Zinc me before they sink me.

[Scott Galloway]

“Zinc”, “zincs”, and "corrosion” didn’t produce many results in the search feature on this forum, so here is a question or two for you all:

I put a couple of zincs on my soon-to-be re-launched Ariel: one on the rudder shoe and one on the rudder, grounded to the upper rudder shaft. The rudder shoe zinc is just an OB motor zinc. Larger zincs did not seem to fit the flat space available on the shoe.

I noted at open time that some vestigial wires seem to have connected shroud chain plates to something else, but I am not sure to what exactly. A green wire runs to the rusty steel bolt protruding from my ballast. I have been told that is an RF ground for the Loran. Since I have some new thru-hulls with cool little bonding screws in their flanges, I'd like to connect them to something. Anyone have any idea how the metal on these boats (OB Models) were originally protected from corrosion?

And has anyone come up with a really good bonding system for thru-hulls? I had trouble finding an appropriate zinc to bolt to the rudder shoe that was large enough to last between annual haul-outs. Time to get out the snorkel I guess. As far as the rudder-mounted zinc, I did not want to go too heavy there, and that zinc should be fairy easy to replace in the water.

I was also thinking that I could make up removable zinc that could be used when the boat was at the dock. I could connect all the bondable devices on the boat to a wire that ran back to a bolt mounted in the OB well, and hang a zinc there from that bolt that could be removed when it was time to go sailing: Sort of a poor man's version of that $55 zinc fish on stainless steel wire that West Marine sells.

Any thoughts?

[John]

Scott,

Zincs.....and galvanic corrosion require both an electical connection and a conducting medium (salt water) to complete a circuit. Dissimilar metals along with the two previous items form a battery. The use of zincs is to provide a more active (less noble) side for the circuit so that the zinc is consummed rather than your boat part. Zinc is a very active metal, asi is aluminum.

This raises two points. The first is that in order to work, zincs need to be connected electrically (by wire) with the other metal items that sit in the salt water. If it doesn't sit in the water, it doesn't need to be bonded. And zincs not connected to the other items may corrode for other reasons but will not protect your boat.

The second point is more debatable, by some. There is a the thought that to bond (connect) your through hulls to the other metal in your boat is an invitation to disaster. If the zincs are consumed and the through-hulls are now the most active metal in the system, you now have a battery eating up the one thing between you anad the bottom of the harbor. There have also been some reports I have seen saying that galvanic corrosion can cause problems with the surrounding material, especially wood and soften and weaken them. I can't speak with any authority about that but I have heard it from some. So my recommendation is to bond everything but your through hulls.

There are two systems tying things together electrically in your boat. The first is the bonding system as mentioned above. The second is a grounding system tying all metal items above the water to the same electrical point, for lightning protection. Code requirements currently (sorry,,,I couln't resist) are for the main discharge path to be 4 ga copper wire or better and ohter paths to be no less than 6 ga or 20 ga copper strips. This may be the source for wire tying your shrouds and stantions together and might lead to a through hull (argghh).

If you have any questions, drop me an email...Also a shameless plug for the Power Squadron. Their Marine Electronics course (for members) is an excellent resourse for this and other information. Join a local squadron and avail yourself. (I am an ME instructor)

[Scott Galloway]

John,

So since conventional wisdom says to bond all metals except my thru-hulls, and since the only metal in my OB equipped (no inboard) Ariel is the rudder, and I have added zincs to the rudder shoe to protect the shoe and lower shaft and another zinc connected by a copper strip to the upper shaft, so that's it I suppose for bonding. I am stuill perplexed, however by Grocco's seacock installation instructions that say, "connect the sea cock to the vessel bonding system with 14 guage wire and a ring connector. A bonding screw bolt is provided on the sea cock flange for this purpose. Connection to the vessel bonding system must be in accordance with ABYC projects E-1, E-2, and E-9."

Although I do have some wires that must have led to what once was a linghtning grounding system, the wires now lead nowhere, unless of course somewhere there is a connection to my Loran RF ground (The rusted steel eye bolt in the bilge that is screwed into the lead ballast, which is encapsulated in glass, unless somehow the lead ballast is connected to the rudder shoe.

None of my former thru-hulls cockpit or head thru-hulls had attachment points. I have no other thru-hulls, so I better chase down those stray wires.

Can I rule out a connection betweeen by lead ballast and the rudder shoe, at least as built by Pearson?

[Toby]

I bought a used sail from someone in Minneapolis whose Commander was totaled after a lightning strike. His report is instructive...

As for lightning (the class of the first sailboat I owned), It was frightening to see pockmarks all about the hull at every place there was a wave peak when the bolt hit, while the boat was moored in 25' of water on the St. Croix. The areas with the chain plates were especially hard hit as the charge jumped from the plates, thru the glass at the waterline...I could put a key 3" into the delamination at the bow; amidships the scoop out of the hull was the size of a golf ball. The lateral damage from the travel of the bolt from amidship plates to the hull pass throughs and on to the motor mounts was frightening. It is a tribute to the old fashioned construction techniques of Pearson's glass lay-up that she didn't sink. I saw a cored Hunter in a yard hit by the same storm that received $15,000 worth of damage. There they were removing 1'x 2' pieces of glass - with that same golf ball sized scorch mark - that looked like the black aftermath of a grass fire on the resin impregnated interior layer.

[John]

Scott,

I think Toby's post is instructive. The result of a direct hit is going to put holes in things, and with millions of volts, most surfaces on a boat are conductive. All that power is seeking a ground point, wherever it can find it.

