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Old 14-04-2012, 17:54   #1
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Do I need a dynaplate?

The age old question and argument over bonding v. grounding v. lightning protection.

I have a 3"X8" sintered bronze dynplate on the hull exterior. Used to be an old defunct SSB on board. No longer. Coastal US cruising only at this point. All DC returns to a common dc buss and finally the engine block. Through hull and other bonding was tied into the dynaplate(?) as well as a lighting bond from the mast and then all tied into the dc neg buss.

I would greatly appreciate any new thinking on this confusing question.

Ditch the dynaplate? Find a lightning ground plate for the mast and keep it isolated?

No hot marina here, residing on a mooring, fairly hot river. What are you all doing out there?

Thanks for any input!!
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Old 14-04-2012, 21:53   #2
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Re: Do I need a dynaplate?

On the exterior? I thought Dynaplates went over the keel?

Not an expert, because I have a cambered steel deck. The whole frickin' boat's a Dynaplate.

What you are describing sounds more like a plate anode...but that would not likely be bronze, but zinc or magnesium.

A ground plate for the keel-stepped mast is usually 1/4 or 1/2 inch aluminum bolted from the mast base to a keel bolt.
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Old 14-04-2012, 22:29   #3
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Re: Do I need a dynaplate?

Alchemy, the sintered bronze plate is indeed a Dynaplate and they are through-bolted to the hull.

I don't think the Dynaplate is going to make much difference with your lightning protection, but it couldn't hurt. When it comes to SSB, it's also not much better than a bronze through-hull, but it does do the job. If it bothers you I would remove it. Of course then you have to patch the bolt holes.
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Old 15-04-2012, 09:23   #4
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Re: Do I need a dynaplate?

Thanks for the clarification. For some reason I thought they were perpendicular to the antenna, and not offset. Just goes to show where the holes in my knowledge are clearly marked as forum hazards.
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Old 15-04-2012, 09:28   #5
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Ssome dynaplates specifically say they cannot be used for lightening protection. In essence the explode as the heat from the strike gasses the water trapped in the designed porosity. Better to use a long copper bar and big through bolts for lightening.
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Old 15-04-2012, 10:00   #6
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Re: Do I need a dynaplate?

AC & DC grounds, lightning grounds, bonding system grounds, and HF/SSB grounds are all different and mostly need to be kept separate.

Here's a good primer. Read it carefully...it's got the answers to most of your questions:

Grounding

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Old 15-04-2012, 13:38   #7
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Re: Do I need a dynaplate?

As sabray said. A Dynaplate should NOT be used for the lightning ground. Because sintered bronze is porous, it has a great deal of surface area "inside" the block, which makes a great radio frequency ground. And it hit by lightning, all that surface area means a lot of seawater flashing into superheated steam at the same instant, inside the plate. "Kaboom". Not a good thing.

It could be useful for the bonding system, but I'd be concerned that lightning could flash over and hit it anyway, unless there was a much more attractive lightning ground.
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