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Old 11-08-2014, 10:25   #31
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Re: Lightning

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Originally Posted by belizesailor View Post
Yes, similar idea, but something that won't corrode. Run power via single large gauge +/- cables to bus bars inside to which gear attaches then you just need a dual pole breaker for the power and a few quick disconnects for antennas...to make it quick and easy.
The picture I posted was supposed to be 316... Agreed as to exactly how I pictured the inside bus, data, antenna stuff...

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My mental picture for this statement is a guy in a lazyboy with a beer watching televisionů

Mark
Hey now!

What would I do with all of the cylinders, steel shot bags, and the like???

Funny story=Client asked for cheap way to perform a tilting cycle test on a chair in his factory in China... I assembled the cheapest down and dirty list of components for him, probably about $150...

Asked a couple months later how his new "test setup" was working... He replied...

"We didn't do it... It was cheaper to pay a big fat Chinaman to sit in the chair and rock back in the chair, 10 hours a day for 2 weeks..."


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Originally Posted by onestepcsy37 View Post
Thanks for the explanation. Now I know that I am neither bonded OR grounded. This boat hasn't been bonded in its 35 year life so I think I will just keep it that way. The bottom of the mast sits on a rather substantial base, about 3 feet from the 8000 lb lead keel, which is completely encapsulated in fiberglass. I could run a bigass cable or grounding strap between the two. Something to think about.
Mannn.. Therein lies the problem... Are you "more prone" to attracting a strike with a grounded stick... But if it isn't and you get hit... Your "bonded" stuff is the easiest path to ground...
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Old 12-08-2014, 10:43   #32
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Re: Lightning

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Originally Posted by onestepcsy37 View Post
Thanks for the explanation. Now I know that I am neither bonded OR grounded. This boat hasn't been bonded in its 35 year life so I think I will just keep it that way. The bottom of the mast sits on a rather substantial base, about 3 feet from the 8000 lb lead keel, which is completely encapsulated in fiberglass. I could run a bigass cable or grounding strap between the two. Something to think about.
*DO NOT* connect your mast to your encapsulated ballast! That's one of the worst of all possible scenarios. A direct strike could blow holes in your ballast skin. If you want to ground the mast to the water, connect the base of the mast to a ground plate. The ground plate should be mounted on the exterior of the hull as close as practical to the base of the mast. Connect the base of the mast to the ground plate with at least #4 AWG (larger if practical). Use as straight a run for the cable as practical. No sharp bends. Ground plate should be at least 1 Sq-Ft in area and about 1/4" thick. A longer strip is better than a square plate, again as practical. These are the recommendations of most authorities on the subject. No guarantees, and won't change your chances of being hit (much). The point is to provide a path for the bulk of the energy to the water. If you don't provide a path, the strike will likely provide its own, through the hull.

Lightning grounding is all about reducing the chances of catastrophic damage (as in sinking the boat). It is not about protecting the electronics or preventing strikes. There are some things you can do to help your electronics chances of survival. Mark mentioned some. Disconnecting a unit of electronics from *every* cable/wire is also helpful, but usually not practical. Placing electronics in a Faraday box is also good, but often impractical. There is *nothing* you can do to *prevent* a strike if you are in a lightning prone area. All the isolated, one-off accounts of strikes, near strikes, or non-strikes mean nothing. Statistically, lightning will do what it will do. There are too many unknown variables to predict its path.
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Old 12-08-2014, 11:25   #33
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Re: Lightning

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That my friend is a SLICK IDEA!

I'm a test lab guy for furniture, and we see flipper door cabinets for office panel systems all of the time... Door lifts and slides on top of the cabinet. Mount one of these in a nav station, mount your electronics in it... Make a couple of disconnect plugs for the whole box... Flashee come... shut the door... Pull the plugs...

