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Old 05-01-2011, 16:58   #1
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Lightning Protection

I have been reading the how-to books for upgrading old boats, and many give recommendations on how to design/install lightning protection for a sailboat. For my old boat it might be tricky, as I have an encapsulated keel, so to follow their rules, I would need to add an external metal strip or plate to dissipate the strike into the water.

This complicates things for my upgrade project, so I am not certain I will do it right away. I took a walk around the marina, and I was surprised to see that only about 1 in 20 boats even has a lightning rod/protection (maybe less).

So what's the deal...is this important to have or not? My future cruising plans do not include crossing oceans, but a trip across the Gulf of Mexico is within reason (and I assume there is a fair amount of lightning in the gulf).

Any comments appreciated.
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Old 05-01-2011, 17:05   #2
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Well us 'Ole Timers' just attach a piece of chain port and stbd to the mast shroud and let it hang in the water...
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Old 05-01-2011, 17:13   #3
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Quote:
So what's the deal...is this important to have or not?
There is a lot already posted on CF about it and the custom search tool should get you more than you can digest. Over the past 7 years I will say there is nothing breaking on the subject. Bottom line. A big direct hit will with some certainty kill you. It can be a small jolt and you'll live or a big one and the deck stain won't come out.

Following basic best electrical and grounding practices will assure a good ground plane for an HF radio as well as some lightning protection. If it can jump from way up in a cloud going through your boat is not even an inconvenience. Most of the definitive claims can't be backed up. There is a limit on what anyone will spend. Experience that is more personal tells me not being plugged into any shore power helps avoid inducted lightning damage. Being plugged in is in my estimate the worst thing you can do. It means any local induction can have your address.

Induction could be called a near miss. On a big strike, close is good enough to cause you damage by induction. The magnetic field can induct a large side jolt a few hundred yards sideways quite easily - or not.
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Old 05-01-2011, 17:25   #4
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The following is an interesting site, with some views contrary to existing theories
Marine Lightning Protection Inc.
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Old 06-01-2011, 11:13   #5
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It is to drain static charge that is accumulated arround the building.

Simply run a wire fron the top. Dig a deep hole in the earth and place the wire in it.
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Old 06-01-2011, 11:37   #6
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Originally Posted by Marinheiro View Post
The following is an interesting site, with some views contrary to existing theories
Marine Lightning Protection Inc.
I wouldn’t call Dr. Ewen Thomson an “outsider” in lightning protection (theory or practice) circles. He's highly respected in the field.

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It is to drain static charge that is accumulated arround the building...
False! One cannot equalize the charge between a boat or building, and the entire environment (water/earth & air) surrounding it.
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Old 06-01-2011, 11:52   #7
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Originally Posted by StringBimini View Post
This complicates things for my upgrade project, My future cruising plans........

Any comments appreciated.
I thank you for the "Any comments appreciated".

I think you are CRAZY to go to sea without lightning protection! You should also install Floating Shipping Container Proteciton and Randy Whale Protection. I have bought Storm Protection but it can't fit on the foredeck so I've rigged it above the dinghy davits next to the Water Ingress Protection Device, alongside the Emergency Electrical System - Thats also where I store my Paper Charts. **Do NOT tether the goat to the paper charts!**



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Old 06-01-2011, 13:07   #8
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Being hit by lightning is actually quite possible, over say 40 years of cruising in areas fraught with thunderstorms. Your chances are at least 1 in 3 of being hit, in the above category. (This is based on extensive studies, not just my opinion). I have dozens of friends or acquaintances who have been hit, and a boat right next to me has been hit on three occasions. This is just the strikes that I know of!

The research done by the University of Florida about 20 years ago, on a Federal grant, was the most complete I've read. Basically, ground the mast well with like... double ought wire, as straight down as possible to a 2 sq' (min) copper ground plate, and attach in as many of your shrouds / stays as possible, with #6 wire. Ground the engine and large metal as well. (Cuts down on side flashes).

