For most of the country its that time of the year again. I would like to throw the lightning topic on the board for opinions and feedback on experiences of dealing with the threat of it. I would appreciate opinions on strike prevention techniques such as mast head dissipaters, cone of protection theories, the old jumper cables over the side technique, etc.,. Risk of strike differences between deck stepped and keel stepped masts. In that all info on lightning strikes is theory for the most part does anyone feel that efforts taken to bond lifeline stanchions is worth the effort. Being that the factory installed bonding did not include the stanchions makes me wonder if it is a sensible effort to undertake. One does wonder why the the shrouds would be bonded and not the stanchions in case of flashing. I have never been comfortable with the light duty connectors on the ends of the bonding wires at the seacocks, chainplates etc., and find it hard to believe they would be capable of handling the voltage and current in a direct strike in leading the strike safely to ground. Has anyone changed to a more typical heavy duty grounding lug as used on a/c motors or similar? If so were they screwed tight, crimped, soldered or brazed to the conductor? Has anyone increased the bonding wire gauge? What size and why? Stranded or solid core? Why? Does lightning voltage pass on the surface of a conductor or throughout the core? Does having electronics turned on add to the strike potential of the boat by adding to the boats static charge? How much of a roll does a stainless masthead whip antenna contribute to strike potential? Would a static dissipater still be effective if mounted at a lower height than the tip of the antenna? What about wind vanes in the equation? Would a radar dome operating attract strikes? What about a transmission over SSB through a backstay antenna? Or even over the VHF for that matter? I've looked at two strike preventers (reducers), one of which is the multi wire dissipaters that supposedly maximize ion dissipation and reduce the static charge buildup of the vessel. The other is the more typical pointed lightning rod that claims to do the same. Has anyone had experience with either of these? Who has been hit and what were the conditions and what were the results? Is your heart still in your throat! I and several others almost got hit several years ago while standing next to a marina building. A strike came from a wispy looking sky and struck the 6 foot VHF antenna that was mounted on the building about 15' from us. I can still hear that god awful sizzle and crack as it struck. We all stared blankly at one another. Plenty of masts sticking up a lot higher than the VHF antenna. Do you wonder? I recall another time in the midwest when a 25' sail on a trailer with the mast down was struck on the stern rail and it left the boat with thousands of holes the diameter of a pin all through the stern area of the hull. When viewed from inside the hull on a sunny day it looked like the Milky Way. Aside from the burn mark on the rail and the thousands of tiny holes you would never have known the boat was hit. I look forward to some interesting posts regarding this serious and all to important but very overlooked subject. Any good boat/lightning websites?
lightwork@earthlink.net
lightning , lightning - ZAP, SIZZLE - protection
Moderator: Jim Walsh
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Tom Coons
Re: lightning , lightning - ZAP, SIZZLE - protection
John wrote: For most of the country its that time of the year again. I would like to throw the lightning topic on the board for opinions and feedback on experiences of dealing with the threat of it. I would appreciate opinions on strike prevention techniques such as mast head dissipaters, cone of protection theories, the old jumper cables over the side technique, etc.,. Risk of strike differences between deck stepped and keel stepped masts. In that all info on lightning strikes is theory for the most part does anyone feel that efforts taken to bond lifeline stanchions is worth the effort. Being that the factory installed bonding did not include the stanchions makes me wonder if it is a sensible effort to undertake. One does wonder why the the shrouds would be bonded and not the stanchions in case of flashing. I have never been comfortable with the light duty connectors on the ends of the bonding wires at the seacocks, chainplates etc., and find it hard to believe they would be capable of handling the voltage and current in a direct strike in leading the strike safely to ground. Has anyone changed to a more typical heavy duty grounding lug as used on a/c motors or similar? If so were they screwed tight, crimped, soldered or brazed to the conductor? Has anyone increased the bonding wire gauge? What size and why? Stranded or solid core? Why? Does lightning voltage pass on the surface of a conductor or throughout the core? Does having electronics turned on add to the strike potential of the boat by adding to the boats static charge? How much