We’ve sailed surrounded by lightning several times. While impressive, especially at night, we have been very aware that we do not have any way for lightning to get out of the boat easily. After reading up on different solutions, this is what we built;
- A copper strip (150×6 cm) on the outside of the hull, as close as possible to the vertical line of the main mast
- A bronze thru hull post. This is what the copper strip is bolted onto.
- 25 mm2 tinned copper wiring from thru hull post to mast foot
- 16 mm2Â tinned copper wiring wiring from thru hull post to top and middle shrouds
Ideally, the grounding strip should have been made of bronze and twice as thick. Also, apart from the central bolt which connects the strip to the thru hull post, our solution to glue it to the hull, using Sikaflex 552, is a gamble.
Our always helpful local machine shop (panico.se) made a thru hull post for connecting the grounding wires inside the hull to the grounding strip on the outside. It’s basically a solid bronze rod with a flange on the outside and a M10 thread hole for bolting the grounding strip into it. On the inside is has an outside thread that takes a retaining nut from a thru hull and a 6mm hole for bolting the crimp cable shoes. In the picture, the cable from the mast has not been fitted yet.