Lightning Ground

[George ( C&C 40 )]

Hi All,


I just received an e-mail from the lady who purchased Pearson Triton #236 "Ca Ira" from me a couple of years ago. They got caught in a bad thunderstorm off Thomas Point Light on the Chesapeake bay over the weekend and took a lightning strike. She e-mailed me just to let me know that the grounding system I had installed worked. The system handled the blast and none of the on-board electronics were hurt. She'll send me an e-mail after the boat gets hauled later this year and let me know if it did anything to the keel. She did say that they could see the bolt flash over the conections to the cable but that it didn't cause any real damage.

The ground system consists of a pair of square 1" aluminum plates bolted onto the base of the mast that hold one end of the 2/0 ground cable and a length of 2/0 cable that goes through the deck, around the door frame next to the hanging locker and into the bilge where it attaches to a keelbolt. I had used the huge Anchor 2/0 tinned battery cable because I had read that lab testing showed that a really huge lightning strike that contained 7 or more return strokes would melt anything less than 2/0 cable.


George Jones

[grampianman]

Hello George,
This is timely as I live in Southwest Florida and lightning is a fact of life during the summer.
How did you attach the cable to the mast?
Mine is on a tabernacle so I was thinking I only need to attach heavy wire to the pivot bolt and then lead the wire down the compression post to the keel bolt. My mast and tabernacle are aluminium.
How did you lead the wire through the deck? Did you simply drill a hole and pull the wire through, then sealed it?

Thanks for your reply,
Cheers,
Ian

[Ceasar Choppy]

I saw Ca Ira out this weekend as I was part of the same race they were sailing in. On Monday she described the same blast. Now I know who "the guy that installed the cabling" is that she was referring to!

I like the idea of 2/0 cable as well. I unfortunately have an encapsulated keel so I'm going to have to look into a hull mounted plate (no, not a Dynaplate). Has anyone done something like this?

[George ( C&C 40 )]

Hi All,


I crimped on 5/16'th hole 2/0 wire terminals onto the cable then placed the terminal fitting between the two plates of aluminum. The whole assembly was then screwed into a tapped hole on the base of the mast with a 5/16'th bolt. I did this thing with the aluminum plates because I could then "Duralac" the stainless steel bolt I used and also keep the copper terminal fitting off the mast. I always Awlgrip my masts and this helps keep the paint from bubbling up around fittings with dissimilar metals. Not perfect, but it helps.

I'm sorry to say I forget how I attached the cable to the keel bolt or how I brought it through the deck. I'll post if I remember.

Also... I seem to remember reading that encapuselated keels don't need any kind of plate. The lightning will just burn a very small hole out the bottom of the keel.


George Jones

[Ric in Richmond]

Anyone rig up someting temporary to hook to the rigging and use at anchor in a storm?

My boat has NO lightning protection at all. The reading I have done makes me wonder if I should.

[grampianman]

I've used jumper cables. I attached both clips to the backstay and just dropped the ends into the water.
I had gotten this method from a friend who has sailed extensively in and around Florida. He sailed a LazyJack 32 schooner and on one occasion he got caught in a severe thunderstorm. He was sailing back from the Keys en route to Ft. Myers and was in Florida Bay at the time. He told me of lightning striking the sea surface around him but nothing (luckily) hit him. He had taken precautions, including hailing the Coast Guard and they were on a 15 minute update schedule. He said he has never been as scared as that. He had two jumper cables, one on the foremast and one on the main.

Cheers,
Ian

[xroyal]

Sure is a popular topic in boating forums now. Timely as we had warnings of possibly severe thunder/lightning storms last night. One poster said to ground to the battery, and throw it overboard. Your less extreme jumper cables to the stay seem more prudent.

[Ceasar Choppy]

I'd rather provide the lightning a path to the outside rather than let the lightning blow a hole in my encapsulated keel. From what I have seen, when lightning tries to go through fibrglass, it usually isn't one hole, but a million tiny little ones that can be hard to detect... This happened to a Cal 27 on our dock some years ago and although it was hauled after the strike to check for holes, nothing was found-- until the following winter when some of the holes had opened up and were weeping lots of water.

That said, I've sailed through my share of thunder storms to Bermuda and a recent Atlantic crossing. What amazed me on these trips was lightning struck the water all around the boat within 1/4 mile, but never struck the boat-- despite the fact that our mast was the tallest thing for a hundred miles.

[George ( C&C 40 )]

Hi Again All,


I found pictures of the lightning grounding system on #236 "Ca Ira" on the National Triton Association webpage in the MIR section. It appears that I used a waterproof thru-deck cable fitting near the base of the mast for the 2/0 ground cable. Also, I noticed the ground point at the keelbolt had a #2 battery cable connecting the engine block too. I now remember that this was to prevent any difference in electrical potential to develop between the big mass of metal that is the engine and the mast / ground wire area of the boat. Without it, there is the possibility of "side flashes" occuring between the two chunks of metal. A 100 - 200 amp flash through the cabin is never a good thing.

