same lightning protection on a heeled and on a "staight" s/y ?????

T

taratoo

New Member
Joined
12 Nov 2005
Messages
6
Location
greece
Visit site
same lightning protection on a heeled and on a \"staight\" s/y ?????

Fellow sailors,
don't you think that wiring the shrouds to a grounding plate will drive the mighty lightning instead to the plate somewhere else(especially when the boat is heeled)????
Fair winds and fair lives to everyone.
 
Re: same lightning protection on a heeled and on a \"staight\" s/y ?????

This question is as unfathomable as the path of a lightning strike. May the density of the enquiry never reach its apparent negative potential. A chain draped around the back stay may not serve to relay a strike but at least it gives you something to do while the thunder is rolling around.
 
Re: same lightning protection on a heeled and on a \"staight\" s/y ?????

[ QUOTE ]
. . . gives you something to do while the thunder is rolling around.

[/ QUOTE ]

I think you'd be better off wrapping the chain around your backstay BEFORE the thunder starts rolling around!
 
Re: same lightning protection on a heeled and on a \"staight\" s/y ?????

It's gonna get to the grim stage of sitting huddled at the tiller cringeing as waves pile up around in a squall. Might as well muck about with a bit of chain as worry, eh?
 
Re: same lightning protection on a heeled and on a \"staight\" s/y ?????

I agree with wavelet. There is nothing you can do about the lightning, it will go where it wants and destroy what it wants, or destroy nothing if it feels so inclined. So you may as well fiddle with a bit of chain, or gaze hopefully at your masthead bottle brush, while you are waiting for it to decide. Of course by now you will have disconnected your expensive electronics and put them in the oven or a steel box.
 
Re: same lightning protection on a heeled and on a \"staight\" s/y ?????

The problem is that by earthing any stay you will to an extent attract the lightning. The grounded mast top will extend the first leaders out toward the charged cloud. Now this is fine if your stay can handle the current when the real strike arrives after being invited by the leaders.
However Stainless Steel is not a good enough conductor in fact its resistance will cause it to melt rather quickly with the real current.
so the only answer is to earth the bottom of the mast. The resistance of aluminium is low enough to carry the current without too much heating.
of course that is a brave statement and a big strike might just melt it anyway and in any strike case you should investigate the hardness (temper) of the mast in case it has been weakened.
It is important to provide a high current copper cable from the mast base to the sea water via the keel or a ground plate of several square feet. What size cable is enough? well i would say start at the size of your starter cables. In this case it is not sio much the voltage drop with current as the fusing current of the cable. Again the keel bolts could be the highest resistance and so be weakened by the current.
In the case of a wooden mast if it is dry and you have no wiring or steel wire halyards then you are perhaps safest. It is the conduction of the low current leader that starts all the problems. a conductor provides an attraction of an area something llike the radius of the height. So having no conductors more than say 2 metres means you will only attract strikes to a range of about 2m radius. That is simplly because the strike doesn't want to go sideways more than necessary.(ie it easier to go to the sea than sideways to youur boat. But a 20 metre conductive mast will attract strikes for a 20 metre radius. So you must expect more likely hood of a strike..

It is all a bit too much to worry about but if you choose to worry that seem to be the best guidance. (in a very speculative area)
olewill
 
Re: same lightning protection on a heeled and on a \"staight\" s/y ?????

Hi There

I have been thinking on this issue lately.

I was wondering it it would be as effective to haul a temporary conductor up the mast when required using a spare halliard, and then trailing the other end in the sea. Obviously the top end of the conductor would have a point or fuzzy brush on that is weighted in a way to keep it correctly orientated. The conductor itself will need to be a highly conductive wire - guage 0 or something like that with perhaps a largish plate on the section trailed in the sea.

Not sure how effective or practical this may be. Whether it would work underway or not...

I have been thinking of this option which may be simpler than leading a wire from the mast foot (mast is wood so will need a conductor from the tip anyway) down to the hull, making holes for the cable to go through and then attaching a grounding plate...

