Fanie
10-28-2007, 02:29 PM
Is lightning a big risk on masts during storms ?
View Full Version : Lightning on masts
lazeyjack
10-28-2007, 02:38 PM
yes and no, I was struck over and over in our steel yacht in Fiji, all it did was knock out our ssb, via the backstay
It is a real risk even in boats with grounded mast, because if the high voltage, it can neevr be relied upon to take a certain track, I mean you can not expect a million volts to track down a 6mm wire, so often the lightening will blow out meatal seacocks and the like, CertainLY GROUNDING THE MAST TO KEEL BOLTS DOES HELP, but really you can not control the path it may take
All in all, many boats come away with the men in them alive after lightening strike, albeit lacking a lot of expensive equipement
I will say this, it is very scary and bloody noisy
It is a real risk even in boats with grounded mast, because if the high voltage, it can neevr be relied upon to take a certain track, I mean you can not expect a million volts to track down a 6mm wire, so often the lightening will blow out meatal seacocks and the like, CertainLY GROUNDING THE MAST TO KEEL BOLTS DOES HELP, but really you can not control the path it may take
All in all, many boats come away with the men in them alive after lightening strike, albeit lacking a lot of expensive equipement
I will say this, it is very scary and bloody noisy
Fanie
10-28-2007, 02:46 PM
Certainly the steel boat provided a shied around you. How about if it's a fibre glass boat. If a mast is through-cabin, can or will it be life threatening ?
ted655
10-28-2007, 07:20 PM
Here are some things to know that might help in making decisions.
Lightning is always in a hurry, it doesn't like to make sharp turns.
It prefers a surface path, pipe is a much better conductor than wire, other things being equal.
It will jump, it's always seeking a faster path or "paths" to ground.
The height of the initial contact is not always the tallest structure, but rather the better path.
Lightning is always in a hurry, it doesn't like to make sharp turns.
It prefers a surface path, pipe is a much better conductor than wire, other things being equal.
It will jump, it's always seeking a faster path or "paths" to ground.
The height of the initial contact is not always the tallest structure, but rather the better path.
Ike
10-28-2007, 09:55 PM
If you go to menu at the top of the page and use the search function, searching on lightning you will find that this has been discussed many time. Here's the most recnt thread http://boatdesign.net/forums/showthread.php?t=19662&highlight=lightning
Fanie
10-29-2007, 03:27 AM
Ok, I've read the posts made that Ike suggested, thanks. I still don't have an answer, is lightning on a boat with a metal mast life threatening, or are there no-one alive to tell about it :D
Wrt the electronics that gets damaged. Even if plugged out it can get damaged by EMP. Such an electro magnetic pulse can be very large. Equipment with metal shielding inside would have a better chance to survive than if enclosed only in plastic.
If you place electronic equipment inside a lightweight metal enclosure you should get about zero lightning damages, unless maybe in a direct strike. The CSIR once showed how safe automobiles are, lightning travels outside the body, never in, so the occupants are safe. Same for equipment.
The real reason plugged-in electronics get damaged is a simple matter of ohms law - if a radio is connected to the mast antenna, and even grounded really well to the mast, the radio gets damaged purely using ohm's law.
The low ohm value of the mast, conducting many thousands of amps works out to a huge huge voltage drop that is frying the equipment. It is this immense current from the lightning bolt that generates an electro magnetic field (EMP) that buggers the equipment up.
The best metal to use would be 'mu-metal', you find it in hard drives and floppy drives to shield the magnetic fields from the supermagnets to the magnetic media they use in them - otherwise the saved data on a drive will get erased faster than you can write it.
While still magnetic, this metal prevents magnetic fields to pass through the metal. If you place a magnet on one side nothing will be attracted on the other side. The same with other metals is not true to a more or lesser degree.
You don't need a direct lightning hit to lose equipment from EMP. The world's biggest fear should be if a meteor enters the atmosphere and create a large enough EMP to destroy all electronics. Everything would come to a screetching halt. Ok, maybe not all boats... ;)
Wrt the electronics that gets damaged. Even if plugged out it can get damaged by EMP. Such an electro magnetic pulse can be very large. Equipment with metal shielding inside would have a better chance to survive than if enclosed only in plastic.
If you place electronic equipment inside a lightweight metal enclosure you should get about zero lightning damages, unless maybe in a direct strike. The CSIR once showed how safe automobiles are, lightning travels outside the body, never in, so the occupants are safe. Same for equipment.
The real reason plugged-in electronics get damaged is a simple matter of ohms law - if a radio is connected to the mast antenna, and even grounded really well to the mast, the radio gets damaged purely using ohm's law.
The low ohm value of the mast, conducting many thousands of amps works out to a huge huge voltage drop that is frying the equipment. It is this immense current from the lightning bolt that generates an electro magnetic field (EMP) that buggers the equipment up.
The best metal to use would be 'mu-metal', you find it in hard drives and floppy drives to shield the magnetic fields from the supermagnets to the magnetic media they use in them - otherwise the saved data on a drive will get erased faster than you can write it.
While still magnetic, this metal prevents magnetic fields to pass through the metal. If you place a magnet on one side nothing will be attracted on the other side. The same with other metals is not true to a more or lesser degree.
You don't need a direct lightning hit to lose equipment from EMP. The world's biggest fear should be if a meteor enters the atmosphere and create a large enough EMP to destroy all electronics. Everything would come to a screetching halt. Ok, maybe not all boats... ;)
PAR
10-29-2007, 04:05 AM
Lightening can strike a metal mast, can damage equipment and all the rest. I've been struck twice, once in an unprotected production sailboat and the other in a well protected wooden ketch. Both strikes were on the mast (metal rod and wire on the ketch). The unprotected boat was holed by the strike, as its path out was through the centerboard pin, which the surrounding materials didn't like the quick rise in temperature. The ketch blew a few of the wire clamps, holding the cable to the mast, free and the connection between the masthead mounted rod and the cable was burned through. Some charred wood was evidenced under the cable, but this was the extent of the damage.
I've known of several people who have been struck aboard their yachts and repeatedly, the protected boats faired much better then the unprotected. I've read about lose of life from strikes, but it's reasonably rare and most had the misfortune of taking the strike on a body part (usually the head). Personally, I live in the lightening capital of the world. On a summers day, when the afternoon thunderheads build, we may experience 6,000 (typical average) in an hour. In particularly bad, usually very lager storm cells, doubling this number isn't uncommon. Things get hit, trust me. Automobiles are naturally protected by the insulating effect of their tires, though electronics can be affected. People in close proximity to a strike will get hurt, mast or not.
In direct answer to your question, yes you can die, but more often then not you'll just get the crap scared out of you. It's a matter of willingness to accept risk. You're willing to go father from shore then you can safely swim back too. You may have potentially explosive chemicals and fuels aboard this vessel. You have bits and parts of rig that can bonk you on the head well enough to mash your skull, but you can accept these risks, with understanding, equipment and reasonable skills. This same logic applies to lightening. Set up a protective cone for your yacht and you'll fair better then those that elected not to.
I've known of several people who have been struck aboard their yachts and repeatedly, the protected boats faired much better then the unprotected. I've read about lose of life from strikes, but it's reasonably rare and most had the misfortune of taking the strike on a body part (usually the head). Personally, I live in the lightening capital of the world. On a summers day, when the afternoon thunderheads build, we may experience 6,000 (typical average) in an hour. In particularly bad, usually very lager storm cells, doubling this number isn't uncommon. Things get hit, trust me. Automobiles are naturally protected by the insulating effect of their tires, though electronics can be affected. People in close proximity to a strike will get hurt, mast or not.
In direct answer to your question, yes you can die, but more often then not you'll just get the crap scared out of you. It's a matter of willingness to accept risk. You're willing to go father from shore then you can safely swim back too. You may have potentially explosive chemicals and fuels aboard this vessel. You have bits and parts of rig that can bonk you on the head well enough to mash your skull, but you can accept these risks, with understanding, equipment and reasonable skills. This same logic applies to lightening. Set up a protective cone for your yacht and you'll fair better then those that elected not to.
tuks
10-29-2007, 06:26 AM
Lightning is a risk, but I wouldnt worry too much about it. On the Vaal Dam there are over 1000 boats, in a fairly high risk lightling area(highveld thunderstorms almost every day in summer). Only a few boats get struck a year. There are other things which are more dangerous.
