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Old 17-10-2016, 06:52   #16
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Re: Lightning Strike! Whats the likely damage and preventive measures.

QEC sadly. Been living in aussie for 30 yrs, moving to Bay of lslands when i finally sail home.
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Old 17-10-2016, 08:02   #17
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Re: Lightning Strike! Whats the likely damage and preventive measures.

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Excellent presentation...
Yes, excellent ➥ Science & Technology
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Old 17-10-2016, 08:22   #18
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Yes, excellent ➥ Science & Technology
Select relevant paragraphs.. copy and paste..
Sometimes just a link is not satisfaction enough..
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Old 17-10-2016, 08:29   #19
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Re: Lightning Strike! Whats the likely damage and preventive measures.

i sailed thru the stuff for a near year--in a sloop with aluminum mast and no lightning "protection"-- no issue. scary, but nonissue.
live and cruise tropics with lightning around-- in a formosa--nothing-- in la cruz got to witness a catamaran being hit--was spectacular. yup. it was "protected"--niiiice green flash.
there was a boat docked across a channel/inlet from the dock used by the man i sailed that near year with--it was a beneteau 55 ft-- got hit not once, but a second time 4 yrs later and sunk.oops... so much for not hitting 2 times in exact same place---it was overprotected by a nasa scientist whose over protection n early cost his house second time.
ok that was enough for me--as i was a n ear hit at age 3.5, i figger, as lightning DOES strike 2 times same place that i best not be calling it out. so--me-- rubber shoes, rubber hat, wood wheel, wood masts and short er ones as i sail a ketch, and my on board cat.
now--cats, as in felines, have never been recorded as hit by lightning-- so it is most important to have that item on board whether stuffed or real.
yup--makes as much sense as getting all riled up about a random occurrence.
a friend cruising was also hit in la cruz-- was a tiny pinhole burn in electrical panel, and the hit was to the WIFI ANTENNA!!!!!! h ah ah aha ha SO--unplug your wifi antenna in a storm.
there is a fact you can quote--no two strikes are the same.
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Old 17-10-2016, 15:37   #20
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Re: Lightning Strike! Whats the likely damage and preventive measures.

Well, at least its good to know lightening wont strike me twice
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Old 17-10-2016, 15:44   #21
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Re: Lightning Strike! Whats the likely damage and preventive measures.

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Well, at least its good to know lightening wont strike me twice

lightning WILL strike 2 times. in slidell louisiana the same boat was hit at the same dock 2 times in 4 yrs. yes lightning DOES strike twice. mebbe not in same storm, but i would not place money on that.
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Old 17-10-2016, 15:49   #22
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Re: Lightning Strike! Whats the likely damage and preventive measures.

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there was a boat docked across a channel/inlet from the dock used by the man i sailed that near year with--it was a beneteau 55 ft-- got hit not once, but a second time 4 yrs later and sunk.oops... so much for not hitting 2 times in exact same place---it was overprotected by a nasa scientist whose over protection n early cost his house second time.

a friend cruising was also hit in la cruz-- was a tiny pinhole burn in electrical panel, and the hit was to the WIFI ANTENNA!!!!!! h ah ah aha ha SO--unplug your wifi antenna in a storm.
there is a fact you can quote--no two strikes are the same.
Common thread here Zee - tall spire & good grounding will attract the strike. (55 Bene has a tall mast, and the wifi antenna well grounded.)
Makes sense to me.
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Old 17-10-2016, 15:53   #23
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Re: Lightning Strike! Whats the likely damage and preventive measures.

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Common thread here Zee - tall spire & good grounding will attract the strike. (55 Bene has a tall mast, and the wifi antenna well grounded.)
Makes sense to me.
This is the theory that I have been evolving. Electricity in general seeks the path of least resistance so why would lightening not do the same. So the boat with a combination of the best ground IE low resistance path to the ocean AND the highest mast will be the one most likely to get hit.

No evidence or data to back this, just a theory or maybe just a WAG.
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Old 20-10-2016, 19:35   #24
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Re: Lightning Strike! Whats the likely damage and preventive measures.

