Hull Zinc question - what's that thing on the inside??

[AMcC]

I pulled the hull zinc (CD 25D) this past weekend for replacement. On the inside of the bilge, there's what looks like a plastic-covered something - gray plastic, through which the hull zinc bolts stick into the hull... what is that??? Does it also need replacement?

Any good lines on the right size hull zinc replacement?

Thanks.
-Alec

[tjr818]

Hull zinc?? I was not aware that there was one. Are you talking about the sintered bronze grounding plate? As always, photos are a big help.
Maybe someone else will have an answer. Best of luck

[moctrams]

The thing is a Dynaplate It is the boat's bonding system where the thru hulls, stanchions, filler pipes are connected to the bolts securing the Dynaplate to the hull.

Guest Dynaplate Lightning Protection write up

Create a proper bonding and grounding system using Guest Dynaplate grounding shoes to reduce the risk of serious hull damage and electrical shock associated with boat lightning strikes.

A proper bonding and grounding system using Dynaplate shoes will help provide a direct, controlled high-capacity path for lightning dissipation.

SSB and AM radio transmitters rely upon a proper size ground to operate to their designed capacity. A dynaplate grounding shoe helps provide a large solid surface (the water surrounding the boat) to "push off" from. This is technically known as "counterpoise", and the other necessary half of the antenna system.

The bronze Dynaplate material also serves as the next sacrificial metal on the galvanic scale after the zincs, providing another buffer against corrosion of stainless steel parts.

[AMcC]

Ah, Guest Dynaplate... you learn something new every day...
Thanks. I'll figure out what to order over football and Turkey!
I really do appreciate this message board and the help it offers - it was part of the reason I decided to bite the bullet and buy a CD!
-Alec