newbie lightning protection?
- Thread starter rpludwig
- Start date
If I read this correct, you are saying that because you have a grounded boat, you will reduce your chances of getting hit by lightning and it has something to do with Ben Franklin's research (cutting edge stuff from about the year 1750).
This is also an interesting read overall but I copied the first paragraph as there is a Ben Franklin reference
http://journals.ametsoc.org/doi/pdf/10.1175/1520-0450(2003)042<0984:TCFUBL>2.0.CO;2
Although I do find it very refreshing to hear someone say that grounding reduces your chances of a strike vs the common comment that grounding will attract a strike, my opinion is mostly based on the paper I just linked to which if you stretch how you interpret results, its possible that if two identical boats are sitting side by side and a strike came down exactly between them, the strike at the last moment would chose the boat with less Corona current emission of the top of the mast because it was more successful at sending a leader up to attach to the down strike - and that would be the ungrounded boat. It may also depend on what the top of the mast looks like (see the linked article). Those wire brush things may have some influence.. I really dont know. But this is likely a relatively small influence. You cant hide by making the boat look like the surroundings (those wire brush things actually add charge to the mast, not remove it). However, the best reason to provide a path to the water (surface or underwater in salt water) is that its very clear that you get less damage.
But.. this is a forum with an exchange of ideas and I wont claim I am more correct than anyone else.. been wrong in past. Maybe one of these days something will come out off the insurance industry that is more conclusive.
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Both are science!
I wonder why we don't have an epidemic of city water towers, cell towers, bridges, tall buildings, Washington Monument, Statue of Liberty
Being Blown Apart by Lightening Strikes?
What year was the Statue of Liberty built?
For further discussion by me, read my post #5 on this thread.
Jim...
PS: Keep up the "cutting edge" research! You may invent something to help my well grounded boat in the future!
Ok.. one more thing that I think is very interesting (sorry again for so off topic to the C22 folks..)
We are on the water planet and water has some properties that are really interesting. One of these is how water affects electric fields created by charge and how it affects lightning. There is a property called dielectric constant and "relative permittivity". These properties describe how much voltage drop over a distance a charge causes. We care about this for lightning since for air to conduct a lightning strike, a large electric field is required to ionize the air molecules and make them conductive. From the link below
So.. if we have some charge separated by some distance in air, this will create some voltage (and electric field). Now if you replace air by another insulative material like some sort of plastic with a relative permittivity of 2, you now get 1/2 the voltage (and 1/2 the electric field). So the higher the relative permittivity is, the lower the voltage that is produced by the charge.
In this link https://en.wikipedia.org/wiki/Relative_permittivity are listed relative permittivity for different material. https://en.wikipedia.org/wiki/Relative_permittivity
The RP for air is 1. Go down that list and look at water. Its a huge 80.1 for water at 20C!! This means that the same charge that created enough voltage to ionize air creates 80 times smaller voltage in an equivalent amount of water. Since the breakdown voltage for water and air are about the same, the charge in the lightning strike that created the field to ionize air now creates an 80 times smaller field in water - so its very unlikely that in the lightning strike scenario that water ionizes. Instead water must dissipate charge resistively.
I posted this picture already but I think this is why the ionized charge coming down through the air will still use ionized air at the water surface as the lowest impedance path to find a larger area of surface. Ionized air at the water surface apparently makes a better conductor than not ionized water.
FYI, speaking of capacitors.. interesting that if water wasnt somewhat conductive, it would make a really great dielectric for capacitors. Even Tantalum used in capacitors only has a relative permittivity of 27.. way less than water.
We are on the water planet and water has some properties that are really interesting. One of these is how water affects electric fields created by charge and how it affects lightning. There is a property called dielectric constant and "relative permittivity". These properties describe how much voltage drop over a distance a charge causes. We care about this for lightning since for air to conduct a lightning strike, a large electric field is required to ionize the air molecules and make them conductive. From the link below
Vacuum has a RP of 1 and air is slightly over 1.
So.. if we have some charge separated by some distance in air, this will create some voltage (and electric field). Now if you replace air by another insulative material like some sort of plastic with a relative permittivity of 2, you now get 1/2 the voltage (and 1/2 the electric field). So the higher the relative permittivity is, the lower the voltage that is produced by the charge.
In this link https://en.wikipedia.org/wiki/Relative_permittivity are listed relative permittivity for different material. https://en.wikipedia.org/wiki/Relative_permittivity
The RP for air is 1. Go down that list and look at water. Its a huge 80.1 for water at 20C!! This means that the same charge that created enough voltage to ionize air creates 80 times smaller voltage in an equivalent amount of water. Since the breakdown voltage for water and air are about the same, the charge in the lightning strike that created the field to ionize air now creates an 80 times smaller field in water - so its very unlikely that in the lightning strike scenario that water ionizes. Instead water must dissipate charge resistively.
