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Old 27-11-2014, 23:08   #1
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Lightening protection on a cat

Lightening rod
Hello, everyone!
I posted this under Electrical etc. Forum, but got only 2 replies... and was hoping someone here might have a simpler solution to this problem:

I am an aspiring Cat-sailor (she's being build as I write - delivery in April'15).
I haven't had much experience (Did a coastal skipper course a few years back) and trying to find my way around as a live-aboard single-handler).
I read the other day in this forum about a lightening strike on a boat that destroyed all fuses and some systems, and almost got the skipper who was working on his engine.
My question is: There must be a way to have a lightening and surge protection system installed at the mast which then "guides" the electricity into the water?
Has anyone experience with this? I am sure the insurance company would be happy....
Please let me know and thanks in advance for your advise.
Cheers!
Thomas
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Old 28-11-2014, 02:24   #2
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Re: Lightening protection on a cat

Fire Pig,

You posted in the correct forum ie Electrical. And one of the replies referred you to where you will find all the information you will need to understand what you need to do to protect your boat. That site happens to be by one of the world leading authorities on this subject, Prof. Ewen Thomson, and the info he presents is straightforward and well explained. There is no "simpler solution to the problem". If you are looking for a 2 line explanation of this, you will be disappointed.

I am currently also researching this subject for catamarans, so after you read the information on that website, you can come back with further questions and I'd be happy to respond. But do the minimum work first, at least. The good news is it's actually really interesting stuff.

That site once again is Marine Lightning Protection Inc.
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Old 28-11-2014, 02:40   #3
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Re: Lightening protection on a cat

Thanks, BigBeaky! I appreciate your reply and reference and I have actually read the article!
So, on a cat, you don't have a keel, so where to connect the arrester to? Just to the plates at the water line? This MUST be a big problem for everyone on a boat, but you hear very little about it. And insurance companies treat it as "Act of God" and don't pay? Frightening issues!
Is it possible to switch off ALL electrical systems when you run into a thunderstorm?
Thomas
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Old 28-11-2014, 05:57   #4
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Re: Lightening protection on a cat

Insurance companies pay up for lightning damage. At least all that we have dealt with do so. In fact, our current insurance actually waives the deductible for lightning damage.

There is no system that will prevent lightning or guarantee full protection of your boat and equipment. The best one can hope for is to direct a strike to ground in a manner that doesn't have it doing physical catastrophic damage to the boat structure, and possibly to protect electronics and electrics enough that a weak or close indirect strike doesn't take them out.

Switching off electronics may help protect them from an EMP of a near hit, but they would have to be completely unwired to have much hope of surviving a direct hit.

There are surge protectors and voltage clamping devices that go a long way toward protecting electronics and electricals, but these are expensive, need to be installed on each individual piece or circuit, as well as the whole panel, and have difficult installation issues on boats.

For many cruising areas, lightning is a rare event and worrying about its low probability is like worrying about crashing every time one gets on an airplane. Unfortunately for you, Malaysia is not one of those areas!

If there were any solid protection/prevention systems known, insurance companies would require them or give discounts for having them. I don't know of any of these insurance companies.

The best lightning protection is a good insurance plan. Once that is acquired, taking some simple steps to ground/bond the boat for lightning is a good thing. One can go to extremes with Ewen's electrode system and surge protection on everything, but the cost and bother of a retrofit is probably higher than the probability of a strike - even in Malaysia.

Mark
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Old 28-11-2014, 07:10   #5
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Re: Lightening protection on a cat

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Originally Posted by colemj View Post
If there were any solid protection/prevention systems known, insurance companies would require them or give discounts for having them. I don't know of any of these insurance companies.
Mark is right - again.

I suspect lightning strikes or near strikes and the resultant frying of electronics is the single biggest category of sailing vessel insurance claims and payouts. Even if not the biggest, insurance companies have huge incentive to minimize these payouts and seek what works to lessen them. Bottom line - nothing works definitively (well almost nothing - see below). The really bad news is that insurance companies seem to be resorting to their other tried and true strategy to lessen payouts - minimizing coverage for lightning. My policy recently was renewed and in the fine print the former $500 deductible for damage to electronics due to lightning was removed. Now the deductible for any lightning damage is the same as the overall deductible.

I expect my boat to suffer a strike sooner or later. I'm amazed it hasn't happened already. But it won't happen before next September because I've taken the mast down - in part to avoid lightning strikes during the spring and summer next year while we take this winter off for extensive refit.

