I was wondering...has anybody heard of someone being hit by lightning whilst windsurfing?

About 1992 we were sailing on some lake in from Rocky and the locals were telling a story of a guy hit by lightning. Never did verify the tale but I'm pretty sure alloy masts were the go. I know I was using a serfiac at the time.

Little known fact:

Carbon Fiber is more conductive than aluminum and fiberglass.

Yes, decrepit, I did a bit of googling on this as well, I was sure aluminium was a better conductor than carbon fibre. Didn't want to expose my ignorance though

I know aluminium is an excellent conductor of heat...

Came across a couple of manufacturing sites that said that they were using a carbon fibre/aluminium composite so you get high strength and high conductivity, from which you could assume that aluminium is a better conductor than carbon fibre.

That said, lightning normally travels on the outside of the conductor (skin effect) due to its relatively high frequency. Also high voltage does strange things... I've had to faultfind systems where something will be a dead short at 240 V but your multimeter will say that it's got several k ohms. I reckon salt water in your luff tube will act like a dead short to lightning anyway, so it doesn't matter what you use as your mast. It goes from your mast base straight through your board (which is foam/air, not very conductive eh?) so the normal rules don't really apply.

(Edit: fixed a typo so I actually have a point to the post)

Just thought of something, if carbon is such a good conductor, why is it used to make resistors????

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Originally posted by nebbian



That said, lightning normally travels on the outside of the conductor (skin effect) due to its relatively high frequency.

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Now you suprise me, thought lightning was DC, after all it's caused by a static voltage between earth and clouds.

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It goes from your mast base straight through your board (which is foam/air, not very conductive eh?) so the normal rules don't really apply.

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Yes but by the time it gets to the board, it's awfully close to the water! And how many sailors have a dry deck and mastbase?

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Now you suprise me, thought lightning was DC, after all it's caused by a static voltage between earth and clouds.

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True, true, for short values of DC... have you ever seen a photo of lightning where they move the camera sideways as it hits? More like pulsing DC, and for most intents and purposes it's more like AC than DC.

Check 'dis:
hyperphysics.phy-astr.gsu.edu/hbase/electric/lightning2.html

Also here's what a carbon fishing rod looks like after it was struck by lightning:
http://www.lightningsafety.com/nlsi_info/damage_photos.htmlbroke://
Top half of fishing pole hit by lightning. All resin has been vaporized and nothing is left but fiber that looks like cotton candy.

Yowch!!!

dont stand under trees in a thunderstorm. They explode, and the bits that fly off fast are hard and can be sharp. The moisture in the trunk heats so rapidly that it creates extreme pressure which is like an explosive. Also, the voltage gradient is much higher at the base of the object that was hit- because the ground has some resistance. So you get zapped between the legs.

I was sailing at Melville a loooong time ago when lightning struck a few hundred metres away. I got a hell of a boot from it that threw me off, and I nearly got run over by Lindsay Park (who also got a jolt). Crazy. Suspect as the lightning struck, the clouds became neutralised so that charge on the mast had nothing to support it, so it had to go somewhere fast... We were both on Serfiac aluminium masts.

Carbon is a good conductor. Carbon resistors are made from a very thin film applied to a ceramic base, with the width and length of the film varied to give various resistive values. The resistivity of the carbon itself is not changing. You can also get resistors made from a thin metal film (strangely enough called metal film resistors) manufactured in much the same way.

Lightning is DC, but because it is a short impulse, a fourier analysis will show that it can be modelled as the summation of several short duration high frequency AC components with a DC offset. Thus skin effect applies. (But don't expect to save your skin!).

High resistive values can be measured where there is a 240 volts fault, because the air gap that is giving the high resistive reading may be small enough for the 240 volts to arc accross. This is the idea of using a 'mega' to test the electrical insulation of a building as it imposes many hundreds of volts to discover any small air gaps or 'almost failed' insulation.

You do not really want to be standing too close to something tall and conductive in a lightning storm. (And not just because of the exploding trees.) As the lightning travels through the tall object and then into the ground, the current dissipates radially into the earth, creating a voltage gradient across the surface of the ground. If you are standing nearby, and your feet are too far apart, you will get electrocuted by the voltage difference between your feet. Cows standing under a tree are in a very unfortunate position, as their feet are much further apart. (This is also why if you are near some fallen power lines, and the ground is wet, you should jump away from them with your feet together. Just as you should jump out of vehicle that fallen power lines on it - don't touch the vehicle and the ground at the same time.) A car is a safe spot to sit in a lightning storm. NOT because of the rubber tires, but because the car body forms a 'Faraday cage' that keeps the inhabitants at a constant voltage, whether or not that voltage is zero volts, or many hundreds of volts above ground potential.

The worst situation for being at danger of a lightning strike is to have a tall pointy conductive object that stand well above its surroundings. (eg. carbon mast on the open water).

The build up of electrical charge in the clouds induces an opposite charge on the ground below it. The electric field of this charge concentrates on the end of the pointy object until it exceedes the air's insulation level. A 'leader' goes from the object on the ground to the cloud, which opens the flood gates (ie. ionises the air into a conductive path of plasma) for the electrical charge of the cloud to be dumped to the ground.

In a former life I use to create computer models of lightning impulses as a travelling wave to design electrical power equipment.

Hey NotWal,

The higher the frequency the more the current travels just on the outside 'skin' of the conductor. See here: en.wikipedia.org/wiki/Skin_effect

For DC the current travels through the entire conductor, including the centre. Yes electrons repel each other but the protons in the metal pull them back towards the middle, net effect is zero.

No idea how this applies to windsurfing