Grounding Plate

[Jim Cornwell]

Newsletter recently received from Boat US by all of us who insure through them has an article on lightning protection. Recommendation is for a grounding plate to be no less than one square foot, preferably long and narrow with ridges and preferably near the waterline. Yankee's bronze dynaplate is much smaller, about 3" x 8" (I'm guessing) or 17% of the recommended area, and is mounted down at the turn of the bilge. It's bonded to the mast at the steps, so it's the path to ground for lightning. I assume this is all standard throughout the CD fleet. Have others modified their original grounding systems? Is a supplementary lightning ground a good idea (I've thought about deploying a sheet of copper clipped to the backstay with a jumper cable - or maybe two sheets of copper clipped to shrouds on either side)? What does the community think about this?

[John Stone]

Well you know how to pick a controversial topic. The Far Reach is not grounded. I have mixed feelings on it. I have read everything I could find on the topic. I have sailed through terrifying electrical storms and watched lightening strike the water less than 50' away, and let me tell you it made a big impression on me. I have also had a boat hit by lightning. I'm neither convinced one way or the other nor am I convinced the experts really know how lightning works when it comes to boats.. If they did, insurance companies would require lightening protection.

Still, I thought about installing the long narrow strip per RC Collins Compass Marine website. I didn't do it because, in the end, I know too many experienced sailors that simply don't buy into the theory of it being safer to bring the super high voltage associated with lightening into one's boat.

The best I can tell is that the evidence seems to suggest that if you ground your boat you have a slightly higher risk of being struck by lightening, but a lower risk of damage to associated electrical equipment.

Pick your poison, as it were.

[tjr818]

Our grounding plates are sintered bronze with supposedly gives them far more area exposed to the water than a flat bronze plate. One brand, Marinco, describes their plate thus:

Product description for Marinco Standard Dynaplate
Creates dynamic hull bonding and grounding for increased performance of electronics and lightning protection. Features most proven and reliable grounding plate, sintered porous bronze matrix with approximately 50 percent porosity, 48 to 1 grounding area for size, best ground path, 34 percent more grounding than other available plates, streamlined low resistance shape and easy 2-step thru-hull installation. Comes with gold plated terminal mounting bolt and a silver contact coating solution for a positive and permanent connection. 4006 is recommended for lightning protection. 4012 and 4008 are recommended for Loran C or lightning and Loran C. 4018 is recommended for SSB radio, lightning and SSB or lightning, Loran and SSB. Equivalent of copper sheathing is given in minimum column.

As John said, Pick your own poison, but I would not bother adding a another plate. I have often thought about a plate clipped to the shrouds to be deployed during a storm, but if you do that, which shroud do you pick? I can't imagine being tossed about in a storm with copper plates dragging through the water hanging from forestay and backstay, along with port and starboard shrouds.

[Carl Thunberg]

I hear about the idea of ground wire trailing in the water and clipped to the shrouds, or forestay/backstay, and it goes against my every instinct. I can't help thinking about the steel chainplate backing plates that are inside the cabin where my children are taking shelter. Not for me, thanks. I would rather the lightning find an inefficient route to ground than to concentrate it. This may be irrational thinking on my part, but that's my story and I'm sticking to it.

[tjr818]

For those who do not have faith in the experts, you could try this idea;

http://svbellastar.blogspot.com/2012/10 ... trike.html

It is probably as good as some of the other ideas, cheaper than adding a new plate, and something that the kids might enjoy.

[Jim Walsh]

I still have the factory standard equipment sintered bronze Dynaplate. I believe it's 3"X12" (or something close to that). I wire brush it every year just to keep the surface free of accumulated sealife condominiums. I am happy to report that it works perfectly and has kept its host free of lightning for 31+ years. With a product endorsement like that who needs science getting in the way of blind devotion.

[RLW]

I and two friend were aboard my CD 28 when lightning struck in the middle of the night. We were all in our bunks, but awake due to the raucous nature of things. The strike was clearly focused on the masthead, as the gear aloft was reduced to splinters landing all over the deck. The rust on the chainplates came off like a sparkler, seen between the hull and liner. The vhf was fried with burn marks primarily where the antenna cable entered. The alternator was fried, but remarkably the starter still worked. I have no idea if my carefully maintained grounding plate played a role, but in the morning we heard others on nearby boats with taller masts comment on how close the strikes were!

[Steve Laume]

Do remember to ground or bond all new metal accessories you add to your boat. Pulpits, biminis and wind vanes should all be tied to the boats grounding plate.

One of the most frightening times I had aboard Raven was with a violent thunderstorm surrounding me in Cape Cod Bay. I had just installed wind vane and had not yet run the bonding wire. The thing was steering the boat and I didn't want to get anywhere near it. I don't know how much of a risk it was but it did spook me out a bit.

Mostly I just try to stay close to boats that have taller masts, Steve.

[John Stone]

Based on all the reports I have read we should be trying to stay near the multi hulls.

[Sea Hunt Video]

Pulpits, biminis and wind vanes should all be tied to the boats grounding plate.

Steve:

Thanks I installed a bimini almost 2 years ago. It NEVER occurred to me to tie it in to the grounding plate. Yet another project to add to the list. Yea

[tjr818]

Do remember to ground or bond all new metal accessories you add to your boat. Pulpits, biminis and wind vanes should all be tied to the boats grounding plate.

Just a thought, how about all plumbing that you add? Sinks, showers, deck washes, ect. ?

[Jim Walsh]

You guys are starting to scare me. Now I'm wondering what Carl Alberg was thinking when he decided to design my boat with a 46 foot long lightning rod that runs right down through my main cabin and steps on the keel. I may have to see if there exists a wearable Faraday cage.

[Jim Cornwell]

The big danger with a strike isn't that the electronics might get fried unless in the oven, which inconveniences the cook. It's that a strike on the mast will seek a path to ground and may blow a big hole in the hull if a better route isn't provided. It seems that many of us have gotten this far with the original design, mast bonded to Dynaplate, for thirty years or more. Does anyone have an idea how many CDs have been struck?

[RLW]

The first thing we checked after the strike was the thru hulls, as they are known to get blown out by a strike. BTW...the nearby taller rigs did nothing to protect us!

[Neil Gordon]

The big danger with a strike isn't that the electronics might get fried unless in the oven, which inconveniences the cook. It's that a strike on the mast will seek a path to ground and may blow a big hole in the hull if a better route isn't provided. It seems that many of us have gotten this far with the original design, mast bonded to Dynaplate, for thirty years or more. Does anyone have an idea how many CDs have been struck?

A CD30 Mk II took a hit in its slip several years ago. The live aboard owner reported smoking batteries, and there was damage to wiring and to electronics, all of which needed to be replaced, but no structural damage at all to the boat.