Lightning

[EmeraldBay]

Advice on Lightening, apart from avoid it.

Has anyone been struck and what was the damage?
Any bright ideas on protecting the boat? I have heard placing all electronic items in the oven will protect them. It acts like a faraday box, or the microwave.

If struck, and you don't have a conductor, would most fuses blow?
I have also been advised to go dead ship, and turn everything off.

All comments welcome.

Guy

 

[dparilla]

Been hit once. In the marina we were zapped when it hit a neighboring boat. We had no outward indications until we started turning on our electronics. Knot log, chart plotter, vhf were immediate casualties. Over the next week we discovered that our MSD control panel, tank sounder, and even our bilge pump control panel and DC refrigerator failed. Keep in mind, none of these were in use at the time of the strike, as we were moored. We also had a slew of blown small amp fuses. During our haul out we found no immediate indications of an exit point. That is why we think it was a near hit and not a direct one.

While putting handhelds in the microwave or oven is a common recommendation, since the gear is often needed at the time of a storm, I don't see that as a good option..also since the ovens are not meant to be Faraday cages, their utility as such would be suspect.

Boats that have lightning arrestors etc. get hit just as often as unprotected vessels. So I would recommend making sure that your mast is lightning bonded to the keel (see other threads, good old boat, or Nigel Calder's book on marine mech/electrcal).

 

[Bill Roosa]

Re: Lightening

Current thinking by the insurance companies is that you should "take the strike over the side" and not take it down the mast to the keel.
This is due to the water surface (not 6 ft down at keel level) is where the lightning is attracted. only the very top layer of water gets charged by induction when an electrically charged cloud goes overhead. This is also why you see many strikes exiting the boat at the waterline after traveling down the mast.
I'd recommend getting a set of auto battery jumper cables and cut the cables in half so you have a battery terminal clamp on one end and a bear wire on the other. Strip the insulation off the bear end and clamp one cable to the shrouds, forestay and backstay. The other end goes over the side and into the water. make sure the insulation is stripped back enough to have bear metal at the water surface. And unground your keel.

 

[kloudie1]

Re: Lightening

Took a hit in the marina several years ago.. Blew the VHF antenna off .. fried the VHF radio, blew the bulb out of the reverse polarity indicator, physically.. it was on the other side of the cabin. Blew the fuse in the LORAN set but it worked fine after replacing that. Blew out the breaker on the nav lights.. blew up the bulb out of the stern nav light .. Damaged the fan speed control in the air conditioner.. Batteries were off and all dc circuits off.. AC was plugged in and operating the battery charger and air conditioner and a couple of little fans in the cabin.. Fortunately, not a lot of damage.

 

[justsomeguy]

Re: Lightening

https://tomeshew.wordpress.com/2014/07/18/struck-by-lightning/

 

[Skipper]

A guy in our Annapolis harbor had a big breaker style switch for the main ground. Can't rem if it was a breaker or not. He said the lightning comes up through the ground wires and completes the circuit through equipment by arching in the panel, at connections, or even right through insulation.

The boat's batt switch typically only disconnects the positive side.

If a storm were predicted he'd throw that switch and the batt switch, disc the VHF ant, and disc the shorepower. Unfortunately he'd never been hit so no test. Unless...he had been hit and nothing happened.

 

[victorhoisington]

Re: Lightening

So I have a weird one for a lightning hit.

Our Hunter 28, French Temper, was hit a few years ago.

Our Sail club marina has no shore power or other electronics on the docks and our docks are floating with no real grounding of any kind. The boat was hit on the opposite side (kitchen) from all of the electronics. As best we can tell she had a small fender hanging over the side which was rubbing against the hull. A large bolt of lighting came down and split across all of the masts since they were acting as a sort of Faraday shield for most of the boats, however we believe a small finger of lightning found the top of the fender and hit it, entering the boat on the kitchen side, blowing a hole in the side about the size of a silver dollar (later we found the delamination was the size of a dinner plate), the lighting then blew up a bag of chips and exited the hull just ABOVE the waterline through a dime sized hole. No other damage to the boat and lucky for us all electronics still worked.

