Bond the prop shaft to the boat's grounding system?
Moderator: Jim Walsh
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Mike Schwartz
Bond the prop shaft to the boat's grounding system?
I have a Cape Dory 36 with a three bade max prop which has its zinc mounted on the central hub of the prop. There is a hard rubber disc in the drive shaft at the coupler. At present there is no brush connecting the shaft to the boat's grounding system. The zinc just lasts the season. Should I electrically tie the distal shaft to the grounding system?
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D. Stump, Hanalei
Re: Bond the prop shaft to the boat's grounding system?
Mike,
I believe that there is usually a jumper wire across the shaft to output shaft flanges that ties the shaft to the engine through the transmission to the engine ground. So, the easy fix is to install a short jumper wire across the flanges. Instantaneous ground! Doesn't take brushes or any special equipment. Just leave a little slack in the wire so it can vibrate naturally and you should be all set.
Thanks for posting the question, I'm not sure if Hanalei has the jumper, but will check before she comes off the hard this Friday!
Dave Stump
Captain Commanding
s/v Hanalei CD-30
I believe that there is usually a jumper wire across the shaft to output shaft flanges that ties the shaft to the engine through the transmission to the engine ground. So, the easy fix is to install a short jumper wire across the flanges. Instantaneous ground! Doesn't take brushes or any special equipment. Just leave a little slack in the wire so it can vibrate naturally and you should be all set.
Thanks for posting the question, I'm not sure if Hanalei has the jumper, but will check before she comes off the hard this Friday!
Dave Stump
Captain Commanding
s/v Hanalei CD-30
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Matt Cawthorne
Re: Bond the prop shaft to the boat's grounding system?
Mike,
This is post might get you many conflicting opinions. On my '36 I do not ground the shaft to the rest of the bonding system. My reason for this is simple. All metal underwater is bronze except the prop shaft and prop. In the absence of any externally applied current the bronze will hold up just fine and will prevent barnacles from growing to boot. The shaft is stainless and must be protected by a zinc. If you bond the existing zinc to more under water metal components the zinc will disappear at an even faster rate. If you had a zinc which gets used up now, you may then find that by the end of the season your zinc disappears and your expensive prop and through hulls become the sacrificial metal! My zinc fell off one year (yes I installed it) and the prop began to experience significant dezincification. The one good thing that can come of bonding your propeller is in the event of a lightning strike your prop would be able to dissipate much more current than your through hulls.
Matt
Mcawthor@bellatlantic.net
This is post might get you many conflicting opinions. On my '36 I do not ground the shaft to the rest of the bonding system. My reason for this is simple. All metal underwater is bronze except the prop shaft and prop. In the absence of any externally applied current the bronze will hold up just fine and will prevent barnacles from growing to boot. The shaft is stainless and must be protected by a zinc. If you bond the existing zinc to more under water metal components the zinc will disappear at an even faster rate. If you had a zinc which gets used up now, you may then find that by the end of the season your zinc disappears and your expensive prop and through hulls become the sacrificial metal! My zinc fell off one year (yes I installed it) and the prop began to experience significant dezincification. The one good thing that can come of bonding your propeller is in the event of a lightning strike your prop would be able to dissipate much more current than your through hulls.
Matt
Mike Schwartz wrote: I have a Cape Dory 36 with a three bade max prop which has its zinc mounted on the central hub of the prop. There is a hard rubber disc in the drive shaft at the coupler. At present there is no brush connecting the shaft to the boat's grounding system. The zinc just lasts the season. Should I electrically tie the distal shaft to the grounding system?
Mcawthor@bellatlantic.net
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D. Stump, Hanalei
Re: Bottom paint on bronze thru hulls??
Matt,
Along with the original question, comes this one. Should the thru hulls (that are bronze) be painted with antifouling bottom paint?(only the mushroom part on the outside of the hull.) I had two people at the yard give me different answers, one said to paint the thru hulls and up inside them as far as you can reach with a small (1/2") brush, the other said to leave the thru hulls bare. So what is the proper thing to do?
Thanks for your help...
Dave Stump
Along with the original question, comes this one. Should the thru hulls (that are bronze) be painted with antifouling bottom paint?(only the mushroom part on the outside of the hull.) I had two people at the yard give me different answers, one said to paint the thru hulls and up inside them as far as you can reach with a small (1/2") brush, the other said to leave the thru hulls bare. So what is the proper thing to do?
Thanks for your help...
Dave Stump
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John
Re: Bond the prop shaft to the boat's grounding system?
Yes, you should have all your underwater metal fittings tied to your "common ground point". In your case you do need to install a jumper wire across the coupler rubber vibration dampner thus electrically connecting the two halves of the coupler completing the path to ground.
