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Old 13-04-2011, 10:56   #31
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Re: question about lightning

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Originally Posted by cabo_sailor View Post
Question Gord,

Would a steel hulled or aluminum hulled boat make a natural Faraday cage?

Rich
The oven of your stove is a perfect faraday cage
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Old 18-04-2011, 13:34   #32
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Re: Question about Lightning

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Originally Posted by LEOCAT66 View Post
Thanks for the response Bill. I guess we were lucky, but the damage probably will run a bit. We are not bonded and have never been, and have never been hit before. From what I have been reading lately, it seems that the current thinking on bonding may be changing to non- bonded. We do have a static dissipater, mast top. The really strange thing to me is the Tri-Color. Only 1/2 Green working and no white, while the red is totally fine. I wonder if WHITE LEDs are more prone as the Anchor Light is gone too?
RED LEDS are the first color developed. They are probably more tolerant of temporary overvoltage. Blue and white are higher energy forms of light, the semiconductor has to operate at a higher bandgap to generate these frequencies, so given the junction has a simular electrical breakdown range the white is probably operating closer to the upper limit.

Not to say Red is "lightening proof", you could have just as easily lost them all or none. It just depends on how much energy they had to dissipate, and how much they can take before they melt.
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Old 18-04-2011, 13:52   #33
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Re: question about lightning

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Originally Posted by barnakiel View Post
Hi,

We disconnect and turn off EVERYTHING (this includes our VHF antenna, etc..).

Then we put small electronics into the oven.

Then we sit it out.

Being offshore might help.

b.
Ditto. I make a mad dash to disconnect ALL connections to anything I can get my hands on, power inputs, antennas, grounds, etc. to SSB, GPS. Radar, VHF, computers, etc. It's a real PITA but have heard about too many people losing ALL their electronic gear from a lightning strike. The only things that can't be easily disconnected is the SSB tuner unit because all the connectors are taped tight and the inverter but am thinking about how to arrange a quick disconnect for it.
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Old 18-04-2011, 13:55   #34
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Re: Question about Lightning

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Originally Posted by psneeld View Post
EMP...electromagnetic pulse...generated by a nearby lightening strike....generates surges in nearby electrical wiring...whether hooked to anything or not.
This is absolutely correct, and in addition one should understand that the EMP pulse is directional, that is radiates out from the bolt. Conductors perpendicular to the polarity of the magnetic field generate higher voltages and amperages than conductors aligned in the direction of travel of the pulse. This can explain some of the strange effects where some electronics of even the same type can be affected and others not affected. Unfortunately there's no way to predict in advance what it will be. Minor differences in alignment can result in some devices exceeding their damage threshold and others not.

4 years ago a bolt hit a steel piling 4 slips away. I lost my VHF and one channel on my depth sounder on my seatalk buss. The depth sounder still works fine, but kills the seatalk buss if you plug it in. None of the other instruments were affected at all.
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Old 18-04-2011, 14:14   #35
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Re: Question about Lightning

The best path to ground is how one lessens the likelihood of a strike blowing a hole in the hull or blasting the mast through the bottom. The pointed rod on top, (with or without "Ion dissipater" bristles) takes the hit, and the mast conducts it to your ground plate or better yet, metal hull, with an 00 size wire. Also grounding the metal rigging and LARGE metal parts, adds to the safety, and lessens side flashes. The above has been the standard for many years, and there is no controversy about it among scientist who are experts in the field.

No, the above does not make you MORE likely to be hit, in that having the metal stick up there alone, is invitation enough!

Protecting your electronics from inducted damage with a Faraday cage should work, but is highly impractical! I keep a small spare GPS in a thick wrap of aluminum foil, away from other metal, but have no idea if it helps.

The jury is out regarding "Ion Dissipaters". They HAVE been proven effective on all the Cell towers in the world, for whatever that's worth. We have the expensive one with over 1000 points.

DOZENS of boats, trees, and docks around us , as well as the water itself, has been hit over the last 15 years. We have been spared however! Could be luck? If we do get hit and survive, the rig & hull will very likely be intact!

We have lost a few electronics due to these close calls however. Just like hand grenades: "Close is goodenuf".

Mark
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