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Old 18-08-2017, 23:07   #31
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Re: Is our mast grounded?

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That is not data, it is opinion. I'd love to see some real data that clearly shows the statistical difference between a ground vessel being hit and a ungrounded one. Do you have a link to actual data?
Paul, not everyone understands the difference between data and opinion.
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Old 19-08-2017, 03:51   #32
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Re: Is our mast grounded?

Whether a mast is "grounded" or not has almost no effect on whether or not a boat will be struck by lightning. In theory there is absolutely no way lightning can tell whether or not your mast is "grounded" before the strike. So best practice is to ground the shrouds (if steel) and mast (if metal or carbon) to the water by some means. That's just for personnel safety and even then there are no guarantees people will not be injured in a strike.

The example above about a boat getting hit multiple times in a short span is related to the ionized air caused by a lightning bolt. It takes time for the ozone (ionized oxygen) to dissipate. Until it does a conducting path still exists so it represents the path of least resistance. Lightning follows the path of least resistance. It has nothing whatsoever to do with mast grounding.
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Old 19-08-2017, 04:03   #33
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Re: Is our mast grounded?

FWIW, I've followed the comments of engineers and people far more knowledgeable than myself regarding lightning strikes and lighting protection for yachts. I've concluded that there are few generalizations to be drawn, given the differences in lightning strike power, boat design, and situational contingencies. Are catamarans struck more often because they are more often moored at the end of a pier for width reasons, and therefore present more prominent masts? My catamaran, I'm told, was struck while owned by the previous seller; but it suffered only a frying of its electronics because lightning protection was built into its design? I'm not certain of that. Other yachts after strikes have suffered major structural damage and pinpoint leaking, to the point of sinking. All I can conclude at this point is that we really don't have a handle on this devastating consequence of nature.
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Old 19-08-2017, 04:04   #34
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Re: Is our mast grounded?

FWIW, I've followed the comments of engineers and people far more knowledgeable than I regarding lightning strikes and lighting protection for yachts. I've concluded that there are few generalizations to be drawn, given the differences in lightning strike power, boat design, and situational contingencies. Are catamarans struck more often because they are more often moored at the end of a pier for width reasons, and therefore present more prominent masts? My catamaran, I'm told, was struck when previously owned; but it suffered only a frying of its electronics because lightning protection was built into its design. I'm not certain of that. Other yachts after strikes have suffered major structural damage and pinpoint leaking, to the point of sinking. All I can conclude at this point is that we really don't have a handle on this devastating consequence of nature. If we did, it would be a non-issue.
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Old 19-08-2017, 04:20   #35
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Re: Is our mast grounded?

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Originally Posted by Paul L View Post
That is not data, it is opinion. I'd love to see some real data that clearly shows the statistical difference between a ground vessel being hit and a ungrounded one. Do you have a link to actual data?
I gave you three sources to support my argument.

As you most probably know, most of the so called data out there concerning lightning is very suspect as if the researchers had already made up their minds on the subject and were simply trying to back it up with some thrown together stats.

It's appearing more and more like you just cannot handle being wrong rather than acknowledging the fact that going "unprotected" is possibly a good way to go.

I found another interesting "source" to support this with some data to back up his assertions.

Also, those that sail without main auxiliary engines or engineless will probably enjoy this data.

Lighning and The Small Boat

From the link above:

Rebuttal

Offered is a theory that an attachment spark will be produced by either a grounded or ungrounded mast on a sailboat in about equal ratio. To support this theory, experiences of Florida surveyors are used. Unfortunately, I think some misinterpretation of those experiences result which, is likely a simple oversight. The interpretation results in a conclusion that boats without lightning protection are being hit in a slightly higher ratio than those with. No serious problem yet. However, then suggested is that the data supports the theory that both grounded and ungrounded mast both produce an attachment spark, and therefore both stand to take lightning strikes in a similar ratio, and if this is true then there is no good reason not to be grounded and benefit from the protection afforded by having a grounded mast. That necessitates conclusions about the mast ground condition on the boats for which the theory is supported. It appears that it was concluded that boats with lightning protection systems had grounded mast and those that didn't had ungrounded mast.

