Lightning Protection

[Al Lorman]

Eb asked me to start a new thread to "show us what you're doing to protect your new toys now" after replacing them due to lightning.

First, let me describe what happened. I was not aboard at the time, so this is reconstructed. My Freedom 30 was tied up in its slip on a Friday in early August in the Chesapeake and there was a typical August thunderstorm, along weith lightning. The marina owner later told me that there was a very close strike, so close his office lit up. The next day, I was aboard and began to notice that nothing electronic worked. (It later turned out that the depth sounder transducer and the electronic compass sensor did survive.) Since we could find no physical evidence of a strike, many folks told me that it was probably due to the electromagnetic pulse from a nearby strike. My son noticed that there was some scorching in the plugs connecting the VHF cable to the antenna cable running up the mast. A new VHF radio didn't work all that well, so I replaced the antenna. I took apart the old VHF and found that there was a very distinct burn mark inside the case where the antenna cable plugged in. So I'm assuming that in fact the strike hit the VHF antenna, traveled down the mast cable and fried everything connected to it in one way or the other. (This doesn't explain the loss of the 120v GFCI, however, or the electronic switch on the bilge pump.)

Sorry, too long an introduction. Ebb, as far as I can tell there's really very little that I can do to protect my new instruments. Everything appears to be grounded properly and I did not have side flashes trying to blow a hole in my hull to get out. From what I've read, and I read a lot, the only reasonably priced device is that sort of wire brush affair that you mount at the masthead, and there's no real consensus that it works. I'm told that real lighning protection probably could be provided at extraordinaily high cost and at a weight penalty that would sink the boat. Even disconnecting everything when you leave the boat doesn't protect you from the electromagnetic pulse. So, for better or worse, I've simply replaced everything and will keep my fingers crossed. I wish I could share an easy solution but there really doesn't appear to be one. I do recommend a good insurance policy.

Al

[ebb]

Thanks Al,
Have to be brief, on the run.
Have heard that the brush is bunk. Might have a hard copy so I look for it.

The extreme method I have to contemplate is a solid bronze plate of a certain dimension with SQUARE edges directly under the mast on the outside of the boat with oversized thru bolts with cable going up both sides of the hull - or the doorway in the case of the Ariel - with both directly connected to the mast. This without any bends or as straight as possible. Something like that.

I don't know if there are ANY PROVEN systems to protect a boat from lightning. Whos's to say that the jolt won't knock out a hole in your boat the same size as the plate? Who's to say?

In the Ariel you'ld have to have the plate on one side of the keel. One plate NOT faired in per specs and you would go slower on one tact. Put another on on the other side and go even slower.

Electronics are supposed to be protected if you unplug them and put them in a metal box.

r i g h t !!


(Did you share the strike with others there? Maybe in a marina you can get struck a second time? Remember on a thread here someone saying (Bill?) that clipping battery cables to the upper shrouds at the chainplates and tossing the ends in the water was as good protection as any.)

[Dan Maliszewski]

Found these, and they seem like interesting reading...

http://www.thomson.ece.ufl.edu/lightning/

http://www.marinelightning.com/

[Dan Maliszewski]

Sorry, forgot to add these.......

http://www.boatsafe.com/nauticalknowhow/lightning.htm

http://www.strikeshield.com/

[Theis]

One thought is that with regard to lighning, there is no an absolute and the rationale for whatever you do should not be thought of as a binary - it works or doesn't work.

The issue is whether whatever you do for lightning protection diminishes the liklihood of a destructive lightning strike. I think it is reasonably well recognized what can maximize the liklihood of a lightning strike - but that does not mean that all lightning will strike that target.

So looking at the opposite case - what decreases the liklihood - there are numerous alternatives - and many are based on black magic. Just because a boat gets hit doesn't mean that such and such doesn't work. It may have diminished the liklihood or the damage.

As for bending the grounding cable, the cable has to be bent. The key is to make the bend with the largest possible radius.

As an idea, I think that boats are often hit because of corrosion in the grounding path. One ohm of resistance at a terminal point in the grounding path can generate a 10,000 volt potential if there are 10,000 amps running through it - and that is not much current for a lightning strike. Another factor is that the resistance of a corroded connection (and even one not badly corroded) can increase significantly as it heats up - possibly even becoming an open connection.