From experience I have noted that tin plated braided copper strap works best. You can purchase the braid from battery specialty dealers or purchase already made up "braid" ground cables from some automotive parts stores and modify the length to suit your needs. When I have modified them in the past I simply cut them to an appropriate length and then solder about 1" of each end with a high tin % solder such as a lead free electronics solder. You will need a propane torch to be able to solder the braid. When finished drill the appropriate sized hole to fit your coupler bolts. Install the strap with adequate length to compensate for flexing of the coupler. You should also do a complete check on the boat for possible ground leaks.
From experience I have noted that tin plated braided copper strap works best. You can purchase the braid from battery specialty dealers or purchase already made up "braid" ground cables from some automotive parts stores and modify the length to suit your needs. When I have modified them in the past I simply cut them to an appropriate length and then solder about 1" of each end with a high tin % solder such as a lead free electronics solder. You will need a propane torch to be able to solder the braid. When finished drill the appropriate sized hole to fit your coupler bolts. Install the strap with adequate length to compensate for flexing of the coupler. You should also do a complete check on the boat for possible ground leaks.
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Tom
Re: Bottom paint on bronze thru hulls??
Dave, I and everyone I know paints them including the inside. The copper in the bottom paint is very close to bronze on the galvanic scale so there is no electrolysis to speak of. If you don't paint them, you won't believe the growth that can grow there. The only thing I don't paint is the dyna plate and the prop shaft. Don't forget to paint behind the rudder with a tiny brush as well. Push it all the way to one side and paint and then push to the other side and paint the other.D. Stump, Hanalei wrote: Matt,
Along with the original question, comes this one. Should the thru hulls (that are bronze) be painted with antifouling bottom paint?(only the mushroom part on the outside of the hull.) I had two people at the yard give me different answers, one said to paint the thru hulls and up inside them as far as you can reach with a small (1/2") brush, the other said to leave the thru hulls bare. So what is the proper thing to do?
Thanks for your help...
Dave Stump
TacCambria@thegrid.net
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Greg Kozlowski
Re: Bottom paint on bronze thru hulls??
My surveyor and the boat yard both advised that the thru hulls be sanded down to original bronze, then barrier coated before applying
bottom paint throughout, including inside. Depending on what
kind of bottom paint you use, some bottom paints such as Petit, Trinidad which have high copper content may interact with the bronze - therefore the barrier coat first.
Greg Kozlowski
"Sherpa" CD36
koz@seijo.ac.jp
bottom paint throughout, including inside. Depending on what
kind of bottom paint you use, some bottom paints such as Petit, Trinidad which have high copper content may interact with the bronze - therefore the barrier coat first.
Greg Kozlowski
"Sherpa" CD36
koz@seijo.ac.jp
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matt cawthorne
Re: Bottom paint on bronze thru hulls??
Dave,
I knew this one would get lots of conflicting answers. The Patricia Louise had all of the through hulls unbonded when I bought her. I reconnected all, but did not connect the shaft/prop. I barrier coated the bottom before I launched her the first time and since I ran the epoxy barrier coat up on to the mushroom heads for a short distance I painted the outside of the mushroom heads. Mostly I am just sloppy with the roller and coat the tops out of laziness. I have never coated the inside of any of my bronze through hull fittings. I keep the boat on the Chesapeake where barnacles will grow to nearly 1/2 inch in height on an unprotected surface in one season. I have NEVER had a barnacle grow on any of my through hull fittings, either inside or out. Nor have I had a barnacle grow on the inside or outside of the engine intake strainer which covers the through hull head and which can not be painted. The prop which is galvanically protected is another story.
The story would be different if you had other metals bonded to the bronze fittings. If you have any other metals in there you need to either isolate them or bond and galvanically protect.
If you have only bronze fittings bonded together below the waterline and you have barnacles growing then you probably have some sort of problem with your electrical ground.
I also feel strongly that one should never connect the AC ground from the shore power into the bonding system. If you do your boats through hull fittings might just get to be the replacements for the sacrificial zincs for the steel boat down the dock. Also don't ever use the boats bonding system as a ground wire for some appliance in your DC system. I have read articles in the past where boats have sunk at the dock when their through hull fittings disolved because of both of these problems. There are electrical devices which handle the AC grounding issues. The best is an isolation transformer. The drawback is that they are both heavy and expensive. The other is some sort of solid state device that I read about which is lighter and cheaper, but can fail in such a way as to render it useless. I never leave the boat connected to shore power while I am away.
I am shure that this is more than you wanted to hear.
