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Old 18-07-2008, 16:51   #1
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Lightning Protection

This topic came up on another forum, but since it is such a major problem, especially for multihulls, that I thought it was worth posting here as well.

I suspect that more cruising multihulls are hit by lightning than capsize. But who thinks about the former before going offshore?

Anyway, this is what I wrote

"First visit Marine Lightning Protection Inc.

see the photo on the home page of a catamaran sunk after being hit by lightning, June 20th 2008

Then go to Strikeshield Lightning Protection Systems for Sailboats — Strikeshield Lightning Protection Systems for Sailboats

For the solution that I used after being hit.

Sail in the tropics in the wet season or on the east coast USA right now and you will hear dozens of stories of lightning strikes. With "luck" you'll even be hit yourself.

I sailed up the east coast of the USA in 2003 and met 2 other English boats doing the same. All three of us were hit by lightning.

Later in Panama we were anchored with a group of 12 boats. In one storm 6 were hit. Not us, we had a Strikeshield system fitted, or were lucky.

I write more about my own lightning strike on the article pages of my website"


Woods Designs Sailing Catamarans

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Old 18-07-2008, 17:19   #2
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A great moment to post this, as I have had dozens of strikes within half a mile and one on "those rocks over there" in my anchorage. Sitting on the floor right now, feeling like I should turn off the computer.
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Old 18-07-2008, 20:35   #3
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Later in Panama we were anchored with a group of 12 boats. In one storm 6 were hit. Not us, we had a Strikeshield system fitted, or were lucky.

Richard Woods of Woods Designs
Richard,

You were lucky. The Strikeshield is not a lightning protection system and doesn't lower your chances of being hit (it might even slightly raise them). Instead, it is designed to direct a hit to ground through a well defined and controlled path and, hopefully, spare collateral damage to the boat and its equipment.

We also have one installed on our catamaran.

Mark
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Old 18-07-2008, 22:07   #4
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I agree that it isn't a lightning protection system. The phrase Strike Shield Protection System appears on the posting as that is what this forum thinks I write when I write strikeshield dot com. Ie, that is what the Strikeshield put as their own website index page title.

It is the same with my website, below. I actually write sailingcatamarans dot com, but as you can see that isn't what appears.

Richard Woods of Woods Designs

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Old 19-07-2008, 11:01   #5
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Mark,

did you ever try to have the strikeshield installed during sailing. I.e. reducing speed to minimum practical?
I could imagine, that the copper cable is bouncing around?
Had no chance to try out myself, still on job in Germany.

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Old 20-07-2008, 07:53   #6
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What about "lightning diffusers" (or something like that). they look like a steel brush mounted at the masthead. I heard they diffused the concentration of charge and made a strike less likely. It seems to me that deflecting a strike altogether would be vastly preferable to chaneling it through the rig to the water. Do these work?
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Old 20-07-2008, 09:05   #7
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I had that device mounted on my MORGAN 41. Coming back to the boat one day, this "brush" looked a little strange,
Guess what, we had a nice lightning strike with lot of damage.
But how to prove, that it maybe had prevented a lightning strike before?
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Old 20-07-2008, 09:50   #8
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A long time ago an old salt told us to clip jumper cables on the upper stays and let one end hang in the water with about 6" of bare wire exposed during lightning storms. Living aboard on the Chesapeake during the summer and many years in south Floriduh any time and being often in the Caribbean we have done this over the years. I will not argue the science of this but we have either been really lucky or it has worked in some sense. The idea is not to prevent the strike, but get it directly to the water without passing through too much of the boat. But it sure is cheap to install.
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Old 20-07-2008, 10:40   #9
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Quote:
I will not argue the science of this but we have either been really lucky or it has worked in some sense.
I wouldn't consider not getting struck by lightning being lucky. I've never done anything and have never been hit. That would also include all the time spent off the boat too. Some events don't happen that often. Lightning would be one of them. You see it often but it does not miss you for a reason.
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Old 20-07-2008, 18:22   #10
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Another related question: carbon versus aluminum masts. I've heard that a lightning strike to a carbon mast might destroy it. anyone with experience?
Rocky
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Old 20-07-2008, 18:50   #11
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A long time ago an old salt told us to clip jumper cables on the upper stays and let one end hang in the water with about 6" of bare wire exposed during lightning storms. Living aboard on the Chesapeake during the summer and many years in south Floriduh any time and being often in the Caribbean we have done this over the years. I will not argue the science of this but we have either been really lucky or it has worked in some sense. The idea is not to prevent the strike, but get it directly to the water without passing through too much of the boat. But it sure is cheap to install.

