Has anybody used a lightning master?

[Tom S]

Arlyn, Thats fair.

I read your whole response and in the context you've placed it, I won't argue with any of what you've written.Too bad there isn't an easy answer - I'm still torn on this decision.And on the original question and issues of bottle brushes, I'm with Gord on this. I wouldn't go out and buy one, but I wouldn't take the time and effort to remove one either.

 

[Fred Ficarra]

Arlyn, two problems with your post. You have to

re-do your survey. Just because a boat has an inboard, doesn't mean its' mast is grounded. That is the job of the wires connected to the mast. No connection, no ground. The other problem is that you assume a vessel is grounded because it has a masthead vhf antenna or an instrument of some type. That has no relationship to grounding either. Anything that is on the masthead can and will work perfectly without having any contact with the water. And that is the definition of grounding. Whether it works to prevent strikes, is the issue. But I'm certain your survey is flawed too. My experience is detailed with my post over at 'Big Boats'. With a ground, no hit. Without a ground, twenty thousand dollars damage. I'll be right back. I'm going to cut and paste my story.OK here ya go;(lightening) That is the one subject that will get the biggest argument here, (next to politics and religion). I can tell you my experience but only because we have the same boat.You might have seen the black lightening ground wires secured in the bilge to your keel. That is the only place the factory grounds these boats. It seems to work well. I have been in outrageous lightning storms in Costa Rica and other places and was never hit. But then, one day, I asked a friend and buddy boater, what he did to seal up the rusty keel joint on his Benetaeu First-38. He said 'sitkaflex'. I said OK. BIG MISTAKE! The keel needed to be in contact with the water to ground the 'potential'. (St Elmos' fire) AKA, return path. I might as well have removed the ground wires. We launched in Costa Rica and headed for Panama. A rain cloud approached. Boom! One, and only one, bolt came from that cloud. It blew everything off the top of the mast and toasted $15K worth of other stuff. We limped to Panama and then to Florida. I parked the boat on the hard for the next season at Key West. I read everything I could find on the subject and learned about the 'return path' theory. I repaired the 300, or so, holes blown out of the keel and installed a ground plate. A single wire from the mast was then connected to it. that was 13 years ago. No more strikes and the boat has been through some major Florida lightening storms, with strikes throughout our anchorage. But, is 'bleeding potential' the answer to lightening strikes? I don't know.

 

[Arlyn Stewart]

A grounded mast

quote:Just because a boat has an inboard, doesn't mean its' mast is grounded.Thats true, but here's the deal. The 12v system is grounded to the motor casting necessary for dc return for the starter. This means that if any of the lighting fixtures on the mast, instruments mounted on the mast or radio antenna mounted on the mast have a ground which bonds to the mast, the mast is grounded thru the dc negative, the motor casting and to the prop.An antenna mount would almost be a sure thing as far as grounding the mast.Quote: Anything that is on the masthead can and will work perfectly without having any contact with the water. That is true, generally dc circuits on a boat have pairs of wires that supply both positive and negative circuitry. I did not mean to imply that the mast was often if ever used to supply part of the ground path. The mast gets grounded incidentally by the mountings of antennas, etc.My point is that it is the incidental grounding of the mast that alters it from an isolated to a bonded condition. An intentional ground wire at the base of the mast is not a requisite to the mast being grounded. Obviously, an inadvertent ground would not be capable of handling a lightning strike... but it just might be part of the invitation for one.btw, even if a LPS is installed, it would be wise to disconnect the coax to the radio.

 

[GordMay]

Grounded vs Bonded vs Isloated

All boats in water are "grounded" - at the very least capacitively.Hence no boat, in water, can be considered to be "isolated".Boats with an intentional ground conductor and electrode are "bonded".An interesting discussion folks - keep it up - we're working towards a better understanding of a complex subject.Gord

 

