Lightning protection options

[Divecoz]

Thanks for stirring the pot MOE now along with 2 stroke versus 4 stroke 50 hp versus 70 hp tossing in E-Tec and NOW where do I mount that new antenna. Will the Explorer really tow this boat. How about antenna on the mast using wielding cable for the connection with a Y spliter naaaaa back to chooseing a motor I want a Merc big foot 60 but . . . . . . .

[craiglaforce]

Thanks for the story. Yet another case of a well grounded boat getting struck.
Grounding the mast serves as a conduit for charge to be pulled up from ground and concentrated at the tip of the mast making it a terrific lightning target. they sell charge dissipators for the masthead that look like a bottle brush made of copper. the bunch of little points are supposed to bleed off the charge into the air to lessen the voltage at the top of the mast. I guess it did not have one of these from reading your account. They are quite expensive as I recall.

[Moe]

I don't see an emoticon, but I hope you're using the description, "well-grounded" tongue-in-cheek.

From what I saw today, I feel the 26X mast is probably sufficiently grounded to continuously feed an attachment spark at the top of the mast, whether you want it to be, or not.

There is a metal flange at the top of the compression post that goes up under the mast tabernacle on the deck and is bolted to it, establishing electrical continuity between the mast and the compression post. I also found quite a little bird's nest of excess lampcord wrapped around the compression post up there. So if there is a strike on the mast, there's a good chance most of the electrical wiring, at least all that lampcord, could be burned up.

Given that the base of the compression post is also through-bolted into the centerboard trunk, and that the wet centerboard, trunk, metal cable or soaked rope, is probably far from pure with mineral and marine growth buildup, I think we could have a path to continuously feed that charge up the mast, whether we want it or not.

--
Moe

[craiglaforce]

Moe, you are correct that most of us have at least a partially grounded mast via the compression post and steel cable.
I didn't put a smiley face in my post because I meant what I was saying. Seems like the boats with the perfectly grounded masts are the ones that get struck. I asked a marina owner about grounding one time. the reply was that the only boat that ever got struck by lightning in the marina was a sailboat with a grounded mast.

I'm no lightning expert, but they seem to be the ones that you hear about getting hit.

I think the ideal would be an ungrounded mast with something like that insulated cable idea mentioned earlier, plus a masthead charge dissapator (above the VHF antenna if it is up there). Seems like the odds on getting hit are small in any event, and even if you get hit, it will probably hit the mast and follow it at least to the deck. Unless you are touching the compression post or mast with a foot on the chainplate, then risk of bodily harm is probably low .

[Moe]

Craig, I made the comment I did because of the poor conductivity of the lead keel. I sure wouldn't call such a system "well" or "perfectly" grounded, despite the good intentions.

I'd feel fairly comfortable guessing that this may have been the cause of the damage at the waterline. Given the similarity of the relatively lower conductivity of a 26X below the compression post (if not the deck), it's interesting the only 26X strike we know of resulted in similar damage. In other words, is the lead keel any better as a dissapator than the scum in a centerboard trunk? Or the 26X any worse?

Regarding the mast brushes, if you haven't read this at least read the conclusions at the end. I've wondered how they could be considered effect when hair standing on end has been considered a bad thing as far as making you more likely for taking a strike?

--
Moe

[Greg]

Has anyone seen a wire mesh lobster cage big enough to enclose the Mac (i.e Faraday's Cage)?

I don't know what approach I will take, if any, but still have more questions than answers. It seems this falls in the same category as politics and religion.

The idea of not being on the boat during a lightning storm is the safest solution, but if the boat is used for extended stays in remote areas, there may not be a choice except to be on the boat.

A few things I would like to have a better understanding of:

1. Powerboats get struck more than sailboats. How is the Mac different than a powerboat if the mast is essentially ungrounded (or maybe a little grounded through the compression post and trunk)?

2. A dissapator is better than nothing, but isn't the dissapator essentially making a better ground for the mast but is not heavy enough to carry the current of the lightning bolt?

3. Lightning does not like to change directions (90 deg from mast to grounding system) but yet will jump 3-4 feet to find ground, such as from chainstays to the water. The expensive Strikeshield system bolts a plate to the mast then angles off the mast.

