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Old 10-03-2013, 11:45   #16
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Re: Lightning Dissipator -- Any Good?

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Originally Posted by Dockhead View Post
. Does anyone know whether they actually work or not? Worthwhile?
In one of the previous 354,221,87683,9998776444277 threads on the exact same subject we had an insurance guy come on and say that they did a check of claims and there was no statistical difference if you use a lightning rod or do not.

But I don't have good enough Internet to try a search for the thread.

Like Elvis being alive, the CIA running the White House and Guns are Good, the belief if in the eye of the holder (!)..... As most who use lightning rods are Americans...


Go figure!


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Old 10-03-2013, 11:54   #17
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Re: Lightning Dissipator -- Any Good?

NASA which has some really tall and really expensive stuff in the biggest lightning strike state and some really brainy people (yes they are rocket scientists) does not use them. their research shows that a lightning rod with a 3/16" diameter rounded tip, not pointed, is best.
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Old 10-03-2013, 12:07   #18
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Re: Lightning Dissipator -- Any Good?

Dockhead,

About 20 years ago these brush things appeared on the scene. Initial field experience suggested that they might work. However, after 20 years the statistics suggest they do neither harm nor good. I do not have one of the brush things on my boat.

The gas arrestors can help save your VHF or other coaxial fed equipment but they do not protect other things. They assume the DC and AC wiring is protected by some other means. Look at the arrestor you are considering. It should have a bolt on the side for connecting a ground strap or wire. This strap or wire is to be installed by the user and should be extremely short (<1M if possible) and directly connected to something immersed in salt water (e.g. keel or through hull). In cell tower installations these arrestors will be mounted to a conducting plate in the wall where the coax cables enter the building. This plate will be grounded with a low inductance connection to earthing rods. They are not guaranteed to work but they often do work. Sometimes after a lightning strike the arrestor will be destroyed or damaged so be sure you remember where they are installed and check them periodically.

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Old 10-03-2013, 13:31   #19
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Re: Lightning Dissipator -- Any Good?

Lego works too!s/v Bella Star: How to Prevent a Lightning Strike
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Old 10-03-2013, 13:49   #20
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Re: Lightning Dissipator -- Any Good?

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Originally Posted by Dockhead View Post
Where I sail, one often sees these:

Boat Lightning Static Dissipater

On people's mastheads. Does anyone know whether they actually work or not? Worthwhile?
Gord & MarkJ are right. Even if the dissipators work, your boat has no protection from side flashes. So a neighbors boat might get hit and be fine, but your gets hit by the side flash, taking out all your electronics. That's just the way it is.

If you dig around enough here you'll find a post by an academic that started his own lightning protection company for boats. I also remember seeing it in one of the sailing magazines. Oh, wait, here it is


Coincidentally, most boats get hit in a marina. Is that:

a) just statics as most non-trailered boats spend most of their time in a marina?
b) due to the fact you have a bunch of high metal objects all bunched together?
c) irrelevant as you can't exactly model where lighting will hit anyway?
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Old 10-03-2013, 15:15   #21
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Re: Lightning Dissipator -- Any Good?

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Standard equipment on Jetplanes.
Static wicks on aircraft are not intended to protect from lighting strikes. They're supposed to dissipate static buildup that interferes with radio communications.
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Old 10-03-2013, 16:19   #22
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Re: Lightning Dissipator -- Any Good?

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Originally Posted by s/v Jedi View Post
1. First thing you must do, if you do anything about lightning strike management, is create a bonding system with special arrangements for lightning strikes. This means a bronze plate under the boat where the mast is and then a thick AWG6 or better cable from the base of the mast to this plate without any tight bends. This provides a path to the water for a charge without punching holes through the hull or through crew members towards other metal or plumbing etc.

Yes, if you have a cat you're in trouble :)
Au Contraire. We have a 0000AWG wire connected by a brute of a fitting directly to our mast, terminating on the other end in a tinned copper electrode containing over 6' of edge surface and hanging straight down from the mast into the water.

