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Electrical System Grounding Using Zinc Anodes Above the Waterline
|Author||Topic: Electrical System Grounding Using Zinc Anodes Above the Waterline|
posted 04-30-2007 03:56 AM ET (US)
Has anyone ever added a zinc [anode] to the [electrical system] ground inside the console with any results (on a restored Boston Whaler Guardian 19)? I understand the principals of electrolysis, and that a zinc anode kills the static electricity created by spinning propellers. I plan to ground the helm cable steering unit inside the console.
When charing the battery will this zinc absorb any static inside and around the console instead diverting to the engine zinc?
Right now I don't know if the engine will tilt completely out of the water. When moored in a area many boats nearby are using shore power, inverters, and battery chargers. Do you think this extra zinc would help reduce electrolysis? Thanks, mk
posted 04-30-2007 07:53 AM ET (US)
In my marina, if you have any metal touching the water such as the outboard or the outdrive, odds are your zincs will be down to nothing by season's end. That's a good thing obviously, because the sacrificial zinc is taking the brunt of the electrolysis and not the mechanical casings, trim tabs, and the such.
I don't know why you would be concerned about static buildup on your boat. Generally speaking that is not a problem in high humidity areas. Are you attempting a basic lightning bonding system?
posted 04-30-2007 12:31 PM ET (US)
Bella, hey man, of course I am concerned with static build up regardless where I am moored. Your Marina has great rules but I dont want to depend on my neighbor following them in a Marina that moors 500 boats in a mud puddle during NW prime time.
I'm poised to invest around $18,000 for engines that rely on electronic modules and electronic fuel pumps, and do not have radiators that accept coolants with non corrosive chemicals added.
I wonder if extra zincs might extend the battery life as well. While a car has a metal frame in addition to the negative side of the battery, a glass boat only has the engine and battery to disperse the ground (static). Will adding a zinc or two in a convieniant place in addition to the transom area become an asset to accomplish this?
posted 04-30-2007 01:48 PM ET (US)
The reason I asked about the lightning protection is I just finished installing a complete bonding and grounding system in my 23 Conquest. I did a lot of research on the subject of lighting and concluded that nothing is foolproof, but one can take reasonable steps to minimize the effects of static buildup and even a direct hit if the system is properly installed.
I will be happy to post pictures and an explanation of the work I did if this is of interest to you.
posted 04-30-2007 03:02 PM ET (US)
Thanks, I think I can get by...ohh, you know as soon as I say that, lightning will come outa nowhere and strike me down.
Well, if anybody looks inside my console and wants to know what the hell a zinc is doing in there, I will tell em YOU told me it will help ground lighning.
I agree, more grounding cant hurt, so as long as Im at it, why not?
posted 04-30-2007 05:09 PM ET (US)
I'm not too sure about that static thing...
Zincs protect your boat by being a less-noble metal than the outdrive/lower unit/propellers, thus sacrificing themselves to galvanic corrosion.
They don't ground or dissapate anything.
posted 04-30-2007 05:33 PM ET (US)
Anodes need to be in the water to work. I don't think placing one in your console will do anything other than offer an alternative option for downrigger weights when needed in a pinch.
posted 04-30-2007 06:21 PM ET (US)
Bella, I would be very interested in seeing the lightning protection system on your boat.
posted 05-01-2007 12:09 AM ET (US)
I decided to install an lightning ground system in my 23 Conquest after examining the original Boston Whaler bonding system. I have been caught in several storms in the last couple of years and in fact rescued the very boat that I now own during a very heavy nighttime summer squall. I don't know why I was driven to do such a stupid request but it was an adrenaline rush to say the least. The outcome was three friends on board safely towed back to port and a PBA card in my pocket as one of them was a cop.
I don't mind being caught in such storms knowing the odds are very much in my favor of not experiencing a direct hit. On the other side I am a licensed electrical contractor and ICC electrical inspector. I have read many books over the years on the electrical characteristics of lightning and know to expect the unexpected.
What are the Chances of
Lightning Striking Your Boat?
The following statistics are based on all of the BoatUS Marine Insurance claims for lightning damage over a five-year period. The percentages suggest the chances of the various types of boats being struck in any given year.
Auxiliary Sail .6% Six out of 1000
Multi-hull sail .5% Five out of 1000
Trawlers .3% Three out of 1000
Sail Only .2% Two out of 1000
Cruisers .1% One out of 1000
Runabouts .02% Two out of 10,000
Source: BoatUS Marine Insurance Claim Files
The lightning grounding system should be isolated from the DC electrical system if you are in the habit of plugging into shore power for any length of time. The problem with plugging in to shore power with a ground plate is that any stray currents in the marina will work on any metal your boat may have in the water.
Another fact is that we are working in very tight quarters with our boats. If our boats were to take a hit from lightning, we have to understand that we are dealing with tremendous amounts of voltage, currents, and temperatures. Because of this we can not expect to safely protect our electronics, including our sophisticated outboard motor controls. My concern is life safety. If I can live though a direct hit, I can deal with getting my crew back to shore alive.
posted 05-01-2007 12:25 AM ET (US)
"Anodes need to be in the water to work."
