[Rhodes22-list] lightning protection

Todd Tavares sprocket80@mail.com
Tue, 19 Nov 2002 15:51:05 -0500


   Thanks Bill,

          My only point was that lightning would find the shortest and
   probably straightest path to the water.  My terminology wasn't
   correct.  I thought you were implying that because of the construction
   of the R22 that we were less likely to be hit because of the distance
   between the mast and water, and materials in the boat.

        I have never been on a boat that has been hit by lightening, but
   have seen many ground strikes close up.  My only hope would be to
   survive (including making it back or being rescued from a partially
   submerged boat).  Boat and electronics can be replaced.

   Thanks for the posts.

   Todd

   ----- Original Message -----
   From: "Bill Effros"
   Date: Tue, 19 Nov 2002 12:52:34 -0500
   To: "The Rhodes 22 mail list"
   Subject: Re: [Rhodes22-list] lightning protection
   > Todd,
   >
   > The image of lightning "jumping gaps" is somewhat misleading. Rather
   than
   > rehash everything that has been said previously, let me post a few
   of the
   > responses that meant the most to me from previous discussions:
   >
   > Here is how Razz put it:
   >
   > Rummy,
   >
   > If your electrical thrills are the result of electrostatic charge
   > building up, grounding the rigging won't eliminate the problem as it
   > is already acting as ground. The charge most likely is building up
   on
   > your butt as you slide across the seats. Much like crossing a wool
   > carpet and getting shocked when you touch the door knob.
   >
   > Proper grounding for lightning protection involves installing a
   > lightning rod at the top of the mast and grounding that to a metal
   > surface of significant area below the water. Boats with exposed lead
   > or iron keels can use the keel as a grounding surface. Reuel Parker
   > uses a
   > 2'x2' copper plate laminated into the bottom of his centerboard boat
   > designs. The cable connecting the lightning rod to the ground plate
   > should be very heavy guage and insulated
   > from the mast and rigging. No other metal on the boat, nor any part
   of
   > your electrical system should be grounded to this lightning
   protection
   > system. The theory is to provide a
   > clear alternate path to ground for any potential charge buildup.
   This
   > does not attract lightning as it serves to dissipate most charges
   > before they build up to dangerous levels. If a strike occurs, the
   > lightning ground provides a cone of protection for the boat and its
   > occupants equal to the height of the mast. So as long as you aren't
   > touching metal you are not likely to be injured. One of Parker's 50'
   > centerboard schooners took a direct hit that blew a hole in the hull
   > where his ground plate was attached, but no one on board was injured
   > and the boat did not sink as his designs have water tight bulkheads
   > between compartments.
   >
   > Very few lightning strikes actually occur on inland lakes or on any
   > body of water where land is nearby. Despite the fact that the
   earth's
   > surface is 2/3rds water, 94% of all cloud to earth lightning strikes
   > occur on land. This is due to the fact that large bodies of water
   > usually carry a positive ionic charge which is the same polarity as
   > the positive charge build up in thunderstorms and therefore do not
   > represent a good ground potential compared to the negative charge of
   > land surfaces. Earth ground really does mean solid ground. A boat is
   > more likely to be struck sitting in the marina or anchored near land
   > than out sailing and then only if it is the tallest object around.
   >
   > RAZZ
   >
   >
   > Here is what Fred Lange had to say:
   >
   > West Marine will send you a free packet of articles about lightning.
   >
   > Included in the material are some interesting statistical studies
   about
   > how lightning damages boats. In summary, sailboats are more likely
   to
   > be hit than power boats. Boats near shore or docked are more likely
   to
   > be hit than boats on the open water. Boats on salt water are more
   > likely to be hit than boats on fresh water.
   >
   > The physics of it is that if your boat is in a lower voltage area
   > between sky and earth surface, the likelihood of getting struck is
   > higher.
   >
   > Boats with lightning protection on open salt water suffer only
   slightly
   > less damage from lightning strikes than boats without lightning
   > protection, but the people aboard fare better. Boats on open fresh
   > water pretty much always get sunk when they are hit, but here again
   > lightning protection helps the people.
   >
   > I had a sailboat boat hit at the dock in brackish water. I know
   because
   > I had an anchor chain shackled to a stay and the fiberglass next to
