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Old 07-05-2012, 20:46   #31
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Re: Simple Lightning Protection Idea?

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Originally Posted by GordMay View Post
The following statistics are based on all of the BoatUS Marine Insurance claims for lightning damage over a five-year period.
Goto ➥ BoatUS.com - Seaworthy Magazine

See also ➥ Catamarans

I believe that is a summery of what I read. Still relevant... I'm guessing they removed it from the web so they could sell it to the magazines
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Old 26-01-2013, 02:23   #32
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Re: Simple Lightning Protection Idea?

Cats are supposed to be struck 2x as much as monohulls so I installed this lighting wire with fixtures and attached it to the base of my mast . I fit it into a garden hose then dropped it directly down & out a drain hole in the anchor locker without any bends - Hoping it will help if ever struck- stays out full time when sailing- cost about- $35usd & 1/2 hour of time- not sure if it help, but atleast its a try?
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Old 26-01-2013, 07:42   #33
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Re: Simple Lightning Protection Idea?

great idea. the more chains the better. jazz it up with brass strip connectors tightly secured. and tests show that a dome shape in brass/cu/bronze etc attract and disperse current best. so add one at the top, and dangle them in the water from your chain(s).

but the best disperser is the engine and good old prop shaft (and lovely bronze prop), so really your chains should lead there on their way to the water.

also its about taking the leccy away from other objects of value - so you should also lead conductors to (and from) metal boxes around important objects - VHF, crew quarters, your dubious video collection etc

what do you think?
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Old 26-01-2013, 07:54   #34
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Re: Simple Lightning Protection Idea?

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Cats are supposed to be struck 2x as much as monohulls so I installed this lighting wire with fixtures and attached it to the base of my mast . I fit it into a garden hose then dropped it directly down & out a drain hole in the anchor locker without any bends - Hoping it will help if ever struck- stays out full time when sailing- cost about- $35usd & 1/2 hour of time- not sure if it help, but atleast its a try?
Its a good start, but you need about 1 square foot of surface area in the water.

As for frequency of cats getting struck more, the theory is that its because they're usually on an outer end face dock, or on mooring, as opposed to inner slip. Underway its all probably as wash.
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Old 27-01-2013, 05:26   #35
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Re: Simple Lightning Protection Idea?

my tuppence on the 'cat frequency theory' -

1 lightning likes a route to earth. the classic - and ideal - model is a conical faraday cage, i.e. a mast with steel shrouds, which conduct the lightning to earth (i.e. water!), missing the boat and its occupants and electronics. obviously the beauty of your device is that it bridges the deck/chainplate-to-water gap and thus speeds the lighting on its way to the ocean. i.e. lightning is seeking earth, not your boat.

2 but...to the cat point: getting struck more frequently must be a function of the greater availability of an earth. i assume that a cat with a broader spread of wetted area must fit the bill!

3 but the key is the definition of 'struck'. A: lightning strikes the mast, heads down the shrouds, stops at the boat and smashes everything . OR B: as above, but it finds it way down the 'faraday cage' and via chainpaltes/ devices to the earth/water, causing no damage.

if the assumed definition is 'A', then my theory at '2' above is probably correct. definition B would imply that the hulls / twin engines, and more dumpy faraday cage profile (greater spread of shrouds) conduct to earth/water more efficiently. [you could of course argue in the case of A that a dumpy faraday profile - and thinner shrouds because of the more obtuse angles of support) is a less efficient conductor than a mono hull's. thus the greater 'strike'].

the best advice i have heard is to connect a copper or brass thick strip from the mast foot to the engine, which then conducts the lightning to the bronze prop via the shaft. seems simple!

a bonus would be a bronze dome at the masthead, and the same inverted at the water end of your bronze strip, instead of the prop route.

remember, you can have millions of volts running thru you, and so long as they don't mistake you for an earth you are ok. incredible but true. the problem is if the volts decide you are their earth and decide to dissipate thru you. RIP.

the best example is of the proverbial crane driver whose jib strikes and rests on a power line. no problem. he is untouched. the electricity heads throughout the attractive metal of the crane and heads for earth - literally. how does he know of the problem? the smell of burning rubber. the volts have made it to the tyres' metal reinforcements and are frustrated bu the rubber which won't let them move on to earth. RIP tyres.

so how does he escape? theres a good answer A and a bad answer B

A: he opens the door of the cab, forms himself into a ball shape, and JUMPS away so he doesn't bridge between the cab and earth. no problem

B: he gets out and steps down from the cab holding the handle . RIP.

I suppose the above shows that thin rubber soles on ones shoes are more trouble than they are worth, as you will fry. very thick rubber soles are good, as they deter attempts to get thru as the lightning goes after easier prey.

but of course the easiest solution is to provide easier prey by providing an alternative route. (unless you like 8in stack sole boating shoes....)

good luck
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Old 27-01-2013, 11:18   #36
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Re: Simple Lightning Protection Idea?

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3. Lightning takes the path of least resistance to ground - myth. Lightning takes ALL paths to ground in strict accordance with the known rules of current flow. That tells us that the majority of the current flows through the path of least resistance but it also tells us that some current will flow in all parallel paths.
Imho, a more accurate statement would be,
"Lightning takes paths to neutralize the charge", for instance, cloud to cloud discharges.

The thruhulls being blown out comes not from them being melted, but the water below them being instantly turned to steam and the resulting explosion's pressure wave physically blowing hole(s) in the boat.

A quick search for lightning blowing out thruhull finds lots of boating forums with testimonies.
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Old 27-01-2013, 16:11   #37
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Re: Simple Lightning Protection Idea?

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Imho, a more accurate statement would be,
"Lightning takes paths to neutralize the charge", for instance, cloud to cloud discharges....................
Fair point ; thanks
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Old 27-01-2013, 17:12   #38
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Re: Simple Lightning Protection Idea?

