Conference unifix::sailing

>>>  Although larger (sail)boats have lightning protection can something
>>>  be effectively rigged up for smaller boats?

Small Boat Journal in the past year or so had an article about this very 
question.  I don't recall the specifics, other than discussion about how 
unpredictable lightning is, and some diagrams of heavy copper leads 
attached to the shrouds and tossed overboard.

>>>  What would happen if a small boat gets a direct hit to the mast with
>>>  people huddled in the cabin below?

Having been aboard (and inside) a boat hit by lightning, albeit 33' LOD, I 
was fine other than suffering temporary hearing loss.  On another occasion 
in an open boat whose wooden mast was hit, the current apparently 
travelled down one of the shrouds and arced over the rain-soaked deadeye 
lanyards and then down the hull to the water -- or so we thought at the 
time.  The person standing 6' away on the other side of the mast, hanging
onto the other shroud (!), was zapped and *very* surprised, but apparently
uninjured.  My own impression is that a wet hull on the outside of you is
likely to carry most of the current, but there are cases of holes being
blasted in fibreglass (perhaps around moisture pockets in the laminate??)
and other less-than-encouraging outcomes.  It seems most true that with
lightning, you just never know. 

>>> What was the mild ZING of electricity we felt?  Was it a precursor
>>> to a lightning strike?  I've read that the strike actually starts at
>>> the ground and jump up to the clouds.

I've felt little tingles at times when lightning has struck nearby and a 
groundstroke has made its way underneath me.  The funniest example (true!) 
was when I was standing taking a leak in the flush head at camp around age
10, and lightning hit the lake 800' away into which the heads all flushed.
Wow!...now that's a new charge for a young man! 

J.

    A quickie comment...why did you strike out for home in the first
    place?  Lightning storms not only produce lightning and noise but
    can often whip up winds over 60 mph plus a nasty microburst or two.
    Back in '82 I was knocked flat by a local thunderbumper and hadn't
    even seen a flash at the time.  I'm chicken when it comes to this
    sort of thing...I would have stayed on the beach.
    
    On grounding, most large boats do have ground wires that connect
    the mast and  all shrouds to the keel.  Whether these work well or not
    is a function of the original design and maintenance.  The mast is the
    most favored route for the zap to take but I've seen a few boats that
    grounded everything except the mast.  Exterior ballast makes a fine
    ground plate but many boats with interior ballast (molded in) still
    have the grounds tied into the ballast.  All boat wiring takes a
    hell of a beating, given the environment, and I don't know of many
    people who spend much time maintaining the electrical continuity
    of their grounding systems...I'll bet that most owners have never
    given it a thought.  Sailors all seem to lead charmed lives.  

As I recall the grounding of the mast and shrouds actually increases the risk
of being hit by lightning (right?). However, this grounding reduces the chance 
for serious damage as it routes the strike safely to the ground.  This is why
I feel nervous about being hit but comfortable about the boats ability to 
survive it.

(This is a good case for having a hand-held VHF as the regular set will probably
get knocked out - as happened to a boat in our mooring area in 1983).

Does anyone have a lightning deflector (or whatever it's called) at the top of 
the mast?  (It's merely a metal post with a conical shape at the top to deflect
 a direct hit).  I remember coming across this in a power squadron course a few 
years back.

bc  (who thoughly enjoys a good lightning storm as long as I'm not underway!)

>>> It's merely a metal post with a conical shape at the top to deflect
>>> a direct hit.

Huh? 'Taint no way no how a little piece of metal is gonna deflect a 
lightning bolt. 

A surveyer suggested to me, when lightning is around and about, clamping 
one end of a length of chain to a mast shroud and dropping the other end 
over the side. Lightning is most likely to hit the masthead, and the
shortest, lowest resistance path to ground (ie, the ocean) is that path
that the lightning will (usually) take. 

    Any boat with thru-hulls will have them grounded.  It has been known
    to happen that having been hit by lightning a thru-hull fitting
    has been blown out.
    
    A conical shape metal at the top of the mast "with a pointed end"
    will allow tghe negitive charge to reach the atmosphere.  A chain
    clamped to the mast hung overboard will direct to charge to the
    water as the easiest path vs the hull.
    
