Dynaplate

May 30, 2006
300
Oday 34 Chesapeake Bay
So my dynaplate started leaking. On Karma, it's the bump in the hull that has many coats of antifouling and therefore has been useless way before I've owned her. I've removed the device and have purchased a replacement. Question is to I install the new one and deal with another maintenance item, or do I glass over the two holes and press on.
 
Sep 25, 2008
7,077
Alden 50 Sarasota, Florida
A better alternative is to mount it on the keel.

It makes no sense to attach it to fiberglass in the event it works and dissipates a lightning strike against fragile fiberglass.
 
Last edited:
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
The main reason for having a Dynaplate is to establish a ground plane for a HF or SSB radio. While they might have have some use for bonding or lightening protection, I think the jury remains out on that, since most boats don't have one.

I'd glass over the holes and forget about it.

 
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Sep 25, 2008
7,077
Alden 50 Sarasota, Florida
I can think of no valid reason for using a dynaplate as a substitute for proper RF counterpoise.
The main reason for having a Dynaplate is to establish a ground plane for a HF or SSB radio. While they might have have some use for bonding or lightening protection, I think the jury remains out on that, since most boats don't have one.

I'd glass over the holes and forget about it.

And it’s “lightning”, not “lightening”[SP]
 
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Feb 17, 2006
5,274
Lancer 27PS MCB Camp Pendleton KF6BL
The main reason for having a Dynaplate is to establish a ground plane for a HF or SSB radio. While they might have have some use for bonding or lightening protection, I think the jury remains out on that, since most boats don't have one.

I'd glass over the holes and forget about it.

I am almost going to agree with this, however, that is old school thinking, right along with the 100sqft of copper. Now, the question is asked, what is the purpose of the dynaplate? Is it for lightening protection or for communications? If the former, then I agree with the keel mount. A good lightening strike could blow a big hole in your hull. If for the latter, then get rid of it. Like I said, it is old school. For communications a 4"x6"x.125" copper plate attached to the bottom is as effective as a dynaplate. Now, if your dynaplate is all painted over, then it is useless anyway, so yeah, glass over the hole. JMHO
 
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
I am almost going to agree with this, however, that is old school thinking, right along with the 100sqft of copper. Now, the question is asked, what is the purpose of the dynaplate? Is it for lightening protection or for communications? If the former, then I agree with the keel mount. A good lightening strike could blow a big hole in your hull. If for the latter, then get rid of it. Like I said, it is old school. For communications a 4"x6"x.125" copper plate attached to the bottom is as effective as a dynaplate. Now, if your dynaplate is all painted over, then it is useless anyway, so yeah, glass over the hole. JMHO
So, Brian, I guess you're saying the the Dynaplate is a good solution looking for a problem. ;)
 
May 30, 2006
300
Oday 34 Chesapeake Bay
Thanks for the input. Y'all have verified my thinking as well. Karma has a cast iron keel, everything is bonded to it, at least the engine, and the few thru-hulls left that are metalic. The keel is encapuslated, however thinking that the quickest path to earth would still be the keel as the dynaplate has been pretty much useless since I've owned Karma.
 
Oct 29, 2005
2,355
Hunter Marine 326 303 Singapore
I am almost going to agree with this, however, that is old school thinking, right along with the 100sqft of copper. Now, the question is asked, what is the purpose of the dynaplate? Is it for lightening protection or for communications? If the former, then I agree with the keel mount. A good lightening strike could blow a big hole in your hull. If for the latter, then get rid of it. Like I said, it is old school. For communications a 4"x6"x.125" copper plate attached to the bottom is as effective as a dynaplate. Now, if your dynaplate is all painted over, then it is useless anyway, so yeah, glass over the hole. JMHO
My friend's Hanse 315 came with dynaplate installed and wired. Thru 3-5yrs period he had lightning strikes damaging electronics 5 times. Even when berthed next to my boat. Finally he disconnected the dynaplate and no more failed electronics due to lightning for these few years.

Ken Y
 
May 30, 2006
300
Oday 34 Chesapeake Bay
Yes, lighting is a fickle phenomenon. Any thoughts on removing the ground bonding to my remaining metalic thru-hulls? Seems to me that if lightning were to choose one of them they would be no match to dissapate the energy and be blown out of the hull. And to combat electrolysis seems that the bonding provides a path to other metals for current conduction. Whereas, removing the bonding would in effect isolate the thru-hulls effectively reducing electrolysis.
 

dmax

.
Jul 29, 2018
971
O'Day 35 Buzzards Bay
Bonding combines all the metal bits electrically so that the least noble bit, hopefully a sacrificial anode, will be the one that oxidizes. If you disconnect the bonding wires, each bit is on its own and may start disintegrating.
 
May 17, 2004
5,032
Beneteau Oceanis 37 Havre de Grace
If you disconnect the bonding wires, each bit is on its own and may start disintegrating.
It depends. Generally a galvanic cell requires dissimilar metals both in an electrolyte (salt water) and electrical connection (the grounding wire). In a bonded boat the sacrificial anode protects all the fittings by being both in the water and connected to everything through the bonding system. But if there is no bonding on through hulls they’re out of the circuit and won’t spontaneously galvanically corrode. Other bad things can still happen, for example if an unbonded thru hull sits in bilge water and a power carrying falls in that water. The thru hull then becomes an exit point for current (instead of the current being able to go back on the bonding wires) and will corrode.

Beneteau does not bond its thru hulls, and from what I’ve read some other European builders don’t either.

As for the question on Lightning handling, bonded thru hulls are generally considered safer than not. Lightning is a pretty high voltage, and it’s going to find its way to the water somehow. True that on its way it might damage a thru hull if it’s really a bad direct hit, but if it can’t get out the thru hull it’s more likely to go out the glass.

A boat in our marina was hit a couple years ago. It ended up with about 80 of these star bursts on the bottom. Lots of burnt glass under each one that had to be relaid. I think the thru hulls were replaced too, but it didn’t sink.
1618070542149.jpeg
 
Feb 17, 2006
5,274
Lancer 27PS MCB Camp Pendleton KF6BL
So, Brian, I guess you're saying the the Dynaplate is a good solution looking for a problem. ;)
LOL. You know, I think I would be somewhat OK with the concept of the dynaplate if it weren't for the marketing of the thing. I mean, a small plate with holes that equate to 100sqft of copper. What? really? On what planet? Anyway. There are many who swear by them, and as many that swear at them. But they are basically a zit on the hull if they are painted and most yards just paint EVERYTHING to expedite time. Go figure.
 
May 30, 2006
300
Oday 34 Chesapeake Bay
My fix for the dynaplate :) Filled the holes from the inside with thickened epoxy. Then ground out and laminated with an epoxy/fiberglass sandwich. Ugly now but will be faired and painted over.
IMG_0628.jpeg
 
Nov 30, 2020
79
Macgregor 22 Dania, FL
Does your boat have an HF-SSB radio? If not, remove the Dynaplate and forget about it. Dynaplates were used to provide a ground for the old 2 MHz radiotelephones, and they weren't much good for that. A piece of 4" copper strap the length of the bottom would beat a Dynaplate every time.

Chip V.