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Old 07-08-2008, 20:06   #1
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DISSAPATORS-FEEL GOOD OR REAL GOOD

I am installing a dissapator on top of my mast for lighting strikes and was wondering how well they actually work at preventing serious damage by lightning. Does anyone know of boats that have had a direct strike and damage with a dissapator on top the mast? Are dissapators actually effective at preventing lightning strikes from wrecking havoc?
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Old 07-08-2008, 20:29   #2
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My neighbor has a dissipater. He's been struck twice. Seems to work well for me since I don't have one and have not been struck. He claims it was because he was plugged into shore power. The odds of being struck are so small that it's almost impossible to put real numbers to anything that prevents lightning. We have a lot of discussions about it already and you might want to look them over and make up your own mind.
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Old 07-08-2008, 20:53   #3
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My neighbor has a dissipater. He's been struck twice. Seems to work well for me since I don't have one and have not been struck. He claims it was because he was plugged into shore power. The odds of being struck are so small that it's almost impossible to put real numbers to anything that prevents lightning. We have a lot of discussions about it already and you might want to look them over and make up your own mind.
I did a search on the forum using the word dissapator and nothing came up but I will search lightning and I am sure I will get alot.
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Old 07-08-2008, 20:59   #4
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Old 07-08-2008, 21:00   #5
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I have a severe allergy to lightning.

Before I left on my circumnavigation, I installed two dissipators made by two different manufacturers on my mast. The worst lightning I have ever seen was in Singapore and the Malacca Straits at the start of the Monsoon. Five yachts were struck within a single week while we were there. We were not struck. Maybe we were just lucky.

We have had those dissipators up on the mast for fourteen years and so far our good fortune has held. I don't know if they do any good, but they make me feel better, so I guess they were worth putting up.
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Old 07-08-2008, 21:31   #6
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The worst lightning I have ever seen was in Singapore and the Malacca Straits at the start of the Monsoon. Five yachts were struck within a single week while we were there. We were not struck. Maybe we were just lucky.
Lot's of lightning here. Lot's of folks get struck. IMHO it's a matter of luck...
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Old 08-08-2008, 02:10   #7
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... Are dissapators actually effective at preventing lightning strikes from wrecking havoc?
No - dissipators (charge transfer systems) aren't effective in preventing, nor reducing the risk of a lightning strike.

CruisersForum Google search at:
Cruisers & Sailing Forum

“dissipator”:

ightning strikes/ avoiding them? - Page 3 - Cruisers & Sailing Forums
If you had a ligtning rod (there's another name for it..dissapator?) Start with a dissapator (lightninig rod) at the tippy top of the mast. ...
www.cruisersforum.com/forums/f55/lightning-strikes-avoiding-them-3138-3.html

Lightning? - Page 2 - Cruisers & Sailing Forums
I have one of the little ionic dissapator gizmos at the top which apparently did little or nothing to ward off this strike. The electrical circuits in the ...
www.cruisersforum.com/forums/f122/lightning-6012-2.html

Struck by Lightning/seeking advice - Cruisers & Sailing Forums
The top of the mast has one of the little brushes at the top; a so-called ionic dissapator. I've heard those little gizmos are of questionable value also. ...
www.cruisersforum.com/forums/f80/struck-lightning-seeking-advice-5331.html
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Old 08-08-2008, 03:16   #8
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They tried using the dissipators on the bridges in Florida (I'm not sure how many or which ones). The bridges apparently have a high incident of lightning strikes. Over a period of time they found that there was no difference in the number of strikes to the bridges with the dissipators, compared to the bridges without dissipators.

How can you prove that a lightning protection / prevention system really works? I'm with Paul that it's a matter of luck, and very small odds of geting struck.
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Old 08-08-2008, 09:25   #9
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So much is NOT known about the physics of lightning that anyone can have an opinion, and be right. Or wrong. But how do you tell which it is??? You can't.

Nonetheless, here's my opinion. There is soooooo much energy involved in the evolution of a lightning strike that a pitiful little bundle of metal fronds won't look any different to the lightning than the top of an unadorned mast.
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Old 08-08-2008, 09:36   #10
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Old 08-08-2008, 10:56   #11
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They tried using the dissipators on the bridges in Florida (I'm not sure how many or which ones). The bridges apparently have a high incident of lightning strikes. Over a period of time they found that there was no difference in the number of strikes to the bridges with the dissipators, compared to the bridges without dissipators.
The foregoing is quite surprising in that one of the members of our Yacht Club is an official with FP&L and he indicated that the company had good success reducing power-pole hits by adding bottle-brush charge dissipaters to them. Further, in recent years only the two boats at our club that did not have the devices were hit--one with a mast the same height as ours one slip away--while none of the other boats with the devices have. Maybe that's just coincidence but it doesn't seem so, eh?

FWIW...

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Old 08-08-2008, 10:56   #12
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Air is a relatively poor conductor of electricity. If lightning can arc across miles of air then it certainly can go right through your mast, which is an even better conductor of electricity. Given your mast conducts electricity better than the surrounding air, there is nothing that can be done to keep lightning from striking it...electricity follows the path of least resistance.

Given that, the best thing that can be done is to give lightning a really good conductive path to follow to ground. This means a wire from the top of your mast to ground, and even that is certainly no guarantee against lightning finding an alternate path and destroying things.
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Old 08-08-2008, 12:15   #13
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Thanks all for the nice replies. I tend to agree with the idea that dissipators are of questionable value but there are anecdotes floating around that support their use.
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Old 08-08-2008, 13:02   #14
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Thanks all for the nice replies. I tend to agree with the idea that dissipators are of questionable value but there are anecdotes floating around that support their use.
There are also anecdotes claiming that the checque is in the mail, and describing honest politicians, alien abduction, and Bigfoot (sasquatch) encounters.
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Old 08-08-2008, 14:08   #15
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There are also anecdotes claiming that the checque is in the mail, and describing honest politicians, alien abduction, and Bigfoot (sasquatch) encounters.
Sasquatch once struck my mast, but an honest politician claimed it would have been better if aliens put a check in the mail for it!...

Seriously, though, as David M said, empirical evidence says that the best thing you can do is give lightning an awful good (that is - low impendence) path to earth/ground. Right now, Ewen Thompson's research is about the best thing we have going, and his recommendations to adopt NEC-style grounding/bonding techniques to boats are being integrated into the latest ABYC recommendations: have a perimeter ground loop around the waterline, and bond just about every large metal object to it, a grounding plate/strip with large edge areas in the water, and electrodes/spark gaps tied to the perimeter to help encourage any "hot spots" to side flash to water rather than to internal metal objects or people.

It's expensive to do it right, so right now Beausoleil is incrementally getting there. We've got three ground plates/strips installed, and will slowly grow it into a perimeter ground loop. With everything interconnected with low-impedence wiring, there should be no "significant" voltage potentials between large metal objects. Hopefully if lightning does strike, the whole assembly will see a common voltage rise such that there's no dangerous voltages between parts of the boat. I.e., like a bird perching on a high-voltage wire, there won't be any dangerous voltage potentials. Let the whole assembly rise in voltage, not just any single portion.

Well, that's the theory, anyway...
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