to keep the bilge dry, a large electric on a float for use when the small one is overwhelmed or fails, a Whale Gusher, and a long tube portable. Regarding the bucket, I have been told that a sinking sailor with a bucket is very efficient at removing water from a boat. Allen On Tue, Dec 21, 2010 at 7:12 PM, chris123 <ch… [at] gmail.com>wrote: > > > Allan: > > The first question is "what subject" as there are several issues here that > cross boundaries and are interrelated, and that's where I get lost..Let me > explain: > > 1. How to ground your boat so that is can dissipated lightening without > blowing out the sea cocks. > > 2. How to bond different metals to prevent stray current corrosion. > > 3. How to setup a proper ground on your vessel, DC system > > 4. How to setup a proper ground for the AC electrical current and issues to > consider. > > 5. How to setup a proper grounding plate for your SSB radio. > > Now from going through these issues, mostly from hard copy, not only do > several authors conflict in their opinions, so do manufacturers of > equipment. > > So a comprehensive review article would put you in the league or Practical > Sailor....got to it. > > To some this may not be necessary or intuitive, example, I would never even > consider a boat without a bilge pump and a secondary backup, ie: freshwater > intake from engine that is valved and directed to the bilge......but many > disagree.....so perhaps its one of those issues. Would be very interested in > your observations from an EE point of view. > > Best regards > > /ch > > >

What gets me are statements like I just read: "Whenever different metals are placed in a conductive liquid you create a battery. If you connect these pieces of metal together, current will flow. The current will be removing metal from one of the metal pieces = "electrolysis". followed by: "..copper bonding wire inside that connects all the underwater metal items together so they all share the protection from zinc anodes" The issue, in case anyone misses it, is that this metal only needs protection because it is bonded! To me it is kind of like "we destroyed the village in order to save it". Allen On Tue, Dec 21, 2010 at 7:12 PM, chris123 <ch… [at] gmail.com>wrote: > > > Allan: > > The first question is "what subject" as there are several issues here that > cross boundaries and are interrelated, and that's where I get lost..Let me > explain: > > 1. How to ground your boat so that is can dissipated lightening without > blowing out the sea cocks. > > 2. How to bond different metals to prevent stray current corrosion. > > 3. How to setup a proper ground on your vessel, DC system > > 4. How to setup a proper ground for the AC electrical current and issues to > consider. > > 5. How to setup a proper grounding plate for your SSB radio. > > Now from going through these issues, mostly from hard copy, not only do > several authors conflict in their opinions, so do manufacturers of > equipment. > > So a comprehensive review article would put you in the league or Practical > Sailor....got to it. > > To some this may not be necessary or intuitive, example, I would never even > consider a boat without a bilge pump and a secondary backup, ie: freshwater > intake from engine that is valved and directed to the bilge......but many > disagree.....so perhaps its one of those issues. Would be very interested in > your observations from an EE point of view. > > Best regards > > /ch > > >