Magic formula? - Forums Archive

Crawfish

2017-05-22 14:31:09

Is there a formula for how much zinc you should have on a glass, wood, steel boat?

What about a ratio for zinc to aluminum anodes?

What do you guy's think?

Once and Future

2017-05-23 01:27:17

I am willing to give my 2 cents, and I am also willing to be corrected by others. My fiberglass boat came from Canada with a lot more zincs than you normally see on Alaskan boats. The Canadian fishermen told me this boat had a good reputation for being fishy. So I stuck with the program that was in place. The boat has keel coolers on both sides made of double or quadruple copper tubing. So, going from memory there are 3 or 4 zincs on the keel coolers on each side, plus 2 zincs on the rudder shoe, plus 4 total zincs on the rudder. I'm talking about the zincs that are about 10" long, 2-1/2" wide and 1-1/2" thick. I forget what they weigh. 5 pounds maybe?

And I will say this, I think too many zincs is better than not enough. They erode quite slowly since I have so many. (That's my take, anyway.) I change a few each year that are getting too small. But I would say they last 2 or 3 years. Added bonus that one year I didn't get good enough contact on 2 of them so they weren't working. And their neighbors seem to have taken up the slack.

My theory is that if I had only one zinc it would erode before the season was over. Plenty of zincs and they all erode more slowly, so other than the investment tied up, it's not like I'm wasting zinc. I think more zincs means less eddy current in my boat metals, and in the water.

I had a young fellow in the boat yard once say that many zincs looked "too hot" to him and he questioned whether it fished well. As I have said before when there are fish around, my boat is not the limiting factor as to how many I catch.

I know a friend told me this winter the price of zinc was up and he heard aluminum could be used as a substitute. I was skeptical, but this link seems to support that: http://performancemetals.com/anodes/AnodeFAQs.shtml It also supports my idea that you can't get too much zinc; on a fiberglass boat anyway.

Crawfish

2017-05-23 16:52:11

I think some guys are using the aluminum anodes for an ion trail because they eat more readily than zinc.

Once and Future do you know what your base hull potential is being heavy on the zinc side?

Once and Future

2017-05-23 18:44:46

At the dock, with one cannonball down a couple fathoms, I have plus 600 milivolts on the wire just above water level, with the negative lead of the voltmeter on the rudder post.

And it looks like those zincs weigh more like 10 pounds when new, not 5.

I wonder why aluminum anodes aren't more available at the local hardware stores near the zincs. Could save some money if they didn't mess up the fishing. But then again, an aluminum anode of the same dimensions, even though a third cheaper, would probably only have half as much mass, and so disappear much sooner.

Crawfish

2017-05-24 16:17:11

Cool.

Thanks for the info.