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Lightning Hit my Masthead

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KD4AO
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USA
202 Posts

Initially Posted - 06/10/2008 : 12:29:48

Yesterday evening a pretty bad storm blew through and lightning hit the masthead. It blew the light off and destroyed the plug and socket on the deck but I couldn't find any other damage. The boat was in the water in back of my home, we were in the living room about 40 ft away when it hit, wow what a bang. I looked out a window and could see the masthead light was gone and down on the deck the plug was blown out of the socket and had a small fire burning in it. It was raining very hard and the fire only burned a minute or 2. This morning the only deck damage is just a small black area that looks like it will rub out.

My concern is where did the lightning go from there? It seems it had to get back to earth (water) someway. I am fortunate that I have no through hulls in the water and no electronics that I keep on board except a battery charger which still works and the engine which still runs. The cabin lights still work and there is no damage in the back of the power panel.

Anyone have any good thoughts about where the lightning went?

Bob Townsend

Past C250 Chief Measurer
Past owner of:
C250WK #704
Honda 9.9

Punta Gorda, Fl.

Have a Great Sail!

Edited by - on

Nautiduck
Master Marine Consultant

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Response Posted - 06/10/2008 : 14:13:03

Wow! Glad there is no apparent damage. I do not know where the electricity went but would suggest you lift the boat and look for any possible damage on the hull.

Edited by - on

John Russell
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Response Posted - 06/10/2008 : 14:24:59

What does the radio end of the antenna cable look like? Any arc marks near it? I'd be curious to see what the area around the chainplates look like. What about the keel bolts? You're right, that energy went to ground somewhere. Any chance you can look at the bottom of the keel?

Edited by - on

KD4AO
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Response Posted - 06/10/2008 : 14:49:47

No Radio antenna, and the chain plates and all metal fittings on backstay, forstay and shrouds look fine. Bilge is dry as a bone and the smell inside the boat is that of fiberglass same as before. I expected to smell something smoky inside but all smells normal. When my diver comes out I will have him check the bottom and the keel but even the keel bolts look normal.

Edited by - on

John Russell
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Response Posted - 06/10/2008 : 15:26:17

Another thought I had was the base of the compression post. I realized the mast is stepped on the deck but, we have metal compression posts. I wonder if it could arc through the deck? Although I imagine you'd have smelled something. I hope that Bruce (Passages) weighs in on this.

Edited by - on

piseas
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Response Posted - 06/10/2008 : 16:20:12

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by KD4AO
 the smell inside the boat is that of fiberglass same as before. <hr height="1" noshade id="quote"></blockquote id="quote">
Glad to hear damage limited to light. I have an 03 and always wondered what that smell was. Now I know. But how do we get rid of it?

Steve A
PS must be nice to have boat 40' from home.

Edited by - on

Tom Potter
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Response Posted - 06/10/2008 : 17:16:01

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by John Russell
 Another thought I had was the base of the compression post. I realized the mast is stepped on the deck but, we have metal compression posts. I wonder if it could arc through the deck? Although I imagine you'd have smelled something. I hope that Bruce (Passages) weighs in on this.
<hr height="1" noshade id="quote"></blockquote id="quote">

The mast step and compression post are "one". It bottoms out on a small plate screwed to the cabin sole only inches from the keel bolts on a (WK).

I have always wondered if lighting would travel down the compression post.

KD4AO
I would be curious to know if you find more damage. Please keep us posted.

Compression Post Plate;

Edited by - Tom Potter on 06/10/2008 17:18:58

Dave Bristle
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Djibouti
10005 Posts

Response Posted - 06/10/2008 : 19:00:01

It may have found its way to the keel through the compresion post base screws, in which case you'll probably find some of the coating (polyester resin?) on the keel is missing--blown off to allow the charge to exit to the water. The damage might look like a wide area of pin-holes.

If that path turned out to be too insulated, and the stainless post wasn't a good enough conductor (it's not very good), the lightning might have exited the base of the aluminum mast (excellent conductor) and literally jumped overboard through the wet air. It always finds the most conductive route.

Edited by - on

SCnewbie
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Response Posted - 06/10/2008 : 19:45:09

Discharge via dirt and rain water puddles on the cabin roof and over the hull side possibly???

Edited by - on

GaryB
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Response Posted - 06/10/2008 : 22:40:36

Down the shrouds and then jump to the water or possibly off the top of the mast directly to the water?

