# Being Hit By Lightning - To Ground or Not



## marinedtcomRob (Oct 26, 2005)

So I'll admit I'm a bit paranoid about getting hit by lightning. I've been hit twice, once at Cape Lookout, NC on a Grady-White 23' Gulfstream and the second time at Three Mile Harbor on Eastern Long Island on our Little Harbor 38. In both instances we were around a lot of other boats that had anchored late afternoon, perhaps a little earlier than normal to ride out the night and oncoming squall lines.
<O></O>
On the Little Harbor, we were a sailboat among a lot of other sailboats so that we got hit, well that's the way it goes I suppose. On the Grady, we were surrounded by numerous sailboats. All we had was 15 foot outriggers on the hard top which I had grounded with #4 cable to the engine block. The Grady is a well-made boat but even they do nothing out of the factory regarding lightning grounding. My take is that since I did such a great job grounding I turned us into a really good antenna to "pull down" a strike. When we were hit, my wife and I were standing under the hardtop with the curtains down. Behind us, shards of white hot metal burst onto the deck from the super heated terminal where the # 4 wire connected to the outrigger base. Our loran and depth sounder got fried through the ground wire and transducer presumably, because the power wires were disconnected. Our Icom radio survived intact.
<O></O>
Regarding the strike to the Little Harbor, it is of course a well grounded boat with a bonding system. Even so, as the storm approached I took a battery jumper cable and clipped one end to the base of the port shroud and let the other end dangle in the water. Just after we went to bed I saw and heard that instantaneous "crack" followed by a loud "twang" which I was quite sure was from the sound of the rod rigging (like most things, it has its own unique sound). In the morning when I came up on deck, sure enough, there on the deck lay the 36" whip antenna and part of the base from the top of my mast, having been blown out of its base and bent into a 90 degree angle from being super heated. Where the battery cable had been clipped onto the rigging there was a minor scorch mark (Nitronic rod is pretty tough stuff). Other than my Xantrex Pathmaker being fried (it was the only piece of electronics that's really hard to get at and disconnect) all the electronics were fine as I disconnected everything going to the electronics including grounds this time.​<O></O>
I guess my take at this point, other than the fact that my wife especially hates sailing in lightning, is that I still would rather be well grounded than not as we've had well contained damage each time. I must admit that even with my small sample and relatively small amount of time I get to spend on the water, it does seem to me that being well grounded increases the chances of being hit. It's just that I've heard some really horror stories regarding the damage to boats that are not properly grounded. Does anyone have any experience using one of the lightning / static dissipater products, protecting electronics with a power conditioner, or any other thoughts or experiences with lightning?


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## artbyjody (Jan 4, 2008)

One technique we used in the ole south - that actually works, is taking your cables and doing a loose knot at a point closest to the power source. The knot creates a magnetic field that causes the cable to blow apart there - but doesn't allow the rest of the current to travel any further...That is a very low tech solution for protecting gear. However this is good reading: Link

For most in hull grounding to be effective on a fiberglass boat, one of the techniques was the copper plate running for to aft with additional copper looping from port to starboard to create a Faraday Cage...

There is nothing to prevent a lightening strike - just various techniques to minimize the effect...if your boat is properly grounded, and such...(and seems there are tons of products that promote something that aides etc for it)... none of them are lightening proof...and usually due to the mast and the tallest structure and usually the backstays and forestays are not grounded out to the water - there is only one direct path and that is in the boat and out whatever path your boat has....


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## sailingdog (Mar 19, 2006)

Rob-

The only real way to protect electronics is to disconnect them and store them in a metal box. The voltage surge induced in the wiring is what fries the equipment normally, and not much can prevent that. 

There are basically two schools of thought on lightning grounding and bonding. 

The first is to ground the mast and all large above deck metal objects, like stays, shrouds, stanchions, pulpits and pushpits. This, in theory, should create a region of safety. The grounding system should use a thick ribbon or foil of copper to connect the metal to a grounding plate on the exterior of the keel. 

The second school is to leave the boat completely ungrounded. The reasoning is this... grounded boats tend to get hit more often. So, by leaving the boat entirely ungrounded, you reduce the chance of getting hit. However, there is a downside to this... ungrounded boats generally suffer much more damage when they do get hit. 

So either you ground and increase the risk of getting hit, and minimize the amount of damage a hit will do, or don't ground and minimize the chance of getting hit, but risk far more damage if it happens. 

The static brushes are basically lightning phobe placebo equipment. For those to actually work, they would need a decent path to ground and a solid ground connection... 

Power conditioners don't work, since the lightning power surges can occur in the wiring leading into the equipment, and it doesn't have to be power wiring... the mic cord on a VHF set could fry the electronics if the lightning induced surge is high enough.

As for the Nitronic rod being blow out... not completely surprised given stainless steel's generally high resistance to electricity. It is roughly only 3% as conductive as copper... and as such tends to heat up quite a bit under the very high voltage/amperage of a lightning strike.


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## Stillraining (Jan 11, 2008)

*Saildog*

My boat has a bonding plate on the hull not on the keel but to the left of the shaft tube the hull is only 1/2" thick in that area, It is small maybe 3x8". The engine and chain plates are conected to it, the mast is not. I want to connect the mast also but am concerned about the small size of the bonding plate, the run the wire would take along the bottom inside of the hull and all the keel bolts it would have to pass by? What would you recomend?

Could I Just hook the mast to the first keel bolt?


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## camaraderie (May 22, 2002)

Rob...I've never seen any convincing evidence that any of the masthead products work. Power conditioners that WORK are expensive but may be worthwhile for individual high cost items...SSB's, Plasma TV, PC's etc. if you are in an area that is hit with regular T-storms...(Florida & the Chesapeake come to mind!). I agree with your conclusion that a properly grounded boat is the way to go...and I also like to hang around boats with taller masts (g)
I've never been hit myself...but have been in the company of those that have and these grounded boats had significant damage to electrical components but remained with masts upright and afloat. Meeting those two criterea is sufficient for me...the rest is all insurance!


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## sailingdog (Mar 19, 2006)

Stillraining-

It really depends on what your keelbolts are made of and whether you have an encapsulated keel or not. 

Stainless steel keel bolts are not going to do the job very well. Either is an encapsulated keel. Personally, I wouldn't use a keel as a grounding plate... there are serious possible problems with doing so. 

BTW, A grounding plate should have at least four feet of linear edge to dissipate the charge. The bonding plate you have doesn't sound to be large enough to do a proper job, especially since the mast isn't connected to it.


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## theartfuldodger (Sep 4, 2006)

well I have such a device, as well have boat grounded as well and have to admit that whether its been luck in a storm or the brush on the top of my mast, but touch wood never got struck. Have talked to other sailors on the Ottawa river from the Nepean Yacht club who have also had good safe times in lightening storms, and hench the reason for my brush a top my mast.


