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Author Topic: Lightning  (Read 1516 times)

Dauninge

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Lightning
« on: February 20, 2018, 01:37:32 PM »
So last nite the 5th wheel about 50 ft to my left caught on fire and burned to the ground. No one was hurt thankfully. It was storming pretty bad and though no one knows for sure yet, the owners think it might have been a lightening strike.

My question: On the back of my MH, I have about a 20 ft pipe attached to the back ladder, then on top of that I have about a 4 ft section of PVC with my cellular antenna on top. The pipe is NOT on the ground. It is about 2 ft off the ground secured to the ladder. The cable runs from the antenna on top into my rear bay attaching to the "outside" cable connection, then the coax that runs through the coach to the inside amplifier/booster and internal antenna.

Total height above the MH is about 15 ft, so roughly 27 ft in the air. There are much taller trees around me. Should I take the pole down? Is it a lighting strike potential?
« Last Edit: February 21, 2018, 05:24:12 AM by Dauninge »
Dawn
1995 Southwind 33 (Retired)
2005 Georgie Boy Pursuit M 3500DS

jackiemac

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Re: Lightning
« Reply #1 on: February 20, 2018, 02:01:26 PM »
That's a good question, we have a wifi extender and put it down when there is bad weather but now I am wondering the same!  It is attached to the ladder though.  Be interested to see what folks think.
Jackie n Steve - Happy Scottish Travellers

2017 Heartland Sundance 288rls
2016 Dodge Ram 2500 6.4L Hemi

Travelling in US until 30th October 2018

Dauninge

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Re: Lightning
« Reply #2 on: February 20, 2018, 02:08:24 PM »
The neighbors had about the same length pole, except all metal with a plastic TV antenna on top. Theirs was attached to their ladder as well, but it went all the way down to the ground, whereas mine didn't.

It's still storming here so I went ahead and took it down anyways. Only took me about 10 minutes. (Wasn't lightening when I did it.)

I am still curious though as to whether it would have been "safe" to leave it.
Dawn
1995 Southwind 33 (Retired)
2005 Georgie Boy Pursuit M 3500DS

Molaker

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Re: Lightning
« Reply #3 on: February 20, 2018, 03:14:58 PM »
The path lightning might take is a very difficult thing to predict.  Lightning rods on structures do work to some degree, but still not 100%.  Many times, it appears that lightning did not take the path of least resistance, but often the path of least resistance is created by lightning itself as it ionizes the air.

A home I once owned was a concrete block structure with stucco veneer.  It had a masonry fireplace chimney that stood about 3 feet above the ridge of the roof.  Approx. 10 feet away I had a TV antenna mast strapped to the corner of the house and stuck into the ground, extending several feet higher than the chimney.  About 15 feet away from the house were three 30 ft + tall Chinese Elms in line, much taller than the chimney.  During a lightning storm, we took a lightning strike.  It didn't strike a tree.  It didn't strike the TV mast.  It didn't even hit the highest point of the chimney.  Instead, it hit where the chimney joined with the edge of the roof, 3 ft below the highest point of the chimney.

So, your mast may be a potential strike point, but I doubt lightning is that discriminatory.
Tom & Joyce and Ditto the "don't tell her she's a dog" Westie
U.S. Navy (Ret)
2014 Winnebago ERA 70X 24' class B Sprinter chassis

spencerpj

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Re: Lightning
« Reply #4 on: February 20, 2018, 03:35:08 PM »
I guess I'd unhook the cable in wicked storms.  I've always felt anything conductive (cable), is a source for lightening to travel down.  Sometimes just wet things are enough to pass electricity

blw2

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Re: Lightning
« Reply #5 on: February 20, 2018, 04:11:36 PM »
Two stories that come together to make a point....

