Lightning Vulnerability for Steamboats.

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Re: Lightning Vulnerability for Steamboats.

Post by Centurion » Thu Jul 20, 2017 12:06 am

Bob Cleek wrote:I'd expect a drunken fool going full tilt in a speedboat would be a much greater worry than a lightning strike. It seems the conventional wisdom on lightning strikes on smaller vessels is that on the rare occasions it occurs, the electrical discharge hits the highest metal and then runs in a cone shape (especially with a sailboat's metal standing rigging) to the water. For this reason, it's not advised to bond a metal mast to the keel, as electricity will then run down the mast into the interior of the boat and through the electrical system, frying all the electronics on board. The stack on the average steam launch will likely be so close to the water that the lightning bolt would go for the water before it did much damage to the boat. I've been in the game for over fifty years and I've never heard of a boat sunk by a lightning strike that blew a hole in its bottom, but don't go by me.
As I said, I'm a newbie with no concept of the lightning risk to steamboats. You've made me feel much better. Still will not intentionally steam into lightning, though.
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Re: Lightning Vulnerability for Steamboats.

Post by Mike Cole » Thu Jul 20, 2017 3:07 pm

fredrosse wrote:In Google, look up "lightning damage", and click on "images", you will find answers to most of your questions there. Lightning is usually not so damaging, but anything can, and has, happened. I think the great majority of steamboats would sink with a big hole, I have not seen flotation on them.
It is the bit above that worries me, having no built in buoyancy . I have 4 build in compartments in my sub 18 foot boat. I expect any boat i am in not to sink if there is a hole in the hull.
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Re: Lightning Vulnerability for Steamboats.

Post by fredrosse » Thu Jul 20, 2017 7:24 pm

Flotation vs. Cost and loss of boat internal space, take your choice. Flotation has never been employed on the many boats (US Army Engineer district , dredging operations), from 20 ft survey boats to 125 ft tugboats that I have been involved with. If they are seriously holed, they sink. We all carry life jackets, so loss of life is not too probable, especially on the generally mild trips we make on our steamers.

I have considered completely flooding the Margaret S to see if it would remain afloat, being a boat with plenty of wood. Might have to completely blowdown to add the buoyancy of an empty boiler! Nice to realize I could do that with virtually no harm to anything on the boat, I could completely submerge the burner system, fuel tanks, water tanks, boiler, valves, etc. with no harm, just a lot of things to dry out after the experiment.



What is the general flotation condition on regular pleasure boats, say outboards and inboards 18 to 40 feet long, do they have positive flotation?
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Re: Lightning Vulnerability for Steamboats.

Post by DetroiTug » Thu Jul 20, 2017 9:06 pm

Fred, I think all pleasure craft i.e. skiboats etc are required by law to have level flotation.

What would happen to Iron Chief with a big hole in the hull? :lol: nothing good.

Maybe get some of these:

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Re: Lightning Vulnerability for Steamboats.

Post by Lopez Mike » Fri Jul 21, 2017 3:04 am

I live in an area where lighting is really, really rare so I have no personal experience. But . . .

I friend of mine was tied to a dock in Chesapeake Bay in his son's Catalina 27' sailboat when it was struck. The effects were rather dramatic.

The noise was stunning. No one felt anything electrical. Water started gushing into the fiberglass boat. A thru hull had been blown off leaving about a three inch hole a foot or so below the water line. He dove overboard with a throwable square life preserver/cushion and held it over the hole until a couple of lines could be rigged to hold it in place.

Among the surprises was finding a bunch of electrical debris in the V-berth at the front of the boat. On examination it turned out to be parts of the engine alternator. How it got out of the engine compartment is a mystery. Some opening must have blown open enough to let the parts out and them closed itself.

Anything remotely electrical was dead including a battery powered alarm clock. Who knows?

The bolt hit the top of the mast and then went hither and yon having a great time frying things.

The rule of thumb about being protected by a mast or stack is that you get a foot of protection sideways for each foot hight of the mast/stack. So in my boat when I'm in the stern lording it over everything I get little protection from the stack.

My friend returned to the Northwestern U.S. where I live quite grateful for the lack of such weather.
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Re: Lightning Vulnerability for Steamboats.

Post by PatJ » Thu Jul 27, 2017 8:56 am

A work acquaintance of mine had his ski boat out on a lake in the SE usa, and he had a radio antenna.

He said it was not a particularly bad weather day, but one odd looking dark cloud floated over, and lightning struck the antenna mast.

At the time his two sons were in the water about to water ski, and they were shocked around the neck area, but not seriously injured.

A young girl in the boat had her hand on the aluminum handrail, and it burned her hand from the heat of current flow, but again not a serious injury.

All the electric items on the boat were destroyed, such as the radio, the ignition coil, etc.

The fiberglass hull was not damaged, and so they were very lucky that day that they had no serious injuries.

As I understand it, lightning often follows ionization paths in the air, which can be caused by hot and cold air meeting and other causes.

There is a photo on the net somewhere that shows lighting traveling horizontally and striking at the base of the space shuttle while it was fueled and sitting on the launch pad.

Lightning will put down feelers to find the best conductive path first, so if you feel your hair standing on end, flatten yourself on the floor/ground.

Most lightning consists of a main strike and many less branch paths.
And the initial strike may be from earth to ground, or vice versa, with a downstrike often followed by an upstrike, or perhaps the reverse of that.

The lightning protection on buildings consists of lightning rods with copper down conductors, and these conductors provide a solid path for the lightning to travel along, instead of searching around for the best path and overheating everything it flows in. The trick with downwires is to not make any sharp bends in then, and always keep them going downwards. Never take a downwire down and then back up again.

I would guess that a lightning rod on the top of the stack with the proper downwire connected to a metallic plate on the bottom of the hull would route the vast majority of any strike safely around the boat, just as it does with buildings, barns, etc.

I think Franklin came up with lightning protection for barns, and it worked well, and still does to this day.

The heat generated with electrical current is (I squared R), with I being the current and R being the resistance.
So a low resistance path does not produce much heat, and thus does not start fires like a high resistance path.
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Re: Lightning Vulnerability for Steamboats.

Post by Lopez Mike » Thu Jul 27, 2017 1:50 pm

All good information. The one thing that I might add to that is that one of the primary functions of lightning rods is to prevent the protected structure from being hit in the first place. The heavy conductor to ground is a backup function.

The way that this works is that a properly designed rod has a sharp point or many points and these points cause the charge to bleed off thus making the protected structure seem much lower compared to the surrounding terrain. That sharp point function was discovered by, of course, Franklin!

On aircraft you will see what looks like little brushes trailing back from the rear corners of the wingtips. Horizontal lightning rods.
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