Mark: The piece you wrote on lightning was very informative. How effective are these charge-shedding brush devices that are currently on the market? From what I recall from college physics, they should be very effective at dissipating charges, which is what the manufacturer is claiming. I just wondered if you had an opinion. I live in central Florida, where severe lightning is a daily occurrence (easy to see that I have a vested interest in your opinion!!). Thanks, Peter Suah "Raven"
Lightning question for Mark Kissel
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Mark Kissel
An excellent question!
Peter, There are several charge dissipators on the market; most look like bottle brushes or toilet brushes. They are usually made of stainless or brass/bronze. The idea is that these devices will "bleed" charges into the atmosphere thereby keeping any large potential difference from accumulating on your boat. Some even claim to be able to "retard" the formation of streamers. Streamers are the organized upward "flow" of ions from objects as a charged cloud passes over. A stepped leader begins at the cloud and starts downward. As it approaches the ground, the streamers rise to meet it. When one does, lightning occurs. How effective are they? I recently investigated a lightning strike to a 200 ft microwave tower. This tower had dissipators located every 20 ft all the way to the top and staggered on the three corners of the tower members. They certainly didn't prevent the strike from hitting the tower. Proximity is a great factor. In this case, the tower is the tallest object for several miles around. How do I feel about them? If two identical boats were anchored 50 yards apart and one was equipped with static dissipators, I'd give that boat only a slightly better than 50% chance of not being struck. If it happens to be the only boat on the water for miles around, I'd have to say that the odds go up significantly. Incidentally, central Florida has the highest number of strikes annually and has been dubbed "lightning alley". I'll keep my fingers crossed for you (but not over my head). Mark Kissel s/v Kittiwake H240
Peter, There are several charge dissipators on the market; most look like bottle brushes or toilet brushes. They are usually made of stainless or brass/bronze. The idea is that these devices will "bleed" charges into the atmosphere thereby keeping any large potential difference from accumulating on your boat. Some even claim to be able to "retard" the formation of streamers. Streamers are the organized upward "flow" of ions from objects as a charged cloud passes over. A stepped leader begins at the cloud and starts downward. As it approaches the ground, the streamers rise to meet it. When one does, lightning occurs. How effective are they? I recently investigated a lightning strike to a 200 ft microwave tower. This tower had dissipators located every 20 ft all the way to the top and staggered on the three corners of the tower members. They certainly didn't prevent the strike from hitting the tower. Proximity is a great factor. In this case, the tower is the tallest object for several miles around. How do I feel about them? If two identical boats were anchored 50 yards apart and one was equipped with static dissipators, I'd give that boat only a slightly better than 50% chance of not being struck. If it happens to be the only boat on the water for miles around, I'd have to say that the odds go up significantly. Incidentally, central Florida has the highest number of strikes annually and has been dubbed "lightning alley". I'll keep my fingers crossed for you (but not over my head). Mark Kissel s/v Kittiwake H240
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Chris
How dangerous is it?
I've been worried about lightnening strikes for a while. First, it seems that if you are on a sailboat alone on a bay during a thunderstorm, your chances of getting hit are about 100%. Am I wrong? You are well grounded and at 30-40' are the tallest object for miles. What is there to keep you from getting hit? Second, what happens when you DO get hit? I've heard things like burned holes in the hull, all electronics fried (wheather plugged in or not), fire aboard etc. Is it really THIS bad? Is there anything that can be done to lessen the effects of the strike? I've been told that as much current as passes through, you have to have a really big copper conductor to do any good. Rigging wires, being stainless (poor conductor) are not enough to make much difference...... It just seems that being out in a thundersorm would be a sure way to fry your boat, but many people seem not to get damaged or hit....... Thanks! Chris
I've been worried about lightnening strikes for a while. First, it seems that if you are on a sailboat alone on a bay during a thunderstorm, your chances of getting hit are about 100%. Am I wrong? You are well grounded and at 30-40' are the tallest object for miles. What is there to keep you from getting hit? Second, what happens when you DO get hit? I've heard things like burned holes in the hull, all electronics fried (wheather plugged in or not), fire aboard etc. Is it really THIS bad? Is there anything that can be done to lessen the effects of the strike? I've been told that as much current as passes through, you have to have a really big copper conductor to do any good. Rigging wires, being stainless (poor conductor) are not enough to make much difference...... It just seems that being out in a thundersorm would be a sure way to fry your boat, but many people seem not to get damaged or hit....... Thanks! Chris
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R. Palaia
Cone of Protection
I learned this in my USPS "Seamanship" class. If your stays and shrouds are properly grounded, there is a cone of about 60 degrees with the vertical (from the tip of your mast) and a circle of protection at the water line of about 1.5 to 2 times the height of the mast. If your boat is totally within this cone, it is protected from at least 99 percent of possible strikes!! I think the key here however is "properly grounded mast and stays". Roc
I learned this in my USPS "Seamanship" class. If your stays and shrouds are properly grounded, there is a cone of about 60 degrees with the vertical (from the tip of your mast) and a circle of protection at the water line of about 1.5 to 2 times the height of the mast. If your boat is totally within this cone, it is protected from at least 99 percent of possible strikes!! I think the key here however is "properly grounded mast and stays". Roc
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Michael Bell
Far fetched?