4.Is the expensive Strikeshield system betting on the low occurance of lighting strikes vs the payout if a strike occurs on a boat with their system installed? Same idea as extended warranty insurance?

5.Both statements are from the Strikeshield site:

Will the Strikeshield attract lightning?
Strikeshield will NOT attract lightning, as it is physically impossible to attract lightning.

Radio Antennas. Aerials can draw a strike or cause induced current to flow through the coaxial conductor to the radio. To prevent this, all antennas should have arrestors fitted. Antenna cables can be fitted with a two-way switch: one side to the radio, one to ground. During a storm, or if the vessel is left unattended, disconnecting the antenna cables is an option.

Is there a difference between drawing a strike and attracting a strike to the lightning bolt?

6. One thing that bothers me about the Stewart approach it that you are installing a grounded loop over the center of the cabin, is that a good idea?

7. Welding cables(even 2) are not adequate for carrying the energy of a direct strike, is anything? In other words, what would be required to be equivilant to the mast area?

8. Bare cable is better than insulated cable for lightning systems. Why?

9. If you are anchored out and a storm comes through, are you better off closer to shore (closer to tall trees) or away from shore?

The reason I liked the Stewart approach of the arrestor is that nothing on the existing setup has changed, but if a strike does occur, there is a better( in theory) chance of it being dispersed. Again, maybe that grounded loop over your cabin isn't such a good idea and maybe it wouldn't do a darn thing and the strike would go still go straight down though the trunk (and maybe scatter across any moisture in the bilge).

Would it be possible to use a system similar to the Stewart approach, but a little more engineered? Such as as bolted connectors to the mast with removable insulated cables adequate in size and numbers to disperse the energy, arrestors at the end of the cables (in the water) that are bolted to adequate grounding strips. That way the mast is not hard grounded but still if a strike occurs the energy would be dissapated.

Maybe in the end, as others have said, it all comes down to taking your chances.

Another approach, diversionary tactic:
If golfers get struck more than boaters, how about a floating field of upright putters attached to bouys around the boat? (There's a challenge for you Mark)

Greg

[craiglaforce]

Good points Moe. I "assumed" when I read the words "massive grounding system" and how it was a selling point for the boat, that it was a well engineered system and that the cables hooked to the lead keel were really attached to some copper plate that was attached to the keel as is common practice. Totally agree that if it the cable was just screwed to the lead that this was probably a poor ground and would explain why the lightning found a new path to ground at that point.

As I undestand it, the copper brush dissipator for the top of the mast has no usefulness during the strike and has nothing to do with grounding. It is just supposed to bleed off the charge that is induced on the mast prior to a strike, in an effort to reduce the chance of a strike.

Regarding the size of lightning conductor cables, I think if they are undersized, superheating occurs and the air around it will ionize and conduct the remainder of the strike to ground. (Scorching anything nearby like fiberglass). The wire is mainly to direct the ionization process in a direction that minimizes damage. WHen you are talking about conducting enough power to run a town for a month in less than a second, probably any wire will be undersized, hence I think they all will merely provide an ionization direction.

I like the putters idea.

All just my opinions of course.

[James V]

The biggest problem is the amps that is generated with lightning. Your body (and boat) can handle a lot of volts but not much amps. If the comductors on your boat (i.e. mast and standing rigging) is to small. It will not provide a ground path or prevent the lightning. In other words, if you try to create a path for the lightning with to small of wire it will go where ever it wants and do what ever damage. The amps do the damage.
If you can, get maintance of the building where you work to show you the gounding wires of the lightnning protection. They are big, Bigger than most standing rigging. And there are many. Even so, these are sometimes melted due to too much amps. This is why the lightning protection on boats is nominal at best, But it does give the boater some peace of mind, if not false.

The powerboater that gets hit has a tall. metal rig above the deck in most cases. It is grounded through the motor prop. Very good conductor. They also cannot sail back. So they make the news more than sail boats. I have heard of few small powerboats that get hit.

I find lightning one of the least dangers on the water. Although it is a concern that needs to be addressed.

My biggest fears are -
Drunk/stoned powerboaters.
Drunk/stones Sailboaters.
Big boats that have to stay in the channel or headed my way
Not having enough time on the water.

