Dynaplate and lightning

[CharmCityBoater]

I am seeing very mixed data on using a Dynaplate. For reference I have a 43' Hans Christian. I am wrapping up a complete re-wire of the entire boat. I have LifePO4 batteries (6x 100ah Battleborn). All brand-new electronics. Mast is currently down, and I am getting ready to wire it up now. Going to put a single Morad tuned AIS / VHF antenna on the masthead. LM400 cable down the mast and to my new Icom m605 non-AIS radio along with a Digital Yacht systems AIT5000.

I had planned to use a Dynaplate for grounding of the mast, radio equipment. I have seen a lot of posts that say "DO NOT DO IT" the Dynaplate will explode and leave you with a hole in your boat if you get a lightning strike. I also hear that I should not use the Dynaplate for my DC or AC ground either since it can interfere with clear radio comm. I should have a separate ground on the boat for DC and AC.

So, what says ye oh mighty cruisers forum? Especially interested in hearing from s/v Jedi... I just saw your post about the VHF setup and see "YOU ARE USING A DYNAPLATE". What size Dynaplate?

Thanks

[wholybee]

A dynaplate is fine for VHF or SSB ground. For AC/DC ground (if you decide to connect that to water, which many consider wrong) that should NOT be shared with the RF ground.

Lightning ground should be separate from everything else, and should be a solid plate, not a perforated plate like a dynaplate. A solid plate should be cheaper anyway.

[Statistical]

The standard Dynaplate uses sintered bronze spheres which are ill suited as a lighting conducting path.

Somewhat confusingly named though Dynaplate does have one specific model 4080C which is solid copper and intended as a lighting ground.

From Guest installation instructions

The model 4080C Dynaplate meets ABYC requirements for use in a lightning protection system.

That is likely why you are seeing conflicting advice. They technically are both correct just not specific enough.

[CharmCityBoater]

so... What I have learned...

1. DC / AC grounds do not need a direct path to water. I was of this impression as well, just confirming here.

2. A solid bronze plate works well as a lightning ground path. Should not use sintered bronze.

3. a Sintered bronze plate should only be used for RF ground on VHF / HF radios.

All three above should be separate. Clear as mud?

Thanks

[Statistical]

Originally Posted by CharmCityBoater

so... What I have learned...

1. DC / AC grounds do not need a direct path to water. I was of this impression as well, just confirming here.

2. A solid bronze plate works well as a lightning ground path. Should not use sintered bronze.

3. a Sintered bronze plate should only be used for RF ground on VHF / HF radios.

All three above should be separate. Clear as mud?

Thanks

On #2 solid copper plate is recommended. The electrical conductivity of bronze is much lower than copper. The "C" in 4080C is for copper. Not sure dynaplate makes the 4080C anymore though. You can find references to it but I don't see any store listings online. You may find it easier to just mount a copper plate of appropriate size.

#3 is correct. The sintered spheres allows water inside the grounding plate which increases surface area contact with water but in a lighting strike that water is going to flash boil.

I am going to skip #1 because the abyc regs don't really cover that situation. In fact the wording seems to assume the vessel will have an engine and a grounding connector and that has a connection to the water which may not be universally true.

[CharmCityBoater]

Originally Posted by Statistical

On #2 solid copper plate is recommended. The electrical conductivity of bronze is much lower than copper. The "C" in 4080C is for copper. Not sure dynaplate makes the 4080C anymore though. You can find references to it but I don't see any store listings online. You may find it easier to just mount a copper plate of appropriate size.

#3 is correct. The sintered spheres allows water inside the grounding plate which increases surface area contact with water but in a lighting strike that water is going to flash boil.

Where can I find copper bar stock for this application? I was thinking a 2' long x 6" wide x 1" thick would work. Drill two holes to through bolt it and connect Shrouds and mast.

Also, I keep hearing about the "flash boil" associated with using a dynaplate and lightning strike. Is that enough reason to avoid the Dynaplate all together? I still see mixed opinions on this.

[GordMay]

I recommend:
A solid [not sintered bronze] copper lightning grounding strip [exit terminal], with sharp, exposed corners, at least 3/16 inch (5 mm) thick, approximately one inch (25 mm) wide, and between 4 ft. (1.25 m) and 12 feet long (3.7 m); extending from a point directly below the lightning protection mast, toward the aft end of the boat;
ABYC says, "An equalization bus on the inside of the boat, paralleling the grounding strip on the outside of the boat, may be used as the lightning ground conductor." Secondary lightning conductors can be connected to this equalization bus.
ABYC encourages use of two bolts, at each end of the external grounding strip, extending between the external strip, and the internal equalization bus.

