Date: Sat May 29, 1999 7:27 pm
Heard one excellent seminar on lightning grounds and found that at least our SW is wired correctly, sure hope the rest of the fleet are because of the following. One seaman there had 5, count 5 thru holes blow out and sank after being hit by lightning. Tens of others had complete destruction of electronics because so called marine mechanics had used the lightning ground as ground for the electronics. These vessels were not struck by lightning, but came near and the static buildup on the rigging went right into the electronics by way of the lightning ground destroying the electronics, interesting? Maybe my wife has been right all these years, as she has me disconnect all wiring to our electronics during the summer thunderstorm months. We have been hit twice but never lost any electronics such as GPS, Satnav, loran, depth, speed or wind or vhf radios.
Date: Wed Nov 14, 2001 10:03 am
Has anyone tried the cheap Forspar flywhisk as an ion dissipator? Like much more costly bottle washers also used for the same purpose, their logic is to dissipate electric charges accumulating on the masts, in order to sharply reduce or eliminate the risk of a direct lightning strike. I have two, one on top of each mast, and they attract fun comments!
I have not been struck yet, including amidst a few heavy electrical storms, touch teak!
Our Florida people who are in lightning alley, Don, and others are welcome to comment on what they witness or hear on this simple device, which does not replace serious grounding.
Date:Wed Nov 14, 2001 9:34 pm
Date: Thu Nov 15, 2001 8:17 am
Some years ago I was to have a fascinating discussion with Nigel Calder.
First I must qualify that I am not necessarily a proponent of a great deal of his application of his base of knowledge. I would characterize him as a technical writer who has learned how to make a very comfortable living from publishing his "opinions" with direct relationship to his love of sailing (do I sound jealous?).
Again, I am not a physicist but Calder indicated that electronics damage from direct or spurious static discharge effects were likely as equally directed to the positive DC circuit as were they by the negative circuit's attempt to divert static current to a ground source. He referenced the "fact" that the circuitry was diode protected and that invasion of static current would be thwarted by the various diodes. When I pointed out that electronic diodes are produced and specifically rated to protect circuitry from considerably lower doses than would be exposed to by lightening he switched his "theory" to the protection afforded on the positive side as that provided by an in-line fuse. (In my own estimation; any electrical charge,powerful enough to have leapt a 40,000 foot air-gap certainly should get past a 2.5 amp Buss fuse) He was far more attentive to my observations regarding cruising sails (after my rather sophomoric observations of electrical theory and personal experience found him with little further, 'factual' basis for continued discussion in the electrical arena).
As a young man (1963) in the USN I was trained as a Aviation Machinist Mate, rose rapidly to a youthful but very responsible position as a Plane Captain ( the USAF equivalent, a Crew Chief) on the EC-121. Later I qualified as Flight Engineer, or as the squadron generally referred to us as an "airborne grease monkey". This Lockheed, four engine, intelligence gathering aircraft would be remembered by most as the old Super Constellation of TWA fame.
Don, I mention this only to reference my respect and concurrence with your vast aviation experience;we were to rely heavily on static discharge wicks to protect an incredible amount of electronics stuffed into that old aircraft. Without the benefit of an endless surface water contact to provide a ground source for DC systems, the buildup of static aboard an aircraft can be expected just as a matter of the surface/air friction and those numerous wicks certainly provided adequate path for leaching off the accumulation.
When a sailor has finally experienced St. Elmo's Fire it is generally quite disturbing unless awareness of the phenomenon is a part of their "book" of nautical knowledge. I found its shimmering, glowing and apparent dimension quite fascinating. Although other than a vicious hissing from the VHF I luckily found no negative results from it's visit, I suspect had such a dedicated static path been provided for the visiting charge to quickly seek it's equal and opposite partner I may have been easily able to forego the dubious but fascinating experience.
Where this is leading I have no idea but almost certainly, adding static wicks to, at least, the mastheads and trailing edges of the spreaders would provide a significant measure of additional protection. Plastic radomes, GPS antenna covers, masthead weather sensors and antennae may actually require the additional protection.