Our best guess is that the plastic fender rubbing the side of the boat created enough static electricity to attract just a bit of the lighting. According to our friends, who were on the dock hunkered down on their boat 3 slips over, it scared the heck out of them both. No other boats appeared to be damaged and other than an exploded bag of chips and a couple of holes which taught me how to patch fiberglass nothing was impacted.

My mast and engine are grounded to the keel however, I take no special actions for lightning. I've seen it enough to know it will go where it wants and nothing I can do will really help. My friend however does everything he can, He has a lighting arrestor at the mast linked to his backstay and then drags a frayed wire st the stern.

He's never been hit so maybe it works. As for me. I just hope lightning never strikes the same place twice!!

 

[dscribner]

Re: Lightening

Electronics can be replaced and the insurance industry waffles more on this than cholesterol in eggs. The biggest problem (not inlcuding death) would be having the charge exit through the hull, leaving nice holes as it goes. You're taking on water and your pump is fried.

 

[Maine Sail]

Current thinking by the insurance companies is that you should "take the strike over the side" and not take it down the mast to the keel.

Really? Can you back that up with an insurer that suggests that..... Just one example would be fine....

Considering I have had to add mast to keel bonding after a customer was hit, and this was required by the insurer writing the check, based on the surveyors report, I would love to see an example of an insurer recommending jumper cables over the side. We actually fought that one too because it is not an ABYC requirement, just a suggestion.. Insurer did not care....

Dr. Thompson is recommending it, with his trade marked Siedarc electrodes, but not the ABYC nor any insurance company I know of....

When our boat was hit the strike exited through the very bottom of the keel where the yards keel block prevented a good application of barrier coat. The hull suffered zero pin holes nor any exit wounds other than the keel.

 

[Don S/V ILLusion]

Re: Lightening

The insurance industry is not generally known for its expertise on lightning protection but more likely to be led like shepple by surveyors equally lacking in expertise.

A more knowledgeable industry exists in radio/TV tower installation and maintenance which never allows grounding for lightning to exit at the tower base. Only bad things happen where it exits to ground which prompts them to divert all grounding away from the base. It's not a stretch to carry that principle to boats. In fact, it makes even more sense to protect the hull and keel by diverting the heat expansion and energy dissipation away from the hull/keel.

Having spoken to friends and family in the insurance industry, I would never rely on them for advice in such matters and they freely admit they are influenced by whatever some surveyor writes regardless of his expertise. Also,none of them ever even heard of ABYC.

 

[bawlmer]

