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    Re: Status of Celestial Nav in 2015
    From: Bob Goethe
    Date: 2015 Mar 8, 08:13 -0700


    >>I have seen the results of lightning strikes on aircraft and have never known one take out all systems. <<

    This makes sense.  With its metal skin, an airplane is essentially one giant Faraday Cage.  Most of the electronics ought to survive.  This would be the case with the steel hulls of commercial and military vessels as well.  Most of the research on EMP and vessels has been done by the military, and relates pretty specifically to steel hulls. 

    There has not been much research done on lightning and vessels with fiberglass hulls.  I have a research paper around here somewhere from the University of Florida that says as much, but I can't lay my hands on it right now.  Most of what the article does is talk about what is NOT known about lightning and fiberglass hulls, and say "More research is required" (which is a pretty safe way to finish any paper, on any topic).

    >>I feel a couple of cheap GPS units and a plentiful supply of top grade batteries would see the average yachtie out of trouble.<<

    I was able to find again the posting at CruisersForum.com that really shook me up when I read it.  I reproduce it below.  The bolding of some words is my own.

         We took a hit on our mooring in August 2010. Neighbor said the lightning
         hit the water right at our stern quarter. It did not come down the mast. The 
         strike came in through the ground side of the system and took out nearly 
         everything. Even the PSS seal had carbon blown all over the engine bay. 
         It survived but it gave me the creeps... The only things to survive were a 
         couple of pumps, macerator and shower sump..

         We also lost a bunch of devices not even 
         plugged in to anything. Lost the EPIRB, iPod, Laptop wifi 
         and other features (laptop turned on but was severely compromised), three 
         hand held GPS devices including one that was in a ditch bag wrapped in tinfoil & 
         stored in a ziploc with desiccant.. None of these devices were even plugged in 
         but were still toasted.

         On the AC/DC panel some breakers survived and some did not. All volt gauges, 
         tach, temp, etc. were also fried. Alternator VR was fried. All lighting aboard was 
         LED and all was 100% toast except for one in the v-berth that still works, very odd. 
         Engine starter survived but the solenoid died six months later no-doubt due to the 
         lightning strike. Radar, wind, depth, speed, AP, two plotters, Garmin network hub, 
         VHF, TV, stereo, cell phone amplifier and much more were all fried too..


    It goes without saying that if your battery powered EPIRB (emergency position indicating radio beacon) gets blown, you have the beginnings of a real problem.

    Now, from what I understand of Faraday cages, his attempt to protect a hand-held GPS with by wrapping it in foil and putting it in a plastic bag was getting things just backwards.  You want to have your electronics, surrounded by an insulator, surrounded by a conductive foil (or fine mesh).   Wrapping it in foil and THEN putting it in a baggie may leave you destined for failure.

    That said, the destructiveness of the EMP described above is sobering...and makes me think that bringing my sextant along as carry on luggage when I am going to join a (fiberglass) sailboat on a cruise from Hawaii to Victoria:  well, this is just a good, prudent idea, handheld GPS units not withstanding.

    Having 3 hand held GPSes in cupboards is not true redundancy for your onboard GPS.  It is close to having a single point of failure for all navigational systems.

    It makes sense to me that this description comes from a yacht that was at a mooring.  Had such damage been sustained by a yacht at sea, they could easily join those 40 or 50 vessels a year overdue-and-presumed-lost. 

    If you are 1,000 miles out from Hawaii, and Tahiti is still 1,400 miles away, and you have a catastrophic loss of electronic navigation, there is no place handy that you can put in at.  In that situation, it is navigate by sextant or die at sea.

    Of course, your odds of being struck by lightning are remote.  I tell my sailing friends that they are most likely going to do fine at sea, and don't need celestial as long as they are willing to take responsibility for their actions.  As long as they are willing to die like men, and not whine about how unfair the universe is, then they will say, "Yes, I am going to die, and lose a $250,000 sloop, but I did by God save $600 in not buying a sextant.  The only thing for it now is to lash my hands to the wheel, so that if I ever AM found, somebody will at least make a song about how I died doing my duty to my crewmates."


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