newbie lightning protection?

[CaptDon01]

Rpludwig,
I retired from the FAA after 38+ years, most of the time I was in the Technical Operations Branch. One of the many hats I wore during my career was serving as the resident engineer overseeing the construction and installation of all kinds of radar, communication, and navigation facilities. The FAA is very concerned about lightning because of the impact to very sensitive equipment, which if damaged, could adversely impact the air traffic system. So they go to great lengths to try and control the path for lighting. But, this involved installation of substantial copper down conductors, and an immense copper grounding system below grade. So I've been involved with my share of lightning and bonding systems. On a C-22, we're dealing with 1/8" cable, and yes, an aluminum mast. When we lived in the Midwest for many years, we kept our C-22 in a slip from roughly April to the end of October. We were in slips in Kansas, Missouri, and Oklahoma, so we experienced our fair share of massive thunderstorms for many years while living there. None of my C-22's ever had any lightning protection whatsoever, and maybe I'm just luck,(however, I've never won the lottery), but our boats never suffered any lightning strike that I'm aware of. Yes, I guess it could happen,(never say never), but lightning is looking for the easiest path to ground, and I'm convinced my C-22's, (and several other sailboats), just didn't fit the bill. Looking at the size of the down conductors I've installed for lightning protection, I would guess there is just too much resistance in an 1/8" cable to support a path for that great amount of energy to flow through, then jump to ground, (but I'm no engineer, so take that for what it's worth).

We've only moved to Florida 5 months ago, and we're just now entering our stormy season I understand,(BIG thunderstorm going on right now, and we're in the path to be hit tomorrow and Tuesday with some severe weather), so maybe ask me again next year what I've done to improve the lightning protection system on my C-22, but I can just about assure you, my answer will still be: "nothing".

Lightning strikes are the least of my concerns. Oh yes, I have great respect for it, I just don't lose sleep worrying about it.

Don

 

[Gene Neill]

Maybe there should be a "sticky" post on lightning strike risk mitigation somewhere on these forums?

Yeah - and all it needs to say is "JUST PRAY!", because nothing has been proven to be more effective.

 

[CaptDon01]

Yeah - and all it needs to say is "JUST PRAY!", because nothing has been proven to be more effective.

Can I get an AMEN!

Don

 

[justsomeguy]

Can I get an AMEN!

Don

Inshallah?

 

[rpludwig]

guess a better question on my OP would have been "have any C-22'ers ever received a lightning strike on their boat?"
...my guess is none!!!

My plan going forward is insurance/jumper cables/religion, in no specific order (well insurance first)!!!

Many thanks to all who replied, I don't wanna beat a dead horse that apparently has already been beaten many times over!

Great Forae (er Forums)!

AMEN!

 

[Benny17441]

Before "getting the hell back to shore" the statistics show that the great majority of boats struck by lightning were at or near land as opposed to boats in open water. It would fall to reason that at any given time there are many more boats docked than at sea but that does not explain the larger incidence on boats approaching land or anchored. The good statistics are that fatalities due to lightning strikes are nil for sailboats. There is a theory about a cone of protection at sea provided by the mast . There are also beliefs that bonding a boat to ground (water) help to minimize damages but may also attract strikes. Nothing has been proven so go with what makes you comfortable. Lightning is so powerful that it will go where it may and nothing we can do to prevent it. To me, like I mentioned, the most important statistic is that the number of fatalities in sailboats due to lightning strikes is nil. We cannot outrun storms so dealing with lightning at sea is a reality. With Tampa being the Lightning Capital of North America I see my share of lightning on the water and in land every year. "Tampa" is a Native American word which translates to "fire stick".

 

[JamesG161]

Curious as to why?

The use is to help dissipate static charge build up on your boat's mast that occurs just before a strike. Like grounding the static electricity charge when wearing a wool sweater.

I have one, but all I can say it is like my anti-Elephant charge whistle. I blow that whistle every day and still no Elephants, so it must work.

Mine is mounted horizontal. With the boat when I bought it.
Jim...

 

[vhoisington]

So I'll 2nd Don's comments above. Lightning will stick where it wants and no amount of grounding will help. My boat suffered a single strike a few years ago. No it didn't hit the mast or the shrouds, or any of the other metal parts on the boat. We had a small rubber fender on the port side not touching the water. The rocking of the boat and rubbing of the fender on the hull caused static which caused the lightening to hit the top of the fender, enter the boat at that point (yes through the bare hull) now that it was inside the kitchen, the bag of Fritos appeared and promptly blew up all over the boat ( we thought we had a mouse). After entering the kitchen area and not finding any metal, it traveled down the hull until finding the end of the fender and blew itself back outside the boat. The initial hole at the top was the size of a silver dollar but when ground back to clean fiberglass was the size of a dinner plate. The bottom hole 1 inch above the water line, was the size of a dime.