My guess, based on Valhalla is that the through-hulls were to serve as ground discharege points. I have left the through hulls connected for this reason. The code requirements are for a minimum of 1 sq ft of surface area (copper plate) for the discharge point. I don't believe that the spongey sintered copper rf grounds are sufficient. Again, I have heard stories that boats have been damaged because they used one of these rf ground plates. The story goes that because they are essentially filled with water, when they discharge a lighning stroke, the water is immediately turned to steam and the plate is blown off the boat. This story is probably apocryphal, but the code requirement is for a plate ground.

I have never seen an corrosion on my rudder post, so I have not worried about that. I don't know if the pins on the shoe penetrate into the keel void. If the zinc on your rudder is not wired to something or connected to the lateral rods in your rudder, then they are just weights. I have not been completely under the cockpit floor so I don't know if the rudder post is connected to the ground system. If it is not, then you do not have a protective system for the rudder. There is not a return connection to ground.

[Scott Galloway]

John,

I did not find any bonding screws on my head-related sea cocks, to which my grounding system could have once been attached. Those sea cocks bore the original paint splatters from the original inside hull spray painting. My cockpit thru-hulls were more recent additions and they did not have bonding screws either. I have no other metal in the water other than a rudder shaft (upper and lower)

I have crawled around quite a bit under my cockpit because I had to deal with some leaks from the lazarette into the cockpit lockers and because I installed Garhauer lifting davit and that required work below the cockpit. I can think of no conceivable way to tie the general grounding system electrically to the rudder shaft beneath the cockpit since the rudder shaft slides through its spiffy water-tight glassed-in tube. It would seem an easy thing to do to attach a grounding plate to the hull below water just aft of the lazarette bulkhead and use that as a grounding plate, but the more I read on this topic, they more I am becoming wary of bonding my currently isolated metal components to what would amount to a giant anode, lightning not withstanding.

My rudder shaft is now well connected to zincs, so it is protected.

There were no zincs on my boat when I hauled it. I have been hauled out three times in the past month under rather bizarre circumstances. August was a nautical version of Bill Murray's Groundhog Day. I am hoping to be back in the water on Tuesday.

I have not previously had the boat out of water, so this has been a process of discovery. I discovered two screws that obviously had zincs at one time. One is on the rudder shoe and the other on the rudder. I sanded the bottom paint off the rudder to access the nuts to tighten the bolts connecting the rudder to its upper and lower shaft. I also stripped the upper and lower sections of the bronze shaft. The zinc screw on the upper portion of the rudder seemed strange until I opened the lower of the two upper shaft bolt inspection holes to tighten that nut. An ingenious copper plate with two holes drilled in it connected the upper bolt to the zinc screw. The photo below shows that device. The zinc screw is visible in the photo. The copper strap spans the inspection hole on the starboard side of the rudder. The zinc screw is simply screwed through the smaller of the two holes in the copper strap and into the body of the teak rudder and must at one time have held a zinc of some sort. I replaced this screw with a bolt that goes completely through the rudder and is used to connect a traditional two-sided "balanced" rudder zinc as pictured in the first post to this thread.

The strap runs forward and then bends 90 degrees at the location of the bolt in the inspection hole. There the bolt is inserted through the larger of the two holes in the copper strap. So, the strap on the bolt end serves as a washer between the nut and the forward wall of the bolt inspection hole.

In line with that old song about them dry bones, the zinc bone is connected to the copper strap bone, the copper strap bone is connected to the lower of the two upper rudder shaft bolt bones, and the lower of the two upper rudder shaft bolt bones is connected to the upper rudder shaft bone, and the upper rudder shaft bone is connected to the tiller head bone. So although them bones may not be dry bones, the zinc protects them all from all things wet and briny.

Since the rudder shoe and the lower shaft are in contact, albeit with a mess of blue grease between them, I assume that the rudder shoe zinc protects them both.

However, these two zincs of mine as pictured in the first photo on this thread are rather small, and my upper rudder shaft does have a pink cast to it in places indicating some past corrosion, so I will have to dive the boat from time to time and replace the zincs as necessary. It would have been tempting to add a larger zinc on the rudder shoe, but the need to fit a zinc in between the bolts limited the size of the zinc. I am interested in knowing if anyone else has added larger zincs in this area, o on teh rudder for that matter.

And by the way, while I was working on my rudder I removed the gudgeon and replaced the bolts holding the gudgeon to the keel. I just slipped new bolts into the holes and attached washers and nuts without a second thought, but now I am wondering if it would have been appropriate to have bedded those bolts somehow.

The holes are rather tight, but if those are merely holes drilled through the hull laminate and/or through any voids, might they not allow water to enter the laminate? I wonder about this because little blue dribbled lines run from the gudgeons downward indicating that water must have drained from them for some time after my third and most recent haul out this month. ( not a lot of water, mind you but water that left the blue residue of what I presume is copper oxide formed from some reaction between the fluid leaking out and the new Trinidad red bottom paint.

The old gudgeon bolts were shot. The nuts twisted off rather than releasing. They were bronze bolts like my new silicon bronze bolts. I saw no evidence of bedding compound on the bolts. Since the holes are very tight, I am not sure how one would effectively bed them anyway. One could, I suppose, drill the holes out to a larger diameter, filed them with epoxy, and then re-drill them. I would like to think that those holes do not permit water to enter the hull laminate, but now I am having doubts about that issue.

Does anyone out there know that answer to this question? It would seem that Pearson would have thought the gudgeon bolt hole arrangement out a bit, especially given the keel void issue discussed on page 40 and following in the Ariel manual. I could not find reference to the gudgeon bolt issue in the Ariel Association manual. Since I have similar blue dribbled lines running from various places on my rudder which wouild naturally absorb water saince it is teak, this concern of mine may be much worry about very little that should be worrisome.