2 Hulls Dave
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Old 28-11-2014, 09:22   #6
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Re: Lightening protection on a cat

I have to take issue with the responses. A number of years ago we arrived in Durban, South Africa, after a long passage. We had only been there a short while when the interior of our cat lit up with an eerie purple blue light. We lost some (not all) of our electronics - and the insurance company replaced the damaged items. Items such as our SSB etc are always physically disconnected when there is bad weather. I was concerned about a repeat and asked around, in Durban, about lightning protection and subsequently purchased a lightning dissipator. It is all stainless steel and looks a bit like an oversized upside down toilet brush. Apparently, it is intended to ensure that the electrical potential of the mast is equal to the surrounding air mass and thereby reduce the possibility of a lightning strike. Since fitting it (several hours job as I had to reposition other mast head kit) we have experienced no issues despite other nearby yachts, with shorter masts being struck. When I bought the dissipator I was advised that the South African electricity distribution company were fitting these to their tranmission towers and that the development, design and patents were actually of Canadian origin - also from an electricity company.
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Old 28-11-2014, 12:38   #7
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Re: Lightening protection on a cat

I'm sure it's not as effective as the measures on that website, but I read a while back you could get pretty good lightening protection from a set of jumper cables.
  1. Split the pair into two separate cables
  2. Cut the clip from one end of both cables.
  3. Strip the insulation on the cut end, baring about a foot of copper.
  4. Clip a cable to the bottom of each shroud, and let the bare wire dangle in the water.

Fact or myth?
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Old 28-11-2014, 12:45   #8
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Re: Lightening protection on a cat

It actually makes sense if you are not moving - the strike needs to get to earth by the easiest route and you would have provided that by this method. Only I would leave the crocodile clip on both end and perhaps add a weight in the clip that is over board. Of course it is preferable if your shrous are outboard and perhaps should add also the forestay if possible. Its cheap enough to try! Meanwhile I shall still retain my dissipator (I need to track down a replacement). Cheers.
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Old 28-11-2014, 21:34   #9
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Re: Lightening protection on a cat

FirePig,

You get the charge from the mast to the water by having some system to put a fairly long metal metal strip into the water. In my case our mast base is back further than most cats, it is over the saloon, so the base of our mast with be grounded down through the mast compression post in the saloon using massive aluminium scrap 1" cable (with an insulated outer case for the mast compression post as it passes through the saloon) and connects under the bridgedeck to the long copper strip. The strip is 3mm thick so that there is a definite 90 degree edge, it is the edges where the charge dissipates from. And it deploys from the cockpit where it can be released and pulled back up under the bridgedeck.

With Mark's comment that Ewen's solution with the Sidearc conductors is going to extreme's, I have to differ here from Mark's usually impeccable advice. It is not that hard to install especially in the new build when the conductors can be laid & Sidearc conductors installed easily.
I do, however, agree that putting his suppression on each circuit and specifying it to each specific type of electronic device is getting to the extreme end of the scale.

We will be constructing a Faraday cage section of our forward facing nav station that will house all the critical electronics, and there will be quick disconnects and/or easy access to wires, antennae cables etc to physically disconnect the electronics from a source of surge.

We reckon it's the best we can do to follow Ewen's system at reasonable cost and installation effort.

The idea that you just let the insurance replace everything is OK except if you cruise in quite remote regions, of course. If your coastal cruising all the time in civilisation, that's another matter.
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Old 29-11-2014, 06:47   #10
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Re: Lightening protection on a cat

Quote:
Originally Posted by BigBeakie View Post
With Mark's comment that Ewen's solution with the Sidearc conductors is going to extreme's
I didn't mean to say that Ewen's system was going to extremes - I meant to say that that system was the extreme of lightning protection. In other words, on a scale of protection measures, "none" would be at one extreme and Ewen's would be at the other end. There are lots of partial protection measures in between.

I also meant to imply that his system is best considered during a new build, as the hassle and possible expense of retrofitting one can be high.

Mark
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Old 29-11-2014, 07:00   #11
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Re: Lightening protection on a cat

Quote:
Originally Posted by edneely View Post
I'm sure it's not as effective as the measures on that website, but I read a while back you could get pretty good lightening protection from a set of jumper cables.
  1. Split the pair into two separate cables
  2. Cut the clip from one end of both cables.
  3. Strip the insulation on the cut end, baring about a foot of copper.
  4. Clip a cable to the bottom of each shroud, and let the bare wire dangle in the water.

Fact or myth?
that would make more sense to me than another suggestion I had seen about doing something similar with chain. I was thinking that a dangling chain would be about the epitome of loose ground connections. In series.

If this idea worked, I would wonder why someone hasn't extended the external hull components of their chain plates down to below the water line.
There are catamaran designs where the forestay is mechanically connected to 'dolphin strikers', already pretty close to the water. If connecting chain, fore, and aft stays ( Faraday cage) to the sea water outside the hull would protect the boat, wouldn't this be the common practice by now?

And wouldn't this make steel and aluminum boats immune?
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Old 29-11-2014, 07:16   #12
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Re: Lightening protection on a cat

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Originally Posted by Canibul View Post
that would make more sense to me than another suggestion I had seen about doing something similar with chain. I was thinking that a dangling chain would be about the epitome of loose ground connections. In series.

If this idea worked, I would wonder why someone hasn't extended the external hull components of their chain plates down to below the water line.
There are catamaran designs where the forestay is mechanically connected to 'dolphin strikers', already pretty close to the water. If connecting chain, fore, and aft stays ( Faraday cage) to the sea water outside the hull would protect the boat, wouldn't this be the common practice by now?