So as you examine your grounding system, look for places where there might be corrosion. Particularly check any connections where a stainless steel and aluminum are joined (such as a screw terminal).

Even though a meter is highly inadequate for this purose, it is still better than nothing in looking for a less than 0 ohm resistance path to water ground.

[ebb]

Great tips!

Don't think ohm putting bronze plates on the keel. no way.

Suppose I wire (what kind?) the four long stays and shrouds at the top of the mast to that blunt pointed rod I read about that extends alone above the mast.
When lightning threatens I clip four denuded battery cables to the wire above the four terminals at deck level and toss them in. What's the ohm in that, I wonder? Cheaper and simple or foolhardy and dumb?

What they say?... a strike is hotter than the surface on the sun? Are there examples of sailboats getting hit and NOTHING happens because skipper got it right? How did they do it? Of course it's not news if the boat's OK - maybe there's a clue in the one right next to yours that didn't fry?

The tricolor up there is wired in the mast. But if I wait long enough LEDs will come down in price and there will be a very small insignificant unimportant insulated wire the lightning won't be interested in. Right?

[Theis]

I have put a copper plate on the bottom of the boat, just under the locker. My lightning lines are tied to that. There is a plastic heat dissipator pad in the electrical connection on the inside so the heat generated by the current passing through is not dissipated by the fiberglass

Although I have no empirical evidence to prove this, I am reasonably confident that the electrical connection between the masthead fittings and one or all of the shrouds is usually solid. Those connections tend to work thereby wearing off any corrosion build up. Plus the masthead fitting is aluminum, as is the spar, so there wouldn't be electrolysis.

Where the problem can occur is at the foot of the mast and the shrouds - in my opinion. In the Ariel, inside where the grounding cable is tied to the chainplates is where I have seen corrosion, and, in fact, had to replace my connectors because they were eaten away with corrosion. The wires inside the connectors were super green, and many of the strands were broken as I recall. If all six shouds are tied together at each of the six chainplates using the #6 wire, you're probably in good shape.

What I don't like in the Ariel is that the ground wire on my boat was tied to a small screw on the water intake fitting. That seems too small for me - and I fear the fitting would be blown out - although apparently that has never happened.

The wire to use for lightning is #6 stranded copper, with Anchor (non-corrosive) terminal fittings to connect to the chainplates (and the pulpits and the lifeline/stanchion assembly). As for the tricolor, the lightning would probably bypass it totally, preferring the path of the very low resistance of the mast and shrouds.

Battery cables with one end clipped onto the shroud and the other dangling in the water are good - although I have heard the wetted area in the water is not adequate. You're more fortunate in salt water than we are in fresh water because saltwater is more conductive.

As for boats being hit without damage, yes it happens frequently, and it has happened on my Ariel (many years ago). It is called St. Elmo's fire. The stays hum and can even glow (the "fire" in St. Elmo's fire). When that happens, the boat is discharging the cloud precluding a voltage buildup to cause a lightning strike. The old square wooden square riggers had St. Elmo's Fire happen all the time.

Incidentally, I have been reading about Ben Franklin (the book by Isacsson - great book) and his experiments with lightning. In the book it is pointed out that one of Franklin's findingss was that a rounded surface (your tri-color for example) won't dicharge anything. The key to a lightning rod is to have a point - and that goes to how the static dissipators work. They form a plethora of points to discharge any accumulated positive charge so the masthead does not electrically attract the negatively charged clouds.

[ebb]

iee e e! matey.
from Dan's fourth http above we find we can purchase a StrikeShield product that is pretty much an exact up grade from the 'battery cable'.

They have a narrow cuplike head on the water end and a flat plate you strap to the mast with flat nylon. Port and starboard doodahs will cost you an amazing $799. There is nothing in the specs (excuse me!) that suggests what this money gets you. You can buy a single one for about half that: the "Plain Jane" model.

You could no doubt solder up the ends of a couple b. cables to flat curved metal pieces that you nylon tie to the mast base or hose clamp for real tight contact. Maybe the water end could be larger rectangles of copper plate soldered to the cable. Since the ends are relatively small rectangles of the copper plate, might think of sandwiching the cable between two pieces and clamping with machine bolts.

