Revelations about zinc electrodes.

Discussion in 'Boat Design' started by CDK, Jan 7, 2011.

  1. Frosty

    Frosty Previous Member

    This is extremely complex, I have bronze thru hulls with st /steel ball valves, acorrding to the book this is no no. I have no trouble from them but I can feel electricity of some sorts when my hands are wet yet the thru hulls are not bonded with wires but are by the seawater within it to the engine.

    Behind me a friend has a wooden boat with copper bottom plate , he has stopped using anodes, they dont erode anymore, he has checked the attachments frequently with a meter yet his anodes donr erode, he is very worried.

    I have no bonding to the batts and even a neg and pos batt swithching so engines are isolated.

    I have halted all engine anode errosion by fresh water flushing the engines after use.
     
  2. CDK
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    CDK retired engineer

    This is of course a very special case. The Faraday cage is a poor one, you don't want the deck cluttered with wires every foot.

    I would bond the mast base to the keels with braided copper straps, shortest route, minimal bends, certainly no sharp angles to avoid any inductance that could cause a voltage drop during a lighting spike.
    If the keels will be coated mild steel, install zinc electrodes to ensure contact with the water, if they are stainless, skip the electrodes: there are no different metals there and your boat doesn't stay in the water long enough to need protection.

    You cannot leave the motors and electronics floating, they may acquire any potential vs ground during nearby lighting. If there will be a metal rudder I would use that as central ground, if not, use one of the keels for that purpose.

    If the prop is bronze on a stainless shaft it gets a small zinc electrode on the prop nut or on the shaft. Paint any surface you have access to.

    rgds,
    Cornelis
     
  3. gonzo
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    gonzo Senior Member

    Lightning protection is a completely different thing. To start the voltage is huge. Also, if the current can jump a mile or more, a small separation in the boat will make little difference. The current on the ground cable will produce a high magnetic field that will make other electrics act like a secondary coil in a transformer. That is why electrics get damaged on lightning strikes even if it gets grounded. The protection may save your life though.
     
  4. Wynand N
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    Wynand N Retired Steelboatbuilder

    and this beg the question...why do one want to get this technical and complicated about anodes.

    Best is to keep it simple on a boat, fit anodes where needed and have a cold frosty and fill the sails with a fair breeze. :cool:
    There is an old saying; "any fool can be complicated but it takes a genius to be simple"
    Having said that, why be so technical and blah, blah about having such fancy stuff/ideas and queries on boats such as Bert's post #89 (niks persoonlik nie my vriend) for a boat that will barely sees water that often?

    There are millions of sail boats over a big spectrum of built materials used out on the big blue pond and mostly all of them are protected by the old trusted anode or zinc without problems and usually when there are some problems, it is a lack of insufficient anodes or foolish placement of these critters. Also, simply stick with proven bonding methods of the electrical circuits in the boat and all should be well.

    KISS (please, not me) ;)
     
  5. CDK
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    CDK retired engineer

    That's why the mast to keel straps must be heavy and straight.
    Against a direct hit nothing helps.
     
  6. michael pierzga
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    michael pierzga Senior Member

    More Voodoo statements CDK. The vessel in the picture recieved a direct hit and only suffered minor light bulb damage.

    For anyone reading CDK's Caravan Park Experimental Marine Science I would recommend they first read the literature disseminated by the Metal Boat Society . This information concerning " best practice" Bonding, Anodes and lightning protection is well presented, logical , easy to understand and is widely adopted by designers, marine surveyors, insurance companies and shipbuilders.

    http://www.kastenmarine.com/_pdf/mbqCref.pdf
     

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  7. BertKu
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    BertKu Senior Member

    Because, I am making a boat with lots of electronics and electric DC motors with electronic controllers.

    It maybe true, but I am not building an sailing boat, but an electric driven boat, although it will have a small emergency sail
    Unfortunately, even if the boat is stored at my home, I have to make provision for the electrical surges. A lightning storm will not move around my problems.

    It is not that simple if one uses electronics. But I love to invite you for a drink or a cup of coffee or whatever and I can only learn from you. I assume you live in Houtbay, Cape Town or in that area. Durban is too far for me.
    Bert
     
  8. gonzo
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    gonzo Senior Member

    Michael: can you skip the snot and clarify what do you mean by "Voodoo statements"?
     
