Lightning Protection

[captcoho]

After reading older and not so old threads, how many sailors favor grounding their mast and rigging ?

 

[Captain Larry-DH]

I grounded my mast and rigging on my last boat. It was struck twice in 11 years. No hull damage, but a few rigging fittings showed scorch marks and were replaced as a precaution. Extensive electrical damage throughout the boat, both times. Melted VHF antenna both times.
Does it attract lightning if you ground? Maybe. I can’t find anything conclusive on that question. I’ve heard of ungrounded boats that were struck too. I think a clear path to ground helps limit extent of damage if you’re struck, so I favor it for that reason.
My new boat will be more challenging to ground, due to wire runs (catamaran) but I’ve already installed the Dynaplates. Connection on port side doesn’t have a path that can be totally hidden in unfinished areas, so I’m still thinking that one through.
PS - Dynaplates do not explode from a direct strike. I’ve proven that by experience, twice. (I’ve read it on the web based on the theory that the porous metal can explode from internal steam pressure build up. Hogwash.)

 

[Benny17441]

I don't. The fact that lightning is so powerful and unpredictable that it is deemed to strike where it may defies any attempts to control it. There are unproven theories about factors that may prevent or attract lightning strikes and increase or diminish the damage but the data does not support any. I have opted to observe the data regarding lightning strikes on boats and use this data to try to try and minimize the occurrence of a strike. A good and well stablished statistical fact is that the occurrence of loss of life due to a lightning strike on a sailboat is nearly nil year after year. (the same cannot be said for Golf Courses) That alone has removed any fear from sailing near lightning. Another statistical fact is that the majority of lightning strikes occur near land as opposed to open waters. I only really care about the boat getting hit by lightning if I am aboard; as when it is docked and unattended it will be protected by insurance. When sailing I will steer the boat away from land. It is also prudent to get away from a lee shore in the accompanying storm conditions. There are a few theories about "cone of protection", grounding the mast, installing diffusers but they are all at best unproven. Seems to me that the cone of protection and grounding of the mast are mutually exclusive as grounding may seem to attract lightning instead of repelling it. Both theories remain unproven so it would be a personal matter of choice as to which to follow by faith. Very fortunately, remember the odds against getting hurt are very favorably on our side.

 

[Dalliance]

I do. My thinking is that a lightning strike is going to find the most direct way through the boat to the water. Either through a planned ground connection or possibly right through the hull, which could sink the boat. Either way, the electrical system and electronics would be fried, and fire is still a possibility from that, but providing a direct path to the water seems logical to me to minimize damage. As an architect, every tall building I designed was grounded with lightning rods, a proven invention we owe to Benjamin Franklin. An aluminum mast is effectively a lightning rod and the upper portion of Franklin’s system. It needs to be grounded as directly as possible to the water.

 

[PaulK]

We are fabricating a new 1/8" x 1.5" stainless steel grounding connector now to attach to one of our keelbolts.

 

[Dalliance]

We are fabricating a new 1/8" x 1.5" stainless steel grounding connector now to attach to one of our keelbolts.

Mine may be a similar, less robust, approach. I have a copper ground wire from the aluminum mast base, down the compression post, to a stainless steel keel bolt almost directly below. External lead keel. Liberal application of Lanocote at the dissimilar metal connections.

 

[PaulK]

Mine may be a similar, less robust, approach. I have a copper ground wire from the aluminum mast base, down the compression post, to a stainless steel keel bolt almost directly below. External lead keel. Liberal application of Lanocote at the dissimilar metal connections.

Our boat appears to have had a copper connector at one point, but it must not have liked the salt water baths it got, and it went away. Stainless should last as long as the keelbolts, and the lightning won't care. We've had two friends whose boats have been struck by lightning. The bill for new electronics is well worth a dependable grounding system.

 

[RoyS]

I have grounded my mast to my lead fin keel. Once while sailing a lightning bolt struck the water about a hundred feet from my boat. This led me to believe that my grounded mast did not attract lightning or that lightning bolt would have chosen my grounded mast instead of the water surface 100 feet away. The top of my aluminum mast is 50' above the water. Below is a photo of the ground connection in my bilge. The copper bus is separated from the aluminum compression post by a stainless fender washer to prevent electrolysis from eating the aluminum, a very real issue. The other photo is what happens if you connect a copper shunt strap directly to an aluminum compression post or mast in the bilge without a stainless washer. That damage was all electrolysis and not lightning.