In one particularly bad storm, I have seen multiple strikes around me including the local farmers house which burned. I thought I was going to die. Its weird, when there is lightning around, I wont go fishing with a <3m long fishing rod, but am fairly comfortable in a boat with a 10m mast.
In one particularly bad storm, I have seen multiple strikes around me including the local farmers house which burned. I thought I was going to die. Its weird, when there is lightning around, I wont go fishing with a <3m long fishing rod, but am fairly comfortable in a boat with a 10m mast.
Fanie
10-29-2007, 06:52 AM
So it's a 'normal' :rolleyes: risk. Btw, lightning occurs from the earth up, and not down as is common believed.
We were at the Gariep dam (centre in SA), if you carried a carbon fishing rod you'd get shocked by the static. We were'nt long at the specific spot.
When fibre glass yacht building, do the builders glass metal into the boats for lightning diversion ?
We were at the Gariep dam (centre in SA), if you carried a carbon fishing rod you'd get shocked by the static. We were'nt long at the specific spot.
When fibre glass yacht building, do the builders glass metal into the boats for lightning diversion ?
tom28571
10-29-2007, 07:23 AM
Ok, I've read the posts made that Ike suggested, thanks. I still don't have an answer, is lightning on a boat with a metal mast life threatening,
The answer is, YES, a lightning strike on a sailboat mast is life threatening. It is a bit like crossing a street with blinders on. You may be killed and maybe not. Several people have given good answers to your questions. Ted's list is good. The best you can do is to study the problem, which you are doing, and then choose how you will work out your particular "solution."
Lightning is like the weather, it may be predictable but not very well.
The answer is, YES, a lightning strike on a sailboat mast is life threatening. It is a bit like crossing a street with blinders on. You may be killed and maybe not. Several people have given good answers to your questions. Ted's list is good. The best you can do is to study the problem, which you are doing, and then choose how you will work out your particular "solution."
Lightning is like the weather, it may be predictable but not very well.
ted655
10-29-2007, 11:15 AM
I have held many hot wires without injury., (rubber soled shoes on dry surface & spare hand in my pants pocket or holding the same item) Anyone can, as long as you don't become the path to ground. Give the lightning a better path on your boat, OR don't become the cross over TO a better path and "happy sailing" Provide a better conductor to ground than anything around you, (bare wet feet or both hands touching separate items), and it's "fried Popeye".
Fanie
10-29-2007, 11:25 AM
Lightning is like the weather, it may be predictable but not very well.
Sounds more like a female if you ask me ;)
Sounds more like a female if you ask me ;)
chandler
11-01-2007, 05:02 PM
Lightning goes from the ground up????, What would cause the earth to spew electricity????
Fanie
11-01-2007, 05:09 PM
Read up on lightning ;)
Fanie
11-01-2007, 05:36 PM
If lightning does pose a serious thread, why doesn't they glass metal sheets or strands in the cabins and hulls to divert the lightning ?
ted655
11-01-2007, 08:56 PM
There are "supposedly photos of ground to sky bolts. It's NOT accepted by most scientists &and (your right) it hasn't been explained. For my own health I will continue to follow those practices which have been tried & proven to work. I'm a sky to ground devotee.
.
Putting metal in an insulator does not prevent it from becoming a path to ground. Just ask those with fried electronics as a result of not unplugging them. Better yet, think of trees, surrounded by a non conductor layer of wood. They STILL become "The fastest, nost direct path to ground because they are internally wet". Remain the less desirable path to ground on the boat and sail confidently on.
Back to the "masts", they are chaise #1 for a strike. Do what you need to do & make damn certain the bolt follows it all the way to ground (straight path to a wet keel). The danger is, leading the strike down the mast, THEN slowing , bending or blocking the path. That is when it gets impatiens & starts jumping off, trying to find a quicker, wider path.
It's ALL about "path" guys, don't deny it a suitable path!
.
Putting metal in an insulator does not prevent it from becoming a path to ground. Just ask those with fried electronics as a result of not unplugging them. Better yet, think of trees, surrounded by a non conductor layer of wood. They STILL become "The fastest, nost direct path to ground because they are internally wet". Remain the less desirable path to ground on the boat and sail confidently on.
Back to the "masts", they are chaise #1 for a strike. Do what you need to do & make damn certain the bolt follows it all the way to ground (straight path to a wet keel). The danger is, leading the strike down the mast, THEN slowing , bending or blocking the path. That is when it gets impatiens & starts jumping off, trying to find a quicker, wider path.
It's ALL about "path" guys, don't deny it a suitable path!
TerryKing
11-02-2007, 07:40 AM
If lightning does pose a serious thread, why doesn't they glass metal sheets or strands in the cabins and hulls to divert the lightning ?
Fanie, the reason this is not done is that it would likely result in lots of damage and probably a fire. Lightning current rises from zero to 100,000 amps or more in a few millions of a second. That makes it effectively "high frequency" and much of the current flows in the outer portion of the conductor (wire). Therefore there is much more instantaneous heating than would be expected, even in a large wire.
Lightning conducted down through steel rebar in a concrete column may result in an internal explosion and significant damage to the column with a lightning strike. Wires inside a fibreglass laminate would probably cause similar damage.
High Radio/TV towers (200 to 350 feet) I had installed for broadcast stations always had the bottom of the tower (or it's base insulator if used) sitting on a concrete pillar. We always ran four copper straps about 4 inches wide and .062" thick from the tower base down the four sides of the concrete column, to a hefty ground system, to conduct lightning currents OUTSIDE the concrete.
This is a lot like the modern recommendations to have external shrouds, railings etc. on a boat connected to the water at the outer edges of the hull, not only down through the mast.
Take a look at:
http://boatdesign.net/forums/showthread.php?t=19662&highlight=lightning
for more discussion.
Fanie, the reason this is not done is that it would likely result in lots of damage and probably a fire. Lightning current rises from zero to 100,000 amps or more in a few millions of a second. That makes it effectively "high frequency" and much of the current flows in the outer portion of the conductor (wire). Therefore there is much more instantaneous heating than would be expected, even in a large wire.
Lightning conducted down through steel rebar in a concrete column may result in an internal explosion and significant damage to the column with a lightning strike. Wires inside a fibreglass laminate would probably cause similar damage.
High Radio/TV towers (200 to 350 feet) I had installed for broadcast stations always had the bottom of the tower (or it's base insulator if used) sitting on a concrete pillar. We always ran four copper straps about 4 inches wide and .062" thick from the tower base down the four sides of the concrete column, to a hefty ground system, to conduct lightning currents OUTSIDE the concrete.
This is a lot like the modern recommendations to have external shrouds, railings etc. on a boat connected to the water at the outer edges of the hull, not only down through the mast.
Take a look at:
http://boatdesign.net/forums/showthread.php?t=19662&highlight=lightning
for more discussion.
Ike
11-02-2007, 11:35 AM
You need first a basic understanding of lightning. I like to use the anology of a carbon arc lamp, with two carbon electrodes. As the electrodes approach each other they finally get close enough that the potential energy overcomes the resistance of the air gap and the spark jumps the gap, from both directions! I have actually seen this happen. It's pretty much the same with lightning. The clouds have a high negative charge. The earth is of course positive in relationship to the clouds, but with think of it as "ground" potential. As the current begins to find a low resistance path to ground through the air (that's why in photos of lightning it looks jagged) it follows the path toward ground. As soon as it gets close enough to ground to overcome the resistance of the air gap between it and ground a spark jumps FROM THE GROUND to the point in the air where the electric current is. So lightning appears to the human eye to come down because the last part happens so fast we can't see it, but high speed cameras have recorded it. So your boat is actually getting the part that goes up. You boat is the low resistance path for current to flow. But if you present an even lower resistance path, a very large cable from the top of the mast to a large metal mass under water, then in theory it takes that path.
By the way, experiments have shown that a mast or lightning rod with a dull rounded head works better than the traditional sharp pointed lightning rod.
The flaw in all of this is the simple fact that the current flow is so huge that it jumps to anything conductive that is near it's path to ground, thus frying your electronics.
