Lightning!

Discussion in 'Boat Design' started by FAST FRED, Oct 7, 2007.

  1. FAST FRED
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    Am in the process of working up a new power boat design and am afraid I'm going to be stuck with an electronic engine .Tier II and all that crap.

    Since we live near the Lightning Capital of the world , 1000+ strikes a day , this doesn't thrill me. I'd hate rowing a 38 ft boat home.

    In fact it would force an aluminum boat , rather than the GRP/ Airex were used to building.

    I read Boeing uses a copper mesh net in the hull of the 787 to help with this problem , and wonder if it would work on a boat?

    Boeing probably is able to keep those big volts on the skin till it bleeds off , on a boat the good conducting sea water is close!

    So would I simply be blowing an exit hole in the boat?

    FF
     
  2. Retired Geek
    Joined: Mar 2006
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    Retired Geek Junior Member

    Fred,
    Aircraft use discharge wicks that the charge is led to so you don't blow/burn holes in the wings or fuselage. Not sure what sort of copper mesh that Boeing use, but I have read that a copper indium mesh is best (indium encapsulated in copper). Basically indium is one of those nice materials that goes thru a phase state change at low temperatures and closely approximates a super conductor while in a liquid state. I may have this a little wrong as I read it quite a while back, but I think the basics are correct.
    RG
     
  3. StianM
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    StianM Senior Member

    Would it not just be easier to mount something in steel on the boats highest point and let it folow a cable down to the water?

    I don't think I would put it inside a GRP hull since it would turn hot and develop gas bubles inside(my limited understanding would say it would)

    I seen lots of tall old buildings having copper cables from the highest point and down to ground.
     
  4. Frosty

    Frosty Previous Member

    Its quite common to see little like wire brush things on top of mast these days. I think they call this a defuser. It is supposed to dissipate the static electricity in the boats rigging that attracts the lightening in the first place.

    I have no idea if they work or not, seen plenty around though.
     
  5. Busman1965
    Joined: Jun 2007
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    Busman1965 Junior Member

    Lightning

    I ran a marine electronics business here in Florida for about 10 years, and delt with lightning hits on a daily basis in the summers. Those wire brush diffusers dont work, they are just a toy. I would not try to use mesh screen in a hull, as it will melt the laminates, I have seen it on large motoryachts, with copper screen used for SSB counterpoise. Your only bet is to use a heavy metal mast, which is grounded directly to the water with a large conductor. Sportfish boats have metal tuna towers, and are regular targets for lightning, when grounded proplerly, they survive direct hits, with no structural damage. Of course, all the electronics are destroyed, but the boat survives! There is no way to prevent the electronics from damamge, except disconnecting them.
     
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  6. Man Overboard
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    Man Overboard Tom Fugate

    You may find this on line training video of some help:

    http://tcr-conference.com/marine/

    It is sponsered by Pro Boat, and produced by:

    http://marinelightning.com/

    The video does a good job of explaining how lightning travels through a boat; after watching it, you will rethink how you protect your vessel against lightning.
     
  7. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    If your boat is Aluminum or Steel. no-problem boat provides ground for lighting and Farady cage for electronics, but electrical need to be separate from hull. If fiberglass then isolate shafts from engines, engines can be isolate from hull. Run that run a big cable or two like 00 from tower and ground to shaft ground. Use propellers or rudders to ground. This should be able to take direct hit without sinking boat or killing electronics but lighting is funny thing.

    I was on a big Bertram when it got hit. It blew engine batteries and most electonics. Not only that but it was pitch dark and was in 10 foot seas. Somehow, we got one engine started using a house battery that we connected directly to engine. Fortunately we were only 20 miles offshore.

    The boat had several 100k in damage. The second engine lost all electronics, generator, all navigation, radar and even the frig was bad. According to insurance guy apparently - this happens all time
     
  8. TerryKing
    Joined: Feb 2007
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    TerryKing On The Water SOON

    Lightning VS Electronics

    I'm watching the Lightning presentation mentioned below... Very Interesting, and consistent with what I have thought about for years now.

    I worked as a Broadcast Engineer on AM and FM systems on high towers for 20 years, and have a lot of experience with actual lightning damage. Now I'm working on design of Onboard Computer Systems and NMEA0183 sensors and combiners. Take a look at:
    http://www.boatdesign.net/forums/showthread.php?t=19458
    where we're discussing this...

    I'd like to follow the whole subject of Lightning Protection for Watercraft!

    I'm looking at isolating sections of onboard electronics systems with either Wireless USB , Fibre Optics, or at least with high-voltage optical isolators.
    Is anyone else working on this?? Maybe we can start/sustain a thread in the
    area of http://www.boatdesign.net/forums/forumdisplay.php?f=47
     
  9. Man Overboard
    Joined: Oct 2006
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    Man Overboard Tom Fugate

    Actually, copper is best; a minimum of 1/2 inch rod. It is not as easy as just running it to a 1 foot square plate on the bottom of the boat. Lightning likes to dissipate along the surface of the water. Not always, but some times lightning will skip running down and dissipating out the ground plate and just flash through the side of the boat at , or near the surface of the water.
     
  10. Ike
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    Ike Senior Member

  11. TerryKing
    Joined: Feb 2007
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    TerryKing On The Water SOON

    Bad and Good??

    First, if you're really interested in this stuff, look at:
    http://tcr-conference.com/marine/
    as Tom suggested earlier. It's really worth the time.

    In a nutshell, the old system of lightning protection from mast down thru the center of the boat is BAD:
    [​IMG]

    and a configuration that conducts lighting around the OUTSIDE of the boat and avoids side-flashes is GOOD:
    [​IMG]
     
  12. Frosty

    Frosty Previous Member

    Its by no means lightening free here in the northern Malaaca straits. I have seen people attach another spare peice of rigging wire to one of the shrouds with bulldog clips and let the end trail in the water.

    Whilst this might seem a good idea it is my opinion that the very small amount of contact on the two wire would mean that if there was such a strike it would just blow it apart. Better than nothing I suppose.
     
  13. Man Overboard
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    Man Overboard Tom Fugate

    I'm curious as to how you might better protect the electronic gear? If you have to disconnect it during a lightning storm to protect it, then I think it is worthwhile to do so. Maybe a quick disconnect that all power lines feed into. Plus, all of the antennas would have to be disconnected, including Radar.
     
  14. Ike
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    Ike Senior Member

    Well, protecting the electronic gear is problematic. If it's hooked up or running when the lightning strikes then the odds are it will get fried. If you have some warning you can turn everything off and disconnect it. I talked to a fellow who said put it in the microwave. I thought about that for a while and realized it might work, because a microwave oven is surrounded by a cage, essentially a Faraday cage. For those who don't know what a faraday cage is, it is a mesh cage, usually copper used to surround electronci equipment to isolate it from outside interefernce. It finds uses in all kinds of things. It's used to protect sensitive electronic test equipment when it is being calibrated. It's used on warships to protect electronic equipment from large emf and emr pulses. So in theory you could use one to protect electronic equipment on your boat from lightning. However, it's not very practical on a small boat.
     

  15. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    "Of course, all the electronics are destroyed, but the boat survives! There is no way to prevent the electronics from damamge, except disconnecting them."

    Sounds like the beer can boat would be required to have any chance at using an electronic injected engine.

    The starter could be Hydraulic (as on rescue boats) and I guess it will have to be a mechanical engine ,& damn the buroRATS

    FF
     
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