    Remember to disconnect all antenna leads from the electronics.
    
    
    jay

    RE .4
    
     Is there any particular shroud the chain would be best connected
    to, ie. outer vs. inner? And was there a recommended method to
    clamp the chain to the shroud?

.1 

You MUST be living a charmed life.  Sounds like you have had you share 
of electrifying experiences!


Could someone send me a copy of the SMALL BOAT article mentioned?
thnx. 
	Larry Pearl
	ZKO2-3/Q08

.2
On the decision to leave the beach, here's what was going on in my 
head:

	- Could we beat the storm home? Or maybe, if lucky, get 
	  out of its path?  Let's get the Hell out of here! 

	- We were motoring, not sailing.  Although even as we
	  were heading for the cruisers I saw some people still
	  with sails up!  

	- The anchorage are was too crowded with boats.  There were plenty of
	  less crowded protected anchorages along the way.  I didn't want
	  to be bashing into other boats if things got crazy.

	- Do you think we should have just stayed out in the open 
	  on the beach?	 I was thinking about the lifeguard killed
	  on the beach earlier this summer!

	  I guess in a 40 - 200mph microburst we would have been safer
	  on the beach than in a boat.

	  About 15 years ago (1974?) I was luckily 
	  tied up to the public dock in Marblehead when a nasty
	  squall struck; no lightning, as I recall, but blinding
	  rain (the heaviest I remember) and high winds.  Scores
	  of boats were capsized and several driven up on the rocks
	  by the lighthouse.  

	  Many scared people were rescued and one person died off
	  Salem Willows, trapped in an overturned 24ft cabin cruiser
	  tied up at the pier.   Some say it was a tornado.  At the
	  Willows Yacht Club several large metal storage lockers
	  (8ft x 4ft)	filled with such things as 
	  outboard motors were picked up and tossed about like
	  a child's toys.....a bit scary!
	  
	
ps

	Last night, as a token of our appreciation, I dropped off a
	case of Heineken and a bottle of Southern Comfort
	(seemed appropriate) to the cruiser who let us onboard!

re .4, .6:

The surveyer didn't suggest how to clamp the chain to a shroud (I assume 
a small wire rope type clamp would work find) nor did he suggest which 
shroud (I assume a leeward one to minimize the bashing of the chain on 
the topsides -- perhaps the first few feet of the chain should be inside 
a vinyl hose to protect the topsides).

    
>     Is there any particular shroud the chain would be best connected
>    to, ie. outer vs. inner? And was there a recommended method to
>    clamp the chain to the shroud?

	Wasn't the recomendation to clamp the chain to the MAST?  It seems
that with the incredibly high currents involved in a lightning strike,
that you want as much cross section to the path of current.  I would guess
that the mast (metal I presume) would have a lot more current capability than
the shouds.  Instead of chain wouldn't a length of the biggest diameter
copper cable you can manage that has a bolt terminal at the mast end to
which you quickly bolt it to a prepared fitting on the mast and the other
end stripped back and dumped in the drink.  This will leave the cable
jacket intack to protect the topsides.  You could even put some kind of
'surface area' on the wet end to lower the resistance in the cable/salt water
connection.

	Dave

I would guess that the surveyer's recommendation was based on the 
thought that we all have (or should have) a length of ground tackle 
chain already aboard the boat. I assume that a hefty wire would work as 
well. But, as I recall, number 8 wire is suggested for grounding all the 
pieces of the boat. Lightning is very high voltage -- it may actually be 
rather low current.

RE:.10 by MSCSSE::BERENS "Alan Berens"

> Lightning is very high voltage -- it may actually be rather low current.

I wouldn't count on it.  No way.

Lightning often has a peak current on the order of thousands of Amps.  I've
seen #14 copper wire that had been partially melted by a lightning strike.
I have a great deal of respect for the voltage,  current and power of an
average lightning strike.


Phil

    	I the last electrical storm we were in, we clipped car jumper
    cables to the mast and toss the other end over the side.  Would
    this help or did it just give us a false sense of security?
    