I once had the tuner in my tv get fried. It didn't touch anything else, but the lightning hit the tree in my back yard, and enough current leaked down through my roof antenna that it fried my tuner. I assume that when that happened the tunner stopped conducting, in effect acting as a circuit breaker. When I replaced the tuner the tv worked fine. Can't do that with these solid state TVs.
Anyway, so lightning actually goes both ways, and researchers have actually recorded bolts strictly from the ground up to low lying clouds. I think the one that sticks in my mind is a video of a rocket being launched. They use rockets trailing a long thin wire to attempt to induce the lightning to start. The rocket takes off and litterally trails a large bolt of lightning behind it as it rises which is met by one from the clouds. Very dramatic. All this happens in a few seconds but they use high speed cameras to record it.
Oh I forgot to add. interposing dielectric material (an insulator) between the lightning and the interior of the boat doesn't work simply because the lightning is so powerful that it just blows a hole through the insulator. It would require insulation so thick that it wouldn't be practical to use on a boat.
By the way, experiments have shown that a mast or lightning rod with a dull rounded head works better than the traditional sharp pointed lightning rod.
The flaw in all of this is the simple fact that the current flow is so huge that it jumps to anything conductive that is near it's path to ground, thus frying your electronics.
I once had the tuner in my tv get fried. It didn't touch anything else, but the lightning hit the tree in my back yard, and enough current leaked down through my roof antenna that it fried my tuner. I assume that when that happened the tunner stopped conducting, in effect acting as a circuit breaker. When I replaced the tuner the tv worked fine. Can't do that with these solid state TVs.
Anyway, so lightning actually goes both ways, and researchers have actually recorded bolts strictly from the ground up to low lying clouds. I think the one that sticks in my mind is a video of a rocket being launched. They use rockets trailing a long thin wire to attempt to induce the lightning to start. The rocket takes off and litterally trails a large bolt of lightning behind it as it rises which is met by one from the clouds. Very dramatic. All this happens in a few seconds but they use high speed cameras to record it.
Oh I forgot to add. interposing dielectric material (an insulator) between the lightning and the interior of the boat doesn't work simply because the lightning is so powerful that it just blows a hole through the insulator. It would require insulation so thick that it wouldn't be practical to use on a boat.
Man Overboard
11-02-2007, 03:08 PM
These electrodes were meant to run through the hull, and according to Marine Lightning Protection Inc. They won't melt when the boat is struck by lightning I believe the insulator is Marelon.
http://marinelightning.com/
http://marinelightning.com/
Frosty
11-02-2007, 09:30 PM
Its difficult to estimate the power of lightening. Im not an expert in this field but if you've been within 100 yds of a strike it will all become clear. There is no explaining it.
You would not want that under your fibre glass.
I notice that many people say they live in a lightening prone area. Well Singapore is pretty good, they say that with a roll of film in a storm and you keep clicking you will photograph a strike.
Any way I have seen a small keel yacht get hit whilst on the hard sitting in a cradle. It looked to have done nothing untill I looked at it closer . A portion the size of a large hand had been de laminated--not blown out, but seriously damaged as the power tried to get out through to the cradle and into the ground.
I cant think of anything more silly than through hull lightening electrodes. How do they test them? I dont believe there is such a thing as lightening insulation, the power will build up untill it blows it apart.
I also believe that there is different kinds of lightening storms . Theres the very quick thin type that has a crack like a whip. Or theres the longer arc type that burns for enough time to see it ,maybe 1/4 of a second and has a thick arc maybe 6 feet across its width.
Motoring along at 4 am with no wind and torrential rain and a mast sticking into the sky during a storm like that is a humbling experience. You start to think defferently about --everything.
You would not want that under your fibre glass.
I notice that many people say they live in a lightening prone area. Well Singapore is pretty good, they say that with a roll of film in a storm and you keep clicking you will photograph a strike.
Any way I have seen a small keel yacht get hit whilst on the hard sitting in a cradle. It looked to have done nothing untill I looked at it closer . A portion the size of a large hand had been de laminated--not blown out, but seriously damaged as the power tried to get out through to the cradle and into the ground.
I cant think of anything more silly than through hull lightening electrodes. How do they test them? I dont believe there is such a thing as lightening insulation, the power will build up untill it blows it apart.
I also believe that there is different kinds of lightening storms . Theres the very quick thin type that has a crack like a whip. Or theres the longer arc type that burns for enough time to see it ,maybe 1/4 of a second and has a thick arc maybe 6 feet across its width.
Motoring along at 4 am with no wind and torrential rain and a mast sticking into the sky during a storm like that is a humbling experience. You start to think defferently about --everything.
PAR
11-03-2007, 01:29 AM
I've inspected vessels after lightening strikes and it can do a lot of damage, including blowing holes right through a hull. A lightening bolt can vary in intensity, from a few million volts to several tens of million. The Tampa Bay area is the lightening capital of the world, with the general central Florida region being nearly equal in frequency of strikes. Several places around the world also have their share of unusually high strike activity. The unprotected strike I mentioned earlier, was at the mouth of Tampa Bay.
I've seen space shuttle video of lightening going up from clouds, literally into space.
You can protect your boat and several companies offer packages that work.
I've seen space shuttle video of lightening going up from clouds, literally into space.
You can protect your boat and several companies offer packages that work.
FAST FRED
11-03-2007, 05:54 AM
Any ideas on keeping a boat with electronic injection diesel engine running after a strike?
Only two "solutions " I've heard so far is have a metal boat and 6 spare computer packs and pray.
FF
Only two "solutions " I've heard so far is have a metal boat and 6 spare computer packs and pray.
FF
Frosty
11-03-2007, 06:21 AM
Even then the computer packs rely on various senders for feed back of information.
A complete wiring loom, computer pack, and every sender on the engine.
And you'lle still need to pray.
I really don't know what these engine manufacturers are thinking of. They may be more economical but whats the point when fuel goes up every year.
A complete wiring loom, computer pack, and every sender on the engine.
And you'lle still need to pray.
I really don't know what these engine manufacturers are thinking of. They may be more economical but whats the point when fuel goes up every year.
tom28571
11-03-2007, 07:36 AM
You can protect your boat and several companies offer packages that work.
Which packages and which companies? Some are just feel good stuff. How would you suggest protection for a sailboat without a metal keel? Not trying to put you on the spot.
Which packages and which companies? Some are just feel good stuff. How would you suggest protection for a sailboat without a metal keel? Not trying to put you on the spot.
Fanie
11-03-2007, 08:24 AM
Here's what I think.
The risk of getting hit by lightning is not neccessary higher because you're on a yacht, unless you're right in the direct place the bolt would discharge. I don't think this risk is any higher than lightning hitting your house. I've seen a house's brick awning knocked off and a concrete wall right between two buildings disintegrated on seperate occasions. Why not hit the houses which were beside it...
You ever stood on a high building looking down ? You're not even close to the clouds where the discharge would take place, yet the objects protruding upwards looks insignificant. So why on earth would lightning specifically pick your little mast to discharge through ? It's like you looking down to your lawn and wants to focus on the ant that sits on a grass stem. Truth, you don't even see the ant.
Besides, lightning is good (if it's somewhere else :rolleyes:), it creates many tonnes of ozone killing bac and teria and generates plenty of oxygen.
Getting hit is merely a matter of unfotunately happening to be just in the right spot at the wrong time. One advantage is that us humans are not very conductive, so unless you drink a LOT of sea water, you could consider yourself pretty safe.
So I don't think we get picked on more than is probably needed, and some people needs a bit of lightning every now and again eh !
The risk of getting hit by lightning is not neccessary higher because you're on a yacht, unless you're right in the direct place the bolt would discharge. I don't think this risk is any higher than lightning hitting your house. I've seen a house's brick awning knocked off and a concrete wall right between two buildings disintegrated on seperate occasions. Why not hit the houses which were beside it...
You ever stood on a high building looking down ? You're not even close to the clouds where the discharge would take place, yet the objects protruding upwards looks insignificant. So why on earth would lightning specifically pick your little mast to discharge through ? It's like you looking down to your lawn and wants to focus on the ant that sits on a grass stem. Truth, you don't even see the ant.
