Lightning Protection

[GordMay]

I've never heard a reputable scientist advocate bottle brushes,
and
the blunt tip air terminal has been generally advocated since the late 90's. I believe the various "Standards" commitees adopted blunt rod recommendations about 2000.
I'm sorry if I seem abrubt, but I've previously presented an extensive review of the literature - and there's not a lot of controversy (amongst the "informed") about these simple alternatives.

[Ex-Calif]

"Did you ever get the feeling they have not perfected the science behind lightning strikes yet?? (smile)."

On the contrary. The science behind electricity and lightning strikes is extremely advanced. As an "airplane" person I am very familiar with the subject as relates to aviation. Commercial airplanes are struck all the time - everyday! I am somewhat bemused(?) by the boating community where there is a tremendous amount of pseudo science and old wives tales. Electricity is very predictable.

We just had a sinking 4 weeks ago here at our club. A J24 mast was struck during a thunderstorm and the boat was holed and sunk on teh mooring in 40 minutes.

After haulout I took a good look and it is clear the strike carried down the mast and jumped off the mast below decks about 18 inches above the step. The strike went forward and blew out a 3 inch diameter hole about 5 inches forward of the mast. There were several smaller holes nearby suggesting that the strike separated upon leaving the mast.

The practice of tying all the metal bits together is called bonding. In aviation if you don't bond everything together the strike can jump across rudder bearings effectively welding them in position.

So the basics of any plan require all the metal to be bonded together. Secondly the energy needs a path to ground. It will take the easiest path to ground so the path you provide has to be low resistance, hence large diameter wires and copper plates and so on.

I read that one argument for not bonding to the keel is that a less resistant path may exist through the hull of the boat rather than across corroded keel boats. That's why the plate on the hull is recommended because the water is the closest path to ground and you are trying to make it also the least resistant.

The heat generated by a strike is important. This is why it is especially critical that filled keels and foam filled hulls not be used as grounding planes. The heat expands any moisture inside and we all know what happens when water heats up.

This is exactly what happend to the J24. Several of the smaller holes look like "explosion" holes. We surmise that captured moisture expanded and blew out. In fact event the main hole showed very little signs of arcing or burning.

I personally think the likelihood of a strike is tiny. But so is the likelihood of a sinking at sea and no one would consider a crossing without a lifeboat.

It's expensive but If I go across an ocean I will have a properly bonded boat with a low resistance path to ground.

[schoonerdog]

I would think doing something like 44 cruising cat recommends, take a big 0 gauge cable straight from the bottom of the mast down and through the drain hole in the anchor locker to the water with a large plate at the end.

[Alan Wheeler]

The science behind electricity and lightning strikes is extremely advanced. As an "airplane" person I am very familiar with the subject as relates to aviation. Commercial airplanes are struck all the time - everyday! I am somewhat bemused(?) by the boating community where there is a tremendous amount of pseudo science and old wives tales. Electricity is very predictable.

In how to protect Aircraft, that maybe true. In understanding electricity, that may also be true. In lightening strikes to ground sources, that is absolutely untrue. Plus to add, it is not JUST the electrical path that is the concern. The ability to condute and electrical flow to somewhere is very simple. But in a lightening strike, we have many aspects other than just an electrical flow, that majorly differ between each and every strike. The magnetic feild is just one of them. RF energy is the other. A bolt of lightening is complex. It is both AC and DC. It is RF. It has a magnetic feild. It is emense heat. It is an instantaneous flow of extreme high current and voltage. It causes any "insulator" in it's path to become a dielectric causing it to become a capacitance. This is one of the single most factors in seeing strange effects of high frequency energy and static energy bouncing and reflecting and defying simple electrical theory around the insides of what most would deem an insulator, being the inside of a plastic boat.
The ability to protect a metal envelope as in an aircraft is easy. The ability to protect a boat that is on the strikes path to ground is very different.

[Viking Sailor]

Originally Posted by Viking Sailor

Does anyone have first, second, or even third hand knowledge of a Dynoplate failing or exploding due to lightning?

Well it has been two days since I posted this question and there has been no response. I am also a little surprised at the lack of interest in this subject. As of this posting there have been only 248 views. Strange! You would think that as a real hazard to crew there would be more interest. Especially since there is sufficient knowledge to mitigate the risk to the crew from a lightning strike.

