|
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 |
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 |
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 |
Emergency lightning protection
Charlie Morgan wrote:
On Thu, 15 Mar 2007 15:34:33 -0400, "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. Honestly? There is absolutely nothing you can do to a 30 or 40 foot boat to protect it in the slightest. It may make you feel better, but there's truly no way you are going to harness and direct a lightning strike that hits your mast. Lightning will vaporize (literally) your battery cables. POOF! The only thing that MAY help you is to always anchor with boats that have much taller masts than yours. How about a heavy wire connecting keel bolts to mast bolts, less than a foot apart in my bilge? Stephen |
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 |
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 |
Emergency lightning protection
On Thu, 15 Mar 2007 14:22:13 -0700, Stephen Trapani
wrote: How about a heavy wire connecting keel bolts to mast bolts, less than a foot apart in my bilge? That's about as good as it gets, better to use heavy copper braid however. That also makes an excellent ground for your SSB radio. |
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 |
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 |
Emergency lightning protection
Stephen Trapani inscribed in red ink for all to know:
Charlie Morgan wrote: On Thu, 15 Mar 2007 15:34:33 -0400, "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. Honestly? There is absolutely nothing you can do to a 30 or 40 foot boat to protect it in the slightest. It may make you feel better, but there's truly no way you are going to harness and direct a lightning strike that hits your mast. Lightning will vaporize (literally) your battery cables. POOF! The only thing that MAY help you is to always anchor with boats that have much taller masts than yours. How about a heavy wire connecting keel bolts to mast bolts, less than a foot apart in my bilge? Stephen The problem is that a lightening strike is a pulse - it is not DC. Corners in the wire path look like inductors at high frequencies, and may force the lightening to leave the conductor and take a straighter path (at least in its mind) to earth, avoiding the conductor altogether. All wiring paths should be very heavy gauge, and as straight as possible. It might work. It might not, but one always takes the precautions, right? bob s/v Eolian Seattle, where a lightening bolt becomes the first item on the evening news... |
Emergency lightning protection
On Mar 15, 6:58 pm, RW Salnick wrote:
Stephen Trapani inscribed in red ink for all to know: Charlie Morgan wrote: On Thu, 15 Mar 2007 15:34:33 -0400, "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. Honestly? There is absolutely nothing you can do to a 30 or 40 foot boat to protect it in the slightest. It may make you feel better, but there's truly no way you are going to harness and direct a lightning strike that hits your mast. Lightning will vaporize (literally) your battery cables. POOF! The only thing that MAY help you is to always anchor with boats that have much taller masts than yours. How about a heavy wire connecting keel bolts to mast bolts, less than a foot apart in my bilge? Stephen The problem is that a lightening strike is a pulse - it is not DC. Corners in the wire path look like inductors at high frequencies, and may force the lightening to leave the conductor and take a straighter path (at least in its mind) to earth, avoiding the conductor altogether. All wiring paths should be very heavy gauge, and as straight as possible. It might work. It might not, but one always takes the precautions, right? bob s/v Eolian Seattle, where a lightening bolt becomes the first item on the evening news... Having worked with seriously high voltage discharges, I am a little familiar with this topic and even more fearful of lightning than the average sailor. So, I have a 15' length of #00 guage insulated TINNED battery cable of MANY strands (not the normal heavy strands but many smaller strands) to give max surface area. Water end is soldered to a heavy lug on a thin 2.5'X2.5' piece of copper sheet. Other end is bared and soldered to avoid corrosion on the copper. On the mast I have a heavy clamp type lug bolted to the mast (mast is deck stepped) about 4' above deck to minimize the bend in going over the side. The bare soldered end is placed into the clamp connector and it is clamped down and the copper sheet is thrown over the side. If struck, most of the discharge will go through the most direct path, down the mast and into the cable. I expect to get some arcing off the shrouds at the bottom but I think they will survive. I think this is the best I can do. Having been very close to being struck several times even though I was taking precautions, I am very afraid of lightning. A couple years ago, I did a calculation of the probability of a Florida sailor getting his boat hit if he routinely stayed out in thunderstorms and was amazed at how high it was. This was based on the projected area of the mast, number of strikes/yr/km2, etc. I argued back and forth over this with someone from up north on here and eventually found insurance company stats that agreed with mine. |
