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Subject: Re: Re: TWL: Unzincs
doughoople@XXX.XXX
Date: Wed May 01 2002 - 22:37:15 EDT
So let me get this straight:
There's currently no prop zinc or shaft zinc on Maņana?
Are the prop shafts directly tied to the bonding system (shaft brushes, etc.)?
Is your prop still alive? Is the transom zinc 'electrically proximate' enough to actually protect the prop from the shaft?
This also takes us to another question, and that is, does the prop shaft interact with the shaft log?
Your experience ('white fuzziness' at the stuffing box end) would seem to indicate that it does, although I've heard the argument that says the shaft is isolated from the shaft log by the packing material. Given that water flows through this area in a typical arrangement (i.e., not dripless), that would provide the 'upper' coupling for the galvanic cell (or is that still considered just part of the electrolyte? I'm so confused...).
I may have part of the answer to that this weekend. I'll check the shaft log voltage reading when the prop zinc goes on and see if that makes a difference. I'm not bonded right now, so that should be pretty conclusive.
Thanks for the info. And don't forget to post your results when Maņana is back together again.
Thanks.
Doug Hoople
M/V Bomar
1963 Stephens Bros. 50 FDMY
Sausalito, CA
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