Elec. grounding

[tomy]

On a DE can someone tell/show me what we are going to ground in a bonding system.

no zinc on running gear (prop shaft, prop, rudder is fiberglass). There is a brush on prop shaft which appears connected via ground wire.

No room for "acorn" nut on back of shaft do to closeness to ruddar

ALL these questions are do to my amazement when I took out boat for winter and found my "Brand New" prop all eaten up. I will send pics when I can. Some of the people who have seen the prob, claim it's not electrolysis, but a cavitation issue.

This new prop is made out of "Nybril" and was supposed to be a hard metal. It also was very costly! ($4000.00 US Dollars)

I am beside myself and would appreciate any and all comments/help

thanks
Tommy

 

[F/V First Team]

are you on a mooring or a slip?
we had a customer who couldnt keep a zinc on their boat at all, a few weeks and it was gone. when they tore down the dock near the boat they found 3" thick cables dumping electricity into the water. not so good for running gear.

you might look into a kapac unit to put a positive charge around your boat.

make sure your bonding wires are all good on the ends and connections. i hope you dont have the bare strand copper wiring. cant tell you how many boats ive seen with green powder for bonding lines

 

[djmarchand]

You could grind out a pocket on your rudder to create clearance for a Perry nut. You can also dangle a zinc fish off the stern.

David

 

[traditions]

Whats the shaft brush connected to?Is this on your 36WB?I have all thru hulls and boxes connected to the stern zinc.Outside I have shaft zinc,cage zincs,rudder zinc,and one for my lower rudder box.I have alot of zincs,but I can go 6 months and still have some left.Loose wires that go nowhere in the boat that are still hooked up can cause problems.I believe you can use a multi meter to test if your boat is hot.I have heard of it being done,but not sure what the settings are.Cavitation will look like burns on the wheel,usually if they are hot the whole wheel is pink when you haul out.Do you have anyhting in front of the wheel up forward it?.

 

[captainlarry84]

Bonding

First what kind of boat do you have?

Mechanical-Re: Bonding Systems
Bonding is the connecting of all underwater metals, such as thru hulls, rudders, strainer, struts, propellers & shafting to a sacrificial anode, such as zinc. If a break should occur in this bondingsystem, the noble or precious metals on your boat, such as Stainless Steel, Silicon Bronze, Bronze & Nibral (a combination of Aluminum, bronze & nickel) will be exposed to nature without any protection from electrolysis. All boats should have some form of a bonding system.

Electrolysis – The Cures

Bonding Systems
The easier of the two to explain and test is the bonding system. A well bonded vessel will have all major components tied into the system: all underwater gear, motors, fuel tanks steering system, the list can go on and on. Most systems consist of a zinc plate at the transom which is connected to a bonding strap. Off the bonding strap are leads which then go to all items which should be protected. Another great piece to add to the bonding system at the far end is a Dynaplate. The Dynaplate will improve performance of electronics, lightning protection and most of all a solid bond, as the Dynaplate is designed to provide an absolute ground to water connection. Dynaplates are available in sizes ranging from 6†X 2†(copper equivalent area 12 sq. ft.) to 18†X 6†(100 sq. ft.).

The bonding wire used should be insulted with a green color to designate its purpose:
#8 wire is recommended for up to 20 feet
#4 wire is recommended for up to 40 feet
#2 wire for any longer lengths
While, these wire sizes may seem large, and therefore expensive in order to insure a low resistance path it is money well spent.

Once the bonding wire run is in place, it is connected to the running gear. For transducers, a stainless steel water hose clamp around the stem with the bonding wire tucked under works well. When doing this, it is a good idea to lightly tin the exposed end so that it gets a good clean ground to the clamp& transducer stem. The rest of the items usually just require a lug eye end and bolt. For the rudder, because the packing insulates the rudder, it should be taped with a flexible bonding wire attached. Last is the shafts and propellers. Many times because of transmission seals and fluids, the propeller shafts and propellers can become insolated from the system.
This can be a real problem as shaft zincs rarely are capable of protecting that much nobler metal for any extended period of time. A simple way to test the shafting and propeller is with a continuity meter. Just place one lead on the transom zinc and the other on the shaft or propeller. If you get tone then your precious shaft & propeller are protected. If not, you should then purchase a high quality motor brush to ride on the shaft and attach to your bonding system.
Every season during “haul out†it is good to check to entire bonding system for breaks with a continuity meter. It is quick, simple and can save you a fortune should you find a break.
Moving down the line and as an option the Dynaplate should be given careful consideration as it provides absolute water to ground connection.


