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lightning preparation

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DaveR
Master Marine Consultant

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USA
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Initially Posted - 07/17/2007 : 13:14:57

You may have seen my post on the cruising thread talking about wicked summer storms and lightning. I have an extra piece of stay cable that I have secured to a stainless rod (probably 3 to 5 lbs.) on one end and a screw down clamp on the other that I attach this to my back stay so the steel rod and cable are in the water to ground my boat. This should theoretically save me from grounding through the hull if lightning does strike. What's your opinion of this tactic and/or what do you do if anything to prepare for a lightning storm?

Dave Robbins
PO to*Bamboo*
'89 SR/WK #5877
Daytona Bch., FL

http://bambooc25.weebly.com/

Edited by - on

Champipple
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Response Posted - 07/17/2007 : 13:53:41

There are two schools of thought on this and even most professional boat workers, etc shy away from providing any guidance in this area. School A - If I am grounded then when I get hit I have a clear path to the water and i can minimize the damage on my boat. School B - If I am grounded I provide the shortest path to the water and am inviting the lightening. Therefore I am not going to ground my boat.

Your method seems logical to me. My question would be - Does it always take the path of least resistance? Does it ever take the shortest path? Is that less resistance than the mast through the hull? I personally subscribe to the latter school of thought and would rather not invite the lightning onboard.

As for preparations - Not much at all. The obvious one is don't sail in lightening storms. Great in theory, but that storm can roll in on the Great Lakes with little or no warning. I've been caught in 3 or 4 lightening storms while overnight racing 10+ miles out. We make sure we aren't trailing any lines, reef if needed, sail change, life jackets, dog hatches, tie down crap etc. the usual heavy weather stuff. As for the lightening specifically, we don't do much. Generally I try not to touch anything metal which is nearly impossibly while hiking on the windward rail. With the jib tracks under the hind end, rail under the thighs, Top lifeline across the back of my neck, lower lifeline against my gut and a stanchion separating me and the sucker in the next position aft I am pretty much SOL. I have heard a prayer or two at 3 am, that guy never raced with us again.

Edited by - Champipple on 07/17/2007 15:28:22

Don B
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Response Posted - 07/17/2007 : 15:19:23

Dave, here is an interesting site..."Lightning and Sailboats", produced by University of Florida:

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

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Arlyn Stewart
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Response Posted - 07/17/2007 : 15:53:48

With all due respect... I don't think very highly of Dr Thomson's junk science.

Edited by - on

Dave Bristle
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Djibouti
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Response Posted - 07/17/2007 : 19:12:12

YOu can search on "lightning" and probably find some lengthy threads. I've looked at a lot of opinions, "junk science" and otherwise, and reached the following conclusions (for myself):

1. Salt water is a good enough conductor that lightning often goes directly to it, sometimes missing boats by a very short distance (and frying their electronics from the magnetic impulse). Fresh water is less so, and boats are somewhat more attractive on it.

2. An improper ground is likely worse than no ground. Stainless is a poor conductor, especially compared to aluminum. If lightning hits the top of the mast, it's as likely to go down and through the bottom of the boat as follow stainless cable, even if it goes directly into the water. The most widely accepted "proper" ground is a staight run of very heavy copper cable to a thru-hull terminal attached to at least a one square foot heavy sheet of copper, which is typically formed to the bottom of the boat. I doubt that any "professional" (if there is such a thing) would agree to rig anything less.

3. The cabintop-stepped masts of the C-25 and C-250 are, IMVVHO, relatively well insulated from ground. I once knew of a powerboat that was hit by lightning in a marina, parked right next to a sailboat similar to the C-25. I also know of a Catalina that had a strike into the water within yards of the boat. (Electronics were toasted.)

My C-25 went through many lightning storms for 15 years before I bought her, and five more years after--sitting in a slip or on a mooring for all but a few of them. To date, she's never been hit. I decided not to try to fix something that apparently wasn't broken.