    						=Ralph=

    According to the Navy, grounded metal structures are less likely
    to be struck than ungrounded or poorly grounded ones.  If I recall
    the reationale correctly, it stemmed from the belief that by being
    able to neutralize nearby charged air, one creates an environment
    where a strike is less likely, and if a strike occurs anyway, a
    direct high current path to minimize the spread of the charge.
    
    I lived for several years in Charleston, SC where lightning destroyed
    or damaged an average of 1 tall pine a year on our 1 acre property. I 
    became interested in HAM radio and constructed a very large, well 
    grounded Yagi for the 10 meter band, which was on a tower slightly 
    higher than the 50-70 foot surrounding Pines.  I never experienced a 
    strike after that that time, although some of the neighbors claimed 
    similar numbers.  This seemed to roughly confirm the reduced incidence of
    strikes theory put forward in the Navy.
    
    I believe the jumper cables over the side provide are a better
    protection mechanism than nothing.

    Walt

    I believe the Seven Seas Cruising Assoc. had an article written
    by Chuck Scott giving a very detailed description on this within
    the last year.
    
    jay

    re .13:
    
    You are quite right, the lightning conductor (conical devices, masts,
    grounding wires, chains etc.) is really intended to *slowly* discharge
    the immediate area by leaking those nasty electrons into the atmosphere
    and equalising the charge.
    
    So those with a lightning conductor should be safer.
    
    However, the energies and predictability of electrical storms are
    a massive variable. One can only go by statistics. Therefore, get
    grounded. It's like wearing a seatbelt in a car, statistics show
    that you will be much safer from injury in an accident.
    
    Cheers,
    
    Ray

    Dumb question #47
    
    If the standing rigging is grounded to the keel (external lead),
    what are the chances that if you are struck by lightning a large
    hole in the plastic will be burned around the keelboat? My concern
    is that large amounts of water will come through such a hole or
    that the keel may be loosened (if there is such a word) which would
    also let large amounts of water into the boat.
    
    Ed_who_wants_to_be_grounded_but_isn't_sure_where_to_do_it!!!

RE:.16 by CASV01::THOMAS_E "short!!"

> Dumb question #47
> If the standing rigging is grounded to the keel (external lead),  what 
> are the chances that if you are struck by lightning a large hole in the 
> plastic will be burned around the keelboat {keelbolt}? 

First,  the keel is the best place to ground to,  as it has a large surface
area to minimize the resistance to the water.  Remember V=IR?  A smaller
voltage on the grounding system helps to prevent arcs from the grounding
system to anything else (like you).  Unless you have something with a similar
area, you should use the keel.  Now, power is I*I*R.  Any place you have
resistance will get hot, and anything that gets hot gets more resistive,
so the best connection to the keel that can be made, should be made.  I
would NOT connect the lightning ground to ALL the keel bolts for the reasons
you state.  However,  do remember that however hot those bolts get, that
as soon as water gets to them they will be rapidly cooled, so there will
not be a huge hole burnt out around them.  If you are _real_ paranoid,  keep 
just enough water in the bilge to cover the keel bolts...

Production boats are often grounded through the motor.  This is at best
second best,  as the area of the prop and shaft is smaller than the keel,  
and the current will weld the shaft to the motor bearings.  They also use 
fairly small wire,  what ever is used for ground return from masthead lights 
is also (by default) the lightning ground.  I would be suprised if it was 
larger than #16.  This wire might melt and burn small holes in the boat.
Or worse still, fuse and then arc through the bottom or side , and make a 
HUGE hole in the boat.

A "standard sized" lightning strike is about 10,000 Amps for several 
milliseconds total (usually several pulses).  #12 wire to the keel should 
protect against such a strike with no damage except to electronics and
peace_of_mind.  I do agree that a "super bolt" sized strike (seen several 
times a year somewhere in the world) can not be protected against by any 
reasonable system.  A "super bolt" has currents exceeding 1,000,000 Amps,  
and has a peak brightness as large a small A-bomb.  Lightning has a _lot_ 
of variabliity.  All you can really do is increase your odds...

For EE types, let's do a real _rough_ calculation:

R_bolt=.1 ohm I=10,000 T=2mS

Energy=.1*10,000*10,000*.002=20,000 J=4,000 cal

If M=bolt=.25Kg (it is a big hunk of iron, but is this too large?)