[CharmCityBoater]

Originally Posted by GordMay

I recommend:
A solid [not sintered bronze] copper lightning grounding strip [exit terminal], with sharp, exposed corners, at least 3/16 inch (5 mm) thick, approximately one inch (25 mm) wide, and between 4 ft. (1.25 m) and 12 feet long (3.7 m); extending from a point directly below the lightning protection mast, toward the aft end of the boat;
ABYC says, "An equalization bus on the inside of the boat, paralleling the grounding strip on the outside of the boat, may be used as the lightning ground conductor." Secondary lightning conductors can be connected to this equalization bus.
ABYC encourages use of two bolts, at each end of the external grounding strip, extending between the external strip, and the internal equalization bus.

Excellent feedback. Sounds pretty straight forward.

I have been thinking about the sintered bronze plate for RF. I was worried about a lightning strike causing the water in the sintered bronze to flash boil and explode, potentially causing a hole in the boat. As I thought about it the most sensible thing to do would be to create simple disconnects for the antennas / RF grounds when there is a storm present. Not only will this protect the HF / VHF equipment, but it will isolate the sintered bronze plate from becoming a path to ground. Make sense?

[GordMay]

Originally Posted by CharmCityBoater

... As I thought about it the most sensible thing to do would be to create simple disconnects for the antennas / RF grounds when there is a storm present. Not only will this protect the HF / VHF equipment, but it will isolate the sintered bronze plate from becoming a path to ground. Make sense?

Yes.

Originally Posted by GordMay

I recommend: ...

But, I’m just a, long retired, electrician, and lay student.

For the ‘gold standard’, in lightning protection information & advice , go to Dr. Ewen Thomson’s excellent website [1]. [there’s lots there]
From his research, as professor of Electrical Engineering at the University of Florida, and as president of Marine Lightning Protection Inc. [MLP], he is considered the world's leading expert on lightning strikes, its effects, and best protection methods, specifically with respect to sailboats.
[1] MLP ➥ About MLP

[dannc]

Professional Boat Builder issues 202 and 203 have articles on lightning protection that might be of interest.

There also have been CF discussions on lightning over the last few months, not to mention going back years.

Later,
Dan

[SY Harmony]

Originally Posted by CharmCityBoater

Where can I find copper bar stock for this application? I was thinking a 2' long x 6" wide x 1" thick would work. Drill two holes to through bolt it and connect Shrouds and mast.

Also, I keep hearing about the "flash boil" associated with using a dynaplate and lightning strike. Is that enough reason to avoid the Dynaplate all together? I still see mixed opinions on this.

https://www.onlinemetals.com/en/buy/...Width%3A2%2522

[Statistical]

Originally Posted by CharmCityBoater

Where can I find copper bar stock for this application? I was thinking a 2' long x 6" wide x 1" thick would work. Drill two holes to through bolt it and connect Shrouds and mast.

Online metals is one option. There are other similar companies which produce pure copper bars/plates of various sizes.

https://www.onlinemetals.com/

Also, I keep hearing about the "flash boil" associated with using a dynaplate and lightning strike. Is that enough reason to avoid the Dynaplate all together? I still see mixed opinions on this.

I think dynaplate is fine for an RF ground. Yes it could flash boil and shatter but if your RF ground is transfering lighting well most of your boat is toast anyways. This is why lightning ground and RF ground should not be connected.

[LifesBetterWhenYoureBeating]

Originally Posted by GordMay

I recommend:
A solid [not sintered bronze] copper lightning grounding strip [exit terminal], with sharp, exposed corners, at least 3/16 inch (5 mm) thick, approximately one inch (25 mm) wide, and between 4 ft. (1.25 m) and 12 feet long (3.7 m); extending from a point directly below the lightning protection mast, toward the aft end of the boat;
ABYC says, "An equalization bus on the inside of the boat, paralleling the grounding strip on the outside of the boat, may be used as the lightning ground conductor." Secondary lightning conductors can be connected to this equalization bus.
ABYC encourages use of two bolts, at each end of the external grounding strip, extending between the external strip, and the internal equalization bus.

Would two solid copper strips parallel to each other, connected to the mast via 2 separate wires work as well? Are the extra corners better in this case?

[GordMay]

Originally Posted by LifesBetterWhenYoureBeating

Would two solid copper strips parallel to each other, connected to the mast via 2 separate wires work as well? Are the extra corners better in this case?

Yes, multiple grounding electrodes [solid copper strips], distributed around the hull's perimeter, inter connected by loop conductors, and connected to the mast downconductor, will work [at least] as well.
I suspect that the extra sharp edges, of multiple strip electrodes, may improve the grounding connection.

See:
“The lightning system” ~ by Dr. Ewen Thomson, of Marine Lightning Protection Inc. [MLP]
➥ Marine Lightning Protection Inc.

And
NFPA 780: Standard for the Installation of Lightning Protection Systems
Chapter 8, Protection for Watercraft
➥ https://www.nfpa.org/codes-and-stand...evelopment/780

Superceded 2020 Version of NFPA 780 ➥ https://edufire.ir/storage/Library/o...20780-2020.pdf