What size / shape zinc for keel? Inspection suggestions?

CaptDon01 · Feb 16, 2016

I would suggest pulling the boat and doing an inspection on land. That way you can personally inspect the condition of the keel, keel pin hole, keel cable, and the keel hanger assembly. Being 43 years old, I would want to see everything so I know the condition of everything. Probably fine, but there might be an issue that's easily fixed while out of the water and avoid a serious issue down the road. If you don't know when the lifting cable was replaced, it's probably past due. In my opinion, swing keel boats left in the water require greater keel maintenance and inspection. Do it right and enjoy the next sailing season with a greater peace of mind.

Don

CloudDiver · Feb 16, 2016

Don beat me to it... on a swing keel you really need to pull the boat out. Swing keel refurbishment is a topic we have discussed in the forum several times. Many members, myself included, have posted details and pics about removing the keel and cleaning/sanding/grinding (which is usually best accomplished by sand-blasting) followed by epoxy coating, fairing, barrier coating, and finally bottom paint. During this process we will inspect and possibly replace the keel hangers, keel hanger bolts, keel pin, lifting eye, and keel cable.
If a refurbishment is done correctly encasing the keel in epoxy a zinc shouldn't be required since the cast iron is completed isolated from the water. No salt water = no electrolyte = no galvanic corrosion. I have a prototype remote zinc anode installed on my boat which has yet to be splashed. An old school and low tech solution is to attach an anode to a wire and dunk it over the side, the bitter end attached the keel winch. The winch is electrically connected to the keel via the keel cable, so this can provide some degree of protection while moored or tied pier-side.

fstbttms · Feb 16, 2016

Don't bother. A hunk of metal the size of your keel isn't going to be adequately protected by any anode you'd consider installing anyway.

allen-deckard · Feb 17, 2016

I didn't have a zinc on my boat first couple years MASSIVE issues with corrosion. Third year installed zinc reduced corrosion 90% I'm a HUGH fan of zinc and no conversation would change my mind the difference was night and day for myself.
Like to add a new keel is 2000 a zinc is 30 bucks every couple years. I've also known people that hadn't changed the oil in there car for years and it's still running. Then there are people like me that miss it by 5 miles and the engine blows so maybe I just have bad luck but I do anything and everything I can to prevent future failure.

Now as far as a zinc. I've used a few different methods. In the past I've used a large block one that mounted to the keel kind of a pain. Last time I used from catalina direct the circular ones and tapped out the keel and mounted it there. Works great but only for one season then your taps are ruined.

This season I bought from west marine the big one they sell that looks like a grouper with a wire out it's mouth and a large alligator clamp on the other end. Like above clamped it to the winch handle and throw it over the side pull it when you sail easy to see when it's gone that's this years so don't know if it will work as good or not.

Like to add I am also a giant fan of fiber glassing your keel I think it's a must do project if it's not been done yet but all it takes is a pin hole in your fiberglass to allow corrosion to get a start and thus why I like the zinc.

fstbttms · Feb 17, 2016

allen-deckard said:
Like above clamped it to the winch handle and throw it over the side pull it when you sail easy to see when it's gone...

No offense, but if you believe that attaching an anode to a winch handle is providing protection to anything at all, I have to wonder just how much you understand the causes of marine corrosion and how to control it.

CloudDiver · Feb 17, 2016

fstbttms said:
No offense, but if you believe that attaching an anode to a winch handle is providing protection to anything at all, I have to wonder just how much you understand the causes of marine corrosion and how to control it.

He was talking about the keel winch handle, which electrically connects to the keel via the keel cable... We know stainless isn't the best conductor, but it is better than nothing (we think).

fstbttms · Feb 17, 2016

CloudDiver said:
He was talking about the keel winch handle, which electrically connects to the keel via the keel cable... We know stainless isn't the best conductor, but it is better than nothing (we think).

Not much better, probably. The length of the electrical path between anode and item being protected is important. In the scenario you are talking about, that path is easily 10' or more and highly resistant. Further, I have never come across an iron keel that suffered from galvanic or electrolytic corrosion, which is what zincs anodes provide protection against. Iron will rust however, but anodes will not prevent this.

CloudDiver · Feb 17, 2016

fstbttms said:
Not much better, probably. The length of the electrical path between anode and item being protected is important. In the scenario you are talking about, that path is easily 10' or more and highly resistant. Further, I have never come across an iron keel that suffered from galvanic or electrolytic corrosion, which is what zincs anodes provide protection against. Iron will rust however, but anodes will not prevent this.

