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Old 19-04-2011, 06:32   #1
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What Do You Zinc ?

Im planning to dive in and check my zincs today. Attached are pictures I took during the survey (6 months ago). I read somewhere that they should be changed when about half is gone

My questions are....

1: Would you replace the zincs in the pictures? (the plate seems worse than the others)
2: How does one change the zinc plate? - the bolts look impossible
3: Anything else I should check when I dive? (other zinc or places)
4: Is it really possible to change them without scuba equipment?






As always any additional info is appreciated, links, videos, etc.

thank you
austin
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Old 19-04-2011, 06:56   #2
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Re: What do you Zinc?

If they haven't changed since the survey, leave them alone but carry spares.

Any time at anchor just put on a mask and take a look. Takes about 1 minute. You should be able to free dive them with no problem.

Electrolysis decay on the zincs varies with location.
Some marina's have stray electrical currents that will eat away zincs in no time...
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Old 19-04-2011, 07:16   #3
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Re: What do you Zinc?

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Originally Posted by Unicorn Dreams View Post
Electrolysis decay on the zincs varies with location. Some marina's have stray electrical currents that will eat away zincs in no time...
In addition, using zinc for your anode material may not be the best choice for your location. Other choices include anodes made of aluminum or magnesium, depending on your water chemistry. Magnesium should be used in fresh water only. Aluminum may protect better than zinc in salt water. (See Cruising World, Feb. 2011, pp. 64-68.)
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Old 19-04-2011, 07:42   #4
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Re: What do you Zinc?

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4: Is it really possible to change them without scuba equipment?
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Originally Posted by Unicorn Dreams View Post
You should be able to free dive them with no problem.
You might be able to, you might not. Try this: assemble a shaft zinc around a boat hook or mop handle. Put that on the floor of the Vee berth. Now, take your tools up on deck. Get your hands all wet, take a deep breath, grab your tools and go forward, lie down on the vee berth while holding your breath and disassemble the zinc. Don't drop anything!

Many folks can't hold their breath for even 20 seconds under water. If you are a good breath holder, then Unicorn is right.
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Old 19-04-2011, 07:50   #5
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Re: What do you Zinc?

Haha, great idea doug.

Anyone have any words about the zinc plate and the bolts holding it (to what im sure is the grounding plate)? What are the mechanics behind it, how are things put together/taken apart etc? Its the only part that doesnt seem straight forward.

austin
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Old 19-04-2011, 08:06   #6
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Re: What do you Zinc?

Zincs should be replaced before their 50% point, to remain effective. They also need to be de-scaled (= cleaned off), with a putty knife, once a month or so in warm months.

That strut "could" be protected by the shaft zinc, if the strut's interior end is electrically connected to the shaft with a bonding wire & shaft brush.

Lots of luck on that plate! If you feel that it is needed, I would bond in silicon bronze machine screws with the 2 legs pointed out, & the plate held on with silicon bronze nuts. That way there is no caulk seal to deal with in replacing the Zinc, and you can change it with the others using just a mask & fins.

BTW... be sure you have a "galvanic isolator" in the boat's green wire, to separate your boat's ground from the others in the marina!

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Old 19-04-2011, 08:24   #7
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Re: What do you Zinc?

Thanks mark.

So the plate is an extra precaution?

Maybe another question is where all do zincs need to be on sailboats? Only on the shaft? I appear to have some on the skeg too (seen in image). The only videos I can find are of outboards, and they seem to have many.

The plate located on the port side about the same location as the mast (about a foot away from the mast, the back is visible through the bilge). There is a green ground going to it from the mast, and what looks to be a few other green wires from a few other locations. The guy who wired the boat seems to have everything by the book on this boat.

thanks again all
austin



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Old 19-04-2011, 08:50   #8
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Re: What do you Zinc?

The plate doesn't look like a zinc, it looks more like a grounding plate, either for a radio or for lightning protection..
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Old 19-04-2011, 11:44   #9
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Re: What do you Zinc?

Here are the results (a bit blurry... video stills)
I think ill replace the one on the shaft as soon as I get the chance. Are there standard sizes?





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Old 19-04-2011, 13:40   #10
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Re: What do you Zinc?

theway,
To obtain a zinc for your propeller shaft, you need to specify the diameter.