Re: Lightening

I apologize in advance for the long post. I just started typing until I realize how much typing I did. Hopefully this will be of some benefit to the discussion.
The wireless communications and broadcast industry has a lot of experience and some good science on how to minimize damage from lightning strikes. I have been in the wireless facilities industry for many years and have been doing lightening protection for tower buildings and the equipment installed therein since the late Eighties.
Even though lightening is electricity the standard rules regarding electricity do not apply. Lightening is static. Fluid logic and RF handling rules apply more. When a radio tower is struck the tower itself becomes energized with the force of the strike. The tower itself and the equipment mounted to it are rarely affected. I had a climber at 600 feet on a 900 foot tower when a lightning strike hit it out of a blue sky. It scared the bejabbers out of him (and me) but he felt nothing more than a slight tingle. The damage occurs when this tidal wave of electricity encounters resistance on its way to ground. This typically happens at the base of the tower. This is where the concrete footings for the tower and guywires and equipment attached to the tower and the equipment connected to it are damaged. The way to solve this is attach very heavy wires to the tower legs and guy wires just above ground and attach these wires to deep grounding rods. The idea is to make the path of least resistance to be the path directly to the grounding points and away from the concrete and radio equipment at the bottom of the tower. The same theory applies when water from a downpour is channeled into a drainage canal rather than flooding a neighborhood. Once grounding is achieved the next level of protection is to bond everything together. Damage occurs when one item is at a much greater potential than another item. The transfer of energy from hi potential item to the low potential item causes the damage. Heavy cable connects the grounding rods at the tower base to each other and to the central grounding point to the building at the tower base. Ground rods are driven outside the perimeter of the building and those are connected together as well and also connected to the tower grounding system around the tower base. All the electronic equipment inside the building are in turn connected to this main grounding system that surrounds the tower. The purpose of this is simple. When the million volt strike occurs. You want everything at that site to be at a million volts for that split second so no differing potentials occur between any metal objects. No flashes, no arcs and no (or minimal) damage. The potential of the entire site will be uniform and will drain to ground in unison to the lower potential. Spark gap protectors are used on any wiring (power, coaxial cable, telephone) entering the structure from either the tower or the outside utilities.
Since I started sailing in 1995 I have been struggling to figure out how to apply these rules and practices to protecting my sailboat. The only real issue is the transition to the sea of the tidal wave of energy that is on your boat at the time of a strike. All other practices gained from the wireless community can be more or less applied to your sail boat. A good bonding system may or may not protect your boat in the event of a strike. Everything metal has to be connected by a cables running directly to a center point (keel bolt?). This will do more to protect the people on the boat and possibly some through hull damage as it would minimize flashes across the cabin, bilge and inaccessible areas.
Here are the challenges that arise when you try to make the trip from land to water. On the land you can disperse lightening energy widely across and deeply into the ground. For this reason resistance is very low. On a typical sailboat the best place to channel lightening energy is through the keel as it is metal and under water. The energy that is collected on the boat through the bonding system is concentrated rather than dispersed. This creates a resistance and may cause damage to nearby sections of the boat if spillover arcing occurs. Another issue is that the keel is a critical part of the boat. The concentrated energy of a lightning strike of sufficient force could damage or separate the keel and sink the boat.
If I were to build a boat for the sole purpose of successfully shedding the energy of a lightning strike it would have a metal hull with a metal frame. Everything metal on the vessel would be bonded to the metal framework. Mast and shrouds would have very robust connections to the frame. Spark gap protectors would be attached to every wire to reduce differing potentials in the wiring system, protecting everything that runs on electricity and preventing wires from carrying damaging voltages and current. Also I would add primary protectors to every wire that came off the mast and ground the outputs directly to the frame. This arrangement would channel all dangerous energy directly to the sea using the path of least resistance. The boat itself would be a faraday cage protecting the people inside it.
The problem is this boat would be prohibitively expensive, slow, hard to maintain and would generally be no fun to sail, and you would never win a race (unless all the other racers got hit by lightning). The most logical compromise I ever heard of on this subject was this. An old friend in North Florida had a 12 foot length of 00 stranded cable with the insulation removed about 2 feet from the bottom. He attached one side to the bottom of his mast and let the other end drag over the side in the water. It kept his kids from being scared by storms and his boat was never hit. Maybe that is all he needed.
Apologies again for the long post.

 

[EmeraldBay]

Re: Lightening

I am new to the forum thing. It's a breath of fresh air to hear informative advice, not just from people who love boating but also from people with great experiences.

So, having read Bawlers informative post, could I be right in saying a good idea would be what Mr Bill Roosa suggested with the jump leads, but in stead of attaching to shrouds or stays attach them to the mast, or perhaps shrouds, stays and mast. Worth a shot at £10 a pair, to try prevent possible sinking.

Prevention is better than cure.

 

[Kermit]

"you would never win a race (unless all the other racers got hit by lightning)"
One could only hope. This is why I don't race. I would be the ONLY one hit by lightning.

 

[Stu Jackson]

Re: Lightening - ARRGH LightNing

1. There is no E in lightning. Except if you want it to be less dark! :dance: Makes searching for answers a lot better if you spell it right.

2. There is this: http://www.westmarine.com/WestAdvisor/Marine-Grounding-Systems

3. There has been, as you can imagine, a TON of posts on this subject. On this and just about every boating forum known to man. As far as I know, there has been no insurance company "answer". Thanks to Steve for his long post, good material.

