Lighting strike likelyhood

[Paul L]

Originally Posted by smj

The cat we are on now has been struck by lightning twice, both times were before we purchased.
Carbon fiber mast with a 62’ height above water. According to the previous owner she was the tallest object above water for a mile.
The first strike blew out the depth sounder among other things, and no she didn’t sink. The second strike hit the lightning diffuser on top of the mast, so maybe time to get a refund from the snake oil salesman!

How'd you verify there was no damage to the carbon fiber mast?

[smj]

Originally Posted by Paul L

How'd you verify there was no damage to the carbon fiber mast?

Thermal imaging

[Paul L]

Originally Posted by smj

Thermal imaging

SMJ,
Interesting. Do you have any IR pictures you could post? Was the imaging done at ambient temperature?

[smj]

Originally Posted by Paul L

SMJ,
Interesting. Do you have any IR pictures you could post? Was the imaging done at ambient temperature?

No pictures to post, but from what I understand they used a heat gun.

[FlyingScot]

Cats are wider. In a marina or raft up scenario, wider boats are more exposed due to less 'cone of protection' from other tall objects. Therefore cats on moorings or anchor would be no less likely than any other boat.

[Tonali99]

Originally Posted by C420sailor

Florida has a lot of cats, and they get crushed by storms.

I’m not speaking in absolutes, my point is that the data isn’t corrected for location.

Well you do understand that Florida IS the lightening capital right? So what does one expect?
*
p.s. my 35' mono has been hit twice. Only lost the printer to (possible) EMP.

[abarrow]

I live in Banderas Bay, Mexico. In the 13 years I've been here, I've seen a LOT of boats that have been struck by lightning. My non-scientific conclusion about it is:

- Tallest boats get struck. One boat, just happened to be a cat, on the hard, got struck twice in the same season. Huge boat and definitely the tallest stick around. You want to be in a marina with a mast taller than yours near you, but not NEXT to you.
- Boats in marinas are more likely to get lightning damage, not only from direct strikes, but from boats near them getting struck, and from lightning travelling down power connections or just induction.
- Monos or Cats, whether you believe the stats in that table or not, the percentage of boats getting struck is extremely low, as is the probability that you will get struck. It's not zero, but neither is the probability you'll strike a floating container. Just ask Robert Redford ;-)
- It's just good seamanship to disconnect what you can (VHF, masthead transducers, etc.) if you intend to leave your boat during the lightning season.
- If you're going to get struck, your are going to get struck. I can tell you from my days working as a microwave engineer that lightning doesn't like sharp bends, it will find another route. So, if you are implementing a lighting grounding system, smooth bends please. I've never heard of the thing connecting a jumper cable to a shroud and throwing the other end overboard actually working, but it can't hurt.
- Even professionally working with microwave towers, I can tell you that lightning protection schemes are as diverse as the number of tower engineers out there. It wouldn't surprise me if some recommended the sacrifice of an animal before the storm to prevent a strike.
- Everything about sailing is a risk. Nobody wants a direct strike blowing a hole in the bottom of their boat, or to just lose $30K worth of electronics. Stuff happens. Enjoy your sailing and be as safe as you can be.

[CyKlop]

One of my thoughts is whether it is a statistical artifact. There are (I think) a lot more monohulls than catamarans and the cats tend to be in places where there are lightning storms.

As an (absurd) example, assume there are 100 monohulls and 5 catamarans.
95 of the monohulls are kept in Sweden, 4 of the catamarans are kept in Florida.


Which class of boat will show a higher percentage of lightning strikes?

[owly]

Originally Posted by FlyingScot

Cats are wider. In a marina or raft up scenario, wider boats are more exposed due to less 'cone of protection' from other tall objects. Therefore cats on moorings or anchor would be no less likely than any other boat.

"Cone of Protection" I got a good chuckle out of that! Is that a real term or one somebody just made up? I wonder if it applies to one of those mass shooters as well..... Are you safer in a crowd because there are more human bodies to draw bullets? It sounds like pure speculation to me... I've got to hand it to whoever dreamed that one up and coined the phrase. It'll go down in history alongside superecalifragilisticexpialidocious Sounds like something Spiro Agnew would come up with...

[FlyingScot]

Originally Posted by owly

"Cone of Protection" I got a good chuckle out of that! Is that a real term or one somebody just made up? I wonder if it applies to one of those mass shooters as well..... Are you safer in a crowd because there are more human bodies to draw bullets? It sounds like pure speculation to me... I've got to hand it to whoever dreamed that one up and coined the phrase. It'll go down in history alongside superecalifragilisticexpialidocious Sounds like something Spiro Agnew would come up with...

I understand that it dates back to Ben Franklin so you might be a little slow to have heard it.

[abarrow]

Cone of protection is a real thing.

You might be interested in this web site:
https://www.lbagroup.com/products/li...ble-masts-rods

Specifically: "PLP-32 Lightning Masts provide a cone of protection within which lightning charges are diverted to the mast and grounded instead of to the protected object. Multiple PLP-32 masts may be used to protect extended areas. Protected areas may be determined by use of the widely accepted “rolling sphere” concept. For example, a single PLP-32 mast will protect 9 foot (2.14 m) high portable buildings wholly within a 40 foot (12.19 m) radius. An array of five PLP-32 masts will protect a camp of portable buildings within a 25,000 square foot (2323 m2) area. Consult LBA Technology™ for specific layouts you wish to protect."

[Cheechako]

Lightening strikes do NOT seem rare to me. Which is a bit surprising ....but I have witnessed one and seen resulting damage in at least two others up close. One of which was mine. The one I witnessed was an old Trimaran in Mexico. I was rowing past after fishing and trying to get back to the boat in a thunderstorm. They can be bad damage or minimal.

My boat was fine at survey and 3 months later the windex was melted and there were black carbon streaks on the upper mast at the shroud hardware. No idea when it occurred and nothing else was damaged.

[Frankly]

"Cone of protection is a legit term in the LP codes and industry". 100 ft rolling sphere if IRC. I think 45 degrees for typical mast height. Having said that nothing with lightning is absolute. There is a standard evaluation list for determining "does this structure need protection". #1 Where, #2 relative elevation.


Frankly

[pbmaise]

I would be curious if trimarans were even higher. What may happen is lighting is attracted to something that occupies the greater surface area of water.

[noelex 77]

Lightning is a significant hazard for cruising yachts of all types. If you raise the topic with skippers who have been long distance cruising for a significant time a frightening percentage have been hit at some stage.

Our last boat was hit a few years ago.

Cats statically have a significantly increased risk.

The most important protection is to ensure any potential strike has a reasonably non destructive path to ground. This does not reduce the chance of the strike, but minimises the destruction, particularly the potentially severe damage.

There has been speculation why cats are more susceptible to lightening strikes. Some of the reasons are they are more likely to be moored on the end of marina on a T berth, but even accounting for these differences and factoring in the location they seem to be around twice a likely to be hit.

I did read a very detailed analysis by some physicists that specialised in this area that were convinced that a voltage potential generated between the hulls of catamarans accounted for the difference between monohulls and cats. They recommended grounding the hulls together. This is easy to do and worthwhile considering although you need to be aware of the potential stray current problems that could be caused. Sorry I have lost the reference.