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This is the theory that I have been evolving. Electricity in general seeks the path of least resistance so why would lightening not do the same. So the boat with a combination of the best ground IE low resistance path to the ocean AND the highest mast will be the one most likely to get hit.

No evidence or data to back this, just a theory or maybe just a WAG.

problem with lightning is the extreme high voltage....

air is the best insulator out.... lightning can blast through kilometers of it.

the resistance of a few kilometers of air is effectively infinite, the resistance between various bits of your boat will be measured in single ohms through to several million ohms. so comparatively nothing on your boat has any effective resistance to lightning - it will do what it wants and choose its own path. yes, putting a large conductor as high as possible with a direct path to ground may help.... but its insulation to the boat may melt and let the lightning go elsewhere..... best to do the best we can and see what nature chooses to do.

I have seen fist size holes blown through composite panels where there was clearly (to people) a better lower resistance path for the lightning....

from memory, if you want to be best protected from lightning, you need to have it hit something else not physically cor electrically connected to what you want to protect..... even then the EMP from a close strike can kill electronics that have been unplugged from everything.... someone earlier mentioned Faraday cages - that would surely help.

lightning is wierd, it can strike people and let them live, yet it can strike the ground 10 feet away and still kill you.....
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Old 21-10-2016, 05:09   #25
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Re: Lightning Strike! Whats the likely damage and preventive measures.

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problem with lightning is the extreme high voltage....

air is the best insulator out.... lightning can blast through kilometers of it.

the resistance of a few kilometers of air is effectively infinite, the resistance between various bits of your boat will be measured in single ohms through to several million ohms. so comparatively nothing on your boat has any effective resistance to lightning - it will do what it wants and choose its own path. yes, putting a large conductor as high as possible with a direct path to ground may help.... but its insulation to the boat may melt and let the lightning go elsewhere..... best to do the best we can and see what nature chooses to do.

I have seen fist size holes blown through composite panels where there was clearly (to people) a better lower resistance path for the lightning....

from memory, if you want to be best protected from lightning, you need to have it hit something else not physically cor electrically connected to what you want to protect..... even then the EMP from a close strike can kill electronics that have been unplugged from everything.... someone earlier mentioned Faraday cages - that would surely help.

lightning is wierd, it can strike people and let them live, yet it can strike the ground 10 feet away and still kill you.....
All very true especially the point "lightening is weird". Agree that there is nothing anyone can do to guarantee protection from a lightening strike but I think there are some things one can do that might slightly encourage lightening to pass through with less damage or discourage lightening from striking your boat instead of another. When I was studying EE at UF I read some of the research by Martin Uman, arguably one of the foremost lightening experts in the world, and attended one of his seminars. Bottom line, my take was lightening is weird and unpredictable and not fully understood but there are some things one can do to improve the odds. Some things that might dramatically reduce strike potential or damage to a structure but were very expensive and not feasible for a boat.

I haven't had lightening strike my boat but I did lose two pine trees in my yard. They were about 20' apart and were hit about a year apart in two separate incidents. My house is downhill and lower than all the other houses in my little neighborhood. Many of the trees in the other yards are much higher than the pines that were hit in my yard, but they are mostly hardwoods. I read that pine trees (like catamarans) are struck much more often than hardwoods (or monohulls). My house also borders a creek so the roots of my pines are in much moister soil than than trees higher up the hill (hill being a relative term since I am in Florida) and farther from water. All indicators are that my pines are better grounded than the other trees nearby that were not hit.

Regarding protecting electronics using a Faraday cage, I haven't read any definitive data or research on how effective this may be but would certainly try it if (when) at risk of a strike. I have read of one case where a cruiser stored a spare GPS inside the stove also wrapped in foil that was fried when lightening struck his boat, but many more cases of electronics that survived in the same arrangement.

I guess the only sure solution is to cruise where there is no lightening.
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Old 21-10-2016, 05:39   #26
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Re: Lightning Strike! Whats the likely damage and preventive measures.

Skipmac - it may be that I should have worded better... I didn't mean to suggest we shouldn't at least try to have some form of reasonable lightning protection - I was more trying to point out that there are no guarantees
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Old 21-10-2016, 06:04   #27
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Re: Lightning Strike! Whats the likely damage and preventive measures.