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## Wayne25 (Jul 26, 2006)

Dog:

From what I've read, your correct about the 4' of linear edge. Its the edge of the ground plate that discharges the strike to the water. However, the 4' is for salt water. If you sail in fresh water, the number doubles or triples in length.


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## Stillraining (Jan 11, 2008)

*OK , So if*

I was to manufacture a larger plate with larger attachment bolts and backing plate, and attach my main mast to it. The cable I would have to runn would be laying in the bilge for about 20' horazontal. This is my mane concern as everythin I read say's to form as straight a path down to the water as possibal. I dont want current trying to blow a hole in my hull as it runs that 20' to the bonding plate. I will try to post a picture.


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## Stillraining (Jan 11, 2008)

*Here's a picture*

of the bilge that runs from the mast step ( right at the top of the picture is the mast step tunnel )most of the length of the boat ,into the engine compartment to the shaft tube.

You can see the keel bolts there are 18 of them and yes they are SS. 
The bonding plate bolts are barly visibal to the far left edge of the sole hatch cut out on the left side,( second picture ) there is no backing plate, will be changing that!!

Oh by the way another cncern is thoes are my fuel tanks on both sides of the bilge , Im standing on the starboard tank.( Fiberglass )


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## marinedtcomRob (Oct 26, 2005)

*article by Nigle Calder*

There's a very good article on _"Lightning Protection" by Nigel Calder_ that was published in the December / January 2004 issue of *Professional BoatBuilder* magazine. If you want an in depth and up to date (relatively speaking) review on this subject, Calder is, as usual, painstakingly thorough. The article was not available online that I could find but the phone number for the magazine is 207-359-4651. Presumably they sell reprints.


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## sailingdog (Mar 19, 2006)

Stillraining-

You don't want the lightning bonding ribbon to make any sharp bends... and having the grounding plate is as direct a line with the mast is probably the best idea. Having the grounding foil or wire turn will likely lead to lightning sideflashes, and given where your fuel tanks are, that's probably not a good thing.  *Lightning + Fuel = BOOM!!!!*

And as Wayne has pointed out the 4' linear edge figure was for a boat in salt water. If the boat is in fresh or brackish water, it will need more plate edge exposed.

One of the best grounding strips I've seen in a long, long time was a 1/4" thick plate with 15 3/8" x 2" threaded copper studs attached to it, that was 2" wide by six feet long, and embedded in the hull of a boat. The boat was a cold-molded wood and fiberglass/epoxy composite trimaran.


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## TSOJOURNER (Dec 16, 1999)

*Lightning PREVENTION*

We have a 62 ft sailboat with a tall rig. The top of the pigstick is 98 ft above the waterline. When we built the boat in England, we installed two "No Strike" ion dissipating rods. They are "bottle brush" devices that are connected to the Fredrickson sail track. The sail track is connected to the mast step which is connected to a keel bolt with copper tape. The chain plates are also connected to the keel bolt with copper tape.

We have sailed the East coast, from New England to the Chesapeake and in FL and Tampa Bay and have been in and around many thunderstorms and have never been hit. We've had instances of boats very close to us at a pier or at a mooring, with much shorter masts, which have been hit.

Ion dissipators are intended to dissipate or "bleed off" the electrical charge which builds up during a thunder storm before the accumulated charge creates a "leader" to the cloud which channels the high energy strike.

A quick web search found two sites of interest: LEC GLOBAL has lots of engineering information about lightning strike prevention. Their ion charge dissipators are a bit unwieldy for most boats! 

Northsea Navigator's products are almost identical to what we have installed. It was interesting to see their guarantee! I like doing business with a company that puts their money where their mouth is. Their business is PREVENTION of strikes, not minimizing the damage that occurs when struck. It would be interesting to see what their claim history is.

*******************************
Designed for sailboats 25-45ft
Height 14"
Width 3"
Weight 1.5 lbs
$ 285.84
<o =""></o>Lightning Prevention Systems warrants your product or products to be free of defects in workmanship and materials for a period of 7 years from date of purchase. Lightning Prevention Systems also guarantees that, when properly installed, your boat will not experience a direct hit by lightning. This guarantee will be in effect for a period of 5 years from the date of purchase. Should your boat ever be struck, Lightning Prevention Systems will pay up to one thousand dollars of your insurance deductible for the claim submitted for losses or damage caused by that direct strike to your boat. Lightning Prevention Systems will pay five hundred dollars for losses or damage caused by a direct strike of your boat is uninsured. This guarantee is non-transferable and covers units remaining in their original installation location and boat.
**********************************

Our experience says perhaps you CAN prevent strikes.
You need:
- an effective dissipator (or several dissipators) at the masthead,
- a very straight high conductivity path to the water

This installation has worked very well for us. We've been spared hits while very near to us, boats with much shorter rigs were hit, usually on the VHF antenna.

I would have posted the links and photo but I just found out until I've posted 10 posts, I'm prohibited from including links or photos.


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## cspots (Jan 22, 2008)

The definitive answer isn't in for lightning protection on a sailboat. It isn't even clear how all the damage is done by lightning, nor what type of lightning we are trying to protect from. Any time there are many ways to do something, it means that either anything, or nothing works well enough.

The basic concept of a simple lightning rod, with a direct connection to ground, has worked very well for centuries. (Possibly until we started to have phone and electrical wires going into buildings?) Since the early 1800's the British Navy very successfully prevented damage from lightning strikes on wooden sailing ships, with wooden masts by using an iron rod and iron wire from the mast tops to the water. Nobody has proven any benefit over these simple systems, in spite of all the hype of the lightning rod salespeople.

<o>
</o>
Per a report on lightning by BoatUS Seaworthy: "(1) It is better to avoid being struck in the first place, but (2) if your boat does get hit, you will suffer less damage if the strike is grounded as directly as possible." <o></o>
<o> </o>
What I plan to do isn't far fetched, and is relatively simple, and cheap. It may not protect from every type of damage, from every type of lightning, and it may work better with a catamaran.

<o> </o>I want to keep the lightning out of the boat! Give it a simple, direct route to ground, without connections, angles or upward angles, which encourage side deflections. Don't encourage it to hit the mast, and then try to minimize the damage.

Use 4-10 G insulated copper wire, stranded. The size may depend on mast height, and your anxiety level. Run it through and attach it to ½ inch PVC pipe, and hoist it by a halyard (spinnaker, main, spare jib, or topping lift) attached to the PVC. This is to add rigidity (and further insulation where the wire is closest to the mast near the top). The wire is secured inside the pipe with a wad of electrical tape.
The top 2 feet or so of wire should be above the highest antenna, and the top foot of insulation would be removed and these wire strands, above the antennae, could be: 

splayed open,
pointed, or
rounded (preferred)
 In an almost straight run, the wire would stretch from above the mast head, through the bow netting to the water. This is not close to any electronic equipment, or metal. The insulation is removed just above the water, and the wire strands are splayed and run into the water for at least one to three feet, to allow better grounding and dissipation of current. This would be more difficult to set up when sailing, but not impossible. On a monohull, the wire could go over the lifeline, through another piece of PVC pipe. 
<o> </o>
Granted, even 2 G wire wouldn't protect completely from a direct lightning strike, but the goal is to get the lightning out of the boat, not just to give it more benign route through it. Then hopefully the cone (or rolling sphere) of protection will protect the occupants and equipment.


