Bonding

[Roger Long]

The general view now is to "take it around the outside and not bring it into the boat in the first place"

That would be good news for me. I could carry heavy wires connected to metal plates and attach them to the shrouds and stays with the plates just under water. There would be very little angle change from the shrouds to the wires. Complete electrical bonding probably wouldn't be required since lighting will jump quite a large air gap. Maybe welding cables with a couple feet of insulation removed where lashed to the stays would work.

I expect a lot of charge would still find its way down the big, straight, low resistance mast and then be looking for a place to go.

I certainly want to be anchored in any major electrical storm or at least with enough sea room to drift.

 

[gettinthere]

how big a wire would be needed to run from side stays to the water?

 

[Roger Long]

how big a wire would be needed to run from side stays to the water?

Probably as big as you can store, handle, and deploy reasonably. Stainless has fairly high resistance and the stays are small but you are trying to bleed off a field of charge, not just current flowing down the rig as in normal wires. Lighting likes to jump to large metal objects when it runs to the end of something so you would be trying to turn the portable wire grounds into those.

The one thing my boat has is an all round aluminum toe rail which many help to increase the "cage" effect if I can arrange grounds. I'm not going to throw out my old battery cable set until I've thought about this more.

 

[walt]

Four gauge is about the smallest you can go and not worry about a strong strike melting the wires. Surface effect is important so multiple wires is good.

The picture http://zenpole.com/pictures/electrode_feb2011_1.jpg shows an electrode on the end of a flexible four gauge wire with floatation that keeps the electrode right at the water surface (where the action is) at anchor, motoring or sailing. The floatation is special - it must withstand extremely high temps without vaporizing.

These are not on the market (might be someday?). FYI, this design is seriously covered by issued patents (including Dr. Thomson's) – but that is also why there is a picture of it on the internet.

 

[Bill Roosa]

I'd think that the normal size wire would work fine. I think ABYC upped the gage for lightning though but do not remember the number. 4 gage is my recolection but don't quote me.
I like the float idea, solves the sailing in the lightning and having the boat heeled over problem.
I believe this is a step in the right direction in that it keeps the lightning out of the cabin (who thought that was a good idea anyway???) however it does encourage the lightning to go down the back stay which is unfortunatly right over the helmsman's head. I'm thinking of an insulating soft mat that he can stand on to discourage his body from getting involved in the discharge to the maximum extent possible.

 

[Maine Sail]

I'd think that the normal size wire would work fine. I think ABYC upped the gage for lightning though but do not remember the number. 4 gage is my recolection but don't quote me.

you're spot on 4GA is for the main down conductor and secondary conductors are suggested to be min of 6GA. Of course the ABYC only publishes this as a TE or "technical information" and not a "standard". While it used to be a requirement it became clear that there are really no answers when it comes to lightning, and it strikes what it wants, when it wants to, so it became a TE as opposed to a standard.

I have done nothing different since the strike and do not plan to. The same night our boat was hit so was a teeny tiny Cal 22. It was one of the smallest boats and shortest mast in this 1200 boat mooring field yet it got hit even amongst significanlty taller masts and the boat had virtually no "electronic" on-board except for a VHF... My frind Kim's boat was also hit after they installed a bukoo buck lightning protection system with fuzzy mast head "dissipator". So much for that expense. It destroyed their carbon fiber spar despite having the 4GA down conductor and fuzzy "disipator"...

After our strike I spent a great deal of time, many days actually, talking to numerous individuals at Boat US Insurance and also Amica who also insures boats. The bottom line, after digging for a few days, was that there was no lightning protection system that stood out against any other as "superior". These companies have had every system hit on insured boats and none separated them selves from another in terms of loss mitigation. If they had you can bet that the ABYC and insurance industry would be all over it.

 

[Roger Long]

These companies have had every system hit on insured boats and none separated them selves from another in terms of loss mitigation. If they had you can bet that the ABYC and insurance industry would be all over it.

Sort of like dealing with tornado's with building codes. It may make a difference with the little ones but it's always going to be a crap shoot.

 

[Roger Long]

While pulling out my bonding system (wires black and crumbly with non W.T. terminals), I found a connection between the bonding system and the negative wire running back from the fuel pump. That probably accounts for the funny looking copper bottom paint patterns around my bronze through hulls.

 

[gettinthere]

If you want to run 4 ga wire off the stays for lightening protection...how do you attach the wires to the stays?

 

[woodster]

If you want to run 4 ga wire off the stays for lightening protection...how do you attach the wires to the stays?

i would think you would attach the wire to the fastening bolts on the chain plates.......

regards

woody

 

[Roger Long]

If you want to run 4 ga wire off the stays for lightening protection...how do you attach the wires to the stays?

Lightning isn't like electricity as we are used to thinking of it. The bolt that hits you may have traveled over a mile through air. If you just tied the cables alongside the stays, it would jump the 1/4" pretty easily.

 

[Bill Roosa]

The concept is to "suggest" to the lightning that the best, easiest path to that large capacitor plate (sea water surface) is via the wire you designed for the purpose. So anything you can do to connect to the water surface (not just the water at keel depth) will cause the whole system to see greater potential across it and be the more prefered path.

 

[Maine Sail]

This is how Sabre does it..