On our cruise this summer, someone had brought one of the battery jumper cables from their truck. At the onset of a thunder storm – he clamped the jumper cable to the mast base, and threw the other end overboard. His thinking was that it would conduct the strike from the mast to the water. Any response to this idea would be appreciated.
On our cruise this summer, someone had brought one of the battery jumper cables from their truck. At the onset of a thunder storm – he clamped the jumper cable to the mast base, and threw the other end overboard. His thinking was that it would conduct the strike from the mast to the water. Any response to this idea would be appreciated.
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Tom
Plastic keels
Mark I agree. Very good post. But what about those of us with plastic keels (H26 swing keel)? Is there any way to improve the odds or minimize the damage on a boat with nothing to ground to? Tom/Texas
Mark I agree. Very good post. But what about those of us with plastic keels (H26 swing keel)? Is there any way to improve the odds or minimize the damage on a boat with nothing to ground to? Tom/Texas
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Dave Condon
Grounding
On the 23.5, 240, 26 and 260, you will find in one form or another that the mast and shrouds are grounded via the metal bracket that is used to hold the centerboard in place which protrudes into the water. There is so much discussion on this issue but from the posts, it would appear that no one has been injured. The boat that I just repaired due to damage from lightning, there were four people sailing and no one was hurt. If a storm does come up, head in to the dock or a safe anchorage time permitting. Otherwise, drop your sails and do not much metal. I have been caught in a fierce thunderstorm at night myself and followed the above. Everyone has an opinion which I am sharing based on experience
On the 23.5, 240, 26 and 260, you will find in one form or another that the mast and shrouds are grounded via the metal bracket that is used to hold the centerboard in place which protrudes into the water. There is so much discussion on this issue but from the posts, it would appear that no one has been injured. The boat that I just repaired due to damage from lightning, there were four people sailing and no one was hurt. If a storm does come up, head in to the dock or a safe anchorage time permitting. Otherwise, drop your sails and do not much metal. I have been caught in a fierce thunderstorm at night myself and followed the above. Everyone has an opinion which I am sharing based on experience
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Mark Kissel
Some answers.
Chris, It may seem intuitive that the odds of being struck rise to 100% if you are the only boat on the bay but that's not really the case. To understand why, we need to know something about why lightning occurs at all. I'm sure you've shuffled your feet across a carpet, touched a metal object, and saw/felt static electricity. Shuffling your feet creates charge transfer. The "spark" jumps to your finger before you actually touch the object. Lightning is just static electricity albeit of a much greater magnitude. Ice crystals in a cloud bang into each other creating charge transfer. As the charge accumulates, it is separated within the cloud. Now we have a situation analogous to you shuffling your feet on the carpet. When the cloud passes over an object on the ground, it "sees" a difference in its charge versus that of an object on the ground (potential difference). Now two scenarios can occur. The potential difference may be great enough that the air can no longer act as an insulator and a stepped leader begins to form. At the same time, streamers begin to rise upward to meet the stepped leader. When the two meet, lightning occurs. The second scenario is just like the first but in this case, the object on the ground is much taller than the surrounding terrain. This reduces the physical distance between them making it easier for the leader and streamer to meet. Hence, tall radio/tv towers are struck repeatedly. So why doesn't the only boat on the bay get struck every time a storm passes? It has everything to do with the potential difference. Your boat may not have enough charge build-up to cause a large potential difference. Think about this for a moment, if your mast is grounded, the tip of your mast has approximately the same charge as the water around your boat. Thus, your mast is at nearly the same potential difference as the water relative to a passing thundercloud. The cloud "sees" no more "reason" to strike your boat than the surrounding water. Even if your mast is not grounded, there still may not be enough potential difference to initiate the strike. The second factor is that your mast height may be insignificant compared to the distance from the cloud to the ground. You wouldn't get shocked from standing with your finger pointed at the door knob from three feet away. The air is providing enough insulation to prevent the potential difference from becoming great enough for a discharge. Whew! I hope this answers your first question. For your second question, there are a number of people on this web site that claim to have had their boats struck by lightning. Direct strikes will certainly cause damage to electronics from inductive coupling if not from direct conduction. Many have reported significant hull damage as well. Do not think that stainless is a poor conductor. It may not conduct as well as copper but that would be a moot point in the case of a lightning strike. Mark Kissel s/v Kittiwake H240