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I believe a strike is initiated by a streamer coming up from the earth, this is supported by research done at the U of Fl. I isolate my boats from ground to prevent the relatively low potential streamer from originating at my location. Once a strike begins it can and will go everywhere there is the remotest path to ground. Ionized air is a good conductor. You can not contain the energy of a lightning strike in a wire conductor. In over 25 yrs in Fl I have never been directly or indirectly hit. My boat has been within less than 100 ft of telephone poles, which are shorter than my mast, that have been struck on several occasions over that time, close enough for the RF to fry autopilots, VHF's and GPS receivers.It seems there are no guarantees with lightning but these are my thoughts. Dave
Interesting comments.
Has anyone had experience with a lightning strike at sea? that is, not in a marina or at anchor?
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Old 27-01-2013, 17:51   #39
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Re: Simple Lightning Protection Idea?

Hi all, Candlewin, our 48 LOD Herrshoff was struck by lightening while anchored in Kaneohe Bay,Ha the night before our departure for Canada.Wehad an aluminum rod at the masthead,sailtrack bonded with jumpers across the joins in the track all the way to the butt where I had a heavy copper cable attached to the lead keel. I also tied all the stanchions, bimini etc to the same mass. We took a direct hit, deafening inside, with a great flash of light and the smell of ozone. Amazingly, very little damage, only the vhf out of several thousands of dollars of gear. I remember that the Satnav came on by tself and warned of a power failure. Radar, solar panels everything was okay.I noticed later that wherever the copper jumpers joined the sailtrack lengths, it burned the varnish from the wood spars. I attribute that to having a very direct low resistant path to ground. I did quite a lot of research before the install and read that throwing cables/chain from the shrouds is not really very effecftive as stainless is a poor conductor compared to copper and then the poor connections from the shroud to the water. I have heard that the stainless can glow like a toaster with the resistance.
As for sending all the juice through the engine,out the shaft to the water, think of the mainbearings and what a million or two volts would do.
Interestingly, Candlewin was struck again off New York this past year, well offshore, with more dramatic effects. all the electronics fried but not sure if the new owner kpt up the lightening protection.
cheerio, Greg Janes
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Old 27-01-2013, 17:54   #40
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Re: Simple Lightning Protection Idea?

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Lighting protection. Now more relevant than ever:
Lightning Strikes Man's Scrotum
so from now on men, whenever we're caught in an electrical storm; the sooner you rip off your pants, the better! Gotta beware of that durned zipper!
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Old 08-03-2013, 23:19   #41
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Re: Simple Lightning Protection Idea?

I know that this post was started a while ago and I'm reluctant to start new one but I'm curious: how many cruising boats out there have a Lightning Protection System that somewhat resembles what the ABYC describes? If there are no guarantees that even a to-the-letter LPS will prevent damage to a boat, it's crew or electronics, how worthwhile is it to even install?

We're about to head to Indonesia where we hear there are frequent thunderstorms and squalls with lightning. The previous owner left on board some heavy clamps that have about 50' of wide copper webbing attached to them. I presume that he attached these to the shrouds (mast?) and threw the copper webbing into the water when lightning approached. Based on what I've read, this is better than nothing but possibly ineffective. If I were to attach a 4AWG cable to the mast, I still don't know how I'd attach the other end to a keel bolt - a stainless steel hose clamp? I suppose I could try to drill a shallow hole in the end of the keel bolt and the tap it but that sounds easier said than done.

Any ideas?
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Old 08-03-2013, 23:49   #42
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Re: Simple Lightning Protection Idea?

Wouldn't you be better to follow the theory of dissapating energy out of something sacrificial rather than purposely setting your keel bolt as the target.

I think someone said you need a sq foot of surface area so maybe dangle a Dynaplate off a copper cable when needed? I think Ram put his in some garden hose maybe to stop impacting his topsides, i might be wrong?

Cheers
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Old 10-03-2013, 15:30   #43
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Re: Simple Lightning Protection Idea?

I've got a SS L-shape plate attached to the keel, secured by a keel bolt, and heavy wiring from fore/aft/side chain plates attached to the plate. I gotta believe the hardest part is routing wires and accessing chain plate bolts. Mine was done by manufacturer.
The keel bolt (mine are huge, 1"? can handle the current, the standing rigging is another story, I know someone who was hit and had to replace the rigging, and the electronics, etc.
Tom
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Old 16-03-2013, 07:57   #44
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Re: Simple Lightning Protection Idea?

hello, everyone! this has always been an interesting subject....mostly because it doesn't seem to have any solid answers. if you ask 10 people, all of whom are smart and experienced, you get 10 different answers. at least that's what it seems like to me. one thing that has always bothered me is that, with a good grounding system, it seems to me that you are "inviting" a strike by presenting the highest ground in the area.......what is the current (pun) thinking on the subject??? thanks Ralph
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Old 16-03-2013, 09:56   #45
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Re: Simple Lightning Protection Idea?

Ralph, I think everyone will agree that lightning is unpredictable. Beyond that you won't find much agreement. Everyone selling a product or consulting services claims to have scientific expertise to back up what they say. But the facts speak for themselves, so look toward historical information and try to determine statistical degrees of safety from what you find. Here's a good article citing insurance claims from BoatUS: BoatUS.com - Seaworthy Magazine

BTW one statistic in that article is that multihulls are struck about twice as often as monohulls. Although they offer a theory about why, I don't think that's the whole story.... I think multihulls are struck more often because they're more likely to be on an anchor or mooring, and if at a dock they're more likely to be at an outer face pier. It would be interesting if they offered a statistic on boats on moorings vs. those at a dock when stuck. That would answer my theory.
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