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#1
posted to rec.boats.cruising
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Emergency lightning protection
Like the vast majority of fiberglass boat owners, I'm sailing around in a
boat with next to no lightning protection. I have run a heavy copper grounding wire from a chain plate to a couple of through hulls directly below. That will help bleed off some charge and slightly reduce the chance of being struck. If I am hit however, I imagine it will make the results worse. This is on my "someday" list and would be on the "already done" list if I sailed more to the south. I nearly 40 years of sailing in this part of the world, I've only once been in a situation that I was huddled below trying to figure out the best place to be when the bolt hit. That was long ago enough that I haven't gotten as worked up about the issues as I should. I don't know as much about the subject as I should since I've spent my professional life working with boats that have metal masts welded on top of metal superstructures welded to metal hulls. So, I throw out this idea for comment as a suggestion for either an interim solution or for cruising grounds where energetic storms are too infrequent to justify a major retrofit. How about a couple of plastic coated battery cables with a snap shackle on one end and a length of chain on the other. If it looks like you are going to get caught right in the path of an energetic storm, the kind where you'll want to either anchor or drift while you seek the safest place in the boat, just clip them to the shrouds and drop over the side. Nearly straight run down from the stays (at least if chain plates are not too far inboard), lots of surface area in the chain, plastic coated wire to protect the topsides. You wouldn't want to cruise around with this rig but it seems like it might at least keep a strike from sinking the boat by blowing a hole in it. -- Roger Long |
#2
posted to rec.boats.cruising
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Emergency lightning protection
Roger,
I like that idea but we need to work on the snap shackle because there would be an increased resistance right there. Ansley Sawyer |
#3
posted to rec.boats.cruising
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Emergency lightning protection
The resistance profile may reveal that the shroud becomes the main
dissapative element in the discharge path. It may well vaporize, and you at sea with sails in a squall? Every earth bond will include a weak link, which will burn out first, causing x-metal vapour arc to be temporarily included in an established hi current stroke discharge, if the bolt be juicy enough. I would not want it to be a shroud which parts, possibly leaving me a pedestrian. Ground the base of the mast as directly as possible to a bare keel or clean plate, keeping in mind you must plan a fusible weak point somewhere, but hopefully not where it will cause the mistress to burn her bum. My weak point is the four smallish bolts penetrating the overhead at the tabernacle. My backup is that the shrouds should position the mast heel adequately should all four bolts get burned off. My proof is 25 holes burned in the old mast, repetitively struck by a biggie. The path presented it's main resistance effect in two distinct areas: The burn craters in the mast surface, strangely all at the same point of curvature on the mast surface, and the keel bolt, which cracked the fiberglass around it's bedding, to the tune of a new leak, about one drop every five minutes. The bolt is fatter stainless than the copper ground wire. I would not want to be making connections grounding equipment once the storm gets close enough to make it seem an urgent neccessity, I would likely better be employed reefing or something. Then, I'll go below and sit under a grounded umbrella, hugging the rum bottle and whistling for a taxi. I would have disconnected the VHF AE, but then the steaming lamp would not work, besides I wasn't there at the time and had not thought to do so when I left the boat at the dock. No need, I suspect because the VHF survived the lightning stike. Terry K |
#4
posted to rec.boats.cruising
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Emergency lightning protection
"Terry K" wrote in message oups.com... The resistance profile may reveal that the shroud becomes the main dissapative element in the discharge path. It may well vaporize, and you at sea with sails in a squall? Every earth bond will include a weak link, which will burn out first, causing x-metal vapour arc to be temporarily included in an established hi current stroke discharge, if the bolt be juicy enough. I would not want it to be a shroud which parts, possibly leaving me a pedestrian. Ground the base of the mast as directly as possible to a bare keel or clean plate, keeping in mind you must plan a fusible weak point somewhere, but hopefully not where it will cause the mistress to burn her bum. My weak point is the four smallish bolts penetrating the overhead at the tabernacle. My backup is that the shrouds should position the mast heel adequately should all four bolts get burned off. My proof is 25 holes