Being Hit By Lightning - To Ground or Not

[marinedtcomRob]

There's a very good article on "Lightning Protection" by Nigel Calder that was published in the December / January 2004 issue of Professional BoatBuilder magazine. If you want an in depth and up to date (relatively speaking) review on this subject, Calder is, as usual, painstakingly thorough. The article was not available online that I could find but the phone number for the magazine is 207-359-4651. Presumably they sell reprints.

[sailingdog]

Stillraining-

You don't want the lightning bonding ribbon to make any sharp bends... and having the grounding plate is as direct a line with the mast is probably the best idea. Having the grounding foil or wire turn will likely lead to lightning sideflashes, and given where your fuel tanks are, that's probably not a good thing. Lightning + Fuel = BOOM!!!!

And as Wayne has pointed out the 4' linear edge figure was for a boat in salt water. If the boat is in fresh or brackish water, it will need more plate edge exposed.

One of the best grounding strips I've seen in a long, long time was a 1/4" thick plate with 15 3/8" x 2" threaded copper studs attached to it, that was 2" wide by six feet long, and embedded in the hull of a boat. The boat was a cold-molded wood and fiberglass/epoxy composite trimaran.

[ppsavage]

We have a 62 ft sailboat with a tall rig. The top of the pigstick is 98 ft above the waterline. When we built the boat in England, we installed two "No Strike" ion dissipating rods. They are "bottle brush" devices that are connected to the Fredrickson sail track. The sail track is connected to the mast step which is connected to a keel bolt with copper tape. The chain plates are also connected to the keel bolt with copper tape.

We have sailed the East coast, from New England to the Chesapeake and in FL and Tampa Bay and have been in and around many thunderstorms and have never been hit. We've had instances of boats very close to us at a pier or at a mooring, with much shorter masts, which have been hit.

Ion dissipators are intended to dissipate or "bleed off" the electrical charge which builds up during a thunder storm before the accumulated charge creates a "leader" to the cloud which channels the high energy strike.

A quick web search found two sites of interest: LEC GLOBAL has lots of engineering information about lightning strike prevention. Their ion charge dissipators are a bit unwieldy for most boats! :-)

Northsea Navigator's products are almost identical to what we have installed. It was interesting to see their guarantee! I like doing business with a company that puts their money where their mouth is. Their business is PREVENTION of strikes, not minimizing the damage that occurs when struck. It would be interesting to see what their claim history is.

*******************************
Designed for sailboats 25-45ft
Height 14"
Width 3"
Weight 1.5 lbs
$ 285.84
Lightning Prevention Systems warrants your product or products to be free of defects in workmanship and materials for a period of 7 years from date of purchase. Lightning Prevention Systems also guarantees that, when properly installed, your boat will not experience a direct hit by lightning. This guarantee will be in effect for a period of 5 years from the date of purchase. Should your boat ever be struck, Lightning Prevention Systems will pay up to one thousand dollars of your insurance deductible for the claim submitted for losses or damage caused by that direct strike to your boat. Lightning Prevention Systems will pay five hundred dollars for losses or damage caused by a direct strike of your boat is uninsured. This guarantee is non-transferable and covers units remaining in their original installation location and boat.
**********************************

Our experience says perhaps you CAN prevent strikes.
You need:
- an effective dissipator (or several dissipators) at the masthead,
- a very straight high conductivity path to the water

This installation has worked very well for us. We've been spared hits while very near to us, boats with much shorter rigs were hit, usually on the VHF antenna.

I would have posted the links and photo but I just found out until I've posted 10 posts, I'm prohibited from including links or photos.

[cspots]

The definitive answer isn’t in for lightning protection on a sailboat. It isn’t even clear how all the damage is done by lightning, nor what type of lightning we are trying to protect from. Any time there are many ways to do something, it means that either anything, or nothing works well enough.

The basic concept of a simple lightning rod, with a direct connection to ground, has worked very well for centuries. (Possibly until we started to have phone and electrical wires going into buildings?) Since the early 1800's the British Navy very successfully prevented damage from lightning strikes on wooden sailing ships, with wooden masts by using an iron rod and iron wire from the mast tops to the water. Nobody has proven any benefit over these simple systems, in spite of all the hype of the lightning rod salespeople.

