[Dave_E]

Hi All,

I'm replacing a large seacock (galley) in May. It's totally built up with green corrosion and the lever won't budge. I noticed there is a bonding wire that goes to "nowhere". I see the rest of my through hulls are bonded to each other. They are all in good condition. What is the general rule concerning through hulls in a FG boat?

Dave

 

[eherlihy]

Some say bond all through hulls to help mitigate the impact of a lightning strike. Others say not to tie the through hulls to the bonding circuit, because it can lead to galvanic corrosion of the through hull by completing a circuit between all the metals on your vessel (and those vessels in the marina with you) through the bonding wire. I am in the latter camp, although my mast and rigging are tied to a bonding wire that runs to a keel bolt.

I do not believe that either case has been definitively made.

 

[Minnewaska]

Green corrosion could simply be oxidation and not galvanic corrosion. I don't have a scientific position on bonding thru hulls to prevent galvanic corrosion and have seen both. I have not seen clear evidence of either position.

Intuitively, one requires an anode and cathode in an electrolyte to have galvanic corrosion. When a thru hull is exposed to this problem, one would think it needs protection. When not, one would think it doesn't. Still, metals can simply oxidize.

 

[hellosailor]

Green should just be verdigris, a surface reaction to oxygen and moisture. If the metal under it was pinkish, instead of brassy yellow, that would be galvanic corrosion.

Searoosters (take that, fascist juvenile web censor!) are of course never "grounded" unless you wire them to a helix or rod in the ground. (And I'll bet "rod" gets past the censors!)

Bonding them all is a discussion similar to debating whether Ganesh or Thor is the more venerated among the Gods.

 

[capta]

Before you replace a perfectly good seacock, I'd check out some of the repair threads on them on here and other sites. The green is nothing necessarily bad. Many seacocks have a nut or T-handle opposite the valve handle, which, when loosened allow the tapered pin to move. It is highly unlikely the thru-hull is bad; I've seen silicone bronze thru-hulls around 100 years old and in great shape. They do require servicing and lapping from time to time though.

 

[RichH]

Through-hulls should be electrically connected to the 'bonding' system ....

Here's the latest thoughts on lightning protection from the 'guru' of boat lightning research (formerly from Florida State Univ - 'that' guru). Notice that this expert's opinion leans more towards dissipation of lightning from a boat AT the waterline (where most through hulls are located).... which is much different than 'the old standard recommendations' Marine Lightning Protection Inc.

 

[mitiempo]

Servicing tapered cone seacocks:

Servicing Tapered Cone Seacocks Photo Gallery by Compass Marine at pbase.com

 

[eherlihy]

Through-hulls should be electrically connected to the 'bonding' system ....

Here's the latest thoughts on lightning protection from the 'guru' of boat lightning research (formerly from Florida State Univ - 'that' guru). Notice that this expert's opinion leans more towards dissipation of lightning from a boat AT the waterline (where most through hulls are located).... which is much different than 'the old standard recommendations' Marine Lightning Protection Inc.

Good stuff there!

However, a single ground plate is inadequate to prevent sideflashes, necessitating multiple interconnected conductors. These cause a whole new set of problems:

• accelerated galvanic corrosion or loss of sacrificial zinc's;
• electrolytic erosion in marinas with ground currents leakage;
• many mounting bolts and hull penetrations, each one raising the risk of water seepage;
• additional drag since plates should have exposed edges.

Through-hull transducers, fittings, and all immersed metal, including outboard drives, also inadvertently act as lightning grounds. A typical scenario for an ungrounded smaller powerboat, such as a 20' fisherman, is for lightning to attach to the VHF antenna (vaporizing it), spark through the electronics panel (destroying all electronics), travel into the battery ground or control cables into the outboard solid state ignition (rendering it inoperable), and then spark into the water through the drive unit. Any transducer such as a knotmeter is also likely to be blown out, possibly leaving a hole where it was mounted. This scenario assumes that no crew member is unlucky enough to be bridging a gap along the way.
...

In summary, the major problem with charge dissipation into the water is how to provide the appropriate number and distribution of grounding conductors, to eliminate sideflashes, while minimizing the corrosive effects of multiple immersed conductors that are bonded together.

Reading on, it appears that the website proposes the installation of dedicated lightning dissipation electrodes;

Here is their "suitable design for [the installation of these on] a sailboat"

I don't have these, and I doubt that anyone here has them on their boat either.

As I said, I don't believe that there is a definitive, and let me add practical, answer...

 

[mitiempo]

As I said, I don't believe that there is a definitive, and let me add practical, answer...

There isn't or the insurance companies, who write checks in the multi millions of dollars, would require whatever solution that was effective be contingent on insurance coverage in lightning areas such as Florida.

 

[bill cartwright]

All of the grounding in the world wont save you from a direct lightning hit. Everything tied together will electronicly fry. My keels are fiberglass with lead encapsulated in glass. What I have done works for me, I have a 10 foot piece of 1/4" stainless steel chain that I clip on to the upper stay turnbuckle and the bitter end is dropped in the water. I put it out only when there is a bad lightning storm and I am there in the middle of it. The ocean is a big battery and it will drain any current picked up by static aloft as well. You can even put a small zink on it if you like. An when you are in your slip, you can tie a wire to your main bonding ground and bolt a large plate zink to it an let it hang over the side. You will discover you prop zinc will last 2 to 3 times longer. To get away from thru hull electrolsis is to install plastic thru hulls, do you trust the? No not really but they seem to work. You have them in depth finders and paddle wheel knot meters and they work for that. Red bronze was created in England back in the late 18th century for wooden boats and has good properties. Back to the age old question, Bond all or not bond? I also installed a 3.5KVA Isolation transformer on my power coming aboard thru a 30 amp power cord and get ZERO electrolis from shore cords, yea it was 1300 bucks but one haul out and replacing thru hulls cost much more. And I have two Flicka 20s and in process buying a BCC 28 in the weeks ahead. An Yes I will set up the BCC the same way as I did the Flickas. What is the price you are willing to pay for peace of mind so you can concertrate on sailing rather than counting how many times the bilge pump cycled in the last hour while you are away from civilization on the water. Take it as you will but these things work for me an I am sure there are more ways to skin the cat on this issue.