Besides, lightning is good (if it's somewhere else :rolleyes:), it creates many tonnes of ozone killing bac and teria and generates plenty of oxygen.
Getting hit is merely a matter of unfotunately happening to be just in the right spot at the wrong time. One advantage is that us humans are not very conductive, so unless you drink a LOT of sea water, you could consider yourself pretty safe.
So I don't think we get picked on more than is probably needed, and some people needs a bit of lightning every now and again eh !
TerryKing
11-03-2007, 08:40 AM
Any ideas on keeping a boat with electronic injection diesel engine running after a strike?
Fred, that's an interesting area to try to figure out.
One of the significant parts of the problem is, like Frosty just said, "Even then the computer packs rely on various senders for feed back of information. A complete wiring loom, computer pack, and every sender on the engine."
Two unfortunate realities:
1. All the wiring for the many sensors, monitoring NMEA signals, engine alarms etc etc. act as ANTENNAS when there is lots of electromagnetic energy around.
2. Lightning currents rise so quickly that the discharges are effectively huge radio transmitters.
Ike had the experience: " I once had the tuner in my tv get fried. It didn't touch anything else, but the lightning hit the tree in my back yard, and enough current leaked down through my roof antenna that it fried my tuner."
I think, in Ike's case, that the huge instantaneous magnetic field caused by the nearby lightning strike was coupled (like in a transformer) to his home antenna wire, and was powerful enough to damage his tuner. This is a well-known effect in Lightning damage.
Oh, but Fred asked for ideas! I've been thinking about this in the context of the Onboard Computer project I'm working on. (http://www.boatdesign.net/forums/showthread.php?t=19458 if you're interested).
I have a couple of ideas:
1. Adopt a boat mast/rigging/lightning protection conductor approach that creates multiple lightning paths around and outside the center of the boat where the humans and systems are. There is a whole discussion on this here:
http://boatdesign.net/forums/showthread.php?t=19662&highlight=lightning
where Fred started a major discussion on this. See the posts / information on this concept.
2. Don't use any wires (AKA Antennae) for sensors, alarms, system monitoring etc. Connect them with FibreOptic lines, or Wireless (Wireless USB, ZigBee, or others).
AND, do some serious lightning protection design work on the individual electronics boxes like Onboard Computers, Electronic Engine Controls, AutoPilot, Power control systems, etc. This is non-trivial work!
I am asking some questions of this guy who designs electronics with lots of sensors, microcomputers, etc., and then puts hundreds of them up on mountains with high metal towers and wires running down the tower. The installations look like this:
http://www.terryking.us/boatbuilding/4066-4067-4068_blowup.jpg
This looks a lot like a big sailboat, asking for Lightning Trouble!
There's two parts to this:
1. Encase the electronics system in a sturdy metal box
2. Filter and protect ALL wires going in and out of the box against Over-voltage and Over-Current.
Quite a lot is known about such protection and appropriate devices. I did a lot of that, building broadcast transmitter sites, back in the day. And the Engineering Manager at nrgsystems.com who makes those towers with sensors has sent me a few samples of what they use.
But I'm really thinking that the best approach is: No Wires!
Fred, that's an interesting area to try to figure out.
One of the significant parts of the problem is, like Frosty just said, "Even then the computer packs rely on various senders for feed back of information. A complete wiring loom, computer pack, and every sender on the engine."
Two unfortunate realities:
1. All the wiring for the many sensors, monitoring NMEA signals, engine alarms etc etc. act as ANTENNAS when there is lots of electromagnetic energy around.
2. Lightning currents rise so quickly that the discharges are effectively huge radio transmitters.
Ike had the experience: " I once had the tuner in my tv get fried. It didn't touch anything else, but the lightning hit the tree in my back yard, and enough current leaked down through my roof antenna that it fried my tuner."
I think, in Ike's case, that the huge instantaneous magnetic field caused by the nearby lightning strike was coupled (like in a transformer) to his home antenna wire, and was powerful enough to damage his tuner. This is a well-known effect in Lightning damage.
Oh, but Fred asked for ideas! I've been thinking about this in the context of the Onboard Computer project I'm working on. (http://www.boatdesign.net/forums/showthread.php?t=19458 if you're interested).
I have a couple of ideas:
1. Adopt a boat mast/rigging/lightning protection conductor approach that creates multiple lightning paths around and outside the center of the boat where the humans and systems are. There is a whole discussion on this here:
http://boatdesign.net/forums/showthread.php?t=19662&highlight=lightning
where Fred started a major discussion on this. See the posts / information on this concept.
2. Don't use any wires (AKA Antennae) for sensors, alarms, system monitoring etc. Connect them with FibreOptic lines, or Wireless (Wireless USB, ZigBee, or others).
AND, do some serious lightning protection design work on the individual electronics boxes like Onboard Computers, Electronic Engine Controls, AutoPilot, Power control systems, etc. This is non-trivial work!
I am asking some questions of this guy who designs electronics with lots of sensors, microcomputers, etc., and then puts hundreds of them up on mountains with high metal towers and wires running down the tower. The installations look like this:
http://www.terryking.us/boatbuilding/4066-4067-4068_blowup.jpg
This looks a lot like a big sailboat, asking for Lightning Trouble!
There's two parts to this:
1. Encase the electronics system in a sturdy metal box
2. Filter and protect ALL wires going in and out of the box against Over-voltage and Over-Current.
Quite a lot is known about such protection and appropriate devices. I did a lot of that, building broadcast transmitter sites, back in the day. And the Engineering Manager at nrgsystems.com who makes those towers with sensors has sent me a few samples of what they use.
But I'm really thinking that the best approach is: No Wires!
Fanie
11-03-2007, 08:55 AM
Of course a non-metalic mast and lines would be ideal. The sailing boat have another problem, there is no-where you can earth anything like in EARTing it, so the boat's metal parts are floating , as the boat is floating on the water. You could drop the achor on a metal cable, but this may rather invite lightning to take short cut to ground.
ted655
11-03-2007, 09:38 AM
The risk of getting hit by lightning is not neccessary higher because you're on a yacht, unless you're right in the direct place the bolt would discharge. I don't think this risk is any higher than lightning hitting your house. I
.
.
I disagree. Lightning looks for the tallest object to provide a path. That is why water & golf courses, soccer fields, etc. are more often sites of people being struck.
.
For my part, OK...., so lightning hit my boat! It traveled down my mast & blew (or burned or whatever) a hole around my thru hull. It may even have toasted my engine & fried my radio. The sound made me pee my pants & gave me minor shell shock, BUT, I'm OK. I'll live to repair or replace whatever I need to. I can even read the latest opinions & theory's of source and behavior of lightning. WHY? Because I gave the one bolt that picked me, A BETTER PATH than my body to ground (or sky).
For me, the rest is purely academic, because I'm alive!
.
.
I disagree. Lightning looks for the tallest object to provide a path. That is why water & golf courses, soccer fields, etc. are more often sites of people being struck.
.
For my part, OK...., so lightning hit my boat! It traveled down my mast & blew (or burned or whatever) a hole around my thru hull. It may even have toasted my engine & fried my radio. The sound made me pee my pants & gave me minor shell shock, BUT, I'm OK. I'll live to repair or replace whatever I need to. I can even read the latest opinions & theory's of source and behavior of lightning. WHY? Because I gave the one bolt that picked me, A BETTER PATH than my body to ground (or sky).
For me, the rest is purely academic, because I'm alive!
Ike
11-03-2007, 11:26 AM
Lightning simply takes the least resistance path to ground. If that path is you, well, it's been nice to know you. Although some people have survived lightning strikes. But if your mast is metal, it is a much lower resistance path to ground than the air surrounding it. So when you are out on the water, the lowest resistance path around happens to be your mast.
I was out on a Lake in Utah with lightning all around but my mast was wood. Fortunately none of the lightning struck close enough to do any damage, although my son made the mistake of touching the wire shrouds and got a nasty static discharge. So most lighnting protection systems are based on the simple idea that if you provide a lower resistance path to ground, it will take that instead of you or the hull under you.
I had some nasty experiences with lightning in Utah, Talk about another place with a high lightning frequency. Geez. I was convinced it was out to get me.
