Lightning protection (again), water and swimmers
 

Following on from the recent discussion of lightning strikes what is the
expert opinion here of what to do when a storm arrives and you're swimming?

The instant reaction of almost everyone today was to get out of the water
but I have a nagging doubt. In the water I was not going to provide a
preferential path to earth, although a strike would have caused the
potential of the whole lake to rise surely I would have simply floated with
it.
Out of the water I was standing on the bank soaking wet and probably more of
a target for a strike, a few mm of wet neoprene certainly wasn't going to
protect me.

So what have I missed?

Lightning protection (again), water and swimmers
 

On 7 July, 22:21, "Calvin Sambrook" wrote:
Following on from the recent discussion of lightning strikes what is the
expert opinion here of what to do when a storm arrives and you're swimming?

The instant reaction of almost everyone today was to get out of the water
but I have a nagging doubt. *In the water I was not going to provide a
preferential path to earth, although a strike would have caused the
potential of the whole lake to rise surely I would have simply floated with
it.
Out of the water I was standing on the bank soaking wet and probably more of
a target for a strike, a few mm of wet neoprene certainly wasn't going to
protect me.

So what have I missed?



You've missed a chance at immortality by being the man who discovered
the answer!

Lightning protection (again), water and swimmers
 

On Tue, 7 Jul 2009 22:21:49 +0100, Calvin Sambrook wrote:

Following on from the recent discussion of lightning strikes what is the
expert opinion here of what to do when a storm arrives and you're swimming?

The instant reaction of almost everyone today was to get out of the water
but I have a nagging doubt. In the water I was not going to provide a
preferential path to earth, although a strike would have caused the
potential of the whole lake to rise surely I would have simply floated with
it.
Out of the water I was standing on the bank soaking wet and probably more of
a target for a strike, a few mm of wet neoprene certainly wasn't going to
protect me.

So what have I missed?

Breathe through a non-conductive snorkel and wear one of these on your
head:
http://www.by-the-sword.com/acatalog/info_300064.html

Lightning protection (again), water and swimmers
 

On Jul 7, 10:21*pm, "Calvin Sambrook" wrote:
Following on from the recent discussion of lightning strikes what is the
expert opinion here of what to do when a storm arrives and you're swimming?

The instant reaction of almost everyone today was to get out of the water
but I have a nagging doubt. *In the water I was not going to provide a
preferential path to earth, although a strike would have caused the
potential of the whole lake to rise surely I would have simply floated with
it.
Out of the water I was standing on the bank soaking wet and probably more of
a target for a strike, a few mm of wet neoprene certainly wasn't going to
protect me.

So what have I missed?

A strike in water is almost bound to be fatal, the voltage developed
across the water will be high. Same thing happens on a far smaller
scale when a heater is dropped in a bath.

If there really is nothing higher than the water around, youre in
trouble either way: stay in and get fried, or get out and become the
tallest object in the area.


NT

Lightning protection (again), water and swimmers
 

wrote in message ...
On 7 Jul,
"Calvin Sambrook" wrote:

Following on from the recent discussion of lightning strikes what is the
expert opinion here of what to do when a storm arrives and you're
swimming?

The instant reaction of almost everyone today was to get out of the water
but I have a nagging doubt. In the water I was not going to provide a
preferential path to earth, although a strike would have caused the
potential of the whole lake to rise surely I would have simply floated
with
it. Out of the water I was standing on the bank soaking wet and probably
more of a target for a strike, a few mm of wet neoprene certainly wasn't
going to protect me.

So what have I missed?

I was swimming in a lake last week as a thunderstorm approached. I got out
well before it arrived.

Water does not have zero resistivity. If there is a strike on the water a
potential difference will appear across you in the water. This will most
likely be enough to pass more than 30ma through your body. This is highly
likely to be fatal.

Best place either in a car, or curled up in a ditch out of the water.


Thanks for that, I knew I'd missed something. It does raise the question of
why fish aren't affected though.