4. There is no "right answer" but I'll tell ya one thing: I'd trust anything and everything Maine Sail has to say on the subject. Pretty much all the rest is anecdotal. MS has real life experience, on HIS own boat, as well as hundreds of his customers.

Good luck. If you Google it, you can read for years.

 

[Don S/V ILLusion]

Re: Lightening

Stu
I don't know how much experience with lightning anyone from Maine has compared with folks who live where we do. The conventional wisdom for grounding the mast to the keel is popular but not necessarily the best approach.

As always, people should do their own research in making a judgment rather than default to tradition or myth.

 

[woodster]

Re: Lightening

Victor may i ask what kind of potato chips were they ?

 

[victorhoisington]

Re: Lightening

It was the year BEFORE i boat the boat, so I'm not sure, it did help when I was purchasing her that there was 2 holes in the side that needed to be repaired.

The story goes, the boat sat at the slip until the weekend after the strike. When the owners wife went below, her first thought was that she had a mouse and it had gotten into things, since chips were scattered everywhere. Lick for them the lowest hole was about 1 1/2 inches above the waterline (not below) it it might have been a different story altogether.

Lightning is fickle and will go where it wants, providing the path of least resistance as discussed earlier in this forum makes the most sense but, even then its the luck of the draw. My take on it is that any precautions you take are more for you and your crew's piece of mind than anything else.

Thanks to both Maine Sail and Bawlmer for their informative posts. the more information the better.

Good luck and safe boating.

 

[bawlmer]

Re: Lightening

Yes. It is lightning rather than "lightening". Microsoft spell check did not catch this. I will send Mr Gates a scorcher.

 

[Johnb]

An old friend in North Florida had a 12 foot length of 00 stranded cable with the insulation removed about 2 feet from the bottom. He attached one side to the bottom of his mast and let the other end drag over the side in the water.

Bawlmer - appreciate your wisdom. How would you deal with a keel stepped mast?

 

[smokey73]

Re: Lightening

The NFPA (National Fire Protection Association) has some interesting information and I would imagine some well researched guidelines related to lightning protection and bonding in metal structures (on land of course.) Most of the info directly agrees with Bawlmer's post. In particular, the idea is to conduct the strike from the point of impact to a an extensive ground network. The lightning wires (very heavy gauge) were woven copper or aluminum wires all connected and bonded at the top of the metal frame and again at the bottom before the wire is directed into the ground network. Among other reasons, this is to prevent arc flash from the ground wire to the metal beams since the lightning will want to get to ground in that millisecond after the strike. If there is a significant difference in the potential between the wire and the adjacent beam and if the wire is not bonded to the beam, it will arc flash to the beam to get to ground. (and maybe start a fire or ignite something you don't want to ignite.

A really interesting requirement is that the lightning wires can have a bend radius of no less than a certain number of inches (I think its a 8" bend radius but don't quote me on that). Apparently the massive electrical current moving down the wire doesn't like to change direction and it will "blow out of the wire" and onto any other conductor or ground, apparently through a very large distance of air (think really big spark plug).

Now, how does this relate to the discussion. I am not sure that trying to place a set of jumper cables clamped to a shroud and hanging over would do much good as its hard to predict the bend radius that would be in that arrangement. It may just decide to make a jump at that point and go crashing through your cabin and ruining your plans for some chips and dip later. Then again it probably wouldn't hurt anything beyond what the lighting was going to do anyway as long as you did not remove the bonding from the mast to the keel that is already there. I'm not really sure any of our "bonding wires" to the keel would handle the current from a really big direct strike anyway. As somebody said - lighting does some really strange things and it pretty much does what it wants too. I did all this work inspecting lighting protection systems at a Chemical Weapons Destruction facility where we really care about arc flashes and explosions of the propellant and fires where the nasty stuff we're trying to get rid of is located.

I am by no means a lighting protection engineer who is qualified to design those systems, but I did stay in a Holiday Inn last night.