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Old 25-10-2009, 06:57   #1
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Zincs Protection

We understood that it is wise to hang a seperate zincs overboard on a cable in the harbours to protect the ones on the hull/rudder.

What cable to use ?

Where to connect the top and how?

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Old 25-10-2009, 07:26   #2
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I always love seeing these things hanging from boats lol. Let me ask you why would you want to do this? Are you having problems with Galvanic corrosion? Do you have zincs on your underwater metals? Are you connected to a shore side power supply?

Just hanging a zinc over the side is useless and sort of silly. If you are having problems the thing to do is find the source of the problem and fix it. Although not likely you can cause more problems by added too much zinc. Not likely by just hanging one over the side though.

Even if the zincs you hang over the side do help with protection they will not "protect" the other zincs they will all waste away together, maybe a bit slower but not that much.

A better investment would be a galvanic isolator for your AC ground, or even better an isolation transformer for the whole system if you got deep pockets.

If you have to do it because it makes you feel better attach the cable to your bonding system or DC ground. It has to be a good electrical connection meaning using a snap clip it useless. If you are having a problem with corrosion lets talk about that so others here can learn some too. If you are not having a problem I suggest you spend your money on something that will do you some good.....like a couple of beers lol

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Old 25-10-2009, 08:14   #3
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I've pondered the same thing about using "grouper zincs" I've seen a lot of hot marinas with every other boats shore power cord hanging in the water. Some extra protection sure wouldn't hurt. Remember seeing a friends prop that looked like red swiss cheese when he hauled.
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Old 25-10-2009, 08:26   #4
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The problem is everyone always swears its something on the other guys boat but 9 times out of 10 I find the problem is really on the boat that is having trouble. The best thing to do is make sure your boat is right then start looking for outside sources. If your boat is right the odds are better that even if the guy next to you is not you will be protected. I do this all the time as part of my job but truth be told I checked my boat not long ago and found some problems. So never assume the trouble is not yours. Your friends prop was likely the cause of a fault on his boat.

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Old 25-10-2009, 09:21   #5
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galvanic isolator for your AC ground

Thank you for the advise and please explain in 'common' language what the above means or is.

I am ' not so good' with electricity to put it mildly
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Old 25-10-2009, 09:33   #6
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Let me ask you are you having trouble with underwater metal corrosion? Do you have zincs on your underwater metal? On the prop shaft or I think you mentioned your rudder? If so do they last between haul outs?

If i know this I can help more, this is sort of detective work after all lol.

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Old 25-10-2009, 10:59   #7
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Sailvayu, not clear yet but when inspected will contact you directly ; the original question was a result of a discussion I had recently

Appreciate your input a lot as this issue troubles many sailing folks
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Old 25-10-2009, 11:37   #8
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Wise anodes...

I hang a coupe of anodes off Boracay (44' steel cutter) when we are on a mooring or in a marina. There are a few advantages that I see:-
1) A visible indication every time I take them up of the state of all anodes on the hull.
2) Some additional protection (I hang the anodes amidships about 4' down).

Having had all anodes vanish within months I now take every precaution that I can.

With my steel boat I connect them to bare metal on a frame. With a fibreglass boat I'd ask a marine electrician if they should be connected to the engine block, stern gland, through hulls or somewhere else.
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Old 25-10-2009, 13:09   #9
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Originally Posted by Boracay View Post
... With my steel boat I connect them to bare metal on a frame. With a fibreglass boat I'd ask a marine electrician if they should be connected to the engine block, stern gland, through hulls or somewhere else.
And that marine electrician will tell you that sacrificial anodes, whether permanent fixed, or portable ‘fish’ type, must be electrically connected to the metals they are to protect.

Hence, “Grouper Zincs” must be connected to the boat’s bonding system, which ties all underwater metals together (at the same potential).

This might most easily be accomplished by running a #6 AWG cable from a bonded metal component (prop’ shaft grounding brush, through hull, or engine block) to an electrode above deck (for convenience).

