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post #1 of 38 Old 10-24-2012 Thread Starter
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Lightning Protection & Risk

I just did a search prior to posting and have a few questions.

I just bought a boat (Islander 37, MS) and will have it home FL by Wed. (31 Oct.).

I have a lot of work, nothing major (hope not) and should be ready to go in April of 2013.

When I haul it to Panama City, FL for launch, the mast will be put back up and re-riged, etc. . *** Now, in the mean time, should I be looking into a added option for dealing with Lighting Stike !

I read in the other threads... the listed info. about Lighting Strikes. Currently, the boat makers ensure the sailboats are grounded down through the mast and other grounding provisions are made through out the boat. Now, my Islander (I-37) 37 is a older (1970) boat. I wonder if they (Islander) were that heads up at this time (1970's). Also, I understand that all your electronics are normally fried .. if struck. Is it smart to disconnect them when the boat is docked or take them with you, also to advoid theft when you leave the boat ?

What is a recommended way to Add to your -- Lighting Proctection. One person, said he'd go to the forward berth and take a nap (while he waited the storm out) also, he'd run a heavy gage wire into the water to >> add in >> directing the worst of the lighting force into the water.

Ok, what can you add, just a new guy and lot's of questions.

Closing question... how can you find previous owners through boat registration numbers ?

Thanks in Advance

Avery (HighFly27)
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post #2 of 38 Old 10-24-2012
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re: Lightning Protection & Risk

If your boat is near other sailboats in its slip, chances are you will not get hit although somebody has a good chance of being hit. Try to be one of the lower masts between higher ones.
By itself with no other tall objects nearby, your chances of being hit are good, especially in FL.
I would not disconnect the VHF due to forgetting to reconnect it later but would disconnect other stuff.
At dock, I'd avoid trying to make any lightning ground as you are most likely to cause a corrosion situation.
At sea, i would at minimum get a 2' X 2' copper plate with #2 tinned stranded wire bolted to it. During a storm, lower it over the side and attach the other end to your mast with only gentle bends in the wire. Mine has line attached to the corners for hanging it from the lifelines.
Do not rely on a sintered plate such as a Dynaplate as a lightning ground, not gonna work.
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post #3 of 38 Old 10-24-2012
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re: Lightning Protection & Risk

The odds of getting hit by lightening are not cumulative. When the boat was new 42 years ago the odds were the same as now. Don't worry about it.

Really - but that said, look both ways before you cross the street.

Rik

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post #4 of 38 Old 10-24-2012
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re: Lightning Protection & Risk

Quote:
your boat is near other sailboats in its slip, chances are you will not get hit although somebody has a good chance of being hit. Try to be one of the lower masts between higher ones.
False

Quote:
By itself with no other tall objects nearby, your chances of being hit are good, especially in FL.
Florida and Chespaeake are the two areas with the most boat strikes by lightning

Quote:
I would not disconnect the VHF due to forgetting to reconnect it later but would disconnect other stuff
.

Waste of time, wont make any difference

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At dock, I'd avoid trying to make any lightning ground as you are most likely to cause a corrosion situation.
And it wont make and difference

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At sea, i would at minimum get a 2' X 2' copper plate with #2 tinned stranded wire bolted to it. During a storm, lower it over the side and attach the other end to your mast with only gentle bends in the wire. Mine has line attached to the corners for hanging it from the lifelines._ Frogwatch
.
Can you show me empirical data that this works

Highfly,

The above post by Frogwatch is wishfull thinking. There is virtually nothing you can do except ground you boat so if/ when you get hit the lightning has an exit stratagey instedy of blowing holes througheverything trying to leave your boat

Our boat was struck by lightning this summer anchored/ morred within 500 ft off 900 other masts in Back Creek , Annapolis. We were not the tallest mast at 53 ft. The lightning actually struck
a water tower 100 ft away and came to the boat through the water, We had cablkes in the water as above and they did nothing

The lightning was completely arbitrary what it destroyed. It took out some equipment tuned on and left alone others right next to it which were on. It took out equipment turned off and let alone other equipment turned off. It burned a Yanmar angine panel- off, A chartplotter-off, some white LED lights- off , and a shorepower charger off. Ignored TV anantaee, radar and antanaee and handheld.

We were sitting in the cabin when the big flash occured.

Best thing thing you can do is have good insurance and try not to be out in the open with the boat. All else are fairy tales

Dave
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post #5 of 38 Old 10-24-2012
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re: Lightning Protection & Risk

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Originally Posted by chef2sail View Post
Highfly,

The above post by Frogwatch is wishfull thinking. There is virtually nothing you can do except ground you boat so if/ when you get hit the lightning has an exit stratagey instedy of blowing holes througheverything trying to leave your boat

Our boat was struck by lightning this summer anchored/ morred within 500 ft off 900 other masts in Back Creek , Annapolis. We were not the tallest mast at 53 ft. The lightning actually struck
a water tower 100 ft away and came to the boat through the water, We had cablkes in the water as above and they did nothing

The lightning was completely arbitrary what it destroyed. It took out some equipment tuned on and left alone others right next to it which were on. It took out equipment turned off and let alone other equipment turned off. It burned a Yanmar angine panel- off, A chartplotter-off, some white LED lights- off , and a shorepower charger off. Ignored TV anantaee, radar and antanaee and handheld.