This is how Sabre does it. There were no sharp bends in this wire and they were careful in the routing and support of the wire to get a smooth transition as opposed to sharp bends. It went from the chain plate straight to a keel bolt, just as the mast base did.

To contrast Sabre's attention to detail this was a European builders idea of "bonding"...

 

[walt]

I believe the West Marine adviser linked earlier said to not bond to through holes (?) and this seems like a good idea and especially a good idea for any down conductor which might be discharging lightning.

There is one good reason to ground through holes and that would be if you had an AC fault and somehow applied VAC to the through holes creating a dangerous situation for a swimmer near the boat. If the through hole were bonded to ground, the AC fault would blow a fuse.

So maybe you simply want to avoid running any AC wires (or wires at all) near the through holes??

FYI, UL lists a minimum bend radius of 8 inches for lightning conductors
http://www.ul.com/global/documents/corporate/aboutul/publications/newsletters/electricalconnections/july09.pdf

 

[Forrest15112]

Lightning isn't like electricity as we are used to thinking of it. The bolt that hits you may have traveled over a mile through air. If you just tied the cables alongside the stays, it would jump the 1/4" pretty easily.

That's possible but it could just as likely make a jump to ground through your electrical system as the links that attach the stays to the mast probably aren't designed for routing large electrical surges. Ideally, stays would have ground jumpers clamped to the cable on each side of a turnbuckle or from the mast to the stay. The actual resistance between the mast and a stay would probably become significant during a direct strike to the mast.

 

[thinwater]

I'm not going to comment on lightening--it's all been said.

I am a licensed API petroleum tank inspector, and one of the things we inspect is grounding and galvanic corrosion. Generally, systems are ALL CORRECT or ALL WRONG. half-way attempts are where I find the worse damage, as that can create potential differences.

What I would do (and I have done this many times in tank farms--it works) is get a long pair of leads for you multimeter and check to see if all of the metals are at one potential, or if there are significant differences. It doesn't take long and will give you a good starting point regarding galvanic corrosion. If there is no existing damage on an older boat, I might leave well enough alone.

I have never seen significant galvanic corrosion (thousands of tanks) without <0.2V differential.

 

[Bill Roosa]

electricity and lightning

To say that lightning does not act like normal electricity is a pretty bold statement. I think that if you understood how the lightning got onto the boat and how it eventually got off the boat you would see that it does in fact behave exactly like "normal" electricity. What you don't know is WHERE the + and - poles are and all the internal resistances / insulators. About the only difference between lightning and normal electricity is the rather large difference in potential which allows lightning to jump gaps measured in miles and not fractions of an inch.
With all that said, I'd go with making sure the path you want lightning to travel is in fact the lowest resistance path from the mast head to the water surface.

I'd note that the empire state building has been getting hit by lightning multiple times a year for quite a few years now and the folks inside don't seem to be too concerned. Course they have a dedicated low resistance path to ground .........

 

[Roger Long]

To say that lightning does not act like normal electricity is a pretty bold statement.

As a scientific statement perhaps but not in terms of the practical issues we are discussing here. It's matter of scale. In everyday life, we deal with electricity that makes 90 degree turns and runs around coils. We don't see lightning's huge "inertia" that will make it jump off a conductor the turns too tightly.

Boats like Maine Sail's have everything fried when they weren't even struck directly. If the energy field of the flow can radiate that far out, almost no path it takes down your rigging or other controlled ground is going to insure against similar damage. He was telling me the other day about talking to a marina in Florida that has a lot of strikes due to their location. They have seen every proprietary protection system on the market wiped out at one time or another.

It's been said that the only predictable thing about sharks is that they are un-predictable. I was watching a TV show about lighting the other night which said much the same thing about it. Interesting new research has revealed that lighting bolt create large bursts of gamma rays and other radiation. Some after effects of strikes and close strikes on people, they now realize, are actually radiation poisoning. Future treatment may be improved by understanding this.

The one thing you probably can rely on is a Faraday's cage. The Empire State Building with it's massive and complete grounded steel frame and the complete shells of cars provide this effect. That dedicated low path resistance to ground needs to be a shell. The rigging of a sailboat sort of but the gaps are too large for it to be effective in protecting electronics. Ben Franklin style lighting protection keeps buildings from catching fire but doesn't protect computers and other modern electronics.

 

[Bill Roosa]

I'd agree but if you provide a "low resistance" (read low impedance because the capacitive and inductive parts are significant at those voltages) then lightning does act just like normal electricity. Normally we don't consider that when a 12 volt current travels around a sharp bend it does in fact get "resisted" by the inductive component because we are a) looking at a steady state (long time frames) and b) the induction at those low amps is very small. Wires don't normally have capacitances that we concern ourselves with either but if you are working with low voltage signals on long lines you had better consider capacitive attenuation if you want to have a strong clean signal at the other end.
It is really a matter of understanding electricity correctly and realizing that the various components are going to have different magnitudes in different situations. So while I don’t have to even consider the inductive or capacitive components in most boat wiring they are the major components that need to be addressed when considering lightning wiring.

 

[Roger Long]

they are the major components that need to be addressed when considering lightning wiring.

That's really exactly what I was trying to get at. A 10 GA green wire lead from the base of the mast, snaking up and around through a few lockers, and turning sharp corners to the 1 square foot ground plate required by ABYC may make some surveyors happy but is isn't going to do anything for you in a lightning strike.