bonding wire question

[TikiDoc]

A question for the pros.  I recently bought a 1977 22.2 that was (marginally) water-ready for approximately the first thirty minutes I owned it - until I accidently f*&@'d it up.  I am patching it back together for now, and anticipate a full rebuild in about a year.  My question has to do with a bonding wire.  I was under the impression this tied back to the ground, but this boat had the bonding wire attached to a bolt in the bildge that led through the transom, below the waterline, to what appears similar to an anode, except it was painted.  This thing fell apart when I tried to unscrew the single, central screw holding it on from the outside.  Is this typical practice for a trailer-kept boat, to have a water-based ground tied to the ground buss?

Thanks in advance,
Blake a.k.a. TikiDoc

P.S.:  porn to follow once I get shoot pics

[seabob4]

From Pascoe:

The bonding system, also green wire, has nothing to do with electrical systems. Underwater metals are simply wired together to equalize differences in potential of different kinds of metal. Nothing should ever be grounded to the bonding system. Unfortunately, some people don't understand this and use it to ground electrical equipment, occasionally with disastrous results.

Bonding Systems
Bonding simply means wiring all the boats underwater metals together. This is done because of the galvanism caused by the different metals. By wiring them together, the differing potentials are equalized. Bonding does not solve problems of galvanism or electrolysis, but it does spread the the flow of current around over more metal, so that 1/4 volt or so won't cause any damage. Whereas if that 1/4 volt were going to one small seacock, it would probably eat it up in a hurry. In other words, bonding lessens the effect of small amounts of current. On the other hand, it also spreads it around to all underwater metals so that higher currents end up damaging everything.

Bonding systems use wire and ordinary crimped ring terminals. After a while these get wet and corroded. Electricity doesn't flow very well through corroded metal, so your bonding system after a while stops working. To maintain it, simply cut off the old terminals and install new ones. Do you have wires attached to sea cocks with hose clamps? Forget it. This is putting stainless and copper together, which are galvanically incompatible and it won't work.

Now Pascoe doesn't state what these "disastrous results" may be, nor what may cause them.  Contrary to Pascoe's "advice", all the builders I know that incorporate bonding systems in their boats tie them into DC ground.  These builders wire their boats to ABYC standards, so obviously, there are 2 (or more) schools of thought regarding bonding systems.

The zinc you had on your hull is simply called a "hull zinc", we used them at Stamas and Proline.  Pascoe doesn't mention this is his writings.  While a trailered boat certainly doesn't need a bonding system, having one doesn't hurt, either...

[Capt. Bob]

Contrary to Pascoe's "advice", all the builders I know that incorporate bonding systems in their boats tie them into DC ground.  These builders wire their boats to ABYC standards, so obviously, there are 2 (or more) schools of thought regarding bonding systems.

Agreed.
Mine is wired into the DC ground. I bond the tank and the fuel fill. My sea cock is non-metallic. I keep the boat on a trailer.
Trailer draggers like myself are more concerned about static electrical buildup than slow rotting by stray electrical currents.
We have always promoted bonding through the ground system. Most (but certainly not all) of us do trailer so for us........

Better to rust than go boom.

Good luck.

[Fletch170]

Really interesting guys. I remember guys who owned big boats with towers, would also run large crounding cables from towers to the Keel. I was told this would lessen the damage to the boat if it was struck by lightning.

My Hydrasport has the same through hull anode, which I assumed to be a "ground" for the very reason Bob mentioned. I plan on grounding as much s*it to that thing as possible? Right? I wanted to ground the house and the fuel fill. The motor gets grounded through the harness, and untimately the house.

Thoughts?

[seabob4]

Typically, the hull zinc will have a 8 GA green running to a ground bus.  No need to run equipment grounds to the zinc, that 8 GA will take care of it for you...

[dburr]

Really interesting guys. I remember guys who owned big boats with towers, would also run large crounding cables from towers to the Keel. I was told this would lessen the damage to the boat if it was struck by lightning.

Thoughts?

A better way to look at it is the a good ground on the tower will eliminate the PD (potential differance) that static electricity will generate on an ungrounded object that will be the focal point of a lightening strike... With out a good ground the tower builds a charge until blamo.....

[GoneFission]

Welcome Tiki!  I would guess what you have on the transom is a grounding plate, like a Marinco Dyna-Plate.  They've been around a long time are often used to help with radio reception to form a ground plane for ocean-going small boats, especially boats with AM/SSB setups.  Loran C generally would not work in some areas without one as well.     It should NOT be painted - if it is, sand the paint off and hit it with a wire brush!   :twisted:   It will be connected to the boat grounds, like the fuel tank, etc.  It also provides some protection for lightning - but let's just say if your Aquasport is hit by lightning - you're generally screwed...     The grounding plate is made of porous bronze and also helps with galvanic corrosion, but not as much as zinc or magnesium.  Here's a link:

http://www.marinco.com/en/4006  

See ya on the water!