   the
   > chain was charred. No other damage.
   >
   > Since I'm mainly a fresh water sailor, I have extended my experience
   > with the chain to try and protect the people in the boat if I get
   hit.
   > I have 5 battery cables for clamping to the two back stays, the fore
   > stay and to the port and starboard sides of the mast. I hope the
   cables
   > with their frayed ends will ground most of the strike into the water
   > leaving the crew untouched. However, I expect there is till the
   > likelihood that much of the strike will jump from the base of the
   mast,
   > though the cabin and out of the bottom of the hull, filling the
   Rhodes
   > with water.
   >
   > Fred
   >
   > Here is Roger's 2 cents worth:
   >
   > Thena,
   >
   > Yes, the Beneteau 40 footer had one of the tallest masts in the
   marina that
   > night. But, it wasn't the biggest sailboat & there were other boats
   around
   > it that had comparably tall masts. Mast height is an important
   factor; but,
   > predicting a lightening strike isn't that simple. From what I've
   read, up
   > to about 50 feet of mast height, an ungrounded mast has about the
   same
   > probability of being hit by lightening as the water in the same
   area. It
   > just depends if the boat happens to be unlucky enough to inside the
   area
   > where the charge separation is building up. I subscribe to the
   principle of
   > purposely NOT grounding the mast. I've been out in a number of
   > thunderstorms in my sailing career & I haven't been hit yet. Of
   course, I
   > may get clobbered tomorrow!
   >
   > Roger Pihlaja
   > S/V Dynamic Equilibrium
   >
   > Here is Michael:
   >
   > I sail on salt water, it's my view unless I am ready to do the full
   job and
   > the
   > best job I would be asking for trouble that a jury rig system would
   be able
   > to
   > handle. I rather not ask for trouble then wimp out went it comes,
   but like
   > everything else in life "You pay your money and take your chances"
   >
   > MJM
   >
   > Another dime's worth from Roger:
   >
   > Everybody seems to be assuming lightening is a bigger hazard to
   sailboats on
   > salt water than on fresh water. I suppose this is because it's well
   known
   > that salt water is a better conductor of electricity than fresh
   water.
   >
   > Dow Chemical Company, where I work, is the world's largest
   manufacturer of
   > chlorine & caustic soda. Chlorine & caustic soda are made by sending
   > electricity thru a brine solution inside of a specially designed
   cell which
   > is designed to collect the two products. The process is carried out
   on a
   > huge scale because chlorine & caustic soda are used in enormous
   quantities
   > in the industrial world. I know a little bit about the behavior of
   water &
   > salt water when carrying very high electrical currents. Basically,
   at the
   > kind of voltage & current we are talking about in a lightening bolt,
   both
   > fresh water & salt water behave like very poor conductors of
   electricity. I
   > would expect the electrical resistance in either liquid to dissipate
   the
   > electrical energy to heat within a few meters of the impact point.
   Since we
   > are talking about a huge amount of energy in a very short period of
   time,
   > this heat would cause the water to flash into steam, maybe even
   superheated
   > steam! I wonder if a lot of the damaging effects of a lightening
   strike
   > aren't really blast & thermal effects from a "steam explosion" in
   the water
   > under the boat. Of course, the hole in the hull the lightening had
   to make
   > to get to the water isn't much fun either! In any case, since salt
   water is
   > a little more electrically conductive than fresh water, the zone of
   heating
   > should extend a little farther away from the point of impact than in
   fresh
   > water. This would spread the energy out over a bigger volume
   resulting in a
   > less violent event. But, this is probably splitting hairs, I doubt
   there is
   > very much difference between a lightening strike on fresh vs. salt
   water.
   >
   > Roger Pihlaja
   > S/V Dynamic Equilibrium
   >
   > Fred again:
   >
   > Roger,
   >
   > It is not splitting hairs when you said that salt water will "spread
   the
   > energy out over a bigger volume resulting in a less violent event."
   > Lightning strikes to boats on salt water tend to cause less damage
   and
   > injury. While less frequent, strikes to boats on fresh water are
   much
   > more damaging.
   >
   >
   > Regards,
   >
   > Fred
   >
   > Tommy Thompson:
   >
   > His point about not making it a target is "basically" sound,
   particularly
   > when
   > one considers all the other mechanics that are at work, rain etc....
   Like a
   > car in the rain, it is grounded, it is a question of how good the
