Lightning strike - not theory!

[MAC26X]

Remember all the theoretical discussions about lightning strikes. Now I have first hand experience on the Mac26X. We were not on the boat and it was in our marina slip. There are only 2 sailboats in our marina, similar mast height. Our area had thunderstorms last week with a lot of lightning. I was gone but 2 or our neighbors woke up and saw sparks shooting off the top of our mast for quite a few seconds, followed by a boom that shook the windows in the condo and caused a power outage. But the neighbors didn't mention it until they saw me on the boat with a puzzled look. Here's what I've found so far, but I'll pull the boat for a more complete inspection:

- 3 ft radio antenna at the mast head is gone
- cabin light lenses blown off and broken
- cabin light bulbs exploded
- a couple areas of gelcoat blown off the inner liner near the cabin light
- power panel rocker switches blown across the cabin
- part of power panel fuse holder area melted- all fuses blown
- in line fuse holder by battery exploded
- sink drain hose blown off of both ends.
- hole broken out of storage bin (next to thru hull for sink hose)
- thru hull pvc for sink drain blown off of the inner hull - 4 inch chunk of fiberglass came off with the connection. This area of the fiberglass is charred, indicating this may have been the exit path for the strike.
- various areas of the wiring with the insulation melted and wiring broken.

Good news:

The motor circuit is fine and the motor started right up.
Now I'll rewire the boat using something better than the white lamp cord.

We will see just how good our insurance is.

[Catigale]

Boy - that would have been cool to be on board when that hit...

[craiglaforce]

Wow, can you tell where the lightning went to the water? sounds like through the sink drains. But I would inspect the centerboard cable also.
Did you get the thousand exit pinhole thing around the water ballast tanks, like the other mac that was hit?

Steel centerboard cable or rope?

THanks.

[Billy]

Just curious here. Does your sink drain hose still have the factory loop that holds water? Acts like a P-trap. (Exploring the super heated water theory. )

[kmclemore]

Just curious here. Does your sink drain hose still have the factory loop that holds water? Acts like a P-trap. (Exploring the super heated water theory. )

Yeah, I was thinking the same thing... it blew up when the water converted to superheated steam.

[Moe]

- 3 ft radio antenna at the mast head is gone

pretty typical from what I read...
Did you have an anchor light or windex up there and if so, how did they fare?
Was the radio on-board and damaged?

- cabin light lenses blown off and broken
- cabin light bulbs exploded
- a couple areas of gelcoat blown off the inner liner near the cabin light

above and forward of the upper black trim around the compression post I found a bird's nest of wiring, some going to the forward starboard cabin light, some to the deck plug for the steaming light.
Was your mast plugged into the deck? I'm guessing it probably wouldn't have mattered due to said bird's nest, but still curious.

- power panel rocker switches blown across the cabin
- part of power panel fuse holder area melted- all fuses blown
- in line fuse holder by battery exploded

although what follows sounds like it then side-flashed from the battery to the sink drain, I'd still pull and examine the batteries, give the terminals on the motor cables a good tug and twist to make sure they're still firmly clamped on, pop the motor cowling and inspect where they attach, and inspect both the motor mount and lower unit, including the zincs.

- sink drain hose blown off of both ends.
- hole broken out of storage bin (next to thru hull for sink hose)
- thru hull pvc for sink drain blown off of the inner hull - 4 inch chunk of fiberglass came off with the connection. This area of the fiberglass is charred, indicating this may have been the exit path for the strike.
- various areas of the wiring with the insulation melted and wiring broken.

I'd also pull the forward starboard dinette seat cushion and inspect around the base of the compression post and the centerboard hanger. Not much of a gap between them, but lightning may not have taken this path, in part due to the poor conductivity of the stainless steel. Also inspect around the chainplates, the stem, and the backstay attachment point. When you pull the boat, definitely inspect the centerboard hanger.

Thanks for sharing this and please keep us updated with the results of further inspections.

[LOUIS B HOLUB]

An Aweful Event ! Fortunate that the engine is okay !

