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Subject: Re: TWL: Unzincs
From: Jim McCorison (jim@XXX.XXX)
Date: Wed May 01 2002 - 21:31:33 EDT
At 05:45 PM 5/1/2002 -0700, Douglas Hoople wrote:
>When salt water and electrical current interact, the chemical byproduct is
>an alkaline solution which eats the lignins in the wood, leaving behind
>raw cellulose fiber and sodium chloride crystals.
On Maņana there was a shaft zinc and a propeller nut zinc. The shaft log
was exhibiting "white fuzziness" around the fastenings, especially at the
forward end of the shaft lag where the packing gland was fastened. We wound
up removing the packing gland / cutlass bearing assembly, shaving off a
bunch of wood, overboring a couple of the mounting holes, then epoxied in
some white oak plugs and reshaping the end of the shaft log with thickened
epoxy. Another year with the zincs and the end of the shaft log would
probably have required replacement. LQOBU!!! (Large Quantities Of Boat Units)
>You mention that, when the zinc was sized down, "the boat measured out
>fine". Do you remember what you were measuring? Did you actually see a
>lower voltage reading from the reduction in size? Did your zincs
>deteriorate at a different rate?
I'm afraid I don't know the answers to these questions. The previous owner
discovered the problem after about a year of the excessive zincs. He
removed the shaft and prop zincs and treated the affect wood with vinegar
(I think it was vinegar.) The final configuration was a single 4"x6" plate
mounted on the transom. Unfortunately he didn't have any paperwork from the
survey which established that the new configuration was correct. So, after
we're done with the refit we'll recheck the voltages to make sure we're
still within limits.
Jim McCorison
M/V Maņana - 38' DeFever, Hull #2
Seattle, WA
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