Dan's info above suggests that rigging is a poor conductor because of the 'broken' conductors in the wire, toggles, etc. But I'm not certain why the mast top is any better, since the spike or brush would have to be linked to the mast head, the mast head is probably bedded in aluminum oxide, and then another connecting link to the mast metal itself. Just saying: there seem to be a number of interruptions on the top of the mast.

If you want to neutralize the sailboat's highest point with water-ground, imco the best way would be a single unbroken conductor from the spike above the mast down the mast or the rigging to the water. Don't know what that conductor is, anything less is problematic.

Maybe StrikeShield has saved some boats. Since none of this guarantees the safety of the humans aboard during a thunder storm, the best commercial fix for that could be to get one of those Plain Jane's and strap it to your leg.

[continuing self talk here:
Another unanswered point with the battery cable / strikesheild protection method is that it creates a break in the lightning's path to the water. Aluminum oxidizes readily - to get a good connection I guess you'd have to scrape the mast to bright metal before connecting the cables. (?) When aluminum wire was popular it became apparent it caused fires in homes. Often it was the connectors, but sometimes it melted and burned in the insulation. Anyway it is a LINK problem, if not perfect could imco side flash and/or blow out at the fitting on the mast.
That imco is the problem with connecting the mast at the base to the water. Seems to me you are giving 100,000,000 volts the opportunity to toast the mast. And any body close to hand!
I'm pretty convinced that a unbroken run (lamp cord?) from top to bottom is what to look for for protection. Anyone with an opinion?]

[Anthony/Bina]

Hi Everyone,

We had an electrician check out our wirng/electrical system today because we have recently been re-wiring the entire boat. The elctrician told us that we don't need the ground/bonded wire, the wire that connects to the chainplate from the negative bus. He said we don't need it because we don't have any metal under water and we were wondering if that was for sure true?

Thanks for input!
-Anthony/Bina

[ebb]

Got any thruhulls, seacocks?
How about the rudder post, rudder fastenings, bolts, gudgeon, and rudder shoe?

There is still considerable controversy over bonding all metal parts together on a saltwater boat. Your electrician may be the other camp that believes underwater metal should be isolated from each other because varying potentials might cause galvanic corrosion when wired together.....etc.

Ariels have had bronze corrosion on the ruddershaft in the rudder tube which could be caused by using manganese bronze rod (which is a brass) rather than silicon bronze - where the zinc leeches out because the potential exists in the metal alloy. Wiring pieces together here probably wouldn't help and might make things worse.

Do the SEARCH mode and find out about zincing and where to place zincs - probably your best protection. It would be very good to know what has worked for long time A/C skippers because I have read it is also possible to screw things up by OVER zincing!

[Theis]

In the most recent issue of Seaworthy, the Boat US Insurance Magazine, under MAILBOAT Letters/ Lightning Protection there is a reprint of a portion of a letter from me, and their response. My letter reads:

On the issue of lightning strikes, your article did not mention the issue of electricqal resistance between a sailboat masthead and the water. For example, there may be excellent conductivity between the hasthead and the chain plates (through the aluminum mast and the stainless steel shrouds), and the keel being well grounded, but a couple ohm resistance in the electrical connection between the chain plates and the grounding cable to the keel could, in the event of a lightning strike, build up tens of thousands of volts across that corroded connector and cause the lightning to jump.

The response of the editors was as follows:

A good point and one that highlights one of the reasons why boatbuilders hesitate to install lightning protection systems. Conductivity in the entire system must be near-perfect and over time, corrosion creeps in around connections, increasing the resistance to a point that lightning protection is no longer effective.

There are a couple other letters there plus the article frm the previous issue for those that are interested.

Perhaps the authority, IMO, on the issue of lightning strikes is a book by Michael V. Huck Jr. "Lightning and Boats - A Manual of Safety and Prevention" published by Seaworthy Publications, Brookfield, Wisconsin. Address is 17125C West Bluemound Rd., Suite 200, Brookfield, WI 53008.

[ebb]

Theis, on the subject of this thread, makes imco a very good clear point here.
I am only a student of the problem. The lightening protection system on my sailboat will never get the constant attention it needs. How would I do it? Go aloft with a meter and a magnifier? It is to me a rather gerried collection of assumptions, anyway. If I am depending on connections of bolts and rigging parts what's the fix to get better connections? Something in a spray can?