of a roll does a stainless masthead whip antenna contribute to strike potential? Would a static dissipater still be effective if mounted at a lower height than the tip of the antenna? What about wind vanes in the equation? Would a radar dome operating attract strikes? What about a transmission over SSB through a backstay antenna? Or even over the VHF for that matter? I've looked at two strike preventers (reducers), one of which is the multi wire dissipaters that supposedly maximize ion dissipation and reduce the static charge buildup of the vessel. The other is the more typical pointed lightning rod that claims to do the same. Has anyone had experience with either of these? Who has been hit and what were the conditions and what were the results? Is your heart still in your throat! I and several others almost got hit several years ago while standing next to a marina building. A strike came from a wispy looking sky and struck the 6 foot VHF antenna that was mounted on the building about 15' from us. I can still hear that god awful sizzle and crack as it struck. We all stared blankly at one another. Plenty of masts sticking up a lot higher than the VHF antenna. Do you wonder? I recall another time in the midwest when a 25' sail on a trailer with the mast down was struck on the stern rail and it left the boat with thousands of holes the diameter of a pin all through the stern area of the hull. When viewed from inside the hull on a sunny day it looked like the Milky Way. Aside from the burn mark on the rail and the thousands of tiny holes you would never have known the boat was hit. I look forward to some interesting posts regarding this serious and all to important but very overlooked subject. Any good boat/lightning websites?
I hope you get some answers. I'd like to know also. Let me put in the very little bit I know. As far as I've been able to discover nobody really has the definitive answer to these questions. There are many opinions just as engineers often say there is no such thing as an airfoil and boats sailing upwind has to do with wind vectors. One school on lighning says that you've got a big charge looking for a place to strike and go to ground. If you put a lightning rod up there and give it a path via your boat you INCREASE your chance of getting hit, thus you don't want big wires that run to ground up there on your mast. The other school says that you're the tallest thing around and the charge is looking for something to strike so you're probably going to get it regardless, thus is is better to be prepared and have paths that will minimize scattering by taking it directly to ground. We don't have many electrical storms here on the west coast and I've never been struck by lightning so have no empirical evidence. I figured that Cape Dory comes from an area where you do have electrical storms so they probably know best and accept that everything is bonded together and grounded. The one piece of empirical sea lore that I have it that the boatyard workers.in West Palm Beach told me that if you have a stainless steel mast cap that you never get hit, every mast that they had seen that had been hit had an aluminum cap just like the mast. Or was it the other way around? Anyway my Cape Dory 31 had the right kind of cap to not get hit. I don't put this out as truth. I don't know how much the yard guys knew, maybe they'd just had a run of aluminum strikes and every one since I left has been the other way around. Maybe someone on the web has been hit and can tell us about the size wires and so on. They look small to me too, but I thought the wires to fill caps and seacocks weren't for lightening protection, but for static electricity and electrolysis protection. Logically it doesn't seem like SSB or other radio transmissions would draw lightning because I think it's a positive charge being put out and uses the ocean for "earth" ground so it would be two positive charges repelling rather than a negative charge attracting.
taccambria@thegrid.net
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Walt Bilofsky
Re: lightning , lightning - ZAP, SIZZLE - protection
Most of the discussion I've seen on lightning protection talks about the need to run a thick straight cable from the lightning rod to a good ground plate. And if you are going to get struck, it will likely be on the lightning rod if one is installed.
But what I recall from high school physics is that the main function of the lightning rod is to provide a path to leak off the electrical charge so that you don't get struck. To see how this works, picture the electrical potential in the air as depicted by contour lines. There's a fairly even distribution in the air. Now if the boat gets charged preparatory to a strike, all of a sudden there's a big potential difference - so lots of contour lines between the boat and the air. Around a sharp object like the lightning rod, the contour lines all bunch together at the point - that is, there's a concentration of voltage gradient - and this induces the charge to leak off into the air.
