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Old 09-06-2013, 11:01   #1
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2 Dyna Plates

Hello,

My mate is having his 51 foot taken out of the water next week.

We are going to help him get a new 7.5kw gen in the vessel while at the slipway !

Everything is DC on the vessel now. I thought it best to install a Dyna Plate since it is out of the water.

A few friends at the club house said he could put on a second Dyna Plate on the other side of the hull, and ground the frames of his solar panels to that as lightning protection (since she will be out of the water for easy install).

I had thought 1 large Dyna plate could take both the AC ground of the gen, and also connect the Solar panel frames to the same Dyna plate... All DC is grounding via the main engine.

I have read my way into a brain-freeze after all the hours spent trying to search info online about this.

Anyone care to reply in a vocabulary a simple sailor can understand ?

Alan
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Old 09-06-2013, 12:24   #2
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Re: 2 Dyna plates

How about the idea of the Dyna Plate exploding when used as a lightning ground. These things are made from sintered metal, which is little blobs of metal pressed together leaving lots of their surface exposed to the water. As the lightning bolt hits the water it heats everything up dramatically and the expanding water blows up. Aside from that, the make a great ground.
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Old 09-06-2013, 13:56   #3
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Re: 2 Dyna plates

Alan,

In simple terms any sailor can understand: DON'T DO IT!

For one thing, you're mixing apples and oranges....nay, grapefruits!

There are several different types of grounds on boats. Here's an excellent primer, written in easy language:
Grounding

Most boats don't need even one Dynaplate, much less "matched" Dynaplates.

DC ground is thru the engine/shaft/propeller.

Lightning ground is separate....many experts believe it isn't worth the bother....lightning is gonna do what it's gonna do, and there's NOTHING you can do about it.

RF grounds for radios are separate. Can be as simple as a 3" wide copper sheet to the nearest bronze thru-hull. Or, radials. Or....about 20 other things.

Galvanic grounding is still different. Many experts believe it's best NOT to tie everything together.

AC and DC grounds normally tied together in a boat.

Read Stan Honey and reflect.

Then, have a cool one at the Peninsula and take it from there :-)

Bill
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Old 11-06-2013, 08:42   #4
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Re: 2 Dyna plates

Bill nailed it.

And in case you need more reinforcement: DO NOT DO IT!!
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Old 11-06-2013, 10:13   #5
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Re: 2 Dyna plates

Quote:
Originally Posted by CharlieJ View Post
Bill nailed it.

And in case you need more reinforcement: DO NOT DO IT!!

+1 Yep! Bill did it. Can't cut closer to the chase than that entry.
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Old 11-06-2013, 10:25   #6
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Re: 2 Dyna plates

Even for radio grounding the increased conductivity to the water due to the sintered construction is a MYTH. While I is true that water creeps into the cavities, the resistance of the salt water in comparison to the copper is so much higher that it is only the OUTER surface that is an effective contact. Think of al the little water paths as electrical circuits but they are all shorted out but the proximity of copper where they meet the open water.

You would be better off with a plain copper plate that you can clean and even paint when using for a radio ground.

I agree with the other comments, it is no use for lightning protection and can only make galvanic problems worse.
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Old 11-06-2013, 10:33   #7
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Re: 2 Dyna plates

Quote:
Anyone care to reply in a vocabulary a simple sailor can understand ?
Do not bother , its not needed, there is no need to bond any AC or DC to seawater, there is definitely no need or use to connect DC ground to seawater

Quote:
AC and DC grounds normally tied together in a boat.
only in the US, other wise fit an ELCI and disconnect the AC ( protective earth, never AC ground, ) from the DC negative) , your systems will thank you

Dave
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Old 11-06-2013, 18:14   #8
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Hello gentlemen,

We have the RCD main on the AC (shore power and gen side). The gen set is grounded to itself, so I will gather that the sea water flowing from the seacock is the grounding connection there.

I have read the link that Bill gave... Thank You Bill !!! Vocabulary my wife could even understand :-)

Now knowing a Dyna plate will become an under water claymore if used as lightning protection. We will have to see what we have below the water line once on the slipway !

As the vessel is a motor cruiser, the hard top over the flybridge has 8 large solar panels (300w 1 meter x 2 meter each panel). That is a lot if real estate for lightning to find... Need to give that a path away from the vessel.

Thanks so much for the great info !!!

Alan
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Old 13-06-2013, 08:40   #9
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Re: 2 Dyna plates

Quote:
Originally Posted by Hkalan View Post
Hello gentlemen,

<SNIP>
As the vessel is a motor cruiser, the hard top over the flybridge has 8 large solar panels (300w 1 meter x 2 meter each panel). That is a lot if real estate for lightning to find... Need to give that a path away from the vessel.
<SNIP>
Alan
Concern about dissipating lightning damage by providing a "path away from the vessel" is a waste of time. A lightning strike within 50 feet that didn't even touch your boat will blow out most of your electrical equipment. There is no way you could provide enough conductivity to anything to dissipate a direct strike.

