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Re: CAPAC and Hull Potential question

Posted: Fri Sep 02, 2016 8:16 am
by barkleydave
AC leakage while extremely dangerous will not effect your galvanic readings. You must check for stray current when voltmeter etc. Your .1 reading may be due to loss of continuity between anodes and your hull. (Adding the external mag. anode will tell you real quick.

http://www.boatzincs.com/hanging_anode_magnesium.html

dave

Re: CAPAC and Hull Potential question

Posted: Fri Sep 02, 2016 8:19 am
by Tranquilo
Yeah, thats why I'm alarmed by this. I'm not connected to shore power and am far up river in mostly fresh water.

I'll kill the breaker to his boat and check again today.

So my nodes don't have to be eaten to have that reading? It may just be the current?

I have a ton of extra nodes laying around. Does it need to be Magnesium?

Re: CAPAC and Hull Potential question

Posted: Fri Sep 02, 2016 8:52 am
by ericinga
The magnesium anode will corrode faster than the typical aluminum (Sealloy) anodes. You should use the aluminum anodes especially if there is a potential for brackish water.

That said, hanging aluminum anodes over the side will help protect the hull. As Dave said, the magnesium anode would corrode faster and give a quicker indication of a galvanic problem.

Re: CAPAC and Hull Potential question

Posted: Fri Sep 02, 2016 9:15 am
by Tranquilo
Awesome. Just ordered it

Re: CAPAC and Hull Potential question

Posted: Fri Sep 02, 2016 11:38 am
by jralbert
I know this may be stating the obvious but just to make sure: when you hang whatever you use over the side, it has to be connected to the hull. Stainless wire clamped/tied to a cleat or stanchion or rail. Hope it solves your issue.

Re: CAPAC and Hull Potential question

Posted: Fri Sep 02, 2016 4:06 pm
by Rob
Thanks I was wondering if you had to clamp it to the hull, how deep and best spot for it?

Re: CAPAC and Hull Potential question

Posted: Fri Sep 02, 2016 4:08 pm
by barkleydave
Stantion or cleat works fine Best location forward of the rudders about 1ft below waterfline

Re: CAPAC and Hull Potential question

Posted: Fri Sep 02, 2016 4:16 pm
by Rob
Great, Thanks

Re: CAPAC and Hull Potential question

Posted: Tue Sep 06, 2016 8:28 am
by Tranquilo
Should get it today.

I took the boat out and tested it on a beach. Still read the same but inspected the nodes and bottom. Looks the same as last time I saw it.

I'm leaving for Cuba tomorrow so I'll dangle it over and continue the search when I get back next week.

Can I make extras and dangle lead diving weights as extra protection? I have a bunch of stainless cable laying around so I could make a few of those as well if it would help..

Re: CAPAC and Hull Potential question

Posted: Tue Sep 06, 2016 10:12 am
by jralbert
No on the lead. It's got to be appropriate metal on the galvanic scale. Without that scale in front of me I can't recall where lead fits. But it could do more harm and absolutely no good(have a good trip)