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## TSOJOURNER (Dec 16, 1999)

There are numerous folk medicine cures, but none that are 100% effective. My boat had a well grounded system and was struck by lightening anyway. The strike evaporated my masthead antenna right down to the loading coil, then proceeded down the standing rigging and out the hull mounted grounding plate. The total damage was; the antenna, the masthead tricolor strobe unit and the voltage regulator on the engine generator. Afterwards I added a copper plate attached to a substantial braided conductor which had a very large battery clamp attached. This was clamped to the backstay whenever the boat was on it's mooring or when I was aboard and saw an oncoming storm. As a physicist, my recommendation is to avoid changes in the path of your grounding system. Any deviations represent an increase in inductance and since the voltage developed is L(inductance)x(Di/dt), with Di being very large and the time period dt very short for a stroke of lightening, the backvoltage developed can be enormous and divert the energy to another path.


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## sailingdog (Mar 19, 2006)

I'd be a lot more impressed if they would pay for repairs, rather than just your insurance deductible...which is a cheesy way out, and of absolutely no use to people without comprehensive insurance on their boat. And even worse, they'll pay $1000 if you're insured but only $500 if you're not insured... really nice...  

Of course, the number of boats that are hit is so small that statistically, it is in their favor to pay $1000, since I seriously doubt more than one boat in five that they sell to actually gets hit by lightning....* As long as less than one boat in ten or twenty gets hit... they're going to make a killing... *since they're charging almost $300 for the bottle brush.



ppsavage said:


> .... A quick web search found two sites of interest: LEC GLOBAL has lots of engineering information about lightning strike prevention. Their ion charge dissipators are a bit unwieldy for most boats!
> 
> Northsea Navigator's products are almost identical to what we have installed. It was interesting to see their guarantee! I like doing business with a company that puts their money where their mouth is. Their business is PREVENTION of strikes, not minimizing the damage that occurs when struck. It would be interesting to see what their claim history is.
> 
> ...


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## TSOJOURNER (Dec 16, 1999)

After 2 years of researching this and looking at hundreds of boats this is what I've been able to discern..and this is what I did on my boat.

Forget about where the too small, existing plate is. That plate is likely for grounding the DC system and far too small for this job. Buy a copper plate a minimum of 1/8" thick and 1 square foot in area (thicker and larger are probably better and yes more edge length is better.) You must through bolt the plate to the outside of the hull as close to the mast step as practicle. Access from inside the hull will probably limit where you can place the bolts and will therefore help determine the shape of the plate you need. Use #4AWG (or larger) copper strand wire to connect the mast to the plate. Avoid bends in the wire. Use bronze bolts 3/8" or larger in diameter to secure the plate to the hull and to the cable. You can buy the Bronze bolts, washers and nuts from Lewis marine and other places. You can get the copper plate from several places on the internet such as "onlinemetals.com" It is not that expensive. 
I used .125" thick but would use .25" thick if I did it again. If you would like more details, I'd be glad to help.


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## artbyjody (Jan 4, 2008)

soverel48 said:


> After 2 years of researching this and looking at hundreds of boats this is what I've been able to discern..and this is what I did on my boat.
> 
> Forget about where the too small, existing plate is. That plate is likely for grounding the DC system and far too small for this job. Buy a copper plate a minimum of 1/8" thick and 1 square foot in area (thicker and larger are probably better and yes more edge length is better.) You must through bolt the plate to the outside of the hull as close to the mast step as practicle. Access from inside the hull will probably limit where you can place the bolts and will therefore help determine the shape of the plate you need. Use #4AWG (or larger) copper strand wire to connect the mast to the plate. Avoid bends in the wire. Use bronze bolts 3/8" or larger in diameter to secure the plate to the hull and to the cable. You can buy the Bronze bolts, washers and nuts from Lewis marine and other places. You can get the copper plate from several places on the internet such as "onlinemetals.com" It is not that expensive.
> I used .125" thick but would use .25" thick if I did it again. If you would like more details, I'd be glad to help.


Is it tested by actually being hit by lightening?


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## Classic30 (Aug 29, 2007)

A note on protecting ship-board electronics for the lightning-prone:  

Surge damage can be minimised by installing a surge diverter and virtually eliminated by installing a (more expensive) surge filter.

As the name indicates, a surge diverter is fitted to the +ve and -ve terminals of the equipment you want to protect and basically diverts any power surge to ground (your grounding plate). Good quality ones contain a gas-discharge tube, which provide a high-voltage path to ground and at least one metal-oxide varistor (MOV) between the terminals and earth to limit the maximum voltage on the wire.

A more expensive option is a surge filter, which is fitted in series with the power connection to the electronics and, as well as the above devices, contains a set of inductors and capacitors to prevent any trash on the wires making it to the set. You can buy surge filters for masthead antennas for far less than replacing the radio if you get hit.

As a bare minimum, I'd suggest installing a surge diverter on the radio batteries - for only a few bucks spent at Radio Shack, you might still be able to call the coastguard after the event... of course, both these gadgets must be properly grounded otherwise they won't work...


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## BIRDBATH (Oct 10, 2003)

*Lightning Ground*

This Has Not Been Tested, But If At Anchor In An Electric Storm, I Bend The Storm Anchor Chain Around The Base Of The Mast And Dangle The Anchor Over The Side. It Seems To Me This Would Divert The Strike To The Water And From The Existing Bonding System. The Existing Bonding Wires Are Not Too Heavy (they Are Imbedded In The Fiberglass) And The Grounding Element Consists Of The Shaft And Prop. The Anchor Makes Good Contact With The Water.

In Retrospect, I Should Also Do This At My Slip.


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## artbyjody (Jan 4, 2008)

BIRDBATH said:


> This Has Not Been Tested, But If At Anchor In An Electric Storm, I Bend The Storm Anchor Chain Around The Base Of The Mast And Dangle The Anchor Over The Side. It Seems To Me This Would Divert The Strike To The Water And From The Existing Bonding System. The Existing Bonding Wires Are Not Too Heavy (they Are Imbedded In The Fiberglass) And The Grounding Element Consists Of The Shaft And Prop. The Anchor Makes Good Contact With The Water.
> 
> In Retrospect, I Should Also Do This At My Slip.


Let Us KNow WheN YouR Boat BlOWs UP or you Stand THEiR WEHILE IT HIts...


