Lightning protection options

[jklightner]

Line losses transmitting DC over long distances is high. This is why we now use AC almost exclusivly. Mr. Edison and Mr. Westinghouse hashed this out at the turn of the century, and it wasn't pretty. But the upshot of it all, AC travels well, DC doesn't.

[Dimitri-2000X-Tampa]

I'd be interested in knowing the life cycle costs of buried versus overhead power lines

I actually inquired about this several years ago when first moving into the neighborhood (didn't like the overhead powerlines). Took me several people to get to the right person at Tampa Electric, but when I finally did, I didn't get the answer I (or you) may have thought.

The answer was that the lifecycle costs were virtually identical. Ie, they have just as many problems (costs) with buried lines as they do with overhead. So, it really only comes down to aesthetics as the main reason that most powerlines are buried during the last few decades. Its interesting, because my neighborhood was originally built in 1965 when they used overhead. By 1970, when the second phase of my neighborhood was built, they used underground. For me to change out, I would have to get everyone in the neighborhood to pay for it, and that is only realisticaly feasible through a tax referendum.

Hey, but our part of the neighborhood has the boat ramp at least

[Chip Hindes]

So if lifecycle costs are identical, underground wins for aesthetic and safety reasons, in new installations and whenever it's time to string new lines. It also makes a lot of sense to push that underground be retrofitted whenever safety aspects become paramount, such as at marinas and boat launches.

Our development went up in the early seventies, and all our stuff is undergound, gas, power, phone, cable TV. In other neighborhoods, outages of all these are normal occurances. In ours, almost never.

[Mark Prouty]

Consider the worst case scenario for a lightning strike to a sailboat - a small boat in fresh water. If the boat has been provided with a well-built protection system it is still an exceedingly hazardous situation. If lightning protection does not exist, the situation is life threatening. In both cases, the areas to avoid are close to the waterline and close to large metal fitting. In the unprotected boat, an additional -danger zone is beneath the mast or boom. Even in the unprotected boat, it is unwise to get in the water, as electrocution is highly probable if lightning strikes nearby. In fact, there is no safe place on an unprotected small sailboat, and in a protected boat only places of relative safety. There is, however, one place that is more hazardous than a small unprotected sailboat, that is a small unprotected boat without a mast. Every year there are multiple deaths of boaters in open boats caused by lightning strikes, but very few reports of sailors in sailboats killed by lightning.
The above general rules also apply to larger sailboats. These are generally safer, if protected, since it is possible to get away from the waterline and large metal objects, and yet still stay dry inside the cabin. As far as unharnessed electricity is concerned, a dry human body is much less attractive than a wet one.

Conclusions
Lightning protection on a sailboat means diverting the lightning current into the water without its causing any hull damage, personal injury, or electronics damage. This involves providing a continuous, mainly vertical, conducting path from above any vulnerable masthead transducers to grounding conductors immersed in the water (the grounding system) and a network of mainly horizontal interconnected conductors attached to large metal fittings, including the grounding system (the bonding system). Transient suppressors are needed on each piece of electronics equipment, and wiring should all be twisted pair for protection of electronics.

Ok, I'm not going to mess with the lightning protection.

By day, I'll steer clear.

At night while on board, I'll stay cozy in my bunk safetly away from:
* The waterline
* Large metal fittings
* The danger zone beneath the mast or boom.
* Water

I'll also make sure the insurance is paid up in case the electronics fry on the hull experiences damage.

* Anybody been in a situation like this where lightning hit?
* Anybody experience lightning damage to their boat?
* Anybody have a lightning protection system on their boat?

[Chip Hindes]

On the original Conch Cruise to Bimini, in June almost two years ago. On the very first day just after launching from Homestead, all but a couple of the entire fleet of 25 boats was anchored in about ten feet of water, at our jumping off point a couple hundred yards offshore in Angelfish Creek. We were spread out over an area about half a mile square. A couple boats were still in transit to the anchorage.

Just after sunset a severe thunderstorm with lightning blew through.

The whole thing probably didn't last more than ten minutes. We shut off all the electronics, buttoned up and stayed below, not touching anything but our feet on the deck and our butts on the cushions. By counting the flash-to-bang (rougly 1000fps) I determined that at least two of the strikes hit within a couple hundred feet of our boat.

Other than at least one anchor dragging in the high winds (different story which had nothing to do with the lightning) and some severely frayed nerves, to my knowledge, no damage was done so I assume nobody got hit. Also, to my knowledge none of the boats was equipped with any lightning protection system.