No, metal, no electronics on that side of the boat. Other than a little bit of fiberglass and gelcoat and a bag of chips, $0 damage. Lucky yes, did I change my lightning strategy ( do nothing) no. I just can't find anything that works reliably that is worth the cost. Insurance is paid, the boat stays home on most bad days and frankly, I have way too many boat jobs to do. Maybe someday it will bubble to the top of the list.

Either way, it's your call. Do what makes you most comfortable and gives you the least amount of worries.

 

[kloudie1]

This seems to be latest and greatest thinking on charge dissipation/lightning stuff:
http://marinelightning.com/
a good read..

 

[JamesG161]

a good read..

Nice animation showing the charges as the build up on the boat, if not well grounded.
Jim...

 

[walt]

The use is to help dissipate static charge build up on your boat's mast that occurs just before a strike. Like grounding the static electricity charge when wearing a wool sweater.

wool sweater.. oh no.. an analogy which has nothing to do with what actually happens but sounds good - another reason I dont like analogies... LOL

James, I know you like to understand what goes on with lightning so would propose that Corona current is whats involved with the static dissipators and Corona current is responsible for the shocks you can get by touching ungrounded metal on a sailboat plus the buzzing noise sometimes heard. Corona current explains all of this - and also is the only thing that explains all of this. Google has lots on Corona current - here is one link https://en.wikipedia.org/wiki/Corona_discharge

Previous to a strike, you can have a large electric field between the sky and ground and since a voltage can not develop across the conductive mast (other wise current would flow), the electric field is enhanced at the ends of the mast. If we examine the top of the mast, the enhanced electric field strength and polarity is such that it strips off electrons from air molecules. The electron is swept to the conductive mast leaving a positive charged ion in the air. The elections are stripped off in an avalanche which temporarily reduces the field shutting off the avalanche until the ions are swept away by the field and the wind. Then the process repeats. The frequency of this periodic process is often in the audible range and you can hear it as a buzz.

One interesting thing about Corona current.. is that the ion in the air has the same charge as an electron but a huge larger mass (like 65 thousand times or something like that). So both the ion and the electron have the same coulomb force. But the acceleration of the electron is WAY higher since it has a much smaller mass so the mobility of an electron is a huge amount higher than the mobility of an ion. Because of the very low mobility of ions, corona currents are always very small.

So what happens to the electron that gets swept to the mast? For an ungrounded mast which looks like a capacitor to the water surface, the electron charges the capacitor. More electrons, more charging. As electrons are added to the mast, the mast potential voltage increases and of course this is how you can get shocked by touching shrouds etc on the boat. Once the shock occurs, the potential between the two conductors is reduced.

Some of you may have even heard a periodic pop pop pop on a sailboat (and also off a sailboat) and this is also only explained with corona currents. You need two insulated conductors at different heights so they are in different potentials of the electric field. A Corona current at the top adds electrons to the higher conductor which eventually sparks to the lower conductor. The lower conductor then has corona current off its low side (releasing negative ions). The Corona currents at the top and bottom continually charge the capacitance between the two structures and the period of the pop is dependent on the current and capacitance. FYI, Corona currents are the only way to explain that pop pop pop!!

It only takes some sharp object at the top of the mast for Corona current to occur but the wire brush things of course have many sharp points so may enhance Corona current. Remember these are adding electrons to the mast and if the mast is grounded to the water, the mast does not charge as the electrons are swept away by the vast positive charge at the water surface. Mast charging begins to reduce the field at the top of the mast which will also reduce Corona current so with the grounded mast, Corona current is enhanced at the top of the mast over an ungrounded mast.

Can you neutralize the positive charge at the water surface with Corona current? Remember that the current leaving the top of the mast is positive ions which have terrible mobility compared to an electron. And you have a vast source of positive charge at the water surface. I think it would be like trying to empty the lake with a tea spoon.. On the water, you just are not going to affect anything even for less conductive fresh water.

But.. Corona current at the top of the mast "may" have an influence on how effective the top of the mast is creating a leader to attach to the lighting strike.. I will dig up a paper on this but I am guessing no one is reading this by now LOL..

 

[Flamingo1]

So, drink Dos Equis instead of Corona? Got it.

 

[JamesG161]

James, I know you like to understand what goes on with lightning so would propose that Corona current is whats involved with the static dissipators and Corona current is responsible for the shocks you can get by touching ungrounded metal on a sailboat plus the buzzing noise sometimes heard

Well you get wayyyy in to the micro model of what might be happening. The Corona effect is taken in to account on the safe distance you can walk near a high voltage transformer or switch center.

For any arch to "strike" the resistance of the air has to be low enough to conduct. Many factors determine air's insulating ability and thus the near randomness of a strike.

The Corona effect is just a known ionization of nearby air by extremely high voltage potential, man or nature made.
I am not sure of the mechanism and from a Macro model, the "fuzz ball" has much more ability than your slick surface mast, to prevent a voltage potential difference between the water ground and your mast top. The concept is to make your mast the same potential as the water around you and never let a charge build up on the mast. It does work in the lab.