You are completely correct... Sometimes you just won't win an argument with science vs. sailors looking for peace of mind. In the case of the anode over the side, this is just the cheapest/easiest method, so if the peace of mind is worth the $50 for the anode/wire/clamp then no harm no foul right?

fstbttms · Feb 17, 2016

CloudDiver said:
You are completely correct... Sometimes you just won't win an argument with science vs. sailors looking for peace of mind. In the case of the anode over the side, this is just the cheapest/easiest method, so if the peace of mind is worth the $50 for the anode/wire/clamp then no harm no foul right?

If it doesn't actually provide protection, then the "peace of mind" is really just wishful thinking.

CloudDiver · Feb 17, 2016

fstbttms said:
If it doesn't actually provide protection, then the "peace of mind" is really just wishful thinking.

My point exactly, but sometimes you just can't convince people otherwise. We have a Marina here in San Diego, fairly new in Chula Vista; I've been there twice and its a nicely built and planned facility. I've been told by several people that there is a really bad stray current problem there and no one has isolated the cause. Some anodes have been required to be changed every 90 days. If I was tied up there with my swing keel I'd have the anode over the side... just in case.

CaptDon01 · Feb 17, 2016

CloudDiver said:
My point exactly, but sometimes you just can't convince people otherwise. We have a Marina here in San Diego, fairly new in Chula Vista; I've been there twice and its a nicely built and planned facility. I've been told by several people that there is a really bad stray current problem there and no one has isolated the cause. Some anodes have been required to be changed every 90 days. If I was tied up there with my swing keel I'd have the anode over the side... just in case.

Luke, my friend would slip his C-22 swing keel boat there and the zinc would be gone in 30 days,(California Yachts Docks). I never had any issues there, but then, my boat has a lead wing keel.

Hey, talking about keels, how is Mike's keel coming along?

Don

JamesG161 · Feb 17, 2016

A drop zinc connected to your keel that is electrically connected will offer some short term protection.

Corrosion rate is a function of surface areas of metals exposed to the water (keel and zinc) and submerged distance from the zinc to the keel.

A minor effect is the connection between zinc and keel resistance to galvanic current flow.

@fstbttms has his points, but several drop zincs near the keel would sure slow down the keel corrosion if you are SURE the cable is electrically connected to keel
Jim...

allen-deckard · Feb 17, 2016

a lot more technical than needed but reading threw this page to the end explains why it works.

https://sites.google.com/site/inter...eactivity-series/3---rust-and-rust-protection

CloudDiver · Feb 17, 2016

CaptDon01 said:
Luke, my friend would slip his C-22 swing keel boat there and the zinc would be gone in 30 days,(California Yachts Docks). I never had any issues there, but then, my boat has a lead wing keel.

Hey, talking about keels, how is Mike's keel coming along?

Don

He's progressing nicely... I let him borrow my boat stands, cherry picker, and rolling atv lift along with wood pallet keel cradle so he could get his boat off the trailer and then pull the keel. He sent me a pic via text, as of two weekends ago he had gotten it sandblasted and then had the first coats of epoxy on, then did follow on coats of filler last weekend. He should be done pretty soon.

Jacktar · Feb 17, 2016

The key reason for a keel zinc is to protect the different metals involved in the bronze hanger to stainless pin to cast iron swing keel, usually pretty much electrically connected. Simple to drill hole through completed coating on keel including bottom paint (mine is copper based, another metal involved.) tap and die and bolt on a teardrop zinc. see pix

CaptDon01 · Feb 17, 2016

Jacktar.......just between you and me, your keel hangers are installed upside down....the round portion goes up into the recess in the hull.

Don

CapnGrumpyBreeches · Feb 17, 2016

I was advised by my "sailing marina guy" to not use Keel Zincs on cast iron as the hole that I drilled exposed more metal then its worth. Epoxy coating the whole thing and "keeping up on it." was advised. I had already installed the zincs by this point and to be honest, The zincs were completely gone after 2 months in the water. Also it seemed like I didnt have enough as the darn keel rusted significantly in that 2 month period. perhaps the salinity is high in my area, but at that rate Id have to spend $30 or more every month or 2 to maintain the keel. So I think Ive given up on zincs on my 22. I went ahead an refurbished the keel with about a billion layers of epoxy coating. (Sandblasted of course) Fingers Crossed for 2016.

What size / shape zinc for keel? Inspection suggestions?

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SBO Weather and Forecasting Forum Jim & John

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