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Lightning and carbon masts.

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Created by ka43 > 9 months ago, 26 Mar 2008
ka43
NSW, 3091 posts
26 Mar 2008 10:26AM
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After the family had gone to bed last night I was listening to the thunder storm getting closer. Starting getting some pretty close lightning flashes and suddenly it dawned on me.
After Oz day I had put up an old 550 full carbon mast on top of my garage with a little Aussie flag on top. I then realised all my gear was stored in that same garage.
I made it outside and pulled it down quick smart.
So my question is, do you think it wouldve attracted a lightning strike and if so what would of been the consequences????

DavMen
NSW, 1508 posts
26 Mar 2008 11:02AM
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The mast would attract lightning but mostly if it was windy as well. Think of it like a skool science experiment - when you would rub an ebony rod to attract paper. The wind rushing against the carbon is almost exactly the same effect as rubbing it so it is statically charged.
What would happen to it if lightning hit - not sure - Flag pobably toast - Mast maybe explode. Depending on how it was attached to the garage - it could have set it(garage) alight.
You're a brave man taking it down during the storm.

stribo
QLD, 1628 posts
26 Mar 2008 1:59PM
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I had my tent right at the base of this broken carbon mast made flagpole.On one very stormy night i was crapping myself lightning was hitting the reef probably 500 meters away...you know the ones..the flash and instant bang..This pole was easy the highest point and was grounded in the sand. So i dunno maybe i was just lucky



When i was in QLD i used to sail the northeaster's that blew into the storm fronts.I remember on a particular day the sky was black on one half and blue on the other.Sailing on Lake Cootharabah and as the storm got closer the wind sarted to drop as it does... dogging back a lightning strike hit the water some 500 to 600 meters away from me and a few others I felt a zap through the boom dropped the sail and swam the fastest i've ever swam for shore......
So just luck??

I have seen a doco on lightning strikes and this bloke got hit holding his carbon fishing rod.It melted the resin in the rod making it look sorta like a horses tail.He had third degree burns on his hands and arms and it blew his big toe off ...

Mobydisc
NSW, 9029 posts
26 Mar 2008 5:11PM
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When I was a kid I heard about a windsurfer being struck dead by lightning on Lake Macquarie, near Newcastle.

Whats the deal with your past living conditions? Did you use to live in the bushes by the beach? If so I am envious. One my best months was camping in that crap campground at Lancelin. You may as well have been sleeping in the sandunes. Sort of looks like your past home in the picture but one bit of WA sandy scrub looks just like the next.



stribo
QLD, 1628 posts
26 Mar 2008 5:39PM
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Yeah moby lived in that spot for 2 seasons in the crusty lano van park...very robinson cruseo.Lotsa windsurfing and lotsa fun Best time of my life i reckon...free as a bird When i wasn,t there(in the off season) i was couch surfing in QLD surfing every day around the sunny coast

Mobydisc
NSW, 9029 posts
26 Mar 2008 6:52PM
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No wonder it looks familiar.

I camped under this shrubby tree as it was out of the wind and it was the only place I could get my tent in the shade. It was on the beach side, up a bit from the normal camp sites and not too far away from the dodgy amenities block. I don't think it was an actual campsite but the managers didn't mind me staying there.

Like you I really had a great time there. Mainly because of the interesting people there, mainly poms, a few Germans and a couple of Aussies. Every weekend chicks from Perth would come up to say hello.

From that photo it looks like you were down near the Lancelin town end but I could be wrong.


stribo
QLD, 1628 posts
26 Mar 2008 6:00PM
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Was about 50 meters from the windsurfing park behind what was once called surfers hollow.The gate you can see is a track(urine ally) goes through to eddies point.

sailpilot
QLD, 785 posts
27 Mar 2008 1:39AM
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While the carbon mast may have attracted a strike from the lightning your gear will have actually been protected. There's a physics phenomenon known as "faradays cage" which provides a safe cone shaped area beneath the point of a potential strike. This is also why tall buildings such as church spires put a lightning rod at the top of the structure to protect whats underneath.

ka43
NSW, 3091 posts
27 Mar 2008 12:04PM
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So you reckon ots safe to put back up??
I like to be able to walk onto the back deck and see what the wind is doing.

DavMen
NSW, 1508 posts
27 Mar 2008 12:48PM
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sailpilot said...

While the carbon mast may have attracted a strike from the lightning your gear will have actually been protected. There's a physics phenomenon known as "faradays cage" which provides a safe cone shaped area beneath the point of a potential strike. This is also why tall buildings such as church spires put a lightning rod at the top of the structure to protect whats underneath.


This is true, but it also needs to be properly earthed. Else the charge will look for its own least resistant path to earth - this is why you don't stand under trees during lightning storm. Damp gear makes for good conductivity.