I posted this picture already but I think this is why the ionized charge coming down through the air will still use ionized air at the water surface as the lowest impedance path to find a larger area of surface. Ionized air at the water surface apparently makes a better conductor than not ionized water.
FYI, speaking of capacitors.. interesting that if water wasnt somewhat conductive, it would make a really great dielectric for capacitors. Even Tantalum used in capacitors only has a relative permittivity of 27.. way less than water.
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LOL. My deck is almost completely covered when we aren't sailing. I think birds prefer to crap on fiberglass because she stays pretty clean.
edit: that doesn't read right. I meant covered with canvas, not poop.
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Remember. No matter how you spell it; "lightening", "lightning" or "lighting", it's best to get off of the water
Hey I heard that if you fly a YELLOW Flag on your mast, you will scare the birds.
I just called my Cousin Boudreaux (lives in La Rose) and told him for the biggest catch, follow the lightning strikes in da Bayou.
@woodster you are WAYYYYY behind da times, cher. We are using a car coil and battery today. Dem crank telephones are hard to find.telephone..telephone call for Mr Claude
Jim...
I think that this might be based in a debate that I am told was all the rage in the 1800's. Apparently, back then, there was great disagreement between people who believed that lightning rods should have balls on the ends & people who thought that lightning rods should have points on then ends. The rods with the balls got struck more often & therefore were thought to better attract the lightning if your plan was to run a big wire from there to ground. The pointed rods seldom got struck. The theory was that the pointed rods absorbed charge from the surrounding area gradually & therefore dissipated the potential & prevented the lighting strike from occurring in the first place. I do not know if a consensus was ever reached between the debating parties.
I think that fish & game uses that method to do counts of existing stocks. I think that you can buy electro-fishing gear in China too.
Hey, Bud, how many fish do you think are in this lake? I dunno, Lou, how 'bout we just 'lectrocute 'em and count 'em when they float to the top.
Mil Ochocientos to you.
That
Mil Ochocientos [ mil oh cho see in toes aka 1800] tequila is the top bar stock in Mexico.
But when I got back to USA, the color of USA brand is 2 shades lighter than in Mexico.
So USA 1800 has been blended, I suspect for the revenge of the Alamo.
After about 5 straight shots you will feel...
Lightning Proof
Jim...
The jumper cables from the backstay to the water seems to be the easiest thing to do. Any other practical ideas?
I know this topic is subject to ridicule by some..
I know this topic is subject to ridicule by some..
No Theory involved.
It is all Science.
Look at the top of a water tower.
You will see the miss named "Lightning Rod" as the rod much higher than the tower.
The SCIENCE is simple...
Make the Water Tower appear like the Ground around it, by putting a Faraday Cage effect over the tower.
Not eliminating the strike, but making the Tower a random target like the ground around it.
If your mast and standing rigging is properly grounded to the water around it, Your boat is like the water tower example.
Jim...
You need heavy duty big boy cables and perhaps two "Grounding Plates" hung over the side to get the grounded boat in a Cat 22. Also shore power can feed back from a near by land strike via the Ground fault line.
Jim...
This is still valid thread.
Read it from start to finish and try all the links too.
There is some joking around, but the best protection stuff is there. Read my post #5 and the PDF attachment for a good explanation of the science.
Jim...
My .02 and this could be wrong.. Some hang a chain off the side stays and this might do something but from a technical standpoint, this likely isnt that effective. For a trailer sailer, I think a four gauge cable in the configuration described below would be more effective at reducing the odds of bad stuff happening.
First.. for the weight, something like a four gauge cable is going to have both lower resistance and inductance than a chain - and likely way better for both parameters. The four gauge wire makes a much better lighting conductor and therefore is also more likely to carry the current in the strike.
Second, the mast is the tallest, most conductive structure and therefore most likely to carry the current of the strike. So you really want the "down conductor" cable to be somehow attached to the mast. This might be just wrapping the cable around the mast or actually electrically connecting it to the mast. Lighting will just arc right though the cable insulation, in my opinion, the main thing is keeping the cable from getting blown off the mast. If you think its important, you can electrically connect the cable to the mast (grounded or not), I dont think it would matter much.
As the cable goes over the side of the boat, clip it to the stays. If the stays get energized, they will also easily spark gap jump to the cable.
If you have put some plate on the bottom of your boat to dissipate lightning to the water.. well.. hopefully it doesn't blow off or cause new problems with the trailer sailor hull that wasnt designed for the plate. And you of course alway see some size given for the plate for salt water but then its just left that the plate must be much larger for fresh water.. how much larger? Well.. way larger. Im just not going to bolt some plate to the bottom of my trailer sailor with a large wire running to it.. sounds like a good way to introduce new problems, maybe even affect resale value of the boat.