J/g=16, and I think that Iron takes 1/4 as much heat per gram as water to
warm one degree,  so the bolt will heat up about 60 degrees C.  Not too bad.

Phil

re -.1:

I recall reading somewhere that wire no smaller than #8 (the bigger the 
gauge number, the smaller the wire) be used for lightning grounds. All 
connections should be mechanically strong as well as soldered. Grounding 
to a keelbolt only works with external metal keels. Otherwise, some 
other metal with a large area (1 sq foot minimum) should be used as the 
ground. (A propeller and shaft is probably about minimal.)

    Get off the propeller shaft kick.  Lightning doesn't like to hang
    sharp turns or any turns for that matter.  Regulations governing
    lightning protection for vessels carrying passengers for hire exclude
    the prop shaft for this reason.  The regs do suggest the use of
    a Dynaplate of at least 8 sq.ft. area (I believe).  I'll check on
    regs and reply with exact data.

RE:.18 by MSCSSE::BERENS "Alan Berens"

> I recall reading somewhere that wire no smaller than #8 (the bigger the 
> gauge number, the smaller the wire) be used for lightning grounds. 

Opps.  I was stating what should survive an average lightning strike, NOT 
what is recomended.  I also remember #8 as the recomended size.  The bigger
wire (smaller gauge) the better.


Phil

    Having a normal production type boat (Hunter 25.5), I wondered about
    the grounding etc after spending a evening last summer watching
    the lightning bolts around the harbor while sitting inside the boat.
    I called the Hunter factory and was told that the mast, etc was
    grounded to the keel bolts and was adequate for grounding a lightning
    strike.
    
    Since I, like most folks, paint the keel with two or so coats of
    bottom paint, have I hindered or enhanced the grounding capability
    of the boat?  Should I consider a Dynaplate?

Copper-based bottom paints should be quite conductive (especially
saturated with sea water). In any case, the paint film isn't very thick. 
If you really want to worry, it has been suggested that the heat of a 
lightning bolt dissipating in a Dynaplate could cause the water in the 
pores of the Dynaplate to boil, thus blowing the Dynaplate apart (and 
possibly holing your hull). No known cases of this happening, however. 
Practical Sailor suggests that using the keel as a ground is the better 
idea (again, assuming an external metal keel).

    I'm surprised I haven't seen reference to the flat, braided, copper
    wire commonly available at marine supply stores expressly for this
    purpose.  We have one of these wires bolted to the mast and then
    attached to the keel bolts with an extra nut on top of the nut that
    holds the keel on.  This wire is huge, certainly bigger than #8
    guage.
    
    Even with this grounding we are concerned that all electronics would
    be blown out in the event of a strike.  That would be a considerable
    loss for us.  We started disconnecting the loran, Ockams, VHF etc
    when not onboard, but besides being a pain in the butt we were told
    it really would do little good in the unlucky event of a hit.  I
    don't know what is right.  Any ideas?
    
    Dave

	Would it be worth putting on 2 Dynaplates? One aft of the keel
for the LORAN , and one forward of the keel for the mast for lightning
protection?  I suppose the halyard could also be grounded to the 
forward one also.

	Dave

re -.1
>  I suppose the halyard could also be grounded to the 
                 ^^^^^^^

	That should be shrouds.


	Dave

    Two Dynaplates are recommended...one for lightning ground and the
    other for the electronics and power bonding.  This is assuming that
    the ballast is internal.  

    
    
    My 32' Ketch "North Wind" is moored at the Ipswich Bay Yacht Club
    in an area that the club 'blue bloods' refer to as the "Annex".
    This is the eastern most part of the mooring field and only 100
    yds. from Plum Island.  I'm very familiar with the spot where you
    took shelter on the power boats.  Fortunately, I was not on board
    during the storm that Sunday.  
    
    As an update to your report....5 IBYC boats were struck that day!!
    Damage ranged from a completely destroyed VHF antenna to frayed
    nerves.  No hull damage has been reported.  One Windex is MIA.
    