 

[JamesG161]

how many sailors favor grounding their mast and rigging ?

Me and ABYC Standard wired boats.

The reason is that you make your boat, open seas, the same strike potential as the water around it.
In fact you shield your boat somewhat by this science...
https://en.wikipedia.org/wiki/Faraday_cage

Jim...

 

[higgs]

I favor having the rigging grounded. A number of years ago a physicist friend of mine said a grounded boat is more likely to get hit, but less likely to suffer catastrophic damage. I don't know how reliable that info is, but I still go by it. My understanding is that lightning does not seek out a target. When it is ready to discharge it does so immediately through the least resistant path. So if that discharge moment occurs a hundred feet from your boat, chances are your 60 foot mast is not the most direct path. Additionally, the rigging provides the crew protection as, I think, it forms a Faraday cage. This is often referred to as the "cone of protection" referred to in Power Squadron materials. If you cruise or distance race you are going to get caught out in lightning at some point.

 

[Benny17441]

I do. My thinking is that a lightning strike is going to find the most direct way through the boat to the water. Either through a planned ground connection or possibly right through the hull, which could sink the boat. Either way, the electrical system and electronics would be fried, and fire is still a possibility from that, but providing a direct path to the water seems logical to me to minimize damage. As an architect, every tall building I designed was grounded with lightning rods, a proven invention we owe to Benjamin Franklin. An aluminum mast is effectively a lightning rod and the upper portion of Franklin’s system. It needs to be grounded as directly as possible to the water.
[/QUO

I have grounded my mast to my lead fin keel. Once while sailing a lightning bolt struck the water about a hundred feet from my boat. This led me to believe that my grounded mast did not attract lightning or that lightning bolt would have chosen my grounded mast instead of the water surface 100 feet away.

Could be that it only proves that a powerful lightning strike cannot be steered and it will strike where it may. I'm not sure about the properties of water to conduct or diffuse a lightning strike as well as firm ground does for a building. If water represents a weakened gap in the efficient path to ground it may not attract a strike as a lighting rod in a building would (?) What factors would changes in water depth impart? Not all lighting bear the same intensity, would stronger strikes behave differently in water than weaker ones? There are too many questions and few answers so, we all have to do what we think it is best for our boats and ourselves until science breaks the code and tells us what is fact and what are conjectures. I too had a blinding and instantly deafening lightning strike close to the boat but I just looked at it as a corroboration of the data that says that the number of deaths attributed to lightning strikes in a sailboat are almost nil year after year. On the contrary there are more deaths in open deck power boats and they don't even have a mast. All we can do is keep sailing.

 

[RoyS]

To further add to the confusion, the oft repeated statement that electricity takes the path of least resistance is simply not true. Electricity takes all available paths. Proof of the latter statement is in any parallel circuit.

 

[JamesG161]

There is no confusion on the SCIENCE involved on Lightning Avoidance [Protection is implies a Shield]

You use SCIENCE to minimize your chances of being lightning's path to a Ground.

This is True on Land or Water [Marina, On the Hard, or Open Sea for boats].

My best comparison of Land and Sailboats...

"Water Towers and Sailboat Masts".

The Science works for both examples. Be well Grounded.
_____
This link has best info on Lightning and humor too.
newbie lightning protection?

But I will copy part of my post#5 here.
_____
You never need a consensus on a SCIENCE!
However several types of sciences involved, thus the confusion.
List in order of your ability to control them...
1) Electrical (flow of electrons)
2) Math (statistics)
3) Religion

If you combine all 3 you can reduce your chances of being a target.
In a nutshell...
1) Ground your boat and Isolate yourself
2) Buy Insurance
3) Pray it doesn't hit you
________
I will repost 2 pages from this book by Nigel Calder.
Boatowner's Mechanical and Electrical Manual: How to Maintain, Repair, and Improve Your Boat's Essential Systems: Calder, Nigel: 9780071432382: Books - Amazon.ca

Good Avoidance for your Boats...
Jim...