The problem is that assumption doesn't account for several other reasons mast may be grounded. A mast may be grounded by other systems including masthead lighting, instruments, antenna or shore power hook up, any one of which can provide incidental grounding and a resulting attachment producing spark. In fact, it is very likely that almost all sailboats with an inboard auxiliary motor will have the DC ground bonded to the engine block with the result that any lighting, instrument or antenna on the mast with a ground to it's mount, would then ground the mast through the prop shaft to the water. The same is true for an outboard equipped boat in a slip and hooked to shore power.

This means that it is theoretically possible if not likely that most of the boats in the survey had grounded mast, therefore there is no support afforded for Dr. Thomson's theory by these statistics. His theory is intriguing however, and would likely find greater acceptance among sailors if supported by valid statistical or experiential proof. Currently in the absence of trusted data, sailors are left divided about the issue of non-grounded mast offering the same attraction as a grounded mast. Protection then becomes a decision to reduce the chances of a strike or find ways to contain the forces during a strike.

Examining the Theory

An ungrounded mast will have a finite number of free electrons compared to a grounded mast which is being fed an unlimited supply from the water surface. And while those electrons will be attracted to the upper extremities of the mast by the opposing cloud potential, its not been proven that they could sustain a spark capable of jumping to cloud leaders especially if a single diversion point (air terminal) is not provided as a congregating and launching point. It should be remembered, that air while it is a good dielectric, is not a great one and will allow free electrons to bleed off harmlessly from the mast head unless an air terminal is provided and because of the finite number the ungrounded mast will doubtfully produce an attachment spark. This possibility could be further reduced by avoiding a vhf antenna (good air terminal) at the top of an ungrounded mast and installing an ion diffuser as the upper structure.

When comparing the Florida survey statistics to those provided by Boat US for insurance claims for example, six sailboats with auxiliary power per thousand suffer lightning damage but only two per thousand that are sail only. Unfortunately we still can't gleen from these statistics an accurate account for whether a mast is grounded or not. Other variables and explanations could also come into play.

Everything points to a need for a better survey if conclusions about grounded or ungrounded strike ratios can be drawn to support the theory that ungrounded mast produce attachment sparks.
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I have in the past mentioned that my boat is "floating" as we say in electronics when it comes to whether it is grounded or not.


It was another "discussion" on CF about grounding and a fellow mentioned my boat's electronics were "grounded" to the battery but the point was that the whole system is floating.

I removed my engine a while back and all the grounds that were bolted to it I hooked together with one bolt which then fed back to the battery.........which is floating.

I considered all this after the squall I spoke of before.

But lightning is still scary regardless especially when you see the sky change in 30 minutes as it did on this day then come in with thunder, lightning, winds to around 40 knots and rain


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Old 19-08-2017, 04:29   #36
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Re: Is our mast grounded?

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Lightning follows the path of least resistance. It has nothing whatsoever to do with mast grounding.
In my limited experience I would dispute this. Lightning follows all possible conductive paths and even some non-conductive paths (side flashes through hulls).

PS. To the other part of this ongoing argument ...The data does not exist and the probability that it ever will is slim.
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Old 19-08-2017, 05:42   #37
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Re: Is our mast grounded?

Once the lightning gets to your mast it goes the path of least resistance. If that is through the hull then so be it.

Lightning has massive current. The ionized plasma eventually impedes the flow of more electrons and then it branches out from there. But you can be sure it has traveled the path of least resistance at that moment.
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Old 19-08-2017, 05:55   #38
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Re: Is our mast grounded?

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Once the lightning gets to your mast it goes the path of least resistance. If that is through the hull then so be it.

Lightning has massive current. The ionized plasma eventually impedes the flow of more electrons and then it branches out from there. But you can be sure it has traveled the path of least resistance at that moment.
I need more evidence than that, it's not what I have seen and a short Google Search seems to indicate otherwise
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Old 19-08-2017, 06:02   #39
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Re: Is our mast grounded?

