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Old 04-01-2016, 10:44   #46
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Re: Should mast be grounded or not?

Thunderhoof-
I thought the #1 preferred way to connect a lightning rod cable to a ground rod was to use a thermite cup and fusion weld the two conductors together, making for the lowest possible resistance and best conductance into the ground.
Of course, Home Depot has good reason not to be offering thermite to every yoyo on the block.(G)
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Old 04-01-2016, 11:04   #47
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Re: Should mast be grounded or not?

Thanks guys/gals it was a rhetorical question since I wanted someone else to explain it so I didn't have someone come back with formulas and such.
I wonder how many employ them or even know about them. Low tech.. Two little points with an air gap.
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Old 04-01-2016, 11:50   #48
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Re: Should mast be grounded or not?

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Thunderhoof-
I thought the #1 preferred way to connect a lightning rod cable to a ground rod was to use a thermite cup and fusion weld the two conductors together, making for the lowest possible resistance and best conductance into the ground.
Of course, Home Depot has good reason not to be offering thermite to every yoyo on the block.(G)
? as I recall? Thermite was used to weld train tracks in days of yore.
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Old 04-01-2016, 11:58   #49
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Re: Should mast be grounded or not?

Cadence-
It is handy stuff, but for some reason, WalMart, Sears, Lowes...they all refuse to stock it. Heck,I can't find it on Amazon and it isn't even in the Sears Special Tools catalogue anymore. :-(
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Old 04-01-2016, 12:07   #50
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Re: Should mast be grounded or not?

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Cadence-
It is handy stuff, but for some reason, WalMart, Sears, Lowes...they all refuse to stock it. Heck,I can't find it on Amazon and it isn't even in the Sears Special Tools catalogue anymore. :-(
It is Iron filings and another of several metal oxides. Have no idea what it has to do with a spark gap on coax?
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Old 04-01-2016, 12:20   #51
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Re: Should mast be grounded or not?

Like always, half this thread has good info and half is complete nonsense. Well there is some 50-50 posts as well.

If your boat is not metal then a lightning protection / bonding system makes sense because guiding the bolt via a path designed by by the system is much, much better than letting the bolt decide. Human bodies conduct better than air to give an example.
A protection system for a boat does not have a lightning rod; it does have a ground plate which should be thick solid bronze, not the sintered SSB ground plates. Also, for a monohull, the bronze pkate should be directly under the mast which is the main conductor. The base of the mast should have a direct/straight conductor to the plate of size awg6 or better. Other metal parts, like chainplates, should ave their ownconductors to the ground plate. A ketch should have two ground plates: one under each mast.

You can't prevent a strike from happening, but you can try to have it seek something else to strike than your boat. This is where the brush-like devices come in. It can bleed ions that fom a leader but only so much... one can hope enough to make another object, like the pointy end of a leaf on a tree, or the lightning rod on top of the nearby church, or the breaking wave a little further on, to appear as a better path for the strike.

With a good system you can expect to escape without being holed by lightning, but all electronics will be fried normally.

Then there is the antennas. Anything that is not bonded can cause problems as it can build up a charge for a leader. If you have a HAM or SSB antenna, then it should be disconnected from the tuner and grounded. Same for vhf antenna, insulated stay etc
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Old 04-01-2016, 12:22   #52
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Re: Should mast be grounded or not?

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There was discussion of grounding and lightning strikes in this thread, but no clear conclusions:

Offshore Sailing in Thunderstorm far from land

Still seems to be the case. no conclusions, just different opinons and some of those by people trying to sell solutions.
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Old 04-01-2016, 14:20   #53
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Re: Should mast be grounded or not?

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Still seems to be the case. no conclusions, just different opinons and some of those by people trying to sell solutions.
I don't know anyone was trying to sell a solution. It's a crap shoot, wrong place at the wrong time. Wish I had the answer to minimize it.
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Old 04-01-2016, 20:56   #54
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Re: Should mast be grounded or not?

Do i need to ground on a steel boat
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Old 04-01-2016, 20:57   #55
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Re: Should mast be grounded or not?

Does a steel boat have to worry about grounding for a lightning strike
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Old 04-01-2016, 21:26   #56
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Re: Should mast be grounded or not?

