[Rhodes22-list] Lightning 'Cone of Protection' Fw: Overhead and
underfoot metal
Brad Haslett
flybrad at gmail.com
Wed Aug 2 16:59:14 EDT 2006
Found this in the Nov 2002 thread of the archives. Everyone might want to
review those posts and see if there is anything new. Here's (was) my two
cents worth.
Brad
--------------
Roger,
It looks like theres still some life in this dead
horse so Im giving it one more kick.
Thanks for the input. The data you referred to have
been verified many times by several different sources
including a recent study by a Russian scientist
studying lightning strikes in Hong Kong. The problem
is that the data isnt 100% relevant to the sailboat
application. Those studies were done in industrial
and commercial settings where at the 25-foot level
there were many other targets as opposed to a solitary
tall structure. Plus, all of this data comes from land
based studies. As you say, when you increase the
height of a structure, its probability of being struck
increases substantially. However, if you did the
analysis on several square miles of densely placed
500-foot towers it would skew the data just as it does
in an industrial plant full of 25-foot structures.
That being said, strike probability clearly increases
geometrically with height. A Rhodes 22 in your
driveway with its mast up is no more likely to be
struck by lightning because of its mast height than
the two-story home next to it. When you park it in
the middle of an open body of water the odds change.
To quote Dr. Marcus O Durham, Associate Professor at
the University of Tulsa and director of the Power
Applications Research Center, The strike frequency of
lightning goes up with the square of the height above
average terrain. This makes isolated structures
particularly vulnerable..Sharp points increase the
likelihood of a strike. (vhf antenna, mast, etc. bh)
The high electric field below a charged cloud will
create ions in the neighborhood of sharp points.
These ions increase the air conductivity and
probability of a cloud discharge (strike). Which
brings me around to the original question; if you are
sleeping on your R22 in quiet cove and are awakened by
approaching thunder do you?
a) leave the cove for open water b) stay in the cove
and compete with the trees c) throw out your mast
grounding system or d) put in your cassette of
Dont Worry, Be Happy! and play it at a volume
greater than the thunder? One nice thing I have
discovered in all this research is that in Tennessee
Im number five on the risk list behind (in order)
Florida, North Carolina, Texas, and New York. New
York? Yep, didnt make it up.
Brad Haslett
CoraShen
On 8/2/06, Arthur H. Czerwonky <czerwonky at earthlink.net> wrote:
>
>
> FYI
>
> Art
>
> -----Forwarded Message-----
> From: Ewen Thomson
> Sent: Aug 2, 2006 2:31 PM
> To: "Arthur H. Czerwonk y"
> Subject: Overhead and underfoot metal
> < BR>Art,
> I promote the concept that the best way to NOT be the at tachment
> point for a lightning strike is to have metal overhead.
> This would make a sailboat with metal shrouds safer than one
> without, at le ast as far as a direct connection is concerned.
> Sidefla shes on the other hand depend more on metal between the
> mast and the water, such that unbonded metal
> in the hull increases the risk of a sideflash to a crew member.
> Regards,
> Ewen.
> [1]www.marinelight ning.com
> Arthur H. Czerwonky wrote:
>
> Ewen,
>
>
>
> Good point. I am interested if you have found any evidence or co
> mpelling theory that would promote the 'cone of protection' theme,
> either a s a result of being or not being grounded, said to be a
> result of the array of shrouds used on a sailboat.
>
>
>
> Some have felt that grounding, by creating a most direct path to the
> w ater, actually makes the mast a more likely location for lightning
> to strik e. Would you agree?
