[Rhodes22-list] Lightning mitigation

Sat Jul 14 18:15:54 EDT 2012

Grounding a mast does not protect it from being hit, in fact there is a lot
of evidence that there is a slight increase in incidents.  I think that the
idea is that the flow of electrons can dissipate rather than build up, but
the difference in potential when talking about hundreds of thousands of
volts is very little.  The advantage for a grounded mast is when you are
struck you will direct the path of the electrons and its exit point.  A word
of caution, grounding to a single bronze through hull can have disastrous
results as the fitting can heat almost to incandescence and any water
trapped nearby is vaporized.  I have seen a through hull blown out of a
boat, not good.  You will need something that has several square feet of
surface area such as a copper plate.  Often when an ungrounded mast is hit
the lightning travels to the base of the mast (if deck stepped) and then
jumps to the water line right through the hull.  This can burn a hole in the
fiberglass, but what do we care our boats are unsinkable.

Chris G

-----Original Message-----
From: rhodes22-list-bounces at rhodes22.org
[mailto:rhodes22-list-bounces at rhodes22.org] On Behalf Of Goodness
Sent: Saturday, July 14, 2012 6:59 AM
To: The Rhodes 22 Email List
Subject: Re: [Rhodes22-list] Lightning mitigation

If your boat mast is grounded then a lightning strike to the mast is not
really going to happen.  Many carry jumper cables and when a storm comes up
clamps to a mast fitting and toss the other end overboard.  A more clever
solution is an internal grounding wire to a metal underwater through
hull......however that through hull needs to be protected with a zinc or it
will corrode big time and sink you.  I have seen lightning switches that you
flip in a storm too.  On a dock on a lift, it would be smart to ground the
mast to the actual ground, very little corrosion risk there.

On Jul 14, 2012, at 12:51 AM, peter klappert <peterklappert at comcast.net>
wrote:

> 
> Just to bring you all up to date and ask a question (or two).
> 
> Did I mention that the day I discovered the damage the Tampa Bay Times
reported that Tampa has lost its (completely unofficial) status as lightning
capital of the world?
> 
> I may as well get to the important question right away, then rattle on for
anyone interested in the patient's health. So here's the question: 
> 
> What kind of lightning mitigation does the R22 have? For example, it might
be heavy guage wire or cable connecting the shrouds to centerboard or some
other metal below the waterline.
> 
> Does anyone know? Or has anyone done or modified this sort of thing on
their boat?
> 
> Here's the latest news. If I had more time I could make this shorter, but
it's past midnight and the marine electrician is due at 8 A.M.
> 
> The damage to Aeolia is, of course, more extensive than I knew when I sent
the list under the subject "Major Electrical Problems." But it's not much
more extensive, just quirky and seemingly patternless.
> 
> There is no visible damage to hull cabin or rigging, but most electronics
are fried, as are running and anchor lights; the VHF aerial apparently got
melted out of its mast-top mounting. So far wiring seems to be ok, with some
fuses blown and some not. The outboard's electric starter is gone, but the
motor starts manually and runs like a purring cat. Both main & Genoa look to
be like new--I was concerned because of their proximity to metal. 
> 
> I'll know a lot more after this weekend and hope to have Aeolia out on
Tampa Bay sometime next week.
> 
> The concensus among those I've talked to is that having the boat elevated
on the lift and the aluminun lift itself increased likelihood of my boat
being either struck or damaged by a strike nearby. Still, the total height
of Aeolia on the lift, including 2-foot VHF aerial, is only about 36-37 feet
above mean high tide. 
> 
> One leg of dock wiring is shorted, but that may be unrelated. Aeolia was
not on shorepower at the time and the hull made no direct contact with
metal--it was on the carpet-covered PT lumber of the lift bunks. Odds are
that was part of the problem.
> 
> Obviously I need to make sure the lift is grounded (never thot to wonder
or doubt it until this happened) and the guy who built the dock is looking
into what might be possible and legal by way of a lightning rod on a pole.
His power boat has a 24' metal antenna and has never been struck. My next
door neighbor docked his C & C 34 behind his house for many years without
incident. Lightning strikes--or damage, at least--among the big sailboats on
the other size of Apollo Beach (in Bal Harbor) are reputed to be rare.
> 
> G'night!
> 
> 
> 
> 
> 
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