Plus... Now you have a locking panel to cover your stuff....
One enhancement needed...some sort of indicator that the antennas are disconnected. Recently on the hard with antennas disconnected. Splashed today. Tried to make a call on the VHF....doh!
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Old 12-08-2014, 12:06   #34
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Re: Lightning

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There are too many unknown variables to predict its path.
What from I have seen in strikes on aircraft, this is true
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Old 12-08-2014, 13:21   #35
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Re: Lightning

Marine engineer Kasten,has an interesting read for lightning attenuation.A very good overview!
Lightning Attenuation Onboard
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Old 12-08-2014, 15:10   #36
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Re: Lightning

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Originally Posted by Arthur Garfield View Post
Marine engineer Kasten,has an interesting read for lightning attenuation.A very good overview!
Lightning Attenuation Onboard
It is a *very* good overview. It even addresses the often overlooked problem of whether to connect a anode protected bonding system to the lightning system. My take on this is that they should not be connected. But this requires the mast and rigging be electrically isolated from the DC ground (negative). This can sometimes be tricky, but doable. I'd then propose that the isolated lightning and bonding systems should then be connected to a heavy duty high current carrying spark gap. This would connect them during a strike and hopefully prevent a side-flash. It's all theory however, and impossible to test for effectiveness.
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Old 17-08-2014, 09:40   #37
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Re: Lightning

Also lots of good lightening info here:

http://www.marinelightning.com/index.html
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Old 17-08-2014, 11:15   #38
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Re: Lightning

i find protecting one's boat from random and highly unpredictable events is a fools chore.
might make ye FEEL better, but does it actually DO anything FOR the purchasor--therein lies the rub.
isnt a definitely gonna help ye item, isnt a definitely not gonna help ye item, and i find lightning something i would rather not attract. therefore i save my money for more definitive issues.
having been introduced to lightning up close and personal at the young age of 3 yrs makes one a lil more prone to avoidance as opposed to channeling. you can keep the bright stuff and we will watch the light shows.
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Old 17-08-2014, 12:05   #39
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Re: Lightning

Zeehag, we have argued this ad nauseum before - grounding your boat does not attract lightning. There is absolutely no scientific evidence of this, and many studies have been done. Actuarial data does not support it, so the insurance companies are neutral on it. I know as many boats that have been struck without grounding as you do with grounding, so please spare us the Benetaeu or other anecdotal stories.

Grounding your boat does help mitigate serious structural damage. ABYC recommends grounding the boat for lightning.

There is no practical way to protect a boat from being struck by lightning. There is no way to avoid lightning other than to not be in areas where it occurs.

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Old 17-08-2014, 12:47   #40
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Re: Lightning

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Originally Posted by colemj View Post
Zeehag, we have argued this ad nauseum before - grounding your boat does not attract lightning. There is absolutely no scientific evidence of this, and many studies have been done. Actuarial data does not support it, so the insurance companies are neutral on it. I know as many boats that have been struck without grounding as you do with grounding, so please spare us the Benetaeu or other anecdotal stories.

Grounding your boat does help mitigate serious structural damage. ABYC recommends grounding the boat for lightning.

There is no practical way to protect a boat from being struck by lightning. There is no way to avoid lightning other than to not be in areas where it occurs.

Mark

you may diss me until cows come home, but bakatcha, as the stuff you spew is just as off as that which i believe,. there is nothing in science to back up th e sales of these scam items sold to boaters as protection from lightning damage-- you may wiish to s=discuss the protection factor with the nasa scientist w ho lost his boat not once but twice probably because of lightning protection of a most nasa ascientific varity.
and do not tell me my i am misguided, as you are just as misguided in thinking that alleged protection isnt attractive to the electrical force seeking a ground..
yes, your boat grounded is attractive, as an easier path to ground is most attractive for lightning.
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Old 17-08-2014, 13:14   #41
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Re: Lightning

Lightning is a very random event, and the things we can do to avoid it - even if they do what they are supposed to do - don't change the outcomes much: it's mostly luck. That said, I like to do what I can.