Transom Zinc:
As mentioned, this should be at the endof the bonding run. The transom zinc is not the end all be all of protection. In order for it to be maintained easily, it is placed on the transom below the water line, putting it high in the water for visual inspection. Sacrificial Anodes (zincs) do their best job when they oppose the noble metal that is being protected. This positioning allows a free flow of material from the anode to the noble metals which affords the best protection. The transom is really the only reasonable spot for this anode. Also keep in mind that when underway the transom zinc is completely out of the water.

Rudder Zincs:
Rudder zincs are always a good place for an anode. They rest nice and low in the water column and the rudder can be drilled so the zinc is in a direct line with your most valuable piece of running gear, your bronze or nibral propeller. In addition, rudder zincs do not erode fast because they taper very nicely on the rudder with little drag.

Shaft Zincs:
Every year we put them on for peace of mind and 99% of the time they do not make it through the season. There are two types of Shaft Zincs. The Collar Zinc which is tapered at both ends, like a football to reduce drag; The Donut zinc, which is just that, and used on vessels with minimal shaft clearance, such as keeled New England Boats.
Both offer protection, but once again not enough alone. As stated earlier, the shafts must be tied into your system. In doing so, it will also lighten the load on the shaft zincs to extend its life.
The main reason why these zincs do not last is due to shaft turbulence and cavational erosion as the shaft spins thru the water at a rapid rate. The amount of drag on these zincs is high. Keeping that in mind, it is also a good idea to mount the shaft zinc at a reasonable distance away from your struts to allow good water flow for lubrication to the strut’s cutlass bearing.

Hanging Fish Anode:
Commonly referred to as a “Guppyâ€, thisis an excellent electrolysis problem indicator and protector for you vessel. The Guppy should be tied directly into your bonding system. When the vessel is on land, the guppy cable lead should be measured so the guppy will be in line with your running gear. The guppy can be checked daily or whenever required. Any spike in its erosion is a sure indicator that something has goneastray! It is quick and easy to install and replace, plus it also lightens the erosion load on the underwater zincs which work solo when not at dockside.

Engine Zincs:
The engines contain a separate body of water that is not protected by the boat’s bonding system. Engine zincs must be very carefully inspected and replaced once they are about 50% eroded. Owner’s manuals give recommended hourly inspections of the motor zincs. It is only a guide under ideal conditions. Each vessel is different, and conditions can change. For peace of mind, I inspect zincs every 50 to 75 hours at a maximum. They are cheap and they protect the life blood of your motor. The eroding of engine zincs is also due to water flow and cavation across is surface. The newer smaller higher turning motors will erode zincs quicker that the larger slower turning motors. When your boat is underway at full cruise, lean over the transom and look at the water volume exiting your exhaust system - you will be amazed at the volume!

Even with a perfect bonding system with all the bells and whistles it can only fight electrical currents off for so long. Your guppy which is the Gremlin Scout for a problem should let you know first. Whether your problem is A.C. or D.C. the results are the same - death to healthy metals. If your bonding system is 100% and you are still losing too much zinc then a meter is required to do the testing. This meter is commonly called a galvanic voltage meter or corrosion control meter.

 

[tomy]

Larry..1st glad to hear about your "good" luck coming through the hurricane. Today, sunday, Ronny and Others comming to look at prop. I will be taking pictures and posting for comments. thanks for your last post on this threat.

 

[captainlarry84]

I hope it was helpful;

Did you ever hear the expression; Rust Never Sleeps..how true is that! The best we can do is get a little rustolium and we then slow the process down on things like wrought iron furniture and house trimmings. The same is true about the mysteries of galvanic corrosion, AKA Electrolysis. In laymans terms, electrolysis is the destruction of metals from electrochemical reactions in a saltwater environment. Once this reaction is in motion, like rust, it never sleeps! Good luck in your hunt for the metal gremlins

 

[BillD]

Larry..1st glad to hear about your "good" luck coming through the hurricane. Today, sunday, Ronny and Others comming to look at prop. I will be taking pictures and posting for comments. thanks for your last post on this threat.

I'm going to help Tomy out by posting a few pictures I took today of his prop.
I met Tomy for the 1st today and a couple of his crew. Very nice people. Tomy has a beautiful Cummins 6CTA 450 powered 36 Wayne Beal.

He does have a prop issue. Here's a few pics.
Please note:
1. the transom zinc photo..the zinc is on it's 2nd season.
2. 30X32 DQX
3. 2600 rated engine, 2.5:1 reduction gear.

 

[BillD]

here's a few more pics

Tomy also stated that the prop nuts have a tendency of "loosening" over the season. Had a diver check the prop.

30X32, 3 inch tip clearance.

 

[captainlarry84]

The propeller is gone that is for sure. Nibral wheels are more prone to electrolysis that straight bronze. You may want to consider a bronze wheel if you cannot fine out what the problem is.
My option is that you need to tie you wheel into the bonding system better. I assume that you are bonded, if not follow the guide lines I layout in the earlier post. Zinc Guppies are great you can hang the guppy directly in line with the propeller. The guppy must then be tied into your bonding system. If you cannot do so then clip the guppy onto the shaft or cuppler this will give you dock side protection. I would also check you 110 dockside and genny to make sure the ground leg is not breached. Your bronze stern tube looks fine which additionally adds to my suspicions that the wheel is not tied in to the system.