Cheers
Charles
 
Re: same lightning protection on a heeled and on a \"staight\" s/y ?????

William,

I hate to disagree with you, but I think you need to read up a bit on lightening protection theory. If I remember correctly, the idea is to stop the build up of the precursors to lightening. The lightening conductor is a misnomer. If you are struck by lightening, any amount of conductor and earthing is going to be precious little help.

From http://www.lightningsafety.com/nlsi_lhm/lpts.html

The phenomenology of lightning strikes to earth, as presently understood, follows an approximate behavior:

1. The downward Leaders from a thundercloud pulse towards earth seeking out active electrical ground targets.

2. Ground-based objects (fences, trees, blades of grass, corners of buildings, people, lightning rods, etc., etc.) emit varying degrees of electric activity during this event. Upward Streamers are launched from some of these objects. A few tens of meters off the ground, a "collection zone" is established according to the intensified local electrical field.

3. Some Leader(s) likely will connect with some Streamer(s). Then, the "switch" is closed and the current flows. We see lightning.

The idea of a lightening conductor is to ensure that upward streamers are not launched (sic) from your boat and mast.
 
Re: same lightning protection on a heeled and on a \"staight\" s/y ?????

[ QUOTE ]
William,
The phenomenology of lightning strikes to earth, as presently understood, follows an approximate behavior:
...
The idea of a lightening conductor is to ensure that upward streamers are not launched (sic) from your boat and mast.

[/ QUOTE ]

Incredible knowledge in all the above posts. Phenomenology is really what I meant when suggesting mucking about with a bit of chain, more a coping stratagy than anti-conductive stance. The thought does come to me though it is not wise to handle wet metallic stuff in lightning storms so just stick to huddling at the tiller as long as its a nice piece of iroko or, as mine is, a sexy laminate of some whitish and some reddish hardwoods.
I know it's flippant, but that's what dolphins do to survive (act flippantly) and that's the phenomenological way of the ocean /forums/images/graemlins/tongue.gif.
 
Re: same lightning protection on a heeled and on a \"staight\" s/y ?????

Thanks John I appreciated the reference. I don't think the end result of what you should do to your boat is any different. The actual success of the current carrying capability is of course never known until after the direct strike. I still reckon that the heaviest earthing conductor from base of mast to earth keel etc will give you the best chance. A heavy copper wire will dissipate a lot of current from a strike before it vapourises. Don't be near it if you can mkanage incase of this vapourisation.
The other uncertainty is regarding a sharp or multi tipped probe at the top. This style will dissipate static buildup ie St elmos Fire at a lower potential so may discourage the initial leaders from earth but then that may not be good for discouraging a strike. So yes you are right my knowledge is a bit limited and if your boat was on one of those mountain tops in USA where lightning strikes regularly this boat protection would probably be blown apart but for us sailors I think grounding the Al mast is the way to go.
olewill
 
Re: same lightning protection on a heeled and on a \"staight\" s/y ?????

Thanks Will

If its of any interest, I have a very heavy copper braid from my mast compression post to the keel. The mast compression post is of course bolted through to the mast foot plate which is in direct electrical connection to my Aluminium mast.

I am sure that bits of it would vapourise instantly if we received a direct hit. Furthermore the induced voltages in any nearby electrical equipment would probably destroy most electronics. That is why you see suggestions to put items within a 'Faraday Cage' - ie your metal oven, or to wrap up a spare hand held GPS in silver foil.

My feeling is that lightening is still not understaood very well, although I do believe the bit about pre-cursors and trying to eliminate them.
 
Re: same lightning protection on a heeled and on a \"staight\" s/y ?????

Fellow sailors,
doing my best to learn from your experiences ,i owe you a grateful thank you for your contribution to my query and post some interesting real experiences i downloaded from a forum ,not too long ago,but long enough to forget where from!!!