We were struck earlier this year. It killed everything that was connected to a piece of wire, yes including the light bulbs.

I'm convinced there was nothing I could have done to help, except removing electronics. The lighting took the path of least resistance, WHICH WAS ALL PATHS.

We lost everything that was connected, anything not plugged in survived (no they were not in the oven). After replacing everything, I disassembled the dead electronics. Even low draw items connected only to the NMEA network had extensive damage inside (chips blown up).

Now when lightening threatens, we unplug EVERYTHING that can be unplugged.
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Old 21-10-2016, 06:47   #28
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Re: Lightning Strike! Whats the likely damage and preventive measures.

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Skipmac - it may be that I should have worded better... I didn't mean to suggest we shouldn't at least try to have some form of reasonable lightning protection - I was more trying to point out that there are no guarantees
And perhaps I should have worded better as I did understand you weren't suggesting do nothing but pointing out that no matter what you do to guard against it, lightening can and will strike and cause catastrophic damage, or not, on a very unpredictable and seemingly random basis.

One of the frustrating things about boating for me as no amount of preparation or planning can do much to protect you from the potential of strike and damage.
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Old 21-10-2016, 07:09   #29
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Re: Lightning Strike! Whats the likely damage and preventive measures.

The height of the mast and its sharpness will influence whether you are struck, but your grounding will not, because it's a static charge. What grounding will influence is the route(s) the strike takes when it becomes conductive. Unfortunately, the voltage and the amperage involved is so massive that multiple routes through anything conductive (your antennas, wiring, and standing rigging) and some things non-conductive (not even fiberglass is an adequate insulator) are likely, and everything may be fried. Giving the strike a good and damned big route to ground will help, but will not guarantee protection.
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Old 21-10-2016, 08:39   #30
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Re: Lightning Strike! Whats the likely damage and preventive measures.