 

[smokey73]

Found out some interesting things when working at a weapons disposal facility doing safety assessments, Lightening doesn't like to make "tight turns" and is highly unpredictable in the paths it takes, even with proper grounding. There is an NFP standard on lightning protection that is specific to buildings but has applications for us. First, although not stated explicity, the jist is that lightning takes the path it wants to take. For instance, with grounding straps and and these are big flat woven copper, not just small wires (and 10 gauge is small in terms of lightening) are run from the lightning rod to the ground along metal beams, the attachment point must be grounded to the beam. That is because even the robust straps cannot carry the current easliy and it will arch to the beam if not grounded. There is a specification for how sharp the bend can be in the ground strap since if you try to "turn" the lightning around too sharp a bend it will simply go off course and arc to the nest best available path. Think of a race car out of control around a 90 degree turn. Of course this is in common language rather than the techincal jargon of the standard. They also discuss in detail the concept of a "cone of protection" that effective lightning protection can provide.

Take aways - I will ground my mast to the keel bolt of my lead keel to do what I can and trust in @JamesG161 solution list: BUT
1. I really doubt the little 10 gauge wire would conduct a lot of the current with a direct hit to the mast but it may do enough good to keep from blowing a hole in the boat.
2. The wire is insulated, but probably only good to about 600V and may very well arc right through that along the way.
3. There are probably several near sharp bends in that wire in its path from the mast to the keel bolt.
4. Insulate yourself as best you can, don't be hanging on the shrouds, backstay or hugging the mast during a lightning storm. Take advantage what cone of protection you do have. With any reasonable mast height the cone covers the whole boat. Probably why more lighning injuries on power boats - no cone of protection.
5. Make sure you are insured. Replacing electronics, a near certainty with a lightning strike may be expensive depending on your boat's equipment
6. Have a good relationship with your "Maker" - never hurts to be in good graces there.

I had a lightning strike on my boat, BUT I wasn't even in the water. I was sitting in a travel lift awaiting launch the next morning and not "well grounded" to the water or the ground as far as I can determine. There were the nylon slings holding the boat, the huge rubber tires of the travel lift and the keel was resting on wooden blocks (not very good conductance). Go figure. My mast was about 75-80 feet in the air in the lift but there were other trees taller around. Don't know what that tells you about the advantages of being grounded to the water or not but it is what it is.

 

[JamesG161]

1. I really doubt the little 10 gauge wire would conduct a lot of the current with a direct hit to the mast but it may do enough good to keep from blowing a hole in the boat.

So true with one exception...
The 10 gauge wire allows the grounded mast to be at ground potential, never intended to conduct Lightning Amps
Jim...

 

[smokey73]

@JamesG161 Excellent point and something I didn't consider. As you stated, its not so much about "protection" as it is about "avoidance" in making sure the mast is at the same potential as the water. Also make sense now about the strike in the slings.

 

[JamesG161]

Also make sense now about the strike in the slings.

My boat is on the hard now and I made sure I am Grounded by three Chains hanging and connected to my boat.

Although you can get a Ground strike nearby. I hope the boat yard has a well grounded meter station on 120VAC. Nearby ground strikes can send back Voltage through your AC Ground Wire.
Jim...

PS: I am still fully insured.

 

[smokey73]

I think I actually had what is sometimes called a "side strike". It hit somewhere else nearby and some portion "jumped" to my boat at the mast and it exited through the keel and the wet wooden blocks to the ground. The VHF antenna was "gone", the connection charred, the stuff at the top of the mast was laying in the cockpit, and all my electronics were damaged but there was no evident "exit wound" and no indication that wiring was damaged. Progessive was my insurance company and the were great! They required the mast be stepped and inspected to confirm it was a lightning strike and make sure everything was repaired. When they saw the black burn marks on the VHF antenna it was "lets get this fixed".

 

[smokey73]

I like the idea of chains from the boat to the ground. Are they connected to ground rods into the ground or just laying on the concrete or gravel?

 

[Dalliance]

I believe ABYC recommends 6 gauge minimum (4 gauge is better) ground wire from mast base to keel bolt and 8 gauge minimum from chainplates, etc. to keel bolt. Of course connection to the keel bolt is only for external mounted keels, not encapsulated.