Matt
mcawthor@bellatlantic.net
I knew this one would get lots of conflicting answers. The Patricia Louise had all of the through hulls unbonded when I bought her. I reconnected all, but did not connect the shaft/prop. I barrier coated the bottom before I launched her the first time and since I ran the epoxy barrier coat up on to the mushroom heads for a short distance I painted the outside of the mushroom heads. Mostly I am just sloppy with the roller and coat the tops out of laziness. I have never coated the inside of any of my bronze through hull fittings. I keep the boat on the Chesapeake where barnacles will grow to nearly 1/2 inch in height on an unprotected surface in one season. I have NEVER had a barnacle grow on any of my through hull fittings, either inside or out. Nor have I had a barnacle grow on the inside or outside of the engine intake strainer which covers the through hull head and which can not be painted. The prop which is galvanically protected is another story.
The story would be different if you had other metals bonded to the bronze fittings. If you have any other metals in there you need to either isolate them or bond and galvanically protect.
If you have only bronze fittings bonded together below the waterline and you have barnacles growing then you probably have some sort of problem with your electrical ground.
I also feel strongly that one should never connect the AC ground from the shore power into the bonding system. If you do your boats through hull fittings might just get to be the replacements for the sacrificial zincs for the steel boat down the dock. Also don't ever use the boats bonding system as a ground wire for some appliance in your DC system. I have read articles in the past where boats have sunk at the dock when their through hull fittings disolved because of both of these problems. There are electrical devices which handle the AC grounding issues. The best is an isolation transformer. The drawback is that they are both heavy and expensive. The other is some sort of solid state device that I read about which is lighter and cheaper, but can fail in such a way as to render it useless. I never leave the boat connected to shore power while I am away.
I am shure that this is more than you wanted to hear.
Matt
D. Stump, Hanalei wrote: Matt,
Along with the original question, comes this one. Should the thru hulls (that are bronze) be painted with antifouling bottom paint?(only the mushroom part on the outside of the hull.) I had two people at the yard give me different answers, one said to paint the thru hulls and up inside them as far as you can reach with a small (1/2") brush, the other said to leave the thru hulls bare. So what is the proper thing to do?
Thanks for your help...
Dave Stump
mcawthor@bellatlantic.net
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D. Stump, Hanalei
Re: Bottom paint on bronze thru hulls??
Matt,
Thanks for your reply. I am going to paint all through hulls except the dynaplate before she goes in on Friday. They were painted before, and showed a minimum amount of growth (almost none). The grounding of the 110 vAC is something I'm not too sure of. As I recall, you can ground the green ground wire to the ships ground, but the neutral should never be tied to the ships ground. Of course, if the neutral opens, either on board or on the dock, the ground becomes "live" and then you not only have a galvanic corrosion problem but an electric shock hazard! When I wire Hanaleis' 110v system this spring, I will install GFCI's and circuit breakers in all circuits. This should protect against any stray current(like through my 1st. Mate!), but I'm am still not sure about connecting the green ground to the ships ground?
Can you or anyone else clarify??
I agree with you, I will never leave shorepower connected when I am not in attendance. The lady that owns a Pearson in the slip next to us does that all the time and will eat up a hanging "fish" zinc in a few months. I've tried to tell her, but it hasn't gotten through yet! She was pulled one fall with all underwater bronze a bright red color! And, once, it did eat her prop!
Dave Stump
Captain Commanding
s/v Hanalei CD-30
Thanks for your reply. I am going to paint all through hulls except the dynaplate before she goes in on Friday. They were painted before, and showed a minimum amount of growth (almost none). The grounding of the 110 vAC is something I'm not too sure of. As I recall, you can ground the green ground wire to the ships ground, but the neutral should never be tied to the ships ground. Of course, if the neutral opens, either on board or on the dock, the ground becomes "live" and then you not only have a galvanic corrosion problem but an electric shock hazard! When I wire Hanaleis' 110v system this spring, I will install GFCI's and circuit breakers in all circuits. This should protect against any stray current(like through my 1st. Mate!), but I'm am still not sure about connecting the green ground to the ships ground?
Can you or anyone else clarify??
I agree with you, I will never leave shorepower connected when I am not in attendance. The lady that owns a Pearson in the slip next to us does that all the time and will eat up a hanging "fish" zinc in a few months. I've tried to tell her, but it hasn't gotten through yet! She was pulled one fall with all underwater bronze a bright red color! And, once, it did eat her prop!