>
>
Per a report on lightning by BoatUS Seaworthy: “(1) It is better to avoid being struck in the first place, but (2) if your boat does get hit, you will suffer less damage if the strike is grounded as directly as possible.” >>
> >
What I plan to do isn’t far fetched, and is relatively simple, and cheap. It may not protect from every type of damage, from every type of lightning, and it may work better with a catamaran.



> >I want to keep the lightning out of the boat! Give it a simple, direct route to ground, without connections, angles or upward angles, which encourage side deflections. Don't encourage it to hit the mast, and then try to minimize the damage.



Use 4-10 G insulated copper wire, stranded. The size may depend on mast height, and your anxiety level. Run it through and attach it to ½ inch PVC pipe, and hoist it by a halyard (spinnaker, main, spare jib, or topping lift) attached to the PVC. This is to add rigidity (and further insulation where the wire is closest to the mast near the top). The wire is secured inside the pipe with a wad of electrical tape.
The top 2 feet or so of wire should be above the highest antenna, and the top foot of insulation would be removed and these wire strands, above the antennae, could be:

• splayed open,
• pointed, or
• rounded (preferred)

In an almost straight run, the wire would stretch from above the mast head, through the bow netting to the water. This is not close to any electronic equipment, or metal. The insulation is removed just above the water, and the wire strands are splayed and run into the water for at least one to three feet, to allow better grounding and dissipation of current. This would be more difficult to set up when sailing, but not impossible. On a monohull, the wire could go over the lifeline, through another piece of PVC pipe.
> >
Granted, even 2 G wire wouldn’t protect completely from a direct lightning strike, but the goal is to get the lightning out of the boat, not just to give it more benign route through it. Then hopefully the cone (or rolling sphere) of protection will protect the occupants and equipment.

[pmichaelis]

There are numerous folk medicine cures, but none that are 100% effective. My boat had a well grounded system and was struck by lightening anyway. The strike evaporated my masthead antenna right down to the loading coil, then proceeded down the standing rigging and out the hull mounted grounding plate. The total damage was; the antenna, the masthead tricolor strobe unit and the voltage regulator on the engine generator. Afterwards I added a copper plate attached to a substantial braided conductor which had a very large battery clamp attached. This was clamped to the backstay whenever the boat was on it's mooring or when I was aboard and saw an oncoming storm. As a physicist, my recommendation is to avoid changes in the path of your grounding system. Any deviations represent an increase in inductance and since the voltage developed is L(inductance)x(Di/dt), with Di being very large and the time period dt very short for a stroke of lightening, the backvoltage developed can be enormous and divert the energy to another path.

[sailingdog]

I'd be a lot more impressed if they would pay for repairs, rather than just your insurance deductible...which is a cheesy way out, and of absolutely no use to people without comprehensive insurance on their boat. And even worse, they'll pay $1000 if you're insured but only $500 if you're not insured... really nice...

Of course, the number of boats that are hit is so small that statistically, it is in their favor to pay $1000, since I seriously doubt more than one boat in five that they sell to actually gets hit by lightning.... As long as less than one boat in ten or twenty gets hit... they're going to make a killing... since they're charging almost $300 for the bottle brush.

Originally Posted by ppsavage

.... A quick web search found two sites of interest: LEC GLOBAL has lots of engineering information about lightning strike prevention. Their ion charge dissipators are a bit unwieldy for most boats! :-)

Northsea Navigator's products are almost identical to what we have installed. It was interesting to see their guarantee! I like doing business with a company that puts their money where their mouth is. Their business is PREVENTION of strikes, not minimizing the damage that occurs when struck. It would be interesting to see what their claim history is.