I respectfully submit the following: Even if you had 200HP instead of 50 or 90, without both an early warning of a coming storm (say from radar) and a clear indication as to its path, by the time you see it, identify it for what it is, drop the sails and fire up the motor, it's way too late to try to outrun a fast moving thunderstorm. Further, you're nearly as likely to run into a storm as out of it. I believe unless the situation otherwise precludes it, the best bet is to drop the hook or heave to under reduced sail, get below and wait it out.

[Jack O'Brien]

When we moved our print shop into a store that had previously been an often-burglarized TV & Applicance Rental Shop the front doors had, for security over the glass, heavy aluminum grating on them that looks like LARGE expanded metal. (We didn't get burglared but once and they came through the steel back door.) We removed the aluminum gratings and I use parts of them as temporary ground plates with heavy jumper cables for lightning protection. This aluminum expansion is lightweight, highly conductive and with all its exposed edges has a much greater "edge diffusion length" than a similarly sized piece of flat metal.

High voltage travels on the surface of conductors (wires) not the cores. This is partly why the ground plate edge length is more important than the flat surface area. One could consider cutting holes in a flat plate to increase the edge length. I'm not sure if these would be as effective as true, continuous edge but, sure couldn't hurt.

[Moe]

I've researched this pretty heavily and have come to the conclusion that if we take a hit on a Mac, especially on freshwater, we could be pretty well SOL no matter where we are in the cabin. Better than being at the helm, I guess, grounded through the steering and motor to the water, with the end of the boom right at head level.

--
Moe

[Jack O'Brien]

The former Commodor of our sailing club has a good sized ? sailboat docked behind his golf course house in North Palm Beach, Florida. It got hit, at dock with nobody aboard, twice within a couple of months last year. He had just replaced the electronics - insurance - when the second bolt hit. Insurance company is wondering??

Golf courses are dangerous for lightning strikes (serves them right) and if I have to get hit I'd rather do it while sailing than golfing.

[Divecoz]

There are a lot of boats on the island/Cozumel, some with Tuna Towers almost as tall as our mast. I see Numerous Sailboats with twice the mast as that of a 26, and to the best of my Knowledge no one has been hit in 14 years. Maybe I should say,. . . if they did get hit, no major damage/ loss of life /burned to the waterline was done . But as the subject has come up and I leave for there in a few days . I think I'll ask around for a direct answer .
As for the overhead vs. underground?? Tampa Lights answer surprises me . After 36 years in the industry. . . . Ice Storm damage to an Under Ground Service 0. Wind damage 0 UV damage 0 Vehicular damage negligible / 0 Maintenance near 0 Pole loss 0 and the list at least here in the Northern Climates goes on and on and then add safety and appearance .
HEY !!! I forgot to mention Hurricane damage and so did they,. . in other words who ever it was didnt have a clue.

[Jack O'Brien]

I've researched this pretty heavily and have come to the conclusion that if we take a hit on a Mac, especially on freshwater, we could be pretty well SOL no matter where we are in the cabin. Better than being at the helm, I guess, grounded through the steering and motor to the water, with the end of the boom right at head level.

--
Moe

Considering where we keep the gas tanks, I think the V-berth with the forward hatch unlatched might be the best location during a lightning storm. If I live through it, without paralysis, I can flap my arms after being launched out of the hatch.

[Moe]

Keep in mind the further you get from the base of the mast, on the V-berth, the closer you're getting to the chainplate for the forestay.

And on the aft part of the V-berth, you're real close to the water ballast.
--
Moe

[Mark Prouty]

I've researched this pretty heavily and have come to the conclusion that if we take a hit on a Mac, especially on freshwater, we could be pretty well SOL no matter where we are in the cabin. Better than being at the helm, I guess, grounded through the steering and motor to the water, with the end of the boom right at head level.

--
Moe

Ah, I'm just better off staying home inside my pineapple with a good book! No lightning there!!

(I have to make sure Sponge Bob doesn't hold hands. I don't know about him. None of that Buster the Bunny stuff either.)

[waternwaves]

Many of us mount a VHF antenna on the top of the mast.. but there is much to be said for having the lightning rod above the antenna.

one can mount a lighting arrestor on the antenna system.

But the best attenuation of a strikes charge is via the mast... with a bolt on drain cable...(I use stainless braided aircraft cable, but clean copper is a better conductor at least when new.) when the flashes start I pull the cable out clip it to the bolt and nut on the mast and toss it over the side.. there is a small plate attached to other end of the cable..... the purpose of the plate is to increase the bleed edge area.....charge is released easiest by sharp edges and points on the drain plate.

and stay clear of that line... till the storm has passed.....