Dave Stump
Captain Commanding
s/v Hanalei CD-30
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Matt Cawthorne
green wire
Dave,
Before connecting the green wire to the ships ground research is in order. I believe that I read in practical sailor that it should not be connected to the ships ground. The two reasons that I can immediately think of are that if your black wire goes open then you can start dumping AC current into the water through the green wire. That can be decidedly unhealthy for any swimmers in the area. Secondly the green wire allows DC current to flow from other boats or earth ground to your through hull fittings. You do not want your through hulls connected to the Pearson owners do you? My recommendation is to get a copy of the ABYC electrical standards if you are going to mess with the AC ground. Some "marine electricians" are not even up on the latest ABYC recommendations.
I bought a silver/silver chloride half cell to check out my system when it goes in to the water. I like the idea of just using a copper plate instead and am sort of regretting having spent the money on the half cell.
Matt
mcawthor@bellatlantic.net
Before connecting the green wire to the ships ground research is in order. I believe that I read in practical sailor that it should not be connected to the ships ground. The two reasons that I can immediately think of are that if your black wire goes open then you can start dumping AC current into the water through the green wire. That can be decidedly unhealthy for any swimmers in the area. Secondly the green wire allows DC current to flow from other boats or earth ground to your through hull fittings. You do not want your through hulls connected to the Pearson owners do you? My recommendation is to get a copy of the ABYC electrical standards if you are going to mess with the AC ground. Some "marine electricians" are not even up on the latest ABYC recommendations.
I bought a silver/silver chloride half cell to check out my system when it goes in to the water. I like the idea of just using a copper plate instead and am sort of regretting having spent the money on the half cell.
Matt
D. Stump, Hanalei wrote: Matt,
Thanks for your reply. I am going to paint all through hulls except the dynaplate before she goes in on Friday. They were painted before, and showed a minimum amount of growth (almost none). The grounding of the 110 vAC is something I'm not too sure of. As I recall, you can ground the green ground wire to the ships ground, but the neutral should never be tied to the ships ground. Of course, if the neutral opens, either on board or on the dock, the ground becomes "live" and then you not only have a galvanic corrosion problem but an electric shock hazard! When I wire Hanaleis' 110v system this spring, I will install GFCI's and circuit breakers in all circuits. This should protect against any stray current(like through my 1st. Mate!), but I'm am still not sure about connecting the green ground to the ships ground?
Can you or anyone else clarify??
I agree with you, I will never leave shorepower connected when I am not in attendance. The lady that owns a Pearson in the slip next to us does that all the time and will eat up a hanging "fish" zinc in a few months. I've tried to tell her, but it hasn't gotten through yet! She was pulled one fall with all underwater bronze a bright red color! And, once, it did eat her prop!
Dave Stump
Captain Commanding
s/v Hanalei CD-30
mcawthor@bellatlantic.net
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Paul
Re: Bond the prop shaft to the boat's grounding system?
Most boats have two steel halves that make up the coupler, some have a rubber vibration isolator sandwiched between the two halves. The boats that do not have the rubber isolator do have the shaft and prop tied into the ground system by the simple fact that the coupler halves are steel and in contact with one another, that assembly is grounded via the engine via the common ground point where everything else should be grounded. Boats with the rubber isolator in the coupler should have the strap as John suggests in his message or a grounding brush, the strap is easier and simpler.Matt Cawthorne wrote: Mike,
This is post might get you many conflicting opinions. On my '36 I do not ground the shaft to the rest of the bonding system. My reason for this is simple. All metal underwater is bronze except the prop shaft and prop. In the absence of any externally applied current the bronze will hold up just fine and will prevent barnacles from growing to boot. The shaft is stainless and must be protected by a zinc. If you bond the existing zinc to more under water metal components the zinc will disappear at an even faster rate. If you had a zinc which gets used up now, you may then find that by the end of the season your zinc disappears and your expensive prop and through hulls become the sacrificial metal! My zinc fell off one year (yes I installed it) and the prop began to experience significant dezincification. The one good thing that can come of bonding your propeller is in the event of a lightning strike your prop would be able to dissipate much more current than your through hulls.
Matt
Matt Cawthorne wrote:Mike Schwartz wrote: I have a Cape Dory 36 with a three bade max prop which has its zinc mounted on the central hub of the prop. There is a hard rubber disc in the drive shaft at the coupler. At present there is no brush connecting the shaft to the boat's grounding system. The zinc just lasts the season. Should I electrically tie the distal shaft to the grounding system?