And wouldn't this make steel and aluminum boats immune?
Unless you give credence to the argument that in providing a clean shot to ground that you're creating a juicy target for the lightning. Remember, the "attraction" here is a route for the positive charge above to the negative charge below. The potential will choose the most available circuit. I don't know enough to support or refute this argument. But it could be that providing a clear path to ground, while it may invite a strike, may also minimize the consequences when the strike occurs. But this doesn't necessarily mean no consequences as your electronics will likely still get fried.

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Old 29-11-2014, 07:28   #13
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Re: Lightening protection on a cat

Alligator clips aren't a good connection, and a shroud is a poor connection point. To be useful at all, the mast itself must have a robust connection to ground.

Attached are pictures of our setup. It consists of a thick tinned copper plate permanently connected to the mast, a removable 4/0 wire that has a strong, thick connection mechanism to the mounting plate and is terminated with a tinned copper electrode. The whole thing drops into the water through the trampoline almost directly underneath the mast, with a slight large radius bend to bring it to the tramp.

The electrode is machined to have 9' of sharp edge surface, as well as a point on the end (sorry, the picture is poor and doesn't show this well). As someone else eluded to, lightning likes to exit edge or point surfaces. Simply putting the end of a wire into the water won't be sufficient.

Shrouds have chain-like connection points and are auxiliary to the mast itself. While lightning can go through them, it would not be wise to rely on the strike leaving the mast itself to preferentially travel down one shroud to ground.

Mark
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Old 29-11-2014, 07:35   #14
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Re: Lightening protection on a cat

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Unless you give credence to the argument that in providing a clean shot to ground that you're creating a juicy target for the lightning.

…...
But it could be that providing a clear path to ground, while it may invite a strike
Believe me, if I could find a single piece of evidence that showed this, I would be pulling our grounding system immediately. I have found a few studies and actuarial statistics that show grounded boats do not attract lightning or increase the chances of being hit. Some of these suggest that the chances of being struck are slightly lower with a grounded boat (something to do with bleeding off charge buildup).

The only accounts stating the opposite are lay people saying so on docks and the internet - and their entire body of knowledge and experimental evidence consists of personal beliefs and anecdotal stories. The vast majority of it consists of "my boat isn't grounded and I have never been hit", or "I know of a grounded boat that was hit".

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Old 29-11-2014, 08:27   #15
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Re: Lightening protection on a cat

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Originally Posted by colemj View Post
Believe me, if I could find a single piece of evidence that showed this, I would be pulling our grounding system immediately. I have found a few studies and actuarial statistics that show grounded boats do not attract lightning or increase the chances of being hit. Some of these suggest that the chances of being struck are slightly lower with a grounded boat (something to do with bleeding off charge buildup).

The only accounts stating the opposite are lay people saying so on docks and the internet - and their entire body of knowledge and experimental evidence consists of personal beliefs and anecdotal stories. The vast majority of it consists of "my boat isn't grounded and I have never been hit", or "I know of a grounded boat that was hit".

Mark
My two personal experiences with lightning in 2012, and all my other information and opinions on this tell me that you're doing it right. If you are directly under the ideal spot for lightning to form, you're already part of it's direct path to ground. Lightning forming a mile up and a mile and a half away has a more direct path straight to the water. So the best thing you can do is to try to predetermine the path that the majority of the energy is going to take through your boat if it happens. And timing is important in a moving storm, too. You're a potential path because your boat as an overall entity is less resistance than air. And can be an electrode. The boat becomes that pointy end that lightning seems to like. As for controlling all the energy, well, we can't yet. A solid copper mast extending thru the keel? But if you provide a quick path that can handle most of the main bolt of energy, the radiant and capacitively coupled pulses and spikes have less energy. Meaning they don't leap as big a gap, nor vaporize the same masses of minor resistance. This means less damage, and there are things you can do to minimize the already minimized damage.
For those who claim not to have a grounded boat.....wait just a second. I've been crawling all over mine lately, the new zincs leaked when we launched it Wednesday. I got ground strap on the brain at the moment. And go take a close look at your engine and propshaft. If it's like both of mine, there is a direct cable from the battery negative to the engine block. Your alternator is grounded to the block. There is another ground wire from the block to the stud for an external zinc anode which is also connected to the factory installed wide copper strip that runs all the way around each hull just below the waterline. There is another ground connector from the stuffing block to the zinc and copper strip. Therefore, anything on that boat that uses the 12 volt system is grounded to the seawater at the negative battery terminal, which is also connected to zincs and prop shaft. The braided jacket of the coax cable running to the VHF antenna on the mast, is therefore directly tied to the seawater. And the grounds for the tricolor, wind instruments, radar, steaming light, anchor light, ...loud hailer? So your mast is, indeed, grounded unless it's wooden or fiberglass. Or unless you have electrically isolated your VHF radio mount from the aluminum mast, sufficiently that lightning will ignore a path a fraction of a millimeter away.

Mark, what's happening to the aluminum of your mast where the copper is attached to it? I seem to keep learning the hard way that any two metals of different properties at all will have some reaction when in physical contact in the presence of salt spray. Even two different aluminums in a storm window. Electrons seem to flow, and aluminum seems to suffer if there's no zinc to take the fall. You've got three metals together there at that point, aluminum, copper, and the fastener. Looks like an ideal setup for electron orgies.
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