Air is a good insulator and ionizes (charged molecules) to allow current flow. No lightning on the moon, Corona or not.

All I know is make my boat look like the surroundings to minimize the potential for strikes. Ben Franklin noted that an electrical charge cannot be created, but only collected. Still true today.

So don't let your boat/mast be a collection point.
Jim...

PS: The wool sweater is a real Ben Franklin test. Not an analogy.

 

[JamesG161]

So, drink Dos Equis instead of Corona? Got it.

No, drink more Corona and then don't worry about it.
Jim...

 

[Bill Roosa]

Walt from post #15
if you connect the mast and keel then they cannot be two plates of a capacitor. You have to consider the larger picture. to wit. clouds have a charge (top plate) and induce a charge on the very top of the water surface (read 1/8") (bottom plate) over a very large area with air as the dielectric . Your boat floats on the bottom plate of that capacitor with the keel sticking below the bottom plate and your mast sticking up into the air dielectric. If you route the lightning from the mast base to the keel you are going to get to a point at the water line level where there is absolutely no electrical potential to drive the electrons down below the water surface (lower plate). Electricity does not have inertia as we understand it and it WILL do a 90 degree turn toward the water surface (inside the cabin!~!~!). That would be through a wire or large metal tank in most cases as FG does not carry current well.

 

[walt]

Bill, you are describing another case where the mast is directly connected to the keel and the keel makes electrical contact with the water. In this case, we have a 3D resistance from the keel to the water plus all capacitance.

I think you have posted this before but water surface gets charged positively by the charge in the sky. As the strike comes down, there is an intense electric field from the moving strike and this further ionizes the water surface (called "induced current flow" - this is also how current flows in a capacitor). This was in a "radials" paper and I have lost all these links now but it basically calculated a surface charging time that was dependent on the carrier density in the water. For fresh water, this charging time was in the micro second time frame. So a bunch of years ago I did a little experiment with an instrument (ESD tester) that generates 10K voltage with about a 10 nsec rise time. The first picture below shows a little mock sailboat with an ungrounded mast, then a spark gap to a second conductor just above the water surface. You can see the spark gap working but the interesting thing here is that with a 10 nsec rise time and fresh water, the water surface does NOT have time to charge yet you still see the spider web outwards flow at the water surface. What "we" think is happening here is that water has a very high dielectric constant (about 80 times larger than air) so water does not ionize and instead the charge still flows in ionized air just above the water surface as that is still the lowest impedance path. As you make the water more conductive with salt, the size of that spider web gets smaller. The second picture is the same exact test but in very salty water.

The point being here that the water surface is very important not only for the surface charge but it also may be the lowest resistance path especially in fresh water.

In the case you described of the mast connected directly to the keel, in salt water the keel to water is low enough resistance to apparently dissipate the current. Lots of folks in sailboat with good grounding do in fact safely dissipate charge from the keel to the water safely (in salt water).

But as the water gets fresher and the resistance of the keel to water connection gets worse (higher), now the side flash from the bottom of the mast directly to the water surface gets more competitive. And.. in fresh water, keel boats with good grounding between the mast and keel may still see the spider web flash on the water surface (someone did see this in a discussion from way back).

[

 

[JamesG161]

water does not ionize

True!
You can make Hydrogen and Oxygen though!
Unless your boat is in Lake DistilledWaters, there is enough dissolved salts (minerals) to ionize and conduct the electrons. It is NOT the water, but the dissolved salts that conduct electricity. Distilled water does NOT conduct electricity.

The saltier the water the lower the resistance to amp flow. Thus a nearby water strike will quickly dissipate the amps in the water. I would suspect most boat damage is done by nearby water/land strikes conducting reversely thru your keel or shore power line or side branching.

Trust this, if your boat takes a direct hit, send me a picture of the hole in you boat after you insurance company refloats it.

Have you ever seen a burnt capacitor? Toast!

So...

Don't let Ben Franklin's researched static charge build up. Ground your boat and avoid capacitance.
Jim...

 

[Bill Roosa]

Exactly my point walt!!! the strike spreads out along the WATER SURFACE and does not penatrate the water to the keel and then proceed upward to the water surface. The thing to understand is the charge is not "in the water" it is ON THE WATER SURFACE. No amount of insurance wishing or prayer will make the strike go "below the bottom capacitor plate" It has to dissipate AT THE WATER SURFACE

 

[Don S/V ILLusion]

I have the definitive suggestion of how to protect your boat.

Park it next to mine. It seems to work well for my dock neighbors.

 

[Kermit]

I have the definitive suggestion of how to protect your boat.
Park it next to mine. It seems to work well for my dock neighbors.

That same theory keeps my neighbors' boats free of all osprey poop.