Emergency lightning protection
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 Roger, If lightning hits your mast, your battery cables and chains are not going to help much, although they probably won't hurt either. I've got the electrical engineering degree with a bunch of experience to back it up, but lightning protection is a specialized black art--even in my field. There are some pretty good explanations on the web by PHd's who have made lightning protection their whole career. Search them out and give them a read. It's an interesting subject. Good luck, Don W -- who is still scratching his head about what to do about lightning protection for his Irwin 38. |
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. |
Emergency lightning protection
Charlie Morgan wrote: Honestly? There is absolutely nothing you can do to a 30 or 40 foot boat to protect it in the slightest. It may make you feel better, but there's truly no way you are going to harness and direct a lightning strike that hits your mast. Lightning will vaporize (literally) your battery cables. POOF! A keel stepped mast with large solid aluminum bar ties to the non-encapsulated lead keel is about as good as it gets. It's also supposedly a good idea to ground your chainplates with large wire down to the keel. What is controversial is whether the good grounding scheme actually increases your chances of taking a strike. The ABYC has standards for lightning protection for sailboats IIRC. The only thing that MAY help you is to always anchor with boats that have much taller masts than yours. This is controversial also, as its not always the tallest point that gets struck. Don W. |
Emergency lightning protection
Wayne.B wrote:
How about a heavy wire connecting keel bolts to mast bolts, less than a foot apart in my bilge? That's about as good as it gets, better to use heavy copper braid however. That also makes an excellent ground for your SSB radio. You do not want your boat ground or RF ground connected to your lightning ground unless you wish to replace all of your electronics in the event of a strike. The reason is that when the strike hits, the ground will temporarily pulse to a much higher voltage than the battery output, reversing the power inputs and blowing your electronic equipment. That is not to say that your electronic equipment will survive if the grounds are not connected, but you'll certainly stand a better chance. Don W. |
Emergency lightning protection
On Thu, 15 Mar 2007 23:22:43 -0500, Don W
wrote: 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 Roger, If lightning hits your mast, your battery cables and chains are not going to help much, although they probably won't hurt either. I've got the electrical engineering degree with a bunch of experience to back it up, but lightning protection is a specialized black art--even in my field. There are some pretty good explanations on the web by PHd's who have made lightning protection their whole career. Search them out and give them a read. It's an interesting subject. Good luck, Don W -- who is still scratching his head about what to do about lightning protection for his Irwin 38. FWIW, I took a hit from lightning whilast at anchor in Langkawi, Malaysia. My 42 footer is strip planked and sheathed with GRP. The path of the lightning which melted the VHF atnenna and tricolour at the masthead was down the twin backstays. Both the large ceramic insulators on the one used as an aerial blew to pieces. Later, we recorded a smell of antifouling. It appears that one backstay (not the aerial one) internal chainplate bolt was touching a large tin of antifouling as well as one of the bolts for the drop down ss ladder which was in the water. A small hole was blown in the side of the can. Every connected electronic item and all instruments were blown. The computers were fine. Now I am deminically paranoid about lightning. I race around and pull out all plugs, wires, aerials and power cables. It was a real pain with the 13 to the Raytheon autopilot but I fed all to a single plug which goes back like a breeze. Yes, I've heard of electromagnetic induction. I throw everything that fits into my stainless oven. It feels good to be sailing along with just the compass but have learned to take note of the heading first. Did secure a large cable and chain to one capshroud but the bumping along the hull was too annoying. I like the idea of traing one from a backstay however. Seem to recall hearing somewhere that chain is not good as a conductor. - any ideas please. It is rather scary being the tallest thing for miles of ocean when you see lightning ahead. This thread is of intense interest. cheers Peter Hendra |
Emergency lightning protection
It sounds like I was on the right track,