Lightning will travel down even small wires if it gets to them.  Back in the mid 90's I saw a presentation by Bruce Fisher, a guy that had worked as a scientist of some sort with NASA doing lightning research...flying a F-106 into storms directed by ground radar trying to get struck.
https://www.f-106deltadart.com/nasa_lightning_research.htm

In his slide show, I remember a photo he had of a small GA aircraft, I forget if it was a cessna or piper maybe.... anyway the lightning had entered a wing tip and traveled down the nav light wiring that was just inside of the leading edge, all the way across to the opposite wing tip where it exited out the other nav light.
Now, remember the magnetism that comes with electricity flowing through a wire?
remember the right hand rule?
Well that magnetism completely imploded the leading edge of that wing.  Instead of the nice rounded "nose" it was completely inverted into a cup shape.
the plan made a safe landing...hence the photograph of it!

second story.... when I was a teenager, my dad and I were in his boat fishing off shore.  It was a small flying bridge boat with a cabin so we were inside shelter.  Lightning struck.....flashbang....I felt a zing, and everything shut down.  Now power, no starting the engine, no lights....nothing.  But no apparent damage so we figured it hit the water nearby? 
So we threw out the anchor and resumed fishing once the rain passed.  later a big charter headboat came by and towed us in.  Once back at the dock, someone pointed out the top of the CB radio antenna was black.  Actually it was the top of the lower segment.  The top half was gone!  So what happened was lightning hit that antenna, and through that wire got into everything that was turned on.  Anything that was switched off was fine.  Anything on was melted.  The windshield wiper that was on...melted.  the one that was off, ok.  every light bulb, electronic ignition module, etc... that was on...melted.  Literally goo.

Anyway, My point is this.  If lightning does hit that antenna, it will almost certainly get into your RV and will likely travel all around through it.  I'd suggest grounding that antenna.
Brad (DW + 3 kids)
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'06 Silverado
'05 Rockwood Freedom 1910 (5-1/2 years)
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HappyWanderer

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Re: Lightning
« Reply #6 on: February 20, 2018, 04:41:22 PM »
Grounding an antenna isn't as simple as it sounds, and is probably more dangerous if not done properly. I've spent several hundred dollars to make sure my home amateur radio antennas are properly grounded and bonded.

If you're really concerned about lightning, dropping the antenna is a better choice.
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Dauninge

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Re: Lightning
« Reply #7 on: February 20, 2018, 04:59:09 PM »
I took it down. I wasn't prepared to take the risk. There was no way it was properly grounded, if at all. (It was not touching the ground and no additional ground wire connected.) It's not going back up either. At least not in that configuration.

It was amazing how fast that RV burned to nothing. Less than 45 minutes and it was gone. I'm really glad that they made it out OK and that my MH didn't go with it. Most important is that everyone is OK.

I thank everyone for the replies.
Dawn
1995 Southwind 33 (Retired)
2005 Georgie Boy Pursuit M 3500DS

johnhicks

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Re: Lightning
« Reply #8 on: February 20, 2018, 08:44:12 PM »
Ground the metal pole to a four-foot ground spike or take it down.

HappyWanderer

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Re: Lightning
« Reply #9 on: February 20, 2018, 10:54:01 PM »
Ground the metal pole to a four-foot ground spike or take it down.

Grounding in such a manner is not appropriate, for many reasons. Without getting into a prolonged technical discussion on grounding and bonding (of which many can easily be found on electrical and communications forums), just don't do it.
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John From Detroit

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Re: Lightning
« Reply #10 on: February 21, 2018, 07:58:48 AM »
First. when it comes to lightening you have two things that damage. a DIRECT HIT and a NEAR MISS  I've had the "pleasure" of both. A Strike abut 200 yards from where I was parked (Thankfully I am somewhat protected so that only damaged some MOV's slightly) and a Direct on a Radio Tower I was using (Professionally) Believe it or not the tower survived save for a converter (Just like in your RV) that was the only thing totaled

Grounding the mast will help. Code is a 10 foot pipe but 10 one foot tent stakes is good too and a whole lot easier to insert and remove.. Use heavy wire.. I use 10 ga but you really should use heavier. and no kinks  gentle sweeping curves yes. kinks no.
Nothing adds excitement like something that is none of your business
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HappyWanderer

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Re: Lightning
« Reply #11 on: February 21, 2018, 08:13:27 AM »
Guys, please stop with the bad advice.

The NEC is very clear on this topic, along with recognized industry standards for lightning protection.

Both suggestions posted are incorrect in that they promote isolated grounds, which can be lethal to humans and equipment.
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blw2

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Re: Lightning
« Reply #12 on: February 21, 2018, 08:43:24 AM »
OK, enlighten us please.  If you were to be using such an antenna, how would you do it?
I'm guessing your an amateur radio operator.  Do you ever set up a rig while RVing?  How do you ground it?

