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RE: [campernicholson] Lightning Protection

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  • JIM TEIPEN
    Albert, Articles that I ve read on the topic over the years don t seem to have any real consensus on the topic. Ground plates on the bottom of the hull seem
    Message 1 of 12 , Jul 3, 2008
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      Albert,

      Articles that I've read on the topic over the years  don't seem to have any real consensus on the topic.  Ground plates on the bottom of the hull seem to be common,  but other sources I've read say this isn't a good idea since lightening can leave a hole at the point of exit to the water.  These articles say that its better to run a heavy conductor either from a shroud or from the mast itself directly to the water.   In the situation like you described where you were caught out in a storm, you might consider carrying a something like a heavy duty car battery jumper cable to use as a temporary ground for your mast or shroud to the water.  

      Jim
      Alegria
      CN 35 - 68


      To: campernicholson@yahoogroups.com
      From: Albert_Boyce@...
      Date: Tue, 1 Jul 2008 22:06:19 -0400
      Subject: [campernicholson] Lightning Protection

      I am wondering what other Nicholson 35 owners have done for lightning
      protection. I have developed a keen interest in lighting protection
      after getting caught out on the Chesapeake in a thunderstorm last week
      and getting a mild electric shock at the helm while steering the boat.
      Quite a wake up call. I have hull number 132 and there is a small
      sintered bronze plate on the outside of the hull that is connected by #8
      wire to the mast.

      None of the shrouds, stays, lifelines, stanchions, or any other metal
      objects are grounded or otherwise connected to this plate

      I look forward to hearing what lightnting protection arrangements others
      have in place on their boats.

      Al Boyce
      Discovery CN35 #132

    • Graham Norbury
      Jim, There are a lot of myths and misinformation surrounding lightning protection. Fortunately the laws of physics still apply, so there are some basic
      Message 2 of 12 , Jul 4, 2008
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        Jim,

        There are a lot of myths and misinformation surrounding lightning
        protection. Fortunately the laws of physics still apply, so there are
        some basic precautions that a vessel owner can take to maximize their
        safety and that of the vessel. Unfortunately there isn't much that can
        be done to protect onboard electronics as these are often damaged by
        high voltages induced on internal wiring connected to sensitive
        integrated circuits.

        1. Provide a suitably sized, low resistance path to ground leading
        directly down from the air terminal.
        In the case of a sailboat, the air terminal is either the top of the
        aluminum mast, or pointed rod mounted ABOVE the highest fixture (e.g.
        vhf antenna) on the mast. ABYC standards dictate the minimum surface
        area of an underwater grounding plate for both salt or fresh water, and
        also the use of minimum 4 AWG conductor size to connect the air terminal
        (base of aluminum mast) to the grounding shoe.
        NOTE: stainless steel is a poor conductor compared to aluminum or
        copper, so relying on your standing rigging as a primary grounding
        conductor is likely to lead to turnbuckle or swage damage.

        2. Provide suitably sized secondary grounding paths, to minimize side
        flashes and crew hazard.
        All exposed metal such as shrouds, lifelines, stanchions, binnacle,
        pushpit & pullpit should be grounded with minimum 6 AWG sized
        conductors, leading to the primary grounding point. In addition, metal
        hardware such as water or fuel tanks located near the primary conductor
        (mast base) should also be bonded to prevent side flashes.

        3. A lightning strike delivery huge energy in a very short duration.
        With properly sized hardware and low resistance connections, there is
        really no reason for anything to heat up enough for damage to occur.
        Most vessel suffering hull damage either had an inadequate ground system
        (if at all), or defective/corroded underwater fittings that became
        impromptu grounds.

        While I don't have the standards book in front of me here at home, if
        anyone wants more information, feel free to contact me directly.

        Graham
        ABYC Certified Marine Electrician
        Oxford Boatyard, Oxford, MD

        JIM TEIPEN wrote:
        >
        > Albert,
        >
        > Articles that I've read on the topic over the years don't seem to
        > have any real consensus on the topic. Ground plates on the bottom of
        > the hull seem to be common, but other sources I've read say this
        > isn't a good idea since lightening can leave a hole at the point of
        > exit to the water. These articles say that its better to run a heavy
        > conductor either from a shroud or from the mast itself directly to the
        > water. In the situation like you described where you were caught out
        > in a storm, you might consider carrying a something like a heavy duty
        > car battery jumper cable to use as a temporary ground for your mast or
        > shroud to the water.
        >
        > Jim
        > Alegria
        > CN 35 - 68
        >
      • MICHAEL FORSDYKE
        Hello Albert When Blue Days (35/209) was built, Camper and Nicholson earthed the mast to an 8 x 2.5 Dynaplate, mounted adjacent to the mast on the
        Message 3 of 12 , Jul 5, 2008
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          Hello Albert
           
          When 'Blue Days' (35/209) was built, Camper and Nicholson earthed the mast to an 8" x 2.5" Dynaplate, mounted adjacent to the mast on the starboard side. Originally they fitted a rather small wire but, at my request, replaced this with a wire of starter cable proportions.
           
