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Old 10-03-2013, 21:12   #31
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Re: Lightning Dissipator -- Any Good?

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Originally Posted by colemj View Post
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.

Mark
The keel bolt is the best. A through hull might not be perfect but where lightning is involved there aren't any good solutions. Only progressively worse ones. If the through hull is not substantial then probably not a good idea.

It's hard to tell if the gas arrestors are damaged by visual inspection. Usually the VHF will not send or receive which is often the first clue. You can test them with an ohm meter. The center pin should be a short between both ends. The center pins on both ends should have infinite resistance to the outer case. Usually they fail short between center and outer case. Sometimes they fail open.

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Old 10-03-2013, 22:06   #32
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Re: Lightning Dissipator -- Any Good?

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Originally Posted by s/v Jedi View Post
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.
Don't rub it in. There are many more spiff Dashew tricks, besides that one, which you simply won't find on other boats. My favorite, though, is the no through hulls in the main hull volume.
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Old 11-03-2013, 02:42   #33
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Re: Lightning Dissipator -- Any Good?

The best think you can do for lightning protection is to have a good system to ground the mast. The main purpose of this is to conduct to ground a lightning strike in the safest way. A strike will often still do significant damage, but this system reduces the damage, particuarly the catastrophic damage that sinks yachts.

Many people fear that grounding the mast will increase the risk of a strike. In fact the opposite is true, but the effect is only slight.
The reasons are that a ungrounded sailboat mast builds up a static charge, this charge build up attracts some lightning strikes.

The main advantage of grounding is to dissipate the strike in the safest way, but the reduced static build up is also a slight advantage.

The "brush" fittings are designed to enhance this disipation (and concentration) of static charge.
It is well known this type of structure dissipates static charge (hence the use on aircraft wings) what is less well proven is if it makes any difference to the risk of lightning strike on a yacht.

The effect, at best, will be very slight. Even ungrounded boats have only a very slight extra risk of a strike (but the strike does far more damage) so the potential for the brush to reduce strikes further is small.

IMHO I think they are very slightly beneficial. The effect is so slight I would not bother fitting one to yacht, but if I had one I would not remove it.
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Old 11-03-2013, 08:20   #34
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The "brush" fittings are designed to enhance this disipation (and concentration) of static charge.
It is well known this type of structure dissipates static charge (hence the use on aircraft wings) what is less well proven is if it makes any difference to the risk of lightning strike on a yacht.

The effect, at best, will be very slight. Even ungrounded boats have only a very slight extra risk of a strike (but the strike does far more damage) so the potential for the brush to reduce strikes further is small.

IMHO I think they are very slightly beneficial. The effect is so slight I would not bother fitting one to yacht, but if I had one I would not remove it.
I bet you had no lightning strikes yet and don't spend too much time in the ITCZ? I agree with what you write above but wonder how many strikes you would need before putting a dissipator in the mast? More so when you are struck and others around you but not the boats with a correctly installed dissipator?! For me the two strikes were enough and we ended that unlucky streak with a dissipator on each masthead.

I have seen St Elmos fire in my rigging and in the rigging of a smaller boat anchored next to me. When the strike came it was so violent that I was sure we had a direct strike. There was a sound and feeling of an elevator surging up and all hair stand up... but it was the neighbor that was struck. He did not have a dissipator; we had no damage at all. I know this is not proof, but I also know that, with the first two lightning strikes that our boat took, there were no other boats hit or damaged, so this was a welcome change of events and we were happy to have spent the $200 on the dissipaters.

I have one other experience: this concerned a boat anchored in south Grenada during the summer. We were anchored in the same bay. That boat had a correctly installed dissipater but it was hit by lightning. When we investigated to find out what had been fried and what not, we discovered that the strike had been on the insulated backstay antenna. The automatic tuner had burned out, then the radio and the breaker and some other branch circuits. This was a 43' Morgan ketch. Lesson is that you need to ground your antennas too, but somehow the lightning bolt had passed the masthead without touching it. This is also not proof that it did so because of the dissipater that was installed there; it's just another case where the dissipater seemed to work.

cheers,
Nick.
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Old 11-03-2013, 08:52   #35
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Re: Lightning Dissipator -- Any Good?