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When Benjamin Franklin invented the lightning rod in 1750, he noted that it could also be used to protect ships. It was not long before the first ships were to benefit from his ideas.* In the late 18th century the sailing warships of the British navy were fitted with lengths of anchor chain to prevent their wooden masts from splintering when struck by lightning.* Franklin himself was unsure of the actual mechanism, thinking initially that a pointed rod would discharge the thunderstorm "for if there be a rod sharpened ... the electrical fire would be drawn out of a cloud" but five years later covering all bases by adding "pointed rods would either* prevent a stroke or would conduct it so that the building should suffer no damage".** For whatever reason, this technology worked.* The discharge physics of the* lightning strike to ground would not be well understood until research done in South Africa in the 1930's and later.
In the intervening centuries scientific opinion has come down squarely on the side of Franklin's last opinion - that a lightning rod protects a building by offering a suitable path for the current to flow.* Still, modern day refinements for marine protection somewhat mirror the historical record.* Although a code developed by ABYC definitely improves lightning safety, research continues into the underlying science.* In* a paper published by IEEE (the Institute of Electrical and Electronic Engineers) in 1991, Ewen Thomson of the University of Florida tested this code by applying the traditional science used in lightning protection systems for ground installations.* The traditional science, reflected in terms such as "ground resistance" and "step potentials" models voltage gradients as a consequence of current flow in the ground (or water). Thomson concluded that key changes were needed. While some changes were trivial to implement, such as upgrading down conductors from #8 gauge copper to #4 gauge copper, others were highly impractical.* In particular, Thomson noted that hull damage to sailboats struck in fresh water was so extensive, even when the boat had a good connection to the keel, that multiple grounding surfaces were needed over an extensive underwater area, a requirement is very difficult to fulfill in practice.
Of even more concern were some types of boat lightning damage that were impossible to explain with the traditional scientific model. In the light of these inconsistencies, Dr. Thomson concluded, in a yet unpublished study, that key assumptions in the traditional model were invalid* Removing these assumptions and reinterpreting the fundamental science has resulted in a new model that enabled innovative technology to be developed to overcome the above practical limitations.* This technology is now covered by a* patent issued by the University of Florida* and licensed solely to Marine Lightning Protection Inc.
Attachment
Since there is no scientifically proven method to repel it, the fundamental problem in yacht lightning protection is how to deal with lightning when it strikes.* Where the lightning channel attaches to a boat is determined by the geometry of topside conductors on the boat and the location of the downward-going stepped leader relative to the boat.* For example, if the stepped leader is heading for the water behind the boat, aft conductors are more likely to be struck.* In general, the taller the conductor, the higher the probability that its upward streamer will be the one that connects with the stepped leader, thereby completing the ground channel for the lightning. The conductor in the lightning protection system intended to make this connection is termed the air terminal, or, more commonly, the lightning rod.* In this respect, research reported by Dr. Charles Moore and associates in New Mexico only two years ago finally resolved that blunt lightning rods are actually more effective than the traditional sharp pointed rods. The tendency of a tall conductor to attract the lightning strike, by preferentially launching the final connecting streamer, has resulted in the idea of a "cone of protection".* This somewhat flawed idea holds that a vertical conductor forms an effective cone of protection, the apex of the 90 degree cone being at the top of the conductor, and protects the circular area of the cone's base. The idea is flawed in that a vertical conductor does not eliminate the electric field on the ground within this "protected" circular area.* Any conductors inside the area, people included, may give rise to upward streamers if this electric field reaches breakdown strength.* A better arrangement is to have conductors arranged around the area to be protected, or, better yet, forming an umbrella overhead, where the outer edges of the umbrella are connected to down conductors leading towards the water.
Hence the major concern regarding the lightning attachment is to ensure that the lightning attaches to, and causes current to flow in, only an air terminal, or other termination conductors, rather than more vulnerable conductors such as crew members, electronics, etc.
Charge dissipation into the water
Fiberglass is such a good insulator that it is used to make insulators for high voltage installations.* Nevertheless, the lightning voltage is more than enough to cause electrical breakdown through a fiberglass hull if no alternative path is provided, and frequently even if one is.* Each penetration leaves a charred hole and much more extensive internal damage.* Grounding conductors (electrodes) are intended to form a bridge into the water to eliminate this hull damage.* However, a single ground plate is inadequate to prevent sideflashes, necessitating multiple interconnected conductors.* These cause a whole new set of problems:
accelerated galvanic corrosion or loss of sacrificial zinc's;
electrolytic erosion in marinas with ground currents leakage;
many mounting bolts and hull penetrations, each one raising the risk of water seepage;
additional drag since plates should have exposed edges.
Through-hull transducers, fittings, and all immersed metal, including outboard drives, also inadvertently act as lightning grounds.* A typical scenario for an ungrounded smaller powerboat, such as a 20' fisherman, is for lightning to attach to the VHF antenna (vaporizing it), spark through the electronics panel (destroying all electronics), travel* into the battery ground or control cables into the outboard solid state ignition (rendering it inoperable), and then spark into the water through the drive unit. Any transducer such as a knotmeter is also likely to be blown out, possibly leaving a hole where it was mounted.* This scenario assumes that no crew member is unlucky enough to be bridging a gap along the way.
Carbon deposits after lightning strikes* trace out the paths followed by sparks forming from immersed conductors, both those grounded and those* that are isolated.* A detailed discussion of this effect is given in a *letter* published in Professional Boatbuilder.* Briefly, charge accumulates on all conductors on the boat,* even when current is flowing into the water.* The charge density is largest close to the water and on sharp corners and edges of conductors, which is thus where sparks are most likely to start.* So sharp corners are highly desirable on the outside of grounding plates and are recommended in most standards.* As well as initiating current flow, spark formation reduces the grounding resistance, thereby lowering the voltage of the whole protection system.* There is experimental evidence that the eventual effective area of the sparks formed from at the water surface above-water fittings may be hundreds or thousands of square feet.* See a brief discussion of this mechanism below.
In summary, the major problem with charge dissipation into the water is how to provide the appropriate number and distribution of grounding conductors, to eliminate sideflashes,* while minimizing the corrosive effects of multiple immersed conductors that are bonded together.

Man that was difficult to read.

If I may suggest to all who post big and wordy stuff to open it up.

Start each sentence at the left and paragraph as much as possible.

And try to keep sentences as short as you can.

Good info though.
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