          More recently I have fitted surge protection devices at the base of the mast in the downleads for all the masthead aerials. These are also earthed to the same Dynaplate. The devices, supplied by RS in England, are of the type used to protect commercial radio aerial installations and are suitable for most coax wires. They are rather expensive but much cheaper than replacing toasted electronics! Admittedly this does leave the wind speed/direction sensor unprotected but I have not found anything suitable for the multi-core wire from this.
           
          I don't claim any expertise in this field but assume that the action I have taken improves the chances of surviving a lightning strike without damage. To my knowledge the installation has not been put to the test but, should a strike ever happen, I hope the lightning will find that the earthed mast provides a better route to earth than the other masthead equipment which have a degree of inherent isolation.
           
          I hope this adds something useful to this interesting discussion.
           
          Regards,
           
          Michael Forsdyke
           

          "Albert G. Boyce" <Albert_Boyce@...> wrote:
          I am wondering what other Nicholson 35 owners have done for lightning
          protection. I have developed a keen interest in lighting protection
          after getting caught out on the Chesapeake in a thunderstorm last week
          and getting a mild electric shock at the helm while steering the boat.
          Quite a wake up call. I have hull number 132 and there is a small
          sintered bronze plate on the outside of the hull that is connected by #8
          wire to the mast.

          None of the shrouds, stays, lifelines, stanchions, or any other metal
          objects are grounded or otherwise connected to this plate

          I look forward to hearing what lightnting protection arrangements others
          have in place on their boats.

          Al Boyce
          Discovery CN35 #132

        • JOHN LARSON
          Hi John and Gail We re heading for Passport on the 28th or 29th of July and will be around Rockland for a few days getting ready, then cruising Penobscot bay
          Message 4 of 12 , Jul 6, 2008
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            Hi John and Gail
             
            We're heading for Passport on the 28th or 29th of July and will be around Rockland for a few days getting ready, then cruising Penobscot bay also.  Lets stay in touch and try to meet somewhere, hopefully with the rest of last year's group.
             
            We haven't had any squeaking from the helm, but we did have a knocking noise which turned out to be worn rudder shaft packing.  We replaced the packing and the noise went away, at least so far.
             
            You may develop topsides envy when you see Passport, but you're bank account is likely in a lot  better shape than ours.  All that prettiness costs lots.
             
            Hope to see you two and the rest of the group while we're in Maine.
             
            John and Sandy Larson
            s/v Passport
          • galljj35
            Our plans are to be in Holbrook Harbor (Castine) for 27th/28, two nights in Belfast (29/30), the 31st - thursday - in Dark Harbor on Isleboro or thereabouts
            Message 5 of 12 , Jul 8, 2008
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              Our plans are to be in Holbrook Harbor (Castine) for 27th/28, two
              nights in Belfast (29/30), the 31st - thursday - in Dark Harbor on
              Isleboro or thereabouts and in Rockland the 1 and 2nd of August.

              From there we will probably go to Perry Creek on Vinalhaven. After
              that we'll wander aroound, but we'll leave from Tenants/Port Clyde on
              the 6th (at the latest) for Gloucester

              Hope we can get catch up.

              As to my bank account, I would rather have invested it in my hull,
              rather than watch it evaporate as it has done in the past few
              months !!

              john


              --- In campernicholson@yahoogroups.com, "JOHN LARSON" <jsl-sll@...>
              wrote:
              >
              > Hi John and Gail
              >
              > We're heading for Passport on the 28th or 29th of July and will be
              around Rockland for a few days getting ready, then cruising Penobscot
              bay also. Lets stay in touch and try to meet somewhere, hopefully
              with the rest of last year's group.
              >
              > We haven't had any squeaking from the helm, but we did have a
              knocking noise which turned out to be worn rudder shaft packing. We
              replaced the packing and the noise went away, at least so far.
              >
              > You may develop topsides envy when you see Passport, but you're
              bank account is likely in a lot better shape than ours. All that
              prettiness costs lots.
              >
              > Hope to see you two and the rest of the group while we're in Maine.
              >
              > John and Sandy Larson
              > s/v Passport
              >
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