I was out on a Lake in Utah with lightning all around but my mast was wood. Fortunately none of the lightning struck close enough to do any damage, although my son made the mistake of touching the wire shrouds and got a nasty static discharge. So most lighnting protection systems are based on the simple idea that if you provide a lower resistance path to ground, it will take that instead of you or the hull under you.
I had some nasty experiences with lightning in Utah, Talk about another place with a high lightning frequency. Geez. I was convinced it was out to get me.
tuks
11-03-2007, 07:21 PM
So I thought I lived in a lightning prone area, I guess I was wrong.
From Usatoday.com
The spot with the most lightning lies deep in the mountains of eastern Democratic Republic of the Congo near the small village of Kifuka (elevation 3200 feet, 970 m). Thunderbolts pelt this land.
Strikes averaged from April 1995 to February 2003 (http://thunder.nsstc.nasa.gov/images/HRFC_AnnualFlashRate_cap.jpg) - Note that over the oceans and desert "white" means no lightning.
Courtesy of NASA's Lightning Imaging Sensor (LIS) Instrument Team and the Global Hydrology Resource Center (GHRC). .
The black dot (in the middle of the largest white area in Central Africa) marks the spot — near the tiny town of Kifuka in the Democratic Republic of the Congo — where the greatest lightning activity in the world occurs. The color code at the top of the image shows the number of flashes per square kilometer during the year. Note that over the oceans and desert "white" means no lightning.
In a year, 158 bolts occur over each square kilometer (10 city-blocks square), says atmospheric physicist Steve Goodman of NASA's Global Hydrology and Climate Center (GHCC) in Huntsville, Alabama.
Say out of the red patches and you should be ok.
From Usatoday.com
The spot with the most lightning lies deep in the mountains of eastern Democratic Republic of the Congo near the small village of Kifuka (elevation 3200 feet, 970 m). Thunderbolts pelt this land.
Strikes averaged from April 1995 to February 2003 (http://thunder.nsstc.nasa.gov/images/HRFC_AnnualFlashRate_cap.jpg) - Note that over the oceans and desert "white" means no lightning.
Courtesy of NASA's Lightning Imaging Sensor (LIS) Instrument Team and the Global Hydrology Resource Center (GHRC). .
The black dot (in the middle of the largest white area in Central Africa) marks the spot — near the tiny town of Kifuka in the Democratic Republic of the Congo — where the greatest lightning activity in the world occurs. The color code at the top of the image shows the number of flashes per square kilometer during the year. Note that over the oceans and desert "white" means no lightning.
In a year, 158 bolts occur over each square kilometer (10 city-blocks square), says atmospheric physicist Steve Goodman of NASA's Global Hydrology and Climate Center (GHCC) in Huntsville, Alabama.
Say out of the red patches and you should be ok.
PAR
11-03-2007, 07:22 PM
The National Agricultural Safety Database out of the U of F
http://www.cdc.gov/nasd/docs/d000001-d000100/d000007/d000007.html
MLP Inc.
http://www.marinelightning.com/
Ewen Thomson's excellent work
http://www.marinelightning.com/Information/GroundingConcepts.htm
ABYC recommends 4 gauge copper (tined) to the mast head on composite or wooden masts. 6 gauge bonding to all major metal components (tanks, engine, etc.) Air gaps, rods, all the exspected stuff.
There are others, but these will put a search on the right path to ground (couldn't resist Tom).
http://www.cdc.gov/nasd/docs/d000001-d000100/d000007/d000007.html
MLP Inc.
http://www.marinelightning.com/
Ewen Thomson's excellent work
http://www.marinelightning.com/Information/GroundingConcepts.htm
ABYC recommends 4 gauge copper (tined) to the mast head on composite or wooden masts. 6 gauge bonding to all major metal components (tanks, engine, etc.) Air gaps, rods, all the exspected stuff.
There are others, but these will put a search on the right path to ground (couldn't resist Tom).
tom28571
11-03-2007, 11:24 PM
Fair enough. These are some of the only reasonable approaches I have seen for lightning protection. There is so much snake oil out there, I did not know what you were referring to. These people do seem to avoid any sharp bends and keep the grounding conductors away from the hull sides which can cause a blowout to water through the hull. Just connecting the various metal parts of the boat to ground is not good enough.
Actually finding a reasonable path to lead the conductors to ground while following the right procedure can be a real problem on a lot of boats though.
Then, there is the bottle brushes and their claims which I question. There is also the claims made for the sintered porus copper grounding bars which are bogus.
Actually finding a reasonable path to lead the conductors to ground while following the right procedure can be a real problem on a lot of boats though.
Then, there is the bottle brushes and their claims which I question. There is also the claims made for the sintered porus copper grounding bars which are bogus.
TerryKing
11-04-2007, 12:28 AM
..(snip).. These are some of the only reasonable approaches I have seen for lightning protection. There is so much snake oil out there
Agreed! Bluntly a lot of discussions about Lightning border on the FolkTale, including those on BoatDesign. Everyone, Please read those pages first!
I had a LOT of trouble getting to those pages for some reason. I had to go through a weird proxy combination. Maybe it's subversive here in Communist China where I live? Here are alternatives in case you have problems.
First, try http://www.marinelightning.com/ directly. If that doesn't work,
try:
Overview of the problem and possible solutions:
http://www.terryking.us/boatbuilding/MarineLightningProtectionInc.pdf
Technical Paper on Grounding Concepts for Lightning and Boats:
http://www.terryking.us/boatbuilding/GroundingConceptsLightningBoats.pdf
Sometime, Someone should add a section on this on the WIKI under "Electrical Systems". If you're reading this, maybe YOU!
Agreed! Bluntly a lot of discussions about Lightning border on the FolkTale, including those on BoatDesign. Everyone, Please read those pages first!
I had a LOT of trouble getting to those pages for some reason. I had to go through a weird proxy combination. Maybe it's subversive here in Communist China where I live? Here are alternatives in case you have problems.
First, try http://www.marinelightning.com/ directly. If that doesn't work,
try:
Overview of the problem and possible solutions:
http://www.terryking.us/boatbuilding/MarineLightningProtectionInc.pdf
Technical Paper on Grounding Concepts for Lightning and Boats:
http://www.terryking.us/boatbuilding/GroundingConceptsLightningBoats.pdf
Sometime, Someone should add a section on this on the WIKI under "Electrical Systems". If you're reading this, maybe YOU!
Fanie
11-04-2007, 02:22 AM
in the middle of the largest white area in Central Africa
I didn't know there was whites it the Congo any more :D But they do have the goliath tiger fish there. Gets to be over 80kg in weight. Someone told me it's like getting hooked into a passing freight train at speed.
I didn't know there was whites it the Congo any more :D But they do have the goliath tiger fish there. Gets to be over 80kg in weight. Someone told me it's like getting hooked into a passing freight train at speed.
lazeyjack
11-04-2007, 06:15 PM
Lightning Strike
This is a copy of the article published in Yachting Monthly
My wife, Monique, and I had traveled the Intracoastal Waterway from Key West to Norfolk, Virginia, in our Moody 36, - Bambola Quatre, then cruised Chesapeake Bay, up the Potomac River to Washington DC. From the mouth of the Potomac to Washington took two and a half days. Once under the final bridge (with 2ft to spare above the vhf antenna), we anchored near a metro station five minutes from the center of Washington.
After three wonderful weeks being tourists I had to return to the UK for a short time so decided to leave the boat in a cheap and safe marina not far from Baltimore Airport. We needed to get back under the bridge at dead Low Water so I started the engine and switched on my handheld VHF in order to communicate with commercial shipping. Then the US Coast Guard issued a storm warning, advising all boats in the Washington area to seek shelter so I dropped the hook again.
I stood in the cockpit in the pouring rain, bare feet, in shorts and T shirt with water splashing around my ankles counting the sound of thunder claps. They were some 4 seconds apart, then 3 then two. Within five minutes the wind piped up and even in the sheltered anchorage it gusted to 45 knots. Just as suddenly it dropped the thunder claps were only a second apart and then there was an explosive bang: Like a huge artillery piece going off. A giant thunderclap directly overhead.
Monique screamed.
Drenching rain reduced visibility to a few yards and I saw plastic debris falling on to the deck. The wind came up again quickly to around gale force and went round 180°. The anchor started to drag.
