How do you prepare for a lightning strike on a sailboat?

After our recent 500 mile crossing where we encountered our worst storms at sea in 13 years, we talk about tactics for avoiding and sailing through lightning storms.

Lightning can strike from up to 15 miles away with a force of 30,000,000 volts, so what do you do when you’re on your boat and an electrical storm approaches?

Your chances of being struck DOUBLE if you’re on a catamaran!

Are there any stats?

The only stats we found are from Boat US Magazine which ran an article in 2015 based on 10 years of marine insurance claims. While we know this is incomplete and only includes vessels which have made insurance claims, the gist is useful. In general, the odds of being hit are 1,000 to one.

In some areas it’s far higher, Florida is 3.3 in 1,000

From personal experience of sailing in the area, we can back up the stats that Singapore is the other place in the world with the most lightning strikes. We would suggest that the Malacca Strait falls into that category too!

And according to Boat US’s information your chances of being struck double if you’re in a catamaran. Read the full article here

What kind of damage can you expect?

Lightning doesn’t have to hit the boat directly to cause damage, it’s electro magnetic field can create a horseshoe effect which will catch you in its net.

Aside from danger to yourself, a strike can take out plotter, radar, compass etc. Or even worse, it’ll blow a hole in your hull

The extent of damage isn’t always obvious as some electronics can take days or weeks to eventually burn out. And when lightning exits a boat via a through-hull fitting you’re in trouble. If it doesn’t blow a hole in the hull, it could create a gradual leak that goes unnoticed.

Watch the video for more details:

We got in touch with Katy Stickland of YBW who have run number of features and case studies. Gill and Mick Russell’s experience off south coast England illustrates exactly how bad it can be…

When lightning hit them, molten metal melted into the deck, electricity engulfed the whole boat and went through Gill, striking her unconscious. It exited through the rear nav light, blowing it to pieces as it went. Gill came round but was weak and unable to help Mick who had to deal with the additional problem of a prop wrapped tightly by weed: after the devastation of a lightning strike he had to jump over the side to free it up.

Cost of repairs in cases like these easily run into five figures.

Tactics

You cannot prevent a lightning strike – nothing exists in the world of science to stop strikes. But there are a few tactics to have up your sleeve.

1. Monitor the weather via vhf and internet.

  • We use Iridium Go + Predictwind on passage. If you’re within internet range, use live radar and lightning apps.
    (Before you set sail ensure all hand-held devices are fully charged and don’t let them run down.)
  • Look for anvils forming in the clouds and avoid them!

  • It’s hard to predict the direction of storms because huge thunderclouds are moved by upper atmospheric wind, not the sea breeze you’ll be using to sail. We have watched them bowling towards us while we’re sailing downwind!
  • Radar is useful in tracking storms

“When thunder roars, go indoors!”

2. If you’re able to, get off the boat.

3. If you can see lightning but can hear no thunder you still have time to change direction. Thunder begins to be heard from 25 miles away.

  • Count and divide by five to work out how far it is from you.
  • But remember that wind and visibility can change in seconds.

4. Be prepared.

  • Take a fix and plot it on a paper chart in case you lose all your electronics
  • Update the log book using dead reckoning.

5. Find a protected area on the boat.

  • If the mast is properly grounded it will have a “cone of protection”, so in theory you can stand within that cone.
  • Stay away from metal objects and power outlets – even instruments in the cockpit can blow out and catch you.
  • Remember that side flashes can jump from metal objects to people.

6. Lower antennas, fishing rods, outriggers etc.

7. Disconnect all electrical appliances.

8. Put portable electronic objects in a Faraday Cage – ovens are good for this. But don’t forget to take them out next time you cook a roast dinner!

9. Don’t use the VHF unless it’s an emergency.

10. Wear gloves if hand steering.

11. Remove jewellery, watches and anything else metallic from your body.

12. When it appears to be all over, wait 30 mins after the last thunder clap.

13. Get the engine running as soon as you think you may be within striking range of lightning because you may not be able to start it again.

What to do if struck

If someone is hit, check they are moving/breathing. If they are, they’ll probably be OK. If there’s no pulse, administer CPR. There is no danger of touching someone who has been shocked by lightning.

Check the bilges for water. Lightning can blow out transducers and through-hull fittings – or even just a hole in the boat. Plug the hole and get the pumps running. A powerful submersible pump is a good tool to have on standby for these situations.

If you need assistance, call on VHF. If it’s not working, use flares.

Keep checking for leaks afterwards or until you are back to safety. Minor damage to through-hulls can get result in slow leaks.

Always get a full survey afterwards. A professional is more likely to pick up on the after effects of a strike that you may have missed. And a survey will, of course, be required for an insurance claim anyway.

Lightning Protection Systems

You cannot prevent a strike, so these systems are designed to take the strike down a path to a ground. In all case studies, the equipment on every masthead was destroyed.

According to American Boat & Yacht Council standards, in a properly bonded system the strike should follow a low-resistance path to a boat’s keel or an installed grounding plate.

An air terminal mounted atop the mast (at least 6” above everything else) runs a thick cable to the ground plate under the water. Grounding plates (long and thin with grooves) should be mounted at or near the surface of the water.

Multiple terminals and multiple ground plates work better.

You can ground to a lead keel if it isn’t encapsulated.

You can also ground to metal rudders or propeller struts.

However, lightning might not follow sharp angles anywhere along the cable, it looks for the quickest route. Install a grounding plate directly underneath the mast, if possible.

Lightning dissipators

The theory is that the many strands dissipate a strike, but there is no evidence that this works!

ESE (early streamer emission) devices are torpedo-shaped rods with circuitry that attract lightning more than normal rods to ensure lightning strikes the grounding path. Again, there is no proof this will work.

SPDs (surge protection devices, or TVSSs – transient voltage surge suppressors) may be used to protect critical electronics. They are installed across the voltage terminals of each device to prevent voltage spikes.

Conclusion

Armed with all this knowledge, and knowing how to best fit out your boat, will you ever be ready to sail into a lightning storm?

As sailors who have done this frequently (which you’ll know from our vlog) we still don’t feel we will ever be fully prepared. Sometimes you just have to take your chances.

If you’ve been struck by lightning, we’d love to hear from you. And if you haven’t, what do you do when a storm approaches? Let us know in the comments below.

As always, thanks for supporting us and allowing us to share our adventure with you.

Peace and fair winds!

Liz, Jamie and Millie xxx

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