>
>
>
> Cheers,
>
> Art
>
> -----Original Message-----
> From: Ewen Thomson
> Sent: Aug 2, 2006 10:51 AM
> To: "Arthur H. Czerwonky"
> Subject: Re: Fw: Re: [Rhod es22-list] sailing and lightning (long
> reply)
> Art,
> Thank s. I'll follow the postings and see if my comments have
> made any diff erence. It was interesting (and educational!) to
> me to note tha t the only quote from my web pages was " lightning
> protection on these boat s also should be regarded as a last
> resort, with storm avoidance being the best defense". This is
> very misleading as it could be interpreted to mean that a
> lightning protection system is less important than e.g. buying a
> $800 GPS system so that the storms can be tracked! Needless to say
> I have rewritten this section to qualify the "best defense" as
> being imprac tical on a sailboat that ventures any distance or
> will be used for cruising .
> Please let me know if you think there is anything else I can do t
> o help in the education effort.
> Regards,
> Ewen.
> PS There is also an interesting discussion on this topic going on
> at the MacG regor message board at
> [2]http://list.sailnet.net/read/?forum =macgregor
> Arthur H. Czerwonky wrote:
>
> Ewen,
>
> I reposted when I was advised of the garble. I may do it again.<
> /DIV>
> Art
>
> -----Original Message-----
> From: Ewen Thomson
> Sent: Aug 1, 2006 2:56 PM
> To: "Arthur H . Czerwonky"
> Subject: Re: Fw: Re: [Rhode s22-list] sailing and lightning (long
> reply)
> Thanks Art.
> However, I just checked out the discussion and found that my post
> was this :
> Forwarded FYI. Art -----Forwarded Message----- From: Ewen Thom son
> Sent: Jul 30, 2006 1:12 PM To: "Arthur H. Czerwon Subject: Re: Fw:
> Re: [Rhodes22-list] saili reply) Dear Art, Thank you for fo Since
> it contains s o me to address all of th FACTS" mentioned
> below,&nbs - Being caught ou t in a sailboat during a lightning
> storm does not mean you are going to be struck. However, even
> this one comes with a disclaimer. Compar being in a m arina close
> to other boat masts, being caught out in a perhaps a factor est
> imate is Bo lightning damage to catamar brief explanation for this
> is that cata there is less protective effect from neighboring ma
> marinas. My best a ttempt at addressing the relevant issues a in
> my web pages at [3]www.marineli ghtning.com , that h updated very
> recently. But even here I realize tha t there is much information
> scattered over so many pages that it is difficu l t for the lay
> sailor to come to grips with the most important concepts, a nd
> opposed to, for example, much cheaper product that, if you bel
> prevent l ightning from striking in the first answer to this see
> [1][4]http://www.ma rinelightning.com/AirTerminals.htm . For
> another , Boat US have a photo of a seriously listing catamaran
> whose bristle brush is still intact Here is an overvi The home
> page [2]www.marinelightning.com summarizes our approa as having a
> foundation in peer-reviewed science, bei ng cons istent with
> observations of actual damage, and being considered by th
> Protection Associatio 780 (see pages 21-28 in [3][5]http://www.nfp
> a.org/Assets/Files/PDF/ROP/780-08-ROP.pdf ). Perhaps
> [4][6]http://www historical intro processes are de scribed and
> reaso key point here is that we attempt to protection system th at
> simulates that on a buildin multiple air terminals, down conductors
> on t he outside, and multip le grounding terminals around the
> perimeter. Note th at this is a very through the one-square-foot
> ground plate risk of sideflas hes. Products described on [5]
> include the Siedarc ( square foot grounding strip, and for a boat
> on a boat lift. Th than or comparable to those on sim ilar pr
> elsewhere. For example, a Siedarc (TM) electrode wit cable is $215
> compared with $419 for the single-electrode Str ikeshield model
> CSSB-15. Th e CSSB does come with a mast-mount c onnector, but
> otherwise the two are ve ry similar. Internal conn ections for the
> Siedarc can be made with inexpens ive heavy duty lugs. As you can
> tell from the above, the installation of a effective lightning
> protection system is not trivial, and every boat is a c ustom job.