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## coatiac (Jan 20, 2001)

*Lightning*

My 2 cents as an electrician are that most damage caused by lightning strikes are due to a poor or improperly sized ground path. The best example I can give is when the stike happens to an "ungrounded" mast. Of course there are conductors up there, the mast being the best one, but if it isn't properly grounded, the the strike will usually start with a light or antenna wire, because there is a connection to ground with these circuits. But as soon as the strike is iniated, the small conductor will fail at some point, leaving the strike to find a new path, which then becomes the mast until arriving at the base, where it then jumps to the next closest conductive material. It is the failing of one path, and subsequent jumping to the next path that causes the damage.

Ground your sticks properly, keep the paths as atraight as possible, and keep your connections maintained.


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## chucklesR (Sep 17, 2007)

Copper foil is (I think) the best grounding plate, doesn't need to be thick - hecks it's meant to be blown away. A thin, 3 inch wide or so, 'tape' of foil from bow to stern provides maximum linear footage for charge disapation. Connected to the mast with the heaviest gauge wire you can get to it - the foil only costs a few bucks and can be replaced every bottom job.


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## nwr (Jul 13, 2000)

*lightning dissipator effectiveness*

I installed the Forespar lightning dissipater brush on the mast of my Islander 37 Motor Sailor prior to a transit from New Orleans to Charleston SC via Florida in June 2003. We got caught in Sarasota Bay in the middle of a thunderstorm super cell that had lightning in all quadrants. we anchored and since i hadn't yet put in a grounding system put 2 automobile jumper cables 2AWG wire size with large copper clamps, into the water from the port and stbd main cap shrouds. lightning struck the water less than 100 yards from the boat several times in the next 1/2 hour or so and i could see a bluish ball of ionization glowing from the top of the mast in the gloom. i know we were the tallest thing within 5 miles but even with the grounded shrouds we didn't get hit. after the storm passed we continued on in the ICW and across lake Okeechobee. every night when we anchored i put the jumper clamps on for security and while there were several more storms none were as close aboard as in the Sarasota Bay. On several strikes i could see the steam come up from the water from the strike. it made me a believer. i'll be putting the suppressor/dissipater's on my recently acquired 45 ft ketch at the next haul out. Neal Richardson s/y Black Swan II (Islander 37 Motor Sailor) and S/Y White Magic (ALOA 45)


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## sailingdog (Mar 19, 2006)

NWR-

The 2AWG jumper cables probably did less than zip to ground your boat, given the high resistance of the stainless steel used in shrouds and stays, and the low surface area of the clamping method... it was of almost purely psychological benefit if anything. 

Chuckles-

The grounding strip/plate for a lightning bond system does generally have to be a bit heavier than most foils are. The best ones I've seen have threaded copper studs that go through the hull to the bonding system.


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## chucklesR (Sep 17, 2007)

SD,
Gem's don't come grounded anymore than your Telstar did, I'm still in design mode. 
I'm not wanting to add 100 pounds to my boat as I get 450lbs per hull = 1 inch of immersion, every pound counts. Granted thicker is better long term - I'm figuring I'll replace each bottom paint or if it gets blown away by a strike.

I'll report back when it happens.


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## sailingdog (Mar 19, 2006)

A 1/8" plate of copper that is 2" x 24" isn't all that heavy..  You could install two of them and probably never have to replace them again. Have them installed with five 1/4" x 20 copper studs attached...and you'd be good to go. However, how you get from the mast, to the underwater part of the boat on a catamaran without encouraging sideflashes is a neat trick. 

A trimaran is a bit simpler... and I'm planning on getting a strip made up for my boat.


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## TSOJOURNER (Dec 16, 1999)

Check the web at rule69blog (of course adding the www prefix and the dot com suffix). There are two pictures today of a 30 meter alumninum sloop at the Cat Club Marina in Antigua that was hit by lightning and burned to the waterline. Our boat was tied to the pier immediately in fron of them. I'm sure their mast was higher than ours!


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## TSOJOURNER (Dec 16, 1999)

Can anyone say "snake oil" ?  If any of the methods mentioned/marketed had any empirical data to support their effectiveness in a true scientific method, they would have cornered the market on said devices and insurance companies would give us a break for installing them. The safety recommendations given by knowledgable sailors are still valid if caught in those situations, but some of these antics are as effective as trailing a dead cat over the side. The will of Providence seems to be the ultimate determining factor in a strike. Most of us that actually get out on the water can testify to manifold experiences and the interesting thing is the absolute unpredictability of a strike and the amazing variety of results from one. Be prudent as you can and take your chances like everyone else. There are no guarantees.  
Regards,
Red


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## GBurton (Jun 26, 2007)

SD, how do you know that the jumper cables would do "less than zip" ?
If lightning struck the cap shrouds it is likely that the jumper cables would help a lot to transfer the strike to the water where it would be dissapated.

Grounding the boat is not possible anyway since its floating in the water not attached to the "ground"

Edit - in NWR 's case he was anchored...thus attached to the ground.....but his anchor chain may not have been bonded to his mast.



sailingdog said:


> NWR-
> 
> The 2AWG jumper cables probably did less than zip to ground your boat, given the high resistance of the stainless steel used in shrouds and stays, and the low surface area of the clamping method... it was of almost purely psychological benefit if anything.
> 
> ...


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## txmatt (Nov 27, 2006)

GBurton,
Grounding effectively is certainly possible, particularly in salt water. "Ground" is simply something big that will absorb the excess charge and potential.

An interesting article that I found when researching about this: http://www.thomson.ece.ufl.edu/lightning/IEEE.pdf

I was caught out in my first thunderstorm last weekend and have been thinking about this some as a result. I have a deck stepped mast and a full keel with internal ballast (i.e. all ballast is well encapsulated.) No compression post, either; the mast is over a bulkhead. I could run 4 gauge up the mast and then down through the deck and hull and to a copper plate, but I don't much care for that idea as it would be, in my view, inviting a strike and would require new holes in both the deck and hull, not to mention the wieght of the wire in the mast. I guess I could just bond some 4 gauge to the base of the mast instead of running it up to the top. Of course, the marginal effectiveness of the grounding plate in low conducting fresh water that I usually sail in doesn't help motivate me any.

I don't care much about electronics damage as I don't have much, certainly nothing expensive, but more concerned with hull, rigging and people damage.

I would be interested to hear any ideas to deal with this.


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## GBurton (Jun 26, 2007)

The point that I was trying to make, is that the jumper cables provide a path to "ground" as well. You may have a well bonded system with an external plate etc. but this will not guarantee that you will not sustain damage from a hit. The energy transferred to the boat may be enough to overwhelm a "grounded" system and cause a lot of damage.

I suspect what a lot of people are talking about here is not a grounded system at all, it is just a bonded system.

Wrapping the anchor chain around the mast would not be a good thing to do imho


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## txmatt (Nov 27, 2006)

GBurton said:


> The point that I was trying to make, is that the jumper cables provide a path to "ground" as well. You may have a well bonded system with an external plate etc. but this will not guarantee that you will not sustain damage from a hit. The energy transferred to the boat may be enough to overwhelm a "grounded" system and cause a lot of damage.
> 
> I suspect what a lot of people are talking about here is not a grounded system at all, it is just a bonded system.