Of course pulling it down is the "easy answer".... and that works maybe a bit better for something of occasional use.  For checking messages once a day....check the wx, put up the antenna, do your business, and pull it down.
but for something like TV or cell phone, that may be used more frequently, used into the evening, etc... pulling it down every time aint so practical.  Especially considering storms might sneak up on you when you are away.... or while sleeping

So I figure an antenna that's up is of course going to be a likely point for lightning to strike.
if it does strike, lightning WILL travel down the wire.
It's either going to travel all through the RV, OR try to jump out to ground if that's more direct and easier.... actually I'd imagine that most of the energy would jump regardless.... it's probably only a partial of the strike that would travel through a small wire...but still....
having the wire grounded through a coax ground block, like you'd use for a sticks and bricks application makes sense to me....
sure having it grounded to the electrical grid's ground  or a proper ground array makes sense
but isn't it better than the alternative to give a more likely place for the energy to jump ship...such as grounding the cable to the mast which at least gives it a direct path to earth, even if that contact is only the mast touching the ground....or the mast within say an inch of the ground?  Seems to me that this would be an easier and more direct  path than it networking through the chassis and all that wiring to find a way out past the tires or through the shore power cable...
Brad (DW + 3 kids)
í13 Thor Chateau 31L Class C on Ford E-450
'06 Silverado
'05 Rockwood Freedom 1910 (5-1/2 years)
former tent campers

Dauninge

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Re: Lightning
« Reply #13 on: February 21, 2018, 10:23:25 AM »
I think I am just going to mount the antenna itself to the ladder using the 4 ft PVC that I have. I don't need to have it so high up in the air. That way I can take it down quickly if needed. If I were going to use the previous setup, with the metal pipe, I would run a ground wire as John advised. I would run a ground from the mast as well as a ground from the ground coax connector at the RV both to a proper ground pole. (Well, as proper as I would be able to in the RV Park)

I realized as the dog and I were in the car a safe distance away, that I really need to think about being able to break camp in a timely fashion. I have double slides and an extend-a-stay hooked up.
I wouldn't move the MH at all with the slides extended. I figure best case scenario I could have had the MH ready to move in minimum 20 minutes, most likely 30.

It would have been too late by then. Within 10 minutes of the fire starting the flames were already raging and embers dancing through the air. The fire dept. arrived in just under 20 minutes. (They are a volunteer FD, so considering they had to get out of bed at 11:40 at night, get dressed, drive to the FD, suit up and drive here, I thought that was pretty good time.) My MH is fully insured, so I just grabbed the dog and my phone, jumped in the car, and got a safe distance away. Made sure the neighbors had made it out and dialed 911 on the way out.


 
Dawn
1995 Southwind 33 (Retired)
2005 Georgie Boy Pursuit M 3500DS

johnhicks

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Re: Lightning
« Reply #14 on: February 21, 2018, 10:35:25 AM »
  You may not need near that height unless there are obstructions.

HappyWanderer

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Re: Lightning
« Reply #15 on: February 21, 2018, 11:25:39 AM »
OK, enlighten us please.  If you were to be using such an antenna, how would you do it?
I'm guessing your an amateur radio operator.  Do you ever set up a rig while RVing?  How do you ground it?

While I donít attempt to comply with NEC 810 and Motorola R56, I do try to comply with the best practices of the standards. I carry a grounding kit with some #6 and #12 wire, a ground buss bar and assorted clamps, which all fit into a canvas bag. I bring this same stuff to Field Day.

The radio and coax shields get connected to the bus bar, then I go looking for a ground. One can be usually found at the pedestal, a cable TV connection or occasionally a copper water pipe on the site.

If severe weather is forecast, Iíll disconnect the antennas and pull the coax out of the RV. Iíve also been known to drop the antennas and disconnect from the power pedestal if things look really bad. For the most part though, I donít worry much about lightning.
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Lou Schneider

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Re: Lightning
« Reply #16 on: February 21, 2018, 01:05:30 PM »
When we installed solid state FM broadcast transmitters, the manufacturer had several recommendations on how to minimize lightning damage to the equipment above and beyond the NEC requirements.

