Author Topic: Lightning protection, easily done on P323 (maybe)  (Read 7499 times)

jwspeck

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Lightning protection, easily done on P323 (maybe)
« on: January 08, 2016, 02:55:56 PM »
Was reading this article: http://www.boatus.com/seaworthy/magazine/2016/january/lightning-protection-on-recreation-watercraft.asp?utm_source=SWMAG&utm_medium=email&utm_campaign=swmag_art1_0116

Since the P323 has an aluminum mast, is keel stepped, and has a lead hull it sounds like you could pretty easily bolt some copper or bronze strips to the keel since it's lead fille and put a lightning rod on top of the mast and you'd be done.

Too straightforward? Do the mast step bolts really go down in to the lead of the keel?

Thanks,
John Speck

Dolce_Vita

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Re: Lightning protection, easily done on P323 (maybe)
« Reply #1 on: January 08, 2016, 03:50:05 PM »
There is a layer of fiberglass over the lead, fully encapsulating it, but the lag bolts that hold down the mast step do penetrate all the way into the lead.

I believe it is important to keep those lag bolts sealed to prevent standing water at the base of the mast from migrating down between the keel and the hull and causing hull problems down the road.
@(^.^)@  Ed
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with rebuilt Atomic-4

Alma

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Re: Lightning protection, easily done on P323 (maybe)
« Reply #2 on: January 09, 2016, 09:26:59 PM »
I also read the article. It is well written and codifies some new science. I'm always concerned with the difficult electrical connection between the underwater grounding strips going through the hull to the mast in the bilge. Because of my hybrid epoxy/stainless mast step, I do not have a natural electrical continuity between the mast and the mast step for these ground plate connections. My mast sits on an Al plate inside the epoxy cup that is bolted to the custom made stainless step. There is no (direct) electrical continuity from my mast to the stainless steel step to insure there is no galvanic corrosion of my Al mast base. The stainless step would wreck the bottom of my Al mast in months.  There is of course a convoluted electrical connection because of the boat's stainless rigging's bonding, but that connection does not occur at the point of contact of my Al mast and Stainless mast-step. Corrosion at the mast base is nonexistant four years now. I have routed my green bonding wires from the chainplates and rails away from connection at the step directly to the mast because my mast step is isolated electrically from the bonding system (and everything else). The step also sits on an epoxy block raising it from any normal bilge water.

The mast's bonding wire connection is a fine-thread 3/8 stainless threaded rod (stud) tapped into the mast at the mast's thickest point adjacent to the sail track, in the bilge. A wingnut securing the bonding wiring to an Al boss (big Al chunk) contoured to match the mast on one side and flat to accept the bonding wire(s) on the other. This insures no broken off bolt heads in the bilge when corrosion attacks the threads on the stud. Should the stud get stuck to the mast it doesn't interfere with disconnecting the wing-nut for servicing the wiring terminals. The stud must come out to pull the mast so I keep the stud greased and service it annually. This Al "button" is mainly for corrosion protection of the mast (from copper bonding wire and terminals) and for the shore power ground-fault safety connection. In a perfect world we would have (several) robust Al bonding lugs welded to our masts.

Although our enclosed lead keel is satisfactory for a SSB counterpoise (ground) it is certainly not adequate to disperse the massive electrical currents associated with a lightning strike or side-flash. Our internal lead is also insulated enough to prevent the tiny currents required for the ionization "cone of protection" we so often hear about...

Boats with inadequate routes for electrical current to the sea have had damage that ranges from simply a fried VHF radio to sinkings resulting from hundreds of small holes where the current has blasted through natural voids in the hull laminate below the waterline.

Many years ago I was hit by a side-flash on my little cuddy cabin powerboat. My hair stuck-out right before the strike and BOOM. A huge blue arc jumped from my hand to the boat's motor keyswitch. It didn't hurt me or my boat but it was an eYe opener for me and I am now terrified of lightning. It is said that there is statistics that show once one is struck (maybe on golf course) one is much more likely to get a visit from a million volts again! So I have mulled-over ALMA's lightning protection for over a decade. It is new data that a ground plate should be as thick as the article states. Old-school protection schemes used copper ribbon bonded or fastened to the exterior of the hull or sintered copper radio ground plates. I never had faith in these old options. Many boats lost this ribbon to flotsam and corrosion.

I'd like to see someone in-lay these thick(er) long shaped grounding strips port and starboard adjacent to the keel with the bronze strips directly connected to the mast via bronze lag bolts and heavy copper conductors to lug attachments on the mast as discussed earlier (to prevent a point of continuity failure at the mast/step interface).

Another important thing is the route of the conductor from the base of the mast through the hull to the plates. This must be of a radius that does not encourage the current to jump away from the conductors. This radius is discussed ad-nasium on yachting chat rooms.

To do this right requires painstaking workmanship and expensive material.
You've got an Al mast, Cu conductor, Bronze ground plates and through hull lag bolts and likely stainless steel hardware clamping the conductors to the lugs on the mast. That is a corrosion cocktail in the salt air in our 323's bilge. A small savings could come from flattened copper tubing as the conductor from the plate lag bolt to the mast attachment...

Inlaying 3/4 inch thick grounding plates following the contour of the 323s hull to prevent the plates from peeling off from debris or creating drag would be optimal and tedious.

The mechanical and electrical connections of each component must be close to perfect to also conduct the miniscule voltages and currents to create the so-called "cone of protection" created by a good electrical continuity between the air-terminal at the masthead, down the mast to the sea.

Each connection must be thorough and modular so they can be disassembled, inspected, cleaned and serviced annually to be able to carry the tiny currents of the ionization for "cone of protection" and massively robust to safely carry the power of a direct hit safely to the sea...

Lets ignore the conflict with the AC bonding system for brevity!









« Last Edit: January 09, 2016, 09:40:21 PM by Alma »

Captain Bri

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Re: Lightning protection, easily done on P323 (maybe)
« Reply #3 on: February 06, 2016, 10:59:19 AM »
Not sure about the bolts but just in case you didn't see it there was lightning strike on Chance that you can find under General Discussion that describes one experience. 
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