By grounding the mast and putting a lightning rod on top any charge that forms on the top is bled off. Charge buildup in the lowest cloud layer (negative IIRC) attracts the opposite charge to the top of the mast, and in extreme cases forms St. Elmos fire (a blue glow as the charge ionizes the air). This creates a slightly more attractive point for lightning to hit. A pointed rod creates a tiny area of high field strength which more easily bleeds the charge off. Compared to all of the other variables this has a very small effect - possibly negligible. Needless to say lightning does not lend itself to tidy lab experiments, and anecdotes are not reliable.

It seems to me that one of the main benefits of providing a direct path to ground (seawater) is that when hit the lightning will have a lower chance of not flashing through the rest of the boat and possibly hitting someone. A direct hit is going to wreck the electronics in most cases. A surge protector is a good idea for protection from lightning getting into the power system, such as when it hits the grid nearby, but isn't going to help a direct hit.

According to the ABYC the DC grounding system (including bonding) is "for the purpose of minimizing stray current corrosion and ensuring a fault current path in the event of a short circuit." Personally I feel the idea of bonding together all underwater fittings is a great way to sell zinc - simply electrically isolating bronze thru-hulls is sufficient to prevent corrosion. What has been driven home to me by the local ABYC rep is the second purpose, which assures that any short that reaches a thru-hull will find a route back to ground sufficient to trip the breakers. In fresh water an AC short to an isolated thru-hull won't trip a breaker but can set up a lethal electrical field near the boat, possibly causing electro-shock drowning (ESD). As far as lightning goes, if it grounds via a thru-hull it can cause a steam explosion that blows out the fitting so I wouldn't consider it a safety feature for lightning.

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Old 17-08-2014, 13:44   #42
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Re: Lightning

A lightning ground and DC bonding should be separate. I wouldn't consider grounding lightning to a thruhull very safe.

I personally know of two boats struck without any lightning ground that blew multiple holes through their hulls and created a lot of damage (one was sinking, but they were near a lift and hauled). I know 3 boats struck with lightning grounds that had no hull or other structural damage. I know 2 boats on the hard (ie, not grounded) that were struck with resultant hull damage.

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Old 17-08-2014, 13:55   #43
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Re: Lightning

The problem is that your sample size is so small that it is anecdotal rather than statistically significant. But I'm with you: my mast is grounded and has a pointed rod on top, and I'd recommend that.

I agree about the bonding: thru-hulls are the last place you want the lightning to go. A separate lightning ground should help the odds, but it still could flash over to the thru-hulls or bonding system.

I believe in tipping the odds in my favor, but with lightning the random (luck?) factor is very large.

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Old 17-08-2014, 14:51   #44
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Re: Lightning

Lightning.....Hmmm,Seems to be concrete and specific actions to take to minimize damage to ones vessel and/or gear.One can act ostritch to "gods will",all fine and good.I prefer to delve into any and all empirical data along with ideas that are PROVEN to attenuate damage from lightning strikes.
To suggest nothing will improve vessels' attenuation of lightning is height of ignorance,lazy thinking/mind ,though probably both ! Faraday cage is PROVEN to
inhibit damage to electronics with proper distance of in/out puts disconecction!
Read the Kasten lightning attenuation link I posted earlier in this subject.
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Old 17-08-2014, 15:30   #45
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Re: Lightning

You guys are right about lightning being utterly unpredictable and difficult to protect one's boat against. My boat's been hit twice that i know of- I was onboard. The first time she had no grounding system & the ground-to-cloud streamer formed at the mast and resultant blast went through the encapsulated ballast & punched thru both sides of fiberglass skin. Lots of collateral elect. damage.
So I installed a grounding plate close to mast base, attaching it with ribbons of copper (for lightning's R.F. nature). Some years later, my boat gets hit again, damnit. But was lucky- the blast harmlessly exited the ground plate. Minimal damage this time, all lights on mast blew & depth sounder transducer fried internally.
Weird stuff and my mast was the SHORTEST one around!
Studied electrical theory in college & will still never understand lighting's vagaries.
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