Also, the "million little holes" in fiberglass hulls occur at the waterline when there is no grounding system in place. A well grounded boat with a encapusulated keel leaves a single small hole through a weak point or wet point in the fiberglass. At least that's what I've read in the various studies at the University of Florida or online at the "Lightning Protection Forum". They have a good collection a marine survey reports on lightning struck boats.

Interesting note : The reason that very few boats get hit even though there is lightning striking all around the boat is that the negative "stair step" working it's way out of the bottom of a cloud doesn't become "aware" of the positive streamers coming up from the ground until it's only a few hundred feet, or less, from the ground. In essence, you are only going to take a strike if the lightning was going to hit right next to you anyway.

As a matter of personal opinion, I'm not a fan of jumper cables attached to rigging. Stainless steel is a very poor conductor of electricity compared to the mast, engine block and shaft, or the rudder post. Not only does a strike energize every piece of rigging on the boat but it allows for massive side flashes off the rigging or mast and through crew members to the wheel, tiller, or through the cabin to the engine block. Also, they can't be used while underway which is when all the really scary hits take place.


George Jones

[Ric in Richmond]

Watched it hit the surface 150 ft from the boat in the gulf stream....truly awe inspiring.

I also used the jumper cable method years ago...but had forgotten...old at 40...duh!!!

That is what I will do for now.

Has to be better than NADA!!!

[CharlieJ]

lol- compared with my wooden mast, the stainless shoruds make a pretty fair conductor.

If I needed to do something I'd clamp a cable to the shrouds, both sides, and trail chain as a temporary something. If we are sailing, the chain plates themselves, which are external, come to within an inch or so of the water or they are UNDER water anyway.

[xroyal]

Another poster elsewhere wrote a treatise about lightning traveling in straight lines. Hence, it seems to me that if you are running cables from the mast to say the keel bolts, the opportunity for side flashes/arcing below increase?

ATM, my sky is darkening for another blast of the scary stuff. As a kid in Virginia, I loved to watch the crash and bang shows. The biggest shows I ever witnessed were on my trips across the great plains...with no mountains or trees to block the giant strike views. On 3 of those cross country trips I was driving a Porsche with a very high windshield. Had trouble watching the road the storm view was so awesome.

[George ( C&C 40 )]

Hi Xroyal,


Good call on the straight line thing. You are 100% correct in that lightning likes to travel straight down if at all possible. There are lots of reports of people using the classic #4 stranded bare copper ground wire off a deck stepped mast and along the hull of the boat on its way to a keel bolt only to have the lightning burn a hole through the fiberglass as soon as it got near the waterline.

I shoud have mentioned that on #236 "Ca Ira", I used Anchor brand marine insulated boat cable in the 2/0 size and that I had made the run as straight as posible and used a keel bolt as close as directly under the mast as possible. There was one 12" section where the wire had to lay along the hull before it got to the keel bolt -- in that area I split a 12" length of heavy walled engine coolant hose and wrapped the insulated 2/0 cable in that just to make certain that the lightning didn't get any ideas about burning a hole through the hull.


George Jones

[Ceasar Choppy]

Also, the "million little holes" in fiberglass hulls occur at the waterline when there is no grounding system in place. A well grounded boat with a encapusulated keel leaves a single small hole through a weak point or wet point in the fiberglass.

I guess my point was that I would rather not have the lightning make a hole in the first place if I can avoid it. From everything I've read, a well grounded encapsulated keel boat needs a grounding strap on the outside of the hull below the water line to which mast, shrouds, grounding terminals, engine and the other metal bits are attached.

[George ( C&C 40 )]

Hi Ceasar,

A ground plate is a great idea. My only point was that an encapsulated keel isn't any barrier to lightning and that a boat set up like you are talking about is just as safe whether or not the ground plate is in place. There is some good info on this at the University of Florida's lightning protection study that was done is association with a large group of marine surveyor's. I don't remember the url at the moment but it's easy enough to find online. Cool pictures too.

George Jones


P.S. -- Oops, I just remembered that what I said about lead keels (encapsulated or not) is only true in saltwater. Freshwater boats MUST have a copper ground plate as the discharge point -- That was also in the study.

[Jedediah]

My two cents to the discussion:

The straight line bit on lightning is not really true, but rather an oversimplification of a few factors, namely the impedance in the circuit for a longer run and the potential field between the charges. I'm skeptical that jumper cables would in the end do much, mainly because of the resistance for the current in the connection to the mast. They might change the potential of an ungrounded mast before the strike but could probably not 'handle' all of the current flow and as a result you would still find current flowing other places (using handle there not for wire heating but rather electron choice). Having worked in the pulsed power field I know first hand how hard it is to predict where current is going to flow all of the time, small resistances and inductances will easily shift part of the flow to other places, even in the presence of good dielectrics, and here it helps to get it right the first time. This is where the straighter path helps the boater. Also, there are a good number of products on the market to help in high current connections (the most basic is small stainless steel grit in a dielectric grease) that when applied make sure a connection does not oxide and lowers the internal arcing while current is flowing. The interface with the water is harder, but I'd guess the larger it is, and thick, the better as that should help reduce the resistance at that point and allow it to 'handle' more current flow before it decides to go elsewhere due to an easier path.