Thx Dave, that is what I was looking for. I didn't know for sure.
My reasoning: the anodes on the transom and engine would be submerged. These and the dry console zinc would all be connected to the [electrical ground system]. With that, you are saying the dry zinc is frivolous? Seems to me the console zinc, wet or dry would just make the the transom zincs bigger. My Tug and Barges have zincs welded to the hull everywhere there is turbulance and they are all grounded together via metal hulls, but...wet. so placing another zinc above the waterline is useless. Ok.
posted 05-01-2007 01:24 AM ET (US)
Bella, that is a very clean and tidy looking install, I am jealous. One question, do your components, materials, and install techniques all pretty much follow the 780?
posted 05-01-2007 08:06 AM ET (US)
bigjohn - The installation of my system coincides with the NFPA 780, National Standard for the Installation
of Lightning Protection Systems code as it relates to wire bending radius, materials, and connections. I do have a couple of spots that I will be watching.
One is the connections to the ground plate through the hull. I expect I will see some corrosion in time due to the fact that water will lie in the well. I may just go ahead and fill that area with something to avoid that situation.
The other area will be the dissimilar metal connections of copper to aluminum on the hard top. I expect that the salt water environment will turn these connections green in time. My answer to that will be to change the copper to a gauge or two larger aluminum.
Hopefully I will never have to report on how well it performed!
posted 05-01-2007 09:19 AM ET (US)
Here-here, I agree let's hope you never have to report on it's performance. I do not have as strong of an electrical background as you but I do have a basic electrical background and do troubleshoot, test, and maintain lightning protection systems for overseas military facilities. I refer to the NFPA 780 for perhaps 80% of the requirements for these functions.
This topic is of great interest to me like many boaters so I enjoy talking about it and exchanging ideas for safety sake. I do have some misgivings about the use of any VHF radio antenna as an air terminal. As you know, much of the so-called "data" on potential LPS systems (for boats especially) is theoretical. I guess my misgiving about this is the fact that a 30-40Ka lightning bolt will likely vaporize the antenna itself upon being struck. I reason this will, in all likelihood impede the path of the strike down to your ground plate.
I'm not sure if you have ever seen the "Sande Report" where hundreds of mini rockets were fired up into thunderstorms to trigger lightning strikes. The data gathered from this project served to set the standard so-to-speak for much of the NFPA 780. It was a contracted project by the U.S. Military in either Nevado or Arizona to ensure they designed the best possible protection system for explosives and ordnance storage facilites. I am at home right now without the 780 in front of me but if my memory is correct, 1/2" is the minimum diameter for air terminal (lightning) rods to begin the proper path to ground.
I guess since a typical VHF antenna is nowhere near 1/2" in diameter, I would question its viability is a lightning rod/air terminal. I am not trying to question your expertise at all. I am all for generating more dialogue and in the process, maybe I can learn along with the group.
posted 05-01-2007 09:49 AM ET (US)
I agree with you whole heartedly in referance to the VHF antenna. It is not my intention to use the antenna as any part of the lightning protection system. The only reason I have the PolyPhaser on the lead-in wire is to hopefully keep my radio from frying.
In the event of a thunderstorm the first order of business would be to lay the antennna down on the hardtop. I am a little torn between letting the outrigger holders bear the brunt or installing and pointing the (collapsed) aluminum outriggers in the up position.
My thought is that the higher my air terminal is from the waterline the more I may be inviting a strike. Some "experts" in the field suggest less is better for that reason. Others suggest that if your in a situation as a possible target, make sure your covered.
posted 05-01-2007 02:10 PM ET (US)
Zinc anodes have a more negative electrochemical potential than most other metals. This electrochemical potential difference is not very large, perhaps on the order of a few microvolts. Just enough to attract oxidation ions away from the surrounding area. Their ability to sink or kill static electricity is in my opinion a myth. At best, zinc anodes can only draw a very miniscule amount of current from the static electricity that developes because of the electrochemical difference of potential between themselves and the surrounding environment.
With respect to the great potential difference required for lightning to occur (many millions of volts), I don't think any zinc anode will help direct lightning current away from where it intends to travel. The best outcome one could hope for would be that the use of or presence of zinc anodes would help in keeping your grounding plate from developing corrosion at its wire connection point.
posted 05-01-2007 05:43 PM ET (US)
OK Bella, so if I understand correctly, you're "bonded" properly to keep all metal at same potential but without a means of directing a potential strike to ground. The idea behind no air terminal is to not invite a strike.
posted 05-01-2007 07:22 PM ET (US)
BigJ - Articles I have read pertaining to boats of my configuration suggests that the framework on the hardtop creates a cage if you will around the occupants. I would expect the outrigger holders which stand about a foot above the highest point of the boat would get it. If not, then the frame holding the hardtop would be the terminal.