> However, there are huge cost/benefits for a one design such as t
> he Rhodes 22 if the manufacturer is motivated system should be po
> boat. Thi s is where you difference. If you could con that you,
> the customer, would l ike to s boat then something is likely to
> happen. Once components have been designed for new builds,
> retrofits shoul possible at an affordable price. I would really
> li in this, it is inappro your message board. Howeve way tha t you
> feel is appropriate, an anything else I can do to . Best reg Ewen
> Tho mson. Arthur H. Czerwonky wrote: Dr. Thompson, We have a
> discussion in prog ress on lightning, and how skippers of the
> Rhodes 22 fleet could best provi de protection for crew, boat, and
> electronics in the event of a lightning a ccompanied storm
> underway. The below 'wisdom' is a poor substitute for your studied
> insights for sure, but does this approach hold any promise for eff
> ectiveness? The '35 foot conductor from mast head to the copper
> plate' woul d probably have to be 4 gauge. Does this solution make
> sense? Would appreci ate your suggestions.
> It looks as though a lot of lines were choppe d off, resulting in
> quite a mess. Also, in an earlier post I found an incorrect link
> to my furled sails interview. The correct link is&nbs p;
> [7]http://media.libsyn.com/media/noeld/furled sails-podcast-47.mp3
> The main point in my message was that impr ovements such as
> lightning protection should be the responsibility of the b uilder,
> and that your group could get this to happen with a concerted
> phone-in effort to General Boats ( 252-482-4372) to request that
> thi s feature be added.
> Regards,
> Ewen.
> Arthur H. Czerwonky wro te:
>
> Ewen,
>
> The URL is "[8]rho des22-list at rhodes22.org". The various topics get
> bounced around a bit, then fade away. One point, which seems to be
> somewhat consensus is that, like in an insulated automobile (rubber
> tires) the sailboat confi guration is such that the odds of a strike
> underway are quite low, and that the array of 9 stays supporting the
> mast creates a 'cone of protection'.&n bsp; If the sailboat is
> grounded to the water, the perception is that the o dds of attracting
> a strike are greater, since there is an easier path of tr avel via
> the mast/stays/conductor. Your input has been most helpful.< /FONT>
>
> Art
>
> -----Original Message-----
> From: Ewen Thomson
> Sent: Aug 1, 2006 12:16 PM
> To: "Arthur H. Czerwonky"
> Subject: Re: Fw: Re: [Rhod es22-list] sailing and lightning (long
> reply)
> Art,
> Thanks fo r forwarding to the board. What is the URL so that I
> can keep track o f the dialogue?
> Please see my comments below.
> Regards,
> Ewen.
> < BR>Arthur H. Czerwonky wrote:
>
> Ewen,
>
>
>
> I will forward your email into the board, which I agree is a more
> suit able way to broadcast. A quick, probably too simple question:
>
>
>
> According to the article attached to your bpage with the 23 min
> video, 8 gauge wire in many cases melted as a result of a direct
> hit. If an insulated 6 gauge copper
>
> 4 gauge is the recommended mini mum size but I use 2 gauge.
>
> conductor were bolted to the mast step (deck located step, traile
> rable) in a very secure manner,
>
> copper in contact with a n aluminum mast will corrode the aluminum
>
> welded to a 1' square copper plate, and suspended over the closest
> acc ess to the water at the side of the boat, would this provide some
> greater d egree of "insulation" or safety, or would it create a
> greater danger?& nbsp;
>
> If you could do this on both sides it would provid e effective
> grounding in salt water, although welding is likely to weaken t he
> cable connection at the joint. In fresh water additional gro
> unding conductors would still be needed, especially at forestay and
> backsta y. Plus large conducting fittings should be bonded to the
> mast to equ alize potentials over the whole boat. From a
> practical point of view, the plates are likely to flail around in
> the water and dent your hull, and any temporary system runs the
> risk of not being deployed and is a hazard t o the deployer.
> Also, if there are any other immersed metals (stainle ss, iron,
> aluminum) the copper is likely to cause corrosion problems (which
> is a problem for any immersed grounding conductor).