Makes me wonder about the theory of a battery cable, clamped onto the mast base with the other end in the water. Sounds like the electricity needs a "strong" path way into the water, maybe possibly a heavier cable than a battery cable -- something tough to carry a heavy load of current.

[Sloop John B]

Was there a tank of water connected to your sink?

I think everyone assumes your mast was up, boom attached. Steaming light plugged into socket.

Anything different about the shrouds and stays?

Opinions about path? (I have nightmares about side strike from compression post).

Any damage to other boats? (I lost two trees, hundred feet apart, with one strike, pitch forked like flash).

[MAC26X]

I'll try to answer all the questions in 1 post.

Boy - that would have been cool to be on board when that hit...

Might not have been cool- maybe toasty or shocking.

Wow, can you tell where the lightning went to the water? sounds like through the sink drains. But I would inspect the centerboard cable also.
Did you get the thousand exit pinhole thing around the water ballast tanks, like the other mac that was hit?

Steel centerboard cable or rope?

Right now it looks like the sink drain was the exit but I will pull the boat this weekend to inspect the hull.

Rope Centerboard line.

Just curious here. Does your sink drain hose still have the factory loop that holds water?

No loop, no water trap, just clear hose direct to fitting.

Did you have an anchor light or windex up there and if so, how did they fare?
Was the radio on-board and damaged?
Was your mast plugged into the deck?

Luckily I guess, the steaming light and radio coax were not plugged in since we had just put the boat in but not sailed. The mast was up. The windex pointer was on the antenna and disappeared with the antenna. I haven't tested the radio (power panel toast) but the small in line fuse to the radio is OK. Some of the bird's nest of lamp cord is damaged.

Everything Moe listed will be inspected, by me, my marine dealer, the insurance adjuster, and possibly a surveyor.

Was there a tank of water connected to your sink?

I think everyone assumes your mast was up, boom attached. Steaming light plugged into socket.

Anything different about the shrouds and stays?

Opinions about path?
Any damage to other boats?

No water tank connected to sink
Mast up boom on, ready to sail

Shrouds and stays look ok but will inspect much more carefully

No damage to other boats but the condo complex 50' away lost power for 11 hours.

Right now it looks like the sink thru hull was the exit path. The hole is still only 3/4 inch but the 4 inches of fiberglass that held the pvc stub pipe to the hull blew off and that area is slightly blackened from heat.

The port bilge has always had little or no water in it. I found it nearly full. so maybe that water came in through the 3/4 in open thru hull during the storm, or maybe there is a new leak.

I'll report more after pulling the boat.[/quote]

[Moe]

If I recall correctly on our X, the lamp cord that came from the battery to feed the entire fuse panel ran right by the through hull for the sink drain on it's way to go up behind the upper liner, just forward of the galley.

Without evidence to the contrary, it appears, at least in this case, the lightning preferred jumping to the circuitous path of the electrical wiring, rather than straight down the attached stainless compression post. That the post isn't bonded to the centerboard hanger, and that one wire of the lamp cord pair everywhere throughout the boat is grounded to the water at the outboard MAY have been factors in this path.

You're fortunate the exit occured above the waterline. Even though the compression post attaches to the centerboard trunk above the waterline, damage could've occurred to the trunk below it, especially had the post been bonded to the centerboard hanger.

Best wishes for no more damage to be found, a cooperative insurance company, and expeditious repairs.

[John McDonough]

Sandusky Ohio, one of the finest sailing area`s. About 1980 I had a old wooden boat in that area and got stuck in a storm out in lake Erie, Lightning flashiing all around, loud thunder and building waves. I was really shook up and when I returned to dock I talked to a 76 year old man who said he has been boating on Erie for 60 years and the only time he ever heard of a boat getting hit by lightning was a 40` sailboaat which was docked in Sandusky Bay and sank in its slip. He saild the lightnig hit the top of the mast and blew a hole out of the bottom. I also recall a few years ago on this forum that a Mac 26X was hit by lightning and when he pulled the boat out of the water he had all kind of blisters around the water line. I cant remember all the detaiil? At least no one got hurt..