When I was a kid lightning struck a cross brace on a power pole behind our neighbors house and then jumped straight to the other neighbors outdoor TV antenna which then blew the front of the TV out. Oddly, this happened twice to the same people in the same way.

I once read an article about the old wives tale that lightning would not hurt you if you were in a car because of the rubber tires. The writer asked a question of the readers "Why do you think a rubber tire would protect you when a lightning bolt travels four or five miles from the top of the cloud to the ground? Another 6 or 8" inches is nothing!" On top of that if it's raining the tire is wet! The real reason is that the metal skin of the car carries the electrical energy around the outside of the car but don't touch any metal in the car. It can still get you!

The new composite panels on airliners and the all composite airplanes require that a metal bonding mesh be installed in the composite material as it's being manufactured. It creates a path for the lightning to follow in the event of a strike. Without it the composite material would disintegrate when struck by lightning.

Edited by - GaryB on 06/10/2008 22:42:40

Arlyn Stewart
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Response Posted - 06/12/2008 : 12:09:40

Probably the reason cars are rarely struck is that lightning more often strikes a leader that provides a shorter path for the discharge. A leader is an upward ionized burn of air caused by electrical charge from the ground seeking the opposite polarity of the clouds. The insulating tires of a car don't provide for the ground to feed such a charge into parts of the car. The ground charge will use tree sap path and send a leader from a tree much more often than from an auto with rubber tires.

However, farm tractors with implements working the soil, and tracked construction equipment are hit by lightning at fairly high rates because being grounded, they do feed the leaders that provide low resistance paths for lightning strikes.

Another factor is the upper surface dynamics of the grounded object. Even if the wet rubber tires convey some charge to the car, metal objects having a broad horizontal surface effectively discharge that charge in a safe way by bleeding the charge to the atmosphere off the area of flat surface. Conversely, metal objects that don't have a broad surfaced to dissipate, collect the charge up on a single dispersion point which is conducive to feeding a leader.

Using this logic, the occupant of an aluminum fishing boat has a higher chance of being struck than the occupant of a fiberglass boat because the aluminum boat can feed a much greater charge from ground to the occupant. Also, the occupant of the aluminum fishing boat who isn't wearing a hat has a higher chance than the fisherman wearing a hat because when his hair stands on end, a single point dispersion point is created from a strand of hair.

Edited by - on

Stardog
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Response Posted - 06/12/2008 : 12:42:17

Recently I read a lot of research about lightening strikes on sailboats. What I took away from it was that the metals on a boat cannot transmit the lightening quickly enough to ground it to water, unless a special lightening protection system is installed, this includes a lot of welding and special bonding. In other words, arcs are not going to jump from one piece of metal to another quickly enough to run the current to ground; once lightening hits the mast it's going to the water in the straigtest path(s) possible. What happens in almost every case (inlcuding protected boats) is that the lightening travels down the mast and at the bottom it shoots out in a radial pattern and goes through the deck, bulkheads and hull directly into the water. I would be looking for burn marks on the hull in particular, they may or may not be plainly visible and they may be in the bilge, behind or under the settees, etc. Another interesting note was that a boat that is going to be hit, will be hit simply due to the fact that at the time it's sitting in a huge electrical charge. Height of mast, or even no mast have no bearing on it, the boat will be hit.

Edited by - on

KD4AO
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Response Posted - 06/12/2008 : 14:08:40

Maybe I didn't get the full strike, only the glass part of the masthead light is missing and as I said the connector blew apart (disconnected, it is still physically there) and burned the pins away. That is all I have been able to find. Question, is Catalina Direct a good place to get the connector or is it a standard WM part as the light probably is?

Edited by - on

Nautiduck
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Response Posted - 06/12/2008 : 14:53:40

Catalina Direct. I buy a couple at a time as they don't last long with people stepping on them and the rubber deteriorates over time in the sun.

[url="http://www.catalinadirect.com/index.cfm?fuseaction=product.display&Product_ID=205"]Deck Connector[/url]

Edited by - Nautiduck on 06/12/2008 14:56:04

aeckhart
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Response Posted - 06/12/2008 : 15:30:52

I had the same thing happen to my C25 several years ago. I lost my radio, fuse panel and a battery. The strike exited the boat at the boot stripe where it left a quarter size and a dime size hole consisting of black powdered fiberglass. There were also about 40 pin head holes with spider cracks in the bottom which I didn't find until after haul-out in the fall. I reemed out the holes with a Roto tool and filled them with epoxy. There was no water entry at all.