>
> Assuming the end of the conductor were carried to a point 1 or 2 feet
> above the mast top, would that be better than at the step?
>
> The mast is already aluminum which is a suitable lightning
> conductor, so that this would be redundant. It is a good idea
> to add an air t erminal at mast head if there are any masthead
> fittings that should be prot ected.
>
> Your response, and especially your help is greatly appreciated.&n bsp;
> Your research has to be quite interesting with so many variables
> to co nsider and to isolate.
>
> "Interesting" is an understatement ! The best solution is always
> a compromise amongst effectivenes s (lightning conductors all over
> the place), cost (fewer is better), aesthe tics (none is best),
> corrosion (no dissimilar metals in the water; if there are,
> either isolate or bond together and add zincs), etc., etc..
>
>
>
> Very best regards,
>
> Art Czerwonky
>
> -----Original Message-----
> From: Ewen Thomson
> Sent: Jul 30, 2006 1:12 PM
> To: "Arthur H. Czerwonky"
> Subject: Re: Fw: Re: [Rhod es22-list] sailing and lightning (long
> reply)
> Dear Art,
> Thank you for forwarding this lively and interesting discussion.
> Sinc e it contains so many points of view, it is impracticable
> for me to a ddress all of them. For example, of the four
> "INTERESTING FACTS" ment ioned below, I would agree with just one
> of them -
> Being caught out in a sailboat during a lightning storm does not mean you
> are going to be struck.
>
> However, even this one comes with a disclaimer. Compared with
> b eing in a marina close to other boat masts, being caught out in
> a thunderst orm increases your probability of being struck by
> perhaps a factor of five or ten. The empirical evidence for
> this estimate is Boat US ins urance statistics. Specifically,
> lightning damage to catamarans is tw ice that to monohulls. The
> brief explanation for this is that catamarans ar e wider and so
> there is less protective effect from neighboring masts in ma
> rinas.
> My best attempt at addressing the relevant issues are contained
> in my web pages at [9]www.marinelightning.com , that have
> been updated very recently. But even here I realize that there is so
> much information scattered over so many pages that it is
> difficult for the lay sailor to come to grips with the most
> important concepts, and why shou ld anyone believe what I have to
> say, as opposed to, for example, the brist le brush salesmen who
> have a much cheaper product that, if you believe them , may
> actually prevent lightning from striking in the first place?&nb
> sp; (For one answer to this see [10]http://www.marinelight
> ning.com/AirTerminals.htm . For another, Boat US have a photo of a
> seriously listing catamaran whose bristle brush is still intact
> at mast h ead following a lightning strike. )
> Here is an overview:
> The home page [11]www.marinelightning.com summarizes our approach,
> as ha ving a foundation in peer-reviewed science, being
> consistent wi th observations of actual damage, and being
> considered by the lightni ng protection committee of the National
> Fire Protection Association for inc lusion in the 2007 version of
> NFPA 780 (see pages 21-28 in [12]http://www.nfpa.org/Ass
> ets/Files/PDF/ROP/780-08-ROP.pdf ).
> Perhaps the most straightforward explanation is that on
> [13]http://www.marineli ghtning.com/science.htm . After a brief
> historical introduction, the relevant lightning discharge
> processes are described and reasonable sol utions are proposed. A
> key point here is that we attempt to build a m arine lightning
> protection system that simulates that on a building -
> with multiple air terminals, down conductors on the outside, and
> multiple ground ing terminals around the perimeter. Note that
> this is a very differen t scheme than the commonly used one of a
> single cable through the middle of the boat that terminates in a
> single one-square-foot ground plate, which i s a good way to
> maximize the risk of sideflashes.