PS My apologise to the authors,but it's for a good reason ........

Posted: 2 Jan 2006 15:18
Quote

Bill Balme,

My Prout Snowgoose catamaran has been struck by lightning twice. The first time, while offshore, the VHF antenna, tri-color light and separate anchor light exploded off the masthead, but no other damage occurred. The boat was not equipped with a lightning grounding system.

The second time, while anchored in southern waters of the Potomac River, my wife and I watched as a small independent cloud cell marked by lightning separated from a major storm. This cell made its way directly toward us - nearly perpendicular to the direction of the main storm - while periodically discharging lightning to the water. I was sure that if the track was maintained, the cloud would pass directly over us, so we secured the boat the best we could.

ALL electrics were turned off via the master battery connector; all individual circuit breakers were selected "off;" all gear with power switches were selected "off;" ac-powered appliances were disconnected from outlets.

When the cloud moved close to us, we huddled in the cabin, away from metal as best we could position ourselves. Through an on-deck hatch on the main cabin top, as our body hair erected because of the electrical charge in the air, we saw exploding plasma when the masthead was struck and flash lightning streaked across the cabin. We were okay, and we watched this errant cloud make its way beyond our boat, continuing to emit lightning.

Except for our 110 VAC reverse-cycle ac system, every piece of electronic gear we had on the boat was made inoperable. The alternator, inverter, in-water transducers, nav gear, electronic wrist watches, tiller pilots, internal battery-powered boom box, GFIs, lights, etc. The tv, clock radio and some other items had been unplugged from the 110 VAC system, but they became non-functional after the strike. I was able to crank the diesel engine and return to home port, but the gel batteries subsequently were unable to hold a charge. The compass was unusable, but after several weeks gradually corrected itself.

Some gear, small radios, VHF, seemed to function but within hours or days their operation became erratic, a common symptom of lightning damage. Surveyors told us that after a direct strike, every piece of electronic gear should be suspect. In their experience, they also said that this type of damage was not uncommon for protected or unprotected boats.

The two non-conductive ends were melted on the very sturdy stainless-center antenna insulators on the backstay, but they didn't fail. Nevertheless, the charge made its way across both insulated ends to a lone chainplate, which was not immersed in water, grounded or connected to any other metal.

In the aftermath of that experience, I researched lightning protection for boats. Although I had experience in lightning-turbulence research/protection/avoidance for airplanes, I learned that the different environments make for very different means of tackling the problem.

For boats, lightning protection (or not) doesn't prevent (or cause) a lightning strike. Moreover, a strike's electromagnetic energy isn't confined necessarily to a lightning grounding system, therefore electronics may be made inoperable despite protection. Even so, the literature makes a good case that a lightning grounding system will increase protection for the crew and may divert sufficient energy to ground to prevent equipment damage.

I have seen a lightning-protected boat at anchor take multiple strikes at the masthead during a single storm, but no damage was done to any of the electronic gear. As with anything involving Mother Nature ... there are no guarantees ... we take your chances.

Nevertheless, these experiences cause me to be very cautious of being too dependent on sophisticated electronics to navigate my boat. In the aftermath of the last strike, I installed a lightning ground system aboard my vessel.

Bill, I know I've gone beyond the short answer to your query, but I believed this first-hand experience was appropriate to the discussion.

Roger
Posted: 2 Jan 2006 16:01
Quote

On our first trip to the Bahamas in a Jeanneau DS40 we had been through two thunder storms and had to lay off Chub Cay to let a storm blow through - after anchoring another one hit and a close lightening strike blew all of our electronics. From the Raymarine CRLC70 to our reefer to our windlass and beyond. The surveyor, two marine electrican, the guy who put our boat together and locals all agree that the only way we did not get a direct hit was this dissapinpator. On the good side the hand held gps was unaffected as was the main compass (we do carry a spare handheld I use to use when climbing mountains) so it was back to paper which we always carry and periodic charting.
One thing that we did notice was that the vfh antenna was blow off the boat but the anchor light, besides a blow bulb was not melted. The radio antenna was above the dissinpator so if I had a lower antenna would we have still been hit as lightening would presumably go to the highest so the new antenna will be cut down a bit.
chuck ritenour