They found that linear edge of ground was more important than just area, so a plate 1' X 2' was not nearly as effective a ground as the exact same "area" in the shape of a 1" wide narrow strip going down the length of the hull. But this is VERY impractical for most boats... so, we just ground them any way we can. Just, NOT with a "Dyna plate". They are useless as a lightning ground, and have been known to explode from a strike!

Lightning rods & Bottle brushes... The rod is an essential part of the system. The "brush concept" has been proven statistically to work on cell towers, and this is why every cell tower in the world has one. Weather or not this principal carries over to boats is unknown, however there is "0" evidence to indicate that they make your odds worse.
I didn't mind a couple hundred more $ to "possibly" improve my odds, even if only slightly... so, I have one. (we have over 50,000 hours of labor in our boat!)

Remember, anyone who talks in absolutes about lightning, is full of it. The idea is to "improve your odds", that's all we can do. The basic ground system mentioned should go a LONG way in preventing the mast from being driven through the hull.

For electronics, there are extreme measures like a "Faraday cage" but who goes that far? We have wrapped up a portable GPS in a roll of foil, It just might help with inductance. Then, there is unplugging antennaes... I used to do it, but it just became too much effort.

In a real hit, you may well loose ALL of your electronics, even if properly grounded. The grounding system is mainly in hopes that the strike doesn't put a LARGE hole in your boat.

As for people... Obviously stay away from metal. This may not be easy. I have been at the wheel, 3' from our mast, on the ICW... with NO place to pull over, and repeated strikes within 100' all around! (This is in white out rain, and 45 knots of wind). I put on rubber gloves and boots, crouched down, and stood on the balls of my feet! I had read of this being useful... This MAY have improved my chances .5%, I don't know. I was so scared I would have whistled Dixie if I thought it would help!

I agree 100% with PBLAIS, inductance will get you under a "close strike" situation. I have had the boat's mast 200' away take a direct hit, and MY battery charger was FRIED! It smoked up the cabin. (Altogether, I've been through 5 battery chargers from spikes down the line during a storm, or inductance).

One thing I do take the trouble to do, is unplug from the dock in a storm, (not just trip the breaker)! Otherwise, if it hits the transformer 1,000' away, it can ruin lots of your electronics.

Just like life in general, I do what I can, about what I can, and hope I'm lucky about surviving the rest.

With lightning, doing nothing makes no sense at all! At least a basic ground system is called for, as it is cheep and easy insurance. Not that you will not be hit, but that you might survive. It vastly improves your odds.

Mark
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Old 07-01-2011, 06:09   #9
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Merrydin1.

Very true! A well insulated, properly lightning protected, ALL metal hull, is by FAR the safest in this regard. M
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Old 10-05-2011, 22:39   #10
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Re: Lightning Protection

Hi Mark,

Great write up and i certainly agree. Can i add the necessity to also protect electronics. For this reason i am calculating that a type of caravan auto plug principle for all electronic wiring prior to DB board.
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Old 12-05-2011, 22:54   #11
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Re: Lightning Protection

In reply to PB and Mark's posts i wish to share a bit of planning i did some time ago. One point was that if i cannot prevent a strike maybe i can guide it to a certain degree. In order to do this i planned to extend a thick copper wire about 1 metre above my mast head right down to the mast foot plate. From the foot plate i placed a thick copper wire to the gaurd rails both sides.
From the foot plate through the super structure and split two ways to two copper ground paltes situated on both hulls. These ground plates were suppose to be 5 mm thick by 70mm wide and about 2.5 meter long. The groun plates were glassed in on the hulls to smooth things out.
All wiring leading to the DB were rerouted to a type of caravan fitting that can be unplugged in heavey weather which is then plugged into a dummy plug that feed back to the cable from the mast foot plate creating a circle. The engine batteries were isolated from the batery bank and the engines were also connected to the copper groundplates with a long thick cable that lead to the cable that go through the super structure to avoid unnecessary holes in the hulls. This might be overkill but i guess when one's in trouble with the weather overkill does not count.
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Old 23-05-2011, 16:29   #12
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Re: Lightning Protection

Mark,

You have given me pause on my invitation to post "any" comments. Haha, words have power, and must be wielded with care.