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I bet you had no lightning strikes yet and don't spend too much time in the ITCZ?.
Your masts are too tall Nick

Only one strike so far, but that's enough.

Not much time in the ITCZ, but a fair bit in the SPCZ (not sure if that is officially part of the ITCZ , but it was less lightning prone than say around Sydney.
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Old 13-03-2013, 16:20   #36
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Re: Lightning Dissipator -- Any Good?

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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.
@ John A -- Did you have a lightning ground plate installed on the hull? I'm thinking of adding one and as I also have a Cabo Rico 38 I thought I'd ask if you had one and how you wired to it. Since the mast is stepped on the holding tank (at least on my boat), the run to the bilge is not a straight as I'd like. Thanks.
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Old 13-03-2013, 18:06   #37
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Re: Lightning Dissipator -- Any Good?

No, I didn't have a grounding plate.

On my boat (hull #51)the mast sits on an I-beam that is an encapsulaed extension which rest on the keel. .
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Old 13-03-2013, 18:31   #38
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Re: Lightning Dissipator -- Any Good?

I manage engineering for 6 small refineries.

  • All six have extensive grounding; it is required by code for gasoline tanks for both fire safety and corrosion protection.
  • One was hit 3 times in 18 months--but not in 8 years before and not in 22 years since. One strike was at grade (truck scale), even though there was an 80-foot steel distilation column about 70 feet away. The other was on a pipe bridge about 15 feet above grade, within 40 feet of the 80-foot column (well inside the assumed "cone of protection").
  • The others have never been struck, though several are much larger.
Since these plants are manned 24/7, all of this was witnessed. None cause significant damage (scorched paint), other than a few local meters blown.



----


My thoughts?
  • Randomness is at work. Anecdotal reports while honest probably don't mean too much, since there are contrary anecdotal reports and no statistics... and probably won't be.
  • A dissipator is not going to affect leaders that reach many thousands of feet. Nonsense.
  • A good ground path means minimal damage. THAT is the proven case for lightening rods or at least good grounding.
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Old 13-03-2013, 19:24   #39
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Re: Lightning Dissipator -- Any Good?

dockhead-
Check out Polyphaser, a major maker of the protection devices. While you can unplug your antenna cable when the radio is not in use (as a norm, not just in storms) a Polyphaser is an excellent investment.

Last time there was a big discussion of the bottle brushes online, someone mentioned that at least one company guaranteed their product--but no one who had been hit had been able to get paid on that.

And while some parts of Florida are infested with them, you could say the same thing about alligators. Still, considering the cost of lightning damage vs the cost of a bottle brush...who is to say it isn't worth trying to improve the odds? After the polyphasers and the proper grounding, of course.
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Old 24-09-2013, 20:41   #40
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I wondered what those were. Unfortunately the one boat that I saw that had one, was recently hit by lightning. Fortunately it only took out the VHF and they were docked in a marina. Googling "broom looking thingy" didn't yield any useful results. Thank you for the pic.
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Old 18-05-2015, 20:57   #41
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Re: Lightning Dissipator -- Any Good?

We had 2 dissipators on our Irwin ketch and during our twenty years sailing her we went through at least a dozen ferocious lightning storms with no damage! It could have been dumb luck but tomorrow I am installing one on my Pearson. When it can't be proven then I'd say it's worth the hundred odd bucks to have one.
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Old 19-05-2015, 05:59   #42
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Re: Lightning Dissipator -- Any Good?

No - dissipaters (charge transfer systems) aren't effective in preventing, nor reducing the risk of a lightning strike. 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, solidly grounded to the water.