Properly earthed usually means, connected (with good conductive material) to an earthrod.

slowboat
WA, 560 posts
27 Mar 2008 11:17AM
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I got zapped once at Melville- the strike was a few hundred metres away and I got a belt through the boom powerful enough to thow me. This was a long time ago when I had an Aluminium mast and boom... I dont sail near thunderstorms any more.

Any high point that has any conductivity is at risk. Basically before the lightning strikes, charge migrates to the top of the object and collects there due to the strong electrostatic field. It doesnt have to be a great conductor for this to happen. When there is enough charge there, and the local voltage gradient is high enough (pointy objects create very intense voltage gradients at the point) a corona discharge can start creating a highly conductive path through the air. If this grows to the cloud (called a leader strike) the bulk of the cloud energy can be discharged through this ionised path (the main strike which does the damage). It doesnt really care if there is a few metres of bad conductor below it- it can easily jump that gap and go over it. The point is, the air is highly conductive all the way to the point of the object. So the remaining gap below the tall object is no biggie for lightning.

By making lightning rods highly conductive, the discharge current goes through the tall object rather than around it. If it has to go around, it will jump to anything remotely conductive nearby (path of least resistance).

The reason you dont stand under trees is because they explode when hit by lightning. The resistance of the moist internals of the trees is usually low enough to contain most of the lightning current inside the tree, but high enough to cause rapid heating. The sap heats up so quickly it vapourises and the pressure becomes intense. If the tree is not strong enough to contain it, it explodes sending chunks of wood flying very very fast.

Houses can be the same... pretty scary. A mate of mine used to service TV sets and he was called to a house in Mandurah that had been struck. All the appliences were toast. But the scariest thing was the way the lightning had made its way through the plumbing in the wall cavity, and onto the metalic backing on the bathroom mirror. The mirror exploded sending shards of glass across the room- hard enough to embed themselves in the wall! Dont want to freak everyone out... there are a lot of houses and they dont often get hit, and when they do the damage isnt usually that extreme, so safety in numbers?

Cars are pretty safe places to sit in a thunderstorm. You are surrounded by connected metal so there is nowhere for an electric field to build up inside.

DavMen
NSW, 1508 posts
27 Mar 2008 3:31PM
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There you go, lots of different local variables can have many cause and effect, so the bottom line is, its probably better to let your neighbour 3 doors up attract the lightning and enjoy the view.
My company builds high voltage towers, all steel, and if the're not properly earthed the concrete foundations explode. Little different to a Sailboard mast - but the attracted energy has to go somewhere.
I remember in my youth walking along 7 mile beach Shoalhaven, quite a distance from home with nothing but scrub around, a big storm front moved in, no rain but huge black cloud heads with thunder crackling in the distance- our hair (yep had some back then) fraid out (staticaly charged) looking like we had seen ghosts - we were scared **less.

ka43
NSW, 3091 posts
27 Mar 2008 4:24PM
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Hmmmmmm, might have to leave it down now after reading your posts.
The mast was just tied to the side of my garage and was earthed into a garden bed. After reading Slowy's description its best if I keep my garages contents, including my gear, safe and snug.
Thanks everyone!!!!!!!!

decrepit
WA, 12767 posts
27 Mar 2008 8:22PM
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The scariest thing I recently read is that lightning can get diverted as much as 40Km away from the thunder cloud, can seem to come out of a clear blue sky!
I always thought I was safe until the storm was right overhead.

elmo
WA, 8868 posts
27 Mar 2008 8:26PM
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decrepit said...

The scariest thing I recently read is that lightning can get diverted as much as 40Km away from the thunder cloud, can seem to come out of a clear blue sky!
I always thought I was safe until the storm was right overhead.


Saw a doco on lightening once which said similar. They had a lady who had been hit by a bolt from a cloud over 10 miles away

Their rule of thumb was

If you can hear it fear it
If you can see it flee it

BundyBear
NSW, 325 posts
28 Mar 2008 5:15PM
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Several years ago whilst doing the marley point overnighter race in Victoria the boat i was racing on was in the creek between the two lakes and saw lightning strike a tree on the bank, it then split into two different arcs and zapped the mast of my boat and another boat boat near us.
My boat had a carbon mast with the hydrailic mast jack earthed to the steel centerboard so no one felt anything other than the heat of flash
The other boat mad an aluminium mast and had a guy sitting leaning on the sidestays with his foot on the centreboard, the guy was soaking wet as he had just pushed his boat off the bank in waist deep water, he felt a jolt and heat but was otherwise OK
the Carbon mast on my boat was OK and appaerntly is still going strong form what i heard last time i spoke to the owner



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Forums > Windsurfing   Gps and Speed talk


"Lightning and carbon masts." started by ka43