   ground is,
   > and hence "bonding" comes into play.
   >
   > The advantage of any grounding scheme design is to "encourage" the
   discharge
   > path away from electronics and/or people. Which is easy to conceive
   on
   > land. For example, if you use a grounded pole or wire overhead it
   creates
   > a120 degree umbrella of protection from the top looking down.
   >
   > On a boat however, especially a small boat, you are still close the
   > discharge
   > path itself. There is always that inherent feeling when you have all
   the
   > proper "bonding" done and cabling in place that now you are the best
   source
   > for
   > creating "trailers". Particularly for the surrounding area in your
   > immediate
   > vicinity. The advantage is only to keep the strike as far away from
   your
   > crew
   > as possible. On a small boat, we are talking some feet.
   >
   > Seems more like a coin toss for personal preferences as some
   argument can be
   > made either way, considering "added value" to a small boat.
   >
   > Tommy
   >
   > Ron Lipton:
   >
   > This is a good reference:
   >
   > http://www.thomson.ece.ufl.edu/lightning/
   >
   > The bottom line is that there is no consensus on whether grounding
   the
   > boat
   > increases the probability of a strike. Lightning protection is
   intended
   > to divert
   > the current of the strike through a good conductor rather than
   through
   > the hull
   > of your boat (or through you) and not to lessen the probability of a
   > strike. Due
   > to the large currents involved it is difficult to do a proper job
   > without substantial
   > conductors.
   >
   > According to Thomson's study the probability of a strike can
   > be approximated by drawing an "attractive area" cone with an apex
   angle
   > of
   > 132 degrees at the top of the mast. (This is an rough estimate based
   on
   > lighting
   > strike data and not a calculated angle). This gives the effective
   area
   > of the
   > Rhodes 22 for lighting strike purposes as about 10,000 square feet.
   So
   > it is roughly equal to the probability of lightning striking a house
   or
   > yard.
   >
   > Given the difficulty in protection and the low probability of a
   strike I
   > would not
   > do anything unless I expect to be traveling in a stormy area. I
   would
   > stay away
   > from metal parts of the boat if caught in a sudden storm and take
   > comfort in
   > the foam flotation in the Rhodes.
   >
   > Ron Lipton
   >
   > And the last word from Rummy:
   >
   > There have been many discussions on this site about lightning. The
   final
   > conclusion agreed to by the group is that it is a personal choice
   whether or
   > not to ground your mast and shrouds. I don't know of a any Rhodes
   22's that
   > are grounded with a plate or whatever. Salt water conducts
   electricity a lot
   > better than fresh water.
   >
   > My personal choice was not to make my boat a target. It has no
   grounding
   > straps. It has been moored on a bouy for many years and tied up at a
   dock
   > lately without being a target. By choice, whenever lightning becomes
   an
   > issue, I leave the boat and head home.
   >
   > Rummy
   >
   >
   >
   > I'm done with this topic for now.
   >
   > Bill Effros
   >
   >
   > ----- Original Message -----
   > From: "Todd Tavares"
   > To:
   > Sent: Tuesday, November 19, 2002 12:13 PM
   > Subject: Re: [Rhodes22-list] lightning protection
   >
   >
   > Bill,
   >
   > I am by no means an expert, and even the "experts" disagree but, it
   > seems to me, that if there is a big enough difference of potential
   for
   > lightning to "jump the gap" from the clouds to the water, then the 3
   to 4
   > feet of air and fiberglass in your R22 would do little to stop
   lightning
   > from shooting a hole right through your boat........or that theory.
   IMHO
   >
   > Todd
   >
   >
   > ----- Original Message -----
   > From: "Bill Effros"
   > Date: Tue, 19 Nov 2002 10:21:28 -0500
   > To: "The Rhodes 22 mail list"
   > Subject: Re: [Rhodes22-list] lightning protection
   >
   >
   > > Brad,
   > >
   > > We have this discussion roughly once a year. When all is said and
   done,
   > its
   > > clear that this is a poorly understood phenomenon. People selling
   things
   > > will scare the shit out of you with horror stories. They provide
   > "experts"
   > > who you have never heard of before, propounding disproven theories
   as
   > facts.
   > >
   > > None of the theories relate directly to the construction of our
   boats.
   > Most
   > > of the strikes occur on sailboats where there is a direct
   electrical path
   > > from the top of the mast to the bottom of the keel, frying
   electrical
   > > circuits as they go. Our masts are, what, 3-4 feet from the water?
   They
