CB zinc replacement

[CharlieRN]

Bub's thread regarding a CB shackle got me thinking about the zinc on my Sun Cat. I did not want to hijack his thread, so started this instead. Let me also mention that my 2013 Sun Cat is new to me and is the first boat I've owned. That's the diplomatic way of saying: "Sorry for the newbie question."

While I went over the boat as thoroughly as I could before buying, she was on a trailer (an EZ Tilt supplied by ComPac when initially purchased) and I couldn't see a way to check out the centerboard. I did check to see if the pennant would release - it did, and there was some movement in the CB - but as far as I could determine, could not drop down very far because of the design of the trailer.

The Sun Cat is in terrific condition overall but I'm assuming that her zinc(s? - not sure if there's more than one) likely need(s) to be replaced. This is based on nothing more than her age and though pretty lightly used, knowing she spent most of her time in salt water. Is there any way to inspect and if needed, change out the zincs while the boat is on her trailer?

[Tim Gardner]

Technically,  it's a Swabbie question.  As far as checking the zinc, there are knowledgeable folks here that can answer that question.   My vessel has no center board.
TG

[slode]

I don't believe the Sun Cat centerboard has an anode.  My Eclipse doesn't.  The centerboard is stainless, a very noble metal, and there are no dissimilar metals underwater to corrode from galvanic action.  Your outboard would be the only concern and that should have it's own anode.  Also don't use zinc in fresh water.  Aluminum is the better anode material for anything but saltwater.

[bruce]

Until you can eyeball any zincs you might have, a couple of things to think about.

How was your boat used, as you say, lightly. Dry sailed, in the water for a few weeks during vacations, or in the water for months at a time? How will you use the boat? Shorter is better for the zincs, of course. Saltwater is generally worse than fresh for corrosion. As Slode says, stainless fairs well in bi-metalic galvanic corrosion because it is more noble than the dissimilar metals around, mostly aluminum.

So, why would anyone put a zinc on stainless steel? The short answer is because real-world experience shows that they can be useful. Stainless, and other metals, can be severely and rapidly corroded by stray electrical currents, in conditions that might be found at your local marina. If you are experiencing stainless corrosion, a zinc could help protect it.
http://www.boatus.com/boattech/articles/marine-corrosion.asp (see stray current corrosion)

Com-Pac changed the design of the Sun Cat centerboard trunk because of corrosion issues, that they felt were preventable by proper zinc replacement if the owners took the time. I know of one PC at a marina in south FL that had welds fail on their stainless centerboard trunk from corrosion. Com-Pac replaced the trunk, and within months the new bolts were actively corroding. He had zincs on the centerboard, but they were not protecting the trunk adequately. He's taken to mounting additional zincs wherever and however he can, changed every 2 months. In the CB shackle thread, Tom Ray clearly used zincs, and changed them as necessary, on his Sun Cat.

Did you get an outboard with the boat? If so, how are the zincs doing there? How does the rudder look? Most don't have zincs, in my experience, but if the owner had experienced problems, which should be evident, he may have added some.

At least with PCs, not all came with zincs on the centerboard. Mine did, but others expressed surprise when they heard I had them. I did not request them, but Com-Pac knew where the boat was headed, coastal RI, so they may have decided to mount them.

Since the boat appears to be in terrific condition, that's a good sign that maintenance was up to date. Unless the boat was in the water for months at a time, or, more importantly, at a marina you don't know, or was connected to shore power routinely to run electrical equipment on board, I bet, like most of us, you're OK. Worth checking out, of course, and check the pendant while you're there!

[Bilge Rat]

I find the easiest way to check your zincs is to dive under the boat while at anchor.  Put a mask on and all it takes is a about 10 - 15 seconds of holding your breath to swim under the boat and take a look at the zincs on the centerboard. While there you can also inspect the shackle and pendant line. 

[CharlieRN]

Thanks to all for the replies. Much to consider.

Right now, she's covered and on her trailer in the boatyard of the dealer/marina I purchased her from. What I was told by the folks at the yard is that the boat was used mostly for on-the-water vacations and spent much of her life dry sailed.

I may be able to get the yard to use their lift to allow me to check out the center board anodes before I trailer her home. I'm also ashamed to admit that I did not check out the zincs on the outboard, which is in an indoor storage room at the yard. I'll check things more thoroughly before I trailer her home in late March, but the o/b itself looked almost new and the shaft showed little corrosion.

Again thanks to all for the advice and info - very helpful for a newbie boat owner.

[bruce]

Charlie, it's always fun to help someone sort out a new boat. Even the most experienced can have questions.

From you observations of the OB, I doubt you have an issue with corrosion. When you get back to your boat, take lots of photos. Many questions can potentially be answered just from seeing what you are concerned about. Most will probably be routine, and easily addressed, not worth stressing out about. If a more serious issue presents, someone here can probably help.

I look forward to hearing more about your experiences as you learn the boat!

[Bub]

Charlie. Just saw this. I had my nearby marina lift her out and place temporarily on a wash rack with bunks running fore and aft that were offset from the keel. Not the recommended way to trailer the boat because of stress on the Fiberglas hull but it was only sitting static overnight. I had called Gerry Hutchins and ordered two sets of zincs ahead of time and installation was simple even for me whose expertise ends with a set of pliers and a screwdriver. I also found that even tho my boat had been mostly dry sailed over its life that the cb was covered with ugly worm like growths which I had never seen before, and a few oyster shells which are common here. My expertise also extends or sandpaper and paint scrapers so I cleaned up the whole mess.

PLEASE NOTE MY BOAT IS THE 17 ft SUN DAY CAT. I do not know if is identical under the waterline to other Cat models.

[Bub]

Update. Just hauled my SunDay Cat for several reasons and inspected the zincs installed last year. There was no visible sign of deterioration, though I emphasize that she is not stored in the water, never more that 24 hours at a time. I'm just sayin'.

[Maritimer67]

Where about on the Sun Cat CB are the zinc(s) located?  Anyone have a picture they can post?

[ChasRN]

Where about on the Sun Cat CB are the zinc(s) located?  Anyone have a picture they can post?

Here's the illustration from the Sun Cat owners manual. Looks like they are at the distal end/anterior plane of the CB

[bruce]

Here's the zincs on Tom Ray's 2005, slightly different layout.
https://forum.trailersailor.com/post.php?id=1390218