I discovered that I had left the master switch on the fuse panel on, which may have contriuted to the strike and or the periperal damage to the electrical system. Lessoned learned.

Edited by - on

GaryB
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Response Posted - 06/12/2008 : 20:30:07

It's amazing to me that a boat can be sitting in the middle of a marina full of masts and get hit by lightning. You'd think one of the boats near the edge of the marina would get hit since the charge travels along the ground below the cloud.

Edited by - on

Turk
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Response Posted - 06/13/2008 : 08:14:57

Several ears ago a friends boat got hit in our bay and sank very quickly. It blue out a thru-hull. The interesting part is, that the lightening travelled out of the boat completely around the waterline. The lightening created thousands of pin holes with spider cracks all around the waterline.

Four feet of mast was showing from shore.

Edited by - Turk on 06/13/2008 08:15:49

KD4AO
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Response Posted - 06/13/2008 : 08:42:04

Thank you everyone for your comments and suggestions. I ordered the connector and light from Catalina Direct (thanks Randy for the link). I will now schedule a haulout and get that done as soon as practical. Its time for new bottom paint anyway so it will be a good time to thoroughly check below the water line. I still feel that the connector popping apart may have prevented the lightning from entering the boat. There is the possibility of the mast conducting it through to the compression post but since the only damage appears to be the light and not the light mounting post, I am holding on to hope that it just disappeared overboard.

Edited by - on

Voyager
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Response Posted - 06/14/2008 : 12:47:52

I've been away and only saw this today. Your experience and that of the forum contributors show you can never tell what's going to happen with a lightning strike. One of nature's mysteries. We may speculate that this was a side bolt or streamer, not the full million+ amp current.

Safe to say, you were lucky. You and your family were not on the boat when the strike hit, and you got away with about $200 damage.

One thing I would check is not only the deck plug & mast top light socket, but also your wiring in the mast which may have partially conducted the current, and the bow light socket, bulb and wiring, if equipped.

You'll know when you replace the socket how much is left of the wire.

Edited by - on

KD4AO
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Response Posted - 03/03/2009 : 15:36:08

I am just now fixing the lightning damage and it is interesting what I am finding. First, there is no damage below deck, not even the lighting. Above deck I found the Nav light bulb blown up, fixture ok but 1 screw holding it to the pulpit had the nut welded to the threads. The stern light bulb was burned out. The deck light bulb was burned out and the Bow light bulb (same fixture)was exploded. The wires and fixture are ok. The Anchor light was burned up and the deck socket and plug were burned up. The lightning hit only the Anchor light and traveled down the wiring. I repaced the Socket and Plug, the wires from panel to deck socket, the Anchor light and all of the bulbs. Every thing works except the anchor light. It has 12v. but appearantly no ground (common) connection from the light to the plug. At this point I think the easiest thing to do is replace the wires from the anchor light to the plug. Question, can someone tell me how the mast is wired inside and specifically where is the ground from the anchor light connected to the ground from the deck/bow lights and the plug? Since the wires are 2 conductor and 3 conductor wires from the fixtures and a 4 wire cable to the deck plug, I suspect it is inside the base of the mast.
How does the bottom of the mast (rubber or plastic) come off so I can see up into the mast?
By the way Catalina Direct had the correct plug and socket but the anchor light they sent was AquaSignal and didn't fit the screw pattern. I suspect the old light was Hellmarine as is the stern light.

I used a home made "A" frame to lower the mast at my dock. I first planned to use Arlyn's fixed "A" frame but changed my mind when I discovered the the stantions I would have to secure it to are exactly the same point fore and aft as the mast and leaning the frame forward a bit just didn't look right. So I rigged the "A" frame base to the stantions and used it in an articulating manner and it worked just fine. Of course I still haven't raised the mast yet, but will soon.