    Talk around the Clubhouse has centered on the incredible frequency
    of the strikes.  Is it possible that this frequency lessened the
    power of these stikes??  (Many small ones vs. few big ones)
    
    I returned to North Wind after the storm and was pleased to note
    no damage, but, my Loran took an inordinate amount of time to
    figure out where it was!!!  I think it would have preferred being
    with me at the bar!

Thanks for the update.  I wanted to contact someone at the club to find
out what happend.  Five boats struck.  Must be some kind of record.....
but glad there wasn't more serious personal/property damage.

Definitely a candidate for "The Scariest Half Hour of Your Life Contest".

By the way, I've been considering joining your club.  Can we talk about
it sometime.

thnx

    
    
    I'd be happy to talk to you about IBYC.  Are you up the Parker River
    at Fernald's, and, if so, is their any meat left on your bones after
    those trips through bug alley?
    
    You can reach me at DTN 264-6993, or stop by the North Wind if you
    see the Ensign flying.  I'd be happy to give you a tour of the
    facility.
    
    Bob

RE: .9   "...the mast (metal I presume) would have a lot more current
          capability than the shouds."  And there by suggesting a mast-to- 
          chain connection instead of shroud-to-chain.

I've heard that the shrouds on all but the smallest boat should be large 
enough to carry most strikes quite harmlessly, and perhaps more to the 
point, I'd certainly opt for the more direct (shorter) path from masthead 
to ground that a shroud offers.

Of course, with a through-stepped mast, first choice is grounding to the
keel or perhaps centerboard hingebolt.


RE: .?    I used to disconnect my electronics -- antenna, power, ground -- 
and never lost anything when that was done.  As mentioned in .1, I lost 
everything once when I didn't do that, and lost the Loran once when the 
boat was left unattended; from the internal burns, we presume some little 
lightning spike nailed it.

J.

    
    The power squadron recommends using #8 jumper cables attached to
    a metal plate with 2 square feet of area, or at least that's what
    was told to me by one of their instructors.
    
    I have one of those fold-up radar reflectors that could provide
    the required surface area when opened in one direction (opening
    in both directions would turn it into a sea anchor & it'd pull
    away from the cables)
    
    My guess is that the preferred approach would be to keep the current
    path as far outboard as possible; attach the cables to the shrouds
    and then attach the other end to the radar reflector.
    
       - jim
    

    At the Newport show there was a vendor selling lightning rods. 
    They had a video running that explained the theory behind their
    product.  The theory goes something like this....
    
    A rod with the correct tip geometry (in this case maybe a 30 degree
    cone, but just a guess) will NOT take a lightning hit.  Rather,
    the rod serves as a point to bleed off accumulated charge thereby
    reducing the potential difference between your boat and the offending
    cloud.  If the charge difference is reduced... no strike.  In
    electrical storms the manufacturer claims that you can actually
    see the rod glowing as it ionizes the air around it.
    
    The people in the booth told me that years ago (when all boats used
    wooden masts) everyone had a lightning rod on their mast.  When
    aluminum masts became the rage it was simply assumed that the metallic
    mast would perform as a lightning rod and lightning rods went away.
    The problem with this was that everyone neglected the fact that
    aluminum masts are decidedly blunt.  Thus they allow their charge
    to build until......Zaaaaaap...... a destructive hit takes place.
    
    Now I'm a long time out of school but this had a very familiar ring
    of truth to it.  I would have bought one of their rods but
    at $25.00 it seemed a bit steep.  It was nothing more than 3/8"
    anodized aluminum with a pointed tip that was 'precision ground
    to a precise angle' (angle was unstated).
    
    Does anyone else in this conference know:
    
    	A. anything about this theory?
    
    	B. what the angle should be (if the theory is true)?
    
    	C. more about lightning science :^?
    

RE: Lightning rods at Newport, 

>>> A rod with the correct tip geometry (in this case maybe a 30 degree
>>> cone, but just a guess) will NOT take a lightning hit.  

Coupla' points:

1)  Maybe it would significantly reduce the chances of a hit, but it's
    hard to believe that anything will gain you 100% avoidance.  The speed 
    with which potentials build up locally (as they rapidly move across
    the earth's surface in random patterns) sometimes can mean that
    there's more charge to discharge than there is time to discharge it,
    before a strike does the job all in a bang. 