Chris, It may seem intuitive that the odds of being struck rise to 100% if you are the only boat on the bay but that's not really the case. To understand why, we need to know something about why lightning occurs at all. I'm sure you've shuffled your feet across a carpet, touched a metal object, and saw/felt static electricity. Shuffling your feet creates charge transfer. The "spark" jumps to your finger before you actually touch the object. Lightning is just static electricity albeit of a much greater magnitude. Ice crystals in a cloud bang into each other creating charge transfer. As the charge accumulates, it is separated within the cloud. Now we have a situation analogous to you shuffling your feet on the carpet. When the cloud passes over an object on the ground, it "sees" a difference in its charge versus that of an object on the ground (potential difference). Now two scenarios can occur. The potential difference may be great enough that the air can no longer act as an insulator and a stepped leader begins to form. At the same time, streamers begin to rise upward to meet the stepped leader. When the two meet, lightning occurs. The second scenario is just like the first but in this case, the object on the ground is much taller than the surrounding terrain. This reduces the physical distance between them making it easier for the leader and streamer to meet. Hence, tall radio/tv towers are struck repeatedly. So why doesn't the only boat on the bay get struck every time a storm passes? It has everything to do with the potential difference. Your boat may not have enough charge build-up to cause a large potential difference. Think about this for a moment, if your mast is grounded, the tip of your mast has approximately the same charge as the water around your boat. Thus, your mast is at nearly the same potential difference as the water relative to a passing thundercloud. The cloud "sees" no more "reason" to strike your boat than the surrounding water. Even if your mast is not grounded, there still may not be enough potential difference to initiate the strike. The second factor is that your mast height may be insignificant compared to the distance from the cloud to the ground. You wouldn't get shocked from standing with your finger pointed at the door knob from three feet away. The air is providing enough insulation to prevent the potential difference from becoming great enough for a discharge. Whew! I hope this answers your first question. For your second question, there are a number of people on this web site that claim to have had their boats struck by lightning. Direct strikes will certainly cause damage to electronics from inductive coupling if not from direct conduction. Many have reported significant hull damage as well. Do not think that stainless is a poor conductor. It may not conduct as well as copper but that would be a moot point in the case of a lightning strike. Mark Kissel s/v Kittiwake H240
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Mark Kissel
And a few more answers.
Roc, The real key is that natural lightning tends to be significantly random. If I hoisted a rubberband to the top of the mast and was never struck by lightning, even though I was in some vicious storms, I might be tempted to claim that it was a great deterrent. **************** Michael, Lightning WILL find its way to the water, jumper cable or not. It may help by providing another path. **************** Tom, Hopefully I answered your question in my reply to Chris. And as Dave mentioned, there is some grounding provided by Hunter. **************** Dave, Good advice! If you can avoid a storm, that is the best prevention. Sort of like not playing in the highway if you don't want to be run over. **************** I quite often hear people comment, "lightning does strange things." I agree that lightning often defies our simple logic however, it still follows the laws of physics. Period. Mark Kissel s/v Kittiwake H240
Roc, The real key is that natural lightning tends to be significantly random. If I hoisted a rubberband to the top of the mast and was never struck by lightning, even though I was in some vicious storms, I might be tempted to claim that it was a great deterrent. **************** Michael, Lightning WILL find its way to the water, jumper cable or not. It may help by providing another path. **************** Tom, Hopefully I answered your question in my reply to Chris. And as Dave mentioned, there is some grounding provided by Hunter. **************** Dave, Good advice! If you can avoid a storm, that is the best prevention. Sort of like not playing in the highway if you don't want to be run over. **************** I quite often hear people comment, "lightning does strange things." I agree that lightning often defies our simple logic however, it still follows the laws of physics. Period. Mark Kissel s/v Kittiwake H240
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Michael Bell
Thanks Mark.
After spending 4 hours cowering in the cabin – I think I’ll look for a place to stow the jumper cable for next summer.
After spending 4 hours cowering in the cabin – I think I’ll look for a place to stow the jumper cable for next summer.
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Ron M
Doubt jumper will work
I have a hard time imagining that the jumper cable hanging in the water will be helpful. My experience with lightning was learned selling radio towers. If you are trying to provide a safe path for the lightning to get to ground (or should I say water), it needs to be heavy duty and have as little bending in the path as possible. Bends need to be smooth, no hard angles. If lightning hits your mast, it could start coming down through many different paths (mast, stays, shrouds). The jumper will be connected to only one place and will most likely have a poor contact surface and create hard bends. Now, if it helps with disipating charge, and thus avoiding the strike to start with...that's a different story. Happy Sailing - Ron M
I have a hard time imagining that the jumper cable hanging in the water will be helpful. My experience with lightning was learned selling radio towers. If you are trying to provide a safe path for the lightning to get to ground (or should I say water), it needs to be heavy duty and have as little bending in the path as possible. Bends need to be smooth, no hard angles. If lightning hits your mast, it could start coming down through many different paths (mast, stays, shrouds). The jumper will be connected to only one place and will most likely have a poor contact surface and create hard bends. Now, if it helps with disipating charge, and thus avoiding the strike to start with...that's a different story. Happy Sailing - Ron M
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