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Old 09-07-2012, 10:20   #61
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Quote:
Originally Posted by offshorer
can somebody please recommend the best way to ground a boat?
Good luck. Lots of opinions. Btw: we came across a sailboat who's hull became a sieve from a strike. Looked like it was hit by a shotgun many times. It sank at dockside. Boatyard declared it not worth repairing. Otherwise it was in good condition.
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Old 09-07-2012, 12:20   #62
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Re: Lightning Strikes

can't provide links as it was a few years ago.
the problem i came across (in reading) is whether the grounding can provide adequate capacity for the energy of a strike.
I'm no expert, but my intuition tells me if it can't, then its back to square one.

I agree, in my case, a proper ground system would have helped in this particular event.
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Old 09-07-2012, 12:58   #63
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Re: Lightning Strikes

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Originally Posted by smaarch View Post
can't provide links as it was a few years ago.
the problem i came across (in reading) is whether the grounding can provide adequate capacity for the energy of a strike.
I'm no expert, but my intuition tells me if it can't, then its back to square one.

I agree, in my case, a proper ground system would have helped in this particular event.

problem is millions of volts, tens of thousands of degrees f in a bolt of lightening. tends to melt stuff. can stray a lot. can do wierd stuff. the 'cone of protection" works sometimes, and sometimes the bolt will go straight for the person(s) on deck or down below. crossing the equator is a good experience living with lightening. most times small leaders hit boats and everyone survives. all bets off with a main bolt smashing into your boat. we never got hit by one in 40 years of sailing but often had the static charges build up so things sizzled, sparked, and generally caused everyone to suddenly become devout. did meet lots of boats that had been hit, burnt, sunk, and blown apart from direct hits. ps. dont leave your propane tank sitting at the base of your metal mast. also beware of wooden masts, they can blast into lethal splinters.
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Old 09-07-2012, 13:08   #64
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Re: Lightning strikes

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Originally Posted by offshorer View Post
can somebody please recommend the best way to ground a boat?
Stay close inshore.

b.
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Old 09-07-2012, 15:08   #65
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Re: Lightning Strikes

best way to ground a boat--- dunno--has been done fast--8+ kts ina cal 30, has been done slow--most everyone----
i take seriously the example i was shown regarding lightning safety on a bendytoy 55 in slidell louisiana.....hit not just once but 2 times, same place, same everything--new and newly re-protected.

i think i will not be "protecting" my boat from lightning. ever. we sailed gom fora near year in and out of lightning storms--55 ft aluminum mast with antenna on top of that. no protection--we werent hit. no problem. yeah was a tad scary--but was fine.
the second strike on my friend's neighbor was really bad--the electrical wiring tothe house was burned half way from boat to house. uhoh. i wont be installing any kind of lightning prevention, thankyou--seems to be an attractor....easiest path way for the strike. wow....and a nasa engineer could not figger that out??
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Old 09-07-2012, 16:01   #66
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Re: Lightning Strikes

ps. dont leave your propane tank sitting at the base of your metal mast.

How about the backstay? If it isn't an insulated antenna, would the sparky stuff get to the bangy stuff on the taffrail, as I saw suggested in the propane thread just now?
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Old 09-07-2012, 19:27   #67
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Re: Lightning Strikes

my boat is a ketch .
my insulated main backstay comes to the hull at the companionway door...
taff is wood. teak wood. low conduction rating, as i recall.

i LOVE my formosa.
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Old 09-07-2012, 21:16   #68
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Re: Lightning Strikes

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Originally Posted by zeehag View Post
my boat is a ketch .
my insulated main backstay comes to the hull at the companionway door...
taff is wood. teak wood. low conduction rating, as i recall.

i LOVE my formosa.
Uh, do you really think those few inches (or feet) of wood are going to stop millions of volts of lightning that have already traveled through miles of air (which is a far better insulator than wood)?
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Old 10-07-2012, 01:25   #69
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Re: Lightning Strikes

Quote:
Originally Posted by zeehag View Post
my boat is a ketch .
my insulated main backstay comes to the hull at the companionway door...
taff is wood. teak wood. low conduction rating, as i recall.

i LOVE my formosa.
Zeehag low conduction is bad not good. You need to give lightning a high conduction path to ground where it will do the least damage.
Lightning traveling down the conductive back stay will not do any damage (probably), until it hits the low conduction conection where it will do a lot of damage.
Jumping from this conection to the water, seacock, or rudder could distingrate the fitting ( low conduction is high resistance which means lots of heat generated as electricity passes through it). As the fitting disintegrates the back stay is no longer connected and the mast is vulnerable.
This is why masts often fall down ( although the shrouds are more commonly involved as these provide a more direct path to ground) during a lightning strike.

A metal boat with its high conduction construction is less vulnerable to this sort of damage (but not immune). The lightning bolt can be conducted safely to the water by the metal hull. The high conduction and large surface area of the hull reduces the heating effects and therefore the damage.In boats with low conduction it is often recommended to hang large electrical cables or chain from the shrouds to provide a conductive path.