And the point that SD was making was that the method of attaching the cables (clipping them on) would not provide and adequate path the ground, which I think is probably true. The 2 ga. wire wouldn't do much good if the connection is poor (loose and small area), and the low conductivity of the stainless shrouds relative to the mast has already been disscussed, making this a less than ideal solution.


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## GBurton (Jun 26, 2007)

If the hit was on the capshroud then it is being conducted right? And then you would want a way to take it to your "ground"

Wouldnt the shroud be a better conducter than the fiberglass deck? And nobody said it would be an ideal situation, it would be better than nothing.


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## txmatt (Nov 27, 2006)

GBurton said:


> If the hit was on the capshroud then it is being conducted right? And then you would want a way to take it to your "ground"
> 
> Wouldnt the shroud be a better conducter than the fiberglass deck?


You might want to check out that article I linked to. It explains the heat generated in a 8 ga. Cu wire and why such a wire is inadequate. The same would likely be true for the clips on the cables and the shrouds themselves, for that matter.


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## GBurton (Jun 26, 2007)

What does #8 wire have to do with what we are discussing?


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## Stillraining (Jan 11, 2008)

*Ok Some very good*

Advice by some people with a hole lot more experience them I.

I'm taking it all in !!

Now for my individual case please refer to post # 10 for pictures.

1) I have sofar gathered not to try and redirect the strike horizonally to my existing bonding plate. Ok I got that

2) My fuel tanks straddle the mast step ( Built in fiberglass at construction ) and my keel bolts are SS a very poor conductor Im finding out here.

3) There is no room for any new hull penitrations due to fuel tanks and keel. ( unless drilled all the way thru keel ..yikes!!

4) Lightning current will flow to the bottom of the mast possibally causing severe side flashes befor returnning up mast to posibally disipate thru another mast conected channel. ie..shroud or mast deck to water connection.

Im stuck on what to do on this one guys ?


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## killarney_sailor (May 4, 2006)

*Hard to get hit*

We were hit by lightning a number of years ago on a passage between New York and Bermuda. The remarkable thing was not that we were hit, but how long it took before we were hit. Strikes were hitting the water near us every 30 seconds or so for 20 minutes plus before we were hit. At the beginning it was terrifying but after a few minutes just awe-inspiring.

The boat was a Nonsuch 30 which had a heavy battery cable from the mast base to the forward keel bolt that was perhaps 8 feet aft. The boat has external ballast. Damage was a burnt out voltage regulator on the engine, all the nav lights and a windex that was blown off the mast head and hit the water in a semi-molten state (you could see its shape bending as it fell). I happened to be looking at the mast head when we were hit and it was spectacular to see. There was probably an inch of rain in the cockpit from the intense rain but no one felt anything.

You can get hit, but it was my sense that it is pretty hard to get hit. We were the tallest thing for miles but it took a long time before we got nailed.


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## txmatt (Nov 27, 2006)

Stillraining said:


> Advice by some people with a hole lot more experience them I.
> 
> I'm taking it all in !!
> 
> ...


Maybe dill a hole at an angle through the keel and insert a copper rod connected to a dissapating plate on the outside of the keel? Maybe if you did it towards one side and at a 45degree angle or so it wouldn't be so long.

Your situation doesn't sound a lot more fun than mine.


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## soulesailor (Nov 18, 2007)

Could you get a grounding plate installed forward of the mast step and fuel tanks? Your entire bilge area is flanked by gas tanks? No room anywhere? I don't think lightning will come down your mast and then go back up again looking for another route. It would probably come down the mast and keep going or take another route from the start. That is why I also have my shrouds, stantions, cleats, bow pulpit and push-pit also connected to my 6' long through bolted grounding plate, along with a bottle brush dissipator on the masthead. I would try hard to find a place to get a nice plate attached somehow, it's not something you want to learn the hard way.


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## sailingdog (Mar 19, 2006)

GBurton-

In all the studies of lightning, it generally takes the shortest path to ground... that is straight down the mast... The contact between the jumper cable clamps and the rigging is miniscule compared to that provided by the entire mast, especially if the mast is keel stepped and connected to the keel bolts. Even in the case of a deck-stepped mast, the mast is still the most likely strike conductor, unless it is a wooden or carbon fiber mast.


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## sailingdog (Mar 19, 2006)

If your keel is lead and not encapsulated in fiberglass, you could sink a copper bolt into it and then put a copper plate on the bottom of it... and the keel would act as a conductor to the grounding plate.  Then again, this might even work for an encapsulated lead keel, provided the lead is one giant chunk, and not lead shot or something like that.



Stillraining said:


> Advice by some people with a hole lot more experience them I.
> 
> I'm taking it all in !!
> 
> ...


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## GBurton (Jun 26, 2007)

You're assuming that the hit is going to happen on the mast...

If the mast is deck stepped, without a bonding conducter - now what?
The energy has to go somewhere.



sailingdog said:


> GBurton-
> 
> In all the studies of lightning, it generally takes the shortest path to ground... that is straight down the mast... The contact between the jumper cable clamps and the rigging is miniscule compared to that provided by the entire mast, especially if the mast is keel stepped and connected to the keel bolts. Even in the case of a deck-stepped mast, the mast is still the most likely strike conductor, unless it is a wooden or carbon fiber mast.


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## sailingdog (Mar 19, 2006)

Most deck-stepped masts have a compression post of some sort below them, which is often metal, and usually connected to the mast step itself via several bolts.


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## GBurton (Jun 26, 2007)

Some do but many do not.

The jumper cables could help - please think before you post.


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## LarryandSusanMacDonald (Apr 3, 2005)

I've been on a number of lists with threads on lightning. They all boiled down to the two schools of thought mentioned above - ground and hope the 20 gazillion volts goes down that little wire and discharges into the water or don't ground and hope it's attracted to something else. 

I've worked in the marine industry for a dozen years, I've lived aboard for those same dozen years. We've cruised all around and I've met many people who have been hit by lightning. In each case, also being a lightning -phobe, I've asked many questions. It actually boils down to this: It's a crap-shoot. Ground and you can get hit just as easily as you can get hit by not grounding.

A few anecdotes: a sport fish charter boat at the City Marina in Ft. Pierce, Florida was hit on three different occasions. At the dock, next to other boats. What was different? Nothing anybody could figure. Just serious anti-serendipity. 

A very good live-aboard friend of mine on a 41' 1941 Rhodes (wooden, obviously) sat between two glass boats at the dock. Both had metal masts. The Rhodes had a wooden mast. The metal masts were both taller, one significantly. The Rhodes had one of those static dissipator gadgets and was grounded. During a violent lightning storm, my friend's boat got hit. My boat was about 50 yards away and both my wife and I could feel our hair stand on end just before the hit. The noise was incredible. My friend said they hardly heard a thing. It scarred the mast, and the electromagnetic discharge took out a lot of his electronics. No other harm done. Interestingly, one of the boats next to him was moved to a different slip and it was hit a few weeks later. Maybe the strike which hit my friend's boat was aiming at the boat next to his. Who knows?

