[Rhodes22-list] Lightning 'Cone of Protection' Fw: Overhead and
underfoot metal
Arthur H. Czerwonky
czerwonky at earthlink.net
Wed Aug 2 16:51:43 EDT 2006
FYI
Art
-----Forwarded Message-----
From: Ewen Thomson
Sent: Aug 2, 2006 2:31 PM
To: "Arthur H. Czerwonk Subject: Overhead and underfoot metal
< I promote the concept that the best way to NOT be the at point for a lightning strike is to have metal overhead.
without, at le Sidefla mast and the in the hull increases the risk of Regards,
Ewen.
[1]www.marinelight 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 result of the array
Some have felt that grounding, by creating a most direct path to the
w to strik
Cheers,
Art
-----Original Message-----
From: Ewen Thomson
Sent: Aug 2, 2006 10:51 AM
To: "Arthur Subject: Re: Fw: Re: [Rhod reply)
Art,
Thank made any diff me to note tha protection on these boat resort, with storm avoidance being the very misleading as it could be interpreted to lightning protection system is less important than e.g. buying $800 GPS system so that the storms can be tracked! Needless to say
being imprac 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 at the MacG [2]http://list.sailnet.net/read/?forum 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 Subject: Re: Fw: Re: [Rhode 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 Sent: Jul 30, 2006 1:12 PM To: "Arthur H. Czerwon Subject: Re: Fw:
Re: it contains s below,&nbs - Being caught ou storm does not mean you are going to be this one comes with a disclaimer. Compar being in a m 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 marinas. My best a my web pages at [3]www.marineli recently. But even here I realize tha scattered over so many pages that it is difficu sailor to come to grips with the most important concepts, a opposed to, for example, much cheaper product that, if you bel
prevent l [1][4]http://www.ma rinelightning.com/AirTerminals.htm . For
another whose bristle brush page [2]www.marinelightning.com foundation in peer-reviewed science, bei observations of actual damage, and being considered by 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 reaso key point here is that we attempt to protection system th simulates that on a buildin multiple air terminals, down conductors
on t perimeter. Note th ground plate risk of sideflas include the Siedarc ( square foot grounding on a boat lift. Th than or comparable to those on sim elsewhere. For example, a Siedarc (TM) electrode wit cable is $215
CSSB-15. Th otherwise the two are ve Siedarc can be made with inexpens tell from the above, the installation of a protection system is not trivial, and every boat is a c 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 the customer, would l happen. Once components have been retrofits shoul possible at an affordable price. li in this, it is inappro your message board. Howeve way tha feel is appropriate, an anything else I can do to . Best reg Ewen
Tho discussion in prog Rhodes 22 fleet could best provi electronics in the event of a lightning a underway. The below 'wisdom' is a poor substitute for your 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 sense? Would appreci It looks as though a lot of lines were choppe quite a mess. Also, in an earlier post I found an to my furled sails interview. The correct link is&nbs [7]http://media.libsyn.com/media/noeld/furled The main point in my message was that impr lightning protection should be the responsibility of the b 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 Regards,
Ewen.
Arthur H. Czerwonky wro
Ewen,
The URL is "[8]rho bounced around a somewhat consensus tires) the sailboat confi underway are quite low, and that mast creates a 'cone of protection'.&n grounded to the water, the perception is that the o a strike are greater, since there is an easier path of tr the mast/stays/conductor. Your input has been most helpful.<
Art
-----Original Message-----
From: Ewen Thomson
Sent: Aug 1, 2006 12:16 PM
To: "Arthur Subject: Re: Fw: Re: [Rhod reply)
Art,
Thanks fo can keep track o Please see my comments below.
Regards,
Ewen.