It's worth stressing again that this high conduction does not increase the chance of the boat being hit, it slightly reduces it.
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Old 10-07-2012, 07:35   #70
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Re: Lightning Strikes

after having sailed thru electrical storm after electrical storm after electrical strorm for a near year, i am not overly worried nor concerned about being hit-we all have our time--
i amnot so arrogant as to believe ANYTHING will stop a bolt of lightning from hitting me--i was near miss by lightning--one foot away from me when i was 3 yrs old. iam not gonna place my self nor my boat inthe path of harm. if i get hit is because lightning wanted to hit me. not because i am inviting it to hit me.
i was in slidell and saw the boat that was hit TWICE by lightning --belonged to a nasa engineer--lightning DOES strike twice in same exact place, as was shown by his bludi fine luck and arrogance...
because i am wooden topsides as far as pokey sticks in mother natures belly, i ammore than happy to buddy boat with someone who has a nice long aluminum 55 or taller mast..lol same with sitting the storms out-- have taller mast--park near me..lol

so---WHO ELSE HERE HAS SAILED FOR ALMOST A YEAR THRU ELECTRICAL STORMS???(wasnt my boat)...

i also place jumper cables from stay into sea..LOL..was told me by a very old salt from wooden boatville....but i only do that if it is REALLY BAD out.....i have yet to be in REALLY BAD electrical storm in my own boat---was in a sloop in gom with 55 ft aluminum mast--was very scary but we did it sans being hit.
cat was with me.
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Old 10-07-2012, 13:32   #71
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Re: Lightning Strikes

Karen,

The issue with lightning is not how to avoid getting hit -- but how to survive being hit.

The reality is that there is no known why to absolutely insure that you won't be hit. Proper bonding does reduce the chance of being hit by the most common type of lightning. However, it does increase the chance of being hit by a much rarer type of lightning. Thus, the consensus is that overall bonding reduces the chance of being hit.

Since, no matter what you do, there will always be a chance of being struck by lightning the issue becomes a question of how to survive being hit. By surviving -- I don't mean the electronics or even the boat itself survive -- I mean the most important thing of all survives -- you!

This need to insure your own survival is the real reason to properly bond the boat. Without proper bonding a lightning strike could, by chance, find a path to ground that includes your body. Admittedly, this is a very remote chance -- but it is a chance never the less. And, it is a chance that can be reduced to near zero by properly bonding the boat.

Take care,

Paul

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Old 10-07-2012, 13:42   #72
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Re: Lightning Strikes

BONDING=WIRES TO EACH THRU HULL.
bonding=sink boat in strike as all are on same string and is a conductive string---

i like my planless plan best. has worked thru many many many countless because i couldnt count'em electrical storms. and we sailed with a 55 ft long lightning rod of aluminum...LOL
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Old 10-07-2012, 13:53   #73
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Re: Lightning Strikes

OK!

My conscience is clear....

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Old 10-07-2012, 15:33   #74
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Re: Lightning Strikes

As far as lightning protection... Well it is a fickle thing, but we CAN drastically improve our odds against a total melt down, or driving the mast through the bottom of the boat!

Seatbelts don't prevent car wrecks, nor does a "Lightning Protection" System protect you from lightning. Never claimed to. Both, however, improves our odds of survival X10 or more!

If you are hit, lightning WILL then go to ground, either through the hull, catastrophically through the metal drivetrain and through hulls, or "hopefully", along the path that WE provide. This is the only given. IF YOU ARE HIT, IT WILL THEN GO TO GROUND!!! Only an idiot thinks that after hitting the mast head, the bolt would get to the mast base, and just stop there...

Statistical evidence from a very small sample, (like ourselves and the folks we know personally), is meaningless! To be valid... It has to be the scientifically accumulated evidence, compiled by thousands of the world's marine meteorologist, using tens of thousands of reports as a sample, over 20+ years... The jury has been in on this for decades!

Here's how to improve your odds exponentially:

Protecting electronics can be done "just a bit", by unplugging things, or taken to extremes, put spare hand held GPS type devices in a "Faraday cage", but this gets really iffy and of diminishing returns. I do carry a spare hand held GPS or two, away from metal, but if you take a BIG one, it is quite possible that ALL electronics will be fried. Lightning varies 1000%, and there are NO guarantees, EXCEPT that: "IF it hits your mast, it WILL then go to ground".

Setting as a goal, a lesser more reasonable level of protection... #1 You need a pointed lightning rod on the mast.

Then, GROUND THE MAST IN A DIRECT ROUTE WITH COPPER. Copper is MANY times better at conducting electricity, where as SS is quite poor. AVOID SHARP BENDS!

Searunners, like mine, are quite good in this respect. Look at my huge "00" grounding wire coming out of the mast. Being copper, its conductivity is roughly equivalent to the entire aluminum mast! Its through bolted, and just like other important connections, including batteries, I CRIMP, then "SOLDER" the crimp, for a perfect connection, and then I HEAT SHRINK the lug to wire interface. Even if the solder is melted by a direct hit, it remains crimped, and until then, the solder keeps the finely stranded tinned copper wire's end, 100% sealed!

