BoatUS published an article in 2015 identifying the probability of lightning strikes as a function of type of boat and size of boat.
Table 1. The probability of a lightning strike by type of boat, 2003–2013
Type of Boat Chances per 1,000
Multihull Sailboat 6.9
Monohull Sailboat 3.8
All – Overall Average 0.9
Bass Boat, Runabout, Pontoon Boat 0.1
Table 2. The probability of a lightning strike by size of boat, 2003–2013
Type of Boat Chances per 1,000
0-15 Feet 0
16–25 Feet 0.2
26–39 Feet 2.1
40–64 Feet 6
The same article also identifies what to do if you are caught out on the water when there is lightning:
What To Do If You're Caught Out On The Water
"When thunder roars, go indoors." If there is time, return to shore and take shelter in an enclosed building (not open-sided) or your car. They are not impervious to lightning, but the lightning is less likely to do damage.
But if lightning has already begun, getting closer to shore may bring you close to trees and other objects that could be lightning targets. In that case, stay on the boat and do the following:
- Go indoors — go down below. Stay in the center of the cabin if the boat is so designed. If no enclosure (cabin) is available, stay low in the boat. Don't turn yourself into a lightning rod!
- Keep arms and legs in the boat. Do not dangle them in the water.
- Discontinue fishing, water skiing, scuba diving, swimming, or other water activity when there is lightning or even when weather conditions look threatening. The first lightning strike can be a mile or more in front of an approaching thunderstorm cloud
- Disconnect and do not use or touch major electronic equipment, including the radio, throughout the duration of the storm.
- Lower, remove, or tie down the radio antenna and other protruding devices if they are not part of the lightning protection system.
- To the degree possible, avoid making contact with any portion of the boat connected to the lightning protection system
From University of Florida's "Boating-Lightning Protection" by William Becker
- On larger boats with an oven or microwave, putting electronics inside should prevent them from being damaged as the oven or microwave will act as a Farraday cage, allowing the charge to pass harmlessly through the metal around the devices."
Another article worth reading is Lightning-Proof Your Boat. Note especially the damage done to the electronics through “electromagnetic induction” and “side flashing”… scary stuff.
An article in BoatUS provides more information. The author is James Coté “…an electrical engineer, ABYC Master Technician, Fire Investigator and Marine Investigator. He operates a marine electric and corrosion control consulting firm located in Florida. For more information, go to: www.cotemarine.net”
Following are excerpts from DWFORUM in April 2017 in which contributors shared their personal experience in dealing with lightning:
"I have relied on the stainless stays on the sides with a 2’ square of copper sheeting mounted below the water line and a flattened 1/2” pipe to carry the stay anchor point over the edge to the plate. I’m not sure how effective it is at the top relative to the radio mast, but the connection to the water should be fine. I’ve never known it to be tested, however!"
Tom Schultz Apr 3, 2017
"My Paradox does have lightning protection as per plan. It consists of a copper strap which leads from the top of the mast directly through the boat to the water."Andre-Francois Apr 3, 2017
"The static wicks on an airplane are only meant to dissipate the static charges that build up from the friction of air rushing over the skin.They do nothing against lightning. The skin of the aircraft is your protection, as electricity only travels on the outside of a metal object. Composite aircraft get a layer of metal mesh like window screen to provide this protection. In a boat, just like on land, a metal cage or can is your safest place in a lightning storm.So carry a metal garbage can you fit into on the boat, or build a cage of wires into the cabin for crew safety. A cable from the mast to the water will keep the hull from damage."Josh (Rowerwet) Apr 5, 2017
"...that's what we did on Dad's Wharram. He had a permanent rod off the backstay coming off above an insulator and running down under water and a pair of thick jumpers we'd deploy off the shrouds if we were out in dicey conditions."
Michael Burwell 4/11/17