For whatever it's worth.
bilofsky@toolworks.com
But what I recall from high school physics is that the main function of the lightning rod is to provide a path to leak off the electrical charge so that you don't get struck. To see how this works, picture the electrical potential in the air as depicted by contour lines. There's a fairly even distribution in the air. Now if the boat gets charged preparatory to a strike, all of a sudden there's a big potential difference - so lots of contour lines between the boat and the air. Around a sharp object like the lightning rod, the contour lines all bunch together at the point - that is, there's a concentration of voltage gradient - and this induces the charge to leak off into the air.
For whatever it's worth.
bilofsky@toolworks.com
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Linda
Re: lightning , lightning - ZAP, SIZZLE - protection
It was interesting reading your concerns..We have our own since our CD27 took a direct hit of lightning! Two years ago we bought this boat and I decided to look into her history ...where she had been, hurricane survival and previous owners, etc.. What I did find I out shocked me. Our cape dory (in its region of manufacture) took a direct hit while the owners were not on board. The lightning blew out the seacocks and she sank to the bottom in 10' of water. He told me it was a good thing she sank otherwise she would have burned to a crisp......how comforting! This does not give me any comfort at all when I hear the rumble of thunder overnight in some port away from home.
Maybe the fellow who owned her while she took the strike reads this board and might give you some more detailed input......
About a month ago we visited the boatyard/dealer where she was originally purchased. We stopped in for a chat wondering if they remembered the boat......"Oh yeh, she was the one we retrieved off the bottom after she took that lightning strike!"........They brought her right up. Now after looking into the past we understand why we have a 2GM engine and 1984 wiring on our 1979 CD. Many questions were anwered in our minds as that owner told me how the boat went down and how electronics and the engine were effected.
Last summer we got caught coming into Martha's Vineyard with a storm developing right in front of us with no place for us to go so we quickly took "safe shelter" next to a 40+' and felt better. All was OK. Someone else who is taller looks like a more likely candidate. At our home mooring our "next door neighbors" are a CD 30 and a Hunter 42' and we figure they stand a little highter in the sky! ----- Year after year someone gets struck in our small marina. Masts are struck -wood or aluminum but that steel crane that sticks sky high on the blacktop never gets it!
My house was struck as a kid while I was at home and we all survived but it is the most vivid of memories! I don't ever want to get that close again especially while on the boat..................Glad to hear you survived and I understand your concern......
Linda, CD27 Chartley (with an aluminum mast cap)
Cdchartley@aol.com
Maybe the fellow who owned her while she took the strike reads this board and might give you some more detailed input......
About a month ago we visited the boatyard/dealer where she was originally purchased. We stopped in for a chat wondering if they remembered the boat......"Oh yeh, she was the one we retrieved off the bottom after she took that lightning strike!"........They brought her right up. Now after looking into the past we understand why we have a 2GM engine and 1984 wiring on our 1979 CD. Many questions were anwered in our minds as that owner told me how the boat went down and how electronics and the engine were effected.
Last summer we got caught coming into Martha's Vineyard with a storm developing right in front of us with no place for us to go so we quickly took "safe shelter" next to a 40+' and felt better. All was OK. Someone else who is taller looks like a more likely candidate. At our home mooring our "next door neighbors" are a CD 30 and a Hunter 42' and we figure they stand a little highter in the sky! ----- Year after year someone gets struck in our small marina. Masts are struck -wood or aluminum but that steel crane that sticks sky high on the blacktop never gets it!
My house was struck as a kid while I was at home and we all survived but it is the most vivid of memories! I don't ever want to get that close again especially while on the boat..................Glad to hear you survived and I understand your concern......