If it works for you, great but I think the charge will travel faster down the mast and into the boat than down the stainless shrouds. I have resorted to praying.... and have not been struck since doing this. I never prayed till I got hit in 1995. Once you've been hit while while sailing you'll become a convert to praying.
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Old 20-07-2008, 20:22   #12
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Mark,

did you ever try to have the strikeshield installed during sailing. I.e. reducing speed to minimum practical?
I could imagine, that the copper cable is bouncing around?
Had no chance to try out myself, still on job in Germany.

Regards

Ralph
Hi Ralph,

Fortunately, I have never had close lightning storms while sailing since I installed it. So I don't have any experience with how it reacts. It's pretty heavy, so I think it would just drag smoothly along toward the top of the water without bouncing too much. Sort of like dragging some chain overboard.

Mark
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Old 20-07-2008, 20:26   #13
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Another related question: carbon versus aluminum masts. I've heard that a lightning strike to a carbon mast might destroy it. anyone with experience?
Rocky
On another forum, a denizen reports that he received a direct hit to his carbon mast on a trimaran. He had a lot of damaged electronics and melted antenna, but no damage to his mast, boat or rigging.

Mark
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Old 23-07-2008, 21:28   #14
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Several weeks ago a brand new, never used 15 meter cat suffered a direct strike 100 meters from my boat. The lightning hit his carbon fibre mast setting it on fire, blowing the never used radar off the mast and blowing a 1 meter wide hole in his bridge deck. The strike took out all electronics and destroyed his $100K mast. I could not find any physical damage to my boat, but the lightning also destroyed my sonar, radar, autopilot, VHF, HF, wind instruments and blew most of the LED's on my electrical display panel. Neither yacht had lightning protection and my shore power supply was also damaged onshore. Although cats have a higher chance of getting struck, I am still contemplating whether it is worth the expense and hassle of installing some form of grounding system be it temporary or permanent. Lightning is common in my area, but the local marine electronics man said he has only dealt with 3 other lightning strike cases in 25 years. What are my chances of getting hit a second time?

What are the Chances of Lightning Striking Your Boat?
The following statistics are based on all of the Boat US Marine Insurance claims for lightning damage over a five-year period. The percentages suggest the chances of the various types of boats being struck in any given year.
Auxiliary Sail 0.6% Sixty out of 10,000
Multi-hull sail 0.5% Fifty out of 10,000
Trawlers 0.3% Thirty out of 10,000
Sail Only 0.2% Twenty out of 10,000
Cruisers 0.1% Ten out of 10,000
Runabouts 0.02% Two out of 10,000

BTW: Thunder is more than just a rich source of loudness (audible up to about 25 miles).
It can also tell you interesting stuff, such as how close you came to being hit by lightning.
Since light travels at 186,000 miles per second, you see the lightning the instant it flashes. But sound, including thunder, travels about a mile in five seconds (1000Ft/Sec, 340m/sec) near the ground, at normal temperatures.
Lightning closer than about three miles away is a warning to take shelter immediately. Successive lighting strikes are often two to three miles apart. If the first stroke is three miles away, the next one could hit you.
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Old 23-07-2008, 23:07   #15
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Given lightning can arc across miles of sky and air is a relatively poor conductor, lightning finds it quite attractive to continue its path to earth through a better conductor than air...such as your mast. It makes perfect sense to provide an excellent conductor like a copper wire to help lightning continue that path to the earth. This is opposed to ever thinking that any sort of shield could be created which diverts these free electrons away from your boat, when your mast is such an attractive conductor compared to air. Nothing is going to shield your boat from lightning when your boat is a better conductor of electrons than the surrounding air.

The product "Strikeshield" sounds like an excellent product...it just has a misleading name. Its not a shield in any way, its more like a pathway. I think "StrikePathway" would have been a better name actually.
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