Lightning + Mast = ????

[Douglast]

Having a similar boat, my feeling is that you should avoid anything that would guide lightning in or through the cabin, and I'd also be concerned that any connection to your drop-keel becomes a potential failure point in case of a strike (pronounced "sinking") . The 'lightning' wiring itself could explode or melt in the cabin... not so nice for anyone inside.

From reviewing this subject and reading most of the experts, my conclusion is closest to Atlantic Al's. I'd use something like jumper cables clipped to the mast base, the other end clipped to a metal bar or chain and overboard. The idea is to route the energy into the water through the heaviest path possible (mast & jumpers) that protects the cabin.

I would not bond the shroud bases; our stays are only 1/8" ss wire and could fail if required to carry heavy current.

And seconding the disconnection of electronics, especially antenna leads, to try to minimize equipment damage.

Lightning Protection - ABYC Recommendations
www.kp44.org — The official website of the Peterson Cutter Owner's Group
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What follows is based on the recommendations for lightning protection provided by the American Boat & Yacht Council, Standard E4.
The primary purpose of a lightning protection system is to provide for the physical safety of all aboard your vessel. Prudent actions that should be taken during an electrical storm are: 1) If at all possible remain in the cabin of a closed boat. 2) No one should be in the water or have any part of their body immersed in the water. 3) Do not come into contact with any components connected to the lightning protection system of a properly protected vessel. Otherwise your body could act as a conductive bridge between any items connected to the lightning conductive system. For example, you should not be in simultaneous contact with a metal steering wheel and a metal stern pulpit.
A good lightning protective system ensures that all large masses of metal are electrically connected. This purpose should not be confused with that of the vessel's basic bonding system. A properly installed and isolated bonding system is there to provide a low resistance electrical path to reduce electrolytic corrosion and as a measure of personal protection if there is an electrical fault in the boat's AC/DC electrical systems.
If your sailboat is a vessel with an aluminum mast you have the starting point of a well-grounded lightning rod. This will provide a zone of protection for a radius around its base equal to the height of the lightning rod. Due to some vessels overall length, it may be necessary to install another lightning rod to encompass any areas that do not fall within the zone of protection. Don't forget that the mast itself must be physically bonded or connected through to the common ground - one of the keel bolts or if a encapsulated keel, to the grounding plate, in order to provide optimum protection.
The apex of the rod should be a minimum of six inches above any masthead device. The end should be sharpened to a point. The base of the mast or the mast step if metal, should be connected to a keel bolt on externally ballasted vessels. The preferred wire gauge is No. 6 or even better, #4AWG stranded copper. In no case should such a connection be made to a vessel with internal ballast. The result could be a hole blown through the bottom of the hull. Boats with internal ballast should have a copper ground plate of at least one square foot in size installed externally on the hull bottom. The grounding wire should then be connected to the ground plate.
All wire conductors should be kept as straight as possible. All large metal objects above and below decks should also be electrically tied into the lightning ground conductor. This is a precaution against side flashes. Large metal objects include shrouds, chainplates, toe rails, sail tracks, winches, steering wheels, and bow and stern pulpits. These items can be tied into the ground conductor wire by a minimum #8AWG stranded copper gauge wire, or connected directly to the hull ground terminus.
A thorough inspection of the lightning protection system should be conducted on an annual basis as part of normal maintenance procedure. All connections should be maintained tight and corrosion free. Any corrosion will impede the flow of electricity and promote side flashes. For that reason it is important that the lightning protection system receive the same attention as the rest of the systems aboard the vessel. This should be included as a part of the annual lay-up and maintenance procedure. For additional details regarding the lightning protection standards readers should refer to American Boat and Yacht Standard E-4Source: ABYC Recommendations on Lighting Protection in The Marine Advisor, Spring 2001

WILLIKERS..well im thinking if my swing keel bolt is suspect for failure...3/4 bolt..??...well then a very solid connector on the mast that the wire can be hooked to with the highest regard to connectivity and continuity...maybe just the live end a large copper (min one square ft) deep sixed....and hope the slight bend is not an issue...it would not be horizontal thats for sure....far from it..