There is even the school of thought that by providing a ground path from your highest point you "could" be attracting the lightning to it which might have been ignored if it was insulated from the water.

A flat surface like a solar panel in itself is unattractive to lightning, nearly all the photos and videos you see it goes for a high POINT, hence the spiky lightning arrestors on barns.
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Old 13-06-2013, 08:56   #10
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Re: 2 Dyna plates

Hello,

I have been reading a lot on that the last 2 days... it appears that the stainless steel (1 inch diameter) mast is more prone to a strike then all the aluminium frames of the panels.

Thanks for the great reply !

Alan
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Old 13-06-2013, 09:51   #11
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Re: 2 Dyna plates

Alan,

Can't pass up this chance to AGREE 100% with Andina! We often disagree on silly things like interconnecting batteries.

But, on lightning grounds I completely agree. Waste of time. Some of the WORST damage to your onboard equipment comes from nearby but indirect strikes. The current comes in thru the ground, and does a real job on everything connected.

Sometimes, even direct strikes do less damage to the onboard electrical stuff. Luck of the draw :-)

You don't have to provide a "path to ground"....lightning will find it's own, and it won't follow just the path you've provided....it will follow ALL paths.

IMHO.

BTW, Alan....did you have that drink at the Peninsula yet?

Bill
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Old 13-06-2013, 09:57   #12
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Re: 2 Dyna plates

Hi Bill,

Wednesday was the Dragon Boat races here (Public Holiday). We went to the buffet there before going to Stanley for the big event, and had more then just one drink... good food, good friends, and very expensive cocktails to start the day !!! HaHaHa

Alan
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Old 14-06-2013, 10:25   #13
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Re: 2 Dyna plates

So am I understanding you folks (Andina, Bill, etc.) that you recommend not installing a lightning ground plate? This is an area that is so confusing. I understand that there is no protection from getting hit. Where I'm confused is that the general recommendation I've read from various sources and alleged experts is that although you cannot protect from getting hit, you can at least soften the blow by installing a lightning ground plate connected to the mast. This makes sense to me, but what is confusing is that it seems very few boats have one. I know of no commercially available lightning ground plates. No market for it? I've never actually seen a lightning ground plate on any of the boats in my or surrounding marinas, and I looked last winter through several boat yards on the Chesapeake. I specifically looked at boats that are of encapsulated ballast. So if that's the recommendation, why is no one doing it? Is there any evidence that a lightning ground plate will at least reduce damage to the hull in the event of a strike? That's my greatest fear. I'll work around poofed electronics/electricals. A holed hull presents an entirely greater immediate problem.
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Old 14-06-2013, 10:40   #14
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Re: 2 Dyna plates

I have a piece of 1/4"thick copper about 6"x 24" screwded into the encapsulated keel and bonded to the mast. I have seen lightning bolts all around us but have no clue if we are any more protected but we have not been hit yet. One thing about lightning protection for boats is, there is a lot of mumbo jumbo about what works and what does not.
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Old 14-06-2013, 11:09   #15
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Re: 2 Dyna Plates

Most of lightning damage does not come from a direct strike. Most of the damage is done by the electromagnetic energy wave from the high current flash to the actual target with very fast rise and fall times. Its like the strike is the primary winding of an air core transformer and any metal within range is the secondary winding of the transformer. If that metal is an electrical conductor connected to sensitive equipment, the sudden MAGNETIC wave creates high voltage which does the damage. The pules of energy at the indirect location has no destination or inclination to find ground, that is only the path for the main strike.

A Faraday Shield (enclosing your electronics in a metal conductive container) is perhaps the only solution. With this all the penetrating energy is intercepted by the shield and converted to heat without re-radiating to the inside. Many people carry metal cases to protect important electronics from an approaching lightning storm but they must be completely disconnected while inside the container.

So a "lightning ground" will not be adequate to dissipate a direct strike and even if it did, the radiated energy would still damage on-board electronics. It may or may not be a factor that you are providing a preferred path to ground like they used to do on barns or even if the preferred path makes you more of a target.

A boat adjacent to me got hit. Their aluminum mast was connected to their metal keel. It did no damage to the mast but set fire to all the cables INSIDE the mast. Try putting out a fire INSIDE an aluminum mast!

Yes it is common to see ground plates on boats to protect from lightning, in the olden days people wore garlic around their neck to protect from vampires.
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