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Old 10-03-2013, 16:34   #23
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Re: Lightning Dissipator -- Any Good?

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Originally Posted by sanibel sailor View Post
NASA which has some really tall and really expensive stuff in the biggest lightning strike state and some really brainy people (yes they are rocket scientists) does not use them. their research shows that a lightning rod with a 3/16" diameter rounded tip, not pointed, is best.
Those are lightning rods and not dissipators - two different intentions as to function. Lightning rods do actually work and are used to take a strike and guide it to a better place (Nick's antenna serves that purpose on his boat ). Rounded tips have been found to be more efficient than pointed tips for taking a strike. Dissipators theoretically help prevent strikes by bleeding off electrons that may help to induce step leaders.

However, if NASA do not also use dissipators, then that speaks volumes in itself.

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Old 10-03-2013, 16:43   #24
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Re: Lightning Dissipator -- Any Good?

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Originally Posted by transmitterdan View Post
The gas arrestors can help save your VHF or other coaxial fed equipment but they do not protect other things. They assume the DC and AC wiring is protected by some other means. Look at the arrestor you are considering. It should have a bolt on the side for connecting a ground strap or wire. This strap or wire is to be installed by the user and should be extremely short (<1M if possible) and directly connected to something immersed in salt water (e.g. keel or through hull). In cell tower installations these arrestors will be mounted to a conducting plate in the wall where the coax cables enter the building. This plate will be grounded with a low inductance connection to earthing rods. They are not guaranteed to work but they often do work. Sometimes after a lightning strike the arrestor will be destroyed or damaged so be sure you remember where they are installed and check them periodically.
Ideally, one would use two of those - one at the antenna and another where the coax enters the building (boat). Ground the antenna one to the mast and the other to a keel bolt or ground plate, like you describe. Don't know about the through hull idea...

How do you tell when they are damaged and no longer conduct? Does the gas tube show physical damage? Doesn't seem to be any easy way to test them.

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Old 10-03-2013, 16:50   #25
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Re: Lightning Dissipator -- Any Good?

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Originally Posted by Dockhead View Post
I notice you are violating the rule that the dissipator should be the highest thing on the masthead -- do you think it's not important?
Not on Nick's boat. As is perfectly obvious from that picture, Nick is invoking the old Jedi mind trick on the lighting - "This is not the boat you seek".

Works on birds too, I hear...

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Old 10-03-2013, 17:35   #26
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However, if NASA do not also use dissipators, then that speaks volumes in itself.

Mark
Remember that I wrote that dissipaters do not prevent strikes. The strike will come but what will it hit? When you own all the gear and towers and assembly halls and buildings in the area, then you want a lightning rod that attracts the strike and leads it safe to ground. Makes perfect sense.

Now, with your boat, do you want to attract the strike? Do you own all the other boats, buildings, towers etc. around you? I do not so I try to camouflage myself so that the strike does not choose me. Also makes perfect sense to me.

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Old 10-03-2013, 17:39   #27
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Ekh, I have a cored hull, so no new holes or bronze plates for me.

On the other hand, I have 8 tons of lead keel, not encapsulated with anything but antifoul -- maybe that would work?
Yes you can connect to a keelbolt because you have external ballast. Do not connect AC ground to this, nor battery negative; just the base of the mast.

p.s. complain to your designer. Dashew put nice pockets into the laminate so that under each mast is a plate which is flush with the hull... very spiff.
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Old 10-03-2013, 18:34   #28
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Re: Lightning Dissipator -- Any Good?

I had one on my boat, and watched a boat next to mine take a lightening strike that caused $10k worth of damage. My mast was higher than his.

I decided to leave mine installed.
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Old 10-03-2013, 19:34   #29
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I had one on my boat, and watched a boat next to mine take a lightening strike that caused $10k worth of damage. My mast was higher than his.

I decided to leave mine installed.
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Old 10-03-2013, 20:28   #30
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Re: Lightning Dissipator -- Any Good?

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LMAO thank you.
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