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Paul
Re: green wire SAFETY GROUND
First I think we need to get the terminology straight so no one gets confused and electrocutes themselves. The ac black is the hot. The ac white is the neutral. The ac green is the safety ground. The hot carries the current to the boat. The neutral returns the unused current back to the supply source (never ground the neutral wire on board). The safety ground is just what it says, its purpose is to safely lead any shorts directly to ground instead of through a device or the operator of an ac device. So yes, it is supposed to become live to dissipate the current to ground, that's its purpose, not a shock hazard. Lets say someone is using a microwave oven on board and the hot side of the circuit shorts into the chassis of the oven, which in turn would rush to ground through the safety ground wire (green) which in turn would trip a breaker or blow a fuse because of the excess current flow beyond the rating of the breaker or fuse. Only one GFCI is needed on board, all other outlets are run off the one GFCI in series, that way the single GFCI protects all the other outlets as well. GFCI outlets simply have a circuit sensor that detects the slightest leak instantaneously and trips faster than a regular breaker or fuse. They should be mandatory on all boats with ac on board. Back to the safety ground (green wire), that wire is your lifeline, it must go to ground. That is how you protect your mate. You may still get a shock if something shorts but you will still be alive.Matt Cawthorne wrote: Dave,
Before connecting the green wire to the ships ground research is in order. I believe that I read in practical sailor that it should not be connected to the ships ground. The two reasons that I can immediately think of are that if your black wire goes open then you can start dumping AC current into the water through the green wire. That can be decidedly unhealthy for any swimmers in the area. Secondly the green wire allows DC current to flow from other boats or earth ground to your through hull fittings. You do not want your through hulls connected to the Pearson owners do you? My recommendation is to get a copy of the ABYC electrical standards if you are going to mess with the AC ground. Some "marine electricians" are not even up on the latest ABYC recommendations.
I bought a silver/silver chloride half cell to check out my system when it goes in to the water. I like the idea of just using a copper plate instead and am sort of regretting having spent the money on the half cell.
Matt
D. Stump, Hanalei wrote: Matt,
Thanks for your reply. I am going to paint all through hulls except the dynaplate before she goes in on Friday. They were painted before, and showed a minimum amount of growth (almost none). The grounding of the 110 vAC is something I'm not too sure of. As I recall, you can ground the green ground wire to the ships ground, but the neutral should never be tied to the ships ground. Of course, if the neutral opens, either on board or on the dock, the ground becomes "live" and then you not only have a galvanic corrosion problem but an electric shock hazard! When I wire Hanaleis' 110v system this spring, I will install GFCI's and circuit breakers in all circuits. This should protect against any stray current(like through my 1st. Mate!), but I'm am still not sure about connecting the green ground to the ships ground?
Can you or anyone else clarify??
I agree with you, I will never leave shorepower connected when I am not in attendance. The lady that owns a Pearson in the slip next to us does that all the time and will eat up a hanging "fish" zinc in a few months. I've tried to tell her, but it hasn't gotten through yet! She was pulled one fall with all underwater bronze a bright red color! And, once, it did eat her prop!
Dave Stump
Captain Commanding
s/v Hanalei CD-30
Our boat has the ac on at all times with the battery charger switched on. The concerns may be justified about leaving ac on if a boat is not properly fitted with appropriate sized zincs. If good condition zincs are installed, and installed properly, then one need not worry about an ac leak as that is the precise purpose of using the zincs, protection. In all the 18 years that I have serviced boats I have yet to have come across any that have had an ac leak to ground. I think the "ac monster" leak is overstated. If there is a galvanic problem on a boat it can usually be attributed to faulty electrical installation practices. Occassionally a dc device has had a ground leak, but rarely. I have worked for several boat manufacturers in the past and none used isolation transformers on the ac service. All used safety ground (green) to the vessels common ground point along with the bonding and dc grounds brought to the same point as well.
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D. Stump, Hanalei
Re: green wire SAFETY GROUND
Paul,
Thank you very much for your reply. It clarifies a lot! I had intended to daisy chain the duplex outlets off of one GFCI protected outlet, so that is a done deal. Your explanation of the ground(green) to the ship is exactly right, and I will do that. Ya know, as I understand it, most galvanic corrosion is caused by 12v current anyway, isn't it? What I mean is that having a hot 12v lead in the water is worse than a 120v hot lead in the water(as far as eating up zincs and fittings), is this correct?
Dave
Thank you very much for your reply. It clarifies a lot! I had intended to daisy chain the duplex outlets off of one GFCI protected outlet, so that is a done deal. Your explanation of the ground(green) to the ship is exactly right, and I will do that. Ya know, as I understand it, most galvanic corrosion is caused by 12v current anyway, isn't it? What I mean is that having a hot 12v lead in the water is worse than a 120v hot lead in the water(as far as eating up zincs and fittings), is this correct?
Dave