> Products that have been developed to a commercial stage are
> described on [14]http://ww w.marinelightning.com/products.htm
> These include the Siedarc (TM) groun ding electrode, the GStrip
> (TM) 1 square foot grounding strip, and the Zzap Strap (TM)
> bonding strap for a boat on a boat lift. The prices on all
> products are less than or comparable to those on similar products
> av ailable elsewhere. For example, a Siedarc (TM) electrode with
> 4 ' of cable is $215 compared with $419 for the single-electrode
> Strikeshield model CSSB-15. The CSSB does come with a mast-mount
> connector, but otherwise the two are very similar. Internal
> connections f or the Siedarc can be made with inexpensive heavy
> duty lugs.
> As you can tell from the above, the installation of a reasonabl y
> effective lightning protection system is not trivial, and every
> boat is a custom job. However, there are huge cost/benefits for
> a one de sign such as the Rhodes 22 if the manufacturer is
> motivated to add th is feature during production. A complete
> system should be possible fo r a few percent of the cost of a new
> boat. This is where your discuss ion group may be able to make a
> difference. If you could convince Gen eral Boats ( 252-482-4372)
> that you, the customer, would like to see this f eature on your
> boat then something is likely to happen. Once a system and
> components have been designed for new builds, retrofits should be
> poss ible at an affordable price.
> I would really like to hel p. Since I have a commercial interest
> in this, it is inappropriate fo r me to post anything directly on
> your message board. However, please feel free to quote me in any
> way that you feel is appropriate, and let me know if there is
> anything else I can do to .
> Best regards,
> Ewen Thomson.
> Arthur H. Czerwonky wrote:
> Dr. Thompson,
>
> We have a discussion in progress on lightning, and how skippers of the
> Rhodes 22 fleet could best provide protection for crew, boat, and
> electronics in the event of a lightning accompanied storm underway. The
> below 'wisdom' is a poor substitute for your studied insights for sure, but
> does this approach hold any promise for effectiveness? The '35 foot
> conductor from mast head to the copper plate' would probably have to be 4
> gauge. Does this solution make sense?
>
> Would appreciate your suggestions.
>
> This reminds me of the first lightning protection system for my
> Mirage 5.5. The maiden crui se in July 1986 was to Cumberland
> Island, GA, in the depth of a thundery su mmer. The new boat had
> not come with lightning protection since the builder assured me
> "we don't add that because it just attracts lightning". &n bsp;
> So I cobbled together a temporary system consisting of two
> fairly large aluminum plates attached to copper braid. The the
> ory was that one end of the braid would be wrapped around the mast
> and the two plates thrown over each side just before a
> thunderstorm. Remember this was 1986, long before I realized that
> tinned copper braid is likely t o corrode any aluminum it comes in
> contact with, and is likely to self dest ruct during a lightning
> strike. In any event, and, with 20/20 hindsig ht, completely
> predictably, the plates never did get deployed. When t he
> inevitable storm rolled in we were nowhere near the boat, which was
> mayb e just as well. We were onshore at Cumberland Island holed
> up in the visitor's center watching the unprotected boat swing
> wildly at anchor as a lightning strike nailed one of our close
> neighbors. Lesson learned:&n bsp; Don't rely on a temporary
> system. Soon after that my Mirage had what was, at that time, a
> state-of-the art system consisting of an aluminum rub rail along
> the centerline that was connected to bow pulpit, chainplate s,
> iron keel, and aluminum rub rail. See [15]http://ww
> w.thomson.ece.ufl.edu/lightning/video.html for a video tour. This
> system is now due for an upgrade. Even though the boat spends the
> ma jority of its life on a trailer, the aluminum rub rail is
> corroding. Besides, it is in the middle of the boat rather than
> near the waterline and so is scheduled to be pulled off and
> replaced by six electrodes just above the waterline. Also, the
> connections were not up to par and will be beefed up to be at
> least as good as #4 gauge copper wire. The d esign constraints
> are tight given the limited interior space of the Mirage 5.5, and
> the main problem is not how to do it, but how to do it most simply
> , with the least cost, and acceptable aesthetics.
