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Old 14-12-2019, 16:29   #31
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Re: Prop shaft bonding brushes?

@boatpoker #29: +1
@gordmay #30: +1. With the limitations of the motor brush/phosphor bronze arm I discussed in my #26.
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Old 14-12-2019, 17:37   #32
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Re: Prop shaft bonding brushes?

I meant to say that my three one pound zincs, and my five shaft zincs on the swim grid. They are all working, really well. What I was trying to say is the alternator never gets used because of the solar panels, and no battery charger which I think is the biggest reason.
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Old 14-12-2019, 17:38   #33
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Re: Prop shaft bonding brushes?

Quote:
Originally Posted by suiramor View Post
On my Beneteau 46 the only sacrificial anode is at the end of the prop shaft (propeller end). However, it seems that the shaft is bonded to the rest of the system with a copper strap, which appears to be connected to the fiberglass (!) part of the shaft enclosure (see picture). Even if I am wrong and the enclosure is metal (I have not checked yet - difficult access), that's not the best connection to the anode anyway. I heard of carbon brushes one can get to create a better connection to the moving shaft but the only one I am finding on the web is ProMariner, which looks flimsy and has mainly bad reviews. Does anyone know where I can get something more substantial? Something where the contact carbon is on a spring so it fits more snugly to the prop? Am I correct even relying on the prop anode or should I be considering adding something fixed to the hull?
slight change/varient in subject,how would lightning strike affect mast electronics/electrodes,on a steel yacht?pls excuse my interruption but i can never see any info on steel yachts or threads,all input appreciated.
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Old 14-12-2019, 17:53   #34
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Prop shaft bonding brushes?

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Originally Posted by rogue trader View Post
slight change/varient in subject,how would lightning strike affect mast electronics/electrodes,on a steel yacht?pls excuse my interruption but i can never see any info on steel yachts or threads,all input appreciated.


I don’t think you can get an honest real answer, there have been boats hit directly and little if any real damage, then there have been some that weren’t hit, it was a nearby stike and pretty much everything electric is fried.

However it’s my opinion that a metal boat, steel or aluminum would most likely fare much better than a plastic boat.
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Old 14-12-2019, 17:56   #35
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Re: Prop shaft bonding brushes?

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I don’t think you can get an honest real answer, there have been boats hit directly and little if any real damage, then there have been some that weren’t hit, it was a nearby stike and pretty much everything electric is fried.

However it’s my opinion that a metal boat, steel or aluminum would most likely fare much better than a plastic boat.
Agree ..... Faraday.
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Old 14-12-2019, 18:23   #36
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Re: Prop shaft bonding brushes?

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Originally Posted by CharlieJ View Post
@boatpoker #18: +1

@rbk #19: You have them reversed; bronze is more active (anodic) to passivated stainless steel (cathodic).
Passivated yes. Active (typical) no. More so when comparing to a quality bronze alloy.
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Old 14-12-2019, 21:03   #37
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Re: Prop shaft bonding brushes?

@rbk #36
Your meaning is unclear. A review of the galvanic series validates my original response.
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Old 14-12-2019, 21:38   #38
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Re: Prop shaft bonding brushes?

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@rbk #36
Your meaning is unclear. A review of the galvanic series validates my original response.

Magnesium and Magnesium Alloys
-1600 to -1630
Zinc
-980 to -1030
18.8, 3% Mo Stainless Steel, Type 316 (active in still water)
-600 to -710M
Silicone Bronze (96% Cu Max, 0.80% Fe, 1.50% Zn, 2.00% Si, 0.75% Mn, 1.60% Sn)
-260 to -290
Bronze ASTM B62 (thru-hull) (85% Cu, 5% Pb, 5%Sn, 5% Zn)
-240 to -310
18-8 Stainless steel, Type 304 (passive)
-50 to -100
Stainless Steel Propeller Shaft (ASTM 630: #17 & ASTM 564: #19)
-30 to +130
18-8 Stainless Steel, Type 316 (passive) 3% Mo
0.0 to -100
Graphite
+200 to +300

Clearer?
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Old 14-12-2019, 22:21   #39
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Re: Prop shaft bonding brushes?

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Why is it that mainly north american boat owners are so obsessed with bonding every piece of metal on their boats. Is there something special about that part of the world that requires it whereas most of the rest of us don't have this problem, or is it some sort of custom or belief that one must follow that which is passed down, or what? I have zero bonding on my old fibreglass tub, with no issues, no one around me has either and the only bonded boats that I have heard of around here are steelies or American imports. Is this a routine practice in Europe as well?
Please, what would the cause of the differing experience/custom be?
Indeed, many surveyors and thus boat owners and servicers are obsessed with the green wires between every piece of metal in sight. And there is a misconception that sea strainers and pipework can be protected through the bonding system (protection is only effective for a distance of aprox 3X the inside diameter, from the outside of the hull).