 

[kenn]

WILLIKERS..well im thinking if my swing keel bolt is suspect for failure...3/4 bolt..??...well then a very solid connector on the mast that the wire can be hooked to with the highest regard to connectivity and continuity...maybe just the live end a large copper (min one square ft) deep sixed....and hope the slight bend is not an issue...it would not be horizontal thats for sure....far from it..

Sure a 3/4" bolt is pretty big, but since your keel pivots freely on it, the electrical connection between bolt and keel isn't necessarily solid. That makes it a weak point.

As you've found, there's consensus around how a larger boat should be bonded for lightning protection, but for us trailer sailors, there's not as much guidance.

I understand that the reason we don't have better answers is that currently there's no testing method that's equivalent to an actual lightning strike. paging Ben Franklin... bring your kite.

And frankly... I wonder if it's actually worth stressing over? I haven't myself heard of frequent fatalities or sinkings of small sailboats due to lightning. I'd love to review the actual stats, if anyone can point to data. I have heard that in general, strikes on ANY occupied sailboat do not usually result in fatalities, due to that big mast-y thing, whereas most direct strikes on an occupied mastless boat do result in serious injury or death.

So for us trailer-salors, the current options are:
- don't occupy the boat in thunderstorms <- absolute best option
- spend an inordinate amount to ground-bond your boat like the big boys
- utilize one of discussed quickie mast-grounding methods, which have apparently been refined into this Zenpole concept, though it isn't tested and available yet
- stay close to a larger, well-bonded yacht, to huddle under their cone of protection
- don't worry about it.

My first mate and I have had two close brushes with lightning. One was canoeing - we misjudged the onset of a storm, and were in the middle of a 1-mile wide bay with lightning all around. A hit then would have been game over. Stupid stupid stupid. The second was overnighting with 9 other boats, anchored behind the protection of a sand spit, but otherwise completely open, and there was an active widespread thunderstorm that raged all around us for several hours. Again not bright... but we all survived, though some sailors complained that some of their electronics went out.

 

[Slow Mo^cean]

How about one of these guys?
http://www.westmarine.com/webapp/wc...toreNum=50523&subdeptNum=50566&classNum=50571

 

[justsomeguy]

How about one of these guys?
http://www.westmarine.com/webapp/wc...toreNum=50523&subdeptNum=50566&classNum=50571

Fear-mongering rip-off.

 

[KD3PC]

How about one of these guys?
http://www.westmarine.com/webapp/wc...toreNum=50523&subdeptNum=50566&classNum=50571

might annoy the birds....but beyond that snake oil and linament would work better...

 

[walt]

I can’t say if the wire brush dissipaters affect your chance of getting struck but believe I can describe what they actually do.

Any sharp point at the end of a conductor in a high enough electric field will generate corona current. How this happens is very interesting and some details are here http://zenpole.com/Corona_current_rev_0.pdf but the readers digest version is that the high electric field at the sharp point will separate an electron from an air atom. The electron flows into the conductor and the resulting atom missing the electon becomes a positive ion and in the case of the sharp point at the top of the mast, the positive ion either gets blown away by the wind or drifts toward the negatively charged cloud.

If the mast is not grounded, the above mechanism just added an electron to the mast and this will cause the mast voltage potential to rise according to coulombs law – similar to charging a capacitor. I.e., rather than discharging the mast, the sharp point (or wire brush) is actually charging the mast. If the electric field persist, electrons keep getting added to the mast further raising its voltage potential (in the negative direction) and this at some point starts to reduce the field at the top of the mast – and eventually reducing the corona current.

If the mast is grounded to the water, the electrons added to the mast go to the water ground.

So we are getting some current flow and charging of the mast due to a sharp point (any sharp point – doesn’t need to be a wire brush) but how significant is this charge compared to the charge of a lightening strike.

A simple Google search will turn up numbers like 5 coulombs for the total charge delivered in a lightning strike.

If you model the capacitance of a mast by rotating it 90 degrees at its mid point and use a standard capacitance equation, a typical mast capacitance to the water ground is 1 to 2 pf (let’s use 1.5 pf). If we were to charge up this ungrounded mast right to the point where it is getting close to arcing to the water surface (lets use 1 million volts), once again we will use a version of coulombs law (Q=CV) to get a charge of 1.5 E-6 coulombs.