Maybe I should write Nigel Calder and ask, no? < my tongue, planted firmly in cheek >
Date: Thu Nov 15, 2001 9:39 am
I believe your hearsay to be a fact, linked to the screen or "Faraday cage" effect provided by the enclosed metallic oven, protecting the content from electromagnetic waves/fields. Make sure you close the door
Date: Thu Nov 15, 2001 12:37 pm
I have followed with interest the discussions regarding lightening strikes. As a result I have determined what happened to us a number of years ago. Allow to explain which should reinforce the good quality of the grounding characteristics of our Seawinds.
On a passage from Whale Cay in the Bahamas to Moorhead City, we were surrounded on night by thunderstorms. They ringed the boat entirely. When my husband came on watch at 4 AM he asked why I had turned off the Maganox Sat Nav. (I was prone to do this at other times because I found it's beat beat beat annoying and Robert refused to disable the noise). I replied that I had not turned the Sat Nav off. It was later found to be "fried" by Magnavox. Robert always felt I was asleep on watch and had missed the lightening strike. Now I know what happened. The installation of the Sat nav re commended connecting directly to the power sourse and grounding to the engine. Which we did rather than to the ground plate. The antenna was on the mizzen mast. Apparently from what I have learned in this discussion, it was static electricity that caused the desmise of the the Sat Nav and not a strike. No other equipment was effected and no other damage done. Now that I have exposed my ignorance, you can all have a good laugh at me.
We have a friend who sustained a strike in the Great Lakes, the electricity elected to go out around the waterline. There were thousands of pin holes around the boat. It required substantial rebuilding to re pair the problem. As I recall not everything on the boat was grounded. Unlike our Seawind where all shrouds, the mast, the self steering gear, thru hulls is all grounded to the ground plate.
Date: Thu Nov 15, 2001 1:17 pm
I suspect that our most recent round of discussion can lend each of us a laugh at ourselves.
No doubt your Sat-Nav fried from an ingestion of static discharge through the antenna and related cable. In theory the antenna cable is grounded to the case and/or chassis of the unit but this was likely insufficient to prevent immediate damage regardless of installation. Fortunately, you suffered no disastrous other effects.
It is always one of the more prevalent fears of sailors to envision the results of a strike or the effects of localized ion discharges. We have tried more to propose what appears to be rational approaches to prevention by preparation. To date, I have read and experienced much regarding the topic and have yet to actually know the answers.
Nature, as often as she undergoes the intensity of analysis, rarely reveals all of her secrets. Had she been so persuaded to do so. in the case of lightening. I feel certain that some enterprising and principled soul would have invented possibly the most important "ounce of prevention" for each of us and prospered greatly by his diligence and enterprise.
The evidence of possibly the most financially successful of these inventions, even today, atop barns and homes all over the world, the lightening rod, remains faithful to date. The grounding lead used was attached to a long metal stake driven deeply into the surrounding soil. Photographic evidence seems to support its frequent success but it has also recorded its failures almost as often.
It is probably very well advised to install a Dynaplate as the dedicated ground connector for all electronics as it appears to offer the most efficient and direct route to the water. Electrically speaking, current certainly seeks the least resistant path but the Dynaplate is ultimately, if remotely, connected to the engine, via the water, through the propshaft and ultimately to the battery ground cable. I find enough reason to suspect that not all of the current from a strike and/or a local static discharge completely dissipates into the surrounding sea. Even that which is directed away from the boat, in the well documented "Faraday Cage Effect", described by the standing rigging, more likely can still affect something of the boat and its inventory. "Fizzz", may be more likely avoided by our various or even combined suggestions but apparently none of us can offer a truly bulletproof prevention as yet.
Fortunately, the most mysterious, unpredictable and challenging aspects of Nature are possibly those that best allow us to see sailing as such an amazing therapy.
Date: Thu Nov 15, 2001 2:03 pm
Fine and humble concluding words from our favorite engineer-philosopher-sailor-quill holder!
I shan't unship my two "whisks" since I still see them on some plane wings, but will thank Neptune and Aeolus every time Pianissimo and all she holds survive any electrical storm. Be well
Date: Thu Nov 15, 2001 5:10 pm
I suggest that the whisks not be consigned to locker space. If they provide nothing more than a level of confidence then you have certainly done more than I have in that area. How many did you say you have? Maybe I should buy myself more confidence then I already have. So far as far as lightening is concerned I may have been more lucky than smart.
