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Old 04-17-2015, 01:38 PM   #1
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Grounding Plate On A Trawler

Do you need to have a grounding plate on a trawler? I had a sailboat that I installed a grounding plate on the keel since all of the lightning protection ground wires went there. My thought was that after a new bottom job the keel is insulated from the water, until your first grounding. That way the lighting has a clear path out of the boat. (After a direct hit in Atlantic City this proved true. A hard hit on the mast, blown electronics, but no damage to the hull.)
Now the trawler I am looking at does have a single side band radio. I am guessing this is why the stern has two ground plates. But is that the reason? The plates are in poor shape. Is there a good reason to keep the single side band radio? My travels are always on the ICW.
Any help would be appreciated
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Old 04-17-2015, 05:39 PM   #2
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Are you sure that the two plates on the transom aren't zinc anodes that are connected to the bonding system for corrosion protection?

Also even though I am familiar with the theory of directing a lightning strike to a grounding plate to let the strike exit there rather than blow out the hull someplace else, I am very skeptical. No trawler manufacturer that I know of, not even Nordhavn , does this.

David
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Old 04-17-2015, 05:56 PM   #3
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Grounding Plates for SSB radios are common on Nordhavn trawlers. Mine are located near the port side stabilizer/keel cooler. I've never heard of one for lightning protection.

With modern satellite communications I'm not sure SSB radios are quite as useful as they once were. I think of it primarily as a backup method of communications.
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Old 04-17-2015, 05:58 PM   #4
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Grounding Plate On A Trawler

Ours does. A what looks to be #4 wire runs directly to the stack stainless dome spreader antenna spreader. Also we have a ground setup for the SSb even though I chucked it. Here are some pictures. There is a copper strap that connects everything together for the SSB. First picture is copper mesh in the ceiling for the SSB, second is the plate.
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Old 04-17-2015, 08:53 PM   #5
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Quote:
Originally Posted by djmarchand View Post
Are you sure that the two plates on the transom aren't zinc anodes that are connected to the bonding system for corrosion protection?

Also even though I am familiar with the theory of directing a lightning strike to a grounding plate to let the strike exit there rather than blow out the hull someplace else, I am very skeptical. No trawler manufacturer that I know of, not even Nordhavn , does this.

David

No I am not sure if they are anodes, good question.
The Lightning ground plate was on my sailboat. Several blue water sailboat manufactures use the exposed ground plate for this reason. Caliber Yachts for one. A friend of mine had his 41 foot sailboat struck by lightning while it was in the yard. There was a hole blown through his hull at each jack stand! That was enough for me. But we are talking about sailboats. I am not sure I would rig a trawler the same way or at all for lightning protection.
Thanks for your comment I will find out from the owner what the two plates are for.
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Old 04-17-2015, 08:55 PM   #6
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Quote:
Originally Posted by Boydski View Post
Grounding Plates for SSB radios are common on Nordhavn trawlers. Mine are located near the port side stabilizer/keel cooler. I've never heard of one for lightning protection.

With modern satellite communications I'm not sure SSB radios are quite as useful as they once were. I think of it primarily as a backup method of communications.

I am inclined to agree that maybe a SSB would be of little use to me. And I am not sure I like having that big antenna on the boat.
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Old 04-17-2015, 08:57 PM   #7
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Quote:
Originally Posted by N4712 View Post
Ours does. A what looks to be #4 wire runs directly to the stack stainless dome spreader antenna spreader. Also we have a ground setup for the SSb even though I chucked it. Here are some pictures. There is a copper strap that connects everything together for the SSB. First picture is copper mesh in the ceiling for the SSB, second is the plate.
Attachment 39271
Attachment 39272

The copper plate above your keel cooler is what our sailboat had for all the ground wires that had been run from each of the standing rigging.
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Old 04-20-2015, 11:01 AM   #8
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I have a ground plate, but that was more back in the day way of thinking, now more of a hassle in that I need to clean the barnacles off it every month during the summer.
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