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Old 23-09-2009, 09:31   #1
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Cats Twice as Likely To Be Struck by Lightning ?

I've just followed a link from a blog to this website which states that:

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[catamarans] are struck [by lightning] twice as frequently as monohulls of similar length
The website sells marine lightning protection equipment too, so it may all just be a marketing ploy. I must admit, I've not heard anything like this statistic before. I won't be losing any sleep over it, even if it is true, but are cats really more likely to be struck by lightning? I'd have thought side-by-side the mono would be more likely to be hit (probably a taller mast and better grounding through the keel).
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Old 23-09-2009, 09:49   #2
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Did you find that on my blog, because I just posted the link to that page this morning! It's not great news if it is true but it doesn't mean we'll be selling our cat and buying a monohull.
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Old 23-09-2009, 10:09   #3
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Hi Mike!

Welcome to Cruisers Forum

Yes I just read your post on your blog and followed the link. If you were about to post anything similar here let me know and I'll delete my post.

Regards

Keith

PS I just left a comment on your blog too
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Old 23-09-2009, 10:27   #4
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Doesn't make a lot of sense to me (from the physics standpoint)
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Old 23-09-2009, 10:41   #5
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I think the original claim was from the Boat US magazine that cited their insurance statistics.

Fair Winds,
Mike
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Old 23-09-2009, 11:05   #6
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And its important to remember that cats are at the end of the dock, not surrounded by a bunch of other masts. Understand that its ridiculous to draw any conclusions from so small a sample, particularly since BOAT US had a policy of NOT insuring catamarans for many years, and their sample, as a result, is meaningless.

IMHO there is nothing that has been objectively proven to prevent lightning strikes. Every device ever installed has on one or more occasion failed. Old standards have been thoroughly debunked, and authoritative organizations have "revised" their previous endorsements. New products just haven't been around long enough for that to happen YET. If nothing else, this makes for a ripe market for charlatans and well-meaning experimenters. Its like radar reflectors. Bogus.
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Old 23-09-2009, 11:41   #7
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Its like radar reflectors. Bogus.
Radar reflectors are bogus? Really? Damn it. Another thing I didn't know! At the risk of hijacking this thread can you cite some source that I should be reading on this, because I see a lot of boats with radar reflectors installed. We even have one on our boat (not installed).
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Old 23-09-2009, 12:29   #8
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Quote:
Originally Posted by mikeandrebecca View Post
Radar reflectors are bogus? Really? Damn it. Another thing I didn't know! At the risk of hijacking this thread can you cite some source that I should be reading on this, because I see a lot of boats with radar reflectors installed. We even have one on our boat (not installed).
I suspect that this is a partial generalisation!

There is some truth in this, in that there are items sold as radar reflectors that achieve less radar echo area, than your mast!

However, there are also equipments that have been scientifically designed to achieve specific measurements, and then tested by military research facilities. The first of these was the old octagonal radar reflector - that ugly multicornered hunk of metal that is a pain to erect and takes up a lot of space. The firdell blipper revolutionised the radar reflector business and achieves a reasonable echo. The Echomax is a newer one that is apparently slightly better.

These three are the best of the standard reflectors. There are also a few special systems based on the properties of the luneberg lens. I have seen one that sits at the top of the mast and has 3 balls. This should work quite well on a cat, but I believe struggles on a mono when tipped well over.

I do not know of any others that are worth the paper they are wrapped in, but there may be one!
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Old 23-09-2009, 12:32   #9
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[QUOTE= particularly since BOAT US had a policy of NOT insuring catamarans for many years, and their sample, as a result, is meaningless.

They insured my cat from 2000 until 2007, and others.
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Old 23-09-2009, 12:33   #10
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Wonder why cats would be hit more often?. What are the stats?./Harry
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Old 23-09-2009, 12:35   #11
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Mike, I seem to recall a test (perhaps in practical boater?) wherein certain radar reflectors did create a bigger image on the radar screen of approaching vessels. Nevertheless, as Sandy points out, they are much less effective than many think (and of course, depend for their utility on someone actually being on the bridge of a ship who is paying attention to a small blip).

As to lightning protection, there are some systems which claim to provide protection by effectively distruibuting the discharge in the sea around the vessel; Richard Woods certainly believes in their utility. However, as Sandy says, there is no scientific proof and there is even some debate about whether improved grounding may actually increase the likelihood of a strike.