[Catigale]

I have outrun storms on Lake Ontario - the key to this was

1 A sharp lookout for the first flash (my 7 year old Exec Officer)

2 Quick call to my friend at work for a peek at

www.wunderground.com

who then reported a storm system coming over the Niagara Penisula heading directly my way

3 Sails down, ballast out, and 18 mph to WIlson harbor - we beat the lightning by 20 minutes.

***I agree with Chip that you cannot count on this as a strategy in general, I got lucky this time. If you miss the first few minutes of lightning strikes your margin is used up. Also, the storm activity tends to be most violent on the leading edge of the storm, so it reaches you first.

...and to come clean, I got caught in my first thunderstorm last May on the Hudson River.nasty.......

Catigale

[Moe]

Interesting comment on the conductivity of stainless steel, Darren. That's one of several reasons I'm not favoring the idea of bonding the compression post and chainplates to the centerboard hanger, as I had considered (besides the fact it routes lightning through the cabin).

I know on the deck of mine, there may be a tiny gap (meaningless to lightning) between the also stainless mast base and the compression post/centerboard rope tube. I haven't looked, but wouldn't be surprised if the compression post is actually bolted to the mast base under the decking. I HAVE seen how far forward the centerboard hanger is of the compression post though.

Besides the lower conductivity of the mast base, compression post, and centerboard hanger, bonding the latter two would put two roughly 90 degree turns in the path of a strike. These issues, and the serious inadequacy of the hanger as a ground plane, without possibly threading the pin ends and cabling it to ground plates or strips bonded to the hull, leave me questioning whether bonding these would be a good thing.

I'm afraid that lightning would just get to the base of the mast (or to the chainplates) and seek another path anyway, because of the higher resistance from that point on. The question in my mind is whether bonding the post to hanger (as well as the chainplates to hanger) would increase the probability of a strike on the mast (despite scientific writings to the contrary) or that doing so would encourage a bolt that would've otherwise jumped from the mast (or chainplates) to the water, to go through the cabin.

I also look up in the cabin and note all the deck filler plugs in the liner, each representing a point for lightning discharge, especially those involved with the stanchions and lifelines. While bonding all these and the mast and chainplates together on an awesomely grounded boat MIGHT be a good idea, I wonder if it would be a bad thing on a poorly grounded or ungrounded boat?

In the end, as you, and some others here and elsewhere have, I've come to the conclusion that heavy cables, well connected to the mast, and led overboard to a grounding point, with sufficient sharp edging, deep enough in the water, may be the best hope for our Macs, especially when it comes to TRYING to keep it out of the cabin. The gold-plated (metaphorically speaking) version of this is the StrikeSheild. Some of the key points they stress:

• Copper for all compenents
• Tinning all components for corrosion resistance
• Crimping AND soldering (tinning) connections
• Use of adhesive heat-shrink tubing
• Adequate cable size, preferably 1/0 or larger
• Electrically robust connection between mast and cable
• Need for an "air terminal" especially above an antenna
• Need for an arrestor in any radio cables
• Unplugging electrical items (lights, etc) on the mast
• NOT bonding to the stays/chainplates, etc
• Adequate water depth for discharge point
• Total length of corners or edges on discharge point

I'm not going to argue that their solution is or isn't seriously overpriced, but I think those points may be something to consider for a DIY project. There are a couple of things that still concern me.

Their patent pending dissipater electrode certainly looks innovative as far as getting as many edges/corners as possible on an object, but I'm still not sure of its size and thus adequacy, especially in freshwater, and especially if the one-cable model was used. And the other thing that concerns me is the angle and radius of the turn, between the mast and cable, and in the cable as it goes over the gunwale, that lightning would have to make to follow the path to ground. I'd think one would want to attach the cable as high as possible on the mast to reduce those angles, and use heavy cable that would resist forming a tight radius as it goes over the gunwale.

And so now I come full circle back to your choice of stainless vs copper, Darren. Is it that corroded copper, such as might be experienced with battery cables, is an even worse conductor than stainless steel braid? Is the corrosion an issue only for those who use the cables while the boat is moored, rather than for occasional protection of personnel while on board (i.e. a lot more)? Might the StrikeShield be worth it for the former use and not the latter?

That leads me to yet another thought. Would grounding our short-masted Macs be counterproductive if they're moored in the midst of much taller-masted boats, especially those with inadequate or no grounding? Would lightning attracted by their taller masts be more likely to jump from there to our better grounded one?

Despite knowing that any of these solutions MAY do no good at all, I feel like I should at least do something, at least for when we're aboard. Determining exactly what and how much is still perplexing. I don't want to do something that would be worse than doing nothing at all. Comments from all are welcome.

--
Moe