Lightning protection (again), water and swimmers
 

It is possible to estimate how far away you need to be from a
lightning strike while immersed in water and be reasonably safe.

The typical current in a lightning strike is about 30kA with a worst
case of about 300kA. The resistivity of seawater is 0.1 to 0.5 Ohm.m,
but the resistivity of lake waters varies from 100 to 400 Ohm.m.

Assume the lightning strike is a point source of current spreading
into a uniformly resistive hemisphere. There will be some distance at
which the potential difference between two points separated by say 2m
is at a level considered to be safe. A "safe" voltage is probably
somewhere in the region of 10 to 50V.

From "The Art and Science of Lightning Protection" by Uman, the
voltage between two points at distances a and b from the lightning
strike is

Vab = rho.I(1/a - 1/b)/2.pi

So in seawater with 0.5 Ohm.m resistivity for a 30kA lightning strike
at a distance of 20 to 22m the peak voltage drop will be about 11V.

However, in a 400 Ohm.m lake at 20m from the strike, the voltage drop
across 2m of water will be about 9kV.

At a range of 100m, in the 0.5 Ohm.m seawater the voltage drop will be
0.5V whereas in the 400 Ohm.m lake it will be about 370V.

I would get out of the lake!

John

Lightning protection (again), water and swimmers
 

NT wrote:
On Jul 7, 10:21Â*pm, "Calvin Sambrook" wrote:
Following on from the recent discussion of lightning strikes what is the
expert opinion here of what to do when a storm arrives and you're swimming?

The instant reaction of almost everyone today was to get out of the water
but I have a nagging doubt. Â*In the water I was not going to provide a
preferential path to earth, although a strike would have caused the
potential of the whole lake to rise surely I would have simply floated with
it.
Out of the water I was standing on the bank soaking wet and probably more of
a target for a strike, a few mm of wet neoprene certainly wasn't going to
protect me.

So what have I missed?

A strike in water is almost bound to be fatal, the voltage developed
across the water will be high. Same thing happens on a far smaller
scale when a heater is dropped in a bath.

So how many people have actually been killed by a 'heater' (presumably
electric) being dropped in the bath? I suspect that in reality the
person dropping the heater is more at risk than the person in the bath.

--
Chris Green

Lightning protection (again), water and swimmers
 

In article ,
"Calvin Sambrook" writes:
wrote in message ...

Water does not have zero resistivity. If there is a strike on the water a
potential difference will appear across you in the water. This will most
likely be enough to pass more than 30ma through your body. This is highly
likely to be fatal.

Your body, being loaded with salts, is a better conductor than fresh
water, so the current will preferentially go through you.

Best place either in a car, or curled up in a ditch out of the water.


Thanks for that, I knew I'd missed something. It does raise the question of
why fish aren't affected though.

They are. A standard fishing technique is to generate a current through
the water which stuns/kills the fish, and you simply pick up the ones
which float to the top.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Lightning protection (again), water and swimmers
 

On 9 July, 08:40, (Andrew Gabriel) wrote:

A standard fishing technique is to generate a current through
the water which stuns/kills the fish, and you simply pick up the ones
which float to the top.

Arguably, a grenade is equally effective and more fun.

Lightning protection (again), water and swimmers
 

On Jul 8, 6:18*am, NT wrote:
A strike in water is almost bound to be fatal, the voltage developed
across the water will be high.

More likely a popular myth. In one situation, lightning struck
water containing scuba divers. Those who were touching the bottom
were shocked. Those floating freely in water apparently did not know
lightning struck. Makes sense once one learns the underlying
principles.

Lightning protection (again), water and swimmers
 

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember saying something
like:

So how many people have actually been killed by a 'heater' (presumably
electric) being dropped in the bath?

According to the movies and cheesy whodunnits, lots. In reality, I've no
recall of it actually happening, but the newspapers love to perpetuate
old myths.