In the US and Canada recreational boat manufacturers are required by federal law to bond all underwater metal parts and connect to the Equipment Safety Grounding conductor if the vessel has an electrical service of higher than 50 volts. Debate of merits is irrelevant, compliance is required, so all production boats made in or for the North American market that have AC electrical service are made so. In the UK and Australia, NZ, and I guess much of Europe Ground Fault Protection is widely universal. I don't know about the regulations abroad, but the necessity for bonding metal parts is much less so because of this. Requirements for more extensive GF protection are just starting to be implemented here, so boats will continue to be bonded for a long time, probably forever.

Besides satisfying the government, the bonding system reduces the risk of electrical shock. Besides that, it allows the delivery of protective current from a common anode to the underwater parts. Once upon a time, hull fittings were by and large all made from very high quality alloys, bronze with 3-4% silicon, less than 1-2% zinc and lead combined, and the attention to process that produced a consistent composition throughout the metal. These parts did indeed last 30 or more years without cathodic protection, but with it they would last much longer. The good stuff just isn't made much anymore, few are willing to pay for it and not many manufacturers remain dedicated to that level of quality. As noted up the thread, some pretty low standards have been set. Accountants rule in business. One buys a boat, or goes to a shipyard or chandlery with a good name and assumes the material will be fit for the purpose, at least, but even that much may be a leap of faith.

Every piece of metal is an array of dissimilar metals. Each grain is different. In some materials the differences are infintesimally small but that's not so with the stuff under our boats today. Though arguments may be made to except certain marine aluminium alloys and high-silicon bronze, all of our underwater metal parts need protection if they are to last. You got to protect the cheap stuff so it doesn't rot out from under you, and the good stuff cause you never want to have to pay to replace it.

Simply connecting fittings together without an anode in the circuit makes anodes of the lower grade materials. Anodes corrode, cathodes are protected. Where each part had its own small reaction potential much greater differences are now involved. A proper bonding system and zinc makes one anode, everything else cathodes. The differences between the range of marine bronze and stainless alloys is nullified, they all react with the one anode as cathodes.

Debates over whether any underwater part is protected or corroding due to reaction with other parts can be answered with a multimeter and a home made probe using a zinc pencil. The relative corrosion resistance of any bronze/brass part can also be determined. I made a detailed post on this years ago and will see if I can locate it.
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Old 14-12-2019, 23:04   #40
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Re: Prop shaft bonding brushes?

http://www.cruisersforum.com/forums/...rina-8445.html

Posts 9 & 13.
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Old 15-12-2019, 05:51   #41
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Re: Prop shaft bonding brushes?

@rbk #38:
In the real world stainless steel develops a passive film almost immediately when exposed to seawater therefore the active value is of interest only in areas where oxygen starvation occurs. Thus my comment.
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Old 15-12-2019, 05:54   #42
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Re: Prop shaft bonding brushes?

@EngNate #39: Spot on with the exception of one typo;
Quote:
Simply connecting fittings together without an anode in the circuit makes anodes of the lower grade materials.
Underlined should clearly be "cathodes".
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Old 15-12-2019, 09:11   #43
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Re: Prop shaft bonding brushes?

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@rbk #38:
In the real world stainless steel develops a passive film almost immediately when exposed to seawater therefore the active value is of interest only in areas where oxygen starvation occurs. Thus my comment.
Self passivation does occur but not consistently across the surface leading to rust spots and pitting which can lead to deep pitting and crevice corrosion.
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Old 15-12-2019, 09:36   #44
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Re: Prop shaft bonding brushes?

Crevice corrosion will occur in areas of oxygen starvation, e.g.; the SS shafting inside a cutlass bearing. This area is oxygen deficient and the strongly adhering passivation film will break down exposing SS that is active and anodic to the rest of the shaft. Crevice corrosion ensues.
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Old 15-12-2019, 09:38   #45
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Re: Prop shaft bonding brushes?

@EngNate #39
Further, the addition of a bonding system to a vessel is one more system that requires maintenance for it to perform correctly. Most of the bonding connections are in or very close to the bilge and maintaining a low resistance (< 1 ohm) connection between the bonding wire and the underwater metal component can be challenging.
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