How important is a really low resistance connection? I have a spinnaker track and fitting at about the right height. Is a special fitting really necessary at these high voltages or would a large snap shackle in the ring do with the cable passed around the mast a couple times first? (Insulation removed over the last couple feet). Similar question about chain which would be much easier to stow than a big sheet of copper. Lots of surface area and, with salt water helping to carry current from link to link is seems like it would work. Wouldn't the solder on the copper sheet vaporize in the first milisecond? It sounds like nothing is going to do anything but tip the odds slightly in your favor. I don't have a big investment in electronices. My only aim is to be alive in something floating after a strike, even with major damage. -- Roger Long |
Emergency lightning protection
On Fri, 16 Mar 2007 23:06:00 -0400, Wayne.B
wrote: On Fri, 16 Mar 2007 22:22:25 +1100, Peter Hendra wrote: It is rather scary being the tallest thing for miles of ocean when you see lightning ahead. You bet. Lightning is fickle however. We were halfway to Bermuda once, over 300 miles offshore when we got hit with a ferocious thunder squall. The boat was a perfect target, all aluminum hull with an 85 ft mast. Lightning chose to hit a wavetop about 100 yards away instead of us. We still lost all of the electronics except my pocket GPS, just from induced currents. The pocket GPS was an early model and hasn't worked in years now, but I still keep it around for sentimental reasons. :-) As it is so fickle, I've often thought of sacrificing a chicken to Poseidon. Once, not having a real live chicken, I threw a tin of chicken spam overboard. It was rusty and looked unsafe for us to eat but the God didn't appear to notice it as the lightning didn't touch us. Anyone know what Poseidon prefers? |
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 |
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. |
Emergency lightning protection
On Mar 16, 12:52 pm, "Frogwatch" wrote:
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. I believe that my battery cable will survive. Consider that lightning rod cables survive multiple hits. There is considerable disagreement over lightning protection especially over whether you can prevent a strike by using pointy conductors atop a structure. However, there is agreement on protecting yourself when you are hit and that is to get the strike to ground via a straight stranded cable. I take an agnostic approach to the "pointy thing atop the mast dissipating excess charge" and think that if it works that my Windex will suffice. BTW, if you have a carbon fiber mast and do not have a cable running up the mast, you WILL lose the mast when struck. It has just enough conductivity to conduct below the surface a bit and the heat in the fibers destroys it. A friend of mine in a 21' sailboat hit an overhead HT powerline. It destroyed the mast leaving a very amazing melt pattern raining the deck with molten Aluminum. Another interesting thing is what happens to different trees that are struck. Many trees survive being struck but not pines. |
Emergency lightning protection
On Fri, 16 Mar 2007 22:22:25 +1100, Peter Hendra
wrote: It is rather scary being the tallest thing for miles of ocean when you see lightning ahead. You bet. Lightning is fickle however. We were halfway to Bermuda once, over 300 miles offshore when we got hit with a ferocious thunder squall. The boat was a perfect target, all aluminum hull with an 85 ft mast. Lightning chose to hit a wavetop about 100 yards away instead of us. We still lost all of the electronics except my pocket GPS, just from induced currents. The pocket GPS was an early model and hasn't worked in years now, but I still keep it around for sentimental reasons. :-) |
Emergency lightning protection
On Mar 15, 2:34 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 Most lightning protection systems are designed to ground your mast (or lightning rod, on houses) to earth with a minimum resistance. The theory is that by "equalizing" the potential of the mast with the sea (or ground for houses) the lightning won't "see" the mast (or lighting rod) as the lowest potential path to ground. Sounds like black magic, and they always use heavy cables to ground the lightning rods, so if you should get struck, it won't vaporize. Sometimes the lightning strike has multiple paths to ground, so you don't always get the full effect. Sometimes, you only get struck a little bit (a near miss) so the total power through your ground path is relatively small. |
Emergency lightning protection
Nearly 60 years ago I started work with a shipping company, to train to
