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Old 05-03-2014, 17:51   #1
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Lightning

I'm sure this subject has been talked to death, but does anyone with a scientific or meteorlogical background know if a mast that is grounded to the water, is safer (or) does it actually attract lightning? I've studied this problem for years, in dozens of articles and scientific papers and still find no one that knows for sure. I appreciate Benjamin Franklins work and how many lives were saved, but then (as my wife brought up), why are there no lightning rods on any NEW construction, anymore.
Anyone have a clue?
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Old 05-03-2014, 17:59   #2
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Re: Lightning

Grounding the mast makes little difference to chance of a ligtning strike. The evidence is that by reducing the static charge at the mast tip the risk of a strike is slightly reduced, but the effect is very small.

Where grounding does make a significant difference is reducing the risk of severe damage if a strike does occur.
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Old 05-03-2014, 18:05   #3
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Re: Lightning

Google knows all :-D

Lightning and Your Boat - BoatSafe.com
GETTING ZAPPED
Lightning Ground Systems | WoodenBoat Magazine
Lightning
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Old 05-03-2014, 18:08   #4
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Re: Lightning

Quote:
Originally Posted by Neil Holck View Post
I've studied this problem for years, in dozens of articles and scientific papers and still find no one that knows for sure.
The real truth is only known here on Cruisers Forum.
Those other sources are a bunch of baloney!
'Jack' knows the true facts that your mast will attract a lightening strike if grounded to the water. Make sure you can capture the energy when it happens, so you can afford to replace all the electronics.

BTW, actual useful info here from 'the professor' is to store sensitive electronics in your microwave, since it has a farraday cage around it to keep the microwaves in, and that also keeps them out.
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Old 05-03-2014, 19:48   #5
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Re: Lightning

An insurance actuary once replied to one of the countless nubers of threads and said theres no difference if grounded or with rod on the mast etc. boats get fried. He said if there was a method to stop or mitigate lightning the insurance companies would insist you have it.

There aint.
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Old 05-03-2014, 19:59   #6
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Re: Lightning

There is a whole range of safety and backup equipment that reduces the chance of an accident. Despite the proven value of a lot of this equipment insurance companies do not generally specify inclusion in their policy.
(Radar, AIS transponder, or even GPS are simple examples)

The science behind grounding reducing the chance of damage is well proven. However, it is important to understand it does very little to reduce your chance of being hit. Even with a grounding system you are still likely to damage most of your electronics in a direct hit, but a correctly wired grounding system will greatly reduce (not eleminate) the risk of severe damage such a destroying one of your seacocks (with rapid sinking) or cainplate (with the mast falling down)

It is a worthwhile, reasonably inexpensive, addition that is frequently not incorporated because of the ungrounded (sorry I could not resist ) fear that it increases the chance of a strike.
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Old 05-03-2014, 20:59   #7
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Re: Lightning

so, the overarching question for me is how many sailors actually ground their mast?
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Old 05-03-2014, 21:12   #8
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Re: Lightning

I never have. Then again, I have never isolated the mast either. On my various boats, I haven't ever really planned for a strike (rightly or wrongly).
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Old 08-08-2014, 21:23   #9
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Re: Lightning

We are totally grounded but in fresh water.

I think we were hit 5 weeks ago while we were off the boat visiting family. We arrived for a 4-week 800 mile Great Lakes cruise with food & supplies and found - not working:

AIS
VHS
Stereo
RayMarine speedo but water temp works
50 amp main breaker
NAV light on both main & mizzen
3 of 6 deck lights
all forward cabin lights
Nav lights a the bow had wires fused
Spare 1500 watt alternator on the generator smoked when the power was restored.
Autopilot unreliable
Xantrex scrambled but a total disconnect & re-boot worked.
Windex on the main mast missing & the remains of its carbon fiber stalk are wrapped around the lightning arrester.

Note that the lightning arrester appears un-harmed.

The Simrad nav chart plotter is OK. It is wired so that the power hot & neutral are both interrupted by an air gap on a local double pole toggle switch. Also switched, the radar & depth sounder & also not damaged.