I also do not like the galvanic darkness on you propeller shaft. The shaft will need some very careful inspect once the wheel is removed. This future re-enforces the lack of bonded zinc preotection as the SS shaft is reacting to your nibral wheel. Lastly if you installed a donut drive saver with a bonded jumper wire you could pick up an additional 1' on the shaft for a shaft zinc. Just make sure that shaft zinc is not to close to the stern tube to allow water to escape.

 

[traditions]

First off,theres no second season on zincs.When a zinc is hauled out and oxidizes,it will no longer work.You can grind off the oxidation if they arent to far gone.That wheel looks to have both problems.The blade tips look like electrolosis,and the other damage looks like cavitation.It could be from that pizza cutter,think about putting a spoiler in front off the hub of the wheel.I know Travis swears by them,but I consider them junk.I have seen more than 1 person scale them into the woods.Is the transducer close to the keel?,like in line with the wheel,or a strainer.I have seen things ahead off the wheel disturb the water and cause a burn. I would invest in a Godfrey collar shaft zinc,they are priceybut how much are wheels?That rudder is getting chewed up pretty bad also.

 

[F/V First Team]

Yeah, the cavitation on the middle of the hub is worrisome, might be because the cutter is pushed right up onto the face of the hub. Same principal as the bulb on cargo ships, gets the wave pattern to ride better along the length. Maybe sliding it ahead some would take care of things? There is a healthy gap on mine, even so I wouldn't blame it all on that. What are you feeding the shaft tube water with? Could you be introducing air down that channel?

 

[captainlarry84]

I am going with all electrolysis on that wheel. With a 2.5 gear you are turn that wheel very slow. I agree that the cutter should be removed and quality shaft zinc installed. It takes a lot to cavitation burn a nibral wheel. You have plenty of room and water flow to the blades. If it was cavitation you would have heard or felt the rumble for sure. Plus the entire wheel is black which is never good.

 

[Raider Ronnie]

Bill met up with me today and we took a ride on my boat up to Tomy's Yacht club.
I say the cutter is the issue.
What Bill didn't post is the picture of the fiberglass rudder.
Same issue.
This is a sandblasting effect caused by the cutter.
The cutter was added this year when the wheel was changed.
No cutter in the past.

 

[captainlarry84]

The cutter we are on to something. Too much stainless steel near the wheel. I have seen this with stainless steel rudders and not a good bonding system do the same thing.

 

[Raider Ronnie]

The cutter we are on to something. Too much stainless steel near the wheel. I have seen this with stainless steel rudders and not a good bonding system do the same thing.

I didn't take any pictures.
But the fiberglass rudder has this issue, definitely from the outside in, not the inside out, and it's in line from the prop wash.
My opinion, this is like a water jet effect.

 

[BillD]

Bill met up with me today and we took a ride on my boat up to Tomy's Yacht club.
I say the cutter is the issue.
What Bill didn't post is the picture of the fiberglass rudder.
Same issue.
This is a sandblasting effect caused by the cutter.
The cutter was added this year when the wheel was changed.
No cutter in the past.

Had too many pictures to choose from, overlooked the rudder pic.

Here is a picture of the fiberglass rudder wearing on the front L side.

 

[F/V First Team]

At least the nuts aren't on backwards

 

[captainlarry84]

The rudder shows a lot caviation. The jury is still out on this one. Any plans on a metal rudder? With a metal bronze rudder zinc could be added and then the rudder can be tied into the bonding system. Plus metal rudders are much thinner allowing the water to escape. With metal you would have less drag and better water flow. I am sure the glass rudder is fine with less HP, but you have a lot of power pushing a lot of water fast. We did a 35 Bruno with a 440 Yanmar and the rudder took a beating. It was replaced with a bronze rudder. We pick up a knot plus it ended the rudder burning problem. The electrolysis problem is still another issue.

 

[Raider Ronnie]

The rudder shows a lot caviation. The jury is still out on this one. Any plans on a metal rudder? With a metal bronze rudder zinc could be added and then the rudder can be tied into the bonding system. Plus metal rudders are much thinner allowing the water to escape. With metal you would have less drag and better water flow. I am sure the glass rudder is fine with less HP, but you have a lot of power pushing a lot of water fast. We did a 35 Bruno with a 440 Yanmar and the rudder took a beating. It was replaced with a bronze rudder. We pick up a knot plus it ended the rudder burning problem. The electrolysis problem is still another issue.

The rudder was never an issue in the past