Thanks for the heads up. Oh yes, how are the fresh eggs from the chickens?
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Old 23-05-2011, 18:00   #13
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Re: Lightning Protection

Quote:
Originally Posted by Mark Johnson
... Lightning rods & Bottle brushes... The rod is an essential part of the system. The "brush concept" has been proven statistically to work on cell towers, and this is why every cell tower in the world has one. Weather or not this principal carries over to boats is unknown, however there is "0" evidence to indicate that they make your odds worse...
The “charge dissipation” theory that supports the bottle brush concept has been thoroughly discredited.
A proper lightning air electrode is either a blunt/rounded or pointed (Franklin) ROD.

Google "Lightning" & "GordMay" for NUMEROUS references.
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Old 23-05-2011, 18:49   #14
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Re: Lightning Protection

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Originally Posted by GordMay View Post
The “charge dissipation” theory that supports the bottle brush concept has been thoroughly discredited.
A proper lightning air electrode is either a blunt/rounded or pointed (Franklin) ROD.

Google "Lightning" & "GordMay" for NUMEROUS references.
Gord you are incorrect on this one. First off, my lightning rod IS a solid (app 24") rod, with a single 1/2 dia down to 0 Dia cone/point on the top, as you correctly said it should. It also, (as an option), has thousands of little bristles/wires that stick 1" out the sides of the rod, like a "bottle brush".

These wires and their claimed "charge dissipation" function do not in any way detract from the fact there is a proper standard lightning rod in place at the top of my mast, so if they don't work at avoiding a strike, it's irrelevant. The rod/mast/00 wire/ and large copper plate, will give it a direct path to ground.

The statement that you made of "being totally discredited"... depends on WHAT you mean. The theory has not, it's sound, and in fact, their are similar charge dissipatiors on every cell phone tower in the world. So, the principal in general, has NOT been discredited... At least not on cell phone towers.

What seemed like an extreme reach to me from the get go, was the manufacturers claims. They claimed: "These will prevent a strike, or they will pay for the damages"! WAY too much enthusiasm for their product. Perhaps THIS STATEMENT on their part has been discredited, I don't know, but it should. It's too absolute when talking about something as fickle as lightning. All we are trying to do here is improve our odds!

Now, this was 16 years ago, and I don't know if they are still around, but all I ever "believed" about my lightning rod's "extra side bristles", was that they MIGHT lessen the odds just a bit, and if not, they would not hurt the standard lightning rod's normal function.

My anecdotal observation from living aboard for 12 years in lightning prone areas, and having hundreds of strikes within 1,000', a good number within 100', and the boats right next to me actually HIT on a half dozen occasions... The gizmo might improve my odds a bit, as I have not been hit. I could also just have gotten lucky, I have no idea?

When I mentioned my " single point lightning rod" as being an integral feature of the system, it is sound advise. I neither recommend nor discouraged the hybrid type that I have, which includes the little side bristles, although there is absolutely NO evidence that they hurt anything, so if one wants to pay extra for the chance that they may improve their odds, there is nothing to loose if they don't work... The lightning rod will still deliver the charge to ground.

There are a lot of "unproven things" that I am willing to try to improve my odds across the board, as long as they can't possibly hurt them... This was but one of them.

M.
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Old 24-05-2011, 02:52   #15
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Re: Lightning Protection

See my post #17:
Bonded vs Unbonded Boats

Many Cell Towers don't even utilize conventional Franklin Rods (though all are grounded), and I doubt many (if any) use bottle brush dissipaters.
I don't know if the bottle brushes interfere with your central rod's effectiveness, or not - but they CERTAINLY add nothing to your lightning protection (actually, mitigation).
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