  9. BertKu
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    BertKu Senior Member

    Unfortunately I must agree with CDK. Unless you have a Faraday cage type of protection, nothing helps for a direct hit. South Africa has the second highest ligthning discharges in the world. We sold and made in excess of
    20 million devices for lightning surges, this is apart from all the other companies who did the same. I have been involved in insurance claims and technical issues. Only if the lightning discharge took place via the metal wires to the top of the mast from bow, aft, and sides, (Type of Faraday cage) it would have had a chance not to damage anything inside the cabin.
    Bert
     
    Last edited: Jan 11, 2011
  10. BertKu
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    BertKu Senior Member

    Thank you Michael, a very useful document. However it is not complete. There is no mentioning that a lichtning surge is not one surge but up to 40 bursts. This for electronics is a serious problem. A golden rule is to re-direct the surge and not to clamp or suppress the surge. Therefore I am puzzled about your attack on CDK. Like I have said before, lets not be personal and lets make it a fun website, without attacks. People should just state their opinion and nothing else. If one disagree with somebody else, it can be done in a nice way. But it is indeed a very interesting worthwile document.
    Bert
     
  11. gonzo
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    gonzo Senior Member

    I worked as a surveyor for insurance companies in Florida over two years. That is the lightning capitol of the world. I have seen many strikes where the path is erratic throughout the boat. It is possible to see the burn marks leave the grounding straps and follow the hull surface or some small wiring.
     
  12. viking north
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    viking north VINLAND

    I agree with Bertku, all you guys with the "KNOW" have alot of good info for us guys who need it but there are times, and often, where we have to choose and pick good criteria from all. Many times we hesitate in that we don't want to seem we are taking sides. You are well educated, informative, and experienced but at times we have to get involved in a blood bath to be part of the forum. A good example was the broken glass path i had to walk with bare feet on the, "reverse engineering thread i started". A certain amount of competitiveness is good it produces good info, but when it comes to personal attacks it embarasses us all. Not pointing out anyone, we're probably all a little guilty of this when pushed and I for one apologize if i have unknowingly done so. Just turning the light on for thought, Dont shoot the messinger, Geo.
     
  13. CDK
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    CDK retired engineer

    The usual nonsense from Spain. You really need a shrink!

    My electronics company got a major contract with the Dutch railways to protect automated railway crossings against lightning. These are very difficult objects with long control wires, high voltage lines and metal barriers that stand upright most of the time, acting as antennas. We were able to suppress all esp with spark gaps, delay circuits and Siemens varistors, but in the (rare) case of a direct hit all electronics was obliterated, cables vaporized and even the motor/worm gear exploded. The national railway company decided to replace all metal barriers with polyester ones to further reduce lightning damage.
     
  14. BertKu
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    BertKu Senior Member

    CDK, Michael,
    The problem is, when replies become very personal, people stay away from contributing and expressing their views. This in view that they do not want to be involved in arguments. I like to suggest that you both give each other some private messages and get it off your chest. But I like to see everybody, even the most timid person, to express his or her view. I may be able to learn something or use his/her idee.
    bert
     

  15. michael pierzga
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    michael pierzga Senior Member

    BertKu...when building or operating a boat , your best defense against Galvanic action , lightning damage, electrical faults, dissimilar metals...... is to follow best practice as determined by generations of specialists, boatbuilders, insurance companies and marine surveyors. This is the only way. Raw zinc anodes, mickey mouse anode bonding and non spec grounding systems revealed by CDK will not help and they are a disservice to any builder endeavoring to apply best practise.
    I have been on sailing yachts struck by lighting , I have repaired sailing yachts blasted by lightning. My observation is that if you follow " best Practice" as is outlined in the literature, your boat has the best chance of escaping serious damage.

    Also, I believe you inquired about using SS underwater as a Keel structure. Be wise. SS underwater is problematic. Normally I only see SS underwater when the boat is specialized...like a trailer sailer or when their is no other material more suitable .

    Look at the photo. This yacht is only 4 months old...new . Observe the corrosion. SS. Oxygen depletion at the paint line. the ss in this fitting has changed from Passive to active state and its visable at the paint line. The service life of this fitting will be harsh and the service life of the sacrifical anode system will be shortened. .

    Oh and BertKu, When I was a kid I worked in the shop of the German electrical engineer. .. Mr Edgar Byne. Ed wrote a booklet to educate field technicians, amateur boatbuilders and boat owners concerning general marine electrical systems. This is the link... well worthwhile printing the document to keep handy in your workshop.

    http://www.smer.fi/docut/12volthandbook.pdf
     

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