> There are a couple of interesting postscripts to the 1986
> discussion/argument concernin g lightning protection. The
> question as to whether the act of groundi ng a mast increases the
> risk of a lightning strike was a valid one. W hile a scientific
> explanation based on electrostatic theory predicted that bridging
> the short gap between mast base and water should have an ins
> ignificant effect on the electric field at mast head, that is, an
> answer in the negative, it would be nice to get some empirical
> answers. So Sea Grant funded a two-year research program in part
> to get an answer. The res ults are published in a Sea Grant
> bulletin (SGEB17 - see
> [16]http://www.thomson.ece.ufl.edu/lightning/SGEB17.html or
> [17]http://nsgl.gso.uri.edu/flsgp/flsgpg92001.pdf ) and presented
> in a video ( [18]http://www.thomson.ece.ufl.edu/lightning/video
> .html ) The answer to the strike probability question is given&nb sp;
> at [19]http://www.thomson.ece.ufl.edu/lightn
> ing/SGEB17.html#Attachment In another development, the buil der, Ken
> Fickett of Mirage Manufacturing, has since become a st aunch advocate
> of lightning protection and close collaborator. We are just
> completing the first installation of a complete system
> on a&nbs p; Great Harbor 47 which we plan to write up for
> publication in PassageMake r.
>
> R,
>
> Art Czerwonky
>
> -----Forwarded Message-----
>
>
> From: "Arthur H. Czerwonky" [20]<czerwonky at earthlink.net>
> Sent: Jul 29, 2006 6:31 PM
> To: The Rhodes 22 mail list [21]<rhodes22-list at rhodes22.org>
> Subject: Re: [Rhodes22-list] sailing and lightning (long reply)
>
> John,
>
> Helpful insights on a nebulous potential problem. This could be a logical
> approach - about 35' of insulated heavy gauge cable run up the mast on the
> main halyard connected so as to project the top end about 12" above the
> masthead, connected to the other end with a copper plate welded/soldered and
> crimped, which would be put into the water near one of the upper side
> stays. The top end would best have a 'spear' type end attached. It would
> be used when strike probability is high, otherwise stowed
> forward. Thoughts?
>
> Art
>
>
>
> -----Original Message-----
>
>
> From: John Lock [22]<jlock at relevantarts.com>
> Sent: Jul 29, 2006 3:12 PM
> To: The Rhodes 22 mail list [23]<rhodes22-list at rhodes22.org>
> Subject: Re: [Rhodes22-list] sailing and lightning (long reply)
>
> At 03:31 PM 7/28/2006 -0700, Tootle wrote:
>
>
> http://www.cdc.gov/nasd/docs/d000001-d000100/d000007/d000007.html
>
> And since John Lock would rather read than sail, maybe he should reasearch
> this one.
>
>
> That is an incorrect statement. I would rather be sailing! But
> since I am nowhere near water and don't have a boat, well...
>
> I already did some research on the subject because it concerned me
> when the sailing bug first bit (not long ago). Here are some salient
> facts and observations that I have found valuable - YMMV.
>
> First, there are two schools of thought on adding lightning
> protection to your boat:
>
> 1) Lightning is a random and poorly understood phenomenon. Trying to
> avoid or control it is probably futile and the results will be random
> and poorly understood.
>
> 2) Doing something is better than doing nothing and maybe it will
> help. Besides it's a cool project.
>
> I suspect that both points of view have merit and which one you
> subscribe to probably says more about your personality than your
> technical skills ;-)
>
> SOME INTERESTING FACTS _
>
> * Boats in saltwater are more likely to be struck than boats in
> freshwater, due to saltwater's higher conductivity. However, boats
> struck on freshwater are more likely to be severely damaged due to
> the higher current loads in the strike itself. (All this being
> relative to the small likelihood of getting hit in the first place.)
>
> * Powerboats are potentially more dangerous in a storm than
> sailboats, because their lower profile means a greater amount of
> current is needed to make a strike. So, if you're out in a typical
> fiberglass runabout and get struck, poooof.
>
> * Being caught out in a sailboat during a lightning storm does not
> mean you are going to be struck. There are many accounts of people
> witnessing water strikes very near their boats. Many other factors
> are involved in setting up a lightning strike.
