I think I’ve seen the standard ground strap installation in a SLM
promotional video. I think it depicted copper tape coming down from the
chainplates extending down into the keel (before the lead is installed). I
think there was also a horizontal copper tape tee-ing into the downward
tape, although I’m not sure where it goes (fwd? Bobstay stem fitting?). I
think the yard bonds the copper in place with some fiberglass tape.
My recommendation would be to install 2" or 3" copper tape from the upper
shrowd chainplate through bolts, down into the keel (before lead is
installed), and install an external grounding plate through bolting the hull
and the copper tape. Then glass over the tape with some light FG cloth, and
then drop the lead in.
I talked with Larry Pardey at the Annapolis boat show a few months ago about
lightning protection on Taleisin. I have a wood mast, so I was interested
in how Larry approached the topic (the air in wood has a tendency to expand
explosively when subjected to lightning strikes). Larry designed his
chainplates to be longer than usual, so that they would extend well below
the waterline. The strike is supposed to follow the upper shrowds to get to
water via the external chainplates.
I read somewhere that factory boats have a grounding strap installed
in the fiberglass incased lead ballist. Any advise on how or where
to
install a strap on a bare hull.
I have a lightning system which doesn’t go down into a grounding plate
attached to the hull. Roger mentioned the setup he used on Xiphias
so I copied it. I have aluminium cables (guy wire cable) attached
to the mast at the lower spreaders, running down port and starboard
shrouds to the chain plates. Then I switch over to long battery
cables that hang overboard into the water. The cables are detachable
so I only use them when a storm is around.
I was struck by lightning last year. The strike blew off the VHF
antenna, wind indicator and mast head light. I couldn’t really tell
if the lightning traveled down the wires, but Godspeed is still
floating…
I think I’ve seen the standard ground strap installation in a SLM
promotional video. I think it depicted copper tape coming down from the
chainplates extending down into the keel (before the lead is installed). I
think there was also a horizontal copper tape tee-ing into the downward
tape, although I’m not sure where it goes (fwd? Bobstay stem fitting?). I
think the yard bonds the copper in place with some fiberglass tape.
My recommendation would be to install 2" or 3" copper tape from the upper
shrowd chainplate through bolts, down into the keel (before lead is
installed), and install an external grounding plate through bolting the hull
and the copper tape. Then glass over the tape with some light FG cloth, and
then drop the lead in.
I talked with Larry Pardey at the Annapolis boat show a few months ago about
lightning protection on Taleisin. I have a wood mast, so I was interested
in how Larry approached the topic (the air in wood has a tendency to expand
explosively when subjected to lightning strikes). Larry designed his
chainplates to be longer than usual, so that they would extend well below
the waterline. The strike is supposed to follow the upper shrowds to get to
water via the external chainplates.
I read somewhere that factory boats have a grounding strap installed
in the fiberglass incased lead ballist. Any advise on how or where
to
install a strap on a bare hull.
i do not have a bcc, but i just reviewed this topic with my surveyor. after my
last squall on the chesapeake, i got a piece of chain in a pvc hose to dangle off
my upper shroud into the water. this amused my surveyor, who thought it
ineffective. the ABYC recommendations are for the mast and all rigging to be
grounded with green #8 awg wire in as strait a line as possible to a copper plate
one foot square as close to the base of the mast as possible. the recommendation
goes on to suggest that all major metal objects are connected as well. the idea
is to prevent lightning strikes by bleeding off the static charge to ground and
equalizing the voltage between the masthead and the sea (ground potential).
practical sailor has recently had articles on the dissipators ($300 brush) and the
fact that they are not completely effective. at least one company that has
guaranteed to pay for damages if the thing is installed has routinely failed to do
so. the #8 wire is supposed to also give the lightning bolt a place to go to
ground easily and with minimal damage if the boat is struck. i believe that the
grounding strap seen in the video is for bonding associated with reduction of
electrolysis although the ballast is also reported to be a good counterpoise for
ssb.
i have grounded my boat per abyc standards. having been a eyewitness to a
direct lightning stike on a lamppost at less than 100 yds away however, it is my
opinion that a strike is likely to cause major damage and that the #8 wire (or
even batt cables) are probably way too small for the fury of mama nature. that
lightning would probably burn the ground plate right thru the hull if it felt like
it, but at least i have done what i can.
john churchill