Re: [campernicholson] Lightning Protection
There are a lot of myths and misinformation surrounding lightning
protection. Fortunately the laws of physics still apply, so there are
some basic precautions that a vessel owner can take to maximize their
safety and that of the vessel. Unfortunately there isn't much that can
be done to protect onboard electronics as these are often damaged by
high voltages induced on internal wiring connected to sensitive
1. Provide a suitably sized, low resistance path to ground leading
directly down from the air terminal.
In the case of a sailboat, the air terminal is either the top of the
aluminum mast, or pointed rod mounted ABOVE the highest fixture (e.g.
vhf antenna) on the mast. ABYC standards dictate the minimum surface
area of an underwater grounding plate for both salt or fresh water, and
also the use of minimum 4 AWG conductor size to connect the air terminal
(base of aluminum mast) to the grounding shoe.
NOTE: stainless steel is a poor conductor compared to aluminum or
copper, so relying on your standing rigging as a primary grounding
conductor is likely to lead to turnbuckle or swage damage.
2. Provide suitably sized secondary grounding paths, to minimize side
flashes and crew hazard.
All exposed metal such as shrouds, lifelines, stanchions, binnacle,
pushpit & pullpit should be grounded with minimum 6 AWG sized
conductors, leading to the primary grounding point. In addition, metal
hardware such as water or fuel tanks located near the primary conductor
(mast base) should also be bonded to prevent side flashes.
3. A lightning strike delivery huge energy in a very short duration.
With properly sized hardware and low resistance connections, there is
really no reason for anything to heat up enough for damage to occur.
Most vessel suffering hull damage either had an inadequate ground system
(if at all), or defective/corroded underwater fittings that became
While I don't have the standards book in front of me here at home, if
anyone wants more information, feel free to contact me directly.
ABYC Certified Marine Electrician
Oxford Boatyard, Oxford, MD
JIM TEIPEN wrote:
> Articles that I've read on the topic over the years don't seem to
> have any real consensus on the topic. Ground plates on the bottom of
> the hull seem to be common, but other sources I've read say this
> isn't a good idea since lightening can leave a hole at the point of
> exit to the water. These articles say that its better to run a heavy
> conductor either from a shroud or from the mast itself directly to the
> water. In the situation like you described where you were caught out
> in a storm, you might consider carrying a something like a heavy duty
> car battery jumper cable to use as a temporary ground for your mast or
> shroud to the water.
> CN 35 - 68
- Hello AlbertWhen 'Blue Days' (35/209) was built, Camper and Nicholson earthed the mast to an 8" x 2.5" Dynaplate, mounted adjacent to the mast on the starboard side. Originally they fitted a rather small wire but, at my request, replaced this with a wire of starter cable proportions.More recently I have fitted surge protection devices at the base of the mast in the downleads for all the masthead aerials. These are also earthed to the same Dynaplate. The devices, supplied by RS in England, are of the type used to protect commercial radio aerial installations and are suitable for most coax wires. They are rather expensive but much cheaper than replacing toasted electronics! Admittedly this does leave the wind speed/direction sensor unprotected but I have not found anything suitable for the multi-core wire from this.I don't claim any expertise in this field but assume that the action I have taken improves the chances of surviving a lightning strike without damage. To my knowledge the installation has not been put to the test but, should a strike ever happen, I hope the lightning will find that the earthed mast provides a better route to earth than the other masthead equipment which have a degree of inherent isolation.I hope this adds something useful to this interesting discussion.Regards,Michael Forsdyke
"Albert G. Boyce" <Albert_Boyce@...> wrote:I am wondering what other Nicholson 35 owners have done for lightning
protection. I have developed a keen interest in lighting protection
after getting caught out on the Chesapeake in a thunderstorm last week
and getting a mild electric shock at the helm while steering the boat.
Quite a wake up call. I have hull number 132 and there is a small
sintered bronze plate on the outside of the hull that is connected by #8
wire to the mast.
None of the shrouds, stays, lifelines, stanchions, or any other metal
objects are grounded or otherwise connected to this plate
I look forward to hearing what lightnting protection arrangements others
have in place on their boats.
Discovery CN35 #132
- Hi John and GailWe're heading for Passport on the 28th or 29th of July and will be around Rockland for a few days getting ready, then cruising Penobscot bay also. Lets stay in touch and try to meet somewhere, hopefully with the rest of last year's group.We haven't had any squeaking from the helm, but we did have a knocking noise which turned out to be worn rudder shaft packing. We replaced the packing and the noise went away, at least so far.You may develop topsides envy when you see Passport, but you're bank account is likely in a lot better shape than ours. All that prettiness costs lots.Hope to see you two and the rest of the group while we're in Maine.John and Sandy Larsons/v Passport
- Our plans are to be in Holbrook Harbor (Castine) for 27th/28, two
nights in Belfast (29/30), the 31st - thursday - in Dark Harbor on
Isleboro or thereabouts and in Rockland the 1 and 2nd of August.
From there we will probably go to Perry Creek on Vinalhaven. After
that we'll wander aroound, but we'll leave from Tenants/Port Clyde on
the 6th (at the latest) for Gloucester
Hope we can get catch up.
As to my bank account, I would rather have invested it in my hull,
rather than watch it evaporate as it has done in the past few
--- In firstname.lastname@example.org, "JOHN LARSON" <jsl-sll@...>
>around Rockland for a few days getting ready, then cruising Penobscot
> Hi John and Gail
> We're heading for Passport on the 28th or 29th of July and will be
bay also. Lets stay in touch and try to meet somewhere, hopefully
with the rest of last year's group.
>knocking noise which turned out to be worn rudder shaft packing. We
> We haven't had any squeaking from the helm, but we did have a
replaced the packing and the noise went away, at least so far.
>bank account is likely in a lot better shape than ours. All that
> You may develop topsides envy when you see Passport, but you're
prettiness costs lots.
> Hope to see you two and the rest of the group while we're in Maine.
> John and Sandy Larson
> s/v Passport