>
> * Boats with lightning protection systems "may" be more likely to be
> struck, but experience less damage. There only seems to be anecdotal
> evidence of this, but the theory seems sound. That is - if you give
> lightning somewhere to go, it may hit you first, but be dissipated
> more readily (see more on this further down).
>
> SOME MYTHS TO BE DEBUNKED -
>
> "Mooring your boat among boats with taller masts will protect you"
>
> Lightning is seeking it's best path to ground. Height (or the
> distance of the "air gap") is only one factor. Other factors - such
> as mast/keel composition, deck or keel stepped masts, presence of
> other grounding objects near the waterline, etc - will ultimately
> decide the lightning path. For example, a lead-keeled, keel-stepped
> boat may be more likely to be struck than a deck-stepped, centerboard
> boat with a taller mast. And you can't survey all those boats you've
> parked amongst, so it's false security.
>
> "Clamping jumper cables on a shroud and dangling the other end in the
> water is good enough"
>
> While that sounds good on the surface, it is in fact a very bad
> idea. The problem is that you are depending on relatively small
> surface areas to conduct a helluva lot of current. The connection
> points between the shroud and the mast and the jumper cable clamp and
> the shroud are not sufficient to conduct the amount of current a
> strike produces. However, you have increased the likelihood of a
> strike by providing a grounding path. I would strongly discourage
> this practice. (There is also a similar method, which involves
> wrapping the anchor chain around the mast. Same problem.)
>
> "Adding a good lightning protection system will protect me and my boat"
>
> Well, maybe... There is at least one documented case of a
> well-protected boat being sunk by a strike. The mast and all the
> shrouds were grounded via heavy copper cable to a copper plate
> epoxied onto the bottom of the hull. However, there was some
> moisture behind the plate. When the strike occurred, that moisture
> was instantly vaporized into steam and exploded the plate off the
> hull (with obvious results).
>
> SOME GOOD IDEAS IF YOU PLAN TO ADD A LIGHTNING SYSTEM -
>
> * Use nothing but heavy-gauge (#4 or larger) copper conductors. All
> other materials will corrode or provide inferior conductivity.
>
> * Keep all leads as straight as possible. Any sharp bends or kinks
> will defeat the purpose.
>
> * Provide lots of contact surface. Snaps, hooks, turnbuckles, etc.
> will not conduct the current loads you get in a typical strike. Use
> large connecting plates, bolts, and flat washers, clean connecting
> surfaces and seal from weather.
>
> * If you have a system installed, don't do anything to defeat it if
> you're caught in a storm. For example - don't hold onto the backstay
> while you pull up the swim ladder or fiddle with the outboard. You
> may involuntarily become an integral part of the lightning system (as
> Bill E. so eloquently described :-) )
>
> VARIOUS LIGHTNING PROTECTION SYSTEMS -
>
> There are basically three commercially available systems in use at
> varying costs and perceived effectiveness. Again, this assumes that
> you subscribe to the "something is better than nothing" school of thought
> -
>
> 1) Complete grounding systems - the mast, shrouds, motor, electronics
> and any other conductive materials are wired into one or more
> grounding leads, which go thru the hull to a flat copper plate
> affixed to the exterior. Yep, that means you have to drill one or
> more holes to bring the conductor thru and (as shown in the example
> above) must be mounted with great care to eliminate all possibility
> of moisture behind the plate. These systems are usually
> professionally installed, custom designed for each boat, and cost
> mucho bucks. See
> [24]http://www.marinelightning.com/Information/GroundingGuide.htm for
> some details on this.
