Lightning -- to ground or not to ground, that is the qn

[aberglas]

By providing a thick cable from the mast to the sea, we hope that (most) of any lightning will take that path to the sea, even if it vaporizes the cable in the process (ions are conductive). However, we also provide a path for charge to move from the mast, so the top will be positive and attracting negative strikes.


Alternatively insulate the mast. Let it float, so that it does not attract lightning in the first place.


My boat has the worst of both. Mast is lightly earthed, will attract lightning but not be able to dissipate it.


Many thoughts, any evidence? What do people think?

[GordMay]

Originally Posted by aberglas

... Alternatively insulate the mast. Let it float, so that it does not attract lightning in the first place...

How do you plan to isolate your mast, from ground, against a lightning bolt [> ± 30 kA @ ± 120 kV], that’s traveled across an air gap of many miles?

Grounded masts do not [significantly] attract lightning.

A ‘Custom Search’, of the Forum will return dozens of threads, discussing all aspects of the subject, and including many links to primary sources of information.

[aberglas]

You are not trying to insulate the mast from a strike. But rather to prevent the streamers reaching up from the masthead to the charge above. To prevent the discharge in the first place.

[GordMay]

AFIC, there is no lightning [protection] expert that does not insist upon solid grounding of the air terminal [mast], including those who market [discredited] Early Streamer Emission/Dissipation (ESE/ESD), Charge Transfer Systems, Dissipation Array Systems; or whatever your particular magic voodoo salesman calls them.

The International Electrotechnical Commission [IEC] prepares and publishes International Standards, for all electrical, electronic, and related technologies, and is the leading international organization, in its field.
IEC 62305, “Protection against lightning”, published by this body, is the international standard for lightning protection, from which most national standards are derived.
This standard states, in the first line of its introduction that:
“There are no devices or methods capable of modifying the natural weather phenomena to the extent that they can prevent lightning discharges”.
IEC 62305-1 ➥ https://webstore.iec.ch/preview/info...ed2.0%7Den.pdf

[GordMay]

Obviously, you’re interested in the subject.
May I suggest a little reading:
“Charge Separation”, & “Field Generation” would be good search terms.

Normally, the ground has a slight negative charge; however, when a thunderstorm is directly overhead, the large negative charge, in the cloud, repels negative charges, on the ground [& upon the sea], underneath the storm.
This causes the ground/sea, and any objects [boats or people] on the ground, directly underneath the storm, to become positively charged. With the cloud polarized into opposites, and with a positive charge induced upon Earth's surface, the stage is set for a lightning strike.

[SailingHarmonie]

There is no question. Grounding is essential to protection of the vessel from potentially catastrophic damage.

[noelex 77]

Lighting is a complex subject, but you do not need to be concerned that grounding the mast will increase the chance of a hit. The overwhelming consensus is that grounding the mast, if anything, helps to slightly reduce the chance of strikes. In simple terms this is because the static charge that normally accumulates as the mast rocks from side to side is dissipated when the mast is grounded.

The reduction is strike frequency is only very tiny. The real reason for grounding is to reduce the chance of catastrophic damage and here grounding will produce a significant improvement.

[s/v Jedi]

Grab this PDF, before it disappears!

Not just the mast, also every chainplate must be bonded. Very hard to do on a cat, much easier on a monohull.

This lightning bonding system has nothing to do with strike avoidance; it is purely to cope with a strike, reducing damage as much as possible.

If you use an external under water grounding plate, which should be located below the mast, make sure that it is rated to be used for lightning protection.

[aberglas]

TE-4 makes an interesting note about conductors needing to be mainly vertical. I suppose this combination of current and static electricity is in a hurray to get to ground!


I am grounding my mast with a thick cable connected to a chain in the water. Will only put it out when there is lightning about. may do something more permanent later. Like most glass boats, it has nothing at all now.


Apparently something like 1% of yachts get struck each year in lightning prone areas.

[s/v Jedi]

Originally Posted by aberglas

TE-4 makes an interesting note about conductors needing to be mainly vertical. I suppose this combination of current and static electricity is in a hurray to get to ground!

I am grounding my mast with a thick cable connected to a chain in the water. Will only put it out when there is lightning about. may do something more permanent later. Like most glass boats, it has nothing at all now.

Apparently something like 1% of yachts get struck each year in lightning prone areas.

That won’t work. The main lightning charge comes down the mast because that path has much less resistance than the standing rigging. When it arrives at the base of the mast, you have to guide it into the water… -vertically- ! If you attach a chain to a shroud or chainplate then you only bring a small part of the charge to the water and the main charge will create its own oath from the base of the mast down into the water. Boats without bonding at the mast often show splatter patterns of hundreds of tiny holes in the hull as a result.

[aberglas]

Thanks, but as I said I am grounding the mast, not the shrouds. Drilling a hole and bolting the thick cable to it.


Normally I would use some anti-corrosion paste between stainless and aluminum. But for this I do not want an insulated connection! There is probably a better way.

[s/v Jedi]

Originally Posted by aberglas

Thanks, but as I said I am grounding the mast, not the shrouds. Drilling a hole and bolting the thick cable to it.

Normally I would use some anti-corrosion paste between stainless and aluminum. But for this I do not want an insulated connection! There is probably a better way.

I’m pretty sure you mentioned using a chain that is hanging in the water. With the requirement to only/mostly use vertical conductors, I can see that only work for a catamaran with a bridge deck suspended over the water, but you don’t have a boat type/model specified in your account so hard to tell.

[TeddyDiver]

Originally Posted by s/v Jedi

I’m pretty sure you mentioned using a chain that is hanging in the water. With the requirement to only/mostly use vertical conductors, I can see that only work for a catamaran with a bridge deck suspended over the water, but you don’t have a boat type/model specified in your account so hard to tell.

That's about what I'll do. Grounding stays to water with deployable copper cable. Maybe a rod on the mast top.. Wooden masts thou

[s/v Jedi]

Originally Posted by TeddyDiver

That's about what I'll do. Grounding stays to water with deployable copper cable. Maybe a rod on the mast top.. Wooden masts thou

Wooden masts! They don’t count as a good conductor… I have no experience with this and recommend you search for more info on Google etc. Are your stays stainless steel? Stainless steel isn’t a good conductor either but I think the classic steel stays may be good. If it isn’t a good enough conductor then you may need a copper conductor from a masthead rod all the way down, tied off a stay.

You can also make electrodes just above the waterline. There was a discussion on this recently for a catamaran, you should be able to search for that on the forum.

[GordMay]

Originally Posted by aberglas

... Normally I would use some anti-corrosion paste between stainless and aluminum. But for this I do not want an insulated connection! There is probably a better way.

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