Does My Boat Have Lightning Protection?
Lightning is as unpredictable as ever, and no boat builder can guarantee protection. There are some accepted best practices, though.
August 10, 2013
Question: In the photo I sent along you can see one of the wires attached to the chainplates on my new sailboat. The boat has one wire on the port side and another on the starboard side. I asked the sales people when I bought the boat if it had lightning protection and they said no. But, this wire makes me wonder.
The bend in this grounding wire should be straightened out to make a more direct path to ground in case of a lightning strike.
I traced it and it goes down to a junction in the bilge at the base of the mast and is ultimately connected to one of the keel bolts on my boat. It sure seems like part of a lightning protection system. What’s your take on this?
Answer: Some years back most boat builders began to shy away from even the mention of lightning protection systems on boats. Although I’ve never been told this directly, I am of the belief that the fear is one of presumed liability based on several tragic accidents, and the resulting lawsuits after lightning strikes (and in one case when a boat’s mast actually hit an overhead power line).
The ABYC actually took one of its standards, E-4, and changed it to what we call a “technical information report," designating it as TE-4. This was done in part because some manufacturers feared that if it was an official standard, it meant they were obliged to install a lightning protection system. That was never really true, but was assumed in some cases. Anyhow, suffice to say that builders are a bit gun-shy when it comes to lightning protection systems for liability reasons.
Lightning is fickle stuff, and in spite of people's best efforts at installing lightning protection systems, damage can still occur. ABYC TE-4 is based on historical observations and analysis of damage after the fact. Adherence to ABYC TE-4 comes with no guarantees that damage or personal injury will never occur.
So, with all that said, the wire you are showing us is part of a grounding system for you boat’s mast and standing rigging. ABYC TE-4 states that this wire should be no less than AWG 6 in size. The report also discourages sharp bends in the cable runs, which your photo shows. That upward slope is really not so good. Loosen the nut and straighten the cable out and slope it downward toward the keel for a more fair run to earth ground. One of the lessons learned by observation over the years is that lightning will sometimes jump out of any sharp bend in a conductor it is tracking along. In addition to this wire, the base of your mast, which we will assume is aluminum, should be connected via a minimum 4 AWG conductor to the keel bolt you mention. Finally, what TE-4 calls an “air terminal” or lightning rod should be installed at the top of your mast to complete the system. One source for the air terminals is Marine Lightning Protection.
If you do all of the things mentioned here, you will have a system that meets the basic criteria for a TE-4-compliant system.