DISCLAIMER: YMMV

Edited by - on

DaveR
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Response Posted - 07/18/2007 : 07:40:54

Thanks for all the good info and opinions guys. It seems logical to me that 1) If a good ground is there it may serve as an attractant to lightning, and 2) The cabin mount mast IS very well insulated from the water and so MVVHO has been changed and I'll probably leave that cable stowed. And you know, I live in the land of lightning and haven't heard of a sailboat being sunk or heavily damaged by a lightning strike.

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Dave Bristle
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Djibouti
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Response Posted - 07/18/2007 : 08:48:49

The good news, Dave, is that your system was probably no more of an attractant (or a "good ground") than your backstay and aft chainplate already were. Light-guage stainless steel is only a slightly better conductor than chewing gum. The expert opinions I've seen say use very straight runs of very heavy copper or don't go there at all. If lightning does visit, it comes very large! (As I recall, it takes 17,000 volts to traverse one inch of dry air--only slightly less to go through rain or high humidity.)

Edited by - on

DaveR
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Response Posted - 07/18/2007 : 12:00:36

Dave,
I do understand Stainless is a bad conductor of electricity and my thought was that it was a good non-corrosive weight to get the stay material in the water. But it really sounds like I'm better off without the ground anyway, not going there any more. Thanks again
P.S. won't hold anyone liable if I get struck

Edited by - DaveR on 07/20/2007 07:29:31

Trust Me
1st Mate

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Response Posted - 07/19/2007 : 15:21:10

One last item is to review your insurance coverage especially in the area of electronics. Does the carrier pay for total replacement? Are you covered to buy a new boat if you come back from a trip and find it resting on the bottom because the lightning strike blew little holes through the fiber glass all around at the water line.

Just a thought.
Ron

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Champipple
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Response Posted - 07/19/2007 : 21:11:10

Arlyn - you didn't give any further details, can you elaborate why you think this is Junk Science?

It appears to have been government funded and doesn't seem to have commercial backing. That is to say the advertisement for 8 guage stranded copper and the New Marine discharge plating system weren't in there. By definition it meets that daubert standard as not being junk science.

I don't necessarily agree with everything the guy says, but with the exception of small sample sizes I don't see what you are - can you elaborate?

Edited by - on

Dave Bristle
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Djibouti
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Response Posted - 07/19/2007 : 21:21:58

The background is all here...

http://www.catalina-capri-25s.org/forum/topic.asp?ARCHIVE=true&TOPIC_ID=4747

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Champipple
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Response Posted - 07/20/2007 : 06:58:46

Okay - makes a bit more sense now. I only read the one link and wasn't aware of many of the others that were apparently removed.

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DaveR
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Response Posted - 07/20/2007 : 07:39:15

Oops

,
<blockquote id="quote">quote:<hr height="1" noshade id="quote">The good news, Dave, is that your system was probably no more of an attractant (or a "good ground") than your backstay and aft chainplate already were. Light-guage stainless steel is only a slightly better conductor than chewing gum.<hr height="1" noshade id="quote"></blockquote id="quote">
I somehow let the fact that the stay material is stainless go flying (sound of a F-22 screaming past) right by, so I called my neighbor and he came over and slapped me, I'm OK now

Edited by - on

Dave Bristle
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Djibouti
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Response Posted - 07/20/2007 : 08:13:38

Arlyn's points in that earlier discussion support my belief that a cabintop-stepped mast doesn't necessarily present a lower-resistence path than the air next to the boat. (Keel-stepped is probably a different matter, but we don't have that.) I suspect his logic can also be expanded to suggest that a boat in salt water is slightly less attractive than one in fresh water, essentially because salt water itself is more attractive than fresh.

My concern is not for the boat or the electronics--let 'em fry, sink, whatever--I don't care. My concern is that if a boat is hit, what happens to any people on board. I think the risk is very high that somebody will be hurt or killed, since the path within the boat is highly problematic no matter what engineering has been done, and the highly conductive human body could alter that path. Also, the magnetic impulse and physical shock wave are no small matter--the fact that they fry electronics from a distance is noteworthy. I believe cardiac arrest is one of the risks when the beast is "in the house" with you.