Lightning protection (again), water and swimmers
 

On 11 July, 16:26, Grimly Curmudgeon
wrote:
////

So how many people have actually been killed by a 'heater' (presumably
electric) being dropped in the bath?

According to the movies and cheesy whodunnits, lots. In reality, I've no
recall of it actually happening,

Circa late 1970s/ early 1980s, the late Lady Barnet of What's My Line?
TV program fame killed herself by arranging for a wall elec heater to
drop into her bath.

She lived in a very pleasant late Victorian house with its own grounds
in Cossington, Leicestershire, opposite the vets. I know because my
cat escaped into her garden from the vets!!

Her suicide occurred after a widely reported case when she was accused
of shoplifting.

but the newspapers love to perpetuate
old myths.

no myth

Lightning protection (again), water and swimmers
 

jim wrote:
On 11 July, 16:26, Grimly Curmudgeon
wrote:
////

So how many people have actually been killed by a 'heater' (presumably
electric) being dropped in the bath?

According to the movies and cheesy whodunnits, lots. In reality, I've no
recall of it actually happening,

Circa late 1970s/ early 1980s, the late Lady Barnet of What's My Line?
TV program fame killed herself by arranging for a wall elec heater to
drop into her bath.

She lived in a very pleasant late Victorian house with its own grounds
in Cossington, Leicestershire, opposite the vets. I know because my
cat escaped into her garden from the vets!!

Her suicide occurred after a widely reported case when she was accused
of shoplifting.

but the newspapers love to perpetuate
old myths.

no myth

I can find little hard evidence for the method of her suicide though
I'm willing to be corrected if you can point me to something.

--
Chris Green

Lightning protection (again), water and swimmers
 

wrote:
jim wrote:
On 11 July, 16:26, Grimly Curmudgeon
wrote:
////

So how many people have actually been killed by a 'heater' (presumably
electric) being dropped in the bath?
According to the movies and cheesy whodunnits, lots. In reality, I've no
recall of it actually happening,
Circa late 1970s/ early 1980s, the late Lady Barnet of What's My Line?
TV program fame killed herself by arranging for a wall elec heater to
drop into her bath.

She lived in a very pleasant late Victorian house with its own grounds
in Cossington, Leicestershire, opposite the vets. I know because my
cat escaped into her garden from the vets!!

Her suicide occurred after a widely reported case when she was accused
of shoplifting.

but the newspapers love to perpetuate
old myths.
no myth

I can find little hard evidence for the method of her suicide though
I'm willing to be corrected if you can point me to something.

http://www.time.com/time/magazine/ar...950505,00.html

Lightning protection (again), water and swimmers
 

Andy Burns wrote:
wrote:
jim wrote:
On 11 July, 16:26, Grimly Curmudgeon
wrote:
////

So how many people have actually been killed by a 'heater' (presumably
electric) being dropped in the bath?
According to the movies and cheesy whodunnits, lots. In reality, I've no
recall of it actually happening,
Circa late 1970s/ early 1980s, the late Lady Barnet of What's My Line?
TV program fame killed herself by arranging for a wall elec heater to
drop into her bath.

She lived in a very pleasant late Victorian house with its own grounds
in Cossington, Leicestershire, opposite the vets. I know because my
cat escaped into her garden from the vets!!

Her suicide occurred after a widely reported case when she was accused
of shoplifting.

but the newspapers love to perpetuate
old myths.
no myth

I can find little hard evidence for the method of her suicide though
I'm willing to be corrected if you can point me to something.

http://www.time.com/time/magazine/ar...950505,00.html

Which says nothing about the method at all (like all the other
references I could find), it just says:-

Four days later, she was found electrocuted in her bath,
apparently a suicide.

--
Chris Green

Lightning protection (again), water and swimmers
 

On 14 July, 18:43, wrote:
Andy Burns wrote:
wrote:
jim wrote:
On 11 July, 16:26, Grimly Curmudgeon
wrote:
////
snip

*but the newspapers love to perpetuate
old myths.
no myth

I can find little hard evidence for the method of her suicide though
I'm willing to be corrected if you can point me to something.

http://www.time.com/time/magazine/ar...950505,00.html

TFT - ties down the date to Oct 1980.

