Peter Hendra wrote in
:

I'll add the ground from my stays. By the way, I neglected to tell
that I have a painted box section wooden mast, deck stepped. Forestay,
backstays and capshrouds are electrically connected due to their
attachment at the head of the mast. There is an aluminium sailtrack
which has no connection. Should this be a factor for consideration?


I'd feel better if you'd add a smooth metal cap at the top of the mast to
bleed off static buildup before it causes a strike.

We've learned a lot since the "lightning rod" days, one of the worst
things ever done to protect buildings from lightning. Remember those
sharp-pointed lightning rods that sprayed electrons into the air to
ionize it and GIVE the clouds a path to ground....right at the top of the
flammable barn roof? This was NOT the way to protect buildings!

Today, lightning systems use a grounded, smooth copper flashing that
distributes the electrons along a smooth, long surface to release them
over as wide an area as possible. A pointy grounded thingy ATTRACTS
lightning because there is a concentrated stream of electrons spraying
off the point, ionizing the air above the point...exactly what the cloud
is looking for.

If there's some kind of metal ring at the top of the mast that's grounded
by the various shrouds and stays, that's great. A metal cap that can
take a pretty good strike, might also keep a hit from boiling the sap in
the mast, creating a steam explosion and putting you out of the sailing
business. This alone makes a mast top bypass cap a good thing.

Larry
--

If there's some kind of metal ring at the top of the mast that's grounded
by the various shrouds and stays, that's great. A metal cap that can
take a pretty good strike, might also keep a hit from boiling the sap in
the mast, creating a steam explosion and putting you out of the sailing
business. This alone makes a mast top bypass cap a good thing.

Larry

yes, it is just as you describe, but this generates another question
(sorry). I had often thought of putting a pointed copper rod on top
grounded to the stays as per many books and articles on the matter. I
have never done so because I believed that it would act as an
attractant, rather like Benjamin Franklin's key on the kite string.

Also what got hit first during the lightning strike in Malaysia - the
day we went back into the water before setting out across the Indian
Ocean mind you - was the VHF aerial. the question is - does the damned
thing act as a lightning attractor as it is the highest thing there?

cheers
Peter

Peter Hendra wrote in
:

Ocean mind you - was the VHF aerial. the question is - does the damned
thing act as a lightning attractor as it is the highest thing there?



Yes, it will. But, that's the best place for the best VHF coverage,
unfortunately. Our main antenna got hit, so I moved both of the VHF
antennas to an L bracket in the shadow of the shrouds down the side of the
mast a ways. The VHF antennas are about 4' down the mast, out away from it
about 24 inches between the mast and the shroud, sorta centered. It's
always a compromise, but it seems to work as well there as it did on top,
exposed to the blast. VHF only has to reach to the horizon, you know, as
it's incapable of going further than that radio horizon just over the
visual one. If it meets that requirement, it's fine.



Larry
--

On Sun, 29 Apr 2007 17:53:07 +0000, Larry wrote:


Again, Thanks for this Larry.
I shall do this also, tomorrow morning. It is only a matter of moving
it down.

The one that got hit just vapourised. The replacement I took off here
to paint the mast - it was one of those clamp in wire ones. Spent two
hours hunting for it and decided that it was cheaper to buy a new one.

cheers
Peter
Peter Hendra wrote in
:

Ocean mind you - was the VHF aerial. the question is - does the damned
thing act as a lightning attractor as it is the highest thing there?



Yes, it will. But, that's the best place for the best VHF coverage,
unfortunately. Our main antenna got hit, so I moved both of the VHF
antennas to an L bracket in the shadow of the shrouds down the side of the
mast a ways. The VHF antennas are about 4' down the mast, out away from it
about 24 inches between the mast and the shroud, sorta centered. It's
always a compromise, but it seems to work as well there as it did on top,
exposed to the blast. VHF only has to reach to the horizon, you know, as
it's incapable of going further than that radio horizon just over the
visual one. If it meets that requirement, it's fine.



Larry