Bonding circuit question

While working on my diesel fuel tank this weekend, I noticed that (by means of having to crawl over them) the prop shaft struts are not attached to the bonding system. The shafts have zincs that have lasted 1 year between replacements, but do the struts require bonding? While there, it is easy to accomplish, if necessary.

If the shafts have their own zincs, then they're protected by those.

Ken

If it has a zinc, it shouldn't need to be part of the bonding system.

Ted

Does that go for the rudder as well?

does it not need to be bonded if it has a zinc? (I think I just tied my tounge in a knot)

what_barnacles said:

Does that go for the rudder as well?

does it not need to be bonded if it has a zinc? (I think I just tied my tounge in a knot)

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Yes.

Ted

Since the shafts run through rubber cutless bearings, how are they protected?

The Shaft is connected to the trasnmission. The transmission in turn is connected to the engine, which is connected to the bonding circuit.
(ankle bone connected to the leg bone.....)
The Zinc is "Sacrificial" therefore will deplete itself rather than the shaft (or other devices such as rudders).

Shafts and rudders should be bonded. And in most cases they are. In the case of the shaft, it's bonded by the fact it's coupled to the engine by the coupler to the transmission. If your using a isolation coupler you make the bonding connection with a strap/wire that that electrically connects the shaft to the transmission by the bolts on each side of the coupler. Or a bonding brush that rides on the shaft while connected to the bonding system.

In the case of the rudders, they are usually connected to the bonding system by the fact that rudder stocks are connected to the bonding system through the quadrant or arms attached to the stocks. Which in turn are connected to the bonding system one way or anther.

Here is an article from Passagemaker that may make sense. I use this sometimes when explaining the bonding system to my customers.

http://www.passagemaker.com/channels/bonding-systems-and-corrosion/

kchace said:

If the shafts have their own zincs, then they're protected by those.
Ken

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O C Diver said:

If it has a zinc, it shouldn't need to be part of the bonding system.
Ted

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Ken, Ted
I agree technically with your statements but in practical terms see a problem.
The problem I see is that if there were no bonding system all of the underwater components w an anode would be protected - but only those components.
If only unprotected components (w/o anodes) are bonded they are still no protected - in fact the purpose of the bonding system is to tie all underwater components together so they are protected by the (few) components that have anodes.

From the article below that seadogmike linked...

"Second, and relevant in PMM’s test vessel case, when the bonding system is connected to a sacrificial anode, as it always should be, then that anode will afford protection to all metals that are interconnected and immersed in the same body of water. Such an arrangement makes it easier for a vessel operator to protect multiple metals by maintaining just a few anodes."

Goldenstar38 said:

... do the struts require bonding? While there, it is easy to accomplish, if necessary.

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Based on my above post - my answer would be - if you want to protect the struts they should be bonded - if it's easy to accomplish Why not?

The bonding system has to be tied to other protected (w/ anodes) components - and sufficient qty / area to protect ALL of the underwater components.

The question is the struts, not the shafts.

meridian said:

The question is the struts, not the shafts.

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You're right. I misread it. The struts should be bonded via bonding wires going from their mounting bolts to the bonding system.

Capt.Bill11 said:

You're right. I misread it. The struts should be bonded via bonding wires going from their mounting bolts to the bonding system.

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+1

Perfect! While down there, I will do this next. Have the bonding wire already as I replaced many sections when I purchased the boat 2 years ago due to their poor condition, just need the correct terminal ends.
Thanks for the clarification.

I'm an isolationist If the struts are not bonded now, and are not showing any signs of electrolysis, I definitely wouldnt waste time and possibly creating a new problem.

Being an isolationist is fine. As long as you are totally committed to the cause.

As in all your underwater fittings are isolated.

Capt.Bill11 said:

You're right. I misread it. The struts should be bonded via bonding wires going from their mounting bolts to the bonding system.

