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Discussion Starter · #41 ·
I'll admit a sailing ship sloppy with sea water and teasing the clouds with its wobbly metal mast, is not exactly an integrated circuit when it comes to controling current. However, you also must admit, we've been controlling pretty big currents for a while now and we certainly can mitigate damage or at least increase our odds for survival, can't we?

I liked hearing from walsn about his transorbs and their potential good effects.

Cam, you say yourself that an unimpeded path to ground helps. Are you saying: it helps but not enough to spend any money on it?

The answers I get on this may really help in my future purchase decision.
 

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Discussion Starter · #46 ·
OK then, no inordinate amount of attention to bonding. The battery cables sound like a prudent piece of gear and as a spare, at least for my peace of mind. It seems to help when you think you have a plan.

Great pictures bubb.
 

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Some wild axx theory stuff on cables over the side ... cant give a reference and it could be wrong..

You always hear that electricity will take the lowest impedance path to ground and there is no reason to believe this does not apply to lightning. There is an aspect of impedance called "inductance" which needs to be very much considered for the path lightning takes.

Inductance is related to magnetic fields (which a bolt of lightning has) and in a simplified description, is sort of equivalent to resistance for fast changing current. For example, if a conductor has high inductance, it will have high resistance at high frequency. A conductor with low inductance will look like a low resistance at high frequency.

So inductance is very important for the path lightning will take since lightning is transient. A path with low inductance is more likely to be taken than a path with high inductance. At the rates of change of lightning, inductance can be more important than DC resistance.

An interesting thing about inductance from current traveling in a straight line (such as lighting from the bottom of the mast to the nearest water surface) is that the inductance is dependent on both the length of the conductor and the radius of the conductor. The larger the radius, the smaller the inductance (specifically, inductance is proportional to the inverse natural log of radius).

So if you have some copper conductor which goes from the bottom of the mast to water, it must compete with ionized air as a path for the charge to follow. Four gauge wire has a diameter of .204 inch. If the diameter of the ionized air discharge is larger than .204 inches, the ionized air path would in theory have a lower inductance than the wire and for short time periods, represent a lower resistance than the wire. What is the diameter of a ionized discharge from the mast to water - I have no idea. However, you hear of "pin holes" in the side of boats near the water line so maybe this is some indication of the diameter of the ionized air path. Since the diameter of the ionized path would appear to be possibly small, it seems you have some chance of using something like a large diameter wire (like 4 guage or smaller) from the mast over the side and having it lower impedance than ionized air.

The other problem is what happens at the end of the cable in the water - and that is where current patents on lightning protection focus. Battery cable ends likely are not that good for what happens in the water (but that would be speculation on my part).

One other note - trying to clip to shrouds only is in my opinion of no use. The inductance of the shrouds is significantly high compared to the mast and would have little effect of preventing a flashover at the bottom of the mast.
 

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So according to Waltsn is that we are Zapped big time no matter what.
But then again...
A grounding plate on the bottom of your boat and the major metal compotents bonded to it will greatly increase your chance of survivability.


Note this is flat grounding plate. Not the ground plate used for the SSB, which will blow out from the Lightening strike.
 

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Zapped.. dont know. Dont take any of the below seriously, just guessing again...

The natural path for lightning to water is to ionize the water surface and radiate outwards at the surface creating a large area for the charge to eventually resistively "sink in". In this link, Marine Lightning Protection Inc. go down a bit and you can see a discharge into a big tub showing the outward surface pattern. You will see this same effect in a lot of lab pictures.. Ive seen the same thing in our lab here at work using lightning and static discharge simulation equipement.

If you have a big keel and your in salt water, the keel would seem to have enough area and the salt water has low enough resistance that this apears to adequatly discharge lightning charge resistively (water likely does not ionize in the lightning event like air does - hence the "resistive" discharge). Fresh water has "hundreds, even up to a thousands times higher resistance than salt water so the keel resistively disipating charge in fresh water probably just does not work - ie, maybe the keel might need to be a 1000 times more underwater area to work in fresh water which of course is never going to be the case.

But... if the charge on the battery cable were to arc over to the water at the water surface and then spread the charge over a large area by surface air ionization, the battery cable idea might work.. But anything under water with the cable may not be of any help at all.

Once again, Im just guessing here.. have no references.
 

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Actually a Lightening Rod at the top of the mast and bonded to a ground plate on the bottom of your hull will go a long way in protecting you from stray electrical currents set up by a lightening strike.