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Whether a mast is "grounded" or not has almost no effect on whether or not a boat will be struck by lightning. In theory there is absolutely no way lightning can tell whether or not your mast is "grounded" before the strike.
Actually, this guy believes there is a way lightning can tell and to me his assertions sound quite plausible:

Examining the Theory

An ungrounded mast will have a finite number of free electrons compared to a grounded mast which is being fed an unlimited supply from the water surface. And while those electrons will be attracted to the upper extremities of the mast by the opposing cloud potential, its not been proven that they could sustain a spark capable of jumping to cloud leaders especially if a single diversion point (air terminal) is not provided as a congregating and launching point. It should be remembered, that air while it is a good dielectric, is not a great one and will allow free electrons to bleed off harmlessly from the mast head unless an air terminal is provided and because of the finite number the ungrounded mast will doubtfully produce an attachment spark.

This from the article in the link below:

Lighning and The Small Boat
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Old 19-08-2017, 06:11   #40
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Re: Is our mast grounded?

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Actually, this guy believes there is a way lightning can tell and to me his assertions sound quite plausible:

Examining the Theory

An ungrounded mast will have a finite number of free electrons compared to a grounded mast which is being fed an unlimited supply from the water surface. And while those electrons will be attracted to the upper extremities of the mast by the opposing cloud potential, its not been proven that they could sustain a spark capable of jumping to cloud leaders especially if a single diversion point (air terminal) is not provided as a congregating and launching point. It should be remembered, that air while it is a good dielectric, is not a great one and will allow free electrons to bleed off harmlessly from the mast head unless an air terminal is provided and because of the finite number the ungrounded mast will doubtfully produce an attachment spark.

This from the article in the link below:

Lighning and The Small Boat


This guy does not know what he is talking about. But there is no shortage of that on the internet.

There are no "free electrons" around your mast.
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Old 19-08-2017, 06:37   #41
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Re: Is our mast grounded?

which one is the path of least resistance ?
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Old 19-08-2017, 06:56   #42
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Re: Is our mast grounded?

https://www.westmarine.com/WestAdvis...unding-Systems
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Old 19-08-2017, 07:12   #43
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Re: Is our mast grounded?

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Curious article where they routinely quote ABYC then advise against bonding metals that can be isolated contrary to ABYC then state ...

In the old days, the technique of bonding everything together worked okay. In its defense, the "bond everything together" approach makes your boat less sensitive to electrolytic corrosion that can result from faulty wiring on your own boat. The problem is, the "bond everything" approach leaves your boat totally defenseless to wiring errors in nearby boats and nearby industry, that cause stray DC currents to run through the water.

This after admitting that the galvanic isolator required for ABYC compliance will solve this issue.

Made me think of an old aphorism .... It may work in practice but certainly won't work in theory.
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Old 19-08-2017, 07:19   #44
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Re: Is our mast grounded?

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This guy does not know what he is talking about. But there is no shortage of that on the internet.

There are no "free electrons" around your mast.
Those who know a bit about electronics understand that what he is saying makes quite a bit of sense.

Examining the Theory

An ungrounded mast will have a finite number of free electrons compared to a grounded mast which is being fed an unlimited supply from the water surface. And while those electrons will be attracted to the upper extremities of the mast by the opposing cloud potential, its not been proven that they could sustain a spark capable of jumping to cloud leaders especially if a single diversion point (air terminal) is not provided as a congregating and launching point. It should be remembered, that air while it is a good dielectric, is not a great one and will allow free electrons to bleed off harmlessly from the mast head unless an air terminal is provided and because of the finite number the ungrounded mast will doubtfully produce an attachment spark.

from the link: Lighning and The Small Boat
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Old 19-08-2017, 08:56   #45
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Re: Is our mast grounded?

The problem with the Internet is someone writes something that anyone with a little knowledge can see the logic. But in this case the logic is not there. If ungrounding masts prevented lightning strikes I could be richer than Elon Musk by selling ungrounding kits to the hundreds of thousands of radio mast owners around the world. But any knowledgeable mast owner would see me for a charlatan and they would be right.
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