While we wait for Cruisingdad to check his source for an answer to the original question I will pose a new question.

Has anyone with a Dynoplate installed been hit by lightning?

[Pblais]

Has anyone with a Dynoplate installed been hit by lightning?

I have one and have not been struck. My neighbor with a bottle brush has been hit twice (both times in the slip a few boats down from me). I think it is a myth to assume that lightning strikes have a lot in common because they take many forms, shapes, and intensities. They don't all strike the top of the mast or any place else in particular while you might expect that they do. Once struck the path is never all that logical after the fact so the pattern of how they work is never always the same and not all that similar.

If you are looking for evidence that having a dynoplate is dangerous then I'm convinced you'll not find that either. I'm sure the dynoplate manufactures could not cover up that fact.

I'm sorry you were unable to find the answers to your lightning questions here but there are not many answers any place I've ever been either. Some things are not well understood.

[Cruisingdad]

Viking,

If you feel comfortable with using the plate as a ground, do it. It is your boat. I will ask Valiant this weekend about their experience. However, should they say "yes", how do you know it wasn't just a fluke? SHould they say NO, does it mean it has not or cannot happen? Thier comments will hold little value in determining the real potential for the plate popping.

Given the very small number of boats with plates that are grounded and have been hit (and of those that have taken it through the plate, I would not put a lot of credence in it either way. I will say, to this sailor perhaps, the logic behind it makes sense. THere have been many write-ups with the same conclusion, one of which I posted as a link above.

It is not to sound argumentative, but I will put it this way: Ever been to a gas station where someone was filling up their car while smoking? I have, several times. Never seen anyone blow up though, depsite all the written warnings and signs everywhere. However, just because I have not seen someone blow up does not mean it is a good idea. The potential is there and it is real - however small the chances, and even though no one on this board has ever sen it.

Just my thoughts. Still, do whatever you feel comfortable with. It is your boat, your system, your life, and your money.

- CD

[JusDreaming]

we took a direct hit on July 26 of last year. No dyna plate on the boat. But it fried everything. Including my wife's spinal chord stimulator (like a pace maker). She had her foot on the compression post. It blew the water out of the batteries,it fried a laptop that was sitting on the table connected to nothing. It blew the antennas off the top of the mast. You name it and it zapped it! I was happy for marlon thru hulls, as no hull damage happened! And I too am surprised that there is not much interest!!!!!!!!!

[Pblais]

And I too am surprised that there is not much interest!

The topic comes up on a regular basis but it's a topic that while there is interest there are few answers. Since you were aboard and saw the events you describe, your interest is highly motivated, but it's not very common in the sense that everyone has had it happen or knows someone that has had it happen to.

I have more lightning stories that are land based and they offer little in explaining lightning any more than lightning on the water explains lightning in general either.

The stories about blown through hulls are very rare but very possible. With enough power anything is possible. I would not assume Marlon through hulls are less prone. When you consider that the ability for a spark to jump across a gap is proportional to the power it becomes moot to assume a lightning bolt that came from the clouds could not go any place inside any boat of any proportion. In this sense there is little you can do to assure a solution to the potential lightning problems any more than you can know the weather with 100% certainty. I think your ability to predict weather is far far better than lightning and I don't think weather prediction is anything that great.

I think the "lack of interest" is more a matter of there are great risks associated with sailing the sea and dwelling on them would be to invite disaster. I don't personally see it that way but many do.

With Cruisers Forum you get what you get and you can have a refund if you like. We are only what members decide to make of it. We only have 83,000 members and they all don't show up on a regular basis. It might be a good thing too .

[Ex-Calif]

"The ability to protect a metal envelope as in an aircraft is easy. The ability to protect a boat that is on the strikes path to ground is very different."

Trust me protecting an aircraft and 400 occupants is not easy or taken lightly. The lightning still follows the same laws of phyisics and is still looking for a path to ground. The extensive use of composites in aircraft have made them very similar to boats in terms of the problems associated with protection

The heat, dielectric effects, RF etc. all occur in aircraft as well with arguably a lot more sophisticated and sensitive electronics.

Bonding oll the equipment and providing a low resistance high capacity path to ground is still the key to surviving lightning strikes.

In casual observation I see a three pathologies.

1 - Lighting is a vixen that can't be predicted. The chance of getting hit are so remote you are better of just hoping for the best.

2 - The mast is stepped to the keel so that oughta do it.