   > > are mounted on non-conducting fiberglass, with wooden support, and
   a lot
   > of
   > > air between the bottom of the mast and the water.
   > >
   > > Now the first thing you are told about lightning is to not touch
   the mast
   > > anytime you are concerned about it. But your approach would
   involve
   > running
   > > to find an excellent conductor, carrying it on the deck, attaching
   it to
   > the
   > > mast while the other end is still in your hand, and leading it
   overboard
   > in
   > > such it way that it does not foul. Every time I find myself in a
   > potential
   > > lightning situation I reaffirm the fact that I would not even
   consider
   > this
   > > approach at a time I was concerned that lightning might strike at
   any
   > > moment.
   > >
   > > We know that some lightning starts in the sky and goes down to
   earth while
   > > other lightning starts in the earth and goes to the sky. Our boats
   are
   > not
   > > susceptible to the earth to sky lightning because there is no
   direct path
   > > from the earth to our masts--unless we attach a conductor to the
   mast and
   > > drape it over the side and into the water.
   > >
   > > There is a school that suggests that these lightning protection
   devices
   > > generate more strikes on the boats they are supposed to protect.
   > >
   > > I don't know, but I do know that I have never heard of an R-22
   being
   > > structurally damaged by lightning. And I always go back to my main
   motto:
   > > "If it ain't broke, don't fix it."
   > >
   > > Bill Effros
   > >
   > > PS -- Sorry to hear about your headache. Maybe it was the fumes
   from your
   > > generator?
   > >
   > >
   > >
   > >
   > > ----- Original Message -----
   > > From: "brad haslett"
   > > To: "The Rhodes 22 mail list"
   > > Sent: Tuesday, November 19, 2002 9:38 AM
   > > Subject: Re: [Rhodes22-list] lightning protection
   > >
   > >
   > > Bill, several sources I've read indicate that is a
   > > mis-conception. The statistical data for boats at
   > > moorings don't indicate a higher mast being more
   > > likely to be struck than a lower one. Brad.
   > > --- Bill Effros wrote:
   > > > Sail or dock near a boat with a 30' mast.
   > > >
   > > > Bill Effros
   > > >
   > > >
   > > > ----- Original Message -----
   > > > From: "brad haslett"
   > > > To:
   > > > Sent: Tuesday, November 19, 2002 7:58 AM
   > > > Subject: [Rhodes22-list] lightning protection
   > > >
   > > >
   > > > This all got started while doing research on
   > > > installing a mast antennae. Several vendors lightly
   > > > addressed surge protection from lightning strikes to
   > > > the mast and I thought, "who cares about electronic
   > > > euqipment? I want the boat to survive!" Yesterday I
   > > > spent eight plus hours on the net researching the
   > > > issue and downloaded a 3" binders worth of material
   > > > including the R-22 site info. My conclusion is
   > > > this;
   > > > sailboats take more lightning strikes than one would
   > > > think, freshwater boats without grounding don't fare
   > > > well, and, protection is not that difficult. While
   > > > there are many different opinions and several "old
   > > > wives tales" the general concensus among the experts
   > > > is that having a protection system on board does not
   > > > make one more likely to be struck. All protection
   > > > systems pretty much do the same thing, they provide
   > > > a
   > > > path from the mast to the water. While at dock its
   > > > a
   > > > simple matter of attaching a #4 cable or flat
   > > > conductor to a 1' square or bigger conductor in the
   > > > water. The straighter the path and the fewer the
   > > > bends the better (lightning doesn't like to turn
   > > > corners). Under sail is a different story. No one
   > > > wants to sail with cables on the foredeck and plates
   > > > dangling in the water. Therefore, a portable and
   > > > quickly attachable system is needed (battery cables
   > > > get knocked off at the moment of strike). The
   > > > StrikeShield system is perfect but expensive. I am
   > > > presently researching a "homemade", ie, Home Depot
   > > > approach that will do the same thing for far less
   > > > money. Most boat manufacturers don't address the
   > > > issue, probably for liability reasons. Catalina
   > > > issues a bulliten from the ABYC on the subject and
   > > > basically tells you "you're on your own". Over the
   > > > past fifteen years I have been caught at least three
   > > > times in thunderstorms in powerboats and once in a
   > > > canoe. Now that my boat has a 26ft tall lightning
   > > > rod
   > > > I'd like to better my chances. Ideas?
   > > >
   > > > Brad Haslett
   > > > "CoraShen"
   > > >
   > > > __________________________________________________
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