[Scott]

That is a brutal story. There has been much speculation on this board and others re: strikes. Excellent to hear a report from one that experienced it firsthand. Not excellent that you had to have the experience to report.

[Dimitri-2000X-Tampa]

Without evidence to the contrary, it appears, at least in this case, the lightning preferred jumping to the circuitous path of the electrical wiring, rather than straight down the attached stainless compression post. That the post isn't bonded to the centerboard hanger, and that one wire of the lamp cord pair everywhere throughout the boat is grounded to the water at the outboard MAY have been factors in this path.

IMO, if the grounding of the engine was a factor, seems like something would have fried in the engine circuits.

Regarding the logic of the compression post not being bonded to the CB hanger, is it bonded to the mast step? If I recall correctly, there is some thick fiberglass between post and mast step but I could be wrong.

Over two decades ago, I was caught once (windsurfing until the last minute when the storm was overhead) on a wet sand beach in Sarasota running for the car when a bolt of lightning hit a lamp post about 10-20 feet in front of where me and 3 friends were scrambling towards the parking lot. I remember being impressed by the width of the bolt, seemed like it was a couple feet in diameter. Also, the shock wave is incredible, knocked all four of us on our tails and everyone thought they had electricity running through their feet from the discharge, I'm pretty sure I felt it up to the knee even though our bodies were not in the direct path of the strike. There were a whole bunch of those little tubes of sand created from the energy.

I guess my point is that electricity will take the shortest path to ground, but that there is so much electricity as well as a huge shock wave, that the energy may have dissipated in many different paths and parts of the boat could have gotten damaged that were not in the direct path.

Another example a bit more recent (maybe 5 years ago) was when a bolt hit a metal pole in my yard while I was at work. My wife was home though and said she heard all the wiring in the house "sizzling" for a few seconds after the strike. The pole is dug deep into the ground and is a good 4 inches thick so plenty of conductivity to ground there, however, there is also an electrical outlet on the pole with a 12 gauge wire running to the side of the house near the pool pumps. This is about a 40-50 foot run. The outlets were all black and charred and I found the same little tubes of dirt spreading outward at the base of the metal pole. The transformer on the pool heater was fried, as well as several switches, a telephone and one TV in the house. After I replaced the outlet, it worked fine again, no apparent problem with the wire running underground. So, even though the strike could have gone directly to ground through the thick metal pole, enough of the energy still went sideways to cause things to break in the house, but not enough energy to melt the 12 gauge wire so obviously most of the energy went straight down.

Makes me wonder if most of the energy in MAC26X's strike still went straight down, but perhaps didn't cause damage significant. Some of the energy may have gone down the stays, etc. but not the bulk of it. Since lightning goes through air, I'm not really sure how much "traditional" conductivity has got to do with it, my guess is that it probably is more important what is the shortest path to ground versus the most conductive medium. Some of the energy likely did exit through the sink drain, but I just don't see how that could have been the bulk of it...assuming it came in through the mast.

[Moe]

Without evidence to the contrary, it appears, at least in this case, the lightning preferred jumping to the circuitous path of the electrical wiring, rather than straight down the attached stainless compression post. That the post isn't bonded to the centerboard hanger, and that one wire of the lamp cord pair everywhere throughout the boat is grounded to the water at the outboard MAY have been factors in this path.

IMO, if the grounding of the engine was a factor, seems like something would have fried in the engine circuits.

Unless along that path the lightning found an alternate route through the through hull?

Regarding the logic of the compression post not being bonded to the CB hanger, is it bonded to the mast step? If I recall correctly, there is some thick fiberglass between post and mast step but I could be wrong.

No, you're right... sort of like a capacitor... except at least one of the bolts that holds the tabernacle to the deck is the same that goes through the compression post upper flange.

[Frank C]

Right now it looks like the sink drain was the exit but I will pull the boat this weekend to inspect the hull.

Aren't the chainplates directly above the galley sink drain? Seems to me the shroud-to-chainplate path was most direct, maybe the most likely main path.