Lightning strikes fears rank after - running out of food, running out of water, what is the best prop, does the Mac plane ............

[Divecoz]

I agree and yes your's is The Best Post Yet

[Jack O'Brien]

Someone wrote:
".....when hair standing on end has been considered a bad thing as far as making you more likely for taking a strike?"

I don't think the hair has any causal effect on getting struck - just the opposite. It is a SYMPTOM that you are a likely target indicating the potential (pun intended) of getting struck.

[Catigale]

My biggest fears are -
Drunk/stoned powerboaters.
Drunk/stones Sailboaters.
Big boats that have to stay in the channel or headed my way
Not having enough time on the water.

Lightning strikes fears rank after - running out of food, running out of water, what is the best prop, does the Mac plane ............

Copy that...best post on this, agreed....

[PollyAnna]

Since it is lighting season in Texas, I read through all of these posts and looked for a research paper on the subject that gave some statistics on lighting stikes on sailboats. This is from the University of Florida:

http://edis.ifas.ufl.edu/pdffiles/SG/SG07100.pdf

While this will not end the debate, hopefully it will give some insights. If your boat gets hit my lighting, the best thing we can do is look for ways to mitigate the damage. Since my boat sits in freshwater, my concerns are a little higher. While seamanship dictates to get out of the way of the storm, my bigger concern is my boat sitting in the slip (I have the biggest mast in the marina... ). While there maybe some protection for be connected to shore power, I do not believe that this is adequate enough to minimize the damage from a direct strike.

Gregg

[Hamin' X]

I am happy to see that you have done some prior research on the matter, Gregg. The subject has been pretty well covered on this board over the past few years and no consensus was reached. What did come of the discussion were several ways of dealing with the problem.

• Massive grounding project (Mega Dollars)
  Strike avoidance (Some not sure this works)
  Don't worry about it (You are more likely to be damaged from other hazards)

My personal opinion is that we do not have the money to install a properly designed grounding system and that the best protection is avoidance through the use of dissipators. My conclusion is from both research and empirical evidence gathered from my experiences working with both commercial and Amateur radio repeaters located on mountain tops.

Here is a list of other threads on the subject: Lightning Strikes

~Rich

[Rick Westlake]

Pardon me for stirring this pot again - but thunderstorms do get your attention, on the Chesapeake Bay.

Looking over Gregg's link - and some others I've encountered through here and through other websites - I've decided to get the StrikeShield mast-grounding system for Bossa Nova. That is to say, I placed an order for it yesterday morning. With shipping, it's about $600 U.S.

This system uses a massive copper grounding terminal, machined so it's "all edges," swaged and bonded to a 1/0 gauge copper cable. The other end of the cable has a large copper bonding plate that attaches to a same-size mast plate with big bronze thumbscrews. Everything is tinned for corrosion control, and the cable connections are covered with marine shrink-tubing. They offer an aluminum air terminal for the masthead, if you have electronics or antennas up there; since all I have is an anchor light, I decided the masthead is "air terminal" enough.

You can remove and stow the cable below-decks while you're sailing, and deploy it when you think you're going to need it (for instance, at anchor, and the clouds are muttering). Screw the bonding plate down onto the mast plate, then throw the grounding terminal overboard. If you do "hit the jackpot", at least it will give the energy an easy path to follow - outside of the boat.

Like my oversize ground tackle - if it helps me sleep at night, I don't think it's money wasted.

I am happy to see that you have done some prior research on the matter, Gregg. The subject has been pretty well covered on this board over the past few years and no consensus was reached. What did come of the discussion were several ways of dealing with the problem.

• Massive grounding project (Mega Dollars)
  Strike avoidance (Some not sure this works)
  Don't worry about it (You are more likely to be damaged from other hazards)

My personal opinion is that we do not have the money to install a properly designed grounding system and that the best protection is avoidance through the use of dissipators. My conclusion is from both research and empirical evidence gathered from my experiences working with both commercial and Amateur radio repeaters located on mountain tops.

Here is a list of other threads on the subject: Lightning Strikes

~Rich

[Divecoz]

Not to worry about stirring the pot Rick...... we do it here a lot all the time But please tell us how it goes though. IF...... you ever take a hit tell us about that as well.