burned in the old mast, repetitively struck by a biggie. The path presented it's main resistance effect in two distinct areas: The burn craters in the mast surface, strangely all at the same point of curvature on the mast surface, and the keel bolt, which cracked the fiberglass around it's bedding, to the tune of a new leak, about one drop every five minutes. The bolt is fatter stainless than the copper ground wire. I would not want to be making connections grounding equipment once the storm gets close enough to make it seem an urgent neccessity, I would likely better be employed reefing or something. Then, I'll go below and sit under a grounded umbrella, hugging the rum bottle and whistling for a taxi. I would have disconnected the VHF AE, but then the steaming lamp would not work, besides I wasn't there at the time and had not thought to do so when I left the boat at the dock. No need, I suspect because the VHF survived the lightning stike. Terry K |
#5
posted to rec.boats.cruising
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Emergency lightning protection
"Terry K" wrote The resistance profile may reveal that the shroud becomes the main dissapative element in the discharge path. It may well vaporize, and you at sea with sails in a squall? My rig would stand without the forward lowers which I would use. Ground the base of the mast as directly as possible to a bare keel or clean plate, keeping in mind you must plan a fusible weak point somewhere, but hopefully not where it will cause the mistress to burn her bum. I'm not talking about doing it right here or protecting the boat. The only aim is to increase the chances of remaining alive on a possibly wrecked boat to deal with the aftermath. I'm just looking for a quick stop gap to at least do something until I can put in a proper system. It's tough on a boat with ballast encapsulated inside a fiberglass keel. I would not want to be making connections grounding equipment once the storm gets close enough to make it seem an urgent neccessity That's the reason for rapid deployment. BTW doppler radar available on your cell phone from the Weather Channel is a great service where there is coverage. I've used it both flying and boating to avoid and plan for storms. I'm glad I sail and plan to sail where there aren't a lot of thunderstorms. Most of them lose a lot of steam when they get to the cold water in this part of the world. They continue to rumble with cloud to cloud strikes but not many of them are still putting out a lot of cloud to ground strikes. I can't remember hearing of a vessel struck north of Cape Cod although I'm sure it has happened. -- Roger Long |
#6
posted to rec.boats.cruising
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Emergency lightning protection
Roger Long wrote: I'm not talking about doing it right here or protecting the boat. The only aim is to increase the chances of remaining alive on a possibly wrecked boat to deal with the aftermath. I'm just looking for a quick stop gap to at least do something until I can put in a proper system. It's tough on a boat with ballast encapsulated inside a fiberglass keel. You've just figured out another important design criterion for a sailboat--proper grounding for lightning protection. It needs to be done as part of the design, instead of as an afterthought. Regarding your aim of increasing your chances of remaining alive, I'm not sure if you are talking about surviving the strike itself, or possibly a sinking caused by the strike. Don W. |
#7
posted to rec.boats.cruising
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Emergency lightning protection
Don W wrote:
Roger Long wrote: I'm not talking about doing it right here or protecting the boat. The only aim is to increase the chances of remaining alive on a possibly wrecked boat to deal with the aftermath. I'm just looking for a quick stop gap to at least do something until I can put in a proper system. It's tough on a boat with ballast encapsulated inside a fiberglass keel. You've just figured out another important design criterion for a sailboat--proper grounding for lightning protection. It needs to be done as part of the design, instead of as an afterthought. Regarding your aim of increasing your chances of remaining alive, I'm not sure if you are talking about surviving the strike itself, or possibly a sinking caused by the strike. Don W. Well, if he don't survive the strike, he probably won't survive the sinking, either. DT |
#8
posted to rec.boats.cruising
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Emergency lightning protection
On Mar 16, 9:58 am, dt wrote:
Don W wrote: Roger Long wrote: I'm not talking about doing it right here or protecting the boat. The only aim is to increase the chances of remaining alive on a possibly wrecked boat to deal with the aftermath. I'm just looking for a quick stop gap to at least do something until I can put in a proper system. It's tough on a boat with ballast encapsulated inside a fiberglass keel. You've just figured out another important design criterion for a sailboat--proper grounding for lightning protection. It needs to be done as part of the design, instead of as an afterthought. Regarding your aim of increasing your chances of remaining alive, I'm not sure if you are talking about surviving the strike itself, or possibly a sinking caused by the strike. Don W. Well, if he don't survive the strike, he probably won't survive the sinking, either. DT A millisecond is a long time for lightning so the solder will probably melt but will last long enough to conduct the pulse. The connection is also crimped. Many boats do get hit and survive and I'd go so far at to say that most survive. You have to remember that at 10,000,000 volts, almost everything looks like a conductor but some are better than others. This means that a wet hull and deck look like perfectly good conductors to the lightning. I have considered connecting the chain plates together and then to the bolts at the mast step (deck stepped mast) to try to make current that goes into the shrouds go back into the grounded cable connected to the mast but this would make a huge loop so am hesitant to do it. I went so far as to use my dremel tool to round all edges on the chain plates to suppress corona discharge from the edges. You want to get that current to ground and do it with a large surface area conductor which is why I use the many stranded wire. The grounded plate has a lot of surface area too. I think that the reason most struck boats survive is that the current travels over the wet deck and hull surface which has huge surface area. I have read that discharge pattersn are common on the outside of struck boats , like Lichtenberg figures. My strategy is to minimize this damage. |
#9
posted to rec.boats.cruising
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Emergency lightning protection
On Mar 15, 3:34 pm, "Roger Long" wrote:
Like the vast majority of fiberglass boat owners, I'm sailing around in a boat with next to no lightning protection. I have run a heavy copper grounding wire from a chain plate to a couple of through hulls directly below. That will help bleed off some charge and slightly reduce the chance of being struck. If I am hit however, I imagine it will make the results worse. This is on my "someday" list and would be on the "already done" list if I sailed more to the south. I nearly 40 years of sailing in this part of the world, I've only once been in a situation that I was huddled below trying to figure out the best place to be when the bolt hit. That was long ago enough that I haven't gotten as worked up about the issues as I should. I don't know as much about the subject as I should since I've spent my professional life working with boats that have metal masts welded on top of metal superstructures welded to metal hulls. So, I throw out this idea for comment as a suggestion for either an interim solution or for cruising grounds where energetic storms are too infrequent to justify a major retrofit. How about a couple of plastic coated battery cables with a snap shackle on one end and a length of chain on the other. If it looks like you are going to get caught right in the path of an energetic storm, the kind where you'll want to either anchor or drift while you seek the safest place in the boat, just clip them to the shrouds and drop over the side. Nearly straight run down from the stays (at least if chain plates are not too far inboard), lots of surface area in the chain, plastic coated wire to protect the topsides. You wouldn't want to cruise around with this rig but it seems like it might at least keep a strike from sinking the boat by blowing a hole in it. -- Roger Long Check out the following website: http://www.marinelightning.com/ And the interview of the proprietor (Dr. Ewen Thomson) at: http://furledsails.com/article.php3?article=676 The Furled Sails interview was quite interesting and the inventor discussed both the product and his thinking behind it in detail, as well as Boat U.S. insurance stats on the frequency of lightening strikes. The web site has a variety of information as well. As for the odds of being hit, the odds are greater if you are in Florida or own a catamaran, and Charlie's advice about mooring near taller targets is apt, as boats in marinas / crowded harbors, have lower risk as well. Steve Hayes |
#10
posted to rec.boats.cruising
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Emergency lightning protection
On Thu, 15 Mar 2007 15:34:33 -0400, "Roger Long"
wrote: How about a couple of plastic coated battery cables with a snap shackle on one end and a length of chain on the other. If it looks like you are going to get caught right in the path of an energetic storm, the kind where you'll want to either anchor or drift while you seek the safest place in the boat, just clip them to the shrouds and drop over the side. Most really large sailboats use zinc fish with an attached wire and alligator clip. You can buy these at West Marine and other chandleries. One on each upper shroud is a good start, and you can also put one on the headstay and backstay (assuming it isn't insulated. I use one on each side of my trawler mast when docked, or at anchor in threatening weather. In the end it's all luck however, lightning is very capricious stuff. http://tinyurl.com/zttlk |
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