I would think that if you stuck a grounding rod in the ground where you park your boat, and fashion a ground strap to connect your mast (and maybe the cross beams) to the rod whilst the boat is parked, you would have some measure of protection. To be truly protected, all the metal bits on your boat should be grounded together, but that may not be practical. But nothing is certain when dealing with lightning.



Grounding your mast would make it a lightning rod - meaning it would bleed potential off, making it less attractive to lightning, and giving it a path if it is hit anyway (although that path will most likely not be completely followed). The common misconception being that lightning rods attrack lightning - that's not their purpose. The keel boats in the marina are mostly protected this way - if the boat is built nice the mast is ground-strapped to the keel or other grounding plate on the hull. The other metal bits are also tied to the ground with ground straps. The end result is a supposed "cone of protection" that fans out about 45 degrees from the mast tip.



With my luck, I'd go through all this, and the lightning would hit the tree next to my boat, which would then fall over on it and crush it.