2)  In the "If-they're-so-smart-how-come-they-ain't-rich?" category, if
    there was a known fail-safe solution to some problem that's been
    around as long as lightning, doesn't it seem that a) someone would 
    have stumbled across it by now, and b) we might have heard about it 
    before now?   (I'm not trying to be particularly cynical; it just 
    seems like a reasonable question.) 

Curious:  Did the purveyor of these items also sell or recommend ground 
(water) connections, too?  

J.  

    They recommended attachment to your boats bonding system or if you
    don't have one they were selling dynaplates with jumper cable type
    of connection which you could throw overboard (after clamping an
    end to a shroud).
    
    I didn't mean to imply that they were guaranteeing anything like
    100% protection.  No sane person could believe 100% protection from
    anything.  The only thing being offered was MORE protection than
    if you do nothing.
    
    The grain of truth in what they are saying though is that there
    is a popular misconception about how a lightning rod (or grounded
    mast) works.  The intuitive approach is that the rod (mast) takes
    the hit thereby protecting everything in its 'cone of protection'.
    The reality is that the objective is to not take a hit in the first
    place.  And the theory behind thinking you can get away with this
    thinking is that little pointy objects allow charge to bleed safely
    off before enough potential difference is present to cause an arc
    (lightning).
    
    As in all things there are no guarantees.  It is possible (though
    hopefully not probable) that charge could accumulate faster than
    the rod can bleed it off to the atmosphere.  Here is where a well
    maintained ground system comes in.  The corroded, falling apart,
    or inadequate grounding system won't be able to handle the current 
    density of a well maintained one so the charge would build faster
    and the odds would slide accordingly.
    
    This might be a little fuzzy but my recollection of this theory
    is that charge and voltage are related by the area of the surface that
    the charge is on.  So the units of charge are in volts per square
    meter.  The square meters in a typical masthead are enormous when
    compared to a pointed rod thus the unprotected mast head can reach
    a much higher voltage than the rod can for equal amounts of charge.
    
    Now lightning is nothing more than a very large voltage arc.  The
    mechanism that causes the voltage buildup is charge which is flowing
    on the surface following an opposite charge in the moving cloud above
    it.  When the charge is allowed to accumulate on something close
    enough to the cloud and large enough (like a masthead) to carry
    significant charge on its surface, you will get enough potential
    difference (voltage) to cause an arc. 
    
    At least I think that's the way it goes.  Sure could use some
    confirmation though from someone with more hard facts :^) 

    One more point I didn't answer......  The opinions in .32 are mostly
    the manufacturers.  The opinions in .34 are mostly mine (copped
    from numerous sources).   I think this manufacturer is NOT selling
    snake oil (at least not entirely).  There is sound theory behind
    what they base their system on.  If they are into snake oil at all
    it is in the proclamation that there rod is blessed with magic powers
    and secret angles etc.
    
    I think it is only necessary to ensure that the highest point of
    your boat is VERY SMALL (preferably pointed).  However I do reserve
    the right to be entirely wrong and would like to here from more
    folks out there.
    
    The reason this knowledge has fallen from grace (my theory) is that
    most builders aren't into theory of electricity and it is really
    hard to sell something that is so darned simple when you don't
    understand it to begin with.  Selling these things to most sailors
    is like trying to sell tomato stakes to a farmer.
    
    Besides (no flames please) this is not the only item of old knowledge
    that has fallen by the nautical seaside in pursuit of speed and
    dollars in the current plastic boat market.
    

    Not a scientific observation but an observation none the less.
    
    I have a wood hull and mast. typical stainless rigging for a 34'
    Alden.
    
    Last summer while riding at the mooring, I had been working on
    my VHF radio. I had left the antenna disconnected near the mast.
    About a 3 ft. section of antenna comes out of the mast and was
    dangling from just under the overhead. Just aft of the mast is
    a 6 foot iron rod that ties the mast partners to the mast step.
    A lot of moisture on the underside of the mast step. The VHF
    antenna sits atop my mast above all other rigging. None of
    the rigging is grounded in any real way, just through whatever
    moisture is present in the wood.
    