Linda, CD27 Chartley (with an aluminum mast cap)
John wrote: For most of the country its that time of the year again. I would like to throw the lightning topic on the board for opinions and feedback on experiences of dealing with the threat of it. I would appreciate opinions on strike prevention techniques such as mast head dissipaters, cone of protection theories, the old jumper cables over the side technique, etc.,. Risk of strike differences between deck stepped and keel stepped masts. In that all info on lightning strikes is theory for the most part does anyone feel that efforts taken to bond lifeline stanchions is worth the effort. Being that the factory installed bonding did not include the stanchions makes me wonder if it is a sensible effort to undertake. One does wonder why the the shrouds would be bonded and not the stanchions in case of flashing. I have never been comfortable with the light duty connectors on the ends of the bonding wires at the seacocks, chainplates etc., and find it hard to believe they would be capable of handling the voltage and current in a direct strike in leading the strike safely to ground. Has anyone changed to a more typical heavy duty grounding lug as used on a/c motors or similar? If so were they screwed tight, crimped, soldered or brazed to the conductor? Has anyone increased the bonding wire gauge? What size and why? Stranded or solid core? Why? Does lightning voltage pass on the surface of a conductor or throughout the core? Does having electronics turned on add to the strike potential of the boat by adding to the boats static charge? How much of a roll does a stainless masthead whip antenna contribute to strike potential? Would a static dissipater still be effective if mounted at a lower height than the tip of the antenna? What about wind vanes in the equation? Would a radar dome operating attract strikes? What about a transmission over SSB through a backstay antenna? Or even over the VHF for that matter? I've looked at two strike preventers (reducers), one of which is the multi wire dissipaters that supposedly maximize ion dissipation and reduce the static charge buildup of the vessel. The other is the more typical pointed lightning rod that claims to do the same. Has anyone had experience with either of these? Who has been hit and what were the conditions and what were the results? Is your heart still in your throat! I and several others almost got hit several years ago while standing next to a marina building. A strike came from a wispy looking sky and struck the 6 foot VHF antenna that was mounted on the building about 15' from us. I can still hear that god awful sizzle and crack as it struck. We all stared blankly at one another. Plenty of masts sticking up a lot higher than the VHF antenna. Do you wonder? I recall another time in the midwest when a 25' sail on a trailer with the mast down was struck on the stern rail and it left the boat with thousands of holes the diameter of a pin all through the stern area of the hull. When viewed from inside the hull on a sunny day it looked like the Milky Way. Aside from the burn mark on the rail and the thousands of tiny holes you would never have known the boat was hit. I look forward to some interesting posts regarding this serious and all to important but very overlooked subject. Any good boat/lightning websites?
Cdchartley@aol.com
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Dana Arenius
Re: lightning , lightning - ZAP, SIZZLE - protection
Gee John, you have covered most of the questions folks generally ask in your opening posting! And at this time of year!
I like to think of lightning protection in an order of priority.
1. Crew protection
2. Then the boat
3. Then the equipment (engine, electronics, etc.)
As you probably already know, there is a vast difference in electrical bonding of seacocks, engine block, mast, etc. between those sailboats which have inboards and those which have outboards. With an inboard engine, manufacturers really go to town on bonding. Hardly anything on the outboard sailboat. This electrical bonding was for the assumed
shore power AC short circuit protection. It prevents any major metallic object on the boat from becoming "activated" with the hot AC power without tripping the breaker. The wire/cable size of this bonding system was not sized or intended for lightning protection. Its use was designed for a different kind of protection, the AC shore power kind.
But if you connect that AC shore bonding wire to the mast, then I believe you have actually set yourself in creating quite a static electrical charge buildup at the top and may actually attract lightning. I can imagine a strike traveling all around inside a boat (i.e. the engine, the seacocks, wiring harness, etc. before finding it way out the seacocks to earth ground. If you are plugged into shore power at the time, then you really have a good wide ground plane potential for lightning to shoot for.