This cable is bolted to the mast, with minimal bends, and I use "Jet Lube" copper loaded conductive grease in the interface. (NOT to be confused with "dielectric" grease, which is NON conductive). After cleaning up the squeezed out grease with mineral spirits, dry and apply 5 coats of "Liquid Lectric Tape" vinyl dip. It is now totally conductive and will stay that way (100%) for 40 years!

This huge wire goes straight through the sub floor, (through a through hull packed with silicone caulk, or a wire gland). From inside, under the cockpit, it goes through the next floor down too.

Now you are to the inside of the hull bottom. I have my 2 sq ft (min) copper plate on the side of the mini keel, and it has a curved copper piece that connects through the hull bottom with a 5/8" silicon bronze carriage bolt. On the inside "wire to bolt connection", do as on the mast connection. Same on the outside bolt pass through, except seal the hull's hole, and bed the plate, in 5200.

With grounding plates of the same sq inches, the longer narrower one is best, as linear inches of exposed EDGE is more important than size alone. It dissipates the charge better. This shape I used was a good compromise over a 1" X 288" strap down the hull! Sometimes practicality wins out over theory.

This alone is the most important part, and if you go no further, do this!!! It allows the hit to pas through the hull to "ground" along YOUR route, rather than the lightning's! Dangling a chain in the water, and such as that, is just wishful thinking!

AVOID Dyna Plates. They are not meant for dissipating lightning, and it's just possible that they'd explode. Even as a radio ground... unless you remove it at EACH haul out, and soak it in acid, the pores fill with growth. SO, it is no more surface area than it appears.

For the next level:

After this level of protection, I ran a #6 wire from ALL of the interior chainplate bolts, (except the synthetic runners'), to the copper junction plate over the main pass through bolt. This helps prevent side flashes within the boat. ABYC recommends connecting in the engine & stove too, for the same reason, but I didn't. Due to previous galvanic "issues", I isolated the grounding plate from the boat's AC AND DC systems. This solved the problems. This "isolation", btw, requires that you rubber mount your VHF antenna, as the bracket is DC -. This is very easy to do.

My SSB radio ground is connected with diodes that pass RF energy, but not DC current, but that's a different subject.

MY mast head lightning rod has the "thousand spikes" in a spiral around it, to "THEORETICALLY" bleed off ions and actually lessen the odds of a strike. Hmmm? It is solid science, used on cell phone towers all over the world, but on boats, Who knows? Since it doesn't "take the place" of the lightning rod, it IS one, and there has NEVER been evidence of it making things worse, I gave it a try. May be coincidence, but a boat RIGHT next to me has been hit, rather than me, on THREE occasions. The water or ground within 150' of us, has been hit on 5 or 6 more! Being hundreds of miles out at sea, was not as scary to us as the Chesapeake or ICW, in summer, due to the powerful thunder storms!

I can't really endorse the "fuzzy thing" that I used, may just be BS, but at least ground your mast! Remember, just like gravity: "its the law"!

"IF it hits your mast, it WILL then go to ground"...

M.
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Old 11-07-2012, 15:12   #75
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Re: Lightning strikes

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...The Art and Science of Lightning Protection by Martin A Uman published in 2008 and printed by Cambridge University Press...
Chapter 2: Lightening has both electric and magnetic characteristics, each of which can cause failure of electronic equipment. A voltage along a conductor is equal to the resistance times the amps. The amperage of a typical lightening strike is 30,000 amps. In fresh water the grounding resistance of a one square foot plate is 1500 ohms. This gives 45,000,000 volts. In saltwater the resistance is 1000 times less or 45,000 volts. The saltwater voltage can cause a spark of an inch or less, not a serious hazard according to the book (unless you have your hand on it?)
A thought of mine is if there are two grounds, say the one square foot aforementioned grounding plate and say the propeller and shaft that is connected to the engine, then a lightning strike can divide itself between the two grounds causing a surge through the distribution panel where all the ground wires meet. For the sake of discussion lets say the propeller and shaft are also one square foot area. Half the amps from the strike will choose the propeller as the ground. Now say you use a 10 gauge wire as ground for your electronics or other devices going back to the distribution panel and that the wring run is 20 feet. At one ohm per 1000 feet, the resistance will be 0.02 ohms. This times 30,000 amps gives 600 volts, enough to fry any electronic devices also in the grounding circuits through the distribution panel. There is also the heating from this current that could melt wiring in the panel. Another thing to consider is that when there is an abrupt change in current as with a lighting strike, a magnetic field is created around the wire that can induce electrical current in adjacent wiring. The quicker the amperage changes in a conductor the higher the current flow in an adjacent wiring or an electronic circuit. Because of this a lightning strike on a mast can cause voltages in electronic equipment thirty feet from the mast to reach 20 volts, enough to cause electric breakdown of transistors contained in integrated circuits even if the electrical devices are not connected to the boat’s power distribution center. A GPS sitting on a table can be destroyed for instance.
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