So to put this in perspective, the charging of an ungrounded mast due to any sort of sharp point at the top is 3.3 MILLION times SMALLER than the charge delivered in a lightning strike. I.e., it’s really in the noise. You will have to decide if this matters.

In the other case where we have a grounded mast, the corona current will stay relatively constant since the charge going into the mast goes to the water so that the mast voltage potential remains at ground. Lightning Master had some literature on the internet (no longer there) showing current measurements of a wire brush dissipater and it pulses so we need to find some sort of average value which I will use about 50 uA from looking at the graphs.

Using the definition of current Q=It, at 50 uA, it would take about 27 hours for this to dissipate the charge in the lightning strike. But… we are in a conductive body of water and in even hugely shorter time frames, the entire body of water is able to equalize and supply the charge. I.e., the charge dissipated by the wire brush does basically nothing to impact the charge in the body of water.

Interesting also is that the Corona current model also describes the buzzing and shocking that can occur on sailboat rigging during a lighting storm.

 

[onecoolair]

Sooo??....What your are saying is besides being a lethal weapon while mast is laying across saw horses in the boat yard. It can cause the mast to act much like a capacitor. If so that may explain a friends sailboat keel being blown off while still in the slip during a freak electrical storm a few years ago...Mast was keel stepped...Big Hole!

 

[Maine Sail]

The "claims"

"This product does control the causes of lightning strikes and thereby reduces the incidence of direct strikes."

The reality:

Lightning Strike July 4th 2012 (with static disipator)

 

[justsomeguy]

*
Everyone, stay safe on the water this summer.* This weather is wild.

And getting wilder.

 

[Slow Mo^cean]

The "claims"

"This product does control the causes of lightning strikes and thereby reduces the incidence of direct strikes."

The reality:

Lightning Strike July 4th 2012 (with static disipator)

Hmm, I guess the dissipator worked... From the point of view that itdidnt get by lightning..

 

[Bill Roosa]

An interesting observation is that the focus has been on "dissipating the strike" by attaching stuff to the masthead. To actually dissipate a charge it has to be connected to the "other side of the capacitor" Given that the earth side is a layer about 1/8" deep of induced charge (even less in fresh water) on the SURFACE of the water and most of us ground of lightning protection systems using a connection that is
a) electrically insulated as it passes through the water surface level
b) is electrically connected at a location "below" the electrically charged surface (ie the strike must pass through the electric field then beyond it) (electrically impossible BTW)

I think your best bet is to throw a stout cable over the side and attach it to the stays. Then your bottle brush could actually complete a circuit and do some dissipating

An interesting experiment is to unground the lightning grounds from the keel then go topside and throw a bare wire in the water and measure the voltage between the wire and a shroud. This is more interesting in a storm (not recommended though) but any day with some clouds overhead shows the effect.
Now if I could only figure out how to run on static electricity...........

 

[Douglast]

i give up...i think i will just bring my mother in law along and make her wear a tin hat...

 

[Maine Sail]

b) is electrically connected at a location "below" the electrically charged surface (ie the strike must pass through the electric field then beyond it) (electrically impossible BTW)

Hmmm, I have seen multiple boats with lightning exit points at the bottom or side of keels well below the surface and no other hull damage, so absolute statements like "impossible" gives one a pause for a reality check......


Here are some real world examples where the "impossible" actually happened.

Here's one with a pic:

Quote: "The mast took the hit and the lightning traveled down the mast and exited the boat through the keel. The result is that the keel is significantly damaged and will need to be replaced."

It also exited well below water through the rudder likely following a bonded SS rudder post.

A C-36 behind us was hit very shortly after he installed a "bottle brush". The spar was directly grounded to the keel bolt. The keel was all spyder crazed and chunks of paint blown off but the hull was perfectly fine including around the Marelon thru-hulls...