I motored into the wind to take the strain off the anchor and keep us from the very nearby lee shore. The engine alarm went off and I saw it was overheating. Shutting it down and running forward, I threw the second anchor into the water and paid out chain and warp. We stopped about 6 metres from a concrete wall.
I went below to find out why the engine had overheated and I heard the little domestic radio receiving VHF transmissions -which it was not supposed to do. Then it died.
Monique, who really does not like boats or cruising, asked if it was normal for her hair to stand on end? I did not realise she was speaking literally.
The main VHF glowed for a moment, then died. The SSB had switched itself on but the display was blank. That was when I realised our yacht had taken a direct lightning hit.
On deck again I found the wind instruments were all out and the masthead was bare. The VHF antenna and wind direction/speed unit were gone; lying beside the cockpit were the remains of the Hawk wind indicator.
People watching from the marina said a fireball had hovered around our masthead. It had been a severe strike. We were lucky to be alive.
In the engine room, investigating the overheating problem, I decided that the thermostat must have failed. With the nuts removed I found that the steel engine bolts had frozen themselves on to the alloy thermostat housing.
Close examination showed a core plug had cracked and was blown half out of the manifold. I was definitely not going to move the boat that day.
We went ashore and I e-mailed the information to Pantaenius, my insurance company. I also e-mailed an order to ASAP for a core plug and thermostat housing.
Next morning I spoke to Mike, the Pantaeneus Claims Manager, who was considerate and very helpful. His advice: find a suitable marine electronics yard to do the repairs -possibly in Annapolis - and he would authorise them and send a surveyor.
He warned me to be careful moving the boat as occasionally lightning strikes damage the skin fittings and allows a major ingress of water.
I called ASAP to confirm that the order was on its way and found that it wasn't - I'd asked for it to be sent FedEx and at £30 to ship it (the order was only worth £ 12) they had considered it too expensive. I told them it was essential to have the part by Friday. I then went to find Bill, the excellent local mechanic, who said he would try to find a suitable core plug locally.
Tuesday dawned and I discovered the 'house' batteries were going flat. The battery control system was out. The multimeter showed that there was nothing coming out of the solar panel at midday and the wind generator refused to function. We now had no engine, no solar or wind power and some shorts in the system were pulling the house batteries down.
To my horror I found that, because it was late June, all the repair facilities in Annapolis and Baltimore were at full stretch. Then 1 was recommended to a company in Cambridge. Maryland, called Mid-Shore Electronics .The owner Marty, said that if I could get to Cambridge, on the eastern side of Bay. by the weekend, they could haul me out on Monday.
Mike at Pantaeneus told me he would arrange for a surveyor lo be there on Monday. I called ASAP to be told that FedEx had not been able to guarantee the core plug delivery by Friday so the order had not been dispatched in case it was too late -but I would get it on Monday next.
Bill, the local mechanic, found that no local US core plugs fitted my block so he would try to get one engineered.
It was very hot and the house batteries were very flat. I was keeping my finger crossed that the engine battery would have enough power to let me start up. Then I realised I didn't have an echo sounder. The Potomac and frequently the Chesapeake are very shallow with anchorages that your creep into with just inches below your keel.
Bill drove me 10 miles to West Marine where I purchased a Fishfinder echo sounder: it would have been almost impossible to motor-sail the 150 miles from to Cambridge, including overnight anchoring without it.
Monday dawned but the FedEx parcel did not. However, on Tuesday at 1000 the delivery happened and by 1100 the engine was assembled. By 1130 we were u under way - and no longer concerned with the low bridge as Bambola’s mast height had been reduced by the loss of the VHF antenna by 3ft.
After two days of motor sailing we entered the Choplack River, arriving at the yard in Cambridge, Maryland 10 minutes after it closed for the weekend.
Marty from Mid-Shore Electronics arrived on Monday and went through the boat with me - virtually every electrical item had been damaged. I had installed almost every bit of the electronic equipment myself and it was painful to see the results of so much time and effort destroyed.
Charles, the Pantaenius-appointed surveyor, arrived.
Bambola Quatre was hauled, Marty was authorised to carry out the work and Pantaeneus transferred a deposit. The final cost to Pantaeneus was $37.000 (about £23.000). II cost me almost four months' cruising and my deductible £1,000, plus 30% of the cost of the new radar and VHF which were both more than 10 years old. Incidental costs such as air fares, car hire and phone calls have added around another£1.000.
I was lucky that everything in the boat was properly bonded to keel bolts, Dyna plate, sacrificial anodes and prop shaft.
My mast support is stainless and bonded to keel bolts in the hull. There was a lot of discoloration between the foot of the mast and the deck plate. I recently delivered a brand new boat – a Bavaria - to the Mediterranean and was surprised to see that the bonding of the electronics was non-existent.
This is a copy of the article published in Yachting Monthly
My wife, Monique, and I had traveled the Intracoastal Waterway from Key West to Norfolk, Virginia, in our Moody 36, - Bambola Quatre, then cruised Chesapeake Bay, up the Potomac River to Washington DC. From the mouth of the Potomac to Washington took two and a half days. Once under the final bridge (with 2ft to spare above the vhf antenna), we anchored near a metro station five minutes from the center of Washington.
After three wonderful weeks being tourists I had to return to the UK for a short time so decided to leave the boat in a cheap and safe marina not far from Baltimore Airport. We needed to get back under the bridge at dead Low Water so I started the engine and switched on my handheld VHF in order to communicate with commercial shipping. Then the US Coast Guard issued a storm warning, advising all boats in the Washington area to seek shelter so I dropped the hook again.
I stood in the cockpit in the pouring rain, bare feet, in shorts and T shirt with water splashing around my ankles counting the sound of thunder claps. They were some 4 seconds apart, then 3 then two. Within five minutes the wind piped up and even in the sheltered anchorage it gusted to 45 knots. Just as suddenly it dropped the thunder claps were only a second apart and then there was an explosive bang: Like a huge artillery piece going off. A giant thunderclap directly overhead.
Monique screamed.
Drenching rain reduced visibility to a few yards and I saw plastic debris falling on to the deck. The wind came up again quickly to around gale force and went round 180°. The anchor started to drag.
I motored into the wind to take the strain off the anchor and keep us from the very nearby lee shore. The engine alarm went off and I saw it was overheating. Shutting it down and running forward, I threw the second anchor into the water and paid out chain and warp. We stopped about 6 metres from a concrete wall.
I went below to find out why the engine had overheated and I heard the little domestic radio receiving VHF transmissions -which it was not supposed to do. Then it died.
Monique, who really does not like boats or cruising, asked if it was normal for her hair to stand on end? I did not realise she was speaking literally.
The main VHF glowed for a moment, then died. The SSB had switched itself on but the display was blank. That was when I realised our yacht had taken a direct lightning hit.
On deck again I found the wind instruments were all out and the masthead was bare. The VHF antenna and wind direction/speed unit were gone; lying beside the cockpit were the remains of the Hawk wind indicator.
People watching from the marina said a fireball had hovered around our masthead. It had been a severe strike. We were lucky to be alive.
In the engine room, investigating the overheating problem, I decided that the thermostat must have failed. With the nuts removed I found that the steel engine bolts had frozen themselves on to the alloy thermostat housing.
Close examination showed a core plug had cracked and was blown half out of the manifold. I was definitely not going to move the boat that day.
We went ashore and I e-mailed the information to Pantaenius, my insurance company. I also e-mailed an order to ASAP for a core plug and thermostat housing.
Next morning I spoke to Mike, the Pantaeneus Claims Manager, who was considerate and very helpful. His advice: find a suitable marine electronics yard to do the repairs -possibly in Annapolis - and he would authorise them and send a surveyor.
He warned me to be careful moving the boat as occasionally lightning strikes damage the skin fittings and allows a major ingress of water.
I called ASAP to confirm that the order was on its way and found that it wasn't - I'd asked for it to be sent FedEx and at £30 to ship it (the order was only worth £ 12) they had considered it too expensive. I told them it was essential to have the part by Friday. I then went to find Bill, the excellent local mechanic, who said he would try to find a suitable core plug locally.
