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SailVicEC 07-04-2004 11:45 PM

Lightening strike
 
Just read in anpother post that Jeff had to replace all his electrnics due to a lightening strike. If you read this Jeff, was wondering if there was something you were going to do to your boat to try an mitigate against the frying of your electronics by lightening again? Is there anything that can be done or is it just something that happens?

Given how expensive electronics can get and the problems that losing all your electronics can cause what is the best way to prevent this eventuality?

Sasha_V 07-05-2004 12:37 AM

Lightening strike
 
My understanding is that he plans to install the new electronics and then sacrifice a small furry animal while muttering arcane rituals to peculiar deities. (actully, I think most of the deities I have met have been rather peculiar in one way or another).

Sources report that he plans to perform these rites on the pullpit of his boat, on the third full moon of the Aztec lunar calender while clad only in cling-film, two band-aides and half a bunny skin.

The breed, gender and political alignment of the small furry animal have yet to be announced.
Tickets go on sale next Tuesday.


:)


Sasha

paulk 07-05-2004 05:29 AM

Lightening strike
 
Are the places reserved, or is it festival seating? While the best remedy for seasickness -- sleeping under an apple tree -- can also be applied here, the tree may also get hit by lightning.

If you''re anywhere but in a cave, you could get hit by lightning. There isn''t much you can do about it, and lightning is such a powerful force that it can fry stuff that isn''t actually even wired together, but is justt nearby. There can be so much voltage that it actually seems to conduct through wooden masts, or it superheats the moisture and the steam blows things apart. Cruising World had a article on it a while ago, with some helpful ideas and suggestions, none of which was foolproof.

I remember reading at one point - perhaps in Woodenboat -- that to avoid radio interference, wires powering electronic components should be twisted in a loop to negate some field or another before they were connected. Apparently in a lightning strike, the current that comes through the wire is so inclredble that the loop turns into the equivalent of a starter coil, boosting the current and thouroughly frying everything before tthe wire vaporizes. Then the discussion expanded as to what the best shape for the dissapating plate on the outside of the hull was, and how heavy-gauge tthe connecttion should be.

If I have to be out in a thunderstrom, I try to not hang onto the stays or shrouds.

Jeff_H 07-05-2004 07:25 AM

Lightening strike
 
Now this is a funny thread.....I think that I will sacrific a stuffed animal or two since I would not harm an otherwise living creature.

Seriously, there is not much you can do to prevent the agony of fried instruments. When lightning strikes a boat there is enormous induced current and that completely overwelms any defenses that can be applied. The damage has been amazing to me. Many of the inline fuses got so hot that not only did the metal in the fuse melt down, but the glass melted as well. Pieces of the bilge pump switch (which was turned off at the time) was blown across the cabin. One of the two batteries were fried as was the three way switch which was turned also off. Light bulbs on the mast were actually welded into the light fixtures.

The boat itself sustained not visible damage. She was out of the water for a bottom job at the time. She has a keel stepped mast that sits on an aluminum beam that is bolted to one of the 25mm keel bolts. I have conjectured that the lightning simply was conducted straight through the mast and out through the keel but there is no way to know. Typical of southern hemishere boats,none of the thru hulls are bonded and so they sustained no damage. (I have heard of thru-hulls blasting out chunks of hull in a lighting strike sinking a boat rather quickly).

The current data, albeit somewhat anecdotal suggests that the Ion Diffusion brushes actually seem to attract lightning so I don''t know of a way to protect my boat from a strike.

As of last night all of the systems are back in and seem to be working, albeit in need of calibration, so I am heading out cruising in a few minutes.

Regards,
Jeff

SailVicEC 07-05-2004 02:55 PM

Lightening strike
 
Good to read that you are back out there Jeff and thanks for the info and for the laugh Sasha et al :-)

How often does this happen on the water? Being that a boat''s mast is often the tallest thing around and running from storms is not always possible or practical. Does having a carbon fiber mast help to not get zapped vs an Al mast?


Sailmc 07-07-2004 06:06 AM

Lightening strike
 
I have never had a direct strike but have lost electronics three times due to induced surges from near stikes over the last 12 years.

Irwin32 08-01-2004 06:30 PM

Lightening strike
 
There is very little one can do to protect against a lightening strike. Insurance companies plan on one boat in a thousand being hit. Your odds are good.

Your mast being the highest thing around is, from my understanding, somewhat misleading. Lightning does not look for the highest thing - it looks for the easiest path to ground. This means that when a cloud is ready to discharge it will do so. If that happens 200 feet away from your 50 foot mast, it won''t seek out your mast, but go straight in to the water.

In Lake Michigan we have had the Mac race run for over 100 years through all types of weather. T storms are very common in our area and are a common part of the race.. No one has ever died in a Mac race from any cause. In addition, we run a 200 mile alternative race at the same time with the same results. That means almost 400 boats out on the lake each year going through whatever weather is thrown at them, and no one has died from anything - including lightning.

I agree, it is frightening and I don ''t like being out in it. But I just tell myself that the odds are bigtime for me. I am safer cruising on my boat, than vacationing in my car.

Jeff_H 08-01-2004 07:03 PM

Lightening strike
 
What makes you think that no one has died in the Mac? I seem to recall quite a few fatalities over the years, mostly drownings, but I seem to recall a fatal multihull capsize, and an ill timed jibe. I may be remembering this incorrectly but that is my recollection.

Jeff

Billpjr 08-02-2004 11:55 AM

Lightening strike
 
Here''s what I have wittnessed over the years in Florida...from 10 yrs liveaboard/cruise and 45+ yrs on the water.

Bonded or not, grounded or not, a feeder strike can or will jump around to metal and electrical components. It jumps by people sitting below and connects with metal. It hits unbonded thru hulls, etc the same as bonded ones. The difference is in the strength of the lightning bolt whether it jumps or follows a path. No wire or system is capable of carrying the charge from a large feeder or main bolt strike. It is impossible. Just the pressure and heat from a main bolt will blow
apart or melt the boat.

A lessor strike (feeder) can burn perfectly symetrical holes through glass hulls where bolts penetrate. They look like a drill made the hole. It melts aluminum masts, sails and gear. It finds dry areas in the lamination and blows the glass apart (appeared to me it superheated the air pockets). I examined a Cal 25 that had a 3''x 4'' section of the hull lamination blown off...popped about 50% of the lamination off and left the other half. The keel bolts stretched 6-8" and the keel lowered. Two people dead and the boat sunk.

On the otherhand I saw a boat completely comsumed by "St Elmos Fire" and nothing happened. The whole boat glowed from stem to stern but nothing damaged.

Put a hand held miliampmeter on an aluminum mast. Every time the wind gusts you will see voltage. Small, but this static charge is what attracts strikes. Make a path big enough for the charge to bleed quickly and it will reduce strikes. I think rain water running off the boat helps bleed the charge in a big way.

Also, two weeks ago a long time friend of mine lost his wife to lightning. It blew her in half while she was holding their son in her arms to keep him warm. He is in critical condition.

Irwin32 08-03-2004 04:26 PM

Lightening strike
 
Jeff - about the Mac safety record. I sail in S. Lake Mich, so I read and pick up info about our area. I cannot remember the source of my info, but your question promted me to do some searching and I have not been able to find anything that contradicts what I said.

The tri you refer to was from either last year or the year before. The entire crew was rescued.

If someone has some reliable info about my statement, I would like to know as I believed it to be reliable.


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