When our boat was hit the only damage to anything below the water was around the very bottom of the keel where bare lead had been exposed due to the wood storage blocks. None of the barrier coat had been blown nor spyder crazed but the areas around the bare lead had some spydering which indicated one of the exit points... We also know it went out through the drive shaft due to carbon being blown all over the engine bay from the PSS seal. Impossible??? Absolute statements like "impossible" are clearly are not adhered to by lightning..

The point is I have seen multiple examples, in person, of lightning exiting through a properly bonded keel and damage was minimized to only the keel and on some occasions directly around thru-hulls which are also well below the waters surface. The majority of boats I have seen that have been properly bonded to ABYC TE-4 have had no hull damage beyond the areas around thru-hulls and the keel or lightning ground plate. Does it happen? Sure but that is why lightning is sooo unpredictable...

 

[RobertLangdirect]

Ah, let's see what the rest of the world has on record

Someone said, "If you have a carbon fiber mast, then good luck, those things explode when hit." This may be true if you do not have proper bonding or even more so within the mast, the proper lightning rod and wire to carry the load. But the proper protection works.

From the URL below, go down to figures 5 and 6, "(R) This shows the side flash in the laminate from the lightning that struck the lightning arrestor. This is superficial damage--the arrestor and lightning ground did their job by keeping the lightning in the conductor and down the mast, not allowing it into the mast laminate itself. "

Read that again, "--the arrestor and lightning ground did their job . . . not allowing [the lightning] into the mast laminate itself."

http://www.sponbergyachtdesign.com/FourMastFailures.htm

"The record shows that carbon masts have survived hundreds of lightning strikes. The greatest damage in a lightning strike (for both aluminum and carbon masts) usually befalls the electronics. We had a carbon cruising mast hit in Massachusetts, and they lost the microwave, television, GPS, radar, and all the instruments. The electronics were completely fried but the mast was fine."

http://www.morganscloud.com/2009/02/18/carbon-fibre-mast-lightning-risk/

 

[walt]

To actually dissipate a charge it has to be connected to the "other side of the capacitor"

The bottle brush manual I believe recommends that the mast be grounded and this will maximize the corona current. But.. as mentioned in my last post, the steady state current is on the order of 50 ua (micro amp - tiny). Since the water body is conductive and nicely "bonded" to the rest of the planet, you would have a hard time dissipating the charge of the planet with a trickle charge of 50 ua.

However, in the very short time frame (like micro seconds), a discharge could grab an enormous amount of electrons from just above the mast and deposit them at the water surface which has two benefits. All the electrons grabbed from above the mast would leave a big positive ion cloud above the mast which would reduce the field in that area and all the electrons added to the water surface would discharge the positive surface charge. The bad news is that is pretty much requires a leader from the surface upwards that does not connect with the downcomming strike. But if it were to connect with the downwards strike... you get hit. Some PHD types in New Mexico doing research on lightning rods were able to document a case where the above did occur. But I would think this happens somewhat randomly and could not be counted on.

I am guessing that any time a lightning strike is discharged in an underwater structure that salt water was involved. Salt water is probably conductive enough and with a large enough area, the charge could dissipate underwater through a keel but then it still would travel up to the surface where the positive charge is.

 

[Team118]

This thread is a bit old and well discussed.

I was wondering, along the lines of the Zen Pole product.

Couldn't I quality jumper cables or make a cable with #0 gauge (or whatever would be best). Install a high quality lug to one end and in the event of a storm, actually connect this to the mast?

Perhaps install or create a band around the mast with 'washer' like hole that I would wingnut the lug to?

Then throw the over end overboard...

It would be a better connection than the battery cable clamps.

I noticed the Zen Pole didn't even connect to the mast, so I assume the lightning would travel down the mast, 'jump' to the Zen Pole and then down to the water?

Chris

 

[KD3PC]

sure, go for it....

read the rest of the posts, you will see, or not see the point...else you will implement your project and feel protected.

btw, lightning jumps quite well, zen pole or no zen pole, cables/clamps or no cables/clamps

 

[anchorclanker]

When we got struck at the old farm house, I actually saw the strike and next morning we saw the damage. The strike burned down the side of a large Cottonwood to within about 15 feet from the ground. It then jumped over 40 feet through the air to the neighboring Cottonwood, and continued down into the ground. The trees were cut nearly a foot wide and nearly a foot deep along the strike and it left large shards of wood all over the property, some thrown over 500 feet. But it wasnt done yet.

