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Old 24-08-2010, 18:23   #1
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No Keel Bolts - How to Ground for Lightning ?

I have internal ballast so no keel bolts on 1 boat and a tri so no keel on another. The tri has copper flashing lead down through the centerboard trunk. Im pretty comfortable with that. The mono is internal ballast. From all reports thes petersons have a mixed bag down there. Last haul I layed some heavy gauge copper sheet about 12x 18 a 1/8" against the hull flush with the gelcoat layer and bolted a ground dynaplate onto that. When I did this the product review said that the smaller version should not be used as a lightening ground the larger one I put on did not mention the limitation. THen I got paranoid. But nowhere can I find a good description or experience using and installing ground plates its very generic.THe smaller dynaplates have been known to explode as heat dissipation rapidly increases the size of molecules within the plate. The bolts that through bolt them are 1/4 inch can they melt. So my request is. What do you have?Have you been hit did it work.
My backstay is isolated and has a SSB tuner attached to the mid section the lower section is unbonded. Normally during thunderstorms all crew minus me hunker down in the back cabin way away from the mast. I cant quite get my thoughts and all I have read, the lack of real experiences and poor descriptions around this problem. again yep lightening is unpredictable. I have seen boats with holes blown clear through them from strikes while on land. One boat had charred glass at where the Jackstands must have been 6 square burn points 3 on either side. but no exerience with hits on the water. How would you set this up? Gord If you give me the ABYC link again I might side flash.
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Old 24-08-2010, 19:41   #2
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Great sabray...how am i supposed to sleep tonight?

According to radio manual I am studying, you need an 8 foot spike in the ground at each leg of a tower and they all need to be connected together in a triangle. Wow, so, on a boat....hmmm...a VERY LARGE grounding plate and connecting the mast to it as direct and short a lead as possible? Or how about multiple small ones? Else, get a steel hull.

You are looking for real testimonials - try searching on the forum. There have been a few people talking about their experiences with real strikes.

Did you also read this latest thread? There are some links and you might leave a question there too...

Question for All You Lightning Rods

I'm wondering about best practices too....
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Old 24-08-2010, 20:20   #3
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Some years ago on this site the question was asked if anyone had first, second, or even third hand knowledge of any size of those porous ground plates exploding do to lightning or anything else. Not one person came forward. Most of the damage to the hull occurs when the lightning punches a hole or holes thru the hull near the waterline. One example showed a large hole in the bow where the lightning jumped from the chain to the water.

I have no association of any kind with the ground plate company.