I wonder if total air gap disconnect including the ground/neutral and antennas would go far to prevent damage? This would be about the same as an uninstalled device lying free on the table. I think I will be buying a few switches.
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Old 08-08-2014, 22:22   #10
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Re: Lightning

We are totally NOT grounded. Three years ago we were hit by lightning in the sea of abaco. A huge thunderstorm was coming towards us so I took down the sails and put out the anchor. I stayed in the cockpit to check for dragging (we didnt drag; we have a manson supreme with all chain rode). suddenly there was a loud bang - like a 155mm howitzer firing right next to me - and a blue light came rushing down the mast. It was over in a second. I went below to check for leaks but after ten minutes of searching out the hull, bilge, and all eight bronze thruhulls found no problems.

It took a few days to discover all the damage but I was pleasantly suprised to find it amounted to just a few hundred dollars.

The fixed vhf and depthsounder were dead. I replaced them rather than repair.
The furuno navtex stopped working, but after careful checking I noticed it was fused on both the positive AND negative leads. The negative fuse was blown and the unit was back in service after I replaced the fuse.
The alternator was not working, but I carry a spare.
All the nav light bulbs had exploded.
Two of nine interior light bulbs were blown.
The masthead antenna had disappeared. I think this is the point where the lightning struck.
All of the devices that were directly wired to the battery were untouched - autopilot, fridge, inverter, solar panel/controller. Batteries were also untouched.
Handheld gps's and vhf's were untouched.
Thats it. I'm happy that I'm not grounded. I've always had nightmares that a strike would ground to a thruhull, blow it out, and sink the boat.
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Old 08-08-2014, 22:29   #11
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Re: Lightning

That is pretty funny. It sounds like any return to the boat, you feel lucky if anything works. Next time it might be better, you never know.
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Old 09-08-2014, 05:38   #12
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Re: Lightning

Quote:
Originally Posted by Neil Holck View Post

(...)

no one that knows for sure

(...)
I strongly believe this is the case.

b.
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Old 09-08-2014, 06:02   #13
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Re: Lightning

Quote:
Originally Posted by MarkJ View Post
An insurance actuary once replied to one of the countless nubers of threads and said theres no difference if grounded or with rod on the mast etc. boats get fried. He said if there was a method to stop or mitigate lightning the insurance companies would insist you have it.

There aint.

Agreed. A thousand opinions, but no solutions. IF there was a solution, the all-seeing cruisers on the internet would know about it and you could order it on Amazon.

Best you can do is try to designate the route the lightning is going to take getting from your boat to the water. That doesn't mean the lightning is going to take the route you prefer, though.
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Old 09-08-2014, 06:07   #14
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Re: Lightning

knowing of a former beneteau 50 in slidell which was hit not once but twice in same location in 4 years ... NASA scientist with ALL the scientific alleged lightning protection. secodn time killed boat permanently and th e power cord half way to his house.
watched as boats in mexico with lightning protection devices were hit and one even glowed green fro miles(catamaran). lovely.

seems to me that as i have been sailing without alleged lightning protection , and i watch as those with protection are first to be hit-- i am happily unprotected, as i truly feel these protected boats may not have been destroyed had they not had something that attracts lightning by way of easy pathway to ground.
does not electricity choose path of least resistence.....in which case, lightning rods and protection(alleged) against electricity in air seem to be actually performing the action of attraction of the lightntning to the boat with easiest access to ground.
that aint my boat. that aint gonna be my boat.
we managed to sail thru some rather nasty electrical storms without being hit--- wasnt fun and was damn scary--guy i sailed with was a holy magenta line follower and got upset when diversion from exact course was made to avoid these nasty cells.
i will divert course when i find i am in pathways of storms with electrical charges....magenta lion is merely a suggestion .. not a law.
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Old 09-08-2014, 06:31   #15
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Re: Lightning

Quote:
Originally Posted by onestepcsy37 View Post
I'm happy that I'm not grounded. I've always had nightmares that a strike would ground to a thruhull, blow it out, and sink the boat.
Doesn't the CSY37 have a keel-stepped mast? If so, you are grounded by default. I don't understand why you worry about a strike finding its way to a thruhull and blowing it out, while simultaneously being happy not to be grounded? The purpose of grounding is to provide a more favorable path for the lightning than a thruhull.

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