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Hi all, Very interesting reading here...I don't want to sound like a dummy here but what is an air gap double pole switch? If these will protect electrics I would install one before each item on the boat...
Thanks a lot
Its a plain old fashioned toggle switch like you buy at the chandlery or Home Depot. Opening the switch creates an air gap between the contacts. A double pole switch has two parallel contacts so you can break both plus & minus conductors. Keep the switch close to the device so you minimize the potential for induced current in the wire between the switch and the device. As I noted (#14) nearly all electronic devices have only software switches so the plus wire is sill connected to the switching circuit (transistors etc.) on the main power board. Negative is always connected. A double pole switch renders the device un-connected from the boat DC wiring. We further isolate the sense connectors and antennas by unplugging.

We have used the same concept to isolate the entire solar charging system using two-pole breakers on each panel and between the charge dontroller and the batteries. All sense connectors are also on toggle switches.

We also isolate our pure sine inverter from DC using a 30 amp double pole double throw switch with center off position.

No guarantees, but this is as close to a bare piece of equipment in a box on the table as you can get without removing stuff totally.
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Old 04-01-2016, 21:38   #57
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Re: Should mast be grounded or not?

Following our big hit noted in #14 above, we sailed to Lake Superior. In Marquette's Cinder Pond park marina we were tied to the wall close to town. To the west & south was a tall hill with tall buildings & antennas. To the east was the yacht club & the old ore dock. The top of the ore dock has a steel railing all along - I assume grounded. A storm roused us early morning. I quickly unplugged lots of things and watched four hard strikes to the ore dock railing over abut 15 minutes. This was only about 200 yards away. For once, we were not the tallest target.
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Old 04-01-2016, 21:42   #58
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Re: Should mast be grounded or not?

Re being next to a taller mast:

More individual observation: a few years ago in the MBTBC marina in Manly, Qld, there was a direct strike on the mainmast of a friends boat, a steel spray "replica", causing major damage to electronics (ham operator wit lots of gear besides the normal boat stuff). The odd thing was that she was between two sloops in adjacent berths, and both of them had masts that were quite a few feet taller than the Spray's kinda stubby rig.

Being that the Spray was steel, one can assume t hat t he mast was grounded to t he sea, but I don't know about her neighbors. There was no hull damage noted BTW.

The only consistent thing about lightning that I have observed is that it is entirely capricious!

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Old 05-01-2016, 05:36   #59
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Re: Should mast be grounded or not?

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I don't know anyone was trying to sell a solution. It's a crap shoot, wrong place at the wrong time. Wish I had the answer to minimize it.
If you follow some of the links offered here as advice by experts, you will find that some of them, indeed, are in the business of selling lightning protection.
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Old 05-01-2016, 08:06   #60
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Re: Should mast be grounded or not?

I remember following a heated thread on here years back about this subject. The consensus was that any form of protection was better than doing nothing at all. There was one forum member (I forget his name) who practically wrote volumes trying to school us on the subject (his career was in land based lightning protection but he wasn't trying to sell us anything). What he explained was that the notion of providing a path to ground in a direct strike is fairly ridiculous as that is not how protection systems work and that the force of a direct hit is enough to vaporize any conductor we can provide. Our masts and spiderweb of rigging is like a trap for static electricity. When there is a strike there is always an "attachment spark", a spark in the opposite direction (from your mast to the cloud) that ionizes a path through the air that the main strike will follow. The purpose of grounding the mast and rigging is to bleed the current from the static in the rigging to the water. To do this effectively you need a fairly large grounding conductor in the water. The reason to ground the mast as opposed to the rigging is that aluminum is a much better conductor than stainless steel. Hanging pieces of chain from your chainplates into the water is not that effective (but better than doing nothing). Relying on an air gap between the chainplates and the water (as mentioned above) is ineffective in bleeding the static and in a direct hit would actually increase the voltage of the "spark", I think that this person got tired of posting on here about the subject (but if you are out there please chime in!). The "bottle brush" on the mast is meant to dissipate static back into the air but is considered by most to be completely ineffective. Also worth noting is that there are several types of lightning and several ways they can affect a boat, for instance, you can fry your electronics just by being near lightning. I am not professing to completely comprehend the subject but when people speak about their ground wire from their mast being able to divert a direct strike I am pretty sure that would be an oversimplification of understanding on the issue. Also, grounding the mast to the keel doesn't guarantee a good electrical connection with the water, think about the coatings on the keel. Something else to think about is the corrosion where the ground wire (copper)is connected to the mast (aluminum) with a screw (SS). Someone should go back and find some of those old threads and read through them, it has all been discussed here before, but don't expect to find any definitive answers...
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