become an electrical engineer. A few years later, after one of the companies ships had a topmast destroyed by lightning (the topmasts were usually wood in those days as it was easier to make a tapered spar this way and appearance still important), the company decided that all the ships wooden topmasts should be protected by lightning conductors, and in a shop where the youngest tech was in his 50s, I got the job. Every ship that arrived in Sydney had it's topmast inspected, and if not conductored I would be assigned to go up the mast, measure up for a conductor, make it, then up the mast again to fit it. Unable to reach past the top of the mast in a bosuns chair I designed the rod be the top part of the conductor fastened below the truck but projecting above it. Usually the conductor consisted of a 1" x 1/4" copper strip, cut at a 60 deg angle at the top (to give a sharp, lightning attracting, point), joggled to go out around the truck and drilled every 2ft or so to be screwed to the topmast, with a hole at the bottom to be bolted to the lower steel section of mast. One mast had a yard about 3' below the top and after being hauled as hi as possible in the bosuns chair, curious because there appeared to be a conductor already on the topmast, I climbed out of the chair by reaching up and grasping the truck, stood on the yard and tied a rope around my waist and the mast. Hi and secure I was able to look down on the top of the truck and saw that there had indeed been a lightning rod fitted previously consisting of a piece of 1" rod that when screwed into a brass insert in the top of the truck made contact with the conductor which went across the top of the spar, beneath the truck. Back in the workshop I rounded up a 12 in length of copper rod and machined a thread to fit the brass plate with a nice sharp lightening attracting point on the top end. Back to the ship, hoisted to the top of the mast, I again grasped the truck, climbed onto the yard and secured myself to the mast with a rope. I screwed the new lighting rod into the truck and kept screwing so that the rod would make firm contact with the conductor. I kept screwing and screwing waiting for the connection to become firm, until finally the whole truck came away in my hands and in shock I dropped it, fortunately not on my halyard tenderers waiting some 60 ft below. My blood ran cold. I had been using this truck as a hand-hold to hoist myself out of the bosuns chair onto the yard. Yet the force of gravity on its weight and a bead of paint around the junction with the topmast were all that held it in place. This was the closest I ever came to being killed by a bolt of lightning, a bolt that occurred several months before, some thousands of miles away in mid Pacific. Remembered from the same period. A mate and I, just as we arrive in the yacht club car park, were pounced on by a storm. We waited in the "Faraday cage" safety of the car till the first fury had abated, then made a break and dinghied out to the boat we were to spend the night on. Worried about the boat being struck by lightning, which looked like coming back, we connected a large shackle on a short piece of wire to the rig and threw it into the water. Now "safe as houses", we turned in to be ready for our early departure in the morning. Of course the next morning we found that the piece of wire had been too short and had the shackle suspended uselessly a foot above the water. Another experience I remember. A mate who had a 26 ft keelboat on an inland lake, new to sailing, was fascinated with the idea of sailing at night. Knowing that I had done a god bit of night racing asked me if I would organise a night sail for him. I picked out a full moon night (the lake was formed by a dam and there were plenty of trees growing out of the water), got hold of another couple of experienced mates and off we set. We'd gone about 6 miles across the dam when a storm obscured the sky, and lightning flashed. We turned back, stationing one hand in the pulpit too keep a look out for trees, fingers crossed. The wind piped up as it does with a storm and we were soon having an exciting sail, rail down, in the dark, when one of the crew (a mechanical engineer) noticed that there were sparks cracking between the boom and the mast. Fascinated by this he tried to interest the man in the pulpit (a mining engineer) who "did not want to know anything about it", while the man on the tiller (electrical engineer) made sure he kept well away from the lifelines and other metal. The owner, an intrepid soul, wide eyed with the excitement of it all, and thoroughly enjoying his night sail. We made it back to the mooring without damage. Another example. Some 5 years ago an almost septuagenarian couple were caught in, their now power cruiser, in a storm while researching the island we now live on. We had anchored in a spot where we were sure there was a good bottom and sat on the bridge to watch the storm. We had wind and rain and lightning, as you do, and I remember suggesting to my wife that maybe I should get some soap and clean the outside of the clears relying on the rain to rinse them. She demurred, on the grounds that it would be too dangerous, after all we were protected from the lightening by our cloth bimini top and clears, so I waited till the first squall passed and then washed the outside of the clears and the next (worse) lot of rain wind and lightening rinsed them clean. It was a bit like when you were a kid, in bed, and worried about monsters, you pulled the blanket over for protection. It worked for me; none of the monsters got me. How about carrying a blanket. Maybe even a Teddy as well. To be serious, I do not believe that there is a definitive answer to the task of protecting a yacht from lightening unless it's made of steel. In Australia anyway, the main thing is to not play golf, as this is where the statistics say you are most likely to be killed by lightening, even worse than shark attack. |