<
Ewen,
I will forward your email into the board, which I agree is a more
suit
According to the article attached to your bpage with the 23 min
video, hit. If an
4 gauge is the recommended mini
conductor were bolted to the mast step (deck located step, traile rable) in a very secure manner,
copper in contact with a
welded to a 1' square copper plate, and suspended over the closest
acc greater d greater danger?&
If you could do this on both sides it would provid grounding in salt water, although welding is likely to weaken t cable connection at the joint. In fresh water additional gro unding conductors would still be needed, especially at forestay and
backsta mast to equ practical point of view, the water and dent your hull, and risk of not being deployed and is a hazard t Also, if there are any other immersed metals (stainle 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
The mast is already aluminum which is a suitable lightning
conductor, so to add an air t fittings that should be prot
Your response, and especially your help is greatly appreciated.&n bsp; Your research has to be quite interesting with so many variables
to co
"Interesting" is an understatement a compromise amongst effectivenes the place), cost (fewer is better), aesthe corrosion (no dissimilar metals in the water; if 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 Subject: Re: Fw: Re: [Rhod reply)
Dear Art,
Sinc for me to a "INTERESTING FACTS" ment of them -
Being caught out in a sailboat during a lightning storm does not mean you are going to be struck.
b a thunderst perhaps a factor of five this estimate is Boat US ins lightning damage to catamarans is tw brief explanation for this is that catamarans ar there is less protective effect from neighboring masts in ma rinas.
My best attempt at addressing the relevant issues are 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 difficult for the important concepts, and why shou say, as opposed to, for example, the brist have a much cheaper product that, if you believe them 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 Here is an overview:
The home page [11]www.marinelightning.com summarizes our approach,
as ha consistent wi considered by the lightni Fire Protection Association for inc NFPA 780 (see pages 21-28 in [12]http://www.nfpa.org/Ass ets/Files/PDF/ROP/780-08-ROP.pdf ).
Perhaps the most [13]http://www.marineli historical introduction, processes are described and reasonable sol key point here is that we attempt to build a m protection system that simulates that on a building - with multiple air terminals, down conductors on the outside, and
multiple ground this is a very differen single cable through the middle of single one-square-foot ground plate, which i maximize the risk of sideflashes.
Products that have described on [14]http://ww These include the Siedarc (TM) groun (TM) 1 square foot grounding strip, and the Zzap bonding strap for a boat on a boat lift. The prices products are less than or comparable to those on similar products
av 4 Strikeshield connector, connections f duty lugs.
As you can tell from the above, the installation of a reasonabl effective lightning protection system is not trivial, and every
boat is a a one de motivated to add th system should be possible fo boat. This is where your discuss difference. If you could convince Gen that you, the customer, would like to see this f boat then something is likely to happen. Once a system components have been designed for new builds, retrofits should be
poss I would really like to hel in this, it is inappropriate fo your message board. However, please way that you feel is appropriate, and let me anything else I can do to .
Best regards,
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 Mirage 5.5. The maiden crui Island, GA, in the depth of a thundery su not come with lightning protection since the builder "we don't add that because it just attracts lightning". &n So I cobbled together a temporary system consisting 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 thunderstorm. Remember tinned copper braid is likely t contact with, and is likely to self dest strike. In any event, and, with 20/20 hindsig predictably, the plates never did get deployed. When t inevitable storm rolled in we were nowhere near the boat, which was
mayb up in the wildly at anchor as a neighbors. Lesson learned:&n system. Soon after that my Mirage had state-of-the art system consisting of an aluminum the centerline that was connected to bow pulpit, chainplate 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 corroding. near the waterline and replaced by six electrodes just above connections were not up to par and will be least as good as #4 gauge copper wire. The d are tight given the limited interior space of the Mirage 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 discussion/argument concernin question as to whether the act of groundi risk of a lightning strike was a valid one. W explanation based on electrostatic theory predicted 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 answers. So Sea Grant to get an answer. The res 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 .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 publication in PassageMake
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< Gainesville, USA
Phone: +1 352 373-3485
Emai URL: [30]www.marinelightning.com
Innovative scie 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"/
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