Saturday, February 15, 2014

Cruising's Biggest Risk

Boot Key Harbor, Marathon, FL

You probably already know the technical definition of risk. It is the product of probability times consequence. It applies to both positive and negative things, but we usually don't use the word risk for positive things like winning the lottery. We thing of bad things.

So what bad things can happen to you? Obviously, the worst consequence is death. Fortunately, we have zero direct experience with fatal events while cruising, so the risk is low. On the other hand, we have run aground many times. The consequences of grounding can be severe or even fatal, but so far for us, the consequences have been minor. Grounding is low risk too.

What is the biggest risk? I think that it is being hit by lightning. It happens very often and the consequences are frequently major.

  • Around 1977, I read in the local paper about a sailboat struck by lightning while it was in Lock 9 of The Erie Canal. There were three men inside. It was struck three times in less than one second. The strikes made six holes in the boat, three in the cabin top and three in the bottom of the hull. It sank in seconds. The three men were unhurt.
  • Tarwathie was hit by lightning in Maine in 2006. We had six people on board when it happened, so I was relieved that no one was hurt. Nevertheless, it did $8000 damage to our electronics, but no structural damage.
  • Noble House was a fine vessel owned by friends Dennis and Barbera. We met them here in Boot Key Harbor. In 2009 Noble House was struck by lightning near Lake Worth Florida. Their hull was holed but the boat did not sink. They got towed into port. Then started a nightmare. I'm fuzzy on the exact details, but I heard that Dennis and Barbera spent 6 months of hell in a boat yard trying to get repairs. They had a big dispute with the insurance adjustor, and that caused the problem. In the end, they gave up on their cruising life. We haven't seen them since.
  • Our friends Bo and Joyce on Dreamcatcher, are in The Bahamas. Today I got the following message.

About midnight last night we got struck by lightening and have no electronics Bo talked to the insurance guy 2 times last night now we have to decide where we go for repairs so if you don't hear from us for a while we are traveling. Will let all of you know what happens and where we go might have to get back to the states. Have enough power to run the refrig. for 2 days then food is gone. Just talked to the boat behind us and they got hit harder than we did as it blew out a through hole.

Pray for safe travels and will talk later.

Joyce and Bo

  • I could cite several more examples, but you get the picture.
So, what can you do to prevent this from happening to you. Unfortunately, I can offer a half dozen suggestions, none of which work all the time. The sad truth is that lightning is hopelessly unpredictable in its consequences. Given the exact same boat with the exact same lightning precautions, and given 10 lightning hits in apt hat boat, the most likely result is 10 different outcomes. Any story you hear such as, "I did this and it worked," or "I did this and it didn't work," are useless anecdotes. The can't predict the future.

What precautions do we take on Tarwathie?

  • We have a static dissipation at the masthead, that supposedly reduced lightning risk. I used to have a deer whistle on the bumper of my car. I never hit a deer with that whistle on, but I never hit one with the whistle off either. The moral, there is no way to prove the effectiveness of a device like that.
  • We have a #6 wire that connects the mast to a Dynaplate grounding plate under the hull.
  • We have a plastic conduit surrounding that #6 wire to prevent molten copper from spraying around the inside of the cabin.
  • When lightning is near, we put all electronics possible in the oven of the stove. The oven acts as a Faraday cage to protect devices from EMP (electro magnetic pulse). Hand-held radios and our chart plotter are first priority to put in the oven.
  • Electronics in our ditch kit are stored in metal cookie tins.
Are any of these measures effective? Are we better off or worse off using them? My heart says "I hope so," but my brain says, "indeterminate." Few things in life are so darn unpredictable as lightning.

p.s. my old company, PTI, used to conduct lightning research by shooting rockets trailing wires up into thunderclouds. Whoosh went the rocket. KABLAM went the lightning 1/2 second later. The wire was attached to devices being tested for lightning resilience, An engineer doing the tests told me, "I can't believe that you are paying me money to do this. I am having the time of my life. I would gladly do,it for free."

Below is a picture of triggered lightning. 9 strokes happened before the camera shutter could close. The straight line on the left is the vaporized remnant of the wire. Wind was blowing from left to right.


p.p.s. I hate auto spelling correction. The sentence above saying "the three men were unhurt," was changed by my computer to read "the three men were neutrinos."


1 comment:

  1. Dick: is the static device on the mast higher then the vhf antenna? I was thinking of adding one but with the antenna seems pointless... and we don't have much lightening or rain here in CA....


Type your comments here.