[dkall]

Hello Dave,

Yes the copper type will be best and you will need two of them.

We do not have a distributor in the US but would be happy to deal with you direct. Door to door air freight via FedEx would be AUD113.75.

We can accept payment by direct transfer or via Visa or MasterCard. If you would like to pay via a credit card, for security, please can you fax us the details on 61 3 6273 1749 or split the details over more than one email. We will let you know when they are going and give you the tracking numbers.

If you have any queries, please let me know.

Best regards,

Geraldine L. Edwards




At 12:21 AM 14/10/2004, you wrote:
So, what you're suggesting is that I have two plates and keep them seprated by what distance? Opposite sides of the keel? I think the copper plates would be best as I've a fiberglass hull and bronze thru hulls with bronze prop and stainless shaft.

How best to purchase then? Do you have an online form? Call you? What hours?

Sincerely,
Dave Kall
Florida, USA


On Oct 13, 2004, at 12:28 AM, Moonraker Australia wrote:

13/10/04


Dear Dave,

Usually it is not a good idea to use one for both. Lightning ground should be just that so as to reduce risk to any equipment, etc., connected to it.

The E Plates are AUD136.25 each (Australian dollars). The Australian dollar is currently around USD0.73.

We have two versions: the normal copper one and an aluminium one. The aluminium one is for boats that may be subject to electrolysis if a copper one is fitted, for example if there is an outboard motor with aluminium outboard legs, etc.

I have attached an article on lightning protection which may be helpful.

If you have any queries, please let me know. You do have a lot of lightning strikes in your part of the world.

Regards,

Geraldine L. Edwards
Marketing Manager
Moonraker Australia Pty Ltd
http://www.moonraker.com.au




At 11:05 AM 13/10/2004, you wrote:

Wanting to ground a ham radio on a boat and to have a lightning ground system for the mast. Can I use one plate for both?

I'm looking at the eplate. I have a 55' mast standing about 63 feet above the water. Fiberglass vessel



Sincerely,
Dave Kall

[Ceasar Choppy]

I couldn't find any info on their e-plate on their web site... do you have a direct link? Thanks!

[dkall]

I would email them. At one time they had quite a bit of info on boat grounding systems. Don't know what happened; maybe their webmaster screwed up.

[George ( C&C 40 )]

Hi Dave,


In most cases a ham radio ground is a completely different animal fom a lightning ground. Unless you use a balanced antenna like a dipole you don't need a ground so much as you need a counterpoise.

Counterpoise construction usually consists of soldering together large pieces of copper screen in the boats hold in addition to tying together various thru-hulls. This gives the single element of a marine antenna, usually an insulated backstay, something to work against as it launches its signal. This type of system requires a very good antenna tuner and a pair of very expensive backstay insulators.

While most boaters use the insulated backstay antenna system described above you could carry a few very simple balanced dipole antenna's onboard and hoist the one you want to use whenever you felt like operating. Dipoles are nice in that they don't require anything more than a ground through a single thru-hull and they are cheap and easy to make. They also give a very good signal within their frequency range. Dipoles are a pain in that you have to hoist one each time you want to operate and they only operate in a couple of narrow frequency bands -- so you need several on board if you want to operate on many frequencies. This is the system that James Baldwin used on the famous Pearson Triton "Atom" during it's many years of touring around the world. I've also used this system a couple of times because it's cheap, easy, and doesn't require any kind of permanant installation.

The ARRL publishes a book on this subject titled "Marine Amateur Radio". You can purchase it through their online store at this link:

http://www.arrl.org/catalog/index.php3? ... 6+Portable


Good Luck,

George Jones

C&C 40 "Delphinus"
KG4RGM

[Ceasar Choppy]

I would email them. At one time they had quite a bit of info on boat grounding systems. Don't know what happened; maybe their webmaster screwed up.

Thanks! If the e-plate is anything like a dynaplate for SSB, then I'd shy away from it for a lightning ground. Word has it that the sintered bronze used in the Dynaplate can theoretically explode (although I've never heard of this actually happening). The theory goes that since water gets in and around the tiny sinters (which makes a plate like this small and effective by increasing overall surface area in a small space), if it takes a lightning hit, the water around the sinters can heat up to such an extreme that it will go "boom".

[krissteyn]

What about :-

am about to buy another (glass) boat and was thinking of attaching a stainless steel or copper strip to the long keel to act as a "protector" - Assuming it wasnt connected to anything else , ie attached via epoxy & small screws , could I attach a cable from the mast to this strip ? and thus use it as a ground ? The dolpin striker would be a perfect place to attach it ???

kris

[dkall]

The e-plate is NOTHING like the dynaplate. More like bronze thru hulls in materials.

[dkall]

http://www.moonraker.com.au/techni/earth.htm

[Ceasar Choppy]

so its solid bronze, not sintered? Hard to tell from the pics.

[dkall]

quite solid. Definitely not sintered. And pretty good size. The company emailed me quickly when I contacted them so you may want to email them and ask away.