The Remote Anode project...
So Back to something we've been hashing over in another thread, the remote anode idea.
To refresh everyones' memory on why this idea has been kicked around; Many of us have done a refinishing job on our keels that involve lots of epoxy, epoxy fairing, and barrier coat paint which results in a keel that is completely encapsulated in epoxy. So why in the name of all things holy would we want to drill a hole through it to install a zinc anode and expose the cast iron to water intrusion? Crazy huh?
So I've asked around... in the forums, other boaters, the chandleries... all I get is blank stares and then the most common response is "go ahead and install a zinc anyway". I don't think many people really get the 'science' behind this problem. Seriously, how can cast iron be susceptible to electrolysis if it is completely sealed in epoxy? Well, the answer is, flatly, it can't. The metal has to be in contact with the electrolyte (salt water) for current to effect it. Someone (with real science to back it up) tell me if I'm wrong.
SO... The only two places on my keel that are not completely coated in thick epoxy; the stainless steel bushing that keel pin rides in and the 1/2" threaded hole into the tail end of the keel where the eye-bolt threads in. I'm not worried about the stainless bushing one bit, nuff said. The eye-bolt is stainless and sealed into the threaded hole with a generous amount of blue loc-tite and was toured down quite firmly. When I painted the barrier coat I made sure I used a tiny craft paint brush to coat up and over the collar of the eye bolt, then I did the same with the bottom paint. Water is not getting in there... period.
Ok, so do I still need a sacrificial anode? Even if my keel is sealed as well as it is there is nothing wrong with having some protection... beside, there is other metal under the water which is worth protecting (like the keel cable!). So it was tossed around that an anode attached to the bottom of the hull but electrically connected the keel by having a wire attached the keel winch would give some degree of protection. This is not a new idea by any means. Read in other forums some discussions about protecting cast iron fixed keels and they give the same advice, attach the wire to one of the keel bolts... and so on and so forth.
The big challenge for me was to find an inexpensive method, but also have a clean and yacht-worthy (is that a word?) method of installing this 'system'. Stainless steel isn't as good of an electrical conductor as regular steel, copper, or even aluminum. There is enough stainless in the form of the keel cable between the sacrificial anode and the keel that I wanted to avoid using any components made of stainless if I could. I also wanted something that would be serviceable, removable, and reversible if necessary.
So I started looking for some type of fitting that I could use that was a thru-hull but I would be able to screw a bolt into it from the bottom of the hull, it had to be bronze, and of course it had to be water tight, LOL! So after a little searching the old inter-webs I came up with this;
This is Garboard Drain Plug From Groco (TH-500), it costs $11 direct from Groco, but there are other online sellers who have them as cheap as $8.50 or so.