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Lightning protection and bonding

Started by stephandjaysail365, May 27, 2023, 11:44:51 AM

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Hey all,

We have a 1981 365 Ketch that we purchased 2 years ago. Currently we have the mast removed and during some of the electrical work I noticed that the bonding conductor was only 8AWG. In order to bring the boat up to code I noticed that there are a few requirements. I am referencing TE-04 in the ABYC standards.
  • Main conductor must be 4AWG - mast can be used as the main conductor to the "lightning grounding terminal".
  • Secondary conductors must be 6AWG. Surge arrestors can be used. Various requirements on bending radius and conductor location and bonding exist here as well

I have a few questions:

  • The standard requires that there is a 1 ft^2 3/16 thick terminal that contacts the water at all times. In regards to the construction of the the Pearson 365 ketch, is there such a thing already? I reviewed our manual and it has this image. It does not specify a "terminal." Is the ballast used as this "terminal"?
  • The exisiting bonding cables I have are a mess and I plan to run them all above the water line using 6AWG utilizing heat shrink crimp ring terminals rather than compression lugs. The standard did not discuss connection methodology other than resistance requirements which is fine. Do you all use compression lugs or crimp ring terminal with appropriate dielectric grease? 
  • In general have most of you used air terminals vs static dissipators? I know for utility lightning protection that is stationary, both are employed. Considering the movement of the boat and the assumption that the boat is properly grounded, the air terminal seems the better solution to me. 
  • It seems that aside from the small ground bus bar in the aft, the main connections are at the ballast near the mast. Are there any other ground bus bars? Does anyone have pictures of lightning protection upgrades they have done in the past that I could reference? I did see Petes 2015 post about the little fuse surge arrestor 3 terminal conenctions which has been helpful.

Thanks in advance.

Jay and Steph SV Venture
Steph & Jay
S/V Venture
1981 Pearson 365

Dale Tanski

Jay & Steph,
1) Ballast on a 365 is insulated from that surrounding water as the ballast, although lead, is encapsulated within the fiberglass hull.  You would have to install a through the hull bonding plate and terminate to there.

2) Bonding cable need not be electrically insulated at all as they are a "earth ground".  Heat shrink ring terminals are there for not necessary. Some thoughts are that in the event of a high amperage load such as a lightning strike, the insulation on bonding wire can actually catch on fire.

3) Dielectric grease is designed to be an insulator which is the last thing you would want within your bonding circuits.

4) Air terminals are designed to collect and direct a strike and static dissipaters are designed to dissipate the electrical differential potential hoping the strike will go somewhere else to land.   The hope is that if you take a strike it is directed down the spar and out with as little resistance as possible.

5) Remember there are three systems at play here.  Your boats electrical grounds are totally different than your bonding system.  Your 120 Vac shore power system has it own separate ground system which is not connected to your negative (ground) side of your 12 Vdc electrical system which is not connected to your bonding system which connects stanchions, metallic through hulls, standing rigging, mast etc. For lightning and electrolysis purposes you should be focused on only the bonding system.

Pearson 365 Cutter Ketch
1976 Hull #40
Buffalo, N.Y.