Lightening protection on a cat

[2Hulls]

Originally Posted by Helia 44

Anyway, my system worked, ...

In what way did it "work"? Your boat got hit and nothing happened? Or it didn't get hit? Or what?

2 Hulls Dave

[Roy M]

Hmmm. My mast stands atop a 1/2" stainless steel "bridge", which spans the opening of my centerboard trunk. I have often considered attaching, robustly, a flattened 1 inch copper pipe from the base of the mast, which then passed straight down the trunk to the bottom of the keel shoe, then to a copper plate fitted in the flat bottom of the keel. The distance is about four feet from mast base to keel shoe. That takes care of the route, with considerable current capacity.

My fear, however, is that the improved routing of current might endanger those of us in the center cockpit of my Searunner 40 trimaran. I'm caught in a decision loop. Boost the ability to conduct current directly into the water, without hull penetration, AND THEREBY increase the possibility of a side arc to the helmsman or crew cowering behind the dodger. It's a dilemma. And not one, I'm afraid, any of this informed body will be able reassure me of. I may have to purchase a plastic Jesus for the cockpit.

[colemj]

How does bonding the mast straight to ground increase the possibility of a side arc over that of the lightning just going in random directions from the mast to get to ground?

Mark

[BigBeakie]

Also a note about how lightning actually earth's out. It seems from photographic evidence that the charge is discharged on the surface of the ocean, which is why Ewen Thomson puts the Sidearc conductors at the waterline. So not sure directing the current to the bottom of a keel is effective.

I have read where mono's have been hit and had the mast grounded directly to keel with a large conductor, and the lightning jumped across the boat and blew out bronze seacock. Which seems to validate the idea that lightning wants to get to the sea surface.

Which brings me to my doubts about the dangling chain idea that "stops" the lightning in it's tracks when a link is blown by the huge amperage. It seems to me, as Cotemar has pointed out, that lightning is not something that you can stop with what is, in effect, a chain link fuse. Lightning, unlike house current at 110 or 240volts, where fuses work quite well as we all know, can be many millions of volts and many thousands of amps, all delivered in about 30 miliseconds. That is a helluva lot of energy determined to get to ground, and is fundamentally different than the household current/voltages scenario. In fact, it is very determined, and will do some amazing things to get to ground.

The idea that a broken link in a chain is going to persuade all that energy to just give up, doesn't make any sense to me. I wish it was that easy, because easy is good, but from all the reading I have done and conversations with electrical engineers, I think at best, the lightning would jump from the broken link to the water. But chain appears to be a poor conductor for this purpose. If the links ARE blowing up, it means it is acting as a resistor. Lightning doesn't like resistors, it likes conductors, and it makes that decision in miliseconds if not microseconds.

Maybe it would be better with big cable that has more surface area, which is the critical factor. The challenge is getting a good conducting path in as direct a line as possible to the waters surface. In fact, many conducting paths is even better.

I like the idea of trying to keep that path on the outside of the boat, which is the one thing that worries me about the Sidearc system that earths the shrouds to the Sidearc conductors via cables that are inside the boat. But unlike the dangling chain idea, the Sidearcs are there and ready to take the hit at any time, even in the middle of the night when that thunderstorm rolls in.

[cwjohm]

More importantly, this dude was hit 17 times in 10 years. Most people do not get hit in their lifetime. It sounds to me like his boat was configured as a floating lightening rod.

[Helia 44]

Yes it was, I mean: It sounded like he set himself up to be struck as part of his R&D

He was a wealthy Man with his yacht and Business as a Consultant, and Designer for skyscrapers, I was privileged to have him come to my aid. FOC.

I think his purpose was to test methods of being hit, and surviving with little or no damage. Bonding to thru hulls, blows holes in boats... Bonding masts to bonding systems and keels and bronze plates, caused huge internal arcs, and could blow holes in boats. His biggest point was to keep the lightening out of the interior, and in his experience the surge liked more straight lines to ground from upper and lower shrouds. He was in the big money for his experience.

I am not going to argue the points, or be in this any more. This is my last comment on this Thread. I was only sharing what he helped me with, and I was impressed. The fused link comment someone made was way below the threshold necessary and would not work at all. The fused link had to be so massive as to conduct the surge, and then break with only the micro-resistance relative to the strike, between the chain links, and the fuse link to blow out was massive in terms of any fuse made by man. This is a massive fuse link, that blew under mid strike surge to break the lightening strike, the way he described it to me, he was the Professional, we are just speculating as inexperienced Laymen....

I am going with what he said, a Self Made Millionaire in R&D on lightening arrestors and systems and skyscrapers design. I only shared this, as it could save someone's Life. I was one of those thinking of internal bonding systems to all thru hulls, but after he told me how he had seen whole interiors of boats that had been blasted and burned out by internal systems in his investigations, I am not into any internal bonding for lightening any more.

I have seen chain lightening in a black wall of cloud moving down the warm current flow, of constant lightening running from horizon to horizon, with a Mason 48 being pushed so hard to stay ahead of it that I was throwing a rooster tail of water up one side the transom with her gunnel in the water and every stitch of sail up on a cutter rigged ketch 57' from bowsprit to boomkin and a 71' main spar in the air... I just managed to stay ahead of it when the U.S. Coast Guard reported some phenomenal 1200 strikes per hour in the black wall of the front moving down the Gulfstream current.. I hope you never see that kind of a day, it is terrifying.. Luckily I outran it, and I hope you never see it..

Good bye on this thread and good luck to all. Helia 44, "Avalon"

[Roy M]

Originally Posted by colemj

How does bonding the mast straight to ground increase the possibility of a side arc over that of the lightning just going in random directions from the mast to get to ground?

Mark

Beats me. Can you guarantee that things work out the way they SHOULD? For the moment, the plastic Jesus is appearing a better decision. Maybe I should make an altar with several available deities, including Billiken, the true god of things as they ought to be: Billiken - Wikipedia, the free encyclopedia.

[cwjohm]

Just make sure Billiken is made of superconducting material and you should be right

[Emmalina]

Having taken a massive hit twice ! I believe there is little true protection. We have a lightning conductor and 2 grounding plates. Still we managed to burn our rudder and genoa not to mention everything else. Good insurance is my recommendation !