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Old 04-06-2008, 12:13   #16
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Originally Posted by GordMay View Post
An aircraft, which cannot be solidly grounded to earth, is not a boat, which can (be).
I don't think a million volts/amps running through/over fiberglass and electronics seeking ground really cares if it's in the water or air.
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Old 04-06-2008, 12:21   #17
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Aircraft mitigate the lightning to the EXTERIOR! They keeps the volts/amps away from the electronics by channeling it over the skin of the plane. Trying to channel lightning through the interior of anything does not seem to be the best safest way to try to avoid problems. Just my thoughts and the thoughts of Areospace engineers that design planes to be hit by lightning and land the passengers safely.
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Old 04-06-2008, 12:56   #18
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After having been struck once in 1995 while sailing I have resorted to an old and tried method for preventing lightning strikes ...... prayer. So far so good. For what it's worth I read nearly everything on boats and lightning after being hit and found that nothing I could do to the boat would prevent a strike. If bonding, un-bonding, dyna plates, dragging cables from the chainplates etc. make you feel better go ahead and do it but it will not prevent a strike.
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Old 04-06-2008, 13:13   #19
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After having been struck once in 1995 while sailing I have resorted to an old and tried method for preventing lightning strikes ...... prayer. So far so good. For what it's worth I read nearly everything on boats and lightning after being hit and found that nothing I could do to the boat would prevent a strike. If bonding, un-bonding, dyna plates, dragging cables from the chainplates etc. make you feel better go ahead and do it but it will not prevent a strike.
My point exactly. You can't prevent a strike, but you can try to stop the lightning from letting the magic smoke out of your electronics. Once the magic smoke is let out the electrons don't flow no more.
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Old 04-06-2008, 13:33   #20
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When lightning strikes the fiberglass radome, happens 100s of times a year, it is mitigated by closely spaced small metal disks glued to the surface. The lightning jumps the gaps creating an ionized path that it will follow.
Huh!? The dome is just a fibreglass dome. It has to be or the radar would not work through the dome.
The big difference with the aircraft against boat, as Gord stated, is that the boat is grounded to good solid earth. This results in a higher voltage and current being disipated to earth than a strike to a body that is not on a solid ground. Ground in this case means electrical ground. A strike in the air is very different to a strike on the ground. And the rare events of aircraft being hit on the ground usually result in a lot of severe damage.
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Old 04-06-2008, 14:29   #21
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Has anyone looked into lightning mitagation systems on aircraft? The radome on the front of the planes is fiberglass and they have very expensive electrions behind them. When lightning strikes the fiberglass radome, happens 100s of times a year, it is mitigated by closely spaced small metal disks glued to the surface. The lightning jumps the gaps creating an ionized path that it will follow. The fiberglass/electronics are saved. The same thing should work on a sail boat. Mast ungrounded, closely spaced small metal disks glued to the exterior of the hull from the shrouds/chain plates down to the waterline. I am going to do this on my boat. I figure that if hundreds of planes are hit every year and none of them have fiberglass radome/electronic damage it must work. If the disks stay on at 500mph they should stay on at 8 kts. It may be worth looking into. Any comments?
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By “metal discs”, I presume you are referring to some sort of “static wick”, which dissipate static charges accumulated because of the aircraft’s high speed (not usually an issue /w sailboats – well perhaps some catamarans J).

A static wick is a piece of metal connected electrically to the frame of the aircraft, usually with one or two spikes or needles on the end. It is housed in a fibreglass rod to insulate it from the airplane.

Because the spikes concentrate the electric charge around them, and they are connected to the airframe, they allow the airplane to dissipate any static charge it may build up* out into the air.

* Aircraft can pick up a static charge by flying through charged air. When they return to the ground, they can hold the charge for a considerable time, sitting on their rubber tires. A real danger exists if the charge sparks when refuelling.

737: There are static dischargers (either wicks or rods) at the tips of the wings, stabiliser and fin. They encourage the static build-up on the airframe to bleed off which would otherwise accumulate and cause radio interference, particularly of ADF & HF.