[Arlyn Stewart]

grounded

According to the Florida Sea Grant study, the greatest numbers of deaths due to lightning occur in small open boats. Yet, Boat US says that runabouts are hit only in 1:10,000 ratio. These two varying statements raise questions. One of which is, aluminum vs fiberglass. Again, the need for more detail in statistics.The only fatality recalled locally was a fishermen in an aluminum boat, with his fishing buddy not hit. Is conductivity important? Would the fisherman have fared better in a fiberglass boat and fallen into the category of runabout statistics?I gotta believe that lightning is seeking ground and that the fisherman in the aluminum boat was an attractive target with his graphite rod extended airborne during his cast just as the golfer extends his club airborne during his swing.High on the list of those struck are farmers on tractors and heavy equipment operators. Why are they hit but not cars? Forgetting all we hear for a moment about Farraday cages on cars, how many cars are actually struck. I've personally never heard of a car being struck or seen damage to a car that was struck... and a great many of them have radio antenna sticking in the air. Why aren't they hit? There are certainly far more cars and trucks than farm tractors or heavy equipemnt. Why were old barns hit in greater numbers than newer homes? It might be that old barns with shake shingles and unpainted wood plank siding absorbed moisture and provided conductivity. Lightning protection on them was a necessity to direct a hit through a wire to ground rather than through the saturated wood which would catch fire. We don't often use lightning rods on homes anymore because they are built of materiels that don't become water saturated and are kept painted compared to exposed wood. IMHO... its a lot about being grounded... and if true, a sailboat that has a grounded mast stands a greater chance of being struck than one that doesn't.While my argument has basically been about trailer sailors remaining ungrounded, I agree completely that a blue water boat ought to have a LPS. However, there are ways in which they could have the best of both worlds. They could have both ungrounded mast and a lightning protection system.It would require some intentional effort to unground the mast during storms. This would require disconnection points for all the wires that go up the mast. The points could however be anywhere and to avoid corrosion ought to be of high quality connectors and sheltered in the bowels of the boat. By disconnecting all the mast wiring, the probabilities of electronics damage in my opinion would be reduced. Lightning can and has inflicted a lot of damage through ground connections. Printed circuit boads in modern elctronics have ground busses that interlace the circuitry making them very vulnerable to ground attack. Leaving the radio, instruments and dc bus connected to the mast where the lightning hits is no doubt much of the reason for so much electronics damage.I know of one ham station that had the tower 25 feet from the house and all wires running into the shack were disconnected at the tower but the station still got dammage. The lightning went down the tower and into the ground via the ground rod at the tower, came across the yard and up through the ground rod near the station and attacked. So, there are never any gurantees. Is it too much hassle to disconnect? Hams do it all the time... it becomes a simple discipline.The last step would be to interrupt the ground wire of the LPS with an air dielectric arrestor.

 

[Fred Ficarra]

Arlyn, I have to be brief, My wife has me by the

hair. (what did you think?) People in open boats are killed because they DO NOT have a mast, that affords sailors what is VERY COMMONLY known as the CONE OF PROTECTION. Tractors get hit because of dirty tires and equipment being dragged or pushed, that is contacting the ground. Cars only touch with rubber tires. We need to NOT compare land metaphors with the sea. It seems confusing to me. (maybe that's just me) An LPS operates by bleeding potential to the water. That's why the P stands for PROTECTION. The idea is NOT to get hit. Gotta go, my head hurts.

 

[Tom S]

Arlyn, are you sure the chassis of a VHF is ?

I thought the VHF antenna base (with mounting bracket) was isolated from the Coax shield ground ? (I guess I'm going to have to go to the boat yard and check with my VOM)Now I do know that if it hits the stainless antenna "whip" then its and easy "jump" down the coax wire (most likely blowing out the VHF base unit). Thats why people buy those lightning arrestors for the VHF coax cable. But the reality is that it will most likely jump down the mast instead of the coax (MUCH better path), if the mast was grounded.I know my mast head light is isolated (totaly plastic) as are the other items up there.Not saying "incidental grounds" don't happen, but they shouldn't on a maintained boat.My whole point is "incidental grounds" on the mast such as I described, are a joke for lightning and might as well not be there, because the second the lightning takes a sharp radius turn it's just going to "jump off" and leave that coax cable (or whatever) and head straight where it wan't to go, which is to the water, and most likely, its going to blast its way through the hull on its way.Unless its a relatively straight run down the mast to the bilge and to the DC ground, then to the engine ground and then out via the shaft. This is very unlikely, and that the reason one would want one "Straight Preferential" path for lightning to take out of the boat. Without a straight path its going to go all over the place messing things up (yes I do know that even if electronics are never touched by lightning they can still be "blown out" by EMP -- but I know that much less will be "blown out" if it doesn't go through the electronics)

 

[Tom S]

Gord, you're right, we are being a little loose

with the terms. I know the difference and sometimes its easier to write it that way, I'm sure there are some people that don't know the difference. Sorry.Maybe there is a good link for people to understand the differences in a laymans way.

