• On September 1st, Maine Sail suffered a major hemorrhagic stroke. One of the most generous members of our sailing community, he has helped thousands. Now it's our turn. Click here to learn more

Lighting protection when on the hard question?

Jan 24, 2017
Hunter 34 Toms River Nj
So long story short, my boat has been struck by lightning three times over the past 30 plus years. Twice in the water and once on the hard. In the water strikes produced very litle damage so the grounding protection aparently worked well.

The Lightning strike on the hard did lots of damage to almost all of the 12 volt systems, batteries, wiring, electronics, all fried.

Now as I understand the way a sailboat Lightning strik works is basicly the Lightning travels thru the mast and rigging to the keel and disperses into the water. At least that's the theory.
Now on the hard the electricity can not disperse into the water obviously.
In my case the Lightning did not have a direct path to ground and bounced all over the systems.

So I have spoken to lots of engineers and electricians about my concerns on the hard.

So my idea was to drive a grounding rod into the ground and attach a heavy duty steel cable to the rod and connect the cable to a steel c clamp, which I will clamp to my steel keel.
My thought is that this should effectively and safely Chanel any electricity directly to the earth as if the boat was in the water.

I have got mixed views on this idea. Some think it should work well and others believe that this will attract a strike.

Now my mast is unfortunately the tallest in the yard standing 60 feet off the ground.

What are your thoughts about grounding it or not?
Feb 14, 2014
Hunter 430 Waveland, MS
Grounding your boat is a good idea.
Use a many grounding rods as you can to simulate the effect of the normal water ground you have when in the water.

Grounding your standing rigging also helps.
Grounding makes your boat look "electrically" like the flat ground, around your boat.

Just like water towers and bridges do grounding to reduce the potential of a direct strike.;)
Jun 14, 2010
TBD Looking for my next boat CT
My boat was struck twice in 18 years. Yours 3 times in 30. Maybe we should just plan for once per decade? :(

I think your ideas are sound, but there’s no way to predict what lightning will damage.
Mar 26, 2011
Corsair F-24 MK I Deale, MD
How common is lightening between October and April? Unless we are talking about summer storage, there is minimal risk.
  • Like
Likes: RoyS


Jun 3, 2012
Hunter 33 Steamboat Wharf, Hull, MA
On the strike that occurred on land, did you have an extension cord plugged in to your boat?
Jan 19, 2010
Hunter 26 Charleston
This place sells lightning protection equipment but it also has a nice "how to" video and some instructional materials.

Feb 14, 2014
Hunter 430 Waveland, MS
The concept of protection is simple.

Don't let your boat be a likely target.:biggrin:

If properly grounded, the height of your mast means nothing.

Just like a community Water Tower!

Where is the epidemic of Water Towers being blown away by Lightning strikes?
If you get a chance, go look at a Water Tower.

There is a "BIG LIGHTNING ROD" sticking high above the Water Tank.:yikes:

Then you will notice a Big cable tied to it, which runs to a Big ground rod.


It is NOT to conduct a strike to ground!


to allow electrons, at the Ground Potential, to be at the top of the tower.

Thus the Charged Cloud doesn't not "see" the tower as a likely strike point.
This does NOT stop a strike, but reduces the chances significantly.

PS: I have been trained by the best in lightning protection.:pimp:


Jun 1, 2007
Macgregor 26S Hobie TI Ridgway Colorado
So my idea was to drive a grounding rod into the ground and attach a heavy duty steel cable to the rod and connect the cable to a steel c clamp, which I will clamp to my steel keel.
I have got mixed views on this idea. Some think it should work well and others believe that this will attract a strike.
Consider that you got mixed views.. because actual grounding or not might not matter that much in you getting a strike or not. I dont think anyone can show any actual evidence that it matters with your chance of getting struck. Creating a known path for lightning energy to flow is no doubt a good idea. Grounding or not.. no proof that it reduces your chance of a strike, but also no proof that it increases your chance a strike. If anyone wants a discussion involving electric fields (what is really important in this subject), corona currents and how this affects leader generation.. please ask. But it would all be just theory. The advice to ground the crap out of everything is overall safe advice. Its not about trying to avoid a strike but its about creating a known best path for dissipating the energy if you do get struck.

Steel cable.. Im not sure. All the studies I have ever seen on lightning grounding use copper and it involves both conductivity and melting point of the metal. I believe home codes still say 8 gauge copper for lightning grounding (anyone know for sure) but I can find a reference saying that is marginal. 4 gauge copper would be better.

FYI, the only study I have ever seen regarding changing your chances of getting struck involved sharp pointed vs blunt pointed lightning rods. A lightning rod is supposed to attract a strike so that it protects things around it from getting struck. So these studies were looking to figure out what worked BEST for attracting lighting and they found that "blunt" lighting rods got struck more often than "sharp" lighting rods. The technical paper at the bottom gives a theory of why.

How you would use this info on a sailboat.. cant really say but if I had a big lighting rod (ie, a mast) and wanted it to still work as a lightning rod when on the boat (because its way better for the mast to take the strike rather than the top of your head), I might consider putting a sharp pointed lighting rod at the top.