There is a brush like rod that is suppose to protect you also, but it isn't bonded to anything... But I haven't heard from anyone who has one on their mast.
 

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Some wild axx theory stuff on cables over the side ... cant give a reference and it could be wrong..

You always hear that electricity will take the lowest impedance path to ground and there is no reason to believe this does not apply to lightning. There is an aspect of impedance called "inductance" which needs to be very much considered for the path lightning takes.
............
The problem with lightening is that we assume that it is one bolt and there fore only a single instance we should protect for. But lightening is static electricity and that means when it strikes it bounces around.

First contact may be the lightening rod - other stray contacts will bounce around to spreaders, steel halyards, etc... So there really is no path of least resistance per se.

Grounding plates and either using the keel or the prop shaft as a means of providing a easy out are good in theory - but that only compensates for the big IF - the main charge hits where you expect.

This is all why - all this voodoo it should work in theory is still voodoo safe guarding. Easiest way to protect your electronics is to put a loop in the wire / cables that comes down from your mast so when a strike happens (VHF cable, etc) the loop explodes and minimum current reaches the other areas. Which reminds me since my mast is down - I should put that in practice myself :)

But regardless - all the data we have about strikes and the results have yielded nothing but "in theory" it should do this if you do this solutions... That says that there is no real science between the madness when dealing with this scenario....
 

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turn the motor on to reduce the load on the rig AND make sure I don't ned to rely on my bateries or starter after I get hit! .
Hey Cammy,
I made this point in a previous thread and the Dog told me I was nuts.
There Dog, Cam does it too.
 

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Quote "This is all why - all this voodoo it should work in theory is still voodoo safe guarding. Easiest way to protect your electronics is to put a loop in the wire / cables that comes down from your mast so when a strike happens (VHF cable, etc) the loop explodes and minimum current reaches the other areas."

Jody, if you dont mind, do you have some sort of reference on the loop or where the idea came from? It sounds very familiar to "drip loops" on cables and the purpose is so that condensation on the cable doesnt run into a lower mounted connector.

I cant see how the loop would do much so was wondering where this came from. Was there a case of a loop actually exploding? If the loop was large enough and hooked up in a certain way, it could aid in generating damaging voltage..
 

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All that means is that both you and RV boy are both nuts... :D
Hey Cammy,
I made this point in a previous thread and the Dog told me I was nuts.
There Dog, Cam does it too.
 

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If you are that worried about Lightening then find the Deepest cave in your country (and all countries have a few caves) and hide there
 

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Bonding and grounding are two very different things. Bonding is the process of connecting all the metal bits to each other to prevent galvanic problems. And some pros would prefer not bonding--because it can increase lightning damage by tying everything together in one path.

Grounding doesn't seek to prevent galvanic problems, it seeks to channel heavier power directly to the water under the boat. Different purposes--even if in practice they may be the same system on a boat. But the lighting ground would typically be a heavy cable running from the mast (or mast step on the deck) straight down to a keel bolt (for an exposed keel) and that might or might not be tied into an optional bonding wire.

Radios don't need an electrical ground of that type, they may be grounded or they may use a counterpoise which stays inside the boat but is capacitively coupled to the water under the hull. No direct contact needed at radio frequencies. Or, they may go to a DynaPlate, which is sintered bronze bolted on externally. Great for a radio ground--but a lightning strike can cause it to explode as the water inside it superheats into steam.

The folks who play radio for a living, with big towers and transmitter sites that can't be offline, use protective devices to shunt the lightning to ground. Most boaters wouldn't bother when you can use the old radio operators' procedure, which is to disconnect the antenna cables and power lines, and plug them right into a ground connection. So if your VHF antenna is on the mast and it runs into the cabin along the mast? You cut it, right there, and splice in a couple of connectors. When you leave the boat (or expect lightning) you disconnect the antenna from the radio, then connect it (at the mast) to another solid cable going straight down to a keel bolt. If it gets hit, the strike should keep going straight down, blowing up the antenna but not detouring into the radio and electronics. In theory, most of the time, anyway.

And while there is a large static buildup before a lightning strike (if you just disconnect the antenna cable behind the radio, you may still see an arc and a multi-hundred volts strike come out of it, from static buildup) lightning isn't static electricity in the "doorknob" sense. It is the huge static charge built up between the earth and the atmosphere, coming up & down an ionized air path with a jillion volts and amps and pretty much doing what it pleases.

All the research adds up to ways to minimize or discourage damage--but there's no way to absolutely prevent it for small craft.
 
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