>
> 2) Static dissipators - These are like inverted stainless steel
> "whisk brooms" attached to the top of your mast. The theory is that
> the many small metallic points offered by the strands of the device
> will dissipate charges gradually as they build up, rather than
> allowing potentials to increase to the level of a full strike. There
> seems to be little evidence that this actually works, since it's
> supposed to prevent a strike. So... you could say if you don't get
> hit, it must be working! They are cheap and have the added benefit
> of keeping birds off your masthead. See example at
> [25]http://www.yachtgard.com/lightning.html
>
> 3) Mast grounding systems - These work on the same principal as #1
> above, except the focus is entirely on the mast, rather than the
> whole boat. The idea being that if lighting strikes the mast (most
> likely point), we should give it somewhere to go before it can cause
> any damage. In concept, this is similar to the "jumper cable" method
> mentioned earlier, but approaches the problem in a more realistic
> manner. A large copper conductor is bolted to the mast and attached
> to heavy copper cable, which can be removed and attached when needed,
> leading into the water. The water-end usually has some kind of
> device attached to increase its surface area in contact with the
> water. See [26]http://www.strikeshield.com/ for a commercial example.
>
> There are many online resources on lightning and boats, protection
> systems, theories, rumors, innuendo... hey, after all it IS the
> Internet ;-) Try a search on "lightning protection for sailboats"
> and you'll get plenty to confuse you further.
>
> And finally, to Mike W: there are two problems with your system - an
> aluminum plate (1) with a right-angle bend in it (2). You'd be much
> better off with a flat copper plate attached to the conductor without
> any bends. I don't know what the physical constraints inside the
> trunk are, but there you have it.
>
> Cheers!
>
> John
>
> "Ever wonder what the speed of lightning would be if it didn't zigzag?"
>
> __________________________________________________
> Use [27]Rhodes22-list at rhodes22.org, Help? [28]www.rhodes22.org/list
>
>
>
>
>
>
> --
>
> Ewen M. Thomson, Ph.D.
> Marine Lightning Protection Inc.
> 3215 NW 17th Street< /FONT>
> Gainesville, FL32605-2511
> USA
> Phone: +1 352 373-3485
> Emai l: [29]ewent at marinelight ning.com
> URL: [30]www.marinelightning.com
>
> Innovative scie nce and technology for lightning protection of
> yachts.
>
>
>
> --
>
> --
>
> --
>
>
>
> --
>
> References
>
> 1. 3D"http://www.marinelightning.com"/
> 2. 3D"http://list/
> 3. 3D"http://www.marinelightning.com"/
> 4. 3D"http:/ 5. 3D"http://www.n/
> 6. 3D"http://www"/
> 7. 3D"http://media.libsyn.com/media/n 8. 3D"mailto:
> rhodes22-list at rhodes22.org"
> 9. file://localhost/tmp/3D"ht 10. ="
> http://www.marinelightning.com/AirTerminals.htm"
> 11. 3D"http://www.mari/
> 12. 3D"http: 13. 3D"http://www.marinelightning.com/science.htm"
> 14. 3D"http://www.marinelightning.com/products.htm"
> 15. 3D"http://www.thomson.ece.ufl.edu/lightning/video.html"
> 16. 3D"http://www.thomson.ece.ufl.edu/lightning/SGEB1 17. 3D"
> http://nsgl.gso.uri.edu/flsgp/flsgpg92001 18. 3D"
> http://www.thomson.ece.u/
> 19. 3D"http://www.thomson.ece.ufl./
> 20. 3D"mailto:czerwonky at earthlink.net"
> 21. file://localhost/tmp/3D"mailto 22. 3D"mailto:jlock at relevantarts.com"
> 23. file://localhost/tmp/3D"mailto 24. 3D"
> http://www.marinelightning.com/Inf 25. 3D"
> http://www.yachtgard.com/lightning 26. 3D"http://www.strikeshiel/
> 27. 3D"mailto:Rhodes22-list at rhodes 28. 3D"http://www.rhodes22.org/list"
> 29. 3D"mailto:ewent at marinelightning.com"
> 30. ="http://www.marinelightning.com"/
> __________________________________________________
> Use Rhodes22-list at rhodes22.org, Help? www.rhodes22.org/list
>
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