The more I write this explanation the more I am convincing myself that air terminals should be the outriggers locked into a skyward direction. Bad enough that if everything works as planned, I will probably be deaf. I don't need to get that close to the heat as well.
Thanks for helping me think this thing though. If you see anything else, please feel free.
posted 05-01-2007 09:29 PM ET (US)
Well, one thing comes to mind. An old boating tradition in some areas seems to be keeping a set up jumper cables abord in the event of a thunderstorm. I am told the thought process goes something like....if a seriously bad storm pops up and you have no way out, hook the jumper cables to the outriggers (one jumper cable clamped to each outrigger) then toss the other end into the water.
What is worse than doing this is the fact that a person would actually think this could protect you. As you know, a strike entering the outrigger would travel down to that clamp and pop it right off the outrigger and then there goes your path to ground. Where the electricity goes from there is nothing short of frightening!
I gave up on my quest to build a viable system for my 170 Montauk. I know it is possible but given its small size and open skiff characteristics, the system would look ugly. Instead, I bought a high quality handheld lightning strike detector to avoid the problem. I have used it on my boat one summer season now and am quite pleased with the performance and accuracy. Consumer reports says even the quality handheld units are no more than about 75% accurate but I figure that is much better than nothing.
We also use these same units at work [as a backup weather monitor only] during shipboard ammunition loading here in Guam. Again, I have found them to be very accurate. Here is a link and note I have zero affiliation with this product or company.
posted 05-01-2007 10:00 PM ET (US)
I have one of the original SkyScan models. I bought it because I was coaching traveling soccer. I attempted to use it on my last boat with little success. It would give false indications every time anything electrical was switched on or off. I understand your model has filtered a lot of these "false hits" out.
I'm definitely with you on this one. Momma always said "An ounce of prevention is worth a pound of cure"
posted 05-02-2007 12:56 AM ET (US)
For sure this model I now have (Spectrum Thunderbolt) is better than many previous versions. Even though, onboard electronics can still be a problem with triggering false alarms. I have been able to all but avoid these false alarms by simply running a background noise test AFTER my VHF and chartplotter have been turned on. The noise test takes 15 minutes and just incoportes any interference caused by the electronics into the baseline background magnetic field. I can track multiple storms from 50 miles away and monitor their position and movement relative to my position.
If I were in a bass boat going 65mph down the lake, I would not trust the unit as much since you would naturally being going into and out of additional magnetic fields very quickly. Since my normaly boat useage is ocean trolling at 8-10knots though, I feel this contributes greatly to the unit's overall accuracy. Although it is pricey at $450.00, I feel it is one of the best safety additions to a boat in the summertime when lightning is prevelent.
posted 05-02-2007 08:17 AM ET (US)
Only metals which are in direct contact with the electrolyte (the sea water) can participate in any reaction with the electrolyte (sea water). Adding a zinc anode in an area which is not submerged is of no value. A dry zinc in air can only react with the air and the other metal to which it is connected. It cannot react with the sea water.
A zinc anode does not kill static electricity from a propeller. On larger ships it is common to have a grounding contact on the propeller shaft to bleed off static electricity. The shaft is isolated from the hull by the non-conductive seals of the propeller shaft gland and flexible shaft couplings. The grounding contact insures that the propeller shaft is at the same potential as the rest of the hull, and it prevents the accumulation of any charge on the shaft. This is generally not a problem on an outboard motor. The propeller shaft is not insulated by a rubber coupling, so it is at the same potential as the rest of the motor. The shaft is directly connected to the engine block by the metallic components of the drive train.
The purpose of a zinc anode is to become a sacrificial electrode in the galvanic system which results whenever there are two dissimilar metals in contact with an electrolyte (sea water). The zinc is more reactive (or less noble) than the other metals (typically aluminum, steel, and stainless steel), and is eroded before the other metals enter into the reaction.
I do not think a zinc metal surface inside a fiberglass boat which is not in anyway submerged can have any value as part of the vessel's electrical grounding system.
posted 05-02-2007 12:19 PM ET (US)
Thx all, always something to learn here.
I googgled "electrolosis" and found this brief basic primer that also covered lightning.
posted 05-02-2007 09:44 PM ET (US)
You might find that spelling electrolysis correctly will yield more results form GOOGLE.
posted 05-02-2007 10:33 PM ET (US)
Thank YOU Towboater for letting me use your thread to air my latest project. May I say growing up on the water I've often envy the job of a Tow Boat Captain (until I see them operating in the dead of the winter that is.)
posted 05-02-2007 10:54 PM ET (US)
Or "from" as it were...
posted 05-03-2007 03:03 AM ET (US)
HEY JIM, at least I spelled google right!
thx again for all your help with this & my other spontaneous caffien induced diatribes.
Bella, thank you! There are good and bad hijacks...yours was a good one. IMO, any Skipper that thinks he knows everything or isnt willing to learn is a cull.
I have two schools of thought regarding winter Towboating.
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