The simpler version of that paper comparing blunt vs sharp lightning rods is here LIGHTNING RODS: FRANKLIN HAD IT WRONG

The actual technical paper is here
Last edited:
  • Like
Likes: Will Gilmore
Jan 24, 2017
Hunter 34 Toms River Nj
Answeres to some questions.
1 No power cords plugged in
2 electrical storms very common in Nj. During October thru April
3 un stepping the mast not really an option due to $$$ to rent a Crain my marina doesn't have the equipment to do it.

Thanks for the suggestions and feedback
I feel that grounding on the hard is the best way to go
Feb 14, 2014
Hunter 430 Waveland, MS
I feel that grounding on the hard is the best way to go
If you would like to discuss the best grounding practices, I can do it by phone or Private Message.

PS: Grounding your boat in the water is covered by the ABYC standards.;)
PSS: Grounding land objects are also covered.;)
Oct 19, 2017
O'Day 19 Littleton, NH
I would like to give my thoughts on this subject. I am not an electrician, nor an electrical engineer, but I have some education in general electrical theory from college physics and computer systems classes. Take these thoughts in the spirit of a modestly educated layman with no practical experience who is as interested in reading any corrections and critiques of my ideas as I am in sharing what I know.

What I know about electricity:
¤ Electricity is the result of the movement of electrons due to the forces of attraction between electrons (negative charge) and protons (positive charge).
¤ The potential charge is based on the pressure gradient between electrons and protons.
¤ The EM forces of attraction and repulsion are carried through a field that can be effective over great distances. The path of least resistance is determined through this field before elections move. You can't fool them into a false path to ground, you can only offer them either a better path or a better ground.
¤ Protons generally make up atoms of elements and compounds around us and are joined with enough orbiting electrons to render them neutrally charged, starved for electrons causing them to be positively charged, or have an over-abundance of electrons making them negatively charge allowing them to give up their extra electrons easily. Elections, on the other hand, don't make up elements or compound by themselves and may be free of or bound with one or more protons.
¤ Protons are much more massive than electrons. This means that, in a tug of war between electrons and protons, electrons lose. Elections are, most often, moved by the attractive forces while protons, both more massive and locked in a matrix of matter with other protons, don't generally move much towards the attracting electron.
¤ Elections repel each other. This is an important concept when considering how to protect something from an electrical charge.
¤ Ground means the negative side of the pressure potential and is any condition that encourages the dispersal of the charge force. It doesn't have to be actual ground. The actual ground just happens to be the most prevalent commodity for this condition.

Now for some thoughts on what all this means for protecting equipment aboard a sailboat on the hard.
A grounded lightning rod, as James points out, brings the surface electrons, that follow under a lightning storm, up to the top of the rod. This, does not mean that all the electrons are up their. Elections repel each other, so they are difficult to pack into small spaces and their repelling force works to disperse them rather than concentrate them. They will likely fill any availible conduit evenly, like a gas fills an empty chamber. The most logical result of a grounded mast or lightning rod is to slightly reduce the distance and therefore the resistance to the potential reservoir of electron depleted protons blowing around in the clouds up above.
Another result of the repelling force of electrons is the Skin Effect. This is what makes a faraday cage work. Anything inside the cage is protected by the Skin Effect. Elections coat the outside of a conductive cage and don't affect what's inside the cage because they are busy repelling each other. The outside of the cage represents the farthest distance they can get away from each other. The only way something inside the cage can be in danger is if there is a greater potential variance between the negative charge of electrons on the outside and some object on the inside. A large positively charged object inside the cage might be able to overcome the repelling force and all the electrons would rush to the nearest point and arc across from cage to object through whatever presented as the path of least resistance.
The path of least resistance is relative. There may be more charge potential than a single path can handle. Elections can and do take multiple paths to equalize their charge variance. They do so by ratio determined by the various resistance values of their possible paths. A single path can handle only so much charge. There may come a point when a secondary path or paths is taken with significant amounts of the overflowing charge.

Specific ideas about grounding your sailboat on the hard:
Your sailboat is already ground wired when in the water. Your thoughts about grounding your keel are logical and appropriate, I think.
Options to consider:
You are storing your boat for the Winter, so you don't need the electronics to be working or connected to anything. Ground the mast and keel, but also any conductive stays that can help keep electrons on the outside of your boat. Connect them together through the ground so the electrons are free to move to the outside of the whole structure. You could even hoist a few cables aloft to facilitate this.
There is likely a large chain link fence nearby. The fence posts may not be 8' into the ground but the post diameters are large and there are a lot of them. The fencing would be a great conductor with a surface area on a par with 4 gage cables. Lightning has about a million volts of potential so go big. It's the surface area of your conductor that matters, not the cross sectional area (remember the Skin Effect).
I therefore suggest that, not only do you ground your mast and stays, but disconnect your electronics from the ground and any connection to the mast or outside conductor. Then, they are just boxes of metal and plastic like anything else inside your boat.

I look forward to whatever anyone else has to say on my musings and the chance for me to learn more.

-Will (Dragonfly)