    We sleep in a full width berth just forward of the mast.
    One early morning, round 2:00 AM, a thunderstorm began to
    sweep across the sky. As I lay in the bunk I could hear this
    "snap!"  pause  "snap!"  pause ...... and on........
    
    I finally dragged myself out to get hatches closed before the
    rain hit. In the dark, about a foot from my head, I was startled
    by a flash!!!!  Every time the antenna cable would swing near
    the iron rod, an arc was being drawn!!!! from the connector to the
    rod!!!  I reconnected that might quick you may be sure!!!!!!!!!
    The arc was probably an inch or so in length........
    
    Don,  for whatever its worth

    Did you reconnect to the VHF or to the iron tie rod?  It seems that
    the antenna was acting like the lightning rod described in .32.
    Every time it touched the iron bar, the antenna became grounded
    and dissipated the charge accumulating in the water.  Wouldn't one
    ordinarilly disconnect a VHF from its antenna during an electrical
    storm?

    I was on dry surface myself. I grasped the dangling coax in a rolled
    up towell and thurst into the female end which was fixed to the
    cabin overhead. There was an additional 8 or 9 feet of coax from
    this point to where the VHF was mounted. I considered two aspects
    before I did this. I knew the iron tie rod was not a good low
    resistance ground because the base of it under the mast step
    was still several inches away from the true bilge surface, which
    in my boat, except when sailing, can actually be somewhat dusty.
    So it was only the moisture distributed through wood surfaces.
    
    The VHF on the other hand, was well grounded through the wiring
    system to the engine to the shaft to the prop to the zinc to
    the ankle bone.
    
    Just another aside..
    
    I held a 1st class radiotel license some years back. I worked at
    WHIO in Dayton, Ohio. We had three self supporting towers which
    I switched at night for dirictional pattern. These towers, maybe
    150 ft high each were mounted on good sized insulators. The
    cement base supporting the towers was surrounded by a copper
    mesh burried in the ground. Across each insulator was a pair
    of rigid wires. One was attached by cable to the ground mesh,
    the other was fixed to the metal leg of the tower. They were
    close to each other in a sharp curve, perhaps an inch apart
    near the base and the curve cause them to separate even more
    in a smother curve. The object was tha a lightning hit would
    jump the gap at the sharper near end and then move out and as
    the curve separated, the stored current would have dissipated
    over time as the arc moved out and eventualy the voltage
    would not be high enough to keep an ionized path between the
    wires.
    
    Many a night a I sat in that station watching a lot of strange
    glows and bangs etc. from direct hits. The antennas were
    center fed incidentaly. Instead of coax, there was an open feed
    surrounded by 4 ground planes perhaps 3 inches away.
    We would get knocked off the air, the transmitter would restore
    itself and I would usually have to retune the lines!!
    
    The reason I mentioned this was to inform you that your VHF is
    designed to ignore lightning shock except under the most extreme
    situation or bad ground in the set itself.
    
    Your antenna is constantly building up high voltages just sitting
    at the mooring with a good stiff breeze blowing!!! You don't need
    a storm in the area!
    
    I can tell you this from experience. Part of my duties at the
    station included routine maintenance and inspection of all the
    facilities. Since the system was powered up till 1:00 AM
    each morning, the only time you could safely check the antennas
    was when power wasd off. It was a 15 KW station as I recall, and
    that is a lot of RF, especially at the base of a center fed 
    antenna. The first night I went out to check the antennas was
    a shocking experience!!!! I shut down power, had grounded out
    everything in  the transmitter with a grounding rod. In fact I
    had been working in the final of the transmitter so I knew there
    was no residual power hanging around when I went out to
    the antenna field. Well, standing on the mat, feet damp from
    dewey grass, I reached up to grab the upper horn of the device
    mentioned above. It was a clear, moonlight night, maybe 10 to
    15 knot wind. Well the bang I got cause me to do a one and a
    half gainer and I ended up on my back. I made some observations
    with a grounding rod, and in the dark, at most any time, you
    could see an ARC !!!
    
    Meanwhile, Captain Andy and Don Winslow continued there trek
    to the cave where the,.....Oh, sorry, got carried away..
    
