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Thread: Lightning protection for a wooden boat with dyneema standing rigging

  1. #71
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    Default Re: Lightning protection for a wooden boat with dyneema standing rigging

    Hi MN Dave,

    Politely disagreeing with the statement of the strength of a lightening strike in the air vs ground. Kirchhoff's current law tells me the lightening strike current is the same entering the structure as leaving it. Sure, it's not exactly the same due to some losses, but I would consider those negligible.

    Cheers,
    Mark

  2. #72
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    Default Re: Lightning protection for a wooden boat with dyneema standing rigging

    Quote Originally Posted by Mark0 View Post
    Hi MN Dave,

    Politely disagreeing with the statement of the strength of a lightening strike in the air vs ground. Kirchhoff's current law tells me the lightening strike current is the same entering the structure as leaving it. Sure, it's not exactly the same due to some losses, but I would consider those negligible.

    Cheers,
    Mark
    I agree that it does sound counterintuitive.

    That may be the case if the aircraft is under the cloud and a cloud to ground strike passes through it. In the air, that is apparently not the usual situation.

    https://ntrs.nasa.gov/archive/nasa/c...9780003081.pdf
    NASA Reference Publication 1008
    Lightning Protection of Aircraft
    Page 39
    When the aircraft is attached to the leader, some charge (free electrons) will flow onto the aircraft, but the amount of charge which can be taken on is limited by the aircraft size. The measure of the aircraft's ability to store charge is its capacitance.
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

  3. #73
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    Default Re: Lightning protection for a wooden boat with dyneema standing rigging

    Isn't that referring to the the leader ? but the high current return stroke does flow through the aircraft as per page 41, figure 24a.

    Too bad we can't use the leaders to charge batteries before the return stroke

  4. #74
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    Default Re: Lightning protection for a wooden boat with dyneema standing rigging

    I dunno what your all worried about.

    https://www.youtube.com/watch?v=szOnAUnuMLk[/VIDEO]

    Skip to about 47 seconds

  5. #75
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    Default Re: Lightning protection for a wooden boat with dyneema standing rigging

    I've been closer then that to a strike on a tree, not more than 40'. It gives you the heebie jeebies.

  6. #76
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    Default Re: Lightning protection for a wooden boat with dyneema standing rigging

    Quote Originally Posted by Mark0 View Post
    Hi MN Dave,

    Politely disagreeing with the statement of the strength of a lightening strike in the air vs ground. Kirchhoff's current law tells me the lightening strike current is the same entering the structure as leaving it. Sure, it's not exactly the same due to some losses, but I would consider those negligible.

    Cheers,
    Mark
    If you're dealing with 10,000 or 100,000 V it isn't going to matter on your boat. You will either live or die.

  7. #77
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    Default Re: Lightning protection for a wooden boat with dyneema standing rigging

    The following information detailing the mechanics of lightning ground systems is extracted from an article in WoodenBoat magazine No. 136, May/June 1997, and referenced in an article about lightning damage by Jonathan Klopman and Joshua Moore in WB No. 215, July/August 2010.
    https://www.woodenboat.com/lightning-ground-systems

    Quote Originally Posted by navydog View Post
    If you're dealing with 10,000 or 100,000 V it isn't going to matter on your boat. You will either live or die.
    100,000V smarts, but the voltage of lightning can reach 1,000,000,000V and the temperature runs up to 50,000F. So while you might have guessed a little low, you got the end result right.

    Edit -useless trivia- I saw a half-melted elecronic part on the counter at a junkyard. When asked, they said it came from their 2 way radio. The antenna ran up a tree and the cable was buried between the tree and building. The lightning hit the antenna, the cable exploded, dug a trench across the yard and blew up the radio.
    Last edited by MN Dave; 07-22-2018 at 12:20 PM.
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

  8. #78
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    Default Re: Lightning protection for a wooden boat with dyneema standing rigging

    Quote Originally Posted by Geftb View Post
    I dunno what your all worried about.

    https://www.youtube.com/watch?v=szOnAUnuMLk[/VIDEO]

    Skip to about 47 seconds
    They speak French but cuss in English!!

  9. #79
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    Default Re: Lightning protection for a wooden boat with dyneema standing rigging

    Quote Originally Posted by Dave Hadfield View Post

    Of course, the real danger from a t-storm is not the lightning.
    I'm sure everyone heard the about the a Duck Boat tragedy.

    The National Weather Service said wind gusts were as strong as 60 mph and caused 3-foot waves. Strong thunderstorms with straight-line winds.

  10. #80
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    Default Re: Lightning protection for a wooden boat with dyneema standing rigging

    Quote Originally Posted by navydog View Post
    I'm sure everyone heard the about the a Duck Boat tragedy.