Another strange one: a Hunter on Lake Erie was hit. A relatively new boat. The lightning dissipated through the hull above the water line leaving scores, if not hundreds of tiny pin-holes. My guess was uncured pockets of resin superheated. Strictly a guess. 

My opinion? Since it is a crap shoot, I opt for not grounding. Grounding - especially bonding - causes (rather than prevents) electrolysis. Another argument, I know, but I have seen it way too many times - corroded through-hulls are bonded through-hulls. It makes sense to me, you've got a battery and you've essentially turned it on by connecting all of your anodes together, raising the potential. 

I am told that you have less of a chance of getting hit while under sail than at a dock. That may be true - I've never met anyone who has been hit while sailing - but it also may be that boats spend more time at the dock than sailing (unfortunately). So if a boat is going to get hit at any given time, odds are it's going to be at the dock. 

Cap'n Larry and Saltwater Suzi


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## sailingdog (Mar 19, 2006)

Gburton-

Using the jumper cables is far more likely to give someone a false sense of security than it is to actually help. There are far too many variables to really say for certainty. It depends on whether the boat is deck-stepped or keel stepped, whether it has a metal or a wooden compression post, whether the keel is encapsulated or not, etc.

However, in the overall scheme of things, jumper cables are far more likely to cause sideflashes or do nothing than to actually reduce the risk of getting hit. That's been pretty well proven by what studies are out there. You might want to take your own advice and not post a technique, which at best is going to give a person a false sense of security and possibly prevent them from taking effective measures.  



GBurton said:


> Some do but many do not.
> 
> The jumper cables could help - please think before you post.


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## Wayne25 (Jul 26, 2006)

I don't really have a good grounding path from my deck stepped mast to the exterior of my hull. So I bought 10' of heavy tinned marine battery cable with a 3/8" watertight lug on both ends. I connect it 6' up the mast using a metal slug stop in the mast groove ( the kind with a stud and thumb nut) and to a very well ribbed zinc (the kind used on a large Yammy that gives many feet of linear edge exposure) and drop the zinc in the water. This produces a direct path to a very good ground at a very slight angle. it is very easy to set up. I use it when at dock or when there is a storm at anchor. I can also use while underway if I'm caught out in a storm. Seems to be the best solution for me. It also keeps the grounding outside of the cabin.


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## GBurton (Jun 26, 2007)

How would jumper cables cause a sideflash? If they were not there its possible the chainplates could be the sideflash point. 

Do try to keep up.


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## Stillraining (Jan 11, 2008)

*My Keel is*

encapsulated. I do not know about the ballest I will try to find out. Could it be iron? Very hard to drill if so.

Great idea though!!

Now you guys got me thinking about my mitzen mast also which is deck steped mad our bed is right under it!!. I figured the cone of protection would protect it but now this discussion has me doubting that.


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## cspots (Jan 22, 2008)

Loewe said:


> Can anyone say "snake oil" ?  If any of the methods mentioned/marketed had any empirical data to support their effectiveness in a true scientific method, they would have cornered the market on said devices and insurance companies would give us a break for installing them. The safety recommendations given by knowledgable sailors are still valid if caught in those situations, but some of these antics are as effective as trailing a dead cat over the side.


Thanks for the warning about bogus nature of the "lightning rod salesmen". Nobody has proven anything better than the basic lightning rod system in over two centuries of trying to sell their expensive scams. Granted, some devices could possibly be slightly more effective, but the controlled study with power to prove it has not yet been done - it would be very difficult, and expensive.


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## artbyjody (Jan 4, 2008)

cspots said:


> Thanks for the warning about bogus nature of the "lightning rod salesmen". Nobody has proven anything better than the basic lightning rod system in over two centuries of trying to sell their expensive scams. Granted, some devices could possibly be slightly more effective, but the controlled study with power to prove it has not yet been done - it would be very difficult, and expensive.


Quite agreed... typically the school of thought is having ground points at the ends of the boat ....or having that ferro effect interior... I think one of the main issues here is that you are not talking a spark form a shore power box... thousands if not millions of volts - and dare we remind people lightening is STATIC - it has no direction and has at whim a desire to go anywhere it wants to...usually many places at the same time...

Having been struck twice by lightening on the ground myself... there is no rhyme or reason unless it actually has a mind of its own - and there again - there is no winner...


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## TSOJOURNER (Dec 16, 1999)

OK, I bailed out at Page 3 and jumped to the last page, so I apologize if I'm restating someone else's point, but here's the bottom line. If you play golf, you know that every golf course has resident trees - made of wood - willing to testify that lightening is not respectful of dielectric properties of its victims. Yes, lightening is compelled to follow the laws of physics and must follow a conductive path, but here's a flash (no pun intended) - Lightening is usually accompanied by rain! Rain is conductive and makes the surface of anything it coats conductive! Aluminum, stainless, wood, fiberglass, are all potential paths for conducting current from a million volts when coated with rain. "Coaxing" the current to follow more conductive paths that present less risk of damage from the arcing (metal becomes molten at arc points - hence, arc welding - so robust connections are much more effective than clamps), and less risk from the high temperatures generated for an instant during the discharge, do help mitigate the risk of fire and blowing a hole in a stricken hull as lightening seeks its own path. 

Now, what wipes out the electronics? Rarely, is it the current flow from the strike. It's generally the electromagnetic field generated by the current flow of the lightening as it seeks its path to the water and then to ground. Whether that path is actually metal or the watery skin of a wooden spar, it will generate a powerful electro-magnetic field. The field will realign those miniscule magnetic storage places known as software or firmware and will induce side currents in any wiring path that completes a circuit. It is these properties that are injurious to the electronics. 

So, what's the prescription? To make it risk free, stay off the water (and the golf course). OK, you've already declined that option, so you've decided to accept some risk. Good for you – you’re a sailor! A robust grounding path from the mast to the water will greatly help (but not guarantee to) avoid burn damage from the strike and keep you floating. Not having this will decrease the risk of being struck but increase the risk of catastrophic damage if hit. I like staying afloat and not burning, so I generally go with grounding when lightening is likely to think I’m the most attractive thing around. In anchorages, I play the probability side and go for less attractive. Disconnecting all cables from electronics definitely does help to protect them and is highly recommended. Keep this in mind when installing new electronics, so that it’s not an ordeal. Putting anything storing data or programs - chips, discs, hard drives, etc. - in a metal box tucked away from where you anticipate lightening paths is also a good practice, but understand even this may not save them. 

Or you can follow a friend's prescription. He anchors near large cats with their taller masts and larger acreage touching the water. Two months ago, anchored in the San Blas Islands, it paid off when the cat anchored 50 yards behind was hit. But the electromagnetic field still wiped out his laptop and induced a fatal current in his stereo system! 

Good luck!