Edited by - KD4AO on 03/03/2009 15:46:15

jbkayaker
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Response Posted - 03/03/2009 : 17:25:42

I recently dealt with installing an antenna wire in my mast. Unless you are skilled and equipped like a laproscopic surgeon the foot has to come off the mast. The mast foot is held on by two aluminum rivets. The heads can be drilled or ground off. Then punch out what is left by tapping with a small machine screw or flat ended punch. When I could not find replacement rivets I tried threading the holes in the two tangs that protrude vertically from the foot. But could not find screws with flat enough heads to allow the mast to fit back into the deck plate. My solution was to buy a piece of aluminum rod stock from Lowes (or Home Depot). Cut it to just fit between the uprights of the mast support. Then hold it vertically on a chunk of hardwood and use a light hammer to tap on the end until it is peened on the top end. Keep peening until it will not fit thru the holes where the rivets were removed. A hundred or so medium taps will gradually mushroom the malleable aluminum. If you whack it too hard the metal will split rather than slowly reform into a round mushroom shape. The bottom end won't get peened if you use wood underneath. Put the rod thru the mast and mast foot where the two rivets were removed. Have someone hold a heavy chunk of metal or stone against the peened end while you tap away on the unpeened end until it mushroomed enough to not slide thru the mast hole. Now you have a single long homemade rivet to hold the foot onto the mast bottom.

Edited by - jbkayaker on 03/03/2009 17:27:44

KD4AO
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USA
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Response Posted - 03/04/2009 : 15:43:56

Problem solved and all lights are now working properly. The problem was that the wiring in the mast did not match wiring at the panel by color. It does now and all is fine. The mast step plate came off as indicated which revealed the connections to the "pigtail" to be just inside the mast. Mast step plate was reinstalled with new 3/16" pop rivets. New hayards and topping lift tomorrow and mast back up on Saturday. Thanks to all who offered advice and comments.

Edited by - on

Steve Blackburn
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Response Posted - 03/04/2009 : 17:00:19

The boat is 40 feet away from your livinig room...and in Florida? Mine is 1.5 hours away and the lake frozen half of the year. I think that is Gods way of showing you that you are having it way too good.

This tends to say that your mast is the highest and most direct path to the ground in that area. Would mounting a flag pole higher than the mast work?

Edited by - Steve Blackburn on 03/04/2009 17:01:20

Arlyn Stewart
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Response Posted - 03/05/2009 : 07:32:33

Steve is on to something... prevention. While we can't predict all of the actions of lightning, man has learned some about its actions and can take some prevention steps.

The primary one is that most strikes are to a leader, an upward ionized bridge and we can sometimes predict where those bridges originate. We know for example that a horizontal metal roofed building tends not to be an origin of such leaders because it bleeds off the charge attracted to it over a wide area whereas a vertical pointed object collects that charge at its tip having little surface to bleed off and thus the charge dissipates upwards in a leader and in doing inonizes a path of air and gives lightning an attractive path to ground.

So, Steve's plan is a good one. Provide a vertical pointed object as an alternative to the boat mast or antenna on it and make the boat mast less of a pointed object or a place that will provide an electrical charge to send a leader. Some ways to do that are to opt for a rail mounted antenna rather than mast top, use an ionizing diffuser on top of the mast and keep the mast from getting a supply of electrons to build up a charge by not having it grounded.

Ham radio ops learned this lesson during the 1970-80s. Two meter FM repeaters became very popular and because they were worked mobile their antenna's were vertically polarized to match the polarization of car whips. The next progression was that hams added a vertical antenna on top of the stinger pole of his home stations tower. The advantage was that the ham could work many nearby cities without any rotator effort. Suddenly, hams started taking lightning strikes in unprecedented numbers on these home stations.

The reason was simple... when the station had a large horizontal beam antenna... charges that were attracted upward dissipated from the large surface area of those beam antennas but with the vertical on top, the charge gathered at the pointed tip of those antenna and lurched skyward as a leader.

As soon as hams adjusted their practice and moved the vertical antennas lower on the mast than the upper beam antenna... life returned to normal with the occasional strike rather than the rash of them.

Edited by - on

Steve Blackburn
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Canada
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Response Posted - 03/05/2009 : 18:56:55

How efficient are top mast mounted Lightning Diffusers? This one from forespar:

http://www.forespar.com/onlineCatalog/2009/Sailboat/sailing_lightingMaster2009.shtml

From Arlyn's excellent explaination this would spread out the ion streamers.

Edited by - Steve Blackburn on 03/05/2009 18:57:51

GaryB
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Response Posted - 03/05/2009 : 20:54:16

From what I've read in the past they work very well. Under the right conditions you can occasionally see St. Elmo's Fire dancing around the diffuser as it bleeds off the charge.

Edited by - GaryB on 03/05/2009 20:54:44

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