As to catamarans being more susceptible to strikes, Sandy is again absolutely correct. Not only is the sample small, not only are cats often docked apart from other boats/at the end of docks, but in North America (where Boat US operates) they are also more likely to be sailed in areas with a greater frequency of thunder/tropical storms. As you are aware, cats are extremely rare in the great white north; in Florida and the Caribbean they have become quite common. Put a much greater relative percentage of one type of boat in lightening prone areas and the results would not be difficult to predict.

The problem, therefore, is not with the design of the boats, but rather the conclusions that Boat US has attempted to draw from their limited claims. Lightening strikes can cause catastrophic damage (no pun intended) to your boat, whether it is a cat or a monohull. Indeed, there was an Alberg 30 moored in Kerr Bay (an area that you are familiar with) that was struck by lightning 3 years ago; it blew the thru-hulls out of the boat and it sank. At least in your cat you would have remained afloat.

Brad
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Old 23-09-2009, 13:10   #12
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Originally Posted by S&S View Post
Doesn't make a lot of sense to me (from the physics standpoint)
I'm sure Dr. Thomson will be devastated when he learns of your disdaine.

Ewen Thomson is a former research scientist at the Univ. of Florida (specialized in lightening protection research) until 2004, when he formed his own company (Marine Lightning Protection Inc). He’s been the author of several respected papers on the subject of Lightning & Boats, and was instrumental in ammendments to the Lightning Protection codes.

http://www.kp44.org/LightningAndSailboats.php

http://www.kp44.org/ftp/A_CriticalAs...Boats_IEEE.pdf

Catamarans


Quote:
Originally Posted by mikeandrebecca View Post
Radar reflectors are bogus? Really? Damn it. Another thing I didn't know! At the risk of hijacking this thread can you cite some source that I should be reading on this ...
Probably not, because radar reflectors DO work, with varying efficacies.

Report by QinetiQ:
“Performance Investigation of Marine Radar Reflectors on the Market”
http://www.westmarine.com/images/wa/...ors_report.pdf
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Old 23-09-2009, 13:41   #13
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As Gord points out, Dr. Thomson is definitely NOT a quack. He is both a sailor and a professor of Electrical Engineering. While lots of us can say we are the former, how many of us can also say we're the latter? In a field that is probably one of the most difficult areas of the physical sciences in which to do reliable and valid experiments, he has done more than anyone else in trying to understand the interactions between boats and lightning. As he readily acknowledges, he doesn't understand it all and weird things happen with lightning. However, he is trying to bring as much science to it as can be brought.

So, please, don't scoff at his work.

In terms of radar reflectors, all I have to offer is my own experience. I've had several boaters, as well as the deck officer on a freighter, ask me for the brand of our reflector. The deck officer told me that it made our sailing cat look as big as another freighter on his radar. I definitely liked hearing that! It is an Echomax 230 -- looks like a white barrel, 6-8" in diameter, mounted about about 20 feet up the mast.

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Old 23-09-2009, 13:42   #14
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Originally Posted by GordMay View Post
I'm sure Dr. Thomson will be devastated when he learns of your disdaine.

Ewen Thomson is a former research scientist at the Univ. of Florida (specialized in lightening protection research) until 2004, when he formed his own company (Marine Lightning Protection Inc). He’s been the author of several respected papers on the subject of Lightning & Boats, and was instrumental in ammendments to the Lightning Protection codes.

Lightning Protection - Lightning and Boats

http://www.kp44.org/ftp/A_CriticalAs...Boats_IEEE.pdf

Catamarans
Not distain, merely a healthy skepticism. For a given mast hight H the cone of protection has a circular projection on the water. Unless there are projections outside of the cone, (short stick) the strike probablility between a cat and mono should be the same. Soooo, there must be another variable (boat placement in a marina, for example) that gives rise to the different stats. Note that the third site you list does not provide any math that would make one think otherwise. The first two were interesting.



I'm sure you'll agree that citation of authority is not a substitute for critical thinking.
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Old 23-09-2009, 13:50   #15
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Cats twice as likely to be struck by another boat

... from behind or ahead,... they are twice as wide! Now I'll sit back and watch the show
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