Emergency lightning protection
On Sat, 17 Mar 2007 06:17:03 GMT, "barry lawson"
wrote: In Australia anyway, the main thing is to not play golf, as this is where the statistics say you are most likely to be killed by lightening, even worse than shark attack. Same thing here in south Florida. We usually have several fatal golf course incidents every year. So golfing is bad, good thing since my game is terrible anyway. Regarding the boat, a well grounded mast, shrouds and stays seems to be the consensus and jibes with my experience. If caught out, staying away from metalic objects as much as possible seems prudent. That said, I had a friend who was on a fully crewed 35 footer that was struck twice in one weekend. All of the electronics were toast but no one was injured at all, and there was no damage to the hull. Every once in a while you hear about someone with a plastic thru hull transducer getting blown out by lightning. |
Emergency lightning protection
Wayne.B wrote:
I had a friend who was on a fully crewed 35 footer that was struck twice in one weekend. All of the electronics were toast but no one was injured at all, and there was no damage to the hull. Do you know how it was equipped (or not) for lightening protection? Rick |
Emergency lightning protection
On Mar 17, 10:42 am, wrote:
Wayne.B wrote: I had a friend who was on a fully crewed 35 footer that was struck twice in one weekend. All of the electronics were toast but no one was injured at all, and there was no damage to the hull. Do you know how it was equipped (or not) for lightening protection? Rick Golf is Florida Nature's way to get rid of excess tourists. |
Emergency lightning protection
On Sat, 17 Mar 2007 09:42:45 -0500, lid wrote:
Do you know how it was equipped (or not) for lightening protection? ============================= Don't know. |
Emergency lightning protection
"Roger Long" wrote...
Like the vast majority of fiberglass boat owners, I'm sailing around in a boat with next to no lightning protection.... Related question - I am building an open 20' power boat, of all-aluminum construction. It will be used in all weather conditions, sometimes for "time-critical" trips. I have toyed with the idea of shipping a short mast (boathook?) to disperse any electrical charge, and hopefully channel any direct strikes along a known path. Any thoughts? Sal's Dad |
Emergency lightning protection
"Sal's Dad" wrote in message ... "Roger Long" wrote... Like the vast majority of fiberglass boat owners, I'm sailing around in a boat with next to no lightning protection.... Related question - I am building an open 20' power boat, of all-aluminum construction. It will be used in all weather conditions, sometimes for "time-critical" trips. I have toyed with the idea of shipping a short mast (boathook?) to disperse any electrical charge, and hopefully channel any direct strikes along a known path. Any thoughts? Sal's Dad Yes, it's a dumb idea. What you have there is a Faraday cage. If you get caught in a lightning storm sit or lie down in the center of the boat so your head is below the gunnels and you will be protected by the Faraday cage. Erecting a mast will only attract a lightning strike. http://en.wikipedia.org/wiki/Faraday_cage Wilbur Hubbard |
Emergency lightning protection
Wayne.B wrote:
On Sat, 17 Mar 2007 06:17:03 GMT, "barry lawson" wrote: In Australia anyway, the main thing is to not play golf, as this is where the statistics say you are most likely to be killed by lightening, even worse than shark attack. Same thing here in south Florida. We usually have several fatal golf course incidents every year. So golfing is bad, good thing since my game is terrible anyway. Regarding the boat, a well grounded mast, shrouds and stays seems to be the consensus and jibes with my experience. If caught out, staying away from metalic objects as much as possible seems prudent. Err, metal like on my boat, the metal column and wheel of the helm? Yikes!!! Stephen |
Emergency lightning protection
"Sal's Dad" wrote Any thoughts? Make it a tall mast with a sharp point on top. There are also some special electrodes that are supposed to be better than a sharp point but I have no idea how valid their claims are. -- Roger Long |
Emergency lightning protection
"Roger Long" wrote in message ... "Sal's Dad" wrote Any thoughts? Make it a tall mast with a sharp point on top. There are also some special electrodes that are supposed to be better than a sharp point but I have no idea how valid their claims are. Better yet, fly a kite made out of aluminum foil and use a wire leader! Are you trying to get the man killed? Wilbur Hubbard |
Emergency lightning protection
Any thoughts?