First is to provide a direct, straight path for lightning to go from the tower to ground.  Lightning prefers to travel in a straight line, so if there's a direct path to ground it will prefer to take that route.  If you're going to have a ground rod, put it directly under the antenna, not on the other side of the RV.

Next make it harder for the lightning to travel into the building or RV.  Make the coax exit the tower at a right angle then pass it through a ferrite choke.  If the coax is flexible enough, wrap it in a loop so it passes through the ferrite twice.  This won't eliminate the lightning getting in, but it will slow it down a bunch.

If you don't have ferrite chokes, loop the incoming coax several times to form a coil.  This will also encourage the lightning to take the straight path to ground instead of through the equipment.

Finally, minimize ground paths across the building.  By this I mean having the tower and coax enter on one side and have the power line ground on the other side.  Voltage coming down the antenna line will enter the building on the antenna side, then travel across to the power line ground on the opposite side.  If the tower coax and the electrical entry are on the same side and ideally connected to a single grounding point less voltage will flow across the room and anything that's in it.

If you're interested, here are couple of brief articles showing how it's done in professional installations:

http://www.radioworld.com/tech-and-gear/0003/field-service-tips-grounding/340684

http://www.tvtechnology.com/opinions/0004/power-surges--part-two/276965
« Last Edit: February 21, 2018, 01:37:29 PM by Lou Schneider »

Oldgator73

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Re: Lightning
« Reply #17 on: February 21, 2018, 03:12:46 PM »
Way back when, 1969-1974, I worked as a Class B operator on a line crew. When we set poles a copper wire was run down from the top which was connected to a lightening arrester. A lightning rod was pounded into the ground next to the pole. I think they were ten foot sections and we used maybe 2 or3 sections.
Retired Air Force
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skydivemark

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Re: Lightning
« Reply #18 on: February 22, 2018, 07:26:50 AM »
Two stories that come together to make a point....

Lightning will travel down even small wires if it gets to them.  Back in the mid 90's I saw a presentation by Bruce Fisher, a guy that had worked as a scientist of some sort with NASA doing lightning research...flying a F-106 into storms directed by ground radar trying to get struck.
https://www.f-106deltadart.com/nasa_lightning_research.htm

In his slide show, I remember a photo he had of a small GA aircraft, I forget if it was a cessna or piper maybe.... anyway the lightning had entered a wing tip and traveled down the nav light wiring that was just inside of the leading edge, all the way across to the opposite wing tip where it exited out the other nav light.
Now, remember the magnetism that comes with electricity flowing through a wire?
remember the right hand rule?
Well that magnetism completely imploded the leading edge of that wing.  Instead of the nice rounded "nose" it was completely inverted into a cup shape.
the plan made a safe landing...hence the photograph of it!

second story.... when I was a teenager, my dad and I were in his boat fishing off shore.  It was a small flying bridge boat with a cabin so we were inside shelter.  Lightning struck.....flashbang....I felt a zing, and everything shut down.  Now power, no starting the engine, no lights....nothing.  But no apparent damage so we figured it hit the water nearby? 
So we threw out the anchor and resumed fishing once the rain passed.  later a big charter headboat came by and towed us in.  Once back at the dock, someone pointed out the top of the CB radio antenna was black.  Actually it was the top of the lower segment.  The top half was gone!  So what happened was lightning hit that antenna, and through that wire got into everything that was turned on.  Anything that was switched off was fine.  Anything on was melted.  The windshield wiper that was on...melted.  the one that was off, ok.  every light bulb, electronic ignition module, etc... that was on...melted.  Literally goo.

Anyway, My point is this.  If lightning does hit that antenna, it will almost certainly get into your RV and will likely travel all around through it.  I'd suggest grounding that antenna.

