A "shocking" experience I had earlier this summer led me to look into lightning protection. We were sailing on the Potomac River under a threatening sky when I leaned over to shut of the outboard gas I was surprised by a distinct electrical jolt from the motor. Tried a couple more times to touch both the motor and mounting and got shocked both times. These were not carpet sparks, but pretty strong jolts. The storm never broke, and we saw lightning only on the horizon, and we went on to sail in the planned race. My googling led me to an article titled "Lightning and Sailboats" from the University of Florida Seagrant Program, which can be found at: http://edis.ifas.ufl.edu/SG071 Lots of good information there on protection systems and their value. I learned a few quotable facts: Strikes in fresh water cause significantly more damage than in salt water due to the lower conductivity of fresh water. Protection systems should provide a direct path from the base of the mast to the water. Stainless stays should not be used due to their lower conductivity than the aluminum mast. Lightning will likely follow the mast anway. As in most things, there are no easy answers, and no protection systems will guarantee no damage or injury. Rick M-17 #633 Lynne L On Wed, Sep 9, 2009 at 11:21 AM, DavidCPatterson Patteson < davidcpatterson@msn.com> wrote:
A general question for the list: what have sailor's done to handle grounding for lightning protection on their Montgomeries? I was sailing on Lake Granby in Colorado, at 8280 or so feet above the sea. A thunderstorm passed nearby, seemingly very low overhead at that altitude. Static snapping from the backstay to my back alerted me to the electrostatic charge accumulating on Cloud Girl, my M17. When I sat forward I could hear static begin to rhythmically snap from the tip of an anchor on the cockpit bench to one of the hinges there. Needless to say, I headed more near the shore, where something was higher than my mast, in this case a rocky and tree-covered mountain side. My friend Mike called me later to tell me he was experiencing the same phenomenon on his M15, La Pequenita, at a dock a few miles away across the lake, where he couldn't touch his boat without a discharge of static. The next day of my four day mini-cruise up there I reached away from another storm, this one showing lightning on the mountain peaks to the north. Since then, I have been researching static dissipators and grounding plates and braided copper straps and so on. Please share your system if you have installed one. What were the elements, how did you route them, where did you put the external grounding plate (if you used one), etc? Chance of being hit by lightning in a sailboat, I read, is .02% or so. Actually pretty high. Higher if it has an inboard engine, or you are in Florida. Or perhaps on a high mountain lake in an electrical storm! I would appreciate any system descriptions. Thanks, David, M17 #393 _______________________________________________ http://mailman.xmission.com/cgi-bin/mailman/listinfo/montgomery_boats
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