# Posted: 3 Jan 2006 06:04
Quote

The boat is on the hard while my wife and I complete an extensive refit ... the mast is stepped on deck, which allows for a 4-guage tinned, stranded copper cable connection to a 6-foot x 3-inch strap (not foil) thru-bolted with bronze bolts to the outside aft section of the center nacelle. This made for a simple, but incomplete, protection system.

Moreover, while allowing for an excellent direct vertical path to ground, this path also allowed the cable to parallel the adjoining ac/dc electrical panel and the cabin door in the cockpit, undesirable consequences.

After the second lightning strike on my boat, strike marks were discovered near the various chainplates, which suggest that the energy was widely dispersed. The surveyors determined that the strike was discharged primarily through the transducers and the engine/sterndrive.

I'll implement a more comprehensive system during this refit. That task is a few months in the future, so I haven't focused on the details. Current literature and discussions with some lightning researchers suggest that multiple paths to ground likely will improve protection over a single path to ground.

I'm considering direct paths to ground on the fore and aft chainplates. I'll probably implement ABYC recommendations for following the cabin-top outward from the mast base to ground (for locations that would otherwise place the discharge path alongside a cabin door), rather than the vertical path previously in place. All significant metal above- and below-deck will be bonded in the system.

From an electronics standpoint, operators of remote (geographically difficult) transceivers have a special interest in protecting their equipment from lightning strikes, and they offfer a wide range of protection suggestions such as equipment-specific arrestors to ground; circuit proctection on both negative and positive conductors; arrestors on antennas, etc. Most important is preventing the energy from getting inside the facility, so grounding the equipment (e.g., coax, wire) connectors outside the facility is important. BTW, just disconnecting the antenna and power cables from gear doesn't mean that energy entering those cables can't arc to nearby equipment - or crew. I imagine that Greg and Bill Trayfors can offer some information on this topic too.

Faraday boxes can offer some protection, but they too should be grounded to be effective.

This is a simple - and incomplete - outline of some actions that can be taken for lightning protection, and none guarantees protection. As in most tasks, this is not rocket science; success is in the details, such as mapping cable routes and ensuring good electrical connections. Moreover, the material costs of wire, connectors, copper strap and individual equipment protections probably will be in the hundreds of dollars - not thousands - and within the installation capabilities of most cruising sailors.

Hope this is helpful. I'll share the details (such as specific components and where to get them) when I'm done.

Roger
Posted: 5 Jan 2006 01:03
Quote

It would seem from my very cursory reading that the Faraday cage doesn't need to be robust enough to survive being in the path of a lightning strike, but rather is designed to protect its contents from the magnetic field(s) created by the nearby pathway of the electrical energy, i.e., the huge current running down the shrouds will generate a mag. field that will likely encompass most of the vessel, and it is this magnetic field that induces current in even turned-off electric/electronic devices.

If that is the case, a flimsy mylar blanket (survival blanket), and grounded couldn't hurt, wrapped around a cardboard box, would be adequate. It also might prove effective to "blanket" engine components such as alternators, and disconnected battery banks (though I wouldn't let the blanket contact the battery posts).

A lot is being said about lightning here, but the moral of Bill's post speaks of putting all your eggs in one basket, and begs a moment to inventory your set-up of critical systems (manual as well as electronic). The use of fragile electronics, which can be upset as easily with that errant wave or hot coffee as with a bolt from Poseidon's hand, is a wonderful convenience, but dependency on them without reliable backups of a different type is imprudent.

Oh, and while a backup copy of your operating system is good, it won't run on fried hardware.

Jeff
 
You must log in or register to reply here.

Share this page

Top