Make it a tall mast with a sharp point on top. There are also some special electrodes that are supposed to be better than a sharp point but I have no idea how valid their claims are. Better yet, fly a kite made out of aluminum foil and use a wire leader! Are you trying to get the man killed? I was thinking along the lines of the "cone of protection" approach: http://www.mdsg.umd.edu/CB/lightning.html http://www.cdc.gov/nasd/docs/d000001...7/d000007.html http://www.cgauxa.org/beacon/Summer06BEACON.pdf or a Faraday Cage created from the framework of a bimini or dodger. Or maybe a combination of both? Sal's Dad |
Emergency lightning protection
"Sal's Dad" wrote I was thinking along the lines of the "cone of protection" approach: or a Faraday Cage created from the framework of a bimini or dodger. Exactly. I don't know if the accusation of trying to get you killed was directed at me but the boathook originally referred to, doesn't produce much of a cone unless it is an unusually long one. Headstays, backstays, and shrouds outght to produce something of a Faraday Cage effect on a metal boat. -- Roger Long |
Emergency lightning protection
"barry lawson" wrote in news:zJLKh.12288
: we were protected from the lightening by our cloth bimini top Fantastic stories! Thank you! I was on watch during a very violent thunderstorm while out on Charleston (SC, USA) Harbor on a Saturday afternoon. Cap'n Geoffrey had guests aboard the Endeavour 35 who were not sailors, so I suggested, instead of everyone getting drenched to the bone, that he take his guests down into the cabin and I'd handle the helm until it stopped. I put her on a nice tack in not-too-much wind (in spite of the storm), and was soon racing against a Catalina 27 in the storm headed in the same direction. Drowned to the bone by the deluge and having a ball, I soon felt the hackles on my neck start tickling for no reason. I was leaning back against the ungrounded backstay, without thinking about it, and holding THE OCEAN in my hands, the metal wheel firmly attached by stainless cables to the big aluminum rudder underwater! St Elmo's fire was creeping up my arm to discharge that rigging. I decided this was NOT the path to glory it said in the books, so moved away from the backstay to stand on the upwind side of the wheel, steering it from its side a little forward of the pedestal. There were two POPS that jumped, one after the other, from the backstay to the wheel in my hands about 5-10 minutes after I moved! It wasn't a lightning hit, it was static discharging the rigging to that overhead black cloud. It looked like the thin discharge from a Van Degraff static generator back in high school physics class. They didn't hear it in the cabin. I've often wondered how close we were to a major strike to the ungrounded mainmast that lead down to the step in the bilge. Cap'n Geoffrey popped his head up opening the hatch to see if I needed anything a few minutes after. I didn't say anything, but I needed a change of pants....hee hee. Larry -- Roll up to the long checkout line.... Yell, "ICE RAID!" It's your turn to load the grocery belt...(c; |
Emergency lightning protection
Wayne.B wrote in
: Every once in a while you hear about someone with a plastic thru hull transducer getting blown out by lightning. http://edis.ifas.ufl.edu/SG071 Great webpage. The professor of EE is also a sailor. Enter: Sailboat lightning grounding into the Google search engine. There's lots of pages so you can do it right. NEVER MAKE A NEAT RIGHT ANGLE TURN ON A LIGHTNING GROUND! If you gotta be "pretty", don't bother with it at all. ALL turns in ALL lightning grounds MUST be made gradually over a large diameter, not those "nautical" perfect looking turns the bilge pump wires have. This reduceds series INDUCTANCE. Series inductance on the very-fast pulse of a lightning hit is what destroys it.... http://www.copper.org/applications/e...kgbi_station_A 6082.html http://www.space.com/businesstechnol...ket_lightning_ 030130.html Very interesting.....Xrays! Larry -- Roll up to the long checkout line.... Yell, "ICE RAID!" It's your turn to load the grocery belt...(c; |
Emergency lightning protection
Here's my list of lightning protection links. Probably more than you
ever wanted to know. I have a lightning rod on my mast, connected with a large cable to a copper plate that I drop overboard when not underway. Nothing will guarantee protection, but it's better than nothing. At least it makes me feel better! :-) http://www.kastenmarine.com/Lightning.htm http://marinelightning.com/ http://www.thomson.ece.ufl.edu/lightning/ http://www.cdc.gov/nasd/docs/d000001...7/d000007.html http://www.lightningsafety.com/ http://www.lightningsafety.com/nlsi_...od_recent.html - specific info. on lightning rods http://powerquality.com/ar/power_pre...tning_strikes/ http://www.lightningmaster.com/Structural.htm |
| All times are GMT +1. The time now is 04:16 AM. |
Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
Copyright ©2004 - 2014 BoatBanter.com