Re: Lightning Protection questions

On Nov 11, 7:46 am, "Roger Long" <stri...@xxxxxxxxxxxx> wrote:
If lighting wants to go in a straight line to large masses of metal, my mast
is probably somewhat grounded anyway. There is a lot of lead down there and
the keel is quite wide. Side flash would probably go down into that large
mass and spread out below the top of the encapsulation.

It's not that lightning wants to go straight. It's also not about
resistance. In an earlier question, you asked if a heavier gauge wire
would help. No. The concept is called wire impedance. Increasing
that 8 AWG wire to a heavier gauge does little to decrease impedance.
Shorter wire length - not wire diameter - makes better wire
conductivity.

Bending a wire increases impedance. A quarter round bent wire is an
inductor. Basically zero inductance to electricity such as 60 Hertz
AC. But a massive inductance to lightning.

How much lightning current can an 18 AWG lamp cord wire carry?
Something less than 60,000 amps. Lightning typically is only 20,000
amps. So we run larger 6 or 8 AWG wire to make it sufficient for even
largest lightning.

Routine is to have lightning strikes with no damage and no knowledge
that the lightning even struck. But that means some simple grounding
concepts as discussed in that article. If electronics are damaged,
well, electronics made a lower impedance connection to water; the
damage is how a weakness in that grounding is located and corrected.

Somewhere earlier, you worried about a 6" radius verses 8". Well,
that bend is an inductor trying to stop lightning currents. If
lighting does not travel through that bend, then what wire closer to
the cloud will arc to water (due to a sharper bend closer to water)?
IOW you are worrying about a minor thing. If that eight inch bend is
only feet from the grounding plate, then lightning will still go to
the grounding plate; not through the hull.

I did not see all posts. However there should have been a caution
somewhere about keeping those 8 AWG ground wires well separated from
all other wires. Even factory installers often don't understand this
concept which is why electronics damage occurs. If a ground wire is
bundled with other wires, then lightning induced surges is now on
those other wires (just another in a long list of reasons why plug-in
protectors also don't protection in the home).

Not having metal items bonded to that plate is the worst thing you
can do. Even simple lamp cord can conduct lightning because lightning
does not contain the high energy content so often assumed in myths.
How lightning gets to water is equivalent to "a battle is lost for the
want of a nail". It may not be the best, but it still may conduct
that current non-destructively into water.

One final point. In shallow water, lightning is seeking earth
beneath that water. Water is actually a less conductive material.
Lightning may even pass through the hull rather than use that ground
plate if bottom is closer to some other part of the hull. Just
another reason why we prefer that ground plate to be deeper; closer to
the bottom when in the shallows.

If is quite routine to have a direct lightning strike without even
any appreciable indication that the strike occurred. Lightning
strikes more often without any damage than you might imagine. Do
make metallic items (mast, rails) bonded to that ground plate. Then,
where possible, improve that connection by eliminating sharp bends and
separation from other wires.
.

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