    The National Weather Service said wind gusts were as strong as 60 mph and caused 3-foot waves. Strong thunderstorms with straight-line winds.
    Dyneema rigging do you think?

  11. #81
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    Default Re: Lightning protection for a wooden boat with dyneema standing rigging

    Quote Originally Posted by Phil Y View Post
    Dyneema rigging do you think?
    Pretty flippant about the death of 17 people.

  12. #82
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    Default Re: Lightning protection for a wooden boat with dyneema standing rigging

    We had a similar duck boat incident here in Ottawa. 4 people were killed as the vehicle sunk beside our boat on a mooring. It was a difficult time and it still frustrates me 16 years later.

  13. #83
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    Default Re: Lightning protection for a wooden boat with dyneema standing rigging

    Anyway, back to the question: Since dyneema is not a great conductor, down the mast and out through a near-by keel bolt, good conductor to a ground plate of at least a square foot. A conductor inside a hollow mast is probably safe. A conductor made of uninsulated braided copper is best but on many larger boats the mast track is fine. The conductor is more like a suggestion and much of the current is actually traveling through the air alongside the conductor. It's quick enough that it won't burn your sails.

    You'll want very positive provision to unplug all electricals on the mast - lights, radio, whatever. I like mast wires coming out of the mast just under the partners, plugs right there, and enough slack in wires running to the plugs that those wires can be folded back giving a couple of feet gap. Even so, the field around a lightning strike can toast sensitive circuits.

  14. #84
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    Default Re: Lightning protection for a wooden boat with dyneema standing rigging

    In my youth I watched a large sailboat take a direct strike at the masthead, the masthead exploded. Very good discussion.

  15. #85
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    Default

    Quote Originally Posted by navydog View Post
    Pretty flippant about the death of 17 people.


    Yeah I can be a bit like that.


    Sent from my iPhone using Tapatalk

  16. #86
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    Default Re: Lightning protection for a wooden boat with dyneema standing rigging

    Quote Originally Posted by Ian McColgin View Post
    Anyway, back to the question: Since dyneema is not a great conductor, down the mast and out through a near-by keel bolt, good conductor to a ground plate of at least a square foot. A conductor inside a hollow mast is probably safe. A conductor made of uninsulated braided copper is best but on many larger boats the mast track is fine. The conductor is more like a suggestion and much of the current is actually traveling through the air alongside the conductor. It's quick enough that it won't burn your sails.

    You'll want very positive provision to unplug all electricals on the mast - lights, radio, whatever. I like mast wires coming out of the mast just under the partners, plugs right there, and enough slack in wires running to the plugs that those wires can be folded back giving a couple of feet gap. Even so, the field around a lightning strike can toast sensitive circuits.
    So you would think, changing from SS standing rigging to dyneema is OK when having a mast internal, massive and well grounded conductor? From the perspective of convenience this would be my preferred solution. Are there details regarding the conductor going in and coming out of the hollow mast?
    Thomas
    -----------------------------------
    panta rei

  17. #87
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    Default Re: Lightning protection for a wooden boat with dyneema standing rigging

    I think the critical thing is to keep moisture out of the mast, which you want to do to prevent rot in any case. This discussion has me thinking, however, that a ground let into a groove on the outside of the mast is a better solution if it can be done. Otherwise it's look for a good seal at the masthead and keep an eye on it.
    -Dave

  18. #88
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    Default Re: Lightning protection for a wooden boat with dyneema standing rigging

    Quote Originally Posted by zauberberg View Post
    So you would think, changing from SS standing rigging to dyneema is OK when having a mast internal, massive and well grounded conductor? From the perspective of convenience this would be my preferred solution. Are there details regarding the conductor going in and coming out of the hollow mast?
    Avoid sharp bends in the conductor to reduce the possibility of side flashes. Obviously there has to be a bend for the conductor to exit the base, but the bend can be long and sweeping no problem.

  19. #89
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    Default Re: Lightning protection for a wooden boat with dyneema standing rigging

    Quote Originally Posted by Woxbox View Post
    I think the critical thing is to keep moisture out of the mast, which you want to do to prevent rot in any case. This discussion has me thinking, however, that a ground let into a groove on the outside of the mast is a better solution if it can be done. Otherwise it's look for a good seal at the masthead and keep an eye on it.
    This could be done. A groove along the mast, preferabley along the front or the aft mast side, and a rod running within this groove. But other issues come to mind then: Glued in? Or fixed with mechanical fasteners? Could be also some kind of rectangular profile (see sail track discussion) instead of a circular shaped rod, would be easier to integrate into the mast.
    Thomas
    -----------------------------------
    panta rei

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