Ground Plates

[Clyde A. Phillips]

 

The picture below is a part of a picture that Britton posted.  It shows (indicated by a red arrow) a rectangular "lump" that is at least well painted over, if not also fiberglassed over.  Take a look to see if what I see is what you see:

 

This looks like a Dynaplate to me.  The Dynaplate (a tradename) is a maritime ground used very much like a house ground that oft times uses the underground water pipes to connect the house electric system to the true ground, the earth.  On a vessel that type of ground is needed so the vessel's electric system can be properly grounded using sea water as the earth.  Dynaplate makes several sizes so that all boats may be properly grounded.  Their product is so made to increase the effective area of ground plate.  The smallest, possibly the one pictured, is equivalent of about 12 square feet of copper plating.  It goes up to about 400 square feet of surface. 

As an electrical device it needs to be able to make good electrical contact with the sea water.  Therefore it must never be painted.  This style ground plate is made with a multitude of holes throughout the block thereby increasing the effective contact area.  Paint will fill the holes and insulate the whole, thereby making the "ground plate" ineffective.

I think that a painted Dynaplate becomes totally ineffective as a ground plate and that any effort to remove the paint would not be 100 percent effective.  I personally would replace a painted Dynaplate with a new one.  Remember that the standing rigging is (or should be) electrically connected to the Dynaplate to protect the boat during lightning strikes, which protection I do not want to compromise.