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post #21 of 41 Old 08-29-2012
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Re: My pet fear

I just sit on my friggin hands and hope real hard!


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post #22 of 41 Old 08-29-2012
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Re: My pet fear

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Originally Posted by DRFerron View Post
Ohforcryingoutloud.
it is after all quite apt that BBQBuoy should become a hatter ....

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“Life is a trick, and you get one chance to learn it.”
― Terry Pratchett.
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post #23 of 41 Old 08-30-2012
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Re: My pet fear

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Once did a calculation of the probability of a lone sailboat underneath a thunderstorm getting hit. It is considerably higher than you'd expect. Insurance statistics in FL seem to verify my calculation although I forget the actual result.
I would be interested in knowing what the ball park estimate is. That is what would determine how nervous I would get. I would assume that it is not too likely.

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post #24 of 41 Old 08-31-2012
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Re: My pet fear

Like most Catalinas out of the factory, my boat is not bonded. So far I have avoided getting caught out when lightning was present.

A friend suggested that if you find yourself caught on the water, you should attach a jumper cable (or one of those zinc fish/copper cable things) to the upper and dangle it in the water. While it would seem that this would create an easy path to water that could divert the lightning outside the boat (instead of through it), it could be argued that this increases your chance of getting struck.

What do you guys think? Does dangling a grounding cable in the water help or hurt? FYI, I sail in fresh water - does that change the answer?


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post #25 of 41 Old 08-31-2012
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Re: My pet fear

Lightning is several million volts. It can shoot sideways thru your hull and fill it with pinholes.
It is very unlikely you can do anything that will effect it. It might you feel good but there is no evidence that any bonding works (anecdotal stories aside). Certainly fuzzy hats on top of your masts might scare a seagull but to Mighty Thor they have no effect.

Faraday cage/Cone of Protection will give much protection to an overhead strike however.

The stray static charge may still fry your ic boards but that is what sextant , leadline and gps hidden in microwave are for.
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post #26 of 41 Old 08-31-2012
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Re: My pet fear

Been doing this sailing thing for over 50 years and haven't been hit at sea yet, but I have no idea why. We've been surrounded by t-storms with lightning hitting the water within several boat lengths and nothing, nada. My hair crackles and stands on end but the aloy mast, certainly the tallest thing around, doesn't get hit? A lot of times I'll start the engine in particularly bad t-storms, the thought process being an alternator might??? disturb the flow of electrons; doubtful, though.
Dockside, I've had some trouble; strikes coming through the shore power mainly.
By far the most dangerous thing about t-storms, in my opinion is the wind in the leading edge of the storm, after the "calm before the storm". Over 70 knots sometimes. So forget the lightning, it's a real pretty light show, but get your sails down (and start the engine and get that alternator turning?) before the wind hits.
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post #27 of 41 Old 08-31-2012 Thread Starter
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Re: My pet fear

It was roughly 8%. I took the average number of cloud to ground lightning strikes (yes, such a number is available on the net), divided by the area under an average storm and assumed an area affected by your mast of 250' radius.
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post #28 of 41 Old 08-31-2012
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Re: My pet fear

Quote:
Originally Posted by ParadiseParrot View Post
Lightning is several million volts. It can shoot sideways thru your hull and fill it with pinholes.
It is very unlikely you can do anything that will effect it. It might you feel good but there is no evidence that any bonding works (anecdotal stories aside).
Actually there is data both insurance and Florida Sea Grant data and the data shows that unbonded/grounded boats are at a slightly higher risk of a stirke and when stuck they suffer more damage than a lightning grounded vessel..

About the only thing insurance companies actually agree on about lightning is that a primary/secondary lightning grounding system done to a minimum of ABYC standards minimizes damage.

I recently had to install a lightning ground system on a sailboat in order for it to get insurance as it was a "noted" item on the survey. Some insurance companies are now wanting to see lightning ground paths for coverage and some are not but more and more are....


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Certainly fuzzy hats on top of your masts might scare a seagull but to Mighty Thor they have no effect.
This I agree with 100% there is no data I have found that those things make one iota's difference. The idea behind a lightning ground system is NOT to eliminate a strike, you can't do that, but to minimize damage and to help minimize side flashing that can kill those on-board.

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post #29 of 41 Old 08-31-2012
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Re: My pet fear

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Originally Posted by PalmettoSailor View Post

My boat is not bonded, and therefore presents a much higher resistance path to ground which minimizes the chance of being struck. Unfortunately, it also likely increases the likelihood of damage to the boat if I am struck.
I think if your mast is grounded it has a lower chance of getting hit. On non grounded objects it has something to do with a space field making the air around the top more conductive and/or the negative charge from the sky making the mast attract and generate a positive charge and pull the lightning in. Or something like that.

If a boat is not grounded when the lightning hits it will blow holes through the hull to connect the bottom of the mast to the water. Then your boat can sink!

Salt water is much more conductive than fresh water which is better in every way. You don't need as much surface area of metal in the water and the voltage potential between multiple water grounds will be a lot less if there are any other metal parts in the water. But you should connect all the potential grounds together so that a ground loop can't happen (I think.) If you're touching part of the ship's ground such as the wheel if it's grounded and there is water connecting your feet to the sea water I imagine that would be really bad.
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post #30 of 41 Old 09-01-2012
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Re: My pet fear

Some of you might find this interesting to read (this was on the net a while ago for free but the free link is now gone so I scanned my copy)
http://analogengineering.com/lightni...od_study_1.pdf

If you noticed that in the last 10 years or so, lightning rods went from being very sharp (Franklin) to being more rounded, it was because of the research these guys did. There are a bunch of very technical papers by the same phd guys but the one linked to above is somewhat of a summary.

These guys put sharp lightning rods near blunt lightning rods on a mountain top over a bunch of years and while there were 12 strikes to the blunt rods, not a single sharp rod was struck. All of these rods were grounded.

Also interesting that they shot a wire up into the air that induced a lightning strike. This wire was NOT grounded - strike happened when the wire was about its own length above the ground.

It’s always a stretch to make conclusion about what happens on water from what happens on land.. but if I kept a boat in a marina, I think I would put a very sharp tipped rod at the very top of the mast (i.e., a Franklin rod) and would also make sure there was some mechanism to "ground" the mast so that the Corona current mechanism at the tip of the Franklin rod was happening.

Note, Frankin rods work fine as lightning rods, the blunt tip ones just work a little better when they are competing.

Last edited by waltsn; 09-01-2012 at 07:17 AM.
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