Date: Thu Mar 1, 2001 11:37 am
I just had a SWII surveyed which had all rigging grounded to a plate such as you suggested. The surveyor didn't like it at all. He said the probable outcome in a severe electrical storm would be that a significant "hit" could quite probably blow a hole in the boat at the ground plate!! The broker (also present) suggested his method of (during a storm) attaching two heavy gauge (automotive type) jumper cables (with one end cut off) to the rig on either side and the loose
end hanging in the water. Hope this helps...
Date: Thu Mar 1, 2001 3:20 pm
I have the original relatively small gage white cable running around and tying to all the thruhulls. I agree with the risk of a copper plate, unless it is very very large.
Prevention is best, using an ion dissipator at mast top, I am considering adding one to the mizzen mast. The tufted one is much cheaper than the bottle brush, and seem to work well in some huge storms in the Bahamas and off New Jersey last May-June. At least we were not hit despite lightning everywhere
If I were really scared, I would ground the large stay on each side and each mast plus the forestay as proposed below, with a hanging wire just as thick, or a copper jumping cable as suggested. [When in port, you can hang on these some old zinc to protect agains some stray currents: I love dual use!]
Barring these wires, if you have time before the storm hits, you achieve the same by hanging the main mooring chain in festoon around the boat and back to the forestay, tying it up to each stay encountered and hanging in the water between stays (far enough to not come out when heeling). That is what we used on wooden, engineless boats at the Glenans Cruising Center. That is another way for an electric windlass to pay for itself!
Date: Thu Mar 1, 2001 9:45 pm
We live just north of Tampa Bay, the lightning capital of the United States. We have been hit by lightning twice, once by a very large direct hit and once by a smaller direct strike, both times the vessel was stationary. Our ketch has bronze thru-holes, not grounded. The masts stays are all connected with large copper rod which leads to a moderate size ground plate. After each strike the vessel was examined and showed no visible damage to persons or to the hull. The damage was limited to an antenna and fuses and a alternator. We have seen all types of lightning protection devices that are supposed to prevent a lightning strike over the last 45 years here in Florida and have yet to see one that works!!!! Beware of any surveyor that thinks a ground plate will be blown out of the hull. Last time I looked ours was still attached and many vessel have them in this region. In Florida we avoid plastic thru-holes because they can be blown out leaving a large hole. One vessel lost five plastic thru-holes and sank after being struck. Avoid the plastic unless you have a wooden plug sitting next to it and you're around to put it in. We also have knowledge of two vessels struck by one strike. The vessels were within 30 yards of each other and one suffered major damage, the other, ours, only needed a few fuses. If there were a cure all, those of us in this area with 90 electrical storms per season would all have it. No cure has really come by yet.!
Date: Fri Mar 2, 2001 8:43 am
Can you give more details on your stays grounding: size (shape, lateral dimensions and thickness) and location (along ship and how deep, outside the hull or thruhull) of the groundplate, and diameter/gage of the connecting copper. Are the mizzen stays connected as well?
Obviously your system works, and is not standard on SWIIs. Thanks in advance
Date:Mon Mar 5, 2001 8:25 am
Date: Tue Nov 13, 2001 10:50 pm
Maybe I ran over it a bit likely and too quickly but in my reply I had said:
Try to set up a ground bonding wire of at least 8 gauge USWG to each chain plate and lead the wires to a common ground, preferably to a Dynaplate but the engine block will suffice, as you install each new plate. It will help with your electrolysis and add some lightening protection overall. If it were a cheap or easy job I would suggest a two-inch minimum width, flat, copper bonding strap for better lightening protection led throughout the hull and locker voids. In the event you decide to go to SSB radio in the future it also offers a marginally better ground plane for radio performance.
Electronics arequite sensitive to lightening strikes I certainly agree. Generally speaking there is no totally foolproof isolation for strikes of any significance. I was in the habit of using a heavy duty breaker in a dedicated common ground line led exclusively to a Dynaplate for my electronic gadgets aboard both my Tartan 27 and my Southern Cross. Both suffered several strikes with the breaker purposefully opened and still I replaced a Motorola Sat-Nav, VHF, knot and depth instruments, twice, in both boats. The 100 amp breaker fused in both cases.
I have now been aboard during seven strikes over the years of deliveries. For my money lightening and its effects are more likely unpredictable than determinate. I have had my mustache singed, my palms burned and once watched a ball of lightening race down an open hatch. pass my face and strike the backstay harmlessly, Go figure.
I do however agree thoroughly that metal thru-hulls should have a heavy conductor that leads to separate grounding by a below waterline, zinc anode that protects against naturally occurring, electrolytic leaching as well as isolates far better in the case of a loop-type bonding between them, the chainplates and the common ground.
Date:Sat Nov 17, 2001 10:00 pm