Visit our Popular Forums

team karst · 20-05-2022, 16:24

The hanging wire catenary is not doable for us. But, the concept of divert and ground is doable to at least protect a plastic boat. The issue does remain of sensitive electronics protection. Just the large magnetic field induction is a tough one.
The strike % for sailcats is higher. Some think its because so many live in partial dock isolation, due to beam.

Frankly · 20-05-2022, 16:24

Rafting up your motor boat with a properly grounded monohull (say 50+ ft mast). Lightning protection "as good as it gets" on the water.

I was crossing the Okeechobee WW once in July. Lightning from Hell all around. Hid under a transmission line for about an hour. Pretty safe hang out also.

garyfdl · 20-05-2022, 16:51

Quote:

Originally Posted by s/v Jedi

sorry but the word REDUCES means that there are less strikes.

Quote:

Originally Posted by franksingleton

You can believe whatever you like.

Actually? I think we're pretty much in agreement. You guys say 'it might work' I say 'it might not'; is the glass half full or half empty?

The reason I have a particular interest in the subject? I hope the step the mast on my new-to-me Watkins in the next week or so. (It'd be sooner if I stayed off these boards.) While the boat has a bonding plate (apparently too small by today's standards) I haven't seen anything that looks like a lightning protection system.

Now I'm not the biggest stick in the harbor, or even on my dock (although there are probably some around who might disagree with that statement.) So I'm guessing the prospects of my getting hit aren't extreme. But I hate the idea of winding up like that poor 27' Erickson that had the through-hulls blown out and sank at the dock.

catsketcher · 20-05-2022, 20:32

I think one problem with lightning is that it is mercurial. One instance I recently read of was of a steel boat where the lightning ran down the mast and then up the deck and through the bow roller and into the chain, melting the chain.

But a steel boat should be the ultimate lightning conductor and the straight path would usually be straight down the mast and into the hull. So lightning often hasn't read the physics book on how it should behave.

As a Science teacher I play a lot with static electricity. The Van De Graf is a great tool that works best on dry days, when the charge does not leak away. Same with charged rods used in experiments. Charge leakage occurs with all statically charged objects. The idea of the brushes (I think) is to accelerate this leakage.

As for needing to have a large and straight strap to reduce the effects of the mast being charged - I don't think this should be necessary. In pre-lightning conditions, the mast will develop a charge by induction. Electrons will run up or down the mast depending on the charge of the clouds or atmosphere above. Having the mast grounded with even a small wire will allow electrons to bleed onto or off the masthead, reducing the induced charge. The current will be very low to provide enough ground to neutralise the masthead so a small wire connected to a ground plate should be fine.

Not grounding the masthead may allow the masthead to become oppositely charged to the clouds above - increasing the electro-potential between the mast and clouds. Again, no contact is needed to get the mast charged. The best way to bleed electrons off or onto the mast is something I would need to look into, but the most basic Physics would suggest that having a mast with a neutral charge would be better than one with an induced opposite charge if you don't want to be attractive to lightning discharges.

**s/v Jedi** · 20-05-2022, 21:29

Quote:

Originally Posted by franksingleton

That is not how I understand the Lightningmadter works. The mast has to be earthed but not necessarily with a massive wire. It can be to the engine block or to a sacrificial anode. The principle is that it allows the charge to leak away and, so, not build up a charge at the masthead and so reduce the chance of a strike. On a yacht, the lightning rod principle is a bad idea. You do not want a strike to b;ow a hole in the bottom of the boat. The idea of trailing chains over the side is untenable in the average yacht. I have yet to see a better solution than the LM although I agree that may well not give 100% protection.
Does anyone know of a yacht with an LM that has been damaged by lightning?

Your understanding is correct and would suffice if the LM avoids every threat of a strike…. but it doesn’t. When there is no suitable alternative for the strike, you can reduce the electric field as much as you want but it will always be bigger than that of the water surrounding you… so if you are close enough, you get the strike.

Once you get the strike, you must guide it to the water safely. Our boat came standard with a bonding plate under each mast, connected with a straight up and down AWG6 cable, no sharp bends. It worked perfectly during the two direct strikes our boat got before we bought it: still frying electronics but apart from evaporated masthead antennas and wind sensors, no damage to fiberglass.

**s/v Jedi** · 20-05-2022, 21:32

Quote:

Originally Posted by team karst

Ive seen a pix of a melted LM.

Yes there have been multiple reports. None of them were grounded… one I saw was screwed into a wooden mast like if it was some kind of magic totem device

EDIT: and then there are reports from boats struck by lightning even with a correctly installed LM. I happened to be in the same anchorage as one of those cases and after talking to the folks of that boat, who told me the LM as well as everything else at the masthead was untouched, thought the strike may have hit the insulated backstay used as SSB antenna. Upon further investigation, the automatic antenna tuners was completely burned out, as was the copper strap connecting the tuner to boat ground.