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Wow, so did I. That's what I get for responding with brain not engaged. As others have said, struts should definitely be bonded or they won't be protected.

Ken

you crawled over the struts? Is the boat upside down?

The struts on my sporty are "bonded" to my aluminum tower, for a lightning path. Other than that no underwater metal is "bonded" to any other. I have zinks on my shafts for the simple reason of dissimilar metals. My shaft zinks last a very long time, on the order of over three years. I have ZERO electrolisis, none. I have meticulously "debonded" every boat I have owned, including this one. It works for me, very well. But old habits die hard. Bond away.

No, what barnacles, I was over their (through hull) mounting bolts inside the boat.

kulas44 said:

The struts on my sporty are "bonded" to my aluminum tower, for a lightning path. Other than that no underwater metal is "bonded" to any other. I have zinks on my shafts for the simple reason of dissimilar metals. My shaft zinks last a very long time, on the order of over three years. I have ZERO electrolisis, none. I have meticulously "debonded" every boat I have owned, including this one. It works for me, very well. But old habits die hard. Bond away.

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As I said, as long as you're fully committed to isolating all your underwater fittings you should be fine.

goldenstar38 said:

no, what barnacles, i was over their (through hull) mounting bolts inside the boat.

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DOH! :d

meridian said:

Since the shafts run through rubber cutless bearings, how are they protected?

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The shafts on my boat have a piece of spring metal with an electrode that is bonded. Kinda like brushes in a motor.

Correct Bill, and allow for lightning protection. Its much simpler than trying to keep up with a bonding system, and as far as I can tell it works better.

Actually, partially bonding a boat works quite well to...

Even according to several writers like Calder, etc.

One article I just read...think it was a West Advisor maybe, said that bonding was archaic...but needed for safety rather than corrosion.

psneeld said:

Actually, partially bonding a boat works quite well to...

Even according to several writers like Calder, etc.

One article I just read...think it was a West Advisor maybe, said that bonding was archaic...but needed for safety rather than corrosion.

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I'd like to see the Calder quote. Because he used to say the it was an either or thing. No in between.

At least that is what I recall reading in his book. I'll have to look at it again tonight.

May have not been Calder, but if he didnt, it doesn't matter as I have seen it plenty and as I have posted have read other respected marine writers describe it.

By definition, an isolated underwater fitting of good bronze should be unaffected in all but the rare case.

All 3 of my liveaboards have had mixed bonding, isolation with no issues.

psneeld said:

May have not been Calder, but if he didnt, it doesn't matter as I have seen it plenty and as I have posted have read other respected marine writers describe it.

By definition, an isolated underwater fitting of good bronze should be unaffected in all but the rare case.

All 3 of my liveaboards have had mixed bonding, isolation with no issues.

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Hmmm... If you say so. Everything I've always read or been told is that either everything needs to be bonded or nothing.

Because if everything is bonded but one fitting, even if that fitting is bronze, becomes un-bonded that fitting can become like a zinc and leech away over time.

Capt.Bill11 said:

Hmmm... If you say so. Everything I've always read or been told is that either everything needs to be bonded or nothing.

Because if everything is bonded but one fitting, even if that fitting is bronze, becomes un-bonded that fitting can become like a zinc and leech away over time.

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Without a bonding wire or another metal attached to it ....there is no circuit if the solitary metal is far enough away.


Its the metals that are different and connected together like props and shafts, bronze rudder blades on stainless shafts or all the above in close proximity that has issues.


On page 148 of his second edition Mechanical/electrical...., Calder does make it sound like all fittings should be unbounded...but then goes on to say stainless shafts and bronze props need zincs (plus other setups)...well...at what point does totally unbounded and partially zinced matter? Not much according to my reference cell as long as the isolated bronze thru-hull is far enough away.


I know I should link something up...been on the road with very spotty WIFI.... but I have the reference cell and have been checking boats for years and am just passing along what I have observed, had on my boats and read.