[Rhodes22-list] Reposted on Lightning (reply of 7/30 1:12pm)
TN Rhodey
tnrhodey at hotmail.com
Wed Aug 2 07:48:42 EDT 2006
Art,
Thanks for re-posting. I agree with his comment about protecting small
sailboats..... " lightning protection on these boats also should be regarded
as a last resort, with storm avoidance being the best defense".
Wally
>From: "Arthur H. Czerwonky" <czerwonky at earthlink.net>
>Reply-To: The Rhodes 22 mail list <rhodes22-list at rhodes22.org>
>To: rhodes22-list at rhodes22.org
>Subject: [Rhodes22-list] Reposted on Lightning (reply of 7/30 1:12pm)
>Date: Wed, 2 Aug 2006 05:33:46 -0400 (EDT)
>
>All,
>I am reposting this reply from Ewan FYI. I was told the first copy was
>quite garbled.
>Art
>
>
>Dear Art,
>
>Thank you for forwarding this lively and interesting discussion. Since it
>contains so many points of view, it is impracticable for me to address all
>of them. For example, of the four "INTERESTING FACTS" mentioned 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 being in a
>marina close to other boat masts, being caught out in a thunderstorm
>increases your probability of being struck by perhaps a factor of five or
>ten. The empirical evidence for this estimate is Boat US insurance
>statistics. Specifically, lightning damage to catamarans is twice that to
>monohulls. The brief explanation for this is that catamarans are wider and
>so there is less protective effect from neighboring masts in marinas.
>
>My best attempt at addressing the relevant issues are contained in my web
>pages at 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 should anyone believe what I have to
>say, as opposed to, for example, the bristle brush salesmen who have a much
>cheaper product that, if you believe them, may actually prevent lightning
>from striking in the first place? (For one answer to this see
>http://www.marinelightning.com/AirTerminals.htm . For another, Boat US
>have a photo of a seriously listing catamaran whose bristle brush is still
>intact at mast head following a lightning strike. )
>
>Here is an overview:
>
>The home page www.marinelightning.com summarizes our approach, as having a
>foundation in peer-reviewed science, being consistent with observations of
>actual damage, and being considered by the lightning protection committee
>of the National Fire Protection Association for inclusion in the 2007
>version of NFPA 780 (see pages 21-28 in
>http://www.nfpa.org/Assets/Files/PDF/ROP/780-08-ROP.pdf ).
>
>Perhaps the most straightforward explanation is that on
>http://www.marinelightning.com/science.htm . After a brief historical
>introduction, the relevant lightning discharge processes are described and
>reasonable solutions are proposed. A key point here is that we attempt to
>build a marine lightning protection system that simulates that on a
>building - with multiple air terminals, down conductors on the outside, and
>multiple grounding terminals around the perimeter. Note that this is a
>very different 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 is a good way to maximize the risk of sideflashes.
>
>Products that have been developed to a commercial stage are described on
>http://www.marinelightning.com/products.htm These include the Siedarc (TM)
>grounding electrode, the GStrip (TM) 1 square foot grounding strip, and the
>ZzapStrap (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 available
>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 for the Siedarc can be made with
>inexpensive heavy duty lugs.
>
>As you can tell from the above, the installation of a reasonably effective
>lightning protection system is not trivial, and every boat is a custom job.
> However, there are huge cost/benefits for a one design such as the
>Rhodes 22 if the manufacturer is motivated to add this feature during
>production. A complete system should be possible for a few percent of the
>cost of a new boat. This is where your discussion group may be able to
>make a difference. If you could convince General Boats ( 252-482-4372)
>that you, the customer, would like to see this feature on your boat then
>something is likely to happen. Once a system and components have been
>designed for new builds, retrofits should be possible at an affordable
>price.
>
>I would really like to help. Since I have a commercial interest in this,
>it is inappropriate for 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 cruise in July 1986 was to Cumberland Island, GA, in the depth
>of a thundery summer. The new boat had not come with lightning protection
>since the builder assured me "we don't add that because it just attracts
>lightning". So I cobbled together a temporary system consisting of two
>fairly large aluminum plates attached to copper braid. The theory 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 to corrode any
>aluminum it comes in contact with, and is likely to self destruct during a
>lightning strike. In any event, and, with 20/20 hindsight, completely
>predictably, the plates never did get deployed. When the inevitable storm
>rolled in we were nowhere near the boat, which was maybe 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: 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, chainplates, iron keel, and
>aluminum rub rail. See http://www.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 majority 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 design 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 concerning lightning protection. The question as to
>whether the act of grounding a mast increases the risk of a lightning
>strike was a valid one. While a scientific explanation based on
>electrostatic theory predicted that bridging the short gap between mast
>base and water should have an insignificant 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 results are published in a Sea Grant bulletin
>(SGEB17 - see http://www.thomson.ece.ufl.edu/lightning/SGEB17.html or
>http://nsgl.gso.uri.edu/flsgp/flsgpg92001.pdf ) and presented in a video (
>http://www.thomson.ece.ufl.edu/lightning/video.html ) The answer to the
>strike probability question is given at
>http://www.thomson.ece.ufl.edu/lightning/SGEB17.html#Attachment In
>another development, the builder, Ken Fickett of Mirage Manufacturing,
>has since become a staunch advocate of lightning protection and close
>collaborator. We are just completing the first installation of a complete
>system on a Great Harbor 47 which we plan to write up for publication in
>PassageMaker.
>
>
>R,
>
>Art Czerwonky
>
>-----Forwarded Message-----
>
>From: "Arthur H. Czerwonky" <czerwonky at earthlink.net>
>Sent: Jul 29, 2006 6:31 PM
>To: The Rhodes 22 mail list <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 <jlock at relevantarts.com>
>Sent: Jul 29, 2006 3:12 PM
>To: The Rhodes 22 mail list <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
>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
>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 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?"
>
>
>
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