At the ground it dug a foot deep by foot wide trench about 15 feet, and blew out a hole 3 feet in diameter and almost 3 feet down into the ground to grab electrical conduit I had buried for the satellite dish. The conduit was blown in half with both ends pointing upward into the air, leaving the ends of the all the wires burned off. Looked like something from some weird sci-fi movie

The receiver in the house and all the electronics on the dish had all those wires attached. The receiver was plugged into an AC outlet through a lightning surge protector, and was also connected to the phone line. The dish was NOT grounded. I had read that grounded dishes were more prone to strikes.

Except for two items, everything electronic that was plugged in or had an antenna was wiped out. All the TV's and VCR's, all the audio equipment, microwave, dishwasher, wireless intercom, stove, telephones, garage door openers, etc.. If it had a circuit board it was toast. On our big RCA TV, which the insurance paid to have checked out, the tech said he never say anything so thoroughly destroyed.

Surprisingly, the satellite receiver and all the dish electronics survived. Those were the two exceptions. Yet all of the energy had to pass through the reciever to get to everything else. I later found all the phone lines were burned inside the walls, and most the TV coax was bad.

When I first started reading about protecting the boat, some of what I read suggested grounding made the boat more susceptible to a strike, some even hinted that ungrounded boats were either never hit, or rarely, and that grounding would make your boat a bigger target. I think thats a false theory, as false as the reason not to ground that dish. Lightning will strike not whats closest, but what provides the easiest path to ground, the path of least resistance. Years ago women in Colorado was struck by a storm nearly 40 miles away, it doesnt have to be overhead to get you. High speed photography shows that almost completely invisible feelers are reaching up from the earth just seconds before the strike. This would be the point where peoples hair starts standing on end. The strike is searching for a path, and building energy, and its going to let go and follow one of those feelers. Its going to pick the one that offers the least resistance. If it happens to be your boat or your body, it really dont care.

This thread shows what can happen, and shows us its possible to survive a major strike. It would be wise to listen to those with knowledge and try not to think we know better.

Several years ago I took my daughter out fishing. At the time she was about 8 or 9, and after seeing storms building off to the west I turned for shore. We then stopped out about 150 feet from our camper and fished a bit and listened to the weather. Suddenly she said "Daddy, why is your hair doing that". I looked up at her and saw her long hair standing up vertically. I dont know what kind of look I had but it scared the crap out of her. I hit the motor and ran the boat hard toward shore, telling her to jump as soon as the boat hit the beach and run for the camper, dont stop. She did, and I did too. I still dont really know what else we could have done in an aluminum boat, but I sure wouldnt want to play with it again if i dont have too. I know jumping into the water wasn't a good idea, but didnt think laying down in the boat was any better. We sure came close though.

 

[jekle]

I cant tell you what to do if your on the boat, but..
I can tell you what will happen (one possibility anyway) if your mast does get struck.
My C22 was hit 9/5/12.. no one onboard, moored in the canal. Mast lights disconnected thru the hull, but VHF antenna was connected. Lightning hit the antenna and traveled down the mast, entered the cabin, followed vhf & mast wiring to breaker panel. Fuse panel pretty much exploded, blowing fuses around cabin (plastic holders just in pieces). Somehow, the charge then jumped to the swing keel cable and used it as a fuse to the cast iron keel. The keel was up, but the boat was in 3.5ft of water. So when the keel cable "blew" out, the resulting explosion damaged fiberglass around the cable exit causing leaks. Had the boat been in deeper water with the keel up, it would have swung free and broke the inner hull out. Luckily mine swung down to the bottom with no further damage.
Long story short, you may be somewhat protected under the mast "cone". But a lightning strike will find it's way to ground no matter what. And sometimes it's thru the cabin.

 

[shemandr]

Jekle's and others experience related above are why the advice to "Avoid anything metal" during a lightening event is little comfort to me.