    Don

	A couple of points from passed on wisdom of my elders....

	1) PUT A LIGHTING TAP AND SEPERATE GROUND ON ALL RADIO ANTENNA
	   COAX LEADS!!!!! There is a device that looks like a PL259
	   coax plug/jack with a screw on the side, ground the screw
	   to a REAL ground system, seperate from the electrical system!

		I wish I had a buck for every CB or ham rig I've seen
		fried because the owner didn't put in a direct ground
		strap on the end of the antenna lead. In 10 years of
		playing with radio transceivers I've never seen one that
		got zapped if all the leads were grounded, but I've seen
		antennas that looked like they were used as a light bulb!
		Antennas are cheaper to replace than a radio (or an operator)!

	2) Ground the mast and antenna seperate from the coax, lightning
	   is a (usually) surface traveler, and will take (usually) the path 
	   of least resistance to ground. This mast grounding also provides
	   a discharge route, which will provide a "cone" of protection
	   usually equal in diameter to half the height of the mast. 

	3) Old sailor trick - carry a battery jumper cable (large heavy kind
	   like used for trucks and tractors) and a large square copper
	   plate with a big bolt through one corner. On approach of a 
	   thunderhead, clip one end of cable to mast base or shroud plate
	   clip other end to bolt in plate, put plate in water. 

	4) And the one guiding rule (usually YELLED at me) "get inside the 
	   @#$% building (or cabin in this case) dummy!" stay away from power 
	   equip. (which should be powered off and supply cables unplugged),
	   and away from any metal shafts (ie mast base, chain plates, 
	   through hulls (take the relief BEFORE THE STORM HITS! ;-) )....
	   etc.

		most of the above was advice from Radio hams and experienced
		radio operators, but so far seems to hold true..(insert
	 	sound of fist knocking wood fiber...)

	Funny story #2....

	While camping in a 25' trailer (land yacht) my mother once had
	to sit on pillows for a week because she decided to releave herself
	during a thunder storm. Have you ever seen an elderly lady, partially 
	undressed, LEAP out of the head while yelling louder than a nearby 
	thunderclap? 

		Greg

    
    re: point 3
    
        attach it to the bottom of the shroud, not the mast step, to
    keep the ground path as far outboard as possible.  don't expect
    lightening to make any sharp turns.
    

RE:.40 by ECADSR::FINNERTY and others

> attach it to the bottom of the shroud, not the mast step, to keep the 
> ground path as far outboard as possible.  don't expect lightening to make 
> any sharp turns.

No.  If you can ground ONE AND ONLY ONE point,  ground the mast step.  FAR 
BETTER is to ground the mast and all standing rigging.

Lightning will indeed "try to shorten" it's path by jumping at any sharp 
turns.  Lightning will also "try to shorten" it's path by jumping at the end
of any piece of metal,  such as the mast step or the bottom of a stay.

The mast will have much lower resistance and inductance than a shroud because 
it is much larger in diameter.  So grounding it will build up a lower voltage,  
reducing the chance of a jump elsewere.


Phil

    I'm launching a 1988 Catalina 22 in Lake Winnepeseaukee this week. The
    boat has a deck-stepped mast and wing keel. I noticed a little blurb in
    the owner's manual that concerns me. To paraphrase:

         "this boat is NOT equipped with a lightening rod since
         (a) there are many different kinds of devices available
         and this should be at the owner's discretion, (b) many
         people assume that a lightening rod will protect them
         when it might not, and (c) on many boats, lightening rod
         wiring is woefully inadequate or NOT INSPECTED allowing
         the owner to have false sense of security... " 

    Whaaat? I agree with (c) that on many boats the wiring is often
    corroded where it meets the keel bolts - still, this proviso seems like
    a legal hedge to avoid installing the equipment in the first place
    (since so many Catalina 22s have centerboards).
    
    What is the sailing notes community's feeling regarding lightening
    rods?  Maybe I'm nervous for a reason: I once sailing on a boat in
    Florida owned by a man who bought it from the estate of a man struck by
    lightening on it. 
    
    Given that this boat has a deck-stepped mast, how would a lightening
    rod be installed?
    
    Bob