Therefore, I'll choose to reduce the likelihood of being struck at all--not inviting the beast in--by not grounding. The only sailboats I've known of that were struck were grounded, and fortunately nobody was there. So fortunately I don't know what would have happened to them if they had been.

But hey, my approach is just a roll of the dice, too.

Arlyn's "air gap" device is an interesting concept... Arlyn: Have you developed it any further or taken your ideas to the industry-recognized "experts" (like Don Casey)?

Edited by - Dave Bristle on 07/20/2007 08:24:38

Ed Cassidy
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Response Posted - 07/20/2007 : 09:23:04

As a footnote, I took a ride on a 43 foot catamaran last year that had, from the factory, a large (7/16 inch) braided copper wire running from a device at the top of the mast all the way down, across the deck and into the water between the hulls. At the end of the cable, dangling in the water was what looked like an upside down mushroom, about 5 inches across. The owner told me that if there was a storm nearby, we should not stay topside.

Ed

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Dave Bristle
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Djibouti
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Response Posted - 07/20/2007 : 09:53:41

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Ed Cassidy
 ...I took a ride on a 43 foot catamaran last year that had, from the factory, a large (7/16 inch) braided copper wire running from a device at the top of the mast...<hr height="1" noshade id="quote"></blockquote id="quote">
I'm suspicious that the mast was carbon-fiber, and thus the "need" for a separate conductor. Somebody once told me that virtually no manufacturers put lightning protection in except when it was specified in detail by the customer, and some won't even do that. Too much liability when it turns out not to work. (Plus, what's the definition of "work"??)

Edited by - on

frogger
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Response Posted - 07/20/2007 : 18:55:46

Agree with Arlyn's assessment.

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Oscar
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Response Posted - 07/20/2007 : 20:51:28

Most of what's said above is good. I'll weigh in with a keel stepped mast. I know of a few C-42's that have been hit, I myself have lost some electronics from a nearby cloud-to-water strike. I was not on board.

Catalina opted not to install a bonding system on the 42. So there are no thick wires running from mast to keel, chainplates etc. As there is no consensus regarding this, the advantage of the Catalina approach is that you avoid a lot of galvanic issues.

I have been in some very exciting lightning storms, one as recent as April, 120nm SW of Hatteras.... I don't go below, I have to run the boat, but I do touch the metal as little as possible.....

The only thing I do pro-actively is to wrap the handheld GPS in aluminum foil to create a "Farraday Cage".....now someone will tell me that that is not a tue Farraday cage.....(as the microwave and oven have been debunked....)

Edited by - on

Andy_334
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Response Posted - 07/21/2007 : 07:02:16

This prompted an interesting discussion aboard Jalapeno this week.

We'd recently been caught on a nasty lightning storm that erupted from nowhere.

Referring to the two schools of thought that Champ mentioned, we discussed the following.

A: clip one end of the spin pole to the backstay, and allow the other to trail behind the boat, thus “grounding” the mast.

B: creating a ground would seem to invite lighting aboard, and is thus a really really bad idea!

We were already working on plan C………. get the heck off the lake ASAP! It was the longest 45 minutes of my life. Fortunately it all worked out OK.

Edited by - on

Dave Bristle
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Djibouti
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Response Posted - 07/21/2007 : 09:50:56

Andy: C is always the best solution, and no matter what you do or don't do, it will be a "long 45 minutes"! Hopefully, you get the idea that A just won't work very well. But for the same reasons Catalina doesn't get into it, I'm compelled to say again that I'm describing my own thought-process. Each skipper needs to do the same thing for him/herself.

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Arlyn Stewart
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Response Posted - 07/21/2007 : 10:03:09

Duane... you have probably read by now my objections to Dr Thomson's conclusions but I'll restate them here for those who don't wish to labor through the full article I wrote.