The hatch is wide open for a genuine invention to appear on the market, like a single or pair of dependable UNBROKEN runs of cable? from the top to the ground. Perhaps it could be a diy upgrade rather than an obscenely priced doodah. Perhaps it could be weight saving sacrificial aluminium cable that can be renewed easily.

1) The lightning protection system is completely separate from
2) the grounding of a boat's electric system. And I believe
3) the bonding of underwater metals, if you choose to do it, is a separate system as well.
To me that means no sharing of any wires or cables or grounding plates.

If someone could set me straight in very simple english, on this once and for all I'd be grateful. Tho still a curmudgeon.

One ohm more of resistance here:
I feel that if at all possible I have to keep the lightning strike outside the inside of the boat. I feel that NO wire runs connected to the strike safety system should exist inside the cabin. I feel the mast base should not be wired to ground thru the interior space. I feel that bolting a bronze plate to the hull that is somehow connected to the rod on top of the mast is asking for trouble. One ohm out might spell disaster. I feel the faraday cage effect should somehow be incorporated into the safety system to ensure as much as we know that no side flashes are possible in the event of a strike. To me that means use the rigging. That means get the strike to ground without impedance. Or as somebody has pointed out, have such a good ground that lightning is uninterested in my little ship.

[Anthony/Bina]

ebb,

I think you bring up very good points.

In my particular example and I don't believe that the original Pearson wiring was designed for lightning.

My commander is completely stock, with no toilet plumbing or any other through holes except for the drains in the cockpit.

The only thing I have are wires running from the aft chain plates to the negative bus bar. Thus far, I have come up with the following reasons for these wires:

1. They were put in every ariel/Commander and were perhaps necessary on more complex versions of the boat such as internal engines and such. ( For corrosion protection?) But on my stripped-down version, they are completely unnecessary?

2. the wiring was designed to somehow reduce corrosion from the chainplates? perhaps the original designers felt this was important? But it adds a further question, why were only the rear chain plates grounded/bonded? and shouldn't bonding be only required on underwater components, not shrouds and chain plates?

3. This was some sort of attempt at a lightning protection system? But this would not make any sense either because the wires terminate at the negative bus bar which runs to the battery only? Making this a very unlikely scenario.

Are there any other reasons that anyone can think of why these wires would exist? So far I think that number 1 is the most likely reason. and if this is the case it would seem that I could remove these wires.

Any thoughts? Does anyone else's but have the similar wiring configuration? My ground wire was a 10guage green wire.

[Dan Maliszewski]

Capt,

Yep, I got 'em that way on my Ariel, both aft lowers wired in to the system. Don't know if it helps, but doesn't seem to hurt either. HOWEVER, I did used to have a #10 wire connected from the system to my starboard thru hull seacock (bronze). First year in my new marina, and I saw etching on the outer seacock plate when we pulled the boat that winter, so I removed the wire and have had no trouble since. "Hot" marina, I guess, as it went for forty years with no etching. Just for sh*ts and giggles, I also put in a battery disconnect switch each for the motor and the system, and I open both when I leave the boat.

A few years ago, lightning did hit #199 at the dock, but only toasted the radio and fused the "on" switch, which drained my new battery, and I replaced both. No further damage. THAT'S when I put the disconnect switches in.

Carry on...
Dan

[ebb]

Been six years since this thread was posted.
Anybody for a fresh start?
Here is a paper on the subject with some scary diagrams from EM Thomson of the U of Florida - 2010.

google>
SGEB - 17/SG071:Lightning & Sailboats

also see google>
SailboatOwner.com - Strikeshield lightning ground
for a rebuttal.

Maybe some practical feedback is in order?
__________________________________________________ _________________________________________________
google>
Lightning Protection - Cruisers & Sailing Forums
imco some excellent posts of actual experiences, observations, explanations and consequences of this most dangerous phenomenon.
Most agree there is no way to prevent a hit.
There seems to be no concensus on the best way to minimize damage from a strike - but reading these entries may persuade.
My concern still is:
What is the best and most economic mechanical lightning strike diverter for our specific Ariel/Commander?
Most important: What is the safest procedure a sailor can do to protect himself - and crew - on his boat when there is lightning in the area?