The later science on lighting and water is that the water surface gets charged as the lighting strike comes down and especially in fresh water, the lightning charge will want to go the water surface. So the four gauge cable that you attached to the mast and ran close to the shrouds just needs to end near the water surface. Maybe slightly above, maybe slightly below.. Im not sure it matters. What I think would happen is that when the charge came down the cable and got near the water surface, it would jump from the cable to the water surface regardless of what you have at the end of the cable. If you are worried about "grounding", either strip the insulation off the cable if you think grounding is better, leave it on if you dont want the boat grounded. My opinion.. it doesnt make much difference at all.. do what ever makes you feel safer.
Do the same thing on both sides of the boat. You would want this all to be very fast to set up because if lightning struck while you are setting this up.. it going to leave a mark...
If in addition you want to attach a jumper cable to the backstay.. why not. Just doing this alone however means you are relying on the backstay to compete with the mast for carrying the charge. The mast is both lower resistance and inductance and will usually win.
I used to sail around a lot of lightning (high altitude in Colorado) and worried about this a lot. I would do something along the lines of what is described above if I still had the sailboat in a high lightning area.
FYI, putting the end of the cable near the water surface so that it re-sparks and then the charge travels at the water surface is pretty much covered by patents by Dr. Ewen Thomson. So.. if you do this.. just make one for yourself.
First.. for the weight, something like a four gauge cable is going to have both lower resistance and inductance than a chain - and likely way better for both parameters. The four gauge wire makes a much better lighting conductor and therefore is also more likely to carry the current in the strike.
Second, the mast is the tallest, most conductive structure and therefore most likely to carry the current of the strike. So you really want the "down conductor" cable to be somehow attached to the mast. This might be just wrapping the cable around the mast or actually electrically connecting it to the mast. Lighting will just arc right though the cable insulation, in my opinion, the main thing is keeping the cable from getting blown off the mast. If you think its important, you can electrically connect the cable to the mast (grounded or not), I dont think it would matter much.
As the cable goes over the side of the boat, clip it to the stays. If the stays get energized, they will also easily spark gap jump to the cable.
If you have put some plate on the bottom of your boat to dissipate lightning to the water.. well.. hopefully it doesn't blow off or cause new problems with the trailer sailor hull that wasnt designed for the plate. And you of course alway see some size given for the plate for salt water but then its just left that the plate must be much larger for fresh water.. how much larger? Well.. way larger. Im just not going to bolt some plate to the bottom of my trailer sailor with a large wire running to it.. sounds like a good way to introduce new problems, maybe even affect resale value of the boat.
The later science on lighting and water is that the water surface gets charged as the lighting strike comes down and especially in fresh water, the lightning charge will want to go the water surface. So the four gauge cable that you attached to the mast and ran close to the shrouds just needs to end near the water surface. Maybe slightly above, maybe slightly below.. Im not sure it matters. What I think would happen is that when the charge came down the cable and got near the water surface, it would jump from the cable to the water surface regardless of what you have at the end of the cable. If you are worried about "grounding", either strip the insulation off the cable if you think grounding is better, leave it on if you dont want the boat grounded. My opinion.. it doesnt make much difference at all.. do what ever makes you feel safer.
Do the same thing on both sides of the boat. You would want this all to be very fast to set up because if lightning struck while you are setting this up.. it going to leave a mark...
If in addition you want to attach a jumper cable to the backstay.. why not. Just doing this alone however means you are relying on the backstay to compete with the mast for carrying the charge. The mast is both lower resistance and inductance and will usually win.
I used to sail around a lot of lightning (high altitude in Colorado) and worried about this a lot. I would do something along the lines of what is described above if I still had the sailboat in a high lightning area.
FYI, putting the end of the cable near the water surface so that it re-sparks and then the charge travels at the water surface is pretty much covered by patents by Dr. Ewen Thomson. So.. if you do this.. just make one for yourself.
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All good points by Walt.
If your boat is in the water, here is a "Grounding Plate"
https://www.defender.com/product3.jsp?path=-1|344|2028694|2029019&id=28060
If you Cat 22 is on trailer in say your back yard...
Basically large tall pole, rod, and heavy wire to a good ground rod near your boat will offer protection.
This is the Science of a Faraday Cage.
That is Calder pdf... Shield shown.
Jim...
If your boat is in the water, here is a "Grounding Plate"
https://www.defender.com/product3.jsp?path=-1|344|2028694|2029019&id=28060
If you Cat 22 is on trailer in say your back yard...
Basically large tall pole, rod, and heavy wire to a good ground rod near your boat will offer protection.
This is the Science of a Faraday Cage.
That is Calder pdf... Shield shown.
Jim...