The big mystery about lightning is just that - you never know what it is going to do. I've had a half dozen friends whose boats have been struck. On my buddy's Thunderbird (plastic one), he couldn't understand why the boat was taking on water. Nothing was bothered except the depth sounder, which was located on the centerline in front of the keel - and it was just loosened in its thru-hull, not any more. He motored down his 'creek' and across the river to the boat yard - and called them to have the travel lift ready - motored into it, they hauled and the sounder literally fell out!
Another had everything boiled on a Morgan 38, including a hole in the hull - fortunately he was in a slip in water that was only a foot deeper than his keel.....He had one of those whisk broom thingies on the mast - no help. And it goes on. Gary ----- Original Message ----- From: Marek Dziedzic To: cnc-list@cnc-list.com Sent: Friday, January 17, 2014 3:05 PM Subject: Re: Stus-List Electronics GPS I don’t want to get into a scientific discussion, but the main point about lighting strikes and faraday cages is that the amount of energy in the lighting strike is huge and the faraday cages that we use (ovens, antistatic bags, aluminum foil wrap and even many of the commercially available cages) are not perfect (they have openings, the holes in the net are often too big, they have sharp edges, their grounding is of non-zero resistance etc.). The combination of these two factors creates a situation where it is a bit of a crapshoot of what would and what would not survive. Having said that, it is probably better to protect these instruments to whatever degree is reasonable (I cannot see anyone carrying a heavy safe to keep a handheld GPS in it). Marek ------------------------------ Message: 2 Date: Fri, 17 Jan 2014 13:21:58 -0400 From: Rich Knowles <r...@sailpower.ca> To: cnc-list Cnc-List <cnc-list@cnc-list.com> Subject: Re: Stus-List Electronics GPS Message-ID: <b3f341b3-bfba-4627-9e30-7da232f67...@sailpower.ca> Content-Type: text/plain; charset="iso-8859-1" This is an informative site about Faraday Cages: http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Faraday_cage.html We had them at maintenance shops located at TV and radio transmitter sites to enable interference-free equipment testing in high RF environments. Direct lightning strikes on transmission antennas and equipment were always a crap shoot as to what damage would be incurred. All towers, buildings, cages and protective devices were religiously grounded. Some times they would survive direct hits, and, at other times, damage would occur ranging from catastrophic to minor. Always a surprise. Rich Knowles INDIGO LF38 Halifax, NS. ------------------------------------------------------------------------------ _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com
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