3 - Every piece of conductive metal is bonded to every other piece of conductive metal with large copper wire and the is all bonded to a plate on the hull.

I'm not trying to be argumentative at all but if one is serious about avoiding damage caused by lightning strikes step one is a complete bonding system.

Here's an interesting discussion about creating a Farraday cage as a system of protection. This seems pretty intuitive.

Marine Lightning Protection Inc.

[44'cruisingcat]

But the aircraft isn't the path to ground. not if it's flying anyway. A boat is actually part of the path to ground when it gets struck. Effectively the boat is PART of the ground.

[Ex-Calif]

"But the aircraft isn't the path to ground. "

Beg to differ - Anything in the way of the lightnings path to ground is part of the path to ground.

This is a screen shot from a video capture.

[Viking Sailor]

Originally Posted by Pblais

I have one and have not been struck. My neighbor with a bottle brush has been hit twice (both times in the slip a few boats down from me).

Interesting! Do you know if your neighbor had a Dynoplate.

Originally Posted by Pblais

If you are looking for evidence that having a dynoplate is dangerous then I'm convinced you'll not find that either. I'm sure the dynoplate manufactures could not cover up that fact.

I spent about half a hour trying to find out who makes Dynoplates. It turns out that it is Marinco under the brand name of Guest. Follows is a list of their product features:

Use with SSB radio
Improves performance of electronics and reduces RF interference
Offers the best path for hull bonding without long runs of copper foil
Equivalent to 100 square feet of copper foil
Provides a direct, low resistance path for improved lighting protection
Deters electrolysis and galvanic corrosion
Sintered porous bronze sphere construction for maximum conductivity in a compact size
Low drag, non fouling shape
Easy to install
Conforms to ABYC standards
Easy to clean w/wire brush

You would think that they wouldn't put in a lightning protection feature if they were getting reports of Dynoplates exploding.

Originally Posted by Pblais

I'm sorry you were unable to find the answers to your lightning questions here but there are not many answers any place I've ever been either. Some things are not well understood.

Thank you! Sometimes the best way to understand something is to ask a few simple questions.

Originally Posted by Curisingdad

Given the very small number of boats with plates that are grounded and have been hit.....

I've had my Dynoplate for 20 years. I have the impression that Marinco sells a lot of Dynoplates per year. If you figure between 4 and 10 boats hit per year I'm not so sure these numbers are that small.

Originally Posted by Pblais

With Cruisers Forum you get what you get and you can have a refund if you like. We are only what members decide to make of it. We only have 83,000 members and they all don't show up on a regular basis. It might be a good thing too .

I'd settle for 1%.

[Alan Wheeler]

Viking, doing a search may also help. This subject has been very popular in the past. There is a lot of information in the archives.

Ex-Calif, I am not being argumentitive either. But firstly, the aircraft is a large surface area of conductive metal. Boats, except for steel, are not. I have also heard of aircraft that have crahsed due to lightening strike, so aircraft aren't totaly bulletproof....I mean lightening proof either.
It has also been proven that the "cone of protection" idea on boats does not work. it's simple maths and Ohms law. You are trying to conduct a few million Volts and amps to somewhere. Even the slightest resistance in it's path sets up a potential difference of hundreds of thousands of Amps and Volts. The only way you can conduct ALL that current to earth is via a sufficient size super conductor. Something that is still not a reality in the realm of boat masts.
Then there is the electromagnetic field generated. This sets up EMF's in anything conductive. It doesn't have to be in the main currents conductive path. If it is electronic, it is toast, even unplugged. The only safe place is inside a very good farady cage. The best place on a boat is inside the gas oven. Although that even has it's limitations.
The only total effective way of protection is stay away from thunderstorms.

[Ex-Calif]

"But firstly, the aircraft is a large surface area of conductive metal. "

Once again, many aircraft are not metal. In fact the 787 and the A350 will be almost entirely "plastic."

"I have also heard of aircraft that have crahsed due to lightening strike, "

I did a quick search of the NTSB database and from 1999 on there are no records af any commercial aircraft losses frm lightning strikes. Lot's of lightning strikes reported with temporary loss of control in some cases but no aircraft losses or fatalities.

All of your discussion about EMF, circuit resistance and transmission of the current is exactly the same in an airplane.

In the interest of not diverting the discussion from the Dynoplate topic any more I will rest.