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20-12-2012, 11:41
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#16
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Moderator Emeritus
Join Date: Sep 2006
Posts: 4,663
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Re: Hanging The Fish Zinc In The Marina Trick
Zinc fish can be useful, but you should also look at your boat's shore-power connection. Adding a diode ground-isolator, or better-yet, an isolation transformer, can greatly reduce your electrolysis issues.
When VALIS was in San Francisco, I was able to keep the batteries charged with my solar panels, so I had no shore-power connection and my Zincs lasted a long time. Since I moved VALIS up to the PNW, I've found I need to run a small heater to keep the condensation from being a problem. This means I need to run shore-power. I installed a diode isolator ( this one), and hang a Zinc fish from the backstay chainplate. We shall see how my zincs hold up. I need to make some current measurements -- I don't know if I really need the fish.
__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
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20-12-2012, 18:27
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#17
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Registered User
Join Date: Oct 2005
Posts: 6,185
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Re: Hanging The Fish Zinc In The Marina Trick
I try to keep the shorepower unplugged during the daytime when the panels are getting full sun, and anytime we leave the boat for a while. With us onboard at night in the marina we suck down power and I'd rather not cycle the batteries that much.
Here's the one I've seen everywhere:
http://www.defender.com/product.jsp?...9712&id=150598
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21-12-2012, 00:53
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#18
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Moderator
Join Date: Jul 2007
Boat: Bestevaer.
Posts: 14,678
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Re: Hanging The Fish Zinc In The Marina Trick
You can make your own. Most boat yards have lots of old zincs lying around.
Some plastic coated SS wire is all that's needed. It is difficult to get a low resistance connection, but if drill a few holes in the zinc thread the wire in and out then use a bolt to squash the bare wire against the zinc or use a prop shaft zinc, but squash the bare wire between the two halves.
Check the resistance of the connection every so often.
It's cheap and green.
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21-12-2012, 07:24
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#19
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Registered User
Join Date: Jun 2012
Posts: 3
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Re: Hanging The Fish Zinc In The Marina Trick
I fitted an 'over the stern' fish anode 6 months ago, for marina use, at which time the shaft anode was completely intact. The distance between the fish anode and the prop is about 4 feet.The fish was bolted to the pushpit base stud which was in turn permanently attached directly to the battery negative pole and the connections were good. The vessel is GRP, is not bonded and has a single anode. There has been no wear at all in the fish anode during the 6 months. I dived on the shaft anode the other day and it was hanging loose on the shaft well over 50% eroded whereas the last time I inspected it 2 months ago it was still fully intact. In other words the hanging the anode over the side was a waste of time as protection against galvanic corrosion as distinct from electrolysis. Is there any point in an 'over the side anode' in an unbonded vessel?
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21-12-2012, 07:30
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#20
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Registered User
Join Date: Oct 2007
Location: Lakewood Ranch, FLORIDA
Boat: Alden 50, Sarasota, Florida
Posts: 3,464
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Re: Hanging The Fish Zinc In The Marina Trick
Quote:
Originally Posted by Rietsail
I fitted an 'over the stern' fish anode 6 months ago, for marina use, at which time the shaft anode was completely intact. The distance between the fish anode and the prop is about 4 feet.The fish was bolted to the pushpit base stud which was in turn permanently attached directly to the battery negative pole and the connections were good. The vessel is GRP, is not bonded and has a single anode. There has been no wear at all in the fish anode during the 6 months. I dived on the shaft anode the other day and it was hanging loose on the shaft well over 50% eroded whereas the last time I inspected it 2 months ago it was still fully intact. In other words the hanging the anode over the side was a waste of time as protection against galvanic corrosion as distinct from electrolysis. Is there any point in an 'over the side anode' in an unbonded vessel?
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Sounds like you made the common mistake of assuming the path between your shaft zinc and external anode is effective. It sounds like it isn't!
There are way too many connections and resistive uncertainties between the two making the external zinc anode useless especially when connected, as many people do, to a convenient location such as a chainplate or shroud.
The most effective method is to either connect the external anode directly to the shaft or when impractical as closely as possible minimizing both the length and number of intermediate connections.
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21-12-2012, 07:33
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#21
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Registered User
Join Date: Sep 2009
Location: Houston
Boat: '76 Allied Seawind II, 32'
Posts: 9,626
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Re: Hanging The Fish Zinc In The Marina Trick
The guppy will work, but only if in close proximity to the metal being protected and in almost perfect electrical contact with the metal being protected.
Ours (when I still had it) measured 8" from the prop, and electrically 0.03 Ω from the prop through the negative start battery terminal.
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21-12-2012, 20:18
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#22
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Registered User
Join Date: Aug 2009
Location: Bahamas/Florida
Boat: Solaris Sunstar 36' catamaran
Posts: 2,686
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Re: Hanging The Fish Zinc In The Marina Trick
Quote:
Originally Posted by Matt sachs
What problems are created with to many zincs?
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In wooden vessels it is possible to cause deterioration to the wood in areas such as where through hulls are located. There was an interesting article about this some years ago in (I believe) Wooden Boat magazine.
__________________
Sail Fast Live Slow
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27-09-2023, 12:59
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#23
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Registered User
Join Date: Sep 2023
Posts: 1
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Re: Hanging The Fish Zinc In The Marina Trick
Hello All,
Where would be the best place to connect the hanging anode wire within the boat.
Thanks
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27-09-2023, 13:02
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#24
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Hull Diver
Join Date: Oct 2006
Location: Under a boat, in a marina, in the San Francisco Bay
Posts: 5,427
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Re: Hanging The Fish Zinc In The Marina Trick
Quote:
Originally Posted by rperla
Where would be the best place to connect the hanging anode wire within the boat.
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Remembering that the anode must be in direct electrical contact with the item being protected, as close as possible to it and with as short a run of wire as possible.
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28-09-2023, 08:18
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#25
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Registered User
Join Date: Aug 2021
Location: PNW
Boat: 35 Ft. cutter, custom
Posts: 2,214
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Re: Hanging The Fish Zinc In The Marina Trick
Quote:
Originally Posted by FSMike
In wooden vessels it is possible to cause deterioration to the wood in areas such as where through hulls are located. There was an interesting article about this some years ago in (I believe) Wooden Boat magazine.
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Yes, there were some articles in WoodenBoat, ('70s>'80s?,) that were written by Giffy Full, a surveyor who became quite a legend in the NE.
The up-shot was that underwater bronze that is electrically isolated does not need any zinc protection and that connecting zincs to bronze either directly or thru a bonding scheme led to over-protection, which caused de-lignification of the wood surrounding the bronze fitting.
I've observed that several times in the past, the wood gets a white fuzz on it.
The can-of-worms started wiggling when boats started being loaded-up with all kinds of inferior metals and "sketchy" AC/DC electrical systems.
Zincs became a "Band Aid" which, (unknowingly at the time,) contributed to a lot of wooden boats having severe damage.
__________________
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