Tuesday dawned and I discovered the 'house' batteries were going flat. The battery control system was out. The multimeter showed that there was nothing coming out of the solar panel at midday and the wind generator refused to function. We now had no engine, no solar or wind power and some shorts in the system were pulling the house batteries down.
To my horror I found that, because it was late June, all the repair facilities in Annapolis and Baltimore were at full stretch. Then 1 was recommended to a company in Cambridge. Maryland, called Mid-Shore Electronics .The owner Marty, said that if I could get to Cambridge, on the eastern side of Bay. by the weekend, they could haul me out on Monday.
Mike at Pantaeneus told me he would arrange for a surveyor lo be there on Monday. I called ASAP to be told that FedEx had not been able to guarantee the core plug delivery by Friday so the order had not been dispatched in case it was too late -but I would get it on Monday next.
Bill, the local mechanic, found that no local US core plugs fitted my block so he would try to get one engineered.
It was very hot and the house batteries were very flat. I was keeping my finger crossed that the engine battery would have enough power to let me start up. Then I realised I didn't have an echo sounder. The Potomac and frequently the Chesapeake are very shallow with anchorages that your creep into with just inches below your keel.
Bill drove me 10 miles to West Marine where I purchased a Fishfinder echo sounder: it would have been almost impossible to motor-sail the 150 miles from to Cambridge, including overnight anchoring without it.
Monday dawned but the FedEx parcel did not. However, on Tuesday at 1000 the delivery happened and by 1100 the engine was assembled. By 1130 we were u under way - and no longer concerned with the low bridge as Bambola’s mast height had been reduced by the loss of the VHF antenna by 3ft.
After two days of motor sailing we entered the Choplack River, arriving at the yard in Cambridge, Maryland 10 minutes after it closed for the weekend.
Marty from Mid-Shore Electronics arrived on Monday and went through the boat with me - virtually every electrical item had been damaged. I had installed almost every bit of the electronic equipment myself and it was painful to see the results of so much time and effort destroyed.
Charles, the Pantaenius-appointed surveyor, arrived.
Bambola Quatre was hauled, Marty was authorised to carry out the work and Pantaeneus transferred a deposit. The final cost to Pantaeneus was $37.000 (about £23.000). II cost me almost four months' cruising and my deductible £1,000, plus 30% of the cost of the new radar and VHF which were both more than 10 years old. Incidental costs such as air fares, car hire and phone calls have added around another£1.000.
I was lucky that everything in the boat was properly bonded to keel bolts, Dyna plate, sacrificial anodes and prop shaft.
My mast support is stainless and bonded to keel bolts in the hull. There was a lot of discoloration between the foot of the mast and the deck plate. I recently delivered a brand new boat – a Bavaria - to the Mediterranean and was surprised to see that the bonding of the electronics was non-existent.
SeerAtlas
11-05-2007, 03:49 PM
Question, Was your mast taller than the other boats around you?
BTW, every strike on a yacht I've heard of resulted in masthead fittings either 'disappearing' or raining to the deck in pieces. If nothing else, this indicates to me that the *highest point* proposition has some validity.
As for metal vs. other substances..I've got a small ranch that encompasses a 3 or 400 foot high hill about a quarter mile from the gate which is low in the valley. I had just let go of the gate, my hands probably a foot from it, when it was struck by lightning. It blew me off my feet and back about ten feet, and may have knocked me out for a few seconds. This area was surrounded by trees 30 to 40 feet higher than that gate for miles in all directions, yet it went for the metal.
Put these two together and just off hand, it seems to me, that those with wood (dry) :) or fibreglass masts without a lot of cabling or steel on them are likely to fare better than the guys near them with steel or aluminum masts. I'll have to find some scientific studies on this, but running a thick steel or copper cable up that wood or fibreglass mast might amount to setting out the doormat and crying "HIT ME" .
I'd be interested in seeing reports from the pre-steamship era on the lightning damage to wooden ships at sea.
seer
BTW, every strike on a yacht I've heard of resulted in masthead fittings either 'disappearing' or raining to the deck in pieces. If nothing else, this indicates to me that the *highest point* proposition has some validity.
As for metal vs. other substances..I've got a small ranch that encompasses a 3 or 400 foot high hill about a quarter mile from the gate which is low in the valley. I had just let go of the gate, my hands probably a foot from it, when it was struck by lightning. It blew me off my feet and back about ten feet, and may have knocked me out for a few seconds. This area was surrounded by trees 30 to 40 feet higher than that gate for miles in all directions, yet it went for the metal.
Put these two together and just off hand, it seems to me, that those with wood (dry) :) or fibreglass masts without a lot of cabling or steel on them are likely to fare better than the guys near them with steel or aluminum masts. I'll have to find some scientific studies on this, but running a thick steel or copper cable up that wood or fibreglass mast might amount to setting out the doormat and crying "HIT ME" .
I'd be interested in seeing reports from the pre-steamship era on the lightning damage to wooden ships at sea.
seer
SeerAtlas
11-05-2007, 04:55 PM
If you want to avoid the merchandising point of view, take a look at this.
http://assets.cambridge.org/052158/3276/sample/0521583276WS.pdf
seer
http://assets.cambridge.org/052158/3276/sample/0521583276WS.pdf
seer
longliner45
11-05-2007, 07:18 PM
ok fellas ..I am not a rocket scientist ,,I am a power lineman,I see and deal with lighting strikes all the time,,,what I find is ,,it damages equipt and goes into the house ,via ,your service ,,it does,, but rarely blow the top of the pole off,I have seen damage to fishing boats made of wood,,,bows splinterd as she was broaching a wave .,one thing I would like to clarify ,is electricity is always trying to find a way to ground,so I dont buy the photos of lighting reaching up from the ground ,,,now with that said .(question)if you have a wooden boat,,and a aulminium mast,,which should be inuslated,from ground.via wood ,are you ok? ,,it is not called electrical theory because we know all ,,it is called theory because of variances..dirt will tract,wet wood will tract and so on,,,,,,my asumption is that since you are on a boat ,,you are a delta system,supplying your own ground ... but at least while you are tied up at the dock ,,and not there to oversee,you could take some precautions,likegrounding your boat with number2 copper,to a stake in the ground or systems nuetral,but off shore you will be on your own,,and also if you done the latter ,,,what about electrallisis?,,,,basically Im asking the old salts here....also if you look at every power pole ,,you will see a number 6 copper ground wire
PAR
11-05-2007, 08:19 PM
A lightening strike is just like picking the number for the local lottery, the odds are the same regardless of how close they've come before. The average ranges from 400,00 to 600,000:1 odds you'll get a spike close enough to seriously harm you. It may increase or decrease your odds slightly, if you're the highest or lowest thing around, but the strike is reasonably random in nature, so most folks can feel pretty luckily, if a bit scared in a storm. It can hit a ball player on the mound, while missing the stadium towering around him. It can hit a golfer (whether he's in mid swing or not) in spite of 50' trees on each side of the fairway. It's random, though being on the water with a metal stick jutting skyward is increasing your odds (but not by as much as you'd think), it's still random occurrences. Protect you're boat, avoid nasty weather when you can and you'll likely be one of the 99% of the boating public that doesn't have an issue in their life time.
longliner45
11-05-2007, 08:49 PM
thanks for calming the quell par,, but also,,lightening does strike twice,on many of our circuits we know were to go from past strikes,,,and most of the time it is the same ,,lightening,,as you said it is random.for some reasons it repeats and others it is just one time ,,I think I will pass on putting a bunch of money and time in prevention ,,,,,just me ,,It is probably better for me to worrie about drunk boaters and electrallisis ,,,longliner
Ike
11-06-2007, 01:13 PM
I just got my October issue of Technical Information Exchange, put out by BoatUS primarily for Marine Surveyors and Investigators, but a really interesting read for designers and builders. You have to subscribe to read it on-line as well. http://www.boatus.com/scripts/technical/
Anyway, in this issue there is a very good article by Ewen Thompson on lightning protect that takes a whole new approach. It is essentially protecting boats the same way buildings are protected on shore. He proposes using multiple air terminals around the periphery of the boat with multiple external conductors on the outside of the boat, terminating at a grounding loop at or near the waterline, that goes all the way around the boat. I wish this article were online for all to read but they haven't put it on the BoatUS Web site yet and I wasn't able to find it anywhere else on line. The U of Florida web site on lightning say Ewen Thompson no longer works there all though they have his web site up. His new web site is http://www.marinelightning.com/consulting.htm. A synopsis of the history of lightning protection is at http://www.marinelightning.com/science.htm#Solutions and near the end of the page he goes into using multiple air terminals and side conductors.