I do not have to depend on an electrical bilge pump, so generally I do not leave my boat plugged into shore power. With AC bonded seacocks I figure one can avoid those improperly reversed polarity neighbors who may be unknowingly placing stray electrical currents into the water. One hears of stories of seacocks, etc. eaten away as ones gounded seacocks provide a nice grounded return path for the current.
If you are a lightning rod kind of person, you generally believe in trying to direct the strike to ground at the risk of possibly attracting lightning. That is to say, if lightning is going to strike around your boat, your boat will be hit. Ones hope is that it is directed so that the crew is not hurt and one believes it will travel along its intended cable. This is why many folks probably believe in hanging a set of car jumper cables over the side, attached to the mast or shrouds. They believe the strike will be directed to the water, not through the boat like the seacocks or fiberglass skin. This method still presents the question of lightning attraction. Of course, many recognize that lightning protection cable is usually braided and very heavy stuff. Nothing like the AC bonding wiring. And the cable has to run as straight as possible to ground. A tough thing to do properly on a boat.
It is a tough question for most boaters to answer. I could see a mast with properly sized cable, connected thru an air-gap lightning arrestor to a proper thru hull conductor or over the side. By air-gap, I mean two electrodes separated by a short span of air. The thought is the lighting would jump the short air gap if the mast was struck. The same air gap would help to prevent the static charge from building at the top of the mast compared to the directly electrically connected mast to the water. A proper thru hull which can withstand the high currents is another question. Anyone know of any?
Dana
darenius@aol.com
I like to think of lightning protection in an order of priority.
1. Crew protection
2. Then the boat
3. Then the equipment (engine, electronics, etc.)
As you probably already know, there is a vast difference in electrical bonding of seacocks, engine block, mast, etc. between those sailboats which have inboards and those which have outboards. With an inboard engine, manufacturers really go to town on bonding. Hardly anything on the outboard sailboat. This electrical bonding was for the assumed
shore power AC short circuit protection. It prevents any major metallic object on the boat from becoming "activated" with the hot AC power without tripping the breaker. The wire/cable size of this bonding system was not sized or intended for lightning protection. Its use was designed for a different kind of protection, the AC shore power kind.
But if you connect that AC shore bonding wire to the mast, then I believe you have actually set yourself in creating quite a static electrical charge buildup at the top and may actually attract lightning. I can imagine a strike traveling all around inside a boat (i.e. the engine, the seacocks, wiring harness, etc. before finding it way out the seacocks to earth ground. If you are plugged into shore power at the time, then you really have a good wide ground plane potential for lightning to shoot for.
I do not have to depend on an electrical bilge pump, so generally I do not leave my boat plugged into shore power. With AC bonded seacocks I figure one can avoid those improperly reversed polarity neighbors who may be unknowingly placing stray electrical currents into the water. One hears of stories of seacocks, etc. eaten away as ones gounded seacocks provide a nice grounded return path for the current.
If you are a lightning rod kind of person, you generally believe in trying to direct the strike to ground at the risk of possibly attracting lightning. That is to say, if lightning is going to strike around your boat, your boat will be hit. Ones hope is that it is directed so that the crew is not hurt and one believes it will travel along its intended cable. This is why many folks probably believe in hanging a set of car jumper cables over the side, attached to the mast or shrouds. They believe the strike will be directed to the water, not through the boat like the seacocks or fiberglass skin. This method still presents the question of lightning attraction. Of course, many recognize that lightning protection cable is usually braided and very heavy stuff. Nothing like the AC bonding wiring. And the cable has to run as straight as possible to ground. A tough thing to do properly on a boat.
It is a tough question for most boaters to answer. I could see a mast with properly sized cable, connected thru an air-gap lightning arrestor to a proper thru hull conductor or over the side. By air-gap, I mean two electrodes separated by a short span of air. The thought is the lighting would jump the short air gap if the mast was struck. The same air gap would help to prevent the static charge from building at the top of the mast compared to the directly electrically connected mast to the water. A proper thru hull which can withstand the high currents is another question. Anyone know of any?
Dana
darenius@aol.com