I particularly like Don's idea of static discharge wicks. Obviously he has done something right as I'm the one who has replaced my electronic gear twice without being motivated to do anything more intensive about it. Luck cannot last forever. Now that I have all new electronics installed maybe its time for more than a replacement rabbit's foot!
Date: Thu Nov 15, 2001 6:25 pm
Could we define wick vs. whisk?
1. Whisk: I called whisk the funny tuft of stainless steel bristles that spouts at the end of a 20" long stainless tube, flattened at the base with two holes for screwing on a flat surface, in my case the side of my two masts at the top, opposite the antennas.
A more complex and much more expensive unit imitates a foot-high inverted bottle washer.
2. Wick: what is it, please?
Date: Fri Nov 16, 2001 11:20 am
Dear All static & lightning enthusiaists. I'm going to try and clear up the present day thoughts on static and lightning and must advise you that it may not be truth as science continues to learn more each year, but it is all we meer humans possess at this moment in time. First the action, As one sails into an area of thunderstorm activity, both winds and raindrops are applied to the mast and rigging. A static charge is created by friction or the splitting of a water droplet that strikes the surface, one part positive, the other negative. These charges are transfered to the surface and gathers at points and ridges of the conducting surface, and when it accumulates to a sufficient extent to overcome the insulating properties of the atmosphere, it discharges into the atmosphere. This buildup at first is a progressive one, starting as a brush discharge (st. elmo's fire) and growing by ionization. The breakdown follows an irregular path along the line of least resistance. A hundred or more individual discharges may be necessary to complete the path between points of opposite polarity. When this leader stroke reaches its destination, a heavy main stroke immediately follows in the opposite direction. This main stroke is visible lightning, which may be tinted any color, depending on the gases through which it passes. The illumination is due to the high degree of ionization of the air, which causes many of the atoms to be in excited states and emit radiation. St. Elmo's fire is a luminous discharge of electricity from pointed objects such as the masts and yardarms of ships, lightning rods, airplanes static wicks, sailboat whisks, steeples, mountain tops, blades of grass, human hair, arms, etc., when there is considerable difference in the electrical charge between the object and the air. An object from which St. Elmo's fire emanates is in danger of being struck by lightning, since this type discharge may be the initial phase of the leader stroke. Thus the purpose of a grounded lightning system is to bleed off the static charge early before it can build up sufficient to complete the cycle. The uncontrolled variable here is how quickly the static charge builds (controlled by nature) and how quickly you can get rid of it or how effective your system is in getting rid of it. If corrosion is present anywhere on your lightning ground system it acts as an insulator and the charge can not bleed off until its large enough to jump the corrosion and by then we may have enough to complete the cycle and receive a lightning bolt or direct hit. Any sharp point on your vessel will emit static electricity if it builds up enough, the elusive item is how well does each of us clean all the connection points on the lightning ground annually? For myself, its an annual job as soon as the TRW's season is on hand. Well unless I forget, but I'm sure to remember just as the bolts are shooting overhead at night offshore. Remember static charge buildup can destroy electronics, so keep the electronics ground away from the lightning ground. Now if any of you know of a full proof device that will prevent strikes, the insurance companies are interested!!! In my waterfront community each year at least a dozen sailboats are struck. So don't forget to keep those lightning ground connections clean and bright. Hoping this helps and does'nt confuse the issue.
Date: Fri Nov 16, 2001 12:22 pm
Once again you are my hero... I only basically understood the subject matter before today. Understandably now, why I have counted more on luck than effective prevention.
I guess now that the grounding system in Sea Quill has been cleaned and tuned for possibly the first time in 26 years, my annual attention to it gets a far higher priority.
Although the old rabbits foot is beginning to smell a bit, I'll get one of those too.
At least I am not the only one who still believes in the more archaic "fox-tail" and dust bin over vacuums. Sometimes these things just have to come out, sort of therapeutic, you know. Fear of the appearance of getting on in years, I suspect.
Thanks for all of you sharing, it helps. But I actually have two brushes... the in-cabin one and the deck-side brush... over the top, eh?
Date:Sat Nov 17, 2001 9:38 pm