Here’s some links to a few of the expert opinions & papers I’ve previously cited:

A CRITICAL REVIEW OF NONCONVENTIONAL APPROACHES TO LIGHTNING
PROTECTION ~ BY M. A. UMAN AND V. A. RAKOV
MARTIN A. UMAN, Distinguished Professor: ECE-UF Dr. Martin Uman
http://www.lightningsafety.com/nlsi_lhm/Uman_Rakov.pdf

WAR OF THE LIGHTNING RODS ~ By Abdul M. Mousa, (Ph.D., P.Eng., Fellow IEEE)
http://www.lightningsafetyalliance.c...htning_war.pdf
\

There Is No Magic To Lightning Protection:
Charge Transfer Systems Do Not Prevent Lightning Strikes ~ William Rison
(Professor of Electrical Engineering, New Mexico Institute of Mining and Technology)
”... The principles of traditional lightning protection are basic — 1) provide preferential strikes point for lightning (an array of conductors higher than the objects being protected), a good grounding system, and conductors between the two to conduct the damaging current from a lightning discharge away from the structure to be protected; and 2) provide appropriate transient protection on power and signal wires entering the structure to protect equipment and personnel from the effects of induced lightning currents ...
http://www.lightningsafety.com/nlsi_lhm/magic.pdf

Charge Transfer System is Wishful Thinking, Not Science ~ Charles B. Moore*
(Professor Emeritus, Atmospheric Physics, New Mexico Institute of Mining and Technology)

*Charles B. Moore is internationally known for his research on the electrical aspects of thunderstorms and volcanoes. He is an expert in many different areas of atmospheric research, including the scientific and political aspects of weather modification, the scientific and practical issues of lightning protection, and the efficacy of different kinds of lightning rods:
Lightning and Thunderstorm Research - Langmuir Laboratory
Charge Transfer System is Wishful Thinking, Not Science - National Lightning Safety Institute

Fundamentals of Lightning Protection ~ By Richard Kithil, President & CEO, NLSI*
*National Lightning Institute
Fundamentals of Lightning Protection - National Lightning Safety Institute

Evaluation of Early Streamer Emission Air Terminals ~ By Scott D. McIvor, Roy B. Carpenter, Jr., Mark M. Drabkin, Ph.D.
...”CONCLUSIONS: There is limited test data on ESE performance, and no available data substantiates the suppliers’ claims; conversely, the data collected by independent researchers prove otherwise. That is, the ESE performs no better than the conventional Franklin rod.
2. The physics related to the situation, as provided by the atmospherics physics community, demonstrate that the claims made for all of these ESE are wildly exaggerated ...”

http://www.ees-group.co.uk/downloads/ESE%20paper.PDF
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Old 19-05-2015, 06:12   #43
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Re: Lightning Dissipator -- Any Good?

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Originally Posted by lesterbutch View Post
We had 2 dissipators on our Irwin ketch and during our twenty years sailing her we went through at least a dozen ferocious lightning storms with no damage! It could have been dumb luck but tomorrow I am installing one on my Pearson. When it can't be proven then I'd say it's worth the hundred odd bucks to have one.
As a marine electrician I get to do the repair, quoting and meet with the surveyors & insurance adjuster to make sure my customers are getting a fair deal after a strike.

In my own pool of vessels hit I currently have:

* More vessels hit with disipators (fuzzy bottle brushes) than vessels without

* More unbonded (lightning bonding) boats hit than bonded vessels
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Old 19-05-2015, 08:52   #44
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Re: Lightning Dissipator -- Any Good?

At one point there was only one major company selling boat dissipators and they guaranteed a payout if your boat was hit by lightning. Funny thing, even the folks who had them and were hit, couldn't find anyone who'd gotten a payout.


Which of course sets the bunk-o-meter flying off the scale.


Can't hurt to have one, but if you want to just randomly install extra weight (hope the mast is down so you can't risk a fall) aloft, I can sell you a bowling ball, too. Guaranteed to prevent lightning strikes with the unique round, non-conductive rubber construction that traps negative ions while uniformly repelling positive ones! Available in 10, 12, 14, and 16 pound sizes, please be sure to choose one that provides at least one pound of protection per ton (2000#) of vessel weight.
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Old 19-05-2015, 09:01   #45
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Re: Lightning Dissipator -- Any Good?

We have a similar device. In the last two strikes, it managed to save itself but nothing else. Total wipe-out of VHS AIS STERIO 60 amp main breaker, 20 glass tube BUSS fuses, many LED lights etc. Also melted and exploded was the Windex next to the undamaged lightning preventor.
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