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Old 24-08-2010, 20:33   #4
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gee didnt even think about anchor chains.
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Old 24-08-2010, 20:37   #5
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Yes I have read most of the posts. I think although I asked Gord not to quote ABYC does not define very well the ground plate very little specifics like my ground plate has 5/8" bolt made of?. Or I have internal ballast and my mast is grounded by a plate x thick and wire size ? I asked a physics teacher about some of this and got a sorta blank stare and generic you should bond to whatever. There must be some better data somewhere. I have water tanks either side of the mast within 18" I originally thought they should not be attached to lightening ground now Im thinking they sould be. Yes I have read the peterson 44 links excellent except Im too dumb to get the down and dirty of right thing to do. steal boat sounds good.
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Old 24-08-2010, 20:59   #6
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Since you are only asking about the second half of lightning vs. vessels - the answer is rather simple. You want to provide the easiest low resistance path for a lightning strike to pass through the boat to ground/ocean.
- - To do this you need the equivalent of 4 sq ft of copper plate -minimum- mounted in the water. To this plate you attach a welding cable of at least 2/0 to your main mast with virtually no bends in the cable between the attachment to the plates and the attachment on the mast. The best attachment device for an aluminum mast is a pre-made bimetallic grounding lug which is available but difficult to find. It is a casting made with one half being aluminum and the other half bronze.
- - Lightning will connect with the highest thing near or on your vessel which with a sailboat is normally the main mast. Aluminum conducts electricity better than stainless steel so the energy will try to flow down the mast first. If you have a nice "fat" escape route via the welding cable and grounding plates the energy will complete its journey with probably minimal damage to your vessel.
- - However, if there is no "escape path" for the energy it will then (all of this occurs in nanoseconds) try going down the stainless steel shrouds where it will encounter that super skinny bonding wire system connecting everything metal together. In this case now your vessel is the inside portion of a surging electromagnetic field which will happily fry most of your electronics. And still trying to get through your boat to earth/water ground it can and has passed through your bronze through-hulls raising their temperature sufficient enough to melt the FRG and allow the through-hulls to fall out of the boat. Now you have 1.5 inch open holes allowing sea water to enter the boat. Although not in ABYC yet, bonding bronze through-hulls is generally not considered a good idea.On the other hand not bonding bronze through-hulls to a zinc can lead to tin leaching out and through-hull failure. (pick your poison).
- - The sintered bronze grounding plates (Dyna-plates, etc.) are, if you read the label carefully, listed as "equivalent" to "x" square feet of copper. Which they are when newly installed. But before long all those nooks and crannies fill up with sea life and there goes your "equivalent" sq. ft.
- - Wooden masts generally have a thick copper strap that runs down the length of the mast of give the energy of a lightning strike an easy path to ground versus splintering the wood.
- - However, all of the above is theoretical and looks good on paper and has "theoretically" worked on some vessel struck by lightning - it is not a guarantee or "sure-thing." Mother Nature does what Mother Nature wants to do and she does not read our physics books.
- - And secondly installing a proper grounding path system for a lightning strike is both expensive and time consuming and when you consider the probability of being hit is very, very low some folks and manufacturers all consider it not cost-effective. There are a lot of more probable high risk things that can sink a boat which will consume most of your money trying to prevent.
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Old 24-08-2010, 21:54   #7
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Osirissail,
Yes looking at only the second half. I think though that looking at that last phase also partialley addreses the first the atmospheric bond by grounding may negate the initial charges that put us in ground zero.
Im slow to grasp and you have a gift at explaining please continue with your explanation and correct me where you find fault.
I get the direct path my mast is hit. A huge surge of energy is trying to find ground.I think Im set up pretty well. except for the bolts going to the dynaplate. The mast is attached through a 3/8 " stainless bolt with lancote a nut that tightens against the copper 1/2" tubing that is tied to 1/4" copper bolts that hold in the dynapalte wich is a bedded against the copper heavy gauge bonding I added 12x 18". week spots are those 1/4" bolts and maybe I didn't get enough surface area even with the dynaplate. Really appreciate your well described feedback.
I leaned away from grounding the chainplates internally. In a peterson the chainplates being grounded would lead direct path under or over large water tanks. within a 1/4 inch this looked like a potential widespread dispersion. I think not sure the chain plates would be better grounded to the exterior by jumper cables or a strap on the hull going to seawater. My groundplate is probably not big enough and the 1/4" bolts that hold the dynaplate on would be molten. I need to get through this FRP without burning a hole. Sounds like a really big bolt of your special bimetallic. Why isn't this bette described anywhere and no ABYC doesn't do it unless I missed a chapter.
Thanks for the help
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Old 24-08-2010, 23:30   #8
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Quote:
Originally Posted by Viking Sailor View Post
Some years ago on this site the question was asked if anyone had first, second, or even third hand knowledge of any size of those porous ground plates exploding do to lightning or anything else. Not one person came forward. Most of the damage to the hull occurs when the lightning punches a hole or holes thru the hull near the waterline. One example showed a large hole in the bow where the lightning jumped from the chain to the water.

I have no association of any kind with the ground plate company.

I can provide one data point to dispel the exploding Dynaplate urban myth, along with the myth about C-F masts exploding:

As you can see in the image below: Melted stainless whip with vaporized coax connector; my boat took a direct hit two years ago. The mast, a carbon-fiber stick bonded at the base with #4AWG copper connected to a Dynaplate directly below, was not damaged other than what appears to be a weld mark on the stainless mast base where a lightning arc left its mark. The hull was not damaged at all anywhere. Most of the electronics were fried. At masthead the VHF antenna melted and partially vaporized, coax was blown off its connector (which somehow unscrewed itself in the process and was never found), Windex fragments were found on the deck, but the tricolor/anchor was not affected (fully functional including bulbs still working 2 years later). The melting point of 316 stainless steel is in the 1375-1400C range.