We were sitting in the cabin when the big flash occured.

Best thing thing you can do is have good insurance and try not to be out in the open with the boat. All else are fairy tales

Dave
Sorry to hear you got wiped out like that, but you'll find that it isn't "completely arbitrary" what it destroyed and there are a few things you can do to minimise the damage. 'On' or 'off' makes no difference, but complete disconnection of all wiring to some vital piece of kit can help.

First off, basically speaking, lightning takes the path of least resistance to ground. Being 500ft away is no protection from a direct strike, nor is being anywhere near another metal object in the water, but being rafted up to someone with a higher mast (preferably with someone else with a higher mast on the other side) might be.

Lightning system designers sometimes use a technique called "cone of protection" to determine the risk of a hit. The "cone" radiates outwards and downwards from the top. If the top of your mast is within someone else's cone of protection, you're being protected by them. How far depends on the hight of the mast, but it won't extend away from most boats by more than a few meters either side. It's even possible for a VHF antenna on the back of a boat to get hit rather than the mast itself, simply because it is outside the "cone of protection" of the mast.

It sounds like you copped what's known as "earth potential rise". Basically, lightning has such a high voltage that, for a brief moment in time, the water is isn't conducting and the side of the boat nearest the tower is at a higher voltage than the water on the other side. The cables you had in the water would have allowed current to flow into your boat, through whatever else was connected to them (via the earthing system) and then back into the water on the other side! Nasty.. In that particular case, not being grounded at all would possibly have meant less damage.

A few things you can do if you're in a high lightning risk area:
1. Yes, definitely ground your boat so if/when you get hit the lightning has an exit strategy instead of blowing holes in your boat.
2. Make sure the lightning ground system is not connected to or run in close proximity to the boats electrical earthing system or the RF ground (if you have one).
3. Make sure all your electrical earthing is to a single-point ground - usually on the engine... or if it's to the switchboard, that you've got a pretty decent-sized conductor for the earth to the engine.
4. Don't bond all your thru-hulls, etc. together or to anything.
5. Carry a liferaft and a good insurance policy... and hope you never get hit!
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Last edited by Classic30; 10-24-2012 at 08:29 PM.
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post #6 of 38 Old 10-24-2012
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re: Lightning Protection & Risk

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Originally Posted by rikhall View Post
The odds of getting hit by lightening are not cumulative. When the boat was new 42 years ago the odds were the same as now. Don't worry about it.

Really - but that said, look both ways before you cross the street.

Rik
Yes, while the odds aren't likely, what would be the purpose of sailing during such a terrible storm?
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post #7 of 38 Old 10-24-2012
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re: Lightning Protection & Risk

I've inspected a number of lightning strikes (in fresh water ....very different than salt). I've ssen the copper plates hanging over the side, ion disipators and sintered bronze ground plates with No2 bonded to masts and standing rigging. I have seen lightning hit the water 20' away from my own boat in open water with no other targets around. I know that their are laws of physics involved but I also know that even the "gurus" ( I've taken courses fro some well known ones) will admit that we do not know enough about this pheomenon to predict, control or assuage it.

I have come to a simple conclusion .... 60,000,000 volts travelling at near the speed of light and discharging 60,000 amps is going to go wherever the hell it wants.

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post #8 of 38 Old 10-24-2012
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re: Lightning Protection & Risk

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I have come to a simple conclusion .... 60,000,000 volts travelling at near the speed of light and discharging 60,000 amps is going to go wherever the hell it wants.
Pretty much..

All the more reason to get you (and any fancy electronics you happen to value) as far away from it as possible!
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post #9 of 38 Old 10-24-2012
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re: Lightning Protection & Risk

I stand by what I said as I do know a thang or two bout high voltage high current discharges.

Being around other boats masts DOES reduce your probability of being hit.

Having a low resistance path to ground will help when you are hit hence my ground plate. Do you really want mega-amps going thru your thru hulls?

Completely disconnecting your electronics really will protect them more than leaving em connected.

Regardless of what lightning does, it is always in accord with laws of physics. Often the rationale of where lightning hits is not obvious but can generally be explained.

I have a near lifetime of doing stuff with HV discharges and have a very healthy regard for lightning.

Credentials: MS Physics specialty was electrical discharges for electrical charging of very fine particles.
MSEE specialty was "dusty plasmas"
Years of work on very large pulse HV High amp discharges

Having lightning hit 20' from your mast should not surprise you at all. completely in accord with well known properties.

Ball lightning, that is another story.
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post #10 of 38 Old 10-24-2012
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re: Lightning Protection & Risk

By yourself, underneath an active thunderstorm, you stand a reasonable chance of getting hit assuming an average area of said storm and average number of cloud to ground strikes during said storm, I once calculated about a 7% chance of being hit with a 50' mast. Apparently insurance stats agree.
I do not think there is much to be done to prevent a hit. Lightning only "decides" where it will hit when it reaches about 200' above ground (The return stroke). Best to minimize damage after the hit. So, conduct as much to the water as you can.
Lightning has lots of High freq components so it wants to travel on surface of stuff, even water so the best ground would float on water and have lots of edges.
Ground to your mast, not to the shrouds.
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