Anyway, in this issue there is a very good article by Ewen Thompson on lightning protect that takes a whole new approach. It is essentially protecting boats the same way buildings are protected on shore. He proposes using multiple air terminals around the periphery of the boat with multiple external conductors on the outside of the boat, terminating at a grounding loop at or near the waterline, that goes all the way around the boat. I wish this article were online for all to read but they haven't put it on the BoatUS Web site yet and I wasn't able to find it anywhere else on line. The U of Florida web site on lightning say Ewen Thompson no longer works there all though they have his web site up. His new web site is http://www.marinelightning.com/consulting.htm. A synopsis of the history of lightning protection is at http://www.marinelightning.com/science.htm#Solutions and near the end of the page he goes into using multiple air terminals and side conductors.
Man Overboard
11-07-2007, 06:23 PM
In my studies, I have read a book that may offer an explanation for some of the questions raised in this post
Quote by Chandler
Lightning goes from the ground up????, What would cause the earth to spew electricity????
The following explanation is presented by Kasemir and reiterated by Lars Wåhlin in his book "ATMOSPHERIC ELECTROSTATICS" page 64
Kasemir (1950b) who believes that the mechanism involved is that of induction. For example, consider a negative charge centre in the lower portion of a cloud (see Fig. 27a.) from which a leader stroke has just reached ground. Not much charge is brought down because the negative charge in the cloud is bound on small drops or precipitation particles. On the other hand the earth's surface, which is a good conductor, can easily supply positive charge up to the cloud through the ionized channel provided by the stepped leader. When the positive charge in the return stroke reaches the cloud it will penetrate the charge centre like a giant lightning rod which causes the cloud potential to drop drastically since many field lines now are much shorter (see Fig. 27b).
A Historical perspective appears on page 12:
It was B.F.J. Schonland and his team in South Africa who discovered the different sequences of a lightning flash with the aid of a Boys camera (Fig. 6) and revealed the initial process of the stepped leader. Boys' pictures show that a bright-tipped leader works its way down from the Fig. 6 Boys’ camera photograph of cloud to ground discharge. cloud in steps. When the leader gets near ground it is met by the main return stroke which carries the main discharge current through the ionized conducting path provided by the leader. Normally the stepped leader is invisible to the naked eye and only the main stroke can be seen. The return stroke therefore, appears to start from ground explaining the saying that lightning travels from ground up.
Peter does a good job of explaining this in plain terms in post #18
Going back to Fannies original question:
Is lightning a big risk on masts during storms?
Wahlin offers an explanation that counters the rationalization that a lightning rod (or mast) attracts lightning:
page 67
Modern lightning research has proved that the function of a lightning rod is not necessarily to attract lightning and lead it to ground in order to dissipate its power. Careful studies show that large amount of corona discharges occur at the point of a lightning rod before lightning strikes. The corona discharges produce numerous ions which often develop a protective dome around structures fitted with lightning rods. A large conductive dome or sphere has a smoothing effect over protruding surfaces and will lower the electric field strength in its vicinity. Experiments by Vonnegut and Moore have shown that a conducting wire supported between two mountain tops did not get struck by lightning as often as the mountain sides. In fact, the lightning seemed to avoid the wire which can be explained by the above effect that corona must produce a large diameter ion cloud around wire. This has the effect of lowering the field strength in its vicinity.
Quote by Seer
BTW, every strike on a yacht I've heard of resulted in masthead fittings either 'disappearing' or raining to the deck in pieces. If nothing else, this indicates to me that the *highest point* proposition has some validity.
Whalins explanation explains why more boats (especially sailboats) aren’t struck by lightning. (at least those that have metal masts)
Corona discharge is of course not foolproof, boats still get struck by lightning; the lightning protection system adds some protection for boats that are struck.
A through reading of the entire text will prove worthwhile for those interested. It can be found online here:
http://www.colutron.com/products/cosmos.html
Quote by Chandler
Lightning goes from the ground up????, What would cause the earth to spew electricity????
The following explanation is presented by Kasemir and reiterated by Lars Wåhlin in his book "ATMOSPHERIC ELECTROSTATICS" page 64
Kasemir (1950b) who believes that the mechanism involved is that of induction. For example, consider a negative charge centre in the lower portion of a cloud (see Fig. 27a.) from which a leader stroke has just reached ground. Not much charge is brought down because the negative charge in the cloud is bound on small drops or precipitation particles. On the other hand the earth's surface, which is a good conductor, can easily supply positive charge up to the cloud through the ionized channel provided by the stepped leader. When the positive charge in the return stroke reaches the cloud it will penetrate the charge centre like a giant lightning rod which causes the cloud potential to drop drastically since many field lines now are much shorter (see Fig. 27b).
A Historical perspective appears on page 12:
It was B.F.J. Schonland and his team in South Africa who discovered the different sequences of a lightning flash with the aid of a Boys camera (Fig. 6) and revealed the initial process of the stepped leader. Boys' pictures show that a bright-tipped leader works its way down from the Fig. 6 Boys’ camera photograph of cloud to ground discharge. cloud in steps. When the leader gets near ground it is met by the main return stroke which carries the main discharge current through the ionized conducting path provided by the leader. Normally the stepped leader is invisible to the naked eye and only the main stroke can be seen. The return stroke therefore, appears to start from ground explaining the saying that lightning travels from ground up.
Peter does a good job of explaining this in plain terms in post #18
Going back to Fannies original question:
Is lightning a big risk on masts during storms?
Wahlin offers an explanation that counters the rationalization that a lightning rod (or mast) attracts lightning:
page 67
Modern lightning research has proved that the function of a lightning rod is not necessarily to attract lightning and lead it to ground in order to dissipate its power. Careful studies show that large amount of corona discharges occur at the point of a lightning rod before lightning strikes. The corona discharges produce numerous ions which often develop a protective dome around structures fitted with lightning rods. A large conductive dome or sphere has a smoothing effect over protruding surfaces and will lower the electric field strength in its vicinity. Experiments by Vonnegut and Moore have shown that a conducting wire supported between two mountain tops did not get struck by lightning as often as the mountain sides. In fact, the lightning seemed to avoid the wire which can be explained by the above effect that corona must produce a large diameter ion cloud around wire. This has the effect of lowering the field strength in its vicinity.
Quote by Seer
BTW, every strike on a yacht I've heard of resulted in masthead fittings either 'disappearing' or raining to the deck in pieces. If nothing else, this indicates to me that the *highest point* proposition has some validity.
Whalins explanation explains why more boats (especially sailboats) aren’t struck by lightning. (at least those that have metal masts)
Corona discharge is of course not foolproof, boats still get struck by lightning; the lightning protection system adds some protection for boats that are struck.
A through reading of the entire text will prove worthwhile for those interested. It can be found online here:
http://www.colutron.com/products/cosmos.html
Fanie
11-07-2007, 06:51 PM
Thanks everyone for your replies, some of youry went to some lengths, double thanks, I now know a little more about lighning and what to expect on a boat.
From a practical viewpoint, I am not going to worry about special wires or strips. If the lightning is going to strike the boat, there's not much you can do about it any way, and the precautionary steps may or may not work.
Since there are thousands and thousands of boats with masts in storms every single day, it seems the amount of fatal strikes are really very low, as someone suggested kinda like winning the lottery (yeah right).
Seems the thing to do when a storm is up, check the anchor, fire the kettle up, sharpen some hooks, or read multi-hull magazine ;)
From a practical viewpoint, I am not going to worry about special wires or strips. If the lightning is going to strike the boat, there's not much you can do about it any way, and the precautionary steps may or may not work.
Since there are thousands and thousands of boats with masts in storms every single day, it seems the amount of fatal strikes are really very low, as someone suggested kinda like winning the lottery (yeah right).
Seems the thing to do when a storm is up, check the anchor, fire the kettle up, sharpen some hooks, or read multi-hull magazine ;)
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