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## Joesaila (May 19, 2007)

I did some military training and was told by experts that if you are in a boat that is being fired upon...get away from the boat!..stop me if you've heard this before. I heard the same thing about lightning. So how bout this...you rig a 2 foot piece of steel to a halyard and connect it to some wire and then haul it up the mast...just before an electrical storm arrives....then throw the wire that is bolted to a 4' piece of stainless overboard. You could even 'try' to float it away from the boat and use nylon insulated spacers but then all this makes 'get away from the boat sound so easy'. 'Whew...depending on your location, praying just may be the best option'.


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## Classic30 (Aug 29, 2007)

Joesaila said:


> I did some military training and was told by experts that if you are in a boat that is being fired upon...get away from the boat!..stop me if you've heard this before. I heard the same thing about lightning. So how bout this...you rig a 2 foot piece of steel to a halyard and connect it to some wire and then haul it up the mast...just before an electrical storm arrives....then throw the wire that is bolted to a 4' piece of stainless overboard. You could even 'try' to float it away from the boat and use nylon insulated spacers but then all this makes 'get away from the boat sound so easy'. 'Whew...depending on your location, praying just may be the best option'.


Getting away from the boat in most cases will mean getting rather wet, increasing your chances of becoming a good conductor for any stray currents.

You'd be far better off forgetting about fancy methods for trying to dissipate a zillion volts of electricity and going below where it's warm and dry and reading a good book.

Murphy's Law notwithstanding, the boat will look after itself just fine.


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## bhcva (Feb 11, 2007)

*Hit on the Chesapeake*

Our Caliber 40 was hit a few years ago in an Anchorage near Annapolis. The boat is not grounded. Damage showed that the lightening came down the two back stays, the front stay and the mast. All mast head stuff was gone. Most of the electronics took a hit.

Evidence it came down the mast was limited to a pin hole in the depth gauge near the base of the mast.

The front stay was 'charred' at the roller furling joints so it was replaced.

The charges that came down the two rear stays jumped from the stay to a nearby screw in a piece of trim adjacent to the stay straps and blew away the trim from the screws to the tip of the trim...a couple of inches. The damage on both sides was identical.

While standing in the cockpit just after it happened not fully realizing what had happened, I watched a boat behind us moving thru the anchorage get hit....the mast bulb (and probably other gear) just exploded.

There was no time to do anything like hook up battery cables or the like...a very fast moving storm that continued to produce a dazzling show as it moved across the bay. Just don't touch anything!!

Bruce


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## notyet (Oct 20, 2004)

*Lightning Protection*

This website by a former U.of Fl. scientist who now works full time on the lightning issue is the best I have seen on what lightning does when it strikes an object and how to prevent major damage (marinelightning.com). Interestingly, he claims the scientific evidence indicates that the real problem area for boats is from side flash at the waterline.
I'm no physicist, so he could have this all wrong for all I know. It would be great to hear views from someone more technically able - which isn't saying much!
Cheers,
Jeff Wallin
Allied Seabreeze #126


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## TSOJOURNER (Dec 16, 1999)

I have a 26' ungrounded sloop with an outboard. Am I better off leaving it alone or I have been advised that attaching a battery jumper cable to a shroud or the mast and hanging it overboard might be safer in lightening ?


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## Classic30 (Aug 29, 2007)

chaschas said:


> I have a 26' ungrounded sloop with an outboard. Am I better off leaving it alone or I have been advised that attaching a battery jumper cable to a shroud or the mast and hanging it overboard might be safer in lightening ?


Assuming your boat is plastic or wood, definitely leave it alone.. and head for shelter. 

I'd suggest disconnecting any electrics to the outboard though if that's easy to do.


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## artbyjody (Jan 4, 2008)

Found an interesting study on the subject and just though I would share it:

Lighning and The Small Boat


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## sailingdog (Mar 19, 2006)

Thanks for that link...since my boat is technically a trailer sailer.  A big one...but still.


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## SimonV (Jul 6, 2006)

sailingdog said:


> Gburton-
> 
> Using the jumper cables is far more likely to give someone a false sense of security than it is to actually help. There are far too many variables to really say for certainty. It depends on whether the boat is deck-stepped or keel stepped, whether it has a metal or a wooden compression post, whether the keel is encapsulated or not, etc.
> 
> However, in the overall scheme of things, jumper cables are far more likely to cause sideflashes or do nothing than to actually reduce the risk of getting hit. That's been pretty well proven by what studies are out there. You might want to take your own advice and not post a technique, which at best is going to give a person a false sense of security and possibly prevent them from taking effective measures.


From what I have found out. The use of jumper cables or chain is not to direct the lightning hit but to bleed off the static built up in the vessel, thus making the vessel less attractive to the lightning.


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## Classic30 (Aug 29, 2007)

SimonV said:


> From what I have found out. The use of jumper cables or chain is not to direct the lightning hit but to bleed off the static built up in the vessel, thus making the vessel less attractive to the lightning.


Simon, there's two issues at stake here:
a) before the hit, and
b) after the hit.

Sure, jumper cables "might" bleed off static beforehand, but if you get hit they'll be toast... just like this thread should be given that it's approaching 3 months of age...


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## Falballa60 (Aug 31, 2017)

cspots said:


> The definitive answer isn't in for lightning protection on a sailboat. It isn't even clear how all the damage is done by lightning, nor what type of lightning we are trying to protect from. Any time there are many ways to do something, it means that either anything, or nothing works well enough.
> 
> The basic concept of a simple lightning rod, with a direct connection to ground, has worked very well for centuries. (Possibly until we started to have phone and electrical wires going into buildings?) Since the early 1800's the British Navy very successfully prevented damage from lightning strikes on wooden sailing ships, with wooden masts by using an iron rod and iron wire from the mast tops to the water. Nobody has proven any benefit over these simple systems, in spite of all the hype of the lightning rod salespeople.
> 
> ...


I was searching a way to do with catamaran, because the mast, if forward it just stand on fiberglass and is 8 feet from waterline, if centered it rest on a steel post that can be grounded to the mast, but what do you do with the distance between the foot of the steel post and the water ... you need to pass something through the hull bridge and .. and... "something that connect to water". %#)(*%)#@( 
From what I red, many catamaran have their electronic burned, in my mind this is because the lightning pass by the VHF antena and cable, trying to divert away is a good idea.
Your idea is very good for catamaran, but you need to be preventive and install it very soon, or during the night or having it in place when you dock the boat.
This is very labor intensive.


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## Arcb (Aug 13, 2016)

What a great thread to revive. 

I do wish I understood lightning strike on day sailors better so I could work on strategies.


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## RichH (Jul 10, 2000)

Falballa60 said:


> I was searching a way to do with catamaran, because the mast, if forward it just stand on fiberglass and is 8 feet from waterline, if centered it rest on a steel post that can be grounded to the mast, but what do you do with the distance between the foot of the steel post and the water ... you need to pass something through the hull bridge and .. and... "something that connect to water". %#)(*%)#@(
> From what I red, many catamaran have their electronic burned, in my mind this is because the lightning pass by the VHF antena and cable, trying to divert away is a good idea.
> Your idea is very good for catamaran, but you need to be preventive and install it very soon, or during the night or having it in place when you dock the boat.
> This is very labor intensive.