 

[Tom S]

Fred, I've gotta agree with Arlyn on this

Even though there is a P (protection) in the term LPS it does not mean its going to "Protect" your boat from getting hit.I don't think there are ANY experts out there on this subject (on either side of the debate) that would claim that.What I do think most experts do agree on is that if you ARE hit than an LPS will reduce damage (hull, electronics, etc). But its all relative some lightning strikes are stronger than others.What they DON'T agree on is whether having an LPS (lightning Protection System) attracts more lightning strikes or reduces them or it doesn't make a difference. (To be honest, I don't know either)Forgeting we all have a sailboat, one thing I DO KNOW is that if I had an open motor boat, THEN I would really probably want to have an LPS system installed, because in those cases people DO DIE and many more are injured. Unless I thought I would just always try and outrun a storm, but the problem is, sometimes it a "bolt out of the blue" and the edge of the storm. Then I guess your number is just up.

 

[GordMay]

We watched a "hit"

In 1992, we saw a small (<15') open boat struck by lightning. The boat was passing close by a +40' sailboat, while entering harbour - I forget which (Lake Erie). There were two children in the boat, both laying down, and covered by a 'slicker' (it was raining). Dad was hunched down at the tiller. He was struck, and died. The boat did not appear to be damaged.I have no explanation of why the man was struck instead of the very nearby sailboat mast; nor why the boat showed no sign of the hit.Did sombody say that lightning is capricious?

 

[Tom S]

Gord, That's sad.

Thats why I think all this talk of an LPS or not, grounded mast, partial grounded mast or not is all just that -- talk --.For every story I hear of someones boat getting hit with an LPS there is another one like the story you told. It makes no sense. Who knows if that Sailboat's mast was grounded, but if you follow Arlyns arguments then there is a high probability that it was at least "partially grounded" (especially with all that rain). And with a 50 foot mast its potential should have been raised much closer to the lightning above that open boat. But yet it was that small boat that got hit. (Was the small boat inside what you would consider the so-called cone of protection of th sailboat?) The only thing I do know is that an LPS can and does save lives on open boats. A sailboat tends to already have something to be struck first instead of the people in the boat -- still afraid of side flashes though

 

[Fred Ficarra]

OK You guys are still thinking that grounding of

a sailboat mast ATTRACTS a hit. It is there for the opposite reason. AND you are thinking that potential is there and follows to ground, with the lightening, thus causing the strike. Grounding the potential eliminates the RETURN WAVE, thusly preventing the strike. That's why the guy in the pram was hit and not the sailboat. Research and experience (like mine) is starting to point out that this is true.

 

[Tom S]

Fred, I see the point you are making

In fact I have always kind of followed that way of thinking, but thats just your one experience of one person.Not trying to start an argument, but there are lots of people out there without a grounded mast and swear that thats the reason they weren't hit. (Arlyn being one of them - not necesarily me though)BUTIn fact - the one close call I had, I would fall into that category. I have written about my experience from last summer before, (more than once). I just so happen to have a keel stepped mast (C36MKII 1999), but it is in effect isolated from the keel (fiberglass step support - and isolated from the lead keel (I used a Ohm-meter to the keel bolts and verified)Plus I have a "Drive-Saver" on my shaft, so my DC ground is effectively isolated from the Ocean.I was in a horrendous thunderstorm last summer on LI Sound (July 21st look up the weather archives) Winds clocked above 70 knot gusts (my inflatable with gas tank behind my boat looked like a wind sock !) Lightning was striking all around, the Admiral was starting to get emotional and cry and it was one of the few times I have put on a PFD. Well I thought I was out of the worst of it and the 2nd weather cell was almost over when a lightning bolt hit about 50-100 yards from my boat (how can one judge distances in conditions like this?) All I know is that the flash and the boom was basically simultaneous. (I have since changed my underwear )By product of the strike being so close was that it knocked the radar portion out of my Chartplotter, it knocked out my Echo Charger and it knocked out my Accuguage tank guage. Though it didn't hit my boat. Believe me I was the tallest thing out on the sound for **miles** why I didn't get hit -- I don't know . But in fact the mast was not bonded to the seawater - unless you count the rain water from the mast making a conductive path somehow ? (thank you - big guy in the sky) The experts (I'm not talking about any of us) and the available data does not necessarily point to one way or another. In fact I think the data shows that its about a wash -- I have said it before and I'll say it again. With lightning there are no guarantee's it'll do whatever it damn well pleases. But I do agree with you -- If I DO get hit - I'd rather have an LPS system properly installed.

