Lightning protection

Discussion in 'Electrical Systems' started by missinginaction, Sep 8, 2013.

  1. michael pierzga
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    michael pierzga Senior Member

    I keep my second epirb inside the boat. Sun, rain, lightning, physical abuse.....you just never know.

    Im on my third vhf radio and antenea. All blown away by lightning.

    Electronic engine controls are vulnerable.

    Same holds true with your life raft..store inside the boat when you are not on passage.
     
  2. jonr
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    jonr Senior Member

    I suppose when a sailboat is sitting at the dock, it's easy enough to connect a thick copper ground wire to the mast and then drop it over the side. Better than having the lightning punch a hole through the hull. Disconnecting things inside also helps. So do surge protectors (TVS diodes and MOVs).
     
  3. michael pierzga
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    michael pierzga Senior Member

    Ike posted valuable info. If you follow these guidelines you will conform to best practice
     
  4. JSL
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    JSL Senior Member

    Another standard is by ABYC TE-4
    We know that lightning is powerful and 'heavy': like a fast truck, it does not go around corners very well so avoid sharp turns in your grounding wire. If there are 'corners', be prepared for arcing and some damage.
     
  5. tom28571
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    tom28571 Senior Member

    Well, most anything will explode if enough current is forced through it. Dynaplates do conduct very well but no better than a block of copper of the same external dimensions or a hollow copper box of those same dimensions. The granular construction of Dynaplates with acres of internal water contact do not increase their ability to conduct current to the surrounding water and advertising to the contrary is just sales hype.

    This is basic electrical resistance or conductance theory.
     
  6. UNCIVILIZED
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    UNCIVILIZED DIY Junkyard MadScientist

    I gotta' come back & study this stuff later. There's a LOT more good stuff on the topic in here than I'd ever hypothesized existed.
     
  7. urisvan
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    urisvan Senior Member

    alternative?

    i am planning to do it like that: i will make an attachment point on mast and prepare a thick cable with a terminal on one end. when the conditions are bad , i can attach this cable to the mast easily and let the other end go to the water.
    also i can disconnect the VHF and GPS from their antennas
    what do you think about it?

    Regards
    Ulas
     
  8. AndySGray
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    AndySGray Senior Member

    AWG 6 seems a little meagre

    The lightening conductors I've seen on buildings were copper strap 3/16 x 1", the common earth in the UK is a 4' bronze bar hammered into the ground.

    The power is difficult to believe - one of our 100 year old trees took a direct hit and it was anihilated - splintered chunks needing two hands to lift were blown 20-40 feet, it was in a 3 acre field and bits covered at least an acre!
     
  9. Yobarnacle
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    Yobarnacle Senior Member

    Your 100 year old tree was blown apart by super heated steam. Of course the steam was created by the lightning heating the water and sap in the tree.
     
  10. CloudDiver
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    CloudDiver Senior Member

    1 person likes this.
  11. Charlyipad
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    Charlyipad Senior Member

    Guys I heard my first rumble of the season a few days ago. My boat is a new homebuilt catamaran. The bridge deck is open with an aluminum frame to support an awning, other than that not much metal, except the rudder posts and connecting tubes, and the compression tubes forward. The two shrouds and headstay terminate at composite chainplates, about five feet above the water.

    I think I want to run an aluminum cable straight down through the deck at the base of the mast. My thinking is to use heavy aluminum wire with aluminum fasteners connecting it to the aluminum mast step. It seems to me that aluminum would be better, since copper and al don't get along. This cable would not actually go into the drink, just a few inches above, so I could leave it there without worrying about it. I have one of these fuzzy things at the masthead, but no grounding cable running down the stick.

    At the shrouds, what about clamping a ss wire to the shroud ( I really don't like the idea of clamping anything the the shrouds- but what else can you do?) and chucking it overboard if (when) I am underway in a thunderstorm.

    The other stuff is all aluminum except the anchor and chain. (don't know what to do with that)

    but, anyway, the reading I have done everybody always specs heavy copper wire, which to me makes no sense if you are bonding the thing to aluminum. What do you think?

    ps it seems that the aluminum frame for the awning would act as a kind of faraday cage-- I could connect some aluminum wires to the thru bolts where the legs fasten to the deck, and let them hang down in the same fashion as the main grounding wire at the mast. I know all this wire dangling down below the bridge deck would look pretty weird, maybe I could fasten some tethers to the ends and pick them up so they would be up against the bottom of the bridge deck, and let them down in a storm. maybe.

    has anybody else done it that way? I am scared of lightning.
     
  12. JSL
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    JSL Senior Member

    I understand your concern.
    Check out ABYC section TE-4, it should give you a good start if not the total solution: A catamaran may be a bit more complicated than a mono-hull.
    Make sure the ground conductor has a straight route from masthead to the water - lightning takes the shortest path & does not like to change direction. 90 degree bends in the conductor can create arcing points and therefor damage. My guess is, if your grounding cable is dangling clear of the water the 'strike' might arc over to a better conductor such as some metal in the boat...... screws, hinges, boat wiring might be all it needs.
     
  13. Charlyipad
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    Charlyipad Senior Member

    Thanks JSL,

    Ewan Thompson's research indicates that the optimum position for grounding is a few inches above the water. I don't really understand why that is. Anyone have any direct (no pun) experience?

    Thompson sells thru hull connectors that are mounted above the waterline. They look really cool,but I don't think I need them. I have almost zero metal inside my hulls... and so they wouldn't be in the direct path in a strike. My strategy would be to try and route everything in a straight line from the masthead.

    Comments appreciated.
     

  14. Charlyipad
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    Charlyipad Senior Member

    OK this may seem like a silly question but I am going to ask anyway.

    For purposes of a lightning grounding wire, does it matter if it is insulated or not?

    I have an old pair of jumper cables. I cut them into two halves and use them to clip onto the shrouds in a storm. Also I bought a thick aluminum cable with some aluminum lugs and attached that to the mast base, running it straight down through the deck to the water. Both are insulated with plastic sheathing.

    any thoughts appreciated.
     
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