Which says nothing about the method at all (like all the other
references I could find), it just says:-

* * Four days later, she was found electrocuted in her bath,
* * apparently a suicide.

At the time both the case and the inquest received detailed coverage -
including an indication as to how she had made the elec fire fall off
the wall above the bath - in the local rag (the Leicester Mercury), as
well as passing notes in the nationals.

Unfortunately the on-line Merc archive doesn't stretch back that far
(by a long way). So if you really doubt my memory you need to either
(1) visit the Merc's offices & ask to check back issues (if they will
let you) or (2) visit the Leicester Ref Library - or perhaps the Leics
Record Office or (3) visit the Brit Lib Newspaper Reading Rooms in
Collingdale.

I didn't often see the Loughborough Echo which also has Cossington
within its area, but should have expected that also would have given
the matter detailed coverage. So that's a second source for you. And
aren't there official inquest records somewhere too?

Fortunately I moved away from Leics in the mid 80s, otherwise I'd do
the lookup for you.

Even so the matter still sticks in my craw. Two reasons. One was
that my cat's escape & several searches of her garden imparted a vivid
recollection of the 'crime scene'. T'other was that electrocution
seemed, and still seems, an extraordinary suicide choice for a doctor
to make.

And even if by some bizarre circumstance the fire fell off the wall by
itself & it wasn't suicide, there is no doubt she was electrocuted in
her bath.

Funny though, the doubt I have about the ref quoted above lies not in
the suicide, but IIRC Lady Barnet was found not guilty by the local
magistrates - not convicted by a jury. Which factoid also still
sticks in my craw. Possibly because reports in the local rag left one
with a definite feeling that she had had a lucky 'got off' (or 'let
off'?). Not that that was a great surprise as she was, or had been, a
magistrate herself.

Lightning protection (again), water and swimmers
 

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember jim
saying something like:

Circa late 1970s/ early 1980s, the late Lady Barnet of What's My Line?
TV program fame killed herself by arranging for a wall elec heater to
drop into her bath.

She lived in a very pleasant late Victorian house with its own grounds
in Cossington, Leicestershire, opposite the vets. I know because my
cat escaped into her garden from the vets!!

Her suicide occurred after a widely reported case when she was accused
of shoplifting.

but the newspapers love to perpetuate
old myths.

no myth

We need a guinea pig.

Drivel!

Lightning protection (again), water and swimmers
 

On Thu, 16 Jul 2009 13:37:38 +0100, Grimly Curmudgeon wrote:

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember jim
saying something like:

Circa late 1970s/ early 1980s, the late Lady Barnet of What's My Line?
TV program fame killed herself by arranging for a wall elec heater to
drop into her bath.

She lived in a very pleasant late Victorian house with its own grounds
in Cossington, Leicestershire, opposite the vets. I know because my
cat escaped into her garden from the vets!!

Her suicide occurred after a widely reported case when she was accused
of shoplifting.

but the newspapers love to perpetuate
old myths.

no myth

We need a guinea pig.

Drivel!

Only valid on a human being.
--
Peter.
The head of a pin will hold more angels if
it's been flattened with an angel-grinder.

Lightning protection (again), water and swimmers
 

In message , Grimly
Curmudgeon writes
We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember jim
saying something like:

Circa late 1970s/ early 1980s, the late Lady Barnet of What's My Line?
TV program fame killed herself by arranging for a wall elec heater to
drop into her bath.

She lived in a very pleasant late Victorian house with its own grounds
in Cossington, Leicestershire, opposite the vets. I know because my
cat escaped into her garden from the vets!!

Her suicide occurred after a widely reported case when she was accused
of shoplifting.

but the newspapers love to perpetuate
old myths.

no myth

We need a guinea pig.

Drivel!


You can't have an experiment without a control

Dennis !


--
geoff