Adding a hull zinc
Moderator: Jim Walsh
Adding a hull zinc
We have transfered our Cape Dory 33 from the Great Lakes to Puget Sound. Since it has always been a freshwater boat, we are now making the modifications for saltwater. Besides the heat exchanger, we have installed a shaft zinc. The local yard believes that a second zinc, on the keel, should be installed and tied into the Dynaplates ground system and thru-hulls. I know Guest's website states that the Dynaplate is supposed to be a bonding system that helps reduce galvanic corrosion, but the idea of sintered bronze taking the place of a sacrificial metal doesn't make sense. Do Cape Dory's only rely on the Dynaplate and a shaft zinc? Does anyone think that installing a hull zinc on the keel and connecting it to the thru-hulls and bonding system will be a problem? Any thoughts?
Hull zinc's
This is another area that has a lot of strong opinions.
Most boats in salt water do fine with a shaft zinc. In some areas a "Guppy" can be used to supplement the shaft zinc. This is a zinc on a long wire that you connect to a convenient ground when the boat is tied up in a marina. Check and see if your new neighbors use one, or if there is any unusual electrolysis. I personally would use one if there are a bunch of boats that have a "yellow umbilical cord" rigged full time. You just don't know what your neighbors electrical system, or the marinas, is like.
In my own case, I use a hull zinc wired to the boats common ground in addition to the shaft zinc. My shore electrical system also has a ground isolator. In my home port there is one very suspect boat with an owner that is best described as indifferent. A hull zinc about 4x6 inches just makes good insurance and I do check the shaft zinc from time to time, replacing as necessary.
Good luck with your decision. I would give serious consideration to the local advise, they have experience in local conditions.
Most boats in salt water do fine with a shaft zinc. In some areas a "Guppy" can be used to supplement the shaft zinc. This is a zinc on a long wire that you connect to a convenient ground when the boat is tied up in a marina. Check and see if your new neighbors use one, or if there is any unusual electrolysis. I personally would use one if there are a bunch of boats that have a "yellow umbilical cord" rigged full time. You just don't know what your neighbors electrical system, or the marinas, is like.
In my own case, I use a hull zinc wired to the boats common ground in addition to the shaft zinc. My shore electrical system also has a ground isolator. In my home port there is one very suspect boat with an owner that is best described as indifferent. A hull zinc about 4x6 inches just makes good insurance and I do check the shaft zinc from time to time, replacing as necessary.
Good luck with your decision. I would give serious consideration to the local advise, they have experience in local conditions.
Jim Davis
S/V Isa Lei
S/V Isa Lei
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M. R. Bober
- Posts: 1122
- Joined: Feb 6th, '05, 08:59
- Location: CARETAKER CD28 Flybridge Trawler
Remember the Perry nut?
Before you put that zinc on the shaft.....
Cape Dory wasn't fond of the shaft zinc. Something about blocking the water flow to the cutlass bearing (I've been told). What CD was fond of was the Perry nut, a zinc endpiece for the prop shaft. Unfortunately Perry nuts are not available (search this site for more info). Consider something like the Canada Metal's zinc prop nut.
One other thought:
Zincs are sacrifical. Dynaplates are not.
Mitchell Bober
Sunny Annapolis (where you just can't get "fresh water" taffy),MD
http://www.westmarine.com/webapp/wcs/st ... /315/314/4
Cape Dory wasn't fond of the shaft zinc. Something about blocking the water flow to the cutlass bearing (I've been told). What CD was fond of was the Perry nut, a zinc endpiece for the prop shaft. Unfortunately Perry nuts are not available (search this site for more info). Consider something like the Canada Metal's zinc prop nut.
One other thought:
Zincs are sacrifical. Dynaplates are not.
Mitchell Bober
Sunny Annapolis (where you just can't get "fresh water" taffy),MD
http://www.westmarine.com/webapp/wcs/st ... /315/314/4
CDSOA Founding Member