Lightning sure does weird things; Once our dryer quit heating. I pulled it out to check it and found a lightning strike going from the dryer to the washer. No idea where it came in the house but the dryer element was fried.
2015 Thor Four Winds 31L
Clermont, FL

masterdrago

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Re: Lightning
« Reply #19 on: March 10, 2018, 09:30:56 AM »
When I worked in the A/C repair and Appliance business, I saw where a strike hit a tree a few feet from a house corner, jumped to a condensing unit cracking the concrete and moving the unit 8", moving somehow across the house jumping off a turn-off vlv under a commode, blew a 2" hole in the floor, and jump off a 1/4" water line to the refrigerator on the other side of the house. I think it ignored all other paths to grounded stuff. Found this to be a good link to monitor when having antennas up. http://en.blitzortung.org/live_dynamic_maps.php
Kenneth & Joy Drake
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jackiemac

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Re: Lightning
« Reply #20 on: March 10, 2018, 10:53:06 AM »
When I worked in the A/C repair and Appliance business, I saw where a strike hit a tree a few feet from a house corner, jumped to a condensing unit cracking the concrete and moving the unit 8", moving somehow across the house jumping off a turn-off vlv under a commode, blew a 2" hole in the floor, and jump off a 1/4" water line to the refrigerator on the other side of the house. I think it ignored all other paths to grounded stuff. Found this to be a good link to monitor when having antennas up. http://en.blitzortung.org/live_dynamic_maps.php
I have bookmarked that, it should come in handy. Although quite often where we seem to be is where the storm is  ::)
Jackie n Steve - Happy Scottish Travellers

2017 Heartland Sundance 288rls
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Sun2Retire

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Re: Lightning
« Reply #21 on: March 10, 2018, 11:47:29 AM »
I think it ignored all other paths to grounded stuff.

Yup. It's a common misconception that the tires of your car offer protection. But in reality that lightning bolt just traveled anywhere from one to several miles through no other conductor than the air; that last 6" of space offered by the tires isn't going to do much good. It's the Farady Cage principle that allows the charge to travel around the occupants through the frame leaving them unharmed. Same reason airplanes can be hit all the time without hurting anyone. The most damage to an airplane is typically caused when the charge leaves and continues on its way.

Found this to be a good link to monitor when having antennas up. http://en.blitzortung.org/live_dynamic_maps.php

Wow, what a great site! Bookmarked
Scott
Fulltiming in a 2005 Newmar Dutch Star 3810, Spartan, Cat C7 350
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Rene T

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Re: Lightning
« Reply #22 on: March 10, 2018, 11:59:49 AM »
I remember years ago when I was on the Fire Dept. and we responded to a grass fire and a woods fire. We arrived at the scene and found that lightning had hit a huge pine tree and split it down the middle. It then went about 200' in the ground creating a trench about 3' wide and 2' deep. There were boulders weighing about 200 lbs. thrown off to the side. It then went out into the open field starting multiple grass fires. I respect lightning after seeing that.
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John From Detroit

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Re: Lightning
« Reply #23 on: March 10, 2018, 05:39:55 PM »
Regarding the "Tires will protect you"  I always laugh when I read that.. Then I shake my head in disbelief.

you have a bolt of electricity that is going to jump an air gap thousands of feet in length. What's a few more inches????? (Nothing)

NOTE: IF I RECALL correctly,,  Lightning does not strike the earth, it strikes the clouds.  that is the direction the current flows. no matter how we normally picture it. Still  When it starts flying, best place to be is ELSEWHERE.
Nothing adds excitement like something that is none of your business
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Sun2Retire

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Re: Lightning
« Reply #24 on: March 10, 2018, 05:52:51 PM »
NOTE: IF I RECALL correctly,,  Lightning does not strike the earth, it strikes the clouds.  that is the direction the current flows. no matter how we normally picture it.

 :))

"Does lightning strike from the sky down, or the ground up? The answer is both. Cloud-to-ground lightning comes from the sky down, but the part you see comes from the ground up. A typical cloud-to-ground flash lowers a path of negative electricity (that we cannot see) towards the ground in a series of spurts. Objects on the ground generally have a positive charge. Since opposites attract, an upward streamer is sent out from the object about to be struck. When these two paths meet, a return stroke zips back up to the sky. It is the return stroke that produces the visible flash, but it all happens so fast - in about one-millionth of a second - so the human eye doesn't see the actual formation of the stroke."