This actually proves LM worked but also that antennas like insulated backstays must be grounded during lightning storms.

franksingleton · 21-05-2022, 01:29

Quote:

Originally Posted by Galumay

Not really relevant to the boating scene though, unless you can convince several friends with yachts with higher masts than yours to sail in a group surrounding your boat where ever you go!

What is relevant is that before fitting theLM, we used to get a build up of static when storms were nearby or even just a stronger electric field than normal. We have had none since in about 20 years and 30,000 miles cruising the Med and W Europe. That is what LM say should happen i.e. it prevents build up of a charge. Whether or not that saved us from a strike, I cannot say. I just know that strikes were closer than we ever had before or since.
Whether anyone takes my advice and gets one is a matter of your own judgement. For my part, it is a no-brainier.

team karst · 21-05-2022, 08:31

I am more inclined to believe the LM moves the emission of electrons to its sharp points, away from the less intense places. If you were at the top of the mast listening, I think it would be hissing.
In any case, I cant wrap my head around the notion of relieving the local earth (or sea) of charge. Lightning itself is that relief. And its more than a few Coulomb’s.

Frankly · 21-05-2022, 09:07

Lots of years back (in my misspent power boat life) I had a pair of aluminum Perko outriggers. My lightning approach was to lower the port outrigger and connect a galvanized bucket on a heavy jumper cable to the still vertical stbd outrigger. The bucket (kind of a poor mans washdown system) was on a rope and hung in the water from the base of the outrigger.

On two different occasions anchored at the end of a typical Florida Summer all Hell is breaking loose thunder storm the sound of frying bacon could clearly be heard emanating from the top of the stbd outrigger. The sound would wax and wane in intensity as I set quivering in the cabin. Never a strike and the top aluminum tubing was probably 1/2" in diameter so not particularly sharp. Had this been at night, I suspect St Elmo's Fire would have been clearly visible.

IMO the Lightning Master probably does not hurt, but like a lot of things in life, one egg in my lightning basket is a well connected mast. Redundant copper conductors, four large SB bolts and a large 1/4" copper plate.

Frankly

Can't post the picture, if interested in details click on my name I think.

**s/v Jedi** · 21-05-2022, 09:37

Quote:

Originally Posted by team karst

I am more inclined to believe the LM moves the emission of electrons to its sharp points, away from the less intense places. If you were at the top of the mast listening, I think it would be hissing.
In any case, I cant wrap my head around the notion of relieving the local earth (or sea) of charge. Lightning itself is that relief. And its more than a few Coulomb’s.

Before lightning bolts go, leaders are formed to guide (conduct) it. The LM works during the leaders forming phase, not when the strike happens; everything is signed & sealed at that time.

Bowdrie · 21-05-2022, 09:56

Jeepers Batman, after reading this thread I've arrived at 2 conclusions.
1, Keep a desk handy, per post #56.
2, Never go boating in the Florida>Carolinas.
I do have a "mitigation" scheme but still from time-to-time wonder how much, (if any,) effectiveness it would/might have.

team karst · 21-05-2022, 11:55

Its funny. Lived in SFL for over 5 decades, boating, outside antennas, etc. and never hit by lightning.
Year two in W NY, take a direct strike to my antenna hung between two trees. That was an area getting so few thunderstorms, folks at work went to the windows to just stare at them.

Frankly · 21-05-2022, 12:07

After the Okeechobee WW episode I pulled up to the Port Myaca Lock, the thunder storm now having moved out over the lake, and called the lock operator. "I am not sure I want to be out in that lake right now". " I wouldn't be out there either, was the return". "Can I tie up to these dolphins for the night". "That is why they are there". Before heading home for the night the lock operator called me on the radio to tell me that the morning shift would be in early and would lock me through. One other little tid bit he dropped on me, "down here we have mosquitos as big as that boat you are on" (32' IP) . We took his word for it and had our evening cocktails down below.

Next morning locked through and motored across the lake in dead calm.

Living in Florida is not for the faint of heart.

Frankly

franksingleton · 22-05-2022, 00:35

Quote:

Originally Posted by team karst

I am more inclined to believe the LM moves the emission of electrons to its sharp points, away from the less intense places. If you were at the top of the mast listening, I think it would be hissing.
In any case, I cant wrap my head around the notion of relieving the local earth (or sea) of charge. Lightning itself is that relief. And its more than a few Coulomb’s.

From my imperfect understanding of the LM, instead of a charge building up,on a single point, it is diffused among many points. That allows a continuous seeping away of charge. There is always an electric field from atmosphere to earth so the leak is a continuous process. From the behaviour of our ST60 wind indicator it seems that is what occurs. Whether this gives 100% protection is probably unlikely. Maybe we were lucky. I do not know. I just know that the LM does what the makers claim. If that gives some reduction in getting struck then, to me, it is worth the low cost.