He concludes that his study shows that lightning hits both grounded and ungrounded mast in about equal numbers based on the surveyors reports of how many mast were grounded and how many were not in his study. The problem with this is that his basis for calling a mast grounded was if it had a lightning protection system installed and he either by oversight or otherwise fails to account that there are other ways a mast may be grounded and in fact most inboard boats are incidentally grounded by lighting, instrument or radio circuitry.

This means that it is theoretically possible that all the boats in his survey had grounded mast, making his conclusion that grounded and ungrounded mast are hit in equal numbers a false conclusion. To add to this, Thomson is in the business of selling protection systems as well as he is a gun for hire as an expert witness in boating litigation involving lightning and has gone on the record stating that to not have a lightning protection system is negligent. This man is using his false conclusions for profit.

It should be noted that a fellow associate electrical engineering professor from the Florida University System has stated has stated that "grounding the mast could increase chances of being hit" (reference in my article). Though he doesn't deal with Thomson, it seems to me that his statement is a departure from giving credit to his colleagues theory.

Having said that... I agree with Thomson's conclusions that having a protections system would reduce the damage and risk of injury from a strike on a blue water boat but I'd suggest an electrical engineer is not needed to make that conclusion... probably most 8th grade science students would conclude that.

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Champipple
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Response Posted - 07/21/2007 : 11:53:39

I'm ungrounded and believe that is the way to go.

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Arlyn Stewart
 Duane... you have probably read by now my objections to Dr Thomson's conclusions but I'll restate them here for those who don't wish to labor through the full article I wrote.

He concludes that his study shows that lightning hits both grounded and ungrounded mast in about equal numbers based on the surveyors reports of how many mast were grounded and how many were not in his study. The problem with this is that his basis for calling a mast grounded was if it had a lightning protection system installed and ... ... ...

This means that it is theoretically possible that all the boats in his survey had grounded mast, making his conclusion that grounded and ungrounded mast are hit in equal numbers a false conclusion.

<hr height="1" noshade id="quote"></blockquote id="quote">

I was under the impression that to be considered grounded you had to meet the requirements as noted by US Government code - since that was what he was testing therefore grounded boats (by his definition) vs ungrounded boats came out equal...I don't think he tried to hide that. 
<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Arlyn Stewart

To add to this, Thomson is in the business of selling protection systems as well as he is a gun for hire as an expert witness in boating litigation involving lightning and has gone on the record stating that to not have a lightning protection system is negligent. This man is using his false conclusions for profit.
<hr height="1" noshade id="quote"></blockquote id="quote">

Didn't know this not sure how I ight have either. Professional witnesses writing white papersisn't anything new. It is probably the norm. I don't know which came first in his case, the paper or the lightning- though it shouldn't matter. 

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Arlyn Stewart
Having said that... I agree with Thomson's conclusions that having a protections system would reduce the damage and risk of injury from a strike on a blue water boat but I'd suggest an electrical engineer is not needed to make that conclusion... probably most 8th grade science students would conclude that.
<hr height="1" noshade id="quote"></blockquote id="quote">

I've seen a grounded boat with the bow and stern blown out with softball size holes and I've seen an ungrounded boat get about 15 dime sized holes in a shotgun spray pattern with the radio still working afterward.
I've given up on what actually might be better in general, or on Lake Erie. Grounding requires energy and in general I'm a lazy SOB - so I think I'll be ungrounded for a while...


actually now that I think about it, I don't know if the new boat is grounded or not, Though the antenna is attached to the radio which is attached to the board which is attached to the battery which is attached to the starter which is attached to the universal which is attached to the prop....is that a straight enough line?

Edited by - on

Oscar
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Response Posted - 07/21/2007 : 17:17:16

<blockquote id="quote">quote:<hr height="1" noshade id="quote">plan C………. get the heck off the lake ASAP<hr height="1" noshade id="quote"></blockquote id="quote">

DANGER....DANGER.....it works if you make it, but if you ALMOST make it you are worse off then if you were on the lake......negotiating harbour entrances, or docking in 50 knot gusts (saw those the other day coming out of a black cloud.....) is potentially much more hazardous than the risk of getting struck out there....plus, you can also get struck in dock.