The boat was hauled and carefully surveyed for a full day inside and out, plus a full riggers inspection. No damage to carbon fiber mast. No damage to hull, no damage to Dynaplate.

Judging by the evidence I suspect the lightning side-flashed to metal objects and wires through the boat (we were not aboard) and came down the main mast, the stays, and arced to the engine block itself. It probably reached the water by multiple paths (prop, Dynaplate, and direct arc from the shrouds).

Altogether less than $8k damage including hauling and fees, and replacement parts. Most of the labor done by myself and all completed in 2 weeks in my spare time. (If I would have had a yard do it -- it probably would have taken at least $40k and 30 days).

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Old 25-08-2010, 00:28   #9
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So now Im back to square one....I was just told not to hook to Dyna plate yet you had no advers affects by doing it.

Trying to get a no bend large cable from mast to outside of hull and then to 4 SF of copper on the keel does not sound real inviting...I think I will lug to the closest Keel bolt and call it good.....Does lead conduct electricty?
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Old 25-08-2010, 00:50   #10
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I liked the mast to the keel bolt idea from your earlier post. I have been looking at this for a while now. I could be wrong but I dont like the idea of bringing the chainplates down to the keel as well. Given thats ABYC standard Ill go with it but in my case it worries me. In your case the backstay being tied seperataly to the dynaplate surprised me. You persuaded me with your post to dumb down and seek a laymens solution to my best options. What worries me most is I don't have the keel bolt to get my Mast tied into. Your bolts will conduct and the lead is a good ground. Great heat diisipation in your case. In my case will the surface be enough to cool everthing before it melts. Sailfast how were you connected to the dynaplate?
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Old 25-08-2010, 05:37   #11
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Sailfast how were you connected to the dynaplate?
#4AWG copper from mast base to dynaplate directly below, next to the centerboard trunk.

The dynaplate was implemented by the PO, but I'm not a fan of that product. In my prior two boats I implemented a lightning ground using the MOONRAKER Copper Earth Plate which is a better ground, and copper is more resistant to fouling from growth than bronze MOONRAKER Copper Earth Plate - products and systems for boat, yacht, RV, mobile home, caravan and remote powered sites, Gold Coast (near Southport), Queensland | Outback Marine
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Old 25-08-2010, 05:47   #12
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Does lead conduct electricty?
Yes -- quite well. Look at your lead-acid battery terminals.
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Old 25-08-2010, 06:11   #13
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I have never heard of Dynaplates or other brands of the same thing exploding. As to attaching to them they normally use more than one mounting bolt so you can attach your bonding/lightning cables to all of the mounting bolts versus only one.
- - Bonding to ground your lifelines, stanchions, chainplates, and any other conducting metallic part of the boat is required not primarily for lightning protection but for AC faults that might put voltage to these items which if you or anybody on board grabs them could be fatal or at least enough to straighten your curly hair. That situation is a very real threat given the usually poorly maintained electrical systems in both boats and marinas.
- - The vast majority of lightning is HF energy which is why the "welder's" cable is the best to use. It has many, many more strands than normal marine cable. HF energy travels on the surface of the conductor which is why we use the flat copper ribbon versus marine wire on our SSB grounds.
- - Some slightly more paranoid cruisers worried about lightning also use the "zinc fish" or a welding cable attached to a large piece of scrap metal and hang it over the side of the boat from a main shroud.
- - How to lower the "odds" that you will be hit by lightning in the first place is a whole other discussion and the techniques we are discussing of providing an easy large low resistance path to earth/water ground is of little use in the former.
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Old 25-08-2010, 06:17   #14
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Michael Kasten’s recommendations, based upon Ewen Thompson’s research & on industry standards:
Lightning Attenuation Onboard

Ewen Thompson's EXCELLENT Lightning Website seems to be “down”
www.marinelightning.com/
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Old 25-08-2010, 08:35   #15
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If i am reading this report of SailFastTri correctly, the lightning made an exit at other points as well as the dynaplate (engine etc), and still fried the electronics.

What's the benefit in a plate then?
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