 

[Dan McGuire]

Interesting Fred

Some months ago, and I cannot find it now, I was involved in a discussion on another forum. I said that grounding the mast might help prevent a lightning strike. The person who started the thread was a science teacher who had a strong interest in lightning. He went to great lengths to show that grounding a mast would not prevent a lightning strike. I had always thought that lighning rods on a house would help drain off the potential and thus prevent the strike. I will continue to try to ground my mast to the water whenever there is a threat of a thunderstorm with the hope that it will prevent a strike. Even if it doesn't prevent the strike, it might help channel the srike so that the damage to the people in the boat and the boat are minimized.

 

[Jeff M21319]

A complex thread with a lot of opinions...

And I doubt mine will lend any clarity, but I'll try. Watched a science show on TV a few years back about lightening research. They were using ultra high speed movie cameras to record lightening strikes, which they would initiate by launching large 'model rockets' with a thin piece of wire attatched between the rocket and a ground rod at the launcher. As the rocket was fired into the air, (during a thunder storm) the cameras recorded a phenomenon that they called (if I remember right) 'streamers'. What this basically was is a very small 'reverse strike, in that a charge would actually travel UP the wire where it was then met by the actual lightening bolt, which would then travel back down to the ground. Subsequent research and photography found this also occurred when lightening hit other objects, like trees and houses. First, the streamer projects upward from an object, then the lightening meets it and follows a reverse path to ground. Their analysis of this was that the streamer produced an ionized path for the lightening to follow, because the ionized air provided a lower resistance path than the non-ionized air around it. The story was that this had been theorized in the past, but only by using new ultra high speeed movie cameras were they able to finally detect and record the event. I can tell you that the frame-by-frame photos were truly amazing. The camera was so fast that an average strike would be recorded across 6-10 frames, clearly showing first the streamer, then the lightening contacting it, the lightenings travel downwards, striking the object the streamer came from and then that object being blown to bits. One note of interest was that the streamers always came from a grounded object, so, might one postulate that a ungrounded mast may be less likely to produce a streamer and therefore less likely to be hit by lightening, but that if the mast IS hit anyway (due to, perhaps, rain producing a path to ground), a grounded mast will better dissipate that energy with possibly less collateral damage to the boat? Anyhow, great thread and it's good to see so many people discussing something that we will likely never have a complete answer for!

 

[Fred Ficarra]

I saw that show,

I'm not sure if the wire was grounded though. But everyone needs to remember that the cone of protection from the mast, protects sailors.

 

[Tom S]

Jeff M, good input.

And I think you summed it up pretty well with your last few sentences"One note of interest was that the streamers always came from a grounded object, so, might one postulate that a ungrounded mast may be less likely to produce a streamer and therefore less likely to be hit by lightening, but that if the mast IS hit anyway (due to, perhaps, rain producing a path to ground), a grounded mast will better dissipate that energy with possibly less collateral damage to the boat?"I'll tell you one thing - if I, or anyone on board my boat feel's their hair start to stand on end my instructions will be to immediately get away from all metal & "hit the deck" (and pray )

 

[Fred Ficarra]

Tom, I don't think that hair gets charged on a

sailboat. The mast prevents it. My wife reported that effect back in the '60s walking across a bridge when she was in high school. We almost never met.The rule when hair goes up is that the grower of the hair, get down. That is to ground the potential to avoid the strike. That's why the mast should be grounded, to AVOID the strike. More and more is being written about grounding to avoid the strike. Practical Sailor had a piece a while back. I read the article title in my junk mail, not the story. Anybody see it?

 

[R.W.Landau]

Some input...

I have not read this thread. I hope someone has pointed out that salt and fresh water must be treated seperately.Salt water conducts electricity, but it takes about 20 times the area of conductor to dissipate the charge in fresh water.r.w.landau

 

[Arlyn Stewart]

I've missed it , unfortunately

Thanks Jeff, test like that are fantastic... Theory can then be built upon or discarded based on such observations.I wish there was a test to get answers about Dr. Thomson's theory that an ungrounded mast is fed with a supply of airborne electrons to produce a greater charge at the masthead than that of the water surface. I can visualize the airborne migration but if that is true then why is it not true that they also blead off from the mast head and even at a higher rate because of its higher attraction factor which would then leave the mast at a less than ground potential.Someday we will know...