For instance, I’ve used a threaded bolt through the threaded mast (from inside) with a nut on the outside, and about 1.5 - 2" of stud extending beyond the nut as a clamp electrode. I put a nylok or cap nut over the end of the stud when not in use. Obviously, the mast must be bonded.
I've also clamped the grouper cable to a bonded stay. This is a MUCH less satisfactory electrical connection.

As Wayne notes, these may not provide very good electrical connections, unless the grouper cable clamp, and electrode are clean (pristine) and tight.
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Old 25-10-2009, 14:22   #10
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If the zincs on the hull are fine then why bother? Just make sure you are isolated from the shore power (ground). I think they call it the galvanic isolator or something.

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Old 25-10-2009, 19:17   #11
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If the zincs on the hull are fine then why bother? Just make sure you are isolated from the shore power (ground). I think they call it the galvanic isolator or something.

b.

You do not want to be isolated from the shore ground that would be dangerous. The galvanic isolator is a one way diode that prevents stray currant from coming from the shore (a fault on another boat on the same dock circuit) into your boat, but it will let fault currant from your boat to the shore ground. If fault currant does not have this path it will find it through your underwater metal or possible through you if you touch the underwater metal. One more reason you need to have your AC and DC grounds connected on the boat.

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Old 25-10-2009, 20:23   #12
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I was not clear and caused confusion. I meant having the galvanic isolator to sort out the original problem.

In my boat the AC and DC are completely separate thus the need for the isolator eliminated.

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Old 25-10-2009, 20:52   #13
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A couple weeks ago I started using a grouper as added protection because there is a problem somewhere around me. No its not my boat. I am not connecter to AC and have disconnected my battery. I connected the grouper to my shaft. Gord explained how. I am doing this to monitor what is going on. You do need to have propper zinc protection. You do need to check your zincs often but sometimes it is wise to have a little extra until the next haul out.
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Old 25-10-2009, 21:59   #14
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A lot of unclear info in this thread.... just some points for clarification:

A zinc protects the under water metal part(s) it is electrically connected to. So if it is connected to your prop and your prop is electrically connected to your shaft, both will be protected.

If you have a bonding system and the zinc(s) connect to that, all metal parts will be protected. But a zinc can disappear fast if it is too small. You need to have a certain minimum surface area of zinc and the best way to find out how much is by checking how fast they disappear. If it's too fast, you need more surface area.

Whenever something changes around you, like you move your boat somewhere else, or another boat moves into the marina etc. the situation changes. Even if your zincs did just fine in the past, you must continue checking them.

Some zincs are expensive, like my big Maxprop zincs. We use a grouper zinc whenever we are at anchor or moored for more than a couple of days. The grouper zinc has the same surface area as all the fixed zinc together. This means, that the other zincs will last twice as long. We have a bonding system, so we can connect the grouper zinc to any metal part. We use a mizzen capshroud.

Grouper zincs are expensive too. You can grab (used) zincs for free around every boatyard. Throw 'm in an old pot, melt them on a burner and cast them in a sand mold with a piece of awg #10 wire. Strip the couple of inches that go in the zinc.
If you buy one grouper zinc, you can press it in the (moist) sand to create exact replica's. Make new ones before using your last one ;-)

Isolating yourself from the shore power ground-wire is the best thing you can do in a marina, but it needs to be done safely and that means an isolation transformer. A galvanic isolator uses diodes in an anti-parallel circuit so that is a 2-way circuit but it blocks the current for very low voltages. It is unreliable and less safe than a transformer.

for Barnie: it doesn't matter if your AC and DC are separated. That does not protect your under water metals from an shore AC problem. It only helps if the shore AC is not connected to anything else than the outlets in the boat, so no ground plates or ground-to-metal-part connection anywhere. (which the ABYC does not recommend while it is the other way around in the EU). An isolation transformer is always the best option but cost more and weighs more.

cheers,
Nick.
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Old 26-10-2009, 04:07   #15
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I utilize a fish zinc in addition to a shaft zinc, when at our home dock. The advantage is that the shaft zinc lasts years and when the fish zinc finally deteriorates-3 years on the last one-its easy to change.

But you have to attach it to the shaft, engine or transmission, etc to get the proper results.

Another tip...mimize stray current from other vessel...disconnect you shore power cord when not necessary. Bob
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