I believe this is why, if you are in the immediate vicinity of a spot about to be struck, you may get a few second warning as the charge starts to build. People have reported their hair standing on end, tingling, etc. Running back in a building (if close), running and lying down in a ditch or at least getting flat on the ground is the recommended action
Scott
Fulltiming in a 2005 Newmar Dutch Star 3810, Spartan, Cat C7 350
Eezrv TPMS, 970W Solar, Tri-Metric Battery monitor
2002 Dodge RAM 1500 Quad Cab toad
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Molaker

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Re: Lightning
« Reply #25 on: March 10, 2018, 07:25:03 PM »
.....I believe this is why, if you are in the immediate vicinity of a spot about to be struck, you may get a few second warning as the charge starts to build. People have reported their hair standing on end, tingling, etc. Running back in a building (if close), running and lying down in a ditch or at least getting flat on the ground is the recommended action
I thought you were supposed to bend over and put your head between your legs.
Tom & Joyce and Ditto the "don't tell her she's a dog" Westie
U.S. Navy (Ret)
2014 Winnebago ERA 70X 24' class B Sprinter chassis

Sun2Retire

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Re: Lightning
« Reply #26 on: March 10, 2018, 08:02:27 PM »
I thought you were supposed to bend over and put your head between your legs.

Only if there isn't a ditch, house or car really, really close
Scott
Fulltiming in a 2005 Newmar Dutch Star 3810, Spartan, Cat C7 350
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2002 Dodge RAM 1500 Quad Cab toad
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jackiemac

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Re: Lightning
« Reply #27 on: March 11, 2018, 06:50:11 AM »
:))

"Does lightning strike from the sky down, or the ground up? The answer is both. Cloud-to-ground lightning comes from the sky down, but the part you see comes from the ground up. A typical cloud-to-ground flash lowers a path of negative electricity (that we cannot see) towards the ground in a series of spurts. Objects on the ground generally have a positive charge. Since opposites attract, an upward streamer is sent out from the object about to be struck. When these two paths meet, a return stroke zips back up to the sky. It is the return stroke that produces the visible flash, but it all happens so fast - in about one-millionth of a second - so the human eye doesn't see the actual formation of the stroke."

I believe this is why, if you are in the immediate vicinity of a spot about to be struck, you may get a few second warning as the charge starts to build. People have reported their hair standing on end, tingling, etc. Running back in a building (if close), running and lying down in a ditch or at least getting flat on the ground is the recommended action

Here are a couple of images I found on the web....
Jackie n Steve - Happy Scottish Travellers

2017 Heartland Sundance 288rls
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Lou Schneider

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Re: Lightning
« Reply #28 on: March 11, 2018, 12:17:04 PM »
In the 1980s I was in charge of a 50,000 watt AM transmitter site.  It was in the middle of farmland with (4) 500 ft. towers that would occasionally be hit by lightning, causing damage and loss of airtime.

When we installed a new transmitter we also added lightning eliminators that looked like large toilet brushes to the top of each tower - lots of pointy bits to dissipate the upward streamer before it had a chance to form.

A few weeks later I was called out to the site because the transmitter had kicked on and off the air several times.  When I got there I asked the farmer who owned the adjacent land if anything unusual had occurred.

He pointed to ground strikes outside of our property on all 4 sides of the towers and said it was the strangest thing he had ever seen.  A thundercloud had formed overhead but instead of hitting the towers, the lightning struck the surrounding land.  The resulting surges were enough to trip the overload circuits in the transmitter, but each time it returned to the air on it's own and there was no damage.
« Last Edit: March 11, 2018, 12:23:07 PM by Lou Schneider »

Sun2Retire

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Re: Lightning
« Reply #29 on: March 11, 2018, 12:33:05 PM »
lightning eliminators that looked like large toilet brushes to the top of each tower - lots of pointy bits to dissipate the upward streamer before it had a chance to form.

Interesting. Wondering if that explains the sometimes funny shaped lightning rod you'll see on old farmhouses.

Large airplanes use identical technology - they're called static wicks. Roughly 10" in length, they can be seen along the trailing edge of the wings and empennage. Dissipates the charge on the aircraft and sometimes also offers an "exit path" if a strike does occurs
Scott
Fulltiming in a 2005 Newmar Dutch Star 3810, Spartan, Cat C7 350
Eezrv TPMS, 970W Solar, Tri-Metric Battery monitor
2002 Dodge RAM 1500 Quad Cab toad
Stowmaster towbar & Brakemaster toad braking system