Here's some 'food for thought' based on some of the newer or most recent data as derived from Boat/US casualty statistics based on the the much higher potential of *catamarans* being struck by lightening: http://marinelightning.com 
Id also research the latest info directly from Boat/US on their website, etc.


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## RegisteredUser (Aug 16, 2010)

I think if the understanding was known and definitive....we wouldn't have so many posts concerning lightning...

It's interesting to read about different strikes on boats and what was affected. It's different, from mild to sinkings.


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## Jeff_H (Feb 26, 2000)

When I bought my boat, the surveyor noted that she didn't have a bonding system. I discussed this with him thinking that I would need to install one. He said not necessarily. He noted that oddly boats built in New Zealand, Australia and South Africa tended to not be grounded. He said that in his experience, those boats tended to have less damage in a lightning strike than bonded boats, where he's seen thru hulls blown apart sinking the boat, and every hard wired electronic component destroyed in a strike.

A few years after I bought my boat she was hit by lightning. She was on the hard at the time. It's unclear whether it was a direct hit or she only experienced induced current from an adjacent strike. 

I have a keel stepped mast which sits on a stainless steel beam which is attached to the keel bolts. We think that the bulk of the current ran down the mast, into the stainless steel beam, into the stainless steel keelbolts, down thru the lead keel, and exited at the bottom of the keel, where there was a several inch deep and 10-12 inch diameter crater in the asphalt. 

In terms of damage, everything at the masthead was destroyed. The VHF/FM antenna was a melted ball if metal and plastic and the metal whip burned through. The wind instrument was similarly fried. Down below, all of the hard wired radios and instruments were fried. They were on a common bus bar and one hunch is that this common connection may have carried the surge from the radio and wind instrument into the equipment itself. The batteries were fried and the battery switch damaged. The bilge pump on-off switch was blown into a bunch of small pieces that were scattered around the cabin. Oddly the bilge pump itself was fine and is still working 13 years later. The alternator was unaffected and the engine electronics were not damaged. 

There were a few fried wires that ran fore and aft in the boat, but those were almost random in where they were in the boat and oddly a wire next to it would be fine. 

Again the surveyor said that he was amazed at how little damage was done compared to other lightning strikes he had surveyed. He repeatedly said, he thought I was lucky that my boat was not grounded since there probably would have been a whole lot more damage. 

I had asked him about masthead dissipators, and he said he doubted that they work since he had done a number of survey on boats with dissipatators that had been hit by lightning.

Jeff


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## BillMoran (Oct 1, 2016)

Threads like this aren't likely to go away any time soon.

Oddly, I just finished reading the lightening protection chapter in Nigel Calder's _Boatowner's_Mechanical_and_Electrical_Manual_.

One thing that comes up again and again in the chapter: lightening is _so_ unpredictable that science isn't even sure if we actually understand it. My take is that the unpredictability could be the result of so many factors (the moving air, and the moisture it contains, the objects on the ground and how they present the positive charge, etc, etc) but that it's also possible that there are laws about the behavior of high discharge sparks like lightening that we don't quite have codified yet.

It's the kind of thing that leads to religions. You might be just as well protected by making offerings to the lightening gods to avoid being struck (at least as far as the statistics are concerned).

All that being said, Nigel points out that there is no scientific evidence that _anything_ you do will reduce your chances of being struck. He also points out that a proper lightening protection system is the best way to reduce that amount of damage if you _are_ struck, which is the complete opposite of what Jeff_H's story conveys.

Personally, I might just stick to making offerings to the gods.


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## colemj (Jul 10, 2003)

Jeff_H said:


> When I bought my boat, the surveyor noted that she didn't have a bonding system. I discussed this with him thinking that I would need to install one. He said not necessarily. He noted that oddly boats built in New Zealand, Australia and South Africa tended to not be grounded. He said that in his experience, those boats tended to have less damage in a lightning strike than bonded boats, where he's seen thru hulls blown apart sinking the boat, and every hard wired electronic component destroyed in a strike.


There is a difference between bonding for lightning and bonding for corrosion. Typically, thruhulls are bonded for corrosion reasons (also controversial), but are not bonded to a lightning bond circuit. Lightning bonding is usually a direct path from the mast to a suitable underwater metal added specifically for ending a lightning bond circuit.



Jeff_H said:


> I have a keel stepped mast which sits on a stainless steel beam which is attached to the keel bolts. We think that the bulk of the current ran down the mast, into the stainless steel beam, into the stainless steel keelbolts, down thru the lead keel, and exited at the bottom of the keel, where there was a several inch deep and 10-12 inch diameter crater in the asphalt.


So your boat is bonded for lightning whether you intended to or not. Without that bond, it is entirely possible for the lightning to exit all throughout the hull, or any random and more damaging place than it did.



Jeff_H said:


> In terms of damage, everything at the masthead was destroyed. The VHF/FM antenna was a melted ball if metal and plastic and the metal whip burned through. The wind instrument was similarly fried. Down below, all of the hard wired radios and instruments were fried. They were on a common bus bar and one hunch is that this common connection may have carried the surge from the radio and wind instrument into the equipment itself. The batteries were fried and the battery switch damaged. The bilge pump on-off switch was blown into a bunch of small pieces that were scattered around the cabin. Oddly the bilge pump itself was fine and is still working 13 years later. The alternator was unaffected and the engine electronics were not damaged.
> 
> There were a few fried wires that ran fore and aft in the boat, but those were almost random in where they were in the boat and oddly a wire next to it would be fine.
> 
> ...


Your surveyor's opinion isn't very applicable to a boat on the hard. In the water could be a completely different result between a bonded and unbonded boat. Anyhow, your boat was bonded (grounded) for lightning, as you describe above. Having seen dozens of lightning struck boats - both bonded and unbonded - and our boat having been struck by lightning, I disagree with your surveyor's opinion on bonding. I do agree with his opinion on dissipators.

Lightning gets into the boat DC ground circuits through the VHF coax. It really is a good path for this. Once inside the circuit, it does just as you described happening to you - it goes everywhere and takes out everything. Masthead vhf antennas are a real tradeoff in this sense. Coax protectors like the clamps sold by Polyphasor can help in this, but it remains a tradeoff.

The point of bonding isn't to protect electronics - those are going to get fried regardless - it is to provide a controlled exit path for the strike. Search the internet for pictures and you will see lots of boats with holes blown through their hulls. I have seen 4 unbonded boats sink in their slips from hundreds of small holes blown out of the hulls.

Mark


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## RegisteredUser (Aug 16, 2010)

There are some things so strong and overpowering that we cannot harness or control. 
Hurricanes, volcanic eruptions, liquor stores closed on Sundays, and lightning.


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