*******************************
Designed for sailboats 25-45ft
Height 14"
Width 3"
Weight 1.5 lbs
$ 285.84
Lightning Prevention Systems warrants your product or products to be free of defects in workmanship and materials for a period of 7 years from date of purchase. Lightning Prevention Systems also guarantees that, when properly installed, your boat will not experience a direct hit by lightning. This guarantee will be in effect for a period of 5 years from the date of purchase. Should your boat ever be struck, Lightning Prevention Systems will pay up to one thousand dollars of your insurance deductible for the claim submitted for losses or damage caused by that direct strike to your boat. Lightning Prevention Systems will pay five hundred dollars for losses or damage caused by a direct strike of your boat is uninsured. This guarantee is non-transferable and covers units remaining in their original installation location and boat.

[soverel48]

After 2 years of researching this and looking at hundreds of boats this is what I've been able to discern..and this is what I did on my boat.

Forget about where the too small, existing plate is. That plate is likely for grounding the DC system and far too small for this job. Buy a copper plate a minimum of 1/8" thick and 1 square foot in area (thicker and larger are probably better and yes more edge length is better.) You must through bolt the plate to the outside of the hull as close to the mast step as practicle. Access from inside the hull will probably limit where you can place the bolts and will therefore help determine the shape of the plate you need. Use #4AWG (or larger) copper strand wire to connect the mast to the plate. Avoid bends in the wire. Use bronze bolts 3/8" or larger in diameter to secure the plate to the hull and to the cable. You can buy the Bronze bolts, washers and nuts from Lewis marine and other places. You can get the copper plate from several places on the internet such as "onlinemetals.com" It is not that expensive.
I used .125" thick but would use .25" thick if I did it again. If you would like more details, I'd be glad to help.

[artbyjody]

Originally Posted by soverel48

After 2 years of researching this and looking at hundreds of boats this is what I've been able to discern..and this is what I did on my boat.

Forget about where the too small, existing plate is. That plate is likely for grounding the DC system and far too small for this job. Buy a copper plate a minimum of 1/8" thick and 1 square foot in area (thicker and larger are probably better and yes more edge length is better.) You must through bolt the plate to the outside of the hull as close to the mast step as practicle. Access from inside the hull will probably limit where you can place the bolts and will therefore help determine the shape of the plate you need. Use #4AWG (or larger) copper strand wire to connect the mast to the plate. Avoid bends in the wire. Use bronze bolts 3/8" or larger in diameter to secure the plate to the hull and to the cable. You can buy the Bronze bolts, washers and nuts from Lewis marine and other places. You can get the copper plate from several places on the internet such as "onlinemetals.com" It is not that expensive.
I used .125" thick but would use .25" thick if I did it again. If you would like more details, I'd be glad to help.

Is it tested by actually being hit by lightening?

[Hartley18]

A note on protecting ship-board electronics for the lightning-prone:

Surge damage can be minimised by installing a surge diverter and virtually eliminated by installing a (more expensive) surge filter.

As the name indicates, a surge diverter is fitted to the +ve and -ve terminals of the equipment you want to protect and basically diverts any power surge to ground (your grounding plate). Good quality ones contain a gas-discharge tube, which provide a high-voltage path to ground and at least one metal-oxide varistor (MOV) between the terminals and earth to limit the maximum voltage on the wire.

A more expensive option is a surge filter, which is fitted in series with the power connection to the electronics and, as well as the above devices, contains a set of inductors and capacitors to prevent any trash on the wires making it to the set. You can buy surge filters for masthead antennas for far less than replacing the radio if you get hit.

As a bare minimum, I'd suggest installing a surge diverter on the radio batteries - for only a few bucks spent at Radio Shack, you might still be able to call the coastguard after the event... of course, both these gadgets must be properly grounded otherwise they won't work...

[BIRDBATH]

This Has Not Been Tested, But If At Anchor In An Electric Storm, I Bend The Storm Anchor Chain Around The Base Of The Mast And Dangle The Anchor Over The Side. It Seems To Me This Would Divert The Strike To The Water And From The Existing Bonding System. The Existing Bonding Wires Are Not Too Heavy (they Are Imbedded In The Fiberglass) And The Grounding Element Consists Of The Shaft And Prop. The Anchor Makes Good Contact With The Water.

In Retrospect, I Should Also Do This At My Slip.