Note that they are not for lightning protection.
Goto: Instrument Probes
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Old 04-06-2008, 14:33   #22
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Huh!? The dome is just a fibreglass dome. It has to be or the radar would not work through the dome.
The big difference with the aircraft against boat, as Gord stated, is that the boat is grounded to good solid earth. This results in a higher voltage and current being disipated to earth than a strike to a body that is not on a solid ground. Ground in this case means electrical ground. A strike in the air is very different to a strike on the ground. And the rare events of aircraft being hit on the ground usually result in a lot of severe damage.
In order for the radome not to be blown apart/damaged by lightning and the electronics inside damaged by the lightning they direct the lightning around the outside of it. Think Faraday cage. You want to direct the lightning around the object not through it. The potential energy is no more or less (voltage is not increased by an earth ground) If the resistance is lowered the amperage goes up. What every one here is suggesting is to lower the resistance to ground and up the amps. Bad move. Raise the resistance to ground to make a less appealing target for lightning and provide an ionized path if you get hit.
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Old 04-06-2008, 14:41   #23
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By “metal discs”, I presume you are referring to some sort of “static wick”, which dissipate static charges accumulated because of the aircraft’s high speed (not usually an issue /w sailboats – well perhaps some catamarans J).

A static wick is a piece of metal connected electrically to the frame of the aircraft, usually with one or two spikes or needles on the end. It is housed in a fibreglass rod to insulate it from the airplane.

Because the spikes concentrate the electric charge around them, and they are connected to the airframe, they allow the airplane to dissipate any static charge it may build up* out into the air.

* Aircraft can pick up a static charge by flying through charged air. When they return to the ground, they can hold the charge for a considerable time, sitting on their rubber tires. A real danger exists if the charge sparks when refuelling.

737: There are static dischargers (either wicks or rods) at the tips of the wings, stabiliser and fin. They encourage the static build-up on the airframe to bleed off which would otherwise accumulate and cause radio interference, particularly of ADF & HF.
Note that they are not for lightning protection.
Goto: Instrument Probes
They look like US dimes ($.10) glued to the dome with a small gap in between them so when the spark jumps the gap it creates a ionized trail for the lightning to follow. Not even close to the static dischargers.
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Old 04-06-2008, 14:44   #24
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... Raise the resistance to ground to make a less appealing target for lightning and provide an ionized path if you get hit.
Raising the impedance to an effective level is called isolation.
One of the world's foremost authorities on shoreside lightning protection (Bell) replied to my query (bond/ground or isolate?), by asking me "how I would propose to isolate a boat (& all it's systems) sitting in water?"

We might TRY to isolate our boat, intending to make it a less appealing target,; but should we be hit, the consequences would be more severe.
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Old 04-06-2008, 14:46   #25
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Originally Posted by easterly View Post
My point exactly. You can't prevent a strike, but you can try to stop the lightning from letting the magic smoke out of your electronics. Once the magic smoke is let out the electrons don't flow no more.
Thats great, I learned something today. I have seen that magic smoke and never knew what it was. I thought it coincidental that my t.v., computer, auto electronics etc. always seemed to 'end' whenever that smoke leaked out. Is it connected to that awful odor too?
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Old 04-06-2008, 15:30   #26
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This is definately not a good lightning avoidance tactic in itself, but I actually AGREE with Wheels on this one. There is no way to prevent, defer, defacilitate or devinely redirect a lightning strike. There are no mantras, Papal Dispensations, patented devices or gadgets endorsed by unquestionable authorities that have not failed when lightning strikes. Nor is anyone who has done absolutely nothing to prevent, deter, or discourage lighting any more likely to be struck. Karma has no effect. Luck has nothing to do with it. Contrary to what you may see on Television, what you wear, eat, medicate or decorate your body with has no effect whatsoever. Zip. Nada. Niente.

I of course appologize for being so wishy-washy about the subject, but lightning just is and does, and then its gone.

My PDQ 32 was struck by lightning. Every Electronic device on board died. Eye witnesses said it looked like an X-ray on an old "B" movie. The boat was surrounded on three sides by sailboats with taller masts. It was tied up in a floating dock moored by 14" round 9' tall steel pilings driven into the bottom many feet deep. None of the other boats had any specialized lightning protection. An older gentleman, purportedly inebriated was standing on the dock relieving himself when the lightning struck. He was uninjured but somehow strangely affected; The same witnesses said he took off his glasses, threw them on the dock and jumped on them, then left. This is all documented and meticulously filed in the insurance company records. To date no satisfactory explanation of the lack of an exit 'wound' or the older gentleman's behavior has been made.

It is my belief that lightning is just God's way of telling us we don't know Jack.
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Old 04-06-2008, 15:37   #27
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Nice to see someone take a definate position


I've also been struck. Unfortunately I was onboard at the time. Like others in this thread I lost every piece of electronic equipment which was connected to the 12 volt supply. Battery operated devices in the Saloon were unaffected.

Luckily, twin engines and prop shafts were the exit point. Neither of us on board were affected physically nor did we feel a thing. However, I did get hit with debris as everything on top of my mast ended up in the cockpit.
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Old 04-06-2008, 15:46   #28
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Raising the impedance to an effective level is called isolation.
One of the world's foremost authorities on shoreside lightning protection (Bell) replied to my query (bond/ground or isolate?), by asking me "how I would propose to isolate a boat (& all it's systems) sitting in water?"

We might TRY to isolate our boat, intending to make it a less appealing target,; but should we be hit, the consequences would be more severe.
Not isolation, just enough resistance to make your boat a less attractive target, but not enough to cause damage if it is hit. That is how the radomes/electronics on the aircraft are protected. Fiberglass is not a good ground between air and water, bronze through hulls attached to rubber/plastic hoses are not a good ground either that is why we have ground systems/plates. If we put a metal stick on the fiberglass and direct all the volts/amps through the structure while controlling it with no leakage all would be good in life. If we direct the volts/amps around the structure and have 4 to 6 points that it can leak to ground life would be great. It will take some engineeing to come up with the proper spacing for the disks to be used on boats but it can be done. I will talk to my friends at Boeing. I was trying to talk Boeing into sponsoring the engineering for an Americas cup boat.
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Old 04-06-2008, 16:12   #29
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There is no way to prevent, defer, defacilitate or devinely redirect a lightning strike. There are no mantras, Papal Dispensations, patented devices or gadgets endorsed by unquestionable authorities that have not failed when lightning strikes. Nor is anyone who has done absolutely nothing to prevent, deter, or discourage lighting any more likely to be struck.
My PDQ 32 was struck by lightning. Every Electronic device on board died. Eye witnesses said it looked like an X-ray on an old "B" movie. The boat was surrounded on three sides by sailboats with taller masts. It was tied up in a floating dock moored by 14" round 9' tall steel pilings driven into the bottom many feet deep. None of the other boats had any specialized lightning protection. An older gentleman, purportedly inebriated was standing on the dock relieving himself when the lightning struck. He was uninjured but somehow strangely affected; The same witnesses said he took off his glasses, threw them on the dock and jumped on them, then left. This is all documented and meticulously filed in the insurance company records. To date no satisfactory explanation of the lack of an exit 'wound' or the older gentleman's behavior has been made.

It is my belief that lightning is just God's way of telling us we don't know Jack.
OK I give up!
They can't redirect lightning around planes and they are blown out of the sky 100s of times a year and people are dying all the time from it. Lightning takes the path of least resistance, as does all electricty. Your boat was that path, had a better ground, less resistance from the mast to the water. Simple as that.
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Old 04-06-2008, 16:55   #30
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"Magic smoke" - I like it!

The metal disks are there to protect the radome not the radar. The loss of a radome in flight would be an emergency. Whereas the loss of the radar would most likely be just a nuisance. BTW, Airborne radars operate at frequencies that can pass between the disks.

The basic reason an aircraft can survive a lightning strike is due to the bonding of the airframe. It doesn't matter if the aircraft is in the air, on the ground, or floating in sea water. If we could build our boats as complete conductive shells they would also survive lightning strikes better.

However, fiberglass and wood sailboats are a real "hard case" when it comes to lightning protection/mitigation. The best that can be done is to tie everything metal together and provide as much grounding as is practicable.

And, yes, if time and circumstance permits, isolating electronics by disconnecting the antenna and power connections can't hurt the electronics. But, it may be safer to not be holding on to a random piece of wire when that big bright bolt from the sky hits.

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