Alain
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Old 19-04-2011, 19:56   #11
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Re: What do you Zinc?

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Zincs should be replaced before their 50% point, to remain effective.
This is a claim that everybody seems to make but I'd suspect that 99% of the claimants are just repeating what they've heard rather than having independently determined its veracity.

Personally, I have never believed it and have acted accordingly and with no adverse consequences to date. I wait till an anode is 90% gone and then replace it. I judge that the last 10% would do as good a job as the first 10% but am mindful that being left with no protection is not worth the risk in extracting that last little bit.

To my mind, if there is some zinc left then the anode has the capacity to do the job that it is designed to do. My experience says this theory holds true.

Keep in mind that the anode depletes at the same rate (under the same conditions) no matter what its original size, and 50% remaining of a 5kg anode is 100% of a 2.5kg anode. That is, half the big one is exacly the same as a whole (brand new) smaller one.

I also figure I've saved a bucketload of cash over the years by using the anodes for their near full useful life.

Convince me otherwise

Re the underwater changeover query, I'd never do it. Scrubbing the anodes to see just how much zinc is left is easy underwater and should be done but that's all I'd do. Best to careen against a pole or wall or do a quick slipping and make sure the job's done properly imo.
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Old 19-04-2011, 20:03   #12
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Re: What do you Zinc?

Talk about making a major issue out of two paper bags...
It's a zinc! How much damage are you willing to sacrifice to save a few dollars? Replace the things before they get that eroded. The concept that a zinc is still good at 90% eroded is fundamentally wrong as these anodes are never 100% zinc. Therefore, you cannot tell from visual inspection how much zinc is actually remaining. Spend the money and replace it/them or risk sacrificing much more expensive parts - your choice.
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Old 19-04-2011, 20:09   #13
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Re: What do you Zinc?

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Talk about making a major issue out of two paper bags...
It's a zinc! How much damage are you willing to sacrifice to save a few dollars? Replace the things before they get that eroded. The concept that a zinc is still good at 90% eroded is fundamentally wrong as these anodes are never 100% zinc. Therefore, you cannot tell from visual inspection how much zinc is actually remaining. Spend the money and replace it/them or risk sacrificing much more expensive parts - your choice.
Another herd man who doesn't like being thus exposed...
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Old 19-04-2011, 20:21   #14
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Re: What do you Zinc?

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Another herd man who doesn't like being thus exposed...

"thus exposed" to common sense? Please enlighten the rest of us idiots on the chemical composition of a typical zinc anode and how you can determine it's true composition by sight once partially eroded. Do tell.

"Scrubbing the anodes to see just how much zinc is left" shows you nothing about the available zinc still present.

This is not unlike a debate on the interval between changing your car's oil. some people think it's a waste of their time to do it until it turns to sludge because of the "so far, so good" mentality.
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Old 19-04-2011, 20:38   #15
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Re: What do you Zinc?

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Talk about making a major issue out of two paper bags...
It's a zinc! How much damage are you willing to sacrifice to save a few dollars? Replace the things before they get that eroded. The concept that a zinc is still good at 90% eroded is fundamentally wrong as these anodes are never 100% zinc. Therefore, you cannot tell from visual inspection how much zinc is actually remaining. Spend the money and replace it/them or risk sacrificing much more expensive parts - your choice.
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Originally Posted by S/V Illusion View Post
"thus exposed" to common sense? Please enlighten the rest of us idiots on the chemical composition of a typical zinc anode and how you can determine it's true composition by sight once partially eroded. Do tell.

"Scrubbing the anodes to see just how much zinc is left" shows you nothing about the available zinc still present.

This is not unlike a debate on the interval between changing your car's oil. some people think it's a waste of their time to do it until it turns to sludge because of the "so far, so good" mentality.

Wow, we've got one blood pressure bursting angry dude here. One tip pal, no-one is ever convinced by the views of an eye-bulging shouter.

For those out there who are interested in an alternative view backed up by considerable real life experience and who are willing to give it a try, then please do so and report any experiences to this board for our erudition.

Those whose minds are closed - like Illusion - need not apply. Allow those of us who like testing rather than swallowing to go about our merry ways.
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