Most of the lightning protection systems I have put in place related to outside electrical plant and buildings--but the principles are the same as any lighning situation--so I can give you my take on it.
First--the strike itself.
In the Land of Oz and the Southern States of the USA a full-on lightning strike would vapourise half-inch thick copper conductors. I have seen lightning vapourise telephone multiconductor cables--all that remained was a pink stain in the surrounding soil.
So how come lightning protection works as well as it does?
Because the idea as I understand it is to prevent the air from becoming ionised and providing a conductive path from the cloud to earth. If the conductor is working properly, as the air becomes charged because of the difference in potential between the earth and the charged particles in the cloud, this charge is "bled off" by the lightning collector and passed to ground before it can build up enough potential to fuilly ionise a path down which a strike can come--so the air in the vicinity of the collector has less charge density than elsewhere--therefore a higher resistance path than other areas where the air is more strongly ionised.
The streamers one sees rising from trees etc are the precursors to a discharge which may be severe--or may not develop into a severe strike or even a strike of any kind. The streamers may be in themselves be sufficient to safely discharge the air--but one can not count on them to do so all of the time or even any of the time.
A severe strike can occur when a discharge begins and then several charged areas of sky all unload their energy into the established discharge path. This can do real damage.
Now--to the wire in the plastic conduit idea.
It would be better than no protection at all and may work--but I think this idea of the pvc tube is only a way of preventing the copper wire from corroding the mast
. Other than that it serves no protective purpose--and it would not matter if it got covered in salt
. I would not even use copper if the mast was alloy--the mast itself can be quite effective and all it needs is a half-inch thick aluminium rod--sharpened to a point---or perhaps crowned with aluminium wires fanned out and tig welded to the top of it.
The rod can be clamped to the mast or even pass through it. The earthing plate in the ocean can be a large aluminium plate, pivoting down or lowered through a centrecase on deck
, connected to the mast by flexible aluminium cables
If you have wooden masts you may elect to use copper--then it must be fastened to the mast via a length of heavy copper cable and any jonts should be silver brazed or fused copper. If silver brazed the joint must be kept dry and free of salt
otherwise severe corrosion
might take place. For a wooden mast I would go all copper--and for a catamaran
I would rig a copper-clad plywood
centreboard type discharge plate exactly under the mast and able to be lowered to a depth
of at least half a metre.
The only way you can protect expensive electrical and electronic equipment
from a magnetic pulse or strong inductive field is to have it mounted in a ferrous cabinet. This can be painted or even galvanised--but as there is no field inside a ferrous container your precious gear
will be safe--provided you disconnect any wires leading outside the cabinet before the storm hits.
By and large your lightning rod needs to extend a metre or so above the mast. As a rough rule
, the zone of protection extends within a right cone with base angles of sixty degrees and as high as the collector. On a ketch
you may need two of them.
The idea of not using the elecrical equipment earthing system is to prevent the equipment providing a shunt path for induced currents--and frying the circuits.
Lightning earths need to be separate and preferably directly beneath the masts if possible--but if not possible then two plates should be provided either side and below the chainplates, if you wish to continue sailing. I would suspend them like lee boards. In the case of an all copper system 1 or 2mm copper plate could be fastened on the outside of heavy plywood
and connected to the collector by straps soldered or better still--silver brazed to the sheet copper before it is fixed to the epoxy-saturated plywood. Do not paint
the copper, and use it only on the outside of the plywood, not both sides as in the catamaran single
In the case of aluminium plate--the same applies but aluminium strapping can be used, tig welded to the plates and bolted to the conductor.
The idea of dangling a chain overboard
or dropping a circular discharge plate over the side makes it impossible to keep sailing--and sometimes you need to get to heck into a safe anchorage if you can--or if you can not--then get well out into the deepest water you can reach. You need protection while thios is happening.
This is just something for you to comment on or think about. There are proprietary systems available--but they are not as cheap
as offcut marine
aluminium plate or copper water service
metal bashed flat and recycled.