Many a pilot has lost the race to the airport with a thunderstorm, and they were four times as fast as the storm.....most storms are 5 or more times faster than your sailboat.....

When in doubt, stay out.....sea room is GOOD!

Edited by - on

Arlyn Stewart
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Response Posted - 07/22/2007 : 08:40:44

<blockquote id="quote">quote:<hr height="1" noshade id="quote">I was under the impression that to be considered grounded you had to meet the requirements as noted by US Government code - since that was what he was testing therefore grounded boats (by his definition) vs ungrounded boats came out equal...I don't think he tried to hide that. <hr height="1" noshade id="quote"></blockquote id="quote">

If he used that definition to proffer that grounded and ungrounded are hit equally... it would have been lame for an electrical engineer to do so because the attachment spark theory has long been established as increasing the chances of being struck here at this point that will sustain an attachment spark.

To proffer his theory that grounded and ungrounded are hit in equal numbers, he knows he must then supply a theory as to why ungrounded mast can supply that spark.

So, he lays out an unproven theory having no test, data, or corroborating science of how ungrounded mast can do that. What is strange is that he completely ignores the likelihood that many of the boats without lightning protection systems (he is calling ungrounded) could have incidental grounded mast and therefore could fit the model of a boat having a grounded mast that could sustain an attachment spark.

It was an electrician that pointed me to the incidental grounding that Thomson omitted. One would think that an electrical engineer professor would be aware but he makes absolutely no mention of incidental grounding. Why not?

A few words about incidental grounding and why it is relevant to this. Traditionally Ham radio operators had as their upper tower structure, a large horizontal beam antenna for working HF radio frequencies. Then in the seventies and eighties there was a huge proliferation of VHF FM repeaters around the country and to work these many repeaters Hams placed vertical antennas on the stinger pole above the horizontal HF beam. The advantage was that the vertical antenna could hear and work repeaters in any direction without being rotated. The most popular of these antenna had a loading coil just as most sailboats use that cause the stinger to have ground potential even though the wire feeding the stinger is smaller than that feeding a typical lighting fixture on a sailboat mast.

The result was that Hams took hits in unprecedented numbers and now no ham that is informed will put such a coil loaded vertical antenna above his horizontal beam. The reason as outlined by electrical engineers is simple. A horizontal beam harmlessly bleeds off the accumulation of free electrons pulled to the top of the tower and offers no single point collecting and dispersion point needed for sending an attachment spark as did the vertical antenna. Now aware, Hams have returned to the occasional hit ratios.

Again, whether oversight or overt... not factoring incidental grounding negates Dr. Thomson's conclusion.

Edited by - on

Dave Bristle
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Djibouti
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Response Posted - 07/22/2007 : 10:26:11

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Oscar
 When in doubt, stay out.....sea room is GOOD!<hr height="1" noshade id="quote"></blockquote id="quote">
Good point, Oscar! Inlets can be incredibly nasty, with standing waves that feel like they're going to eject you from the cockpit. And a 5500# boat can do some damage to itself, other boats, and the limbs of people trying to horse it around a dock in a big blow. With all sails down and the motor running, a C-25 can take a pretty big squall line. If the motor won't hold her head-to-wind, an anchor or drogue are helpful.

However, some blows are a lot more tolerable in a 42-footer than in a 25-footer... I generally ran for cover--and generally early.

Edited by - on

Andy_334
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Response Posted - 07/22/2007 : 20:46:49

Oscar, I take your point. Your analogy about aircraft is an interesting one. At the moment we were caught out, all we wanted to do was run for home. We’re on a small inland lake, without many of the coastal hazards. However, when the whiteout occurred we were ready to drop anchor to prevent drifting onto the shore.

I believe our on-boat discussion is done. The owner wants to avoid anything that will attract lightning, including not being there in the first place. I’m not about to argue with him.

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