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Old 12-07-2019, 17:48   #91
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Re: Lightning Protection, pros and cons

[QUOTE=Cpt Pat;
If you take a look at one of those big three-phase distribution lines on high metal towers, you'll see a thinner conductor at the very top that has no insulators. That's called the "lightning leader" line. The hope, usually fulfilled, is that lightning will strike that line instead. It creates a "zone of protection" around the active lines below.[/QUOTE]


It is a total surprise to see one in your windshield for the first time, when flying low.
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Old 12-07-2019, 22:48   #92
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Re: Lightning Protection, pros and cons

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That's why I said "almost never." Here are nine accidents, over many years, that were attributed to lightning: http://lightningsafety.com/nlsi_lls/avaition_losses.html

Many times, the lightning doesn't strike the aircraft - the aircraft instead flies into the superheated plasma channel from lightning passing around and ahead of the aircraft. In these cases, damage is confined to the leading edges of the airframe.

When you consider how many aircraft are in the air at any given time worldwide, flying around thunderstorms, and how few are struck; a metallic-framed aircraft is a relatively safe place to be. Now that composites are being increasingly used, I'm not sure that safety record will continue. And lightning protection is a known engineering challenge with aircraft containing composites.
Fair point, you did say almost never and I guess it depends on one's definition of almost never. Mine must be different to yours and that's OK !

I do make the distinction between aircraft being struck by lightning to those being damaged enough to cause an accident (fatal or otherwise). The damage to almost all struck airborne aircraft is minimal and almost never fatal IME.

I think the real reason so few aircraft encounter lighting strikes is that they can readily avoid lighting (most of the time). Many have weather radar that allows them to dodge thunderstorm cells and others have different storm avoidance technology such as the Stormscope ( https://www.l3aviationproducts.com/products/stormscope/)
These are particularly good for detecting dry thunderstorms.
Finally, aircraft can usually move away from potential strike zones.

So yep, aircraft are safe places to be wrt lightning.
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Old 12-07-2019, 23:36   #93
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Re: Lightning Protection, pros and cons

Ok, so since I started this thread, I reserve the right to reiterate my stupid question: Should I feel reasonably protected that in a strike on my aluminum mast, in my 100% correctly bonded and grounded boat with an SSB plate on the rudder (and a grounded keel cooler plate as well...would that have the same effect?) the charge (as much as can ever be predicted) would likely exit those instead of blowing a hole in the hull? And followup, quick easy jumper leads or maybe even heavier gauge just for the purpose attached to shrouds (or possibly twin attatchments, shrouds and mast bottom? or just mast foot?) led to copper pipe dragged beside the boat to use as necessary would be good?

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Old 13-07-2019, 00:03   #94
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Re: Lightning Protection, pros and cons

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Ok, so since I started this thread, I reserve the right to reiterate my stupid question: Should I feel reasonably protected that in a strike on my aluminum mast, in my 100% correctly bonded and grounded boat with an SSB plate on the rudder (and a grounded keel cooler plate as well...would that have the same effect?) the charge (as much as can ever be predicted) would likely exit those instead of blowing a hole in the hull? And followup, quick easy jumper leads or maybe even heavier gauge just for the purpose attached to shrouds (or possibly twin attatchments, shrouds and mast bottom? or just mast foot?) led to copper pipe dragged beside the boat to use as necessary would be good?

Going back to basics: if your mast is connected by a big fat copper cable routed in a straight (or almost straight) line to a substantial area of metal in direct contact with the sea water, then yes, you are reasonably protected .

If you mast is not connected as described, then you are not reasonably protected.

Assuming a nonconductive (ie fibreglas) hull!

As others have posted, lighting discharge current does not like bends, it hates them and will look for another lower impedance path to the water rather than trying to negotiate a sharp bend. In essence, it sees the bend as high impedance inductance.
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Old 13-07-2019, 01:01   #95
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Re: Lightning Protection, pros and cons

So the aluminum mast is not a sufficient conductor? I do see your point about the bends, so a right angle at deck height would likely be ignored... Altho at that height all other grounds or cables do same so maybe not?
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Old 13-07-2019, 02:24   #96
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Re: Lightning Protection, pros and cons

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So the aluminum mast is not a sufficient conductor? I do see your point about the bends, so a right angle at deck height would likely be ignored... Altho at that height all other grounds or cables do same so maybe not?
The aluminium mast is a sufficient conductor from the top to the base but the lightning wants to get to the surface of the seawater; this is the essence of a cloud to ground (sea water) discharge.

So you have to complete the circuit from the bottom of the mast to the sea water with a big fat straight conductor to a substantial area of metal in the water.

If you don't provide such a conductor, the lightning will find whatever way it wants to and does't care about how it does it!

If you have a steel or aluminium hull you are sweet!
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Old 13-07-2019, 07:05   #97
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Re: Lightning Protection, pros and cons

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This is repeated point of confusion.

Consumers imagine lightning protection systems will protect against the risk of being hit by lightning. In practice even the best systems have very little effect on the chance of strike.

Lightning protection systems are designed to reduce the chance of damage, especially catastrophic damage, if a strike occurs. They have very little effect (if any) on the risk of experiencing a strike.
Yes, now. Maybe I should have dated myself, this was in the 70’s. But, there was a ton of research and effort before that (and, still is to some extent) on how to prevent strikes in the first place.

And, I agree, I don’t there is much you can do to stop lightning from striking where it wants to.
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Old 13-07-2019, 07:37   #98
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Re: Lightning Protection, pros and cons

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We were hit by lightning on a previous vessel.
We had boats near us with taller masts.
We had earth (electric start outboard) in the water

Damage was everything electric over $20 toast
Everything else good

Gotta wonder how a modern electronic engine would have fared in that case.
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Old 13-07-2019, 11:25   #99
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Re: Lightning Protection, pros and cons

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It is a total surprise to see one in your windshield for the first time, when flying low.
Yep. We helicopter pilots are taught to fly over the towers - not the wires. You can see the towers.
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Old 13-07-2019, 11:34   #100
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Re: Lightning Protection, pros and cons

A suggestion: If you have an aluminum prop, instead of using bronze as a ground plate, use zinc. Why? Zinc doesn't contribute to galvanic corrosion of an aluminum prop. I tried bronze - and dissolved my prop. Oops.
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Old 13-07-2019, 11:43   #101
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Re: Lightning Protection, pros and cons

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I think the real reason so few aircraft encounter lighting strikes is that they can readily avoid lighting (most of the time).
True. Thunderstorms eat airplanes. Big ones, little ones, transports and fighter jets. Thunderstorms are omnivorous. The only people I know who are crazy enough to fly toward thunderstorms are glider pilots. (Lots of lift.) As a glider tow pilot, I've dreaded the times the glider kept steering me toward the base of the nearest thunderstorm.
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Old 14-07-2019, 20:06   #102
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Re: Lightning Protection, pros and cons

I got tagged by lightning and have a dissipator and grounding last month in Koh Lipe, Thailand. Did my VHF, SSB, pactor modem, wind instruments, AIS, autpilot, charger inverter, back up plotter, lights, gas stove control, camera up mast, control panel, and regulator. I was on a mooring bouy, woke up at 2am wondering if I was having a heart attack as my body was having spasms, and then I realised I was being shocked. VHF antenna decimated. I am insured and the insurance company has been pretty good. Contractors and trying to get quotes - exasperating.
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Old 14-07-2019, 21:29   #103
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Re: Lightning Protection, pros and cons

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Finally, aircraft can usually move away from potential strike zones.

So yep, aircraft are safe places to be wrt lightning.
True...usually but not always....esp in arrival or departure corridors...

One day on departure out of Hong Kong we had HUGE cbs all quadrants.....was watching cloud to cloud lightning. Asked for deviation left...."unable due to traffic " Turn right heading whatever.."unable due to severe weather" So we flew pretty much straight ahead in-between two large CBS with cloud to cloud lightning...then, BANG!....big strike right in front of the co-pilot's windshield...loud as hell.

That was just one instance...been struck multiple times over the last 41 years. Damage was usually pin holes, but know of worse like blown up radomes etc.
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Old 15-07-2019, 00:59   #104
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Re: Lightning Protection, pros and cons

I think that the lightning protection you had fitted probably saved your life.
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Old 15-07-2019, 01:39   #105
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Re: Lightning Protection, pros and cons

Hi, it's me the OP again Don't know how practical this is, but since I keep hearing the straightness of the line is of paramount importance, and that cables clipped to shrouds or alu mast foot would make a big right angle to the water on our GRP boat, at least for anchorage protection, what would it be like to have a properly rounded copper lightning rod assembly of some sort (2 ft rod with weight at bottom) with 20m of #2 or #4 gauge copper wire terminating in a copper pipe piece. Attach to spinnaker halyard at anchor, hoist it to masthead where the rod is above everything and drop the pipe-end in the water over the side?

This would create effectively a straight (if angled slightly) path right to the water. Storage wouldn't be horrible coiled. Makes more sense if anchoring always in Florida or the like, but on paper, would this be a good solution?

Of course now I'm thinking of hard-wiring the top piece and cable down along a shroud, and having a clip on at the bottom for the last 2 meters, so it could be used sailing as well.... wouldn't add much weight or windage, and we're not a performance boat...thoughts?
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