"Bonding" Thru Hull Fittings

[Leo MacDonald]

Hi OJ,

"18" has to be a typo. On E.L. they are all 10 or 8 ga.

[Sea Hunt]

Below is a copy of pages 28-29 of the Cape Dory Yacht Manual found on this website. If I understand it correctly (this is unlikely ), the "bonding" wire is #18 copper. However the lightening ground wire is #8 stranded copper. The manual suggests that the Ty Weekenders and the CD 22 may NOT have a lightening ground system unless requested by the buyer at time of mfg.

3.17 BONDING SYSTEM

All thru hulls and seacocks below the waterline, including the stern tube, are connected to one another, to the engine block and to the external ground plate with a continuous loop of 18 copper wire. This is done to minimize the effects of electrolysis should one fitting become “hot” for any reason. Generally, a fiberglass hull is considered to be non-conducting and as such the chance of
stray electrical currents forming is minimal. (Bonding system is standard on all diesel equipped Cape Dorys.)

As more and more electrical equipment is added to a boat, it becomes increasingly important to BE ALERT TO THE THREAT OF ELECTROLYSIS. We recognize that there are various types of
instrumentation available to further monitor strong currents and any potential difference between ground and the thru hulls. These instruments can all be added to the supplied ground wire system. It
is highly recommended that a sacrificial zinc be installed on the shaft (see shafting section).

3.18 LIGHTNING GROUND SYSTEM

Your Cape Dory is equipped with a lightning ground system installed in accordance with the American Boating and Yacht Council (A.B.Y.C.) specifications. Every shroud and stay is connected
to an external ground plate by a #8 A.W.G. stranded copper wire. Other equipment requiring bonding include the engine, fuel tank, mast step and fuel fill cap. Within practical working restraints,
the wires are lead directly to the ground plate. (Note - Typhoon and CD-22 have optional lightning ground systems.)

While no one can predict how lightning will react when it hits a spar, we know from actual experience that this system offers added protection.

During a lightning storm refrain from touching any metal objects such as shrouds, mast, stanchions, pulpit, etc., as these may attract lightning.

Do not paint the external ground plate with bottom paint as this prevents the plate from grounding
out with the seawater.

Periodically inspect the connections in the bilge to see that they are tight and clean and free from corrosion.

What remains unclear to me is whether the below water seacocks, etc. are connected with #8 AWG stranded copper wire The seacocks are apparently connected with #18 copper wire for purposes of "bonding" and helping to prevent electrolysis. From what I have read, should lightening strike a sailboat with sufficient force it can literally blow out seacocks below the water line because the lightening's nature path is to the water and it gets there through the hull and the seacocks.

For someone who lives in "the lightening capital of the world", I find this topic very, very interesting and more than a little scary.

[Steve Laume]

No matter what the manual might say, for whatever reason, I am certain there are no CDs bonded with 18 GA wire. I would guess my solid copper bonding wire is 8 GA. It could be 10, which would make for a more easily explained typo. All metal, pulpit, stays, shrouds pedestal, seacocks and engine are interconnected and run to the grounding plate. This is approximately, coat hanger sized wire that is fairly inconspicuous. If you have any pictures of a CD seacock you should see it on one of the mounting bolts, Steve.

[Al Levesque]

Our CD33 has a grounding system of solid wire. I haven't measured but the size looks to be about #8. Pictures I have seen on this site also look like solid wire. I don't often see bare stranded wire. The reference to 18 must be a typo, perhaps where the 1 was intended to be #.

[marilou]

I believe, the wire connected to the thru hulls is a "continuos loop of solid #8 copper wire". It may appear "green", might be what Sea Hunt referenced above.

According to manual 'the shrouds, stay, engine, fuel tank, mast step, etc. are